Book Bits
From "The Lubricating Grease Guide":

In industrial service, the following may be considered reasonable relubrication intervals for rolling bearings (assuming eight work hours per day):

180°F (82°C), 6 months

220°F (104°C), 3 months

300°F (149°C), 1 month

380°F (193°C), 1 week

460°F (238°C), 1 day

These guidelines assume reasonable-size bearings operating at usual speeds and loads. If speed is high, bearing large or load severe, relubrication intervals could be even shorter. Where service is severe and/or contamination is unavoidable, relubrication is best carried out with a centralized lubrication system, and lubrication intervals may be measured in hours or minutes."

Today's Tip
In circulating systems, the aeration of reservoirs can be reduced substantially if diffusers are used to "ooze" the oil back to tank. Locate the diffuser well below the oil level and select diffuser designs such that flow velocities are reduced to three feet per second (fps).

UK subscribers! Get Oil Analysis I training and take the Level I MLA certification exam. Training takes place on Feb. 26-28 and April 16-18 in Chester, Cheshire. Go to www.noria.co.uk or call 01244-659381.

The SMRP Certifying Organization (SMRPCO) will offer its examination for Certification in Maintenance and Reliability Management at the Practicing Oil Analysis 2002 Conference in Tulsa, OK on March 19-21. For more information about the exam, go to: www.smrpco.org or call SMRPCO at 865-212-0111.

Q & A
Engine Oil Performance Testing
"I have seen a number of lubricant manufacturers refer to the 4-ball wear scar test as an indicator of how well the oil will protect an engine. Other larger companies tend to brush off the results of this test indicating that it isn't representative of actual engine conditions adding that because it is cheap to run, the results aren't worth much. What are your thoughts on this?"

The 4-ball test (ASTM D4172) is often used as a screening test for many different lubricant types that contain antiwear additives or similar base oil properties. Other tribo-mechanical bench tests are often used as well, including the Timken Test (ASTM D2782) and the Pin and V-Block (ASTM D2670). Because engines have different contact geometry, loads, metallurgy and speeds, numerous bench tests and test protocols are needed. It is not uncommon for several oils to be tested using two such methods and to find that the performance rankings between the oils to reverse (no correlation). This is why, among other reasons, Passenger Car Motor Oils and Heavy Duty Oils (diesel crankcase) are tested in actual engines using controlled methods such as ASTM D5533 Sequence IIIE and D5302 Sequence VE.

Jim Fitch, Noria Corporation

Book Bits
From "Machinery Failure Analysis and Troubleshooting":

A rather large number of factors influences lubricating oil degradation and, consequently, pump bearing life. If your centrifugal pumps are equipped with rolling element bearings, there is little doubt that medium viscosity turbine oils (ISO Grade 68) will perform better than the lighter oils originally specified by many pump manufacturers. But by far, the most frequent cause of lube-oil-related failure incidents is water and dirt contamination. With only 20 ppm water in pure mineral oil, bearing surface and rolling element fatigue life is reduced by an incredible 48 percent. Although the fatigue life reduction is less pronounced with inhibited lubricants, there are always compelling reasons to exclude dirt and water from pump bearing housings. Lip seals are a poor choice for centrifugal pump installations demanding high reliability. Face seals represent superior, "hermetic" sealing and should be given serious consideration.

Today's Tip
Create a lube panel located in a convenient location on or near the machine so that hard to reach grease fittings can be centrally located using line extensions. This makes greasing the machine faster and more convenient for the operator or lube tech doing the PM - a "PM that is Made Quick and Easy is a PM that gets done." (Tip submitted by Karl A. Parrott Sr., Total Productive Maintenance Coordinator, Timken Super Precision)

Join us in Baltimore on February 19-21 for our three day training course "Best Practices for Machinery Lubrication". Click here for information.

Q & A
"Can you filter out oxidation and if so what is the best method? I have heard that oxidation is a permanent chemical change and cannot be filtered out."

Figuratively oxidation can be filtered, that is, it can be slowed or reduced through proactive maintenance practices (cleaner, dryer, cooler, etc.).

In reality, oxidation cannot be filtered because oxidation is a chemical aging process driven by catalysts such as high temperature, water, air, metals (in the form of wear debris and contamination) and other contaminants such as fuels and process chemicals. Hence minimizing the ingress of these will reduce or significantly slow the oxidation rate of the oil resulting in longer lubricant life.

However, by-products of oxidation such as acids and fine polar insolubles can be removed by the use of advanced separation technologies such as electrostatic separators, ion-exchange resins, and activated alumina. Additionally, dense absorbent depth-media (compressed cellulose, etc.) such as commonly used on by-pass and off-line filters, can be effective at removing sludge and oxide insolubles. Because oxidation is auto-catalytic, the removal of oxides can help slow further oxidation.

Once these by-products have been scavenged from the oil, the antioxidants will have likely been depleted. In many cases, the antioxidant can be reconstructed on the guidance of your lubricant supplier. A bleed and feed is sometimes recommended to refresh additives. Of course, once the oxidation process reaches a certain advanced stage, the oil's properties may be too severely impaired to continue in service.

Jim Fitch, Noria Corporation

Two Painfully Powerful Tools

They aren't high-tech. Not even state-of-the-art. And you probably won't get that "kid in a candy store" feeling when you first pull them out of your toolbox.

These are reality-check tools. They constantly bring you back to the fundamentals and show you how to build your lubrication program from the ground up. Powerful, but sometimes painful.

The 'repetitive why' is one of the best diagnostic tools available. Here's a simplified version of how it works: "Why did the machine fail?" The bearing failed. "Why did the bearing fail?" The lubricant failed. "Why did the lubricant fail?" It was contaminated. "Why was it contaminated?" The breather filter was inadequate. "Why was the breather filter inadequate?" No training provided for the maintenance staff. You can see that this could go on for quite a while.

The other powerful, but under-utilized tool is the common '80-20 rule.' One way to apply this rule-tool to lubrication is as follows: 80 percent of lubrication-related failures come from 20 percent of the possible causes of failure. Clever readers already know that this means keeping contaminants such as particle, moisture, heat and air from distressing the oil. They typically account for around 80 percent of all lubricant- related failures.

These are two basic tools that dig for basic answers that can produce remarkable results. Make sure you keep these tools handy and pull them out often.

Mike Ramsey
mramsey@noria.com

Book Bits
From "Synthetic Lubricants and High-Performance Functional Fluids":

Automotive synthetic base stocks (PAO and ester) exhibit improved high temperature properties versus petroleum oils of comparable viscosity. These improvements are characterized by viscosity retention at high temperature (due to higher viscosity index), higher flash points and lower volatility.

Higher viscosity index base stocks, whether petroleum or synthetic, will exhibit lower viscosity loss upon temperature increase. This property will translate into higher film strength for hydrodynamic and elastohydrodynamic lubrication in an engine. At high temperatures, this set of characteristics will mean improved protection for bearings (sleeve, ball or needle) and rotating seals.

Today's Tip
When you make a new hydraulic hose cut from a roll of bulk hose, install the new fittings and then flush the hose with a light-weight oil in order to wash all of the shavings out of the hose. Otherwise you will introduce rubber and metal braid shavings into the hydraulic system. (Tip submitted by Gary Valadez, Hampel Oil. Thanks Gary!)

In regard to the tip above, we'd like to add: When flushing a hose with oil, make sure the flushing oil is compatible with the hydraulic fluid used and that the velocity of the flush is about twice that produced by the system's hydraulic pump. Another way to clean hydraulic hoses is to use pneumatic projectiles (sponges) that push through the hose to clean out debris.

Q & A
"Should I specify a particle cleanliness requirement in my oil procurement contract? (We have visual inspection for contamination, but no ISO cleanliness code.) If I did specify cleanliness, would the oil distributors/suppliers bid? -- Vickie Trojan, Lubrication Engineer, Constellation Energy

I like to see delivered cleanliness of 18/16/13 or better, per ISO 4406 (99). If the oil is going into an application that demands superclean oil, it will still need to be pre-filtered before entering the machine. The proposed cleanliness is a happy medium that gives you relatively clean oil and provides some tangible evidence that the oil has been well-handled in the logistical chain from the refinery, to the blending house, on to the distributor and finally to your facility for use.

In my experience, bulk oil deliveries must be filtered out of the tanker to achieve this goal. For drum oil deliveries, the oil should be filtered at the time of filling the drum.

The drums also play a role. In my experience, reconditioned steel drums will miss the cleanliness objective most of the time. New steel drums will miss the goal some of the time and new one-shot plastic containers will hit it most of the time, assuming proper management at the time they are filled.

Need I mention that you get what you pay for? It costs money to deliver clean oil. Filters, new steel drums and one-shot plastic drums and containers cost money - you should plan on paying a little extra. It is unfair to an oil supplier to slip this into your requirements after the contract has been negotiated. Get these issues out on the table.

Drew Troyer, Noria Corporation