Q & A

Water Contamination Removal
"Our lube oil testing/analysis often shows levels of water present in the oil. We are considering the purchase of portable equipment suitable for the removal of water from lube and hydraulic oil systems. I have also been told by some people that some separators can only remove water down to the water saturation level of the oil. Is there a preferred method for removing water from oil in a lube or hydraulic circulating system? How much water can be removed by these methods?"

Water in any lubrication system is bad news. In hydraulic systems, it can result in vaporous pump cavitation, corrosion and valve stiction, while in circulating lube oil systems it can cause oil film strength loss, rusting and other serious mechanical problems.

The effects of water on the oil are often overlooked. Excessive water contamination can result in premature oil oxidation and promote the build up of sludge and varnish. In ester-based fluids, it can result in the hydrolytic destruction of the base fluid resulting in the formation of corrosive acids. In some circumstances, water can also strip additives from the oil through water washing or hydrolysis resulting in premature oil degradation.

For these reasons, the best strategy when it comes to water is to monitor and control the root cause of the water ingression. This can be achieved by ensuring that all seal and breathers are in good shape (consider using desiccant style breathers), lube tank hatches are closed and sealed properly and that top-up oil is stored and handled properly.

Water can exist in three phases in an oil, free, emulsified and dissolved. Free and emulsified water cause the most damage so a good rule of thumb is to keep moisture levels below the saturation point so that all the water is in the dissolved state. For typical mineral-based industrial oils, this is typically 200-300 ppm.

The most effective way of achieving this is to use a vacuum dehydration unit. These systems are capable of removing free and emulsified water as well as up to 70-80% of the dissolved water. For a typical hydraulic fluid, this can mean water levels as low as 30-50 PPM (0.003-0.005%). Alternatively, many companies are reporting success with vapor extraction devices mounting on tank tops. Some of these devices work similar to air conditioners in removing humid air from tank headspaces.

For more information about vacuum dehydrators go to:

http://www.lube-tips.com/links/water1.html

Today's Tip

• Do not use succinic acid type R&O fluids in ammonia refrigeration systems. Ammonia leaking past the seal will react to form ammonia succinate, a sludge like material that could cause valve sticking and premature failure.

Tip submitted by John Cannella, American Refining Group

Book Bits
"An additive is a compound that enhances some property of, or imparts some new property to, the base fluid. In this way, a base stock that cannot meet operational requirements of a tribological fluid system can be modified through additives. In some hydraulic fluid formulations, the additive volume may constitute as much as 20 percent of the final composition. The more important types of additives include anti-oxidants, anti-wear additives, corrosion inhibitors, viscosity index improvers, and foam suppressants.

Antioxidants prolong the induction period of a base oil in the presence of oxidizing conditions and catalyst metals at elevated temperatures. The additive is consumed and degradation products increase not only with increasing and sustained temperature, but also with increases in mechanical agitation or turbulence and contamination -- air, water, metallic particles, and dust."

Q & A
How To Determine if Wrong Oil is Added
“We suspect that a small amount of an EHC phosphate ester fluid was added to a reservoir containing a PAO synthetic. What is the best way to figure out if this has in fact happened?”

For oils that have wildly different base stock chemistry, the simplest method is usually FTIR (Fourier Transform Infra Red Spectroscopy). FTIR looks for what are called functional groups in the oil sample. These functional groups act as molecular fingerprints to identify different components in the oil, as well as common contaminants such as water, fuel and glycol.

In the case of phosphate ester contamination of a PAO, you would be looking for a peak in the FTIR spectrum around 1700-1800 wavenumber corresponding the phosphate functional group. Since this functional group will not be present in the PAO based oil, any signs of a peak in this region may suggest cross contamination. By comparing the spectra of a new sample of the PAO based oil, a new sample of the EHC fluid and the suspected blend, evidence of cross contamination should be fairly easy to recognize.

Most oil commercial oil analysis laboratories should be able to conduct this test for you.

Today's Tip

The benefit of thinner fibers in a filter is that there are more pores per square inch which allows higher dirt capacity and lower pressure drop.

Book Bits
According to a recent study, Canadian industry is needlessly wasting millions of dollars by ignoring problems related to friction and wear.

It seems Canadian industry could be saving itself well over $5 billion annually. How? By paying a little more attention to problems related to friction, lubrication, and wear. According to the study conducted by the National Research Council's Associate Committee on Tribology, Canada spends over $5 billion annually on problems of friction and wear that have been ignored, or unresolved. It seems ironic that in our age of space travel and high technology, much of industry does not understand the relationship between friction, wear, and the proper selection and application of lubricants.

Q & A
Oil Oxidation and Remaining Useful Life
"I know that both acid number and RPVOT tests are used to determine oil oxidation. What is the difference between the two?"

Strictly speaking, the RPVOT test doesn't measure oil oxidation but rather the oils resistance to oxidation. The test works by stressing an oil with heat, oxygen, water and a metal catalyst and measuring how long an oil can resist these oxidation forcing factors. The test is used to determine the change in oxidation resistance between new oil and in-service oil.

Acid number on the other hand can be used to determine how oxidized an oil has already become. The test relies on the fact that as an oil oxidizes, it forms carboxylic acids that increase the oils acid number. By comparing the acid number of a used oil sample, with a new oil reference sample, the degree of oxidation can be gauged.

Depending on the circumstances, an oil may have less than 25% remaining resistance to oxidation as determined by the RPVOT test, but may only show a difference in acid number from new of 10-20%.

Today's Tip

Overfilling a gearbox sump can be just as damaging as under- filling. Overfilling may cause air entrainment and foam, overheated oil and leakage due to overflow. Over time oxidation may occur due to increased temperatures and exposure to air.

Book Bits

Knowing the potential and probable sources of contaminant helps to establish an effective exclusion program. In reality, three fundamental modes contribute to contamination:Injected by people- implanted during manufacturing or induced in the field during maintenance, repair, or overhaul operations.Generated by the system - created tribologically, chemically, or by desorption.Ingested by the machine - introduced by inhalation of dust, air, and water; encroachment of energy; and migration of microbes from the environment.