In This Issue:

• Up Front: Lubrication Procedure Saves Man-Hours

• Book Bits: How Multi-grade Oils Work

• Today's Tip: Grease-lubricated Coupling Tips

• Q & A: Solution to High Temp Gearbox Lubrication
  

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!)

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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.

Click here for more information about "The Practical Handbook of Machinery Lubrication".

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!)

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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