Lube Tips

Focus: Contamination Control

Portable transfer/filter carts are versatile and can be used for more than just transferring fluids. Other possible uses include offline filtration, cleaning stored lubes, flushing after machine repair and rebuild, flushing during equipment commissioning and draining a reservoir or sump.

The presence of water in lubricating oils can shorten bearing life down to one percent or less, depending on the quantity of water in the lubricant.

Monitor your filter change interval. Premature plugging is usually a sign of a potential problem that merits further investigation. This may be caused by airborne dust coming from nearby construction or a prolonged dry spell raising atmospheric dust levels. Whatever the source of dirt, the root cause needs to be investigated and perhaps the seals or breathers need to be serviced or upgraded accordingly.

Hydraulic system leakage prevention and control is an important component of any world-class lubrication program. Beyond the obvious and substantial replacement cost of lost fluid, there is the additional expense of removing contaminants that enter the fluid system via the leakage path. If not promptly removed from the system these contaminants will likely result in additional maintenance and possibly production related losses due to component failure. Remember: where oil leaks out, moisture and particulates creep in!

One study reported in Hydraulics & Pneumatics magazine analyzed over 1000 hydraulic system seal failures from a variety of industries. It reported that the most common root cause of seal failure, by a wide margin, was hydraulic fluid contamination, accounting for 21.4% of failures. Contamination causes seal failures, which allows further contamination of the fluid, resulting in additional seal damage.

Want to read more about contamination control? Here's a great article called "What Particles Mean and Why They Need to be Monitored and Controlled."

Q & A
"My lube supplier is recommending that I begin using high performance products to extend my reservoir change cycles. Does this work?"

This approach can work for some equipment. However, the issue of sump management still needs to be addressed. If you want to extend change cycles, you need to know when the oil needs attention. A calendar cannot give you this insight. You, or your supplier, should still set up an analysis program and begin tracking the lubricant products and machinery.

If this is how the supplier intends to validate the extension, and if the supplier has a well-developed plan complete with formulas to improve monetary value - then the approach may have merit. However, if the supplier wants your faith in his product that you can make the extension without any further input, then question the approach very carefully.

Success Stories
Scott Mizell at Weyerhaeuser Flint River Operations implemented an aggressive contamination control and on-site oil analysis program. A baseline of the machines' cleanliness levels revealed hydraulic machines and lubricated machines were operating at ISO 19/17 and 22/19 respectively.

Four primary sources of this contamination were targeted: new oil, built-in during manufacture or repair, ingested from the environment and internally generated. Multiple changes were made including the addition of desiccant breathers on reservoirs and new oil storage tanks, off-line filtration and portable filter carts were employed, random cleanliness checks at rebuild shops, and sealed, small volume containers were used for make-up.

Routine oil analysis such as particle counting, moisture testing, viscometry and some microscopic analysis, is performed onsite. More extensive testing like elemental spectroscopy, acid number, etc., however, is reserved for an outside laboratory.

Since implementing this program, downtime has been reduced by 90 percent and repair costs have been reduced 74 percent. When a dollar in maintenance costs is avoided, that money goes directly to the operating profit line because there is no cost of goods sold associated with the improved revenue. That makes the repair cost reductions especially important to overall profitability. Because cost reductions and production improvements occur simultaneously, proactive maintenance pays both coming and going at Flint River.

Today's Tip
Store tubes of greases vertically, not on their sides. This will minimize the amount of oil loss from bleeding, keeping the containers and storage area in better condition

Book Bits
From the book "Wear Debris Analysis":
Spectrometric Identification

An important 'tool' used by analysts world-wide in determining material composition is spectrometric analysis. The spectrometric examination of particles usually requires much more expensive laboratory equipment. The glossary of terms [in Chapter 6] describes a number of these analyzers, but generally what is achieved is a listing of the elements within the particle, or the compounds present. Where proportions are also determined actual metal alloys can be identified, and hence the most likely origin of wear particles. Where compounds are suggested then the presence of additives as well as debris may be decided. Those spectrometers which require the particle to be burnt will only work where the mass of the particle is sufficiently small. This means that the size limit associated with each spectrometer must be adhered to, otherwise totally misleading results will be achieved (8 microns, or less, may be the maximum particle size to be detected).

The basic idea of spectrometry is to cause the elements in a sample substance - in our case, the debris particle - to become excited and give away their presence! The excitation may arise from X-rays or high temperatures (up to 10,000 K), and the detection of the elemental wavelength could be by a photographic monochromator or ion detectors.

Q & A
"We are looking at changing lube suppliers soon and I have been told that mixing products from the two suppliers can present compatibility issues. What advice can you offer?"

In general, it is never a good idea to mix different oils because there is always a possibility that the two will be incompatible, particularly the additives in each oil. Of course, changing lube suppliers is a fact of life and you cannot be expected to drain every last drop of oil from the old supplier from your equipment and replace it with the new oil!

The first step is to discuss with the new supplier any incompatibilities that are known between corresponding products from each vendor that will be used in the same application. Usually, they will provide a cross-reference guide of equivalent products that are compatible and have the same minimum performance specifications. If any doubt exists, compatibility testing should be conducted as follows:

Take three different mixes of oil A and oil B, one at 50:50, one at 90:10 and the third at 10:90 and test for filterability, sediment (possibly caused by additive drop-out), color and clarity, RPVOT, storage stability, demulsibility, rust and corrosion inhibition, air release and foaming tendency. Provided all mixtures pass these performance tests, there is a good possibility that the two oils are compatible. More care should be taken with grease compatibility issues. With greases, the biggest problem is compatibility of soap thickeners. Incompatible greases can either thicken or thin when mixed and extreme care must be taken when switching from one product to another. Without any evidence to the contrary, all greases should be treated as incompatible and equipment be thoroughly cleaned and purged before introducing the new grease.

Today's Tip
Suction line leaks can cause air entrainment and cause problems such as excessive aeration, air lock, pump cavitation, poor lubrication and premature oil degradation. A pinhole-sized suction line leak can be hard to find, however, using a small amount of shaving foam sprayed over the suspected leak area can indicate the source of the problem as the foam is drawn into the line. This method should not be used for large leaks and care should be taken not to use too much soap since this can cause contamination of the lube, resulting in foaming and aeration problems and poor demulsibility.

Book Bits
From the book "Machinery Failure Analysis and Troubleshooting":
Any load-carrying contact, even when rolling, requires the presence of lubricants for reliable operations. The curvature of the contact areas between rolling element and raceway in normal operation results in minute amounts of sliding motion in addition to the rolling. Also, the cage must be carried on either of the rolling elements or on some surface of the bearing rings, or on a combination of these. In most types of roller bearings, there are roller end faces which slide against a flange or a cage. For these reasons, adequate lubrication is even more important at all times. The term "lubrication failure" is too often taken to imply that there was no oil or grease in the bearing. While this happens occasionally, the failure analysis is normally not that simple. In many cases, a study of the bearing leaves no doubt in the examiner's mind that lubrication failed, but why the lubricant failed to prevent damage to the bearing is not obvious.

When searching for the reason why the lubricant did not perform, one must consider first its properties; second, the quantity applied to the bearing; and third, the operating conditions. These three concepts comprise the adequacy of lubrication. If any one concept does not meet requirements, the bearing can be said to have failed from inadequate lubrication.