Up Front

Lubrication Procedure Saves Man-Hours
We recently installed new textile machines in our facility that had more than 100 small gear assemblies per machine. The OEM recommended procedure for the gear assemblies was to remove a number of side plates along each side of the machine and then reach inside and across to the other side of the machine with a long-handled brush. Using the brush, we were to apply a coating of grease to one of the gears while the machine is running. This would distribute the grease to three other gears within the assembly.

This procedure would have required at least eight eight hours of labor and there would have been a risk of contaminating the grease during the application. Also, when removing the side plates, electrical components would have been exposed, creating a safety issue.

We disassembled one of the casings which held a gear assembly and found that there was a small access hole in the front of the casting which would allow us to insert a grease needle into the casting with no danger of it contacting any of the gears. It allowed us to apply grease to one of the gears quickly with no disassembly.

After experimenting with the grease quantity, we are now able to grease more than 100 gear units in less than 30 minutes with no safety risk and little risk of contamination.

The point is that even though a manufacturer may recommend a specific lubrication procedure, it is good to scrutinize it to determine if it is in fact the best method. This can also be done with recommended lubrication frequencies which can vary greatly depending on the environment and loading of equipment.

Submitted by Stan Morgan, Maintenance Engineer, Advanced Glassfiber Yarns. Thanks Stan!)

Book Bits
How Multi-grade Oils Work
From "The Practical Handbook of Machinery Lubrication":

Multi-grade oils are made by blending a low viscosity oil with special additives called Viscosity Index improvers. For example, when these polymer additives are blended in the correct proportion with an SAE 15W oil, the oil flows like an SAE 15W oil at low temperatures and like an SAE 40 oil at high temperatures. The result is an SAE 15W/40 oil that will provide wide protection over an extended temperature range.

Today's Tip

To improve the reliability of grease-lubricated couplings, use only greases formulated for that purpose. General-purpose greases often have thickeners that are heavier than the oil. When subjected to the continuous and extreme forces of a spinning coupling, the thickeners in general-purpose greases can centrifuge to the outside, leaving the oil on the inside. Unfortunately, the outside is where the oil is needed. The thickeners in coupling greases are equal in weight to or lighter than the oil, ensuring that the wearing parts in the coupling are well lubricated. (Tip submitted by Douglas Branham, Lubrication & Reliability Mgr., Lubrication Systems Company. Thanks Douglas!)

Q & A

Solution to High Temp Gearbox Lubrication
"We have a cooling tower fan gearbox, which due to the operating environment runs very hot (>180°F). We recently inspected the gearbox and found a lot of sludge and deposits and a strong sulfur smell. Someone suggested we use synthetic oil instead of the mineral oil currently used to prevent this from reoccurring. What are your thoughts?"

While it is true to say that synthetic oils can be used at higher temperatures, because they do not thin out as quickly as the corresponding grade of mineral oil, and provide better oxidation resistance, this may not be the best solution in this instance. This is particularly true, because the sulfur smell you refer to is likely the thermal breakdown of the EP additive in the oil. Switching to a synthetic oil will do nothing to prevent thermal additive decomposition, if this is the problem.

A better solution may be to install an offline cooling system by piping out a line from the gearbox with a small gear pump to circulate the oil through an external cooling system, returning the cooled oil to the gearbox sump. Not only will this help to cool the oil and prevent thermal and oxidative breakdown, it will also have the effect of increasing the gearbox sump size, allowing the oil more opportunity to cool the gearbox.

A nice side benefit of this arrangement is that the offline system can also be equipped with a filter to help keep the oil clean, and an oil sampling valve to take oil samples on a component that is often difficult to sample on the run.

Mark Barnes, Senior Technical Consultant, Noria Corporation

Issue Focus:

Oil Analysis Instruments

To better track the formation of serious wear debris in machine components, consider trending percent large particles (PLP) as part of your DR Ferrography analysis. PLP will indicate the relative fraction of the total ferrous debris that is indicative of serious wear problems. Simply subtract the reported small particle concentration from the large, and divide by the total. A shift from normal results should prompt further evaluation.

Be sure to watch particle counts, water content, spectrometry iron trends and others as supplemental tests. Iron oxides (rust) is often nonmagnetic and could result in a false negative, even though those particles may still be wear particles of great interest. Know the limitations of your tests for best results.

A particle counter is helpful in providing information on:

oil cleanliness level
filtration performance
abnormal wear conditions
effectiveness of corrective maintenance
problem isolation
identifying the need for ferrographic analysis
identifying the use of dirty top-up containers or dirty new oil

Emission spectroscopy is a test that determines the concentration of elements in an oil sample by measuring the light emitted at specific frequencies as the sample is vaporized at high temperatures.

It is possible to determine whether particles identified under your microscope are two or three dimensional. First focus on the general background of smaller particles. If the particle of interest is in focus, it is two dimensional. The amount of refocusing necessary to bring it into focus roughly indicates it's thickness.

AN (Acid Number) and BN (Base Number) test repeatability is typically plus or minus 10%.

Up Front
Double-check of Lube Specification Saves the Day
An important component of the safety systems at the Ontario Power Generation facility in Pickering, Canada is the standby generator. While preparing a plan to flush and refill the power turbine, it was discovered that the Procurement Department had inserted a "No Purchase" comment in the CMMS system associated with the ISO VG 32 turbine oil usually used, recommending instead that a different, less expensive product be used.

After researching the two products, it was found that the original product was formulated from a Group II basestock, while the less expensive product was a Group I. The Group I basestock oil has a higher cloud point (indicating a less refined product with greater wax content). In the past, usage of this product had caused equipment problems in cold-start situations. Cold oil in the coolers had a tendency to cause large pressure drops across the filters, resulting in low oil pressure trips of the emergency shut-down system. This is why the Group II was used in this application.

Fortunately, the Procurement Departments error was identified before the inferior product was introduced to the equipment, and therefore no damage occurred.

A quick call to the Procurement Department reminded them that price differences shouldn't be used as the primary criteria for selecting lubricants.

Submitted by Khalid Malik, Technical Engineer/Officer, Ontario Power Generation. Thanks Khalid!)

Book Bits
How Water Affects Additives
From "Fluid Contamination Control":

Water in tribological fluids (other than water-based fluids) leads to a multitude of problems in terms of system damage and failure. Perhaps the worst threat of water contamination in storage is its reaction with additives and the damaging reaction products.

Moisture causes a filter-clogging slime to form in fluids containing tricresyl phosphate (TCP), an antiwear additive used in tribological fluids where an alkali is present. If ZDDP (zinc dialkyl dithiophosphate) is used as the antiwear additive instead of TCP, many deteriorating mechanisms could exist; suffice to state here that ZDDP can decompose to form hydrogen sulfide and, in the presence of moisture, transform into a highly corrosive acid (sulfuric acid). Even in fluids of the corrosion-prevention type, moisture causes an egg-white type slime. According to T.N. Dean, when moisture is present, corrosion-preventive additives can exhaust themselves by "wrapping up" the moisture in additive and water dispersion.

Today's Tip
When changing pillow block bearings with a cylindrical OD on the outer race, be sure to clean the grease channel located in the housing prior to installation of the new bearing. The grease in the channel tends to attract dust and dirt over time. When the bearing is changed, this dirt can become displaced into the grease channel as the new bearing is tipped into the housing. The dirt can either pass through the application hole in the outer bearing race or plug off the hole, resulting in damage to the new bearing. (Tip submitted by Greg Neuenfeldt, Dow Corning. Thanks Greg!)

Editors Note: Regarding last week's tip about using spin-on filters as air breather filters on reservoirs and gearboxes:

If you plan to use automotive spin-on filters for breathers, drill holes in the base of the filter outside of the gasket area. Automotive filters have a built-in anti-drainback valve that won't let air out unless these holes are drilled.

Normal industrial filters, like those used in hydraulic applications and filter carts, etc., don't require holes to be drilled.