GG Friction Antidote in GEAR AND CHAIN DRIVE APPLICATIONS

Gear and Chain Drives – What You Need to Know When Selecting Gear Oils

How does one know which lubricant is the best fit for a given application? Typically, it is as simple as searching through a maintenance manual and selecting a product from the QPL (qualified product list). Unfortunately, this solution may not always provide optimum lubrication for a given gear set, or maximum efficiency in managing lubricant inventory. While some original equipment manufacturers (OEMs) provide generic specifications that consider pertinent parameters, others give only a general specification that may not even consider operating temperatures. It is therefore important for the individuals responsible for selecting lubricants to possess a fundamental understanding of how to specify lubricants for gearing. In addition to understanding and being able to interpret the specifications given by equipment manufacturers, it is important to understand why, and be able to make changes when necessary.

When selecting lubricants for industrial gearing, numerous factors must be considered beyond simply selecting a product from the maintenance manual’s QPL, including product availability, operating conditions, the preferred lubricant brand and product consolidation efforts. Proper lubricant selection is a cornerstone of any excellent lubrication program. A good understanding of this allows the lubrication engineer to maximize machinery reliability under normal conditions, as well as use lubricant specification as a problem solver in abnormal conditions.

Selecting the Correct Industrial Gear Lubricant

If your application requires grease lubricated gears, it is important to select a high quality grease that will never harden and has the ability to slump and flow around the gears.

Of all the lubricated components out there, there are few more pervasive than gearboxes. From high-speed gearing in turbo machinery to slow-turning gear reducers, lubricant selection, application and condition have perhaps the single-largest effect on the reliability and longevity of gearboxes. It would be great if industrial gears ran in cool, clean and dry environments. However, conditions in gear-driven operations such as steel mills, manufacturing plants and other strenuous industrial applications are anything but cool, clean and dry. That’s why lubricant selection can be so challenging.
Selection Criteria

In order to choose the best lubricant for a gear set, there are certain factors to keep in mind when selecting industrial gear oil that will provide you optimum performance and profitability:
Viscosity – Often referred to as the most important property of a lubricating oil.
Additives – The additive package used in the lubricant will determine the lubricant’s general category and affects various key performance properties under operating conditions.
Base Oil Type – The type of base oil used should be determined by the operating conditions, gear type and other factors.

The Base Oil

High-quality mineral base oils perform well in most applications. In fact, mineral base oils typically have higher pressure-viscosity coefficients than common synthetics, allowing for greater film thickness at given operating viscosities. There are, however, situations where synthetic base oils are preferable. Many synthetic base stocks have greater inherent resistance to oxidation and thermal degradation making them preferable for applications with high operating temperatures and, in some cases, allowing for extended service intervals. Additionally, synthetics perform better in machines subjected to low ambient temperatures due to their high viscosity index and low pour points. The high viscosity index also makes synthetic products suitable for a wider range of ambient temperatures, eliminating the need for seasonal oil changes. Some synthetics may also offer greater lubricity which reduces friction in sliding contacts.
Selecting lubricants for industrial gearing is similar in most applications. There is no specific property or value to create a good specification. To identify the best choice for a given application, the right viscosity, base oil and type of lubricant must be selected and the appropriate performance properties evaluated.

In order to handle increased demands, today’s industrial gear oils must contain high-performance additive chemistry. The goal is to keep the lubricant thermally stable and robust enough to ensure that it lasts longer, protects better and performs more efficiently, while at the same time keeping the system clean and carrying away heat and contaminants. This is no easy task. Consider industrial gear oils that at one time were widely acceptable for a given application. Even if these oils meet minimum industry specifications, which can remain unchanged for up to 10 years, they may not be durable enough to protect your equipment.
Fluid Cleanliness

Smaller gearboxes must do the same amount of work as, or even more than, their larger predecessors. But spaces are smaller and tolerances are tighter. That translates to higher speeds and loads. The trend toward smaller reservoirs means the system must cycle the fluid more often with less time to dissipate heat, release foam, settle out contaminants and demulsify water.

Constant gear rolling and sliding produces friction and heat. The heavier operating loads common in today’s industrial settings increase metal-to-metal contact or boundary lubrication, producing even more heat and pressure. To meet longer drain intervals for environmental and cost reasons, the fluid stays in the system longer. Therefore, fluid cleanliness and performance retention becomes critical.

GG Friction Antidote is a unique antidote to fluid friction. Highly viscous lubricants generate heat from internal fluid friction and also may consume more power to turn the gears. The rate of oxidation in the fluid can increase, which decreases the fluid’s effectiveness and life. In addition, higher operating temperatures increase sludge and varnish formation, which can damage equipment by forming deposits that can block filters, oil passageways and valves. On the other hand, less viscous lubricants generate less heat, minimizing the chance of exceeding recommended operating temperatures or damaging equipment.
Lubricants play a critical role in removing contaminants such as dirt, water, wear particles and other foreign matter that can damage gears and bearings and impact efficient, smooth running of the gears. As the lubricant travels through the filter system, contaminants, which can originate outside the system or from wear inside, should be removed. Even other lubricating fluids that find their way into the system can cause contamination if they are incompatible, thereby reducing performance.

Because they don’t move easily through the filtration system, highly viscous lubricants can be difficult to filter. Pressure at the filter can increase and, if sufficiently high, will trigger a system bypass, allowing contaminant-laden lubricant to circumvent the filters. Equipment damage can follow. Worn gears and higher levels of iron in the lubricant are signs of an ineffective filtration system.
Less viscous lubricants can flow more easily through the filtration system. Contaminants are effectively removed, reducing the likelihood of gear and bearing damage, and increasing equipment life. Another benefit of GG Friction Antidote is that with a progressive lubricant health analysis, you’ll notice that the lubricant may need to be changed less frequently, resulting in less downtime and cost.
Fluid Durability

Industrial gear oils must be durable enough to withstand in-service conditions and to retain that performance over time. Although many fluids may meet the industry specification when new, they rapidly lose performance while in service. Industrial gear oils formulated for extended durability will keep gears operating properly and protect equipment investment by extending life, reducing downtime, maximizing productivity and lowering maintenance costs.
Industrial gears often operate under heavy loads and require extreme-pressure protection for gear components. Typical industrial gear oils do not always provide high extreme-pressure performance at low-viscosity greases. This challenges the notion that industrial gears performing in harsh environments must have highly viscous lubricants to be adequately protected.
Fluid Demulsibility

It would seem easy enough to keep a gearbox dry, but water can creep into the system, particularly the reservoir, in a variety of ways. Mist from water used in routine plant maintenance can enter the reservoir breather, forming condensation in the reservoir after hot-running equipment cools after shutdown. Or, water may enter in some other way. In any case, it can lead to corrosion and decrease performance.

It is vital for the gear oil to be formulated to quickly separate water at both the high and the low temperatures found in industrial gearboxes. The ability to rapidly drain water from the system helps extend the life of both the component and the oil.

Universal vs. Dedicated Fluids

There are two types of industrial gear lubricants. The first, so-called universal gear oils, are formulated so they may also be used in automotive gear applications. Universal fluids may contain components that are both unnecessary for and harmful to industrial gear performance. Or, they may not contain components that are necessary in industrial applications. For example, water separation is not necessary in automotive gear oil applications. However, water separation is critical in industrial gear oil applications; therefore, demulsibility additives must be incorporated.
The second type of gear oil lubricant is called a dedicated fluid. These fluids are tailored for industrial applications by carefully formulating the lubricant with additive components specifically designed for such applications.
Gear Lubricant Type and Correct Additive Selection

After selecting the viscosity grade, the basic type of lubricant must be chosen. While there are many variations, gear lubricants can generally be placed into three categories: R & O, antiscuff and compounded. The gear lubricant type that best fits a given application will be determined by the operating conditions. Because there are no standard guidelines to help make this determination, the selection is somewhat subjective. Many equipment manufacturers will specify a viscosity requirement and leave this decision to the end user. Others will choose to be conservative and specify EP lubricants for the applications. It is therefore important to understand the general conditions that affect this requirement.
Additives used to enhance extreme-pressure properties in gear oil can be prone to thermal instability, resulting in sludge formation. However, technology is available that provides the optimum balance of thermal stability for sludge-free gearboxes and also extreme-pressure protection for heavy-duty durability.
The combination prolongs gearbox life, maximizes efficiency and eliminates downtime. But most important, high extreme-pressure performance and cleanliness are maintained across a full spectrum of viscosity grades, down to ISO VG 68. Using a lower-viscosity grade can improve efficiency while maintaining durability for optimum performance. In industrial settings, equipment downtime significantly impacts the bottom line.
R & O Gear Lubricants

Rust and oxidation inhibited (R&O) gear lubricants do not contain antiscuff additives or lubricity agents. R&O gear oils generally perform well in the categories of chemical stability, demulsibility, corrosion prevention and foam suppression. These products were designed for use in gearing operating under relatively high speeds, low loads, and with uniform loading (no shock loading). These lubricants are the common choice for these applications where all surface contacts operate under hydrodynamic or elastohydrodynamic lubrication conditions. They do not perform well or prevent wear under boundary lubrication conditions.
Antiscuff (Extreme Pressure) Gear Lubricants

Antiscuff gear lubricants, commonly referred to as extreme pressure (EP) lubricants, have some performance capabilities that exceed those for R&O oils. In addition to the properties listed for R&O lubricants, antiscuff lubricants contain special additives that enhance their film strength or load-carrying ability. The most common EP additives are sulfur phosphorous, which are chemically active compounds that alter the chemistry of machine surfaces to prevent adhesive wear under boundary lubrication conditions. In less severe applications, antiwear additives may also be used to provide wear protection under boundary lubrication conditions. Machine conditions that generally require antiscuff gear lubricants include heavy loads, slow speeds and shock loading. In addition to sulfur phosphorous and zinc dialkyl dithiophosphate (ZDDP) antiwear additives, several common solid materials are considered antiscuff additives including molybdenum-disulfide (moly), graphite and borates. One benefit of these additives is they do not depend on temperature to become active, unlike sulfur phosphorous compounds which do not become active until a high surface temperature is achieved. Another potentially negative aspect of sulfur phosphorous EP additives is they can be corrosive to machine surfaces, especially at high temperatures. This type of additive may also be corrosive to yellow metals and should not be used in applications with components made of these materials, such as worm gears.
Compounded Gear Lubricants

Compounded gear lubricant is the third type of common lubricant. In general, a compounded lubricant is mixed with a synthetic fatty acid (sometimes referred to as fat) to increase its lubricity and film strength. The most common application for these gear lubricants is worm gear applications. Because of sliding contact and the negative effects of EP agents, compounded lubricants are generally the common choice for these applications. Compounded oils are also referred to as cylinder oils because these lubricants were originally formulated for steam cylinder applications.
Changes Impacting Gear Oil Lubricants

Harsher Environments

Even with regular lubricant maintenance, heat, higher loads and pressures, and contaminants such as water can compromise a gear system. Today’s gear-driven equipment, and the lubricants that protect and allow them to perform well over the long haul, must withstand increasingly harsh environments that also cause quick consumption of essential gear oil additives. This is partly due to the trend toward smaller machines and exposure to diverse applications and punishing operating conditions. In addition, maintenance and plant managers expect higher performance, less downtime and more productivity to decrease costs and improve profits.

Gearbox Size

Today’s gearboxes typically are smaller and made from newer, lighter-weight materials than before. But, these smaller, lighter pieces of equipment are pushed to produce more power and, at the same time, be more durable and reliable than before.
Downsizing gearboxes means less oil and additive to lubricate and protect gears. However, at the same time, equipment loads are increasing. That translates into higher temperatures and more rapid oxidation. Oxidation harms industrial gear oils because it can form sludge that can shorten both oil and gear life. The results are expensive downtime, repair or replacement costs.

Viscosity

Choosing an appropriate viscosity grade is usually as simple as finding the recommendation in a component’s maintenance manual. Unfortunately, the manual does not always exist or the machine operates outside the conditions for which the OEM’s recommendations were made. Therefore, it is important to understand the methods for viscosity selection and the factors that affect the requirement. The viscosity for a gear lubricant is primarily chosen to provide a desired film thickness between interacting surfaces at a given speed and load. Because it is difficult to determine the load for most viscosity selection methods, the load is assumed and the determining factor becomes speed.

One of the most common methods for determining viscosity is the ANSI (American National Standards Institute) and AGMA (American Gear Manufacturers Association) standard ANSI/AGMA 9005-E02. In this method, assumptions are made concerning the load, viscosity index and the pressure-viscosity coefficient of the lubricant. The chart in Figure 1 is applicable to spur, helical and beveled enclosed gear sets. Other charts exist for worm gears and open gearing. To use this method, the type of gear set, gear geometry, operating temperature and the speed of the slow speed gear must be determined. After calculating the pitch-line velocity of the slowest gear in the unit, the required viscosity grade can be read from the chart using the highest likely operating temperature of the unit. It is important to note that this method assumes the viscosity temperature relationship of the lubricant (viscosity index = 90). If the VI of the lubricant deviates from this value, additional tables for oils with VI = 120 and 160 are included, or a viscosity-temperature plot can be used to interpolate the appropriate ISO viscosity grade.

Although several common methods for gear lubricant viscosity grade selection are available, most should return similar values.
Viscosity selection for gearboxes is a careful balance between load, speed/reduction ratio, gear geometry and operating environment. Like most applications, a good place to start is with the original equipment manufacturer (OEM) recommendations. This information is commonly posted on the nameplate affixed to the outside of the gear casing.
In surveying this data, you’ll often see viscosity referenced not in terms of ISO grades, but rather the American Gear Manufacturers Association (AGMA) grade or occasionally in Saybolt Universal Seconds (SUS). The AGMA grade is a numeric rating that correlates directly with gear oil viscosity grades. For example, an AGMA 5 oil is equivalent to an ISO VG 220 oil, AGMA 6 to ISO VG 320, AGMA 7 to ISO VG 460, and so on. You also may see the letters S or EP appended to the AGMA grade. This refers to the need for a synthetic (S) oil or an oil formulated with extreme-pressure (EP) additives.
For older gearboxes, lubricant specifications are sometimes given in the older and now-defunct unit of SUS. For example, a gearbox manufacturer may state the need to use a “700-second oil”. To convert to the appropriate ISO viscosity grade, a good rule of thumb is to divide the SUS value by 4.6. Therefore, a 700-second oil becomes an ISO VG 150.

While you certainly shouldn’t be going against the OEM’s recommendations without good reason, extreme ambient operating conditions (e.g. very high or very low temperatures), shock loading or extreme duty cycles, or higher-than-normal load ratings may dictate that a change to the OEM’s recommendations is warranted. It’s always a good idea to consult with a lubrication engineer before selecting a viscosity grade other than the one recommended by the OEM.

Synthetic Gear Oils

Synthetic gear oils offer some very real advantages in some circumstances. For example, in extremely low temperatures, a synthetic gear oil will have a much lower viscosity than the equivalent grade of mineral oil. This can be an advantage during cold temperature start-up when channeling can cause temporary lubrication starvation, particularly in splash-lubricated gear drives. Likewise, at higher operating temperatures caused by high ambient temperatures or the process itself, synthetic gear oils will have a higher viscosity than the equivalent grade of mineral oil and will typically resist oxidative and thermal breakdown better than mineral oil. A rule of thumb is to use a mineral oil if the operating temperature is below 160 degrees Fahrenheit, but consider synthetics or premium mineral-based oils (such as Group III gear oils) if the operating temperature is likely to exceed 180 F. Of course, there are other reasons why a synthetic oil might be advisable, such as for extended oil drain or other operational reasons.

When using synthetic gear oils, pay close attention to the type of synthetic in use. Many synthetic gear oils are made from polyalphaolefin (PAO) base stocks, which are compatible with conventional mineral oils. However, the use of polyglycol gear oils which have excellent lubricity are increasingly in use, while helping to keep the gearbox clean of deposits due to their natural detergency and “clean-burning” tendency. In fact, some gear manufacturers are factory-filling their boxes with polyglycol-based oils. Polyglycols are incompatible with hydrocarbon basestocks (mineral or PAO synthetic), thus requiring extreme caution in helping to prevent accidental mixing and cross-contamination. When switching from a hydrocarbon oil to a polyglcol, perform a thorough cleaning and flushing to help prevent hydrocarbon residues from reacting with the polyglycol gear oil.

When switching from mineral to synthetic gear oil, it’s not uncommon to drop down one ISO grade. The reason is due to the fact that synthetic oils typically have higher viscosity indexes than mineral oils. As a result, when you compare the viscosity of, for instance, an ISO VG 680 mineral oil to that of a ISO VG 460 synthetic, they will have very similar viscosities at 160 F. Before applying this rule, it’s important to plot the viscosity-temperature profile of each oil and consider the anticipated operating temperature along with high and low ambient temperatures to insure you select the correct grade for the specific application.
In some circumstances, this can be true. Certain types of EP additives are designed to react with metal surfaces under elevated temperatures to protect them under boundary lubrication conditions. These types of additives are often referred to as “chemically active”, and at elevated temperatures (greater than 140 to 150 F), they can indeed start to react with yellow metals such as brass and bronze. For this reason, apply caution when selecting gear oils for worm drives; the ring gear is often a yellow metal alloy.

A good way to check and see if an oil is “chemically active” is to look at the specification sheet provided by the lubricant manufacturer. On the sheet, you will typically see a test referred to as “copper strip corrosion” (ASTM D130). This tests how chemically reactive an oil is to copper and copper-containing alloys. For gear oils, a 1a rating is typically a good indicator that the oil is chemically inert, while higher ratings (such as 1b or 2a) might indicate possible problems when used in certain gearing at elevated operating temperatures. Often, a lubricant manufacturer will specifically state “this oil should not be used in gearboxes containing yellow metals”; other times, the manufacturer will simply state that the oil is appropriate for “steel-on-steel” applications – the implication being that they should not be used in situations where the ring gear is brass or bronze.

For certain gear geometries, particularly worm drives, the dominant frictional force is sliding friction as opposed to rolling friction. Under these circumstances, the lubricant must help reduce the coefficient of sliding friction. To do this, special additives that historically have been comprised of fatty acids are used to help the surfaces slide relative to one another. Another name used to describe this type of oil is “steam cylinder oil” because the same effect is desired in lubricating steam cylinder walls. Compounded oils are not commonly used for steel-on-steel gears.

A gain in 10 percent reduction in energy consumption for switching from mineral oil to synthetic oil depends on several factors. For example, when applied to a spur gear, which will typically operate with 95 percent or higher efficiency, it’s hard to understand that there is sufficient frictional loss from the lubricant to justify this claim. Likewise, if the dominant frictional loss is not due to fluid friction but rather the process or some other mechanical factor, again it’s unlikely that you’ll see any difference. However, in some situations where there’s plenty of sliding friction and the lubricant is responsible for most of the energy loss, there are circumstances where a 5 to 10 percent drop in energy has been seen. As with everything, consider all factors (including a practical test) rather than simply accepting anecdotal evidence, no matter what the source.

Polishing Wear

The term polishing wear is typically used to describe interactions between two solids that remove material from the surface of at least one of the solids while at the same time producing a polished finish on the surface. The result is a surface that reflects light brightly like a mirror.
Polishing wear may also be generated as a result of a chemical-mechanical interaction between the surfaces. For instance, it is possible to find polishing wear when there is a high concentration of soot in an engine oil. Soot is formed during the combustion process and enters the crankcase with combustion gas blow-by. Soot has an original size of 0.01 to 0.05 microns but tends to agglomerate to form larger particles in the crankcase. An oil’s ability to disperse soot is critical to preventing soot-polishing wear caused by the effects of soot on the oil’s anti-wear additives.

In high-pressure hydraulic systems, the hydraulic oil tends to accumulate silt. This silt may lead to valve sticking and polishing wear.
Another example may be found in gearboxes where the oil carries debris from micropitting, which can be as small as 1 micron. These particles act as polishing agents. The polishing wear is often found on gear teeth with micropitting, both in areas between the micropits and in areas without micropitting.
Keep in mind that these chemical-mechanical interactions involve both chemical and mechanical elements. In this case, an additive (such as an extreme-pressure or anti-wear additive) or a protective film that covers a metal surface is removed by contact with the other rubbing surface. The protective layer is then reformed, consuming a thin layer of the metallic surfaces under interaction. GG Friction Antidote can prevent polishing wear.
Sulfur-phosphorus additives normally produce minor wear due to the chemical-mechanical interaction. In certain cases, the sulfur-phosphorus types can be too chemically reactive, resulting in polishing wear. This type of wear is undesirable because it reduces gear accuracy by wearing away the tooth profiles.
In some circumstances, the extreme-pressure additives can be detrimental to slow-speed gear applications (less than 10 feet per minute), causing high rates of wear known as polishing.

Service Classifications for Automotive Gear Oils

The American Petroleum Institute (API) service designations are based on the type of service in which components will be used. The designations are utilized by manufacturers to select lubricants for particular gear types and operating conditions. No attempt is made by the API classification system to classify gear oils by physical properties or test performance. It also recognizes that some lubricants are suitable for a wide range of operating conditions and may be recommended for more than one service designation.

Although API designations may be very useful when making general recommendations, manufacturer recommendations should always be consulted to ensure that the lubricant being considered is not prohibited by that manufacturer.
API-GL-1 designates the type of service characteristics of automobile spiral bevel and worm gear axles as well as some manually operated transmissions operating under such mild conditions of low unit pressures and sliding velocities in which straight mineral oil can be used satisfactorily. Oxidation and rust inhibitors, defoamers and pour-point depressants may be utilized to improve the characteristics of lubricants for this service. Frictional modifiers and extreme pressure (EP) agents are not used. This designation is recommended for use in some manual truck transmissions.

API-GL-2 refers to the type of service characteristics of automotive type worm gear axles operating beyond GL-1. It may contain anti-wear and very mild EP agents, and usually includes fatty additives for worm gears. This service designation is obsolete.
API-GL-3 describes the type of service characteristic of manual transmissions and spiral bevel axles operating under moderately severe conditions of speed and load beyond GL-2 but below GL-4. It may have mild EP agents but is not intended for hypoid gearing. This service designation is obsolete.
API-GL-4 relates to the type of service characteristics of gears, particularly hypoid gears operated under non-critical, moderate speed, shock load; high speed, low torque; and low speed, high torque conditions.
API-GL-5 designates the type of service characteristics of gears, particularly hypoid gears in passenger cars and other automotive equipment operated under high speed, shock load; high speed, low torque; and low speed, high torque conditions. This designation is still widely used for EP gear oils.
API-GL-6 is associated with oils that reduce gear scuffing in older high-performance cars. This service designation is obsolete.
API-MT-1 describes a high EP oil intended for some non-synchronized manual truck and bus transmissions.
Mack, Volvo and Caterpillar trucks (as well as others) have their own specifications that address some conditions beyond GL-5. These are Mack GO-J+ and Volvo 97310, although these numbers change every few years.

Example of the Cause for a Short Lived Gear Oil?
If your gearbox is not thoroughly flushed after the oil oxidized, sometimes a simple drain will leave more than 15 percent of the old oil behind, occluding to machine surfaces and becoming trapped within the casing. This also leaves behind a host of reactive chemicals (pro-oxidants) that rapidly deplete antioxidant additives, leaving the base oil unprotected.
When the gearbox is high-duty, which probably means high temperature and high wear metal production then the temperature and wear particles also accelerate the rate of oxidation, especially when sludge and other pro-oxidants are in the mix. In such instances you should consider doing a thorough flushing of the gearbox.

How to Flush Gearboxes and Bearing Housings
Gearboxes and bearing housings periodically need a thorough flushing rather than a simple drain and fill. Several signs point to this requirement, such as overheating of the sump, gross liquid or solid contamination, and development of a severe wear pattern. Material evidence in the form of sludge, rust, moisture, wear metals, gel or other viscous residue that is present at the beginning of the drain should confirm to the technician that a flush is in order. A thorough flush is also useful for removing construction and assembly contaminants from equipment sumps prior to commissioning.
With these factors in mind, what constitutes a thorough sump flush? Are there any particular problems that the operator should be careful to avoid? What equipment can or should be used for this purpose? Finally, what items should be included in a detailed flushing procedure?

Flushing
Flushing is a clean fluid circulation process designed to remove water, chemical contaminants, air and particulate matter (not fixed to surface) resulting from construction, normal ingression, internal generation or component wear.

Flushing can be useful in many different circumstances, such as the following:
For new or rebuilt machines to remove contamination resulting from manufacture, service or overhaul. The fluid system can be contaminated due to dirty assembling elements, corroded surfaces, water, oxidation products and incompatible elastomers such as seals, sealants and coatings. Also, during the assembly process, dirt is ingested and debris is generated due to threading, joining, welding, etc.
For in-service machinery after an oil change due to heavy fluid contamination, component failure, extremely degraded lubricant (oxidation), or if a system flushing has not been performed in the past three years.

For gearboxes and bearing housings that are not fitted with filtration, flushing is required to remove contamination and sediment. Water, rust, excessive wear debris, sludge, varnish or lacquer, and hard-to-open drain ports suggest system contamination and indicate the need for a thorough flush. Ten percent of the old contaminated or depleted lubricant may be enough to use up most of the additives of the new oil.

What Flushing Removes

Material attached to contact or noncontact surfaces that may be harmful to lubricants or critical working surfaces is generically called soil. Soil may be composed of material that is generated internally, such as varnish, carbon deposits, chemical residues, sludge and rust; or material that is generated externally, such as scale, welding slag, rust, machining swarf and metal debris.
Soils may be mechanically or chemically removed. Flushing is a type of high-pressure, high-flow fluid circulation used to generate physical movement of contaminants. As the pressures/flow is used for flushing, circulating clean fluid in the system cannot clean rust and scale from the piping, deburr machined elements or remove flux or weld slag.
Flushing Methods

A few levels of system flushing are practiced, depending on the machinery internal conditions and type of contaminants compromising the system.
Recirculation cleaning – The recirculation of clean fluid at a high velocity to achieve a turbulent flow helps remove contamination from the fluid system.
Power flushing – A variation of recirculation, where the oil level in the sump is reduced and a high-velocity fluid is applied to mechanically dislodge, lift and entrain particulate debris. Power flushing suspends and transports particles; absorbs air, chemical products and water from the system; and releases the contaminants to a filter.

Wand flushing – A wand attached to one of the cart hoses is used to discharge at high pressure (kicking up adherent debris). The flow is then reversed and the wand vacuums the sediments.
Solvent cleaning – The use of solvents to remove organic deposits that cannot be removed by recirculation. Solvent cleaning may incorporate the use of organic (hydrocarbon-based) halogenated, nonhalogenated and blends solvents (type A-1 cleaners such as kerosene, or A-2 cleaners such as naphtha and Stoddard solvent are common) to dissolve heavily crusted or layered carbon residues.
Organic solvents tend to be blends of aliphatic and aromatic hydrocarbons and dissolve soil as opposed to emulsifying soil. These materials may be warranted if evidence of heavy carbonaceous residue exists.
Chemical cleaning – The use of chemicals that can dissolve inorganic components. Chemical cleaning may incorporate the use of aqueous alkali or acid solutions to accomplish the desired result.
Regardless of the flushing compound/fluid selected, unless it is identical to the lubricant used following the flush, it is important that all of the flushing fluid be removed from the sump prior to final fill. Some petroleum solvents with a concentration of five percent can create an appreciable thinning effect on the lubricant viscosity.

Factors for Effective Flushing

Fluid Properties. Fluid solubility and hygroscopic characteristics influence removal efficiency of water, air and chemical contaminants. Most oil companies supply special flushing fluids (rust-inhibited oils with good solvency power) that demonstrate the following desirable properties:
• compatible with system components and lubricating fluid
• noncorrosive to machine components
• low viscosity (lower than the lubricating oil used in the system)
• high density to suspend particles
• low surface tension to eliminate air
• high solvency
• hygroscopicity (for water removal)
• nonflammable
• economical
• reclaimable

Fluid Turbulence. To remove particles, the flushing process depends on the lift forces, drag forces and the depth of the laminar sublayer in the stagnant fluid next to the conduit wall.
As seen in Figure 1, turbulence can have a significant influence on loosely attached solid debris lingering in crevices or in the sidewall perimeter low-flow area. Turbulence in the system shortens the time and improves the quality of the flushing activity.
To properly achieve particle removal, the fluid must be turbulent. The indexless Reynolds number measures turbulence. In general, a number greater than 4,000 represents turbulent flow, and a number less than 2,000 represents laminar flow. Hydraulic and circulation system designers strive to create laminar flow conditions. For gearbox and bearing housings fed with a central system, turbulence is necessary. For stand-alone housings, the effect of turbulence and the ability to direct the force of the fluid facilitates movement of soil.
There is some risk associated with the high-velocity flush. Circulation of a fluid at high velocity with particulate contaminants can damage sensitive components (pumps, heat exchangers and valves). Also, such high pressures and flow can affect system filters. It is necessary to bypass flow- or contaminant- sensitive components.

Filter housings can be left in place if filter elements are removed. Components that restrict the flow rate, and thereby increase the pressure drop, should be isolated from the flushing circuit and cleaned individually.
Flushing Equipment

The flushing equipment required depends on the size, location and installed devices on the machinery. A mobile filtration unit is helpful if the pumps are capable of providing a flow rate at least twice that normally used in the fluid system or the flow requirements for the proper Reynolds number. An air breather is required to prevent dirt ingression during flushing.
Use large duplex filters (Beta 3= 200 or higher) with differential pressure indicator to allow filter changing without interrupting flushing. If water removal is desired, include a filter with water-absorbing capabilities.

A heater should be required in case of low ambient temperature to maintain or reduce fluid viscosity and achieve the flow requirements. Permanently installed quick-connectors are beneficial for flushing or filtration if the connector and piping are large enough to facilitate flow. In some cases, a reservoir other than the machinery sump is needed to contain the high volume of fluid required for the appropriate flushing.
A sampling port should be included upstream of the filter to analyze the fluid to establish when system cleanliness is achieved. An in-line, flow decay-type particle counter is the best option. If particle counters are not available, the use of an optical filter patch can help to determine system cleanliness.
Flushing Procedure

The flushing procedure depends on the specifics of machinery, plant conditions and flushing equipment. To obtain the best results, follow these guidelines:
• Drain the used oil while hot, so the viscosity is low and contaminants remain suspended and can be drained within the oil.
• Inspect the drained oil and drain ports for contamination that may indicate the need for power flushing or wand flushing.
• If drain port is not located at the lower point, heavy solid particles, water and/or emulsions will stick to the bottom of the reservoir. Wand flush is required.
• Remove oil filters from system.
• Block or bypass sensitive components.
• Block or bypass components that can reduce fluid velocity.
• If necessary, divide the system in sections.
• Connect the flushing equipment to gear box or bearing housing.
• Install air breather.
• Circulate and heat the fluid if necessary to reduce viscosity and pressure drop.
• Flush at specified Reynolds number to achieve turbulent condition.
• Monitor the contamination level (in-line particle counter readings or sample fluid and optically inspect filter patch).
• Circulate fluid an additional 15 minutes after cleanliness level is achieved.
• Drain and blow the system with dry, filtered air.
• Remove flushing connectors.
• Empty and clean filter housings and install new filter elements.
• Refill the system with filtered specified lubricant.
• Circulate (filter) new oil at least seven times before operating the equipment. Use a filter cart in systems without filtration.
• Label and store flushing fluid.
• Analyze flushing fluid for suitability.

Flushing Cleanliness Targets

For gearboxes and bearings, the target cleanliness level for flushing should be at least one number below the cleanliness level for the operating fluid. A maximum of 16/14/12 (ISO 4406.99) is recommended for critical gearboxes and element bearings.
The flushing process may be perceived to be an expensive, complicated and time-consuming extra task for an oil change. However, some conditions justify the effort. Highly contaminated reservoirs on critical systems warrant additional attention to assure a high state of reliability.
Flushing is justified for new and rebuilt equipment prior to commissioning to sustain high levels of reliability. A proactive maintenance approach of deploying flushing for in-service bearings and gearboxes helps to increase lubricant life and equipment durability. Generally, the flushing efforts and costs are well compensated with increased reliability related to system cleanliness.

When to Perform an Oil Flush
Just as it should, oil analysis gives rise to many other questions concerning maintenance practices. One that often tops the list is what to do when a lubricant doesn’t get a clean bill of health. More specifically, what must be done with the machine that contained a degraded or contaminated lubricant after the drain? Is a flush required? If the answer is yes, there are a few other questions that follow, such as:
1. What was the root cause that led to a need to flush? Who is to blame?
2. How urgent is the need to flush? Can’t we wait?
3. What are the risks of not flushing? What is the worst that can happen?
4. Are there negative side effects to performing a flush? What dark cloud is hidden beneath the silver lining?
5. What is the best way to perform the flush to reduce cost, risks and business interruption?
To Flush or Not to Flush

While the broader, procedural subject of flushing goes well beyond the word-count limit of this page, let’s take a closer look at the fundamental question of when performing a flush is justified. When we understand the conditions that trigger the need for a flush, we are better equipped to answer the remaining questions on the list above.
Often the need to flush is first observed during an inspection or the appearance of sludge in a sight glass, on a used filter, or on the bottom of a sump. This can be confirmed by oil analysis and further inspection. Remediation involves both the removal of the sludge, varnishing or debris (flushing) plus the removal of the root cause before the system is returned to service with normal life expectancy.
Risky Business

What are the risks associated with a flush? These vary considerably and depend on the flushing procedure, the machine, and the lubricating oil. If the flush procedure involves introducing foreign chemistry (solvents, detergents, etc.) into the oil or machine, this could impair the performance of the lubricant and attack seals and machine surfaces. Lab testing in advance can hedge the risks. In certain cases, flushing can also lead to leakage when deposits are removed around aged seals and gaskets. In addition, problems can also come from the disturbance and resuspension of settled, low-lying contaminants that are not fully carried out of the system during the flush. In general, there are risks any time a machine is invaded by human agency.
Tactics for a Strategic Oil Flushing Program

Flushing Tactics. These are single discrete activities directed at removing unwanted deposits, sediment and risk-prone fluid suspensions.
Flushing Strategies. Strategies are a program of one or more tactics and related steps needed to achieve a complete and successful flush.
Let’s begin this tactical discussion by distinguishing between two closely related cleanup activities: oil reclamation and machine flushing. Unlike flushing, oil reclamation (also known as reconditioning) does not have to involve the machine and its surfaces. It is simply a process of removing health-threatening contaminants from the bulk oil. In certain cases, this may include acid scavenging. For large systems, it may be followed by bleed-and-feed or other top treatments to restore depleted additives and dilute soluble impurities.
As mentioned in the following list of tactics, the removal of harmful contaminants (both soluble and insoluble) from bulk oil can beneficially impact the removal of pre-existing sludge and varnish. It can also substantially mitigate the future formation of internal machine deposits. This has led to a blurred line between the definitions of oil reclamation and flushing. The confusion basically comes from these two cross-linked statements: (1) It can be safely stated that a machine’s internal environment free of deposits, sediment and sludge will by default result in extended oil life expectancy; (2) In a similar fashion, a bulk lubricant scrubbed free of soluble and insoluble impurities by oil reclamation will have a measurable impact on machine service life, cooling and friction. In certain instances, the reconditioned oil can even be an effective agent in removing of varnish-like deposits. This explains why many of the flushing tactics mentioned below are also classical technologies used for oil reclamation.

Choosing the wrong tactic can be not only wasteful, but also risky from the standpoint of potential system upsets and negative side-effects. Anytime you introduce unusual fluid chemistry, temperatures, pressures, flows and turbulence there can be adverse consequential effects to the machine, its seals and the lubricant. Now on to the tactics … the list below describes in limited detail, the practices and technologies used by at least 95 percent of flushing activities in industry.
Drawdown Filtration/Separation. This is the mildest of the flushing strategies. Because many machines have no onboard filtration, the use of periodic filter carts and oil reclamation equipment not only can clean the oil (drawing down the contaminant level) but can also remove loosely deposited sludge and sediment.
High Turbulence, High Fluid Velocity, Low Oil Viscosity. Flushing is improved by enhanced fluid dynamics near machine surface boundaries. The approach involves increasing fluid velocity (sometimes two to four times the normal flow rates) and/or reducing oil viscosity during the flush. Typically, a Reynolds number in the range of 4,000 to 6,000 is generally targeted. Use the search engine at www.noria.com to get information on Reynolds number.
High Flush-Oil Temperature. This strategy also reduces viscosity and increases turbulence, and in addition, it increases oil solvency to aid in the scrubbing of tenacious deposits. Target temperatures range from 175ºF to 195ºF.
Cycling Flush-Oil Temperature. Some practitioners have discovered that shocking the machine with large temperature shifts helps break loose crusty deposits during the flush. They use coolers and heaters to cycle the oil’s temperature repeatedly over a range greater than 100ºF.
Pulsating Oil Flow. Rapidly changing oil flow rates caused by pulsation have been found to help dislodge pesky contaminants from nooks and crannies.
Reverse Oil Flow. By changing fluid flow direction, some contaminants and surface deposits are exposed to bending fatigue reversals and can be dislodged and freed into the oil.

Wand Flush Tool. This tactic is used for wet sumps, gear boxes and reservoirs with convenient access to hatches and clean-out ports. A wand on the end of a flushing hose is used to create high-velocity oil flow to blast away deposits. Alternatively, the wand used in suction mode can be effective at picking up bottom sediment on the sump floor.
Charged Particle (Electrostatic) Separators. Some suppliers of these proprietary reclamation technologies have successfully removed varnish from machine surfaces as well as submicron soft contaminants in the oil, known to be a precursor to varnish and sludge.
Solvent/Detergent Flush. Various solvents and detergents have been used to concoct flush fluids with different degrees of success. These include mineral spirits (petroleum distillates), diesel fuel, motor oils and detergent/dispersant packages. They are typically added to the flush fluid at concentrations of 5 percent to 15 percent, followed by a rinse. Compatibility problems (with the oil, seals and machine surfaces) are the primary concern. Always consult machine and lubricant suppliers before these chemicals are introduced.

Chemical Cleaning. These are chemically active compounds, typically caustics and acids that aid in the removal of the most adherent organic and inorganic surface deposits. The oil must first be removed completely from the system. Following the flush, these chemicals should be thoroughly rinsed from the system, often followed by pacification. Always consult machine and lubricant suppliers before employing chemical flushes.
Mechanical Cleaning. This generally involves the use of scrapers, brushes, abrasives and sometimes an ultrasonic bath. Often, chemicals are also used as the machine components are washed one at a time using a parts-cleaning station.

Selecting the Best Strategies for a Successful Oil Flush

It stands to reason that selecting the wrong flushing tactic and strategy can be not only costly and time-consuming but potentially ineffective. Carelessly opening a machine and introducing foreign fluids may also present risk to the machine’s future reliability – more harm can be done than good. Because of such concerns, there are many cases where the flushing job may well exceed the practical limits of the on-site maintenance staff. This could be due to the complexity of the flushing procedure or the need for specialized auxiliary equipment. If your job is large and complex, it may be good advice to consult with professional flushing service providers before proceeding with a do-it-yourself plan. In such case, you may want to confirm that their approach to flushing will be tailored to your specific needs. Some flushing contractors perform the exact same type of flush for all clients and applications.
Original Oil – this is the old oil that was in use at the time the decision to perform the flush was made. In some cases, this oil may have already been drained from the machine.

Flush Fluid – this is a liquid that has been introduced to the machine after the drain of the original oil. This could be an oil, a solvent, a detergent, a caustic, blends etc. as described in the corresponding flushing tactics.
Rinse Fluid – as the name implies, the rinse fluid is used to rinse out the flush fluid, including suspended sludge and deposits that were successfully dislodged from the internal surfaces of the machine. In certain cases, more than one rinse may be required depending on the flush fluid and the rinse procedure. The rinse fluid in most cases is a lubricating oil of the exact or similar type (perhaps only lower in viscosity) as the new oil that will be reintroduced into the machine following the flush.
New Oil – after all proper inspections, the machine is ready to receive a charge of new replacement oil. Once done, oil analysis should be employed to confirm that no remnants of the flush or rinse fluids remain.
Flushing Strategies

The flushing strategies below are arranged in order of their inherent complexity, time to perform, risk to the machine and overall cost. It is sensible that the strategies further down this list should be avoided if possible. Note that the descriptions of these strategies are brief and generic. Information on more detailed procedures should be obtained from original equipment manufacturers, lubricant suppliers, etc. before proceeding.
Double Oil Change. When a machine’s internal surfaces are not yet exhibiting signs of distress despite the offensive presence of sludge or insolubles, the best strategy might simply be a double oil change. The first drain carries out a large portion of the contaminants and degraded oil. New oil is then introduced and circulated through a fine filter until operating temperature is reached and the oil is turned over a minimum of four times. It is then drained as well. A patch test, blotter, total insolubles or other suitable oil analysis of the second oil just prior to the drain will define the success of the procedure and perhaps the need to perform yet another sequence of the drain and fill.
Simple Power Flush. The power flush uses a portable filter cart or other high-velocity flushing rig. In some cases, a wand tool can be used to manually direct the flushing fluid in an effort to lift sediment and sludge from the sump bottom or break off deposits that have formed on internal machine walls. This can be performed without an oil change or prior to a single or double oil change. In large circulating oil systems, power flushing is usually performed in steps corresponding to specific zones within the system that must be cleaned. Blocking valves and hoses are often used to partition the targeted zones during the flush steps.

Advanced Power Flush. The advanced power flush is the same as the simple power flush with the addition of more aggressive deposit-removing tactics. The selection of one or more of these tactics is usually triggered by an inspection of the machine’s internal surfaces and/or a knowledge of the root cause that led to the need for flushing. Experience with flushing tactics corresponding to the flushing conditions may be the primary basis for the decision. In some cases, these tactics may be an attempt to achieve a successful flush without reverting to the more risky introduction of aggressive chemicals into the machine.
Chemical Power Flush. Using foreign chemicals such as solvents, detergents, caustics or acids should be considered flushing strategies of last resort. How these chemicals might disturb the machine’s reliable operation is always uncertain. For instance, such chemicals may dissolve internal coatings or surface treatments. They might attack elastomers used as seals or bladders. They might soften adhesives and binders used in the construction of filters. Remnants of these chemicals may clash with the oil (base oil and additives) that is returned to the system after the flush. And finally, they may adsorb into the grain boundaries of machine surfaces and later retard the performance of surface active additives such as rust inhibitors and antiwear agents.
Still, there are times when the chemical power flush is the only viable solution – the lesser of the potential evils. In such cases, laboratory testing in advance and seeking sage advice from professionals in the field are highly recommended.

Mechanical Cleaning. One could say that mechanical cleaning is not really a flush. This is because in most cases the machine must be fully or partially disassembled to gain access to surfaces to be cleaned. As such, there is no application of a flush fluid to the machine during the procedure. Often the deposits that require mechanical cleaning have formed in localized regions of the machine where they present operational risk. An example might be enamel-like deposits on the spool and bore of a servo valve that is restricting actuation. On a larger scale, diesel engines, compressors and gearboxes are often torn down for mechanical cleaning, typically involving the use of scrapers, brushes and solvents.
Besides experience, an important part of defining the correct strategy and tactics therein comes from the inspection of the machine. This inspection should be repeated before a machine is returned to service to verify that a successful flush has been achieved. Likewise, a final oil sample should be taken and analyzed to confirm that residual flushing fluids or loosened deposits that could potentially compromise lubrication and system operation don’t remain in the new oil.
The Voice within Your Oil in Guiding the Flushing Process
This voice, also known by practitioners as oil analysis, can provide essential information relating to flush avoidance, when to flush, how to flush and when your flush has been successfully executed. This guiding role of oil analysis will be discussed in three phases.

Phase 1 – Before the Flush

In relation to flushing, it is logical that the most important time to perform oil analysis is well in advance of a present flush requirement. However, this is not just to tell you when an impending need is detected – that would be too obvious. Instead, its real value is to proactively stabilize the internal-state conditions that avoid the need to perform the flush all together. In fact, a well-structured oil analysis program should largely focus on proactive maintenance objectives, such as avoiding the future need for a flush. This is due to the fact that nearly all flushes are performed after the following scenarios:
1. Needed maintenance was not performed (for example, an oil change)
2. Maintenance was wrongly performed (for example, a wrong or incompatible oil was introduced)
3. The machine was invaded by a foreign contaminant (for example, glycol, soot, etc.)
A well-designed oil analysis program should enable these common problems to be detected often before a flush is required. When successful, nothing more than an oil change may be required. Of course, the effectiveness in catching common flush precursors depends on oil samples being taken at the optimum frequency and the proper use of on-site or laboratory screening tests. In the event the condition was not detected on time, oil analysis would still be able to provide both the alert and degree of severity (urgency) of the flush condition.

Phase 2 – During the Flush

As described earlier, many flush strategies involve the use of a program of flush tactics until the original offending contaminant has been scoured from the machine as well as both the flush and rinse fluids. The flush and rinse fluids often contain fluid chemistry that must be thoroughly removed before the lubricant is replaced and the machine is returned to service.
Oil analysis can be used as often as needed to assess what remains in the circulating fluids. In such case, the analyses can aid in guiding the process by defining the type and duration of each step in the sequence. Perhaps certain flush steps (tactics) will need to be repeated based on the results of the analysis. This enables flushing decisions to be made or modified in real time in response to oil analysis data. In addition to laboratory testing of oil samples, various inspections of the machines’ internal surfaces, including gearing, bearings and tanks can help confirm the successful execution of the flush program.

Phase 3 – After the Flush

There are unique and often serious problems that can be an unpleasant side effect of machine flushing. However, evidence of these may not occur immediately. Flushing disturbs a machine in many ways that can’t always be predicted or easily observed. As such, for a period of time after a flush, oil analysis should be performed regularly on critical machinery to ensure that healthy conditions have indeed been restored. Early detection of a problem could be the difference between costly downtime and a nuisance condition that could have been easily corrected. The following is a list of potential problems (side effects) associated with flushing where oil analysis might provide a timely alert:
• Demulsibility – remnants from flush fluids can interfere with this important property.
• Oxidation stability – disturbed sludge and machine deposits may adversely affect this property.
• Viscosity excursion – many flushing and rinse fluids are very low in viscosity compared to the lubricant. When these fluids mix with the lubricant, viscosity can be cut back as much as 50 percent.
• Film strength and rust inhibitor problems – flush and rinse fluids may absorb into machine surface grain boundaries. These absorbed chemicals may interfere with the performance of important surface-active lubricant additives.
• Leakage and seal problems – when new chemistry is added to a machine and/or violent flushing occurs, seal performance may be affected. This may also be due to changes in lubricant viscosity or interfacial intension from fluid mixing problems.
• Oil way and filter plugging – flushing and rinse fluids can resuspend sludge and insoluble contaminants which can cause flow blockage of glands, orifices, oil ways and even filters.
In conclusion, the voice in your oil is an opportunity for those who perform or are considering performing a system flush. It would be rare for a machine to have a flush requirement without both the causes and effects appearing in the oil data well in advance, but only when samples are taken and the right tests are performed. This is just one more reason why learning the language of oil analysis is a valuable, enabling skill in the field of machine reliability.

Machinery Failure Analysis and Troubleshooting:

Under proper alignment conditions and good lubrication, gear couplings can perform satisfactorily for many years. When those conditions become unfavorable, there are distress signals and forces that will adversely influence the coupled equipment before an actual coupling failure occurs. These distress signals may be subtle, but will nevertheless cause expensive downtime. Specifically there are axial forces generated by an increase in the coefficient of sliding friction and by bending moments which become excessive because of misalignment that is always present in even the most carefully assembled machinery train.

How to Achieve Gear Coupling Reliability 

Gear couplings are among the most commonly used methods for connecting process equipment. When properly selected, installed and maintained, they can provide long life and good reliability. Gear couplings offer several advantages over other couplings, including moderate misalignment capacity, exceptional torsional stiffness and very high torque density.

However, when it comes to gear coupling reliability, there are many areas where failures may be initiated. Often these failures begin because of a lack of knowledge or a lack of execution of certain fundamentals, which are necessary for these couplings to run reliably.

Design, Selection and Sizing

Selecting the correct coupling for the application is critical for gear coupling reliability. Use the following steps to help make the selection process easier:

1. Choose the coupling style and design (Fast’s, Series H or Waldron; flex and rigid halves; close coupled or floating shaft; gear teeth specifications and misalignment requirements).
2. Select the service factor (SF) from the original equipment manufacturer’s (OEM) gear coupling charts. Shock loads or variable loading can cause premature failure if adequate SF is not used. Typical service factors are in the 1.5 to 2.0 range. Some manufacturers may even specify a misalignment factor for gear coupling sizing when higher coupling misalignment is expected.
3. Calculate application torque (T) requirements based on design brake horsepower (BHP), SF and speed.

4. Choose a coupling with a torque capacity greater than the torque requirements. Since the service factor is already factored in, there is no reason to add                   additional capacity.
5. Confirm that the coupling selected has a bore capacity greater than the actual application bore (shaft size). Frequently the maximum bore size will drive the           coupling sizing process and even increase the coupling torque capacity two to three times what was previously calculated.
6. Verify the shaft depth available for the coupling hub and compare to the actual hub depth. If the hub is too long, it must be either overhung or machined                 off. Since the hub to shaft engagement is the same in either method, it is preferred to have the hub machined off due to torsional effects of the overhung                 hub. If the hub is overhung or cut off, further examination may be necessary to determine if there is enough torque transmission capacity available. The                 rule of thumb is a 1-to-1 ratio for the hub length to the bore.
7. Check a dynamic balance chart to see if the coupling needs to be balanced. High-speed gear couplings may require balancing.
8. Ensure the coupling will fit around the equipment and guarding. This is typically something that can become an issue when there is a design modification             on existing equipment. Guards that allow maintainability will encourage proper maintenance in the long run.

Installation

Some couplings don’t get much of a chance at a decent life due to their installation. Just like other components that experience infant mortality, often times these parts don’t die but are murdered. Certain elements of gear coupling installation must be considered if optimum reliability is to be obtained, including:

• Hub and Sleeve Fits – Determine the type of hub fit (clearance, locational or interference). Higher speed applications should have an adequate interference fit to offset centrifugal force effects on shaft/hub contact pressures. Excessive hub interference fits can lead to hub cracks and hub failure.
• Keys and Keyway Fits – Keyways should have a proper radius to reduce the risk for fatigue cracking. Key lengths should be measured to minimize the coupling imbalance.
• Hub Bore – Ensure the hub bore is concentric to minimize hub runout.
• Hub Installation – Choose proper heating methods so hub material properties are not compromised and select the proper heating magnitude for interference fit hubs so the hub slides easily on the shaft. Never use a hammer to install or remove hubs, as this can cause bearing damage.
• Correct Coupling Gaps – If floating shafts have a small coupling gap, the shafts may impact one another under misalignment as the shaft oscillates during operation.
• Proper Sealing – Always use proper gaskets and O-rings so the lubricant stays in the coupling.
• Alignment – Install the coupling so misalignment stays within manufacturer limits with respect to offset, angular and axial misalignment.
• Fastener Assembly – Choose the correct type of fasteners (fine or coarse, length, exposed, shrouded, etc.) and the proper arrangement. While standard bolts can work, they may put the threads in the shear plane. Coupling bolts need the correct preload, which is accomplished by proper bolt torque methods.
• Lubrication – Get the right product in the right amount at the right time for optimum gear coupling reliability.

Different coupling styles have different lube and bore capacities. (Ref. Kopflex)

Lubrication

Perhaps the most important operating factor for a gear coupling to be reliable is lubrication. Selection of the proper lubricant is the first step. Many coupling manufacturers supply their own lubricants for their couplings. Gear couplings may either be grease- or oil-lubricated depending on the design. Oil-lubricated couplings will not dry out like grease couplings, while Fast-style couplings have smaller bore capacities.

It is fair to say that most gear couplings are grease-lubricated. Coupling greases have special properties, so general-purpose greases should never be used in gear coupling applications. Gear couplings can be subjected to very high centrifugal forces, and oil separation is a critical element of coupling greases. Since greases are comprised of oil and mostly a thickener, special considerations must be made regarding the selection and application of coupling greases.

Soap thickeners typically are heavier than the oils, so centrifugal forces tend to deposit the thickener at the gear teeth. Generally, a grease with a high oil content of high-viscosity oil and a grade 1 rating from the National Lubricating Grease Institute (NLGI) is preferred. A higher consistency grease may be considered for high-speed applications but should be avoided at low-speed applications.

Grease specifications may include speed limits or certain tests such as the K36 separation factor. Any grease will have oil separation based on time, temperature and centrifugal force. The K36 factor determines the maximum oil separation of the grease while running at 36,000 Gs. A K36 factor of 8/24 means the oil separation was 8 percent in 24 hours. In comparison, a grease with a K36 factor of 3/24 would mean that it did not separate as much as the grease with a K36 factor of 8/24.

Higher oil separation is desirable at lower speeds (lower G forces), while lower oil separation is preferred at higher speeds and higher temperatures. High-vibration equipment can also enhance oil separation and induce failures. Studies have even shown that gear coupling wear rates decrease as coupling speeds increase.

The main function of a lubricant in a gear coupling is to reduce the friction between the gear teeth as they slide against each other. The relative motion between the mating gear teeth occurs in the axial direction due to slight shaft misalignment. This motion is oscillatory, low amplitude, relatively high frequency and a function of the magnitude of angular misalignment.

This sliding axial motion between the gear teeth can generate lots of wear if lubrication is not sufficient. This is why the gear coupling lubricant plays such a critical role in the reliability and life of a gear coupling. Poor lubrication between the gear teeth generates higher friction between these teeth, resulting in gear coupling wear, heat generation and high axial loads to mating equipment bearings. The higher axial loads on the bearings will then decrease the life of the equipment.

The pump shown on the left had a dry coupling that was operating in a torque-lock condition and creating high axial forces on the equipment. The coupling was replaced without making any adjustments to the pump or motor. The only change was a coupling with good lubrication, which reduced tooth friction and decreased the axial forces from the coupling to the pump and motor. The result was a noticeable decrease in the operating temperature of the pump bearing.

Maintenance

Maintenance is the final factor to ensure gear coupling reliability for long equipment life. While the first three factors have more to do with a lack of knowledge, maintenance often comes down to a lack of execution. Unfortunately, this requires discipline by operations and maintenance groups as well as managerial courage to dedicate the resources to ensure that it can happen.

Typical recommendations from gear coupling manufacturers require regreasing at a minimum of 12 months. A regreasing procedure would include breaking, cleaning, inspecting and hand-packing the coupling with fresh grease. Using a grease gun typically is not recommended when the coupling has been broken and ready to receive new grease. When a gear coupling is greased through a fitting instead of hand-packing, it can result in overgreasing, and a hydraulic lock condition can occur, causing high axial forces on the equipment. A hydraulic lock condition can even make alignment difficult, as shafts may be hard to turn.

Some applications require regreasing at six months to ensure good reliability. These applications may include high speeds (high G forces), high temperatures, misalignment or vibration. Smaller lube sump capacity can also be a factor in regreasing intervals. However, deciding to go longer than 12 months without grease replenishment on a gear coupling is a high-risk move that is not recommended.

Regular maintenance of gear couplings should involve special care with respect to many of the installation factors discussed previously. When inspecting gaskets and O-rings, ensure the lubricant stays in the coupling until the next maintenance task is scheduled. Grease fittings should be removed before completing maintenance. These fittings have been known to leak lubricant and can hit guarding, causing loss of lubricant. Under high centrifugal forces, the grease must be completely sealed within the coupling. Guarding should also allow enough access so it does not have to be completely removed for normal coupling maintenance.

Remember, reliability is not for the faint of heart. Most all of these factors must be executed correctly to achieve good gear coupling reliability. This is why the work of maintenance and reliability professionals is rarely ever finished.

11 Simple Steps for Flushing a Hydraulic System

You are asked about a procedure for flushing hydraulic systems in order to change from one type of fluid to another. Among the ideas mentioned involved using brake cleaner, diesel fuel or some type of acid cleaning. However, brake cleaner includes a number of chemicals such as acetone and tetrachloroethylene. These solvents are known to cause problems for nitrile, neoprene, millable polyurethane and silicone seals. Ethylene-propylene (EPDM) seals have a very poor petroleum oil and solvent resistance, and are not recommended for exposure to aromatic hydrocarbons or diesel oil. Therefore, depending on the types of O-rings and seals in your hydraulic system, the solvents used in brake cleaner and diesel fuel can dry out or damage your system’s O-rings. There is also the issue of compatibility with the new type of fluid that has been chosen.
Of course, not everyone is going to do a complete teardown along with a chemical and mechanical cleaning of each component and the system each time a fluid changeover is performed. So let’s examine what should be done at the bare minimum to clean a hydraulic system.
Step 1
While the fluid is at operating temperature, completely drain the system, paying attention to the reservoir, all lines, cylinders, accumulators, filter housings or any area of fluid accumulation. Also, replace the filters.
Step 2
With a lint-free rag, clean the reservoir of all sludge and deposits. Make sure the entire reservoir is free of any soft or loosened paint.
Step 3
Flush the system with a lower viscosity fluid that is similar to the fluid to be used. A Reynolds number between 2,000 and 4,000 should be selected to achieve enough turbulence to remove particles from the lines. Stroke valves frequently to ensure they are thoroughly flushed. The fluid should be filtered and the flushing should continue until reaching one level beyond the system’s target cleanliness levels. For example, if the target is ISO 15/13/11, continue to flush the system until ISO 14/12/10 is reached.
Step 4
Drain the flushing fluid as hot and as quickly as possible. Replace the filters and inspect/clean the reservoir again.
Step 5
Fill the system to approximately 75 percent with the fluid to be used. Bleed/vent the pump. If the pump has a pressure relief or bypass, it should be wide open. Run the pump for 15 seconds, then stop and let it sit for 45 seconds. Repeat this procedure a few times to prime the pump.
Step 6
Run the pump for a minute with the bypass or pressure relief open. Stop the pump and let it sit for a minute. Close the bypass and permit the pump to operate loaded for no more than five minutes. Allow the relief valve to lift to confirm that it is flushed as well. Do not operate the actuators at this time. Stop the pump and let the system sit for about five minutes.
Step 7
Start the pump and operate the actuators one at a time, allowing fluid to return to the reservoir before moving to the next actuator. After operating the final actuator, shut down the system. Keep an eye on the fluid level in the reservoir. If the level drops below 25 percent, add fluid and fill to 50 percent.
Step 8
Refill the reservoir to 75 percent and run the system in five-minute intervals. At each shutdown, bleed the air from the system. Pay close attention to the system sounds to determine if the pump is cavitating.
Step 9
Run the system for 30 minutes to bring it to normal operating temperature. Shut down the system and replace the filters. Inspect the reservoir for obvious signs of cross-contamination. If any indication of cross-contamination is present, drain and flush the system again.
Step 10
After six hours of operation, shut down the system, replace the filters and sample and test the fluid.
Step 11
The sampling frequency should be increased until you are confident that the system fluid is stable.

Flushing Tactics

There are a lot of different ways to flush out a machine. You want to match the flushing method to the flushing condition. Following are common tactics for accomplishing this:
Drawdown Filtration/Separation — Contaminants or insoluble suspensions removed by filtration or separation technologies at normal flow rates.
High Turbulence, High Fluid Velocity, Low Oil Viscosity — Flushing is enhanced by high turbulence flushing conditions by lower flush oil viscosity and increasing oil flow rates.
High Flush Oil Temperature — This reduces viscosity, increases turbulence and increases oil solvency. Temperatures in the range of 175 to 195 degrees F are generally targeted.
Cycling Flush Oil Temperature — Using heat exchangers and coolers to change temperature during flushing across a 100 degree F range helps dislodge crusty surface deposits.
Pulsating Flush Oil Flow — Rapidly changing flow rates by pulsation help dislodge contaminants from nooks and crannies.
Pneumatic Vibrators and Hammers — Used to break loose debris from pipe walls and connectors.
Sparge Flush — Air or nitrogen is bubbled into the flush fluid to improve cleaning effectiveness.
Reverse Flush Oil Flow — By changing fluid flow direction, some contaminants and surface deposits can be dislodged and washed away.
Wand Flush Tool — Used for wet sumps, gearboxes and reservoirs with access hatches and clean-out ports. A wand on the end of a flushing hose is used to direct high-velocity oil flow to loosen deposits or for picking up bottom sediment.
Charged Particle (Electrostatic) Separators — Some suppliers have demonstrated success at removing varnish from machine surfaces and stripping out submicron soft contaminants that can contribute to varnish and sludge.
Solvent/Detergent Flush Fluid — Various solvents and detergents have been used with different degrees of success, including mineral spirits, diesel fuel, motor oils and detergent/dispersant packages.
Chemical Cleaning — These are chemically active compounds, typically caustics and acids, used to aid in the removal of organic sludge and oxide deposits.
Mechanical Cleaning — This involves the use of scrapers, brushes and abrasives, typically used with solvents and other chemicals, to remove hard adherent surface deposits.
Some adherent machine deposits require tactics that are more aggressive than a high-velocity flush, so you must match the flushing tactic and strategy to the problem you are trying to resolve with the flush. Once you understand the problem within the machine that needs to be cleaned, you can then select the appropriate flushing tactic to remedy it.
At this point, it should be obvious that a fluid change-out is not just a drain-and-fill operation. Care must be taken to confirm that the system is as clean as possible prior to introducing the new fluid. Most changeover procedures suggest that some of the old fluid will need to be either drained off the bottom or skimmed off the top of the reservoir after a period of time.
Just because the changeover has been completed does not mean that you are “home safe and dry.” Your system will need to be closely monitored for a while to make certain that the flushing was thorough. Taking the time to verify that the system is fully flushed and purged of the old fluid prior to introducing the new fluid will go a long way toward ensuring a healthier hydraulic system.

Alternatives to Lubricant Flushing
If you are experiencing pump bearing housings that are contaminated with either water, sludge or wear metals, the chosen path will depend on the nature of the contaminants. If your primary problem is an adherent contaminant (varnish), then forceful action or chemical action is likely required. You may remove some portion through normal oil changes, but this is a long-term proposition. High-velocity flush with a detergent or petroleum solvents may be useful, but as I understand, you are not in a position to go this route. There is always some risk to introducing solvents and detergents into lubricant compartments.

If your contaminant is in the bulk fluid (particulate or chemical contaminant), then a drain and fill, repeated a handful of times with short run periods between, may be sufficient. With some systems you should feel comfortable conducting a running drain and literally flushing out the old material with a large quantity of new lubricant metered in while the system is running (also known as bleed and feed). You must pay special attention to oil levels if you choose this route.
It is not difficult to install fluid quick-connect couplings on most existing sumps, even with the machines running. Again, attention to the oil level is important. You should install fluid quick-connect fittings and use a filter cart well above the other alternatives.
When using a filter cart, the oil is taken from a dirty sump, filtered and returned to the dirty sump. The cleanliness of the filtered oil is diluted, so to speak, by the dirty oil residing in the tank. To overcome the dilution effect, the tank volume must pass through the filter approximately seven times to achieve the equivalent of single-pass filtration (where the oil is pumped from one container to another through a filter).

For example, if you have a 30-gallon tank and a filter cart that pumps at 5 gallons per minute (gpm), you need to run the cart for 42 minutes to equal single-pass filtration (30 gallons multiplied by 7, divided by 5 gpm). If you want to achieve two-pass filtration, you must engage the offline filter for 82 minutes or about an hour and a half.
Even with heavily varnished surfaces, the right type of filtration equipment can resolve the problem.
Can Oil be Over Filtered?
The question of whether more is always better when it comes to filtration is a common concern. The answer isn’t as simple as you might think. It has been proven that cleaner oil decreases bearing and machine wear, thus increasing equipment life expectancy. However, there are issues to consider when striving for very low ISO cleanliness codes.

One of the first things to take into consideration is the machine’s tolerances and need for clean oil. Hydraulic systems are notorious for needing clean oil, especially when compared to an industrial gearbox. That’s not to say that gearboxes don’t require clean oil. It just depends on the machine’s age, criticality and equipment cost. In other words, the fluid cleanliness should be matched to these conditions.
After determining the required machine cleanliness, you must select a filter to achieve these levels. The filter’s micron rating is commonly referred to as the benchmark of filter performance, but this only tells half the story. The beta ratio completes the picture of the filter’s true performance and capability. While the micron rating tells you how fine or how coarse the filter media is, the beta ratio tells you how efficiently it catches particles at that micron value. For instance, while having a 3-micron filter is good, it doesn’t tell you much about the filter. It could be a 3-micron filter with a beta ratio of 2, which is only 50 percent efficient, or as high as 2,000, which is 99.999 percent efficient at the same micron value.
Some filters can actually filter at a sub-micron level. As they become more aggressive, filters can begin to strip out some additives, affecting lubricant health. For example, defoamants are among the most common additives to be filtered out, as they are quite large. Depending on the filter media, other additives may be at risk as well. If using a chemically active filter such as fuller’s earth, polar additives (extreme pressure, anti-wear, demulsifiers, etc.) can be stripped, affecting the lubricant’s additive package and ability to protect the machine’s surfaces.
While clean oil is always better, balancing the needs of the machine with the cost of cleaning the fluid can lead to greater reliability and fewer failures. Remember, when it comes to filtration, it isn’t a one-size-fits-all approach. All systems have unique requirements for cleanliness, and they should all be viewed independently.

Contamination Control – Best Methods for Purifying Engine Oil
Here is a scenario where the end-user’s preferred method for minimizing the content of unwanted debris in lube oil in diesel engines with up to 2,000 liters of lube oil in the sump is monitored regularly by the oil supplier, which tells the end-user when to change lube oil. However, the manufacturer recommends an oil change every 1,000 hours. The end-user installed an offline filter, and the oil company report said the oil was useable up to 3,000 hours.
For a long time, the end-user has used centrifugal purifiers, which have done a good job, but the end user also know they have their limitations when it comes to removing smaller and lighter particles from the oil. The end-user is now looking into substituting the purifiers with offline filtration, which would be able to take out smaller particles along with water. Then the end-user has glycol and fuel dilution to consider as well. The end-user has to maintain the engines regarding these matters, but his main issue is to find out what is the best purification method of diesel engine lube oil. Is it a purifier or bypass filtration?
First, you shouldn’t allow oil suppliers to conduct the analysis and tell you when to change the oil. It is in their best interest for you to perform more frequent oil changes than may be required. Instead, use an independent lab test and change the oil based on the results. You may find that you are able to get more life from the oil. Remember, world-class lubrication programs use a condition-based approach rather than a time-based approach for lubricant change-outs.
Secondly, there is no mention of testing the oil upon receipt or prior to transfer. Studies have shown that it is 10 times more expensive to remove contaminants once they are in the oil. Your oil should be tested upon receipt to ensure that you are receiving clean oil from your supplier. In addition, every time the oil is transferred from one container to another it should pass through a filter. Use quick-connect fittings and a product-dedicated filter cart to fill and drain oil from sumps to stop particle ingression.

If you have issues with either fuel or glycol in your oil, removing those contaminants should not be your focus. Having fuel/glycol in the oil is only a symptom, so you must fix the problem. Once these fluids find their way into your oil, they are very difficult and expensive to remove. Check the system for coolant leaks and fix them. In the case of fuel, look for problems with injectors or air filters, which will affect the fuel/air ratio and can cause soot loading.
The best method of purification would be to use a combination of both purifiers and bypass filtration, since each has its limitations. Centrifugal purifiers are good at removing larger particles and water but not for removing the smaller organo-metallic particles, which a filter will remove. If you already have purifiers, keep them and add bypass filtration.

Best Lube Practices for Chain Drives and Conveyors
A chain is a series of traveling journal bearings with a means to engage the teeth of a sprocket and transmit force and motion. Because each chain joint is a bearing, proper lubrication is essential to obtain the maximum service life from a chain drive or conveyor.
Parts of the Chain
Pitch – The nominal distance between the centers of consecutive chain joints. That would be the distance between consecutive rollers in roller chain and offset side bar chain, and between consecutive pins in silent chain.
Side Bar – The tension members connecting consecutive joints in an offset sidebar chain.
Link Plates – The tension members connecting consecutive joints in a roller chain.
Joint – The place in a chain where the chain articulates to engage the sprocket.
Guide – A plate or rail on which a chain, usually a conveyor chain, rides.
Pin – The innermost member of a chain joint. The pin articulates inside the bushing in roller and offset side bar chains, and it usually is pressed into the outer link plates or the wide end of the side bars.
Bushing – The intermediate member of a chain joint in roller and offset side bar chains (silent chains may not have bushings). The bushing is fitted between the pin and roller, and it usually is pressed into the inner link plates or the narrow end of the side bars.
Strand – In roller chain, multiple rows of link plates, bushings and rollers are sometimes assembled onto a common pin. Each row of links is called a strand.
Chains for Drives

The three most common types of chains used for drives are: precision roller chain, covered by American National Standard ASME B29.1; silent (inverted-tooth) chain, covered by ASME B29.2; and engineering steel offset sidebar chain, covered by ASME B29.10. Roller chains are produced in 0.25 through 3.0-inch pitch and are used for a wide variety of drives in the slow to high-speed range. Silent chains are produced in 0.375 through 2.0-inch pitch, run smoother than roller chains, and are used mainly in high-speed drives. Engineering steel chains are made in 2.5 through 7.0-inch pitch and are used mainly in slow-speed drives.
Chains for Conveyors

Both precision roller chains and engineering steel roller chains are commonly used in slat, apron, pusher and crossbar conveyors. Welded steel chains are widely used in scraper and drag chain conveyors. Forged link chains are frequently used in overhead trolley and floor conveyors. Precision roller chains, engineering steel roller and rollerless chains, cast chains, polymeric chains, flat top chains and silent chains are used in plain chain and carrier chain conveyors. Space limitations will permit covering only a few of the most widely used types of conveyor chains here.
How Chains Fail

The three most common ways that a chain may fail are tensile, fatigue and wear. In a tensile failure, the chain is overloaded in tension until it is stretched so badly it will not function properly, or it is literally pulled apart. In a fatigue failure, the chain is loaded repeatedly in tension, at a load below the yield strength (the chain is not stretched), until microscopic cracks develop in the link plates or sidebars. These cracks continue to grow until the chain breaks. In a wear failure, material is removed by sliding, or sliding combined with abrasion or corrosion, until the chain will not function properly (will not fit the sprockets) or the remaining material is so thin that it lets the chain break. This article covers only the lubrication of commonly used steel bushing and roller chains to reduce the effects of wear.
Chain Wear

Most often, wear between the pin and bushing causes the chain to elongate (grow longer but not stretch) until the chain will not fit the sprockets correctly or will not maintain correct spacing or timing. Sometimes wear between the roller and bushing or wear between the link plates or sidebars and guides causes the chain to malfunction.
Chain wear elongation usually progresses through three stages. First, there is a short period of rapid initial, or run-in wear. In this first stage, high spots are worn off the pins and bushings and minor misalignments are quickly worn away. Second, there is a period of constant slow, or lubricated wear. In this second stage, the pins are seated properly in the bushings and the bearing areas are normally well-lubricated. And finally, there is another period of rapid, or terminal wear. In this final stage, lubrication may have become ineffective or failed completely, or the hard case on pins and bushings may have worn through, or chain elongation on the sprocket may have caused loads on individual joints to increase dramatically.
Lubrication Effects on Chain Operation

The majority of chain drives and conveyors will perform better and last longer when timely and adequate lubrication is provided. One rule-of-thumb is that proper lubrication can extend chain life by as much as 100 times.
Even if overall chain life is acceptable, lack of proper lubrication can cause other problems. When a chain is starved for lubrication, wear from one joint to another can vary greatly, causing erratic action. Rapid joint wear can cause early loss of timing in a conveyor. Lack of lubrication can increase friction and power consumption and cause a harmful temperature rise.
Need for Lubrication

Chain lubrication is needed mainly to slow the wear between the pins and bushings in the chain joints, to flush out wear debris and foreign materials, and to smooth the chain’s engagement with the sprocket. Additionally, lubrication may be needed to inhibit rust and corrosion, to carry away heat, and to cushion impact forces.

Chain Lubricants

A chain lubricant should have low enough viscosity to penetrate into critical internal surfaces and high enough viscosity, or necessary additives, to maintain an effective film at the prevailing temperature and pressure. The lubricant should have the capability to maintain the desired lubricating qualities under prevailing operating conditions, and be clean and free of corrodents.
A good grade of nondetergent petroleum base oil usually is acceptable. While detergents are not normally needed, antifoaming, antioxidizing and extreme pressure additives are often helpful. Impure oils should be avoided. Acids or abrasives in the oil can permanently damage the chain.
The chain manufacturer often uses grease or petroleum jelly as an initial lubricant. However, users generally should not apply greases to chains in service because they are too thick to penetrate into the internal bearing surfaces of the chain. Users should use grease only when fittings for injecting the grease into the chain joints are provided.

Lubrication of Chain Drives

The recommended method of lubrication for chain drives is indicated in the power rating tables published in ASME B29 Series Standards and in various manufacturers’ catalogs. The methods normally listed are manual, drip, oil bath, slinger disk and oil stream. In all methods, the oil should be applied to the upper edges of the link plate or sidebar in the lower span of the chain. This enables gravity and centrifugal force to carry the lubricant into the critical bearing areas.

Manual Lubrication

In manual lubrication, the user applies oil periodically with a brush or spout can. The preferred frequency is once every eight hours, but a longer interval may be used if experience shows it is adequate for that particular drive. The amount of oil and the frequency of its application must be adequate to prevent the formation of a reddish brown discoloration in the chain joints. That discoloration indicates that red iron oxide (rust, hematite, etc.) is being generated in the chain joints because they are not receiving sufficient lubrication.

Drip Lubrication

In drip lubrication, oil is dripped between the link plate or sidebar edges at a rate from four to 20 drops per minute, depending on speed. Again, the amount of oil and the frequency of its application must be adequate to prevent the formation of a reddish brown discoloration in the chain joints. In drip lubrication of multiple strand chains, a wick-packed distribution pipe may be used to uniformly distribute oil to all rows of link plates or sidebars.

Oil Bath Lubrication

In oil bath lubrication, a short section of the chain runs through the oil in the bottom of the chain casing. The oil level should extend only to the pitch-line of the chain at its lowest operating point. Having long sections of chain run through the oil bath can cause oil foaming and overheating.

Slinger Disk Lubrication

In slinger disk lubrication, a rotating disk picks up oil in the bottom of the casing and slings it against a collector plate. The oil is then directed into a trough that drops it onto the upper edges of the link plates or sidebars in the lower strand of the chain. The chain should always run above the oil level in the casing.

Oil Stream Lubrication

In oil stream lubrication, the oil is pumped under pressure to nozzles that deliver a stream or spray onto the lower span of the chain from the inside of the loop. The oil spray should be distributed uniformly across the entire width of the chain.
The excess oil is collected in the bottom of the sump and returned to the pump via a reservoir. An oil cooler may be used to keep oil temperature below the maximum limit.

Periodic Maintenance

For manual lubrication, ensure that the designated schedule is followed and the specified grade of oil is used. If the chain is dirty, wipe it clean with kerosene or a nonflammable solvent before relubricating.
For drip lubrication, ensure that the flow rate is as specified and that oil is properly directed onto the chain. Check the oil level in the reservoir at least daily and refill as necessary.
For oil bath, slinger disk and oil stream lubrication, check the oil level in the casing or reservoir at least daily and add oil as necessary. At that time check for leaking, foaming or evidence of overheating. Ensure that all orifices and nozzles are clear and that oil is properly directed onto the chain. Change the oil after the first 50 operating hours and then after every 500 operating hours.

Lubrication of Chain Conveyors

The method of lubricating chain conveyors is generally governed by speed, environment and accessibility. Some method of continuously or periodically lubricating the chain conveyor in service should always be considered. Not lubricating a chain conveyor is a reasonable option only if one of the special chains (sealed joint, etc.) is used.
Manual lubrication is normally sufficient for slow-speed conveyors. Manual lubrication may sometimes be adequate for moderate-speed conveyors, but drip or brush lubrication is often needed. Drip lubrication is often required for high-speed conveyors, and continuous oil stream lubrication may sometimes be needed. Whatever the method, the oil should be applied to the upper edges of the link plate or sidebar in the lower span of the chain. This enables gravity and centrifugal force to carry the lubricant into the critical bearing areas.
In reasonably clean, dry, nonabrasive environments, drip or oil stream lubrication is quite acceptable. However, in dirty, abrasive environments, where the combination of continuous lubrication and abrasive grit can cause rollers and joints to stick, periodic cleaning and manual lubrication may be better. In extremely high or low temperatures, special synthetic lubricants may be required. In wet environments, special lubricants or coatings may be needed.
When accessibility is limited, special remote-fed drip or intermittent-spray lubrication systems may be necessary. Also, special remote-controlled chain cleaning systems may be needed.

Manual Lubrication

In manual lubrication, oil is applied to the chain with a brush or spout can. The preferred frequency is at least once each day, but the interval may be longer if experience shows it is adequate for that particular application. The amount of oil and the frequency of its application must be adequate to prevent the formation of a reddish brown discoloration in the chain joints. That discoloration indicates that red iron oxide is generated in the chain joints because they are not receiving sufficient lubrication.

Brush Lubrication

In brush lubrication, oil is continuously brushed on the lower span of the chain from the inside of the loop. The amount of oil and the frequency of its application must be adequate to prevent the formation of a reddish brown discoloration in the chain joints.

Drip Lubrication

In drip lubrication, oil is dripped between the link plate or sidebar edges at a rate from four to 20 drops per minute, depending on speed. Again, the amount of oil and the frequency of its application must be adequate to prevent the formation of a reddish brown discoloration in the chain joints.

Oil Stream or Spray Lubrication

In oil stream lubrication, the oil is pumped to nozzles that deliver a stream or spray onto the lower span of the chain from the inside of the loop. The oil spray should be distributed uniformly across the entire width of the chain.

Periodic Maintenance

The same guidelines given for periodic maintenance of manual and drip lubrication of chain drives apply to chain conveyors.
For oil stream lubrication, check the oil level in the reservoir at least daily and add oil as necessary. Ensure that all orifices and nozzles are clear and that oil is properly directed onto the chain.

Use of OEM Breathers and Dust Caps

Most original equipment manufacturer (OEM) accessories like breathers do little to restrict the ingression of tiny particles into oil and critical spaces, which can damage machine surfaces. Some of these breathers are simply a cap filled with steel wool or a mesh screen that serves as a block for larger particles. Considering the lubricant film in a journal bearing is approximately 5 to 10 microns, any particles of this size contaminating the oil will greatly increase the likelihood of wear and subsequent machine failure. These tolerance-sized particles do the greatest damage and have the highest probability of causing machine wear. Most OEM breathers and dust caps allow particles and moisture to enter the oil.

Not only do many OEM breathers allow particles into the oil, they also do nothing to restrict moisture from entering the oil. Oil is hygroscopic, which means it absorbs moisture from the ambient air. In areas with high humidity or steam, moisture will pass through these types of breathers and be absorbed into the oil, causing rust, increased oxidation and hydrolysis rates, and a higher corrosive potential of acids formed by oxidation and hydrolysis.
How Desiccant Breathers Control Contamination

To combat the ingression of particles into oil systems, breathers are often attached to reservoirs and other oil storage components. Whether they are connected to an expensive piece of machinery or a drum of oil, breathers offer the peace of mind that as the oil level fluctuates, the air filling the space will be properly cleaned and mostly free of contaminants.
Desiccant breathers provide a wide range of benefits and are becoming more common. However, you may wonder how a plastic cup full of what looks like plastic beads actually filters incoming air and removes not only harmful particles but also water vapor, which is so dreaded in lubrication systems. The answer involves chemistry.

These breathers use the inherent qualities of two of nature’s most absorbent materials – silica and carbon. Everyone likely has opened a package and found little packets marked “Do not eat.” This is the same silica in desiccant breathers. How it works is quite simple. Silica is a very porous material that can trap and hold nearly 40 percent of its weight in water. As water vapor passes around these beads, it is trapped in the pores of the silica. Any water vapor that isn’t trapped by the silica goes through a layer of activated carbon.

Electronegativity is a chemistry term used to describe an element’s attractive force toward other elements. Carbon and oxygen both have high values and are attracted to each other to form new gases, such as carbon dioxide. Water vapor attaches to carbon by this force. The oxygen in the water binds with the activated carbon in the breather, thus preventing it from going any farther.

Most breathers also have a color-change indicator that shows when their useful life is up. This is accomplished with a water-reactive reagent embedded into the body of the silica. As water vapor attaches, it reacts inertly with the reagent, making it change its color.
Desiccant breathers generally have a synthetic fiber filter at the top to trap larger solid particles such as dust or organic material in the atmosphere. Next, there is a device called a diffuser, which takes incoming air and forces it through the entire volume of silica evenly. After the diffuser is the activated carbon, which serves to remove anything left after the initial filtration. As the container exhales, this process takes place in reverse, with the activated carbon absorbing the oil mist so as not to allow it back into the mass of oil after being in contact with other contaminants.

It is recommended that these breathers be installed in tandem with a vacuum gauge. In the case of dry environments, there may not be enough moisture ingression to cause a color change of the silica beads before the top layer of the synthetic filter is clogged with dust and other contaminants. A vacuum gauge will provide a visual signal as to when this occurs, since the air will not be able to pass through the entire breather.
As with most spin-on breathers, desiccant breathers often have a beta rating associated with them. This is a mark of how well the filter removes incoming contaminants.

Among the other criteria to keep in mind when selecting a filter is the cleanliness of the environment, which can affect its life expectancy. Obviously, the dirtier the air, the more particles the breather will trap. The amount of moisture or humidity in the air will determine how long you can go between filter changes.
The criticality of the machinery the breather is attached to is important to consider as well. If the machine operates on close tolerances with little room for particle ingression, you may need to get a high-quality breather and change it more regularly.
To maximize a breather’s efficiency, ensure the headspace of the oil level is sealed tightly. The volume being protected should breathe only through the filter installed. A loose seal will defeat the purpose and allow a straight path for outside particles to enter the system.
Although breathers are relatively easy to install, the process of how they work is quite involved. Pairing science with real-world need provides the advantage required to tackle the challenges of particle ingression and maintaining the small fluid film on which this industry rides.
3 Key Properties of a Breather
Desiccant breathers can help control both moisture and dirt ingression. A good desiccant breather system is one that:
1. achieves the target level for cleanliness and dryness,
2. has the capacity to enable a sufficient service interval between change-outs,
3. is easily visible for routine inspection during preventive maintenance.
In conclusion, the voice in your oil is an opportunity for those who perform or are considering performing a system flush. It would be rare for a machine to have a flush requirement without both the causes and effects appearing in the oil data well in advance, but only when samples are taken and the right tests are performed. This is just another reason why learning the language of oil analysis is a valuable, enabling skill in the field of machine reliability.

Unearth the benefits of GG Friction Antidote – An investment that pays off and your benefits at a glance:

Innovative tribological solutions are our passion. We’re proud to offer unmatched friction reduction for a better environment and a quick return on your investment. Through personal contact and consultation, we offer reliable service, support and help our clients to be successful in all industries and markets.

Profitability:

Switching over to a high-performance lubricant pays off although purchasing costs may seem higher at first, less maintenance and longer vehicles/machinery parts lifecycle may already mean less strain on your budget in the short to medium term.

Continuous production processes and predictable maintenance intervals reduce production losses to a minimum. Consistently high lubricant quality ensures continuous, maintenance-free long-term lubrication for high plant availability. Continuous supply of fresh GG Friction Antidote treated lubricant to the lubrication points keeps friction low and reduces energy costs.

Safety:

Longer lubrication intervals reduce the frequency of maintenance work and the need for your staff to work in danger zones. Lubrication systems can therefore considerably reduce occupational safety risks in work areas that are difficult to access.

Reliability:

GG Friction Antidote treated lubricants ensure reliable, clean and precise lubrication around the clock. Plant availability is ensured by continuous friction reduction of the application. Lubrication with GG Friction Antidote treated lubricants help to prevent significant rolling bearing failures.

Need a good ROI? How about 3,900%?

It may sound too outrageous to be true, but the Institute of Mechanical Engineers estimates every $1,000 spent on proper lubrication yields $40,000 in savings.

INSTANT ROI FOR OPTIMIZING YOUR LUBRICATION REGIMEN

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The information in this literature is intended to provide education and knowledge to a reader with technical experience for the possible application of GG Friction Antidote.  It constitutes neither an assurance of your vehicle/machinery optimization nor does it release the user from the obligation of performing preliminary tests with GG Friction Antidote. We recommend contacting our technical consulting staff to discuss your specific application. We can offer you services and solutions for your heavy machinery and equipment.

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