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In This Issue:

• Up Front: Lubricants Have Come a Long Way

• Book Bits: What Causes Seal Leakage?

• Today's Tip: Getting a Handle on Drums

• Q & A: Comparable vs. Compatible

Up Front

Lubricants Have Come a Long Way

The phrase "all lubricants are the same" is a common misconception among untrained people. It ignores the advances made in the lubricants industry in the last 15 years. The technologies of refining crude oil to produce lubricant base stocks and the development of new additives would be difficult for past generations to imagine.

A few years ago, the recommended oil change interval for an automotive gasoline engine was every 2,500 miles. Newer automotive manuals call for 7,500 miles or more using a mineral oil. The new engine doesn't run cooler. On the contrary, it runs at greater temperatures, higher rpm's, smaller tolerances, etc. New lubricants are lower viscosity (some use SAE 5W20) but they protect much better than a straight SAE 40 from 10 years ago.

I remember when an engine had to be sent for an overhaul after just 100,000 miles. Now, it is possible to find gasoline engines with 400,000 miles without major repair. New lubricants protect the engine better.

Talk to your lubricants supplier, and let them explain the new design/performance characteristics of their products and analyze the possibility of putting these technological advances in lubrication to work in your machinery.

Gerardo Trujillo, Noria Latin America

Book Bits

What Causes Seal Leakage?

From "The Practical Handbook of Machinery Lubrication"

Cost cutting by machine design engineers, incomplete commissioning and plant start-up procedures, and inadequate equipment condition monitoring and maintenance practices are the major reasons for initial seal failure and fluid leakage.

Once a seal has failed, causing fluid leakage, the problem is perpetuated by bad purchasing department policies of purchasing and restocking low-quality (read less expensive), or incorrect seals, or by careless installation practices used during replacement procedures.

The subsequent leaks, though considered excessive, continue. Soon, plant operating and maintenance personnel accept the leakage as normal.

The lack of attention to a few basic details costs millions of dollars annually in external fluid wastage, unnecessary maintenance downtime and environmental damage.

More information about the "The Practical Handbook of Machinery Lubrication"

Today's Tip

Getting a Handle on Drums

• Proper handling of drums is important. Drums aren't designed to be bounced or dropped. Full drums weigh approximately 450 pounds, while empty drums weigh around 36 to 38 pounds. A pail of oil weighs about 40 pounds.

Each tip published will earn the sender $50. Submit your tip.

Q & A

Comparable vs. Compatible

(Actual brand names removed)

"The articulated joints on our buses use (Brand A) hydraulic fluid. Our engineering department wants us to use (Brand B) aviation hydraulic fluid. Our bus supplier says the Brand A is the only approved hydraulic fluid for our system. We purchase the Brand A fluid in our area. Is the aviation fluid actually better, as stated by our engineering department? We won't have to service these units for about another six months, but we must perform some repairs which require small amounts of hydraulic fluids be added, Will the different fluids cause problems?"

These two products, Brand A and Brand B aviation hydraulic fluid, are comparable, according to the manufacturers. The only distinct difference between the two is base oil type. The Brand B product has a PAO synthetic base oil while the Brand A product utilizes a mineral or petroleum base oil.

There are inherent advantages to the PAO base oil, such as viscosity index and oxidative stability, but more important are the properties of the finished lubricant. Sufficient to say, both products should perform adequately in the application for which they were intended.

Are the two products compatible? Possibly. Unfortunately, neither manufacturer has a compatibility study for these products on file. Brand B recommends that the system be drained and flushed before addition of the new product while Brand A recommends at least draining the system before adding the new product.

When changing lubricants, be it type or brand, the primary recommendation is to drain and flush the system completely. Even if lubricants are deemed to be comparable, they are not necessarily compatible.

There are occasions where it is impractical or unnecessary to perform a drain and flush. In such cases, if the appropriate steps are followed, the conversion can often be accomplished without draining the system.

Compatible products are generally similar in base oil type and additive chemistry. Some products have acidic properties while others are alkaline. If two such products are mixed, the acidic and alkaline additives can react to form insoluble products with a grease-like consistency that will obviously compromise lubricant performance. Mixtures of different base oils, especially synthetics, can react with one another and change the physical and chemical properties of the lubricant.

If it is determined that a drain and flush is impractical, the first step should be to contact the lubricant suppliers or manufacturers. For common lubricant types, the lubricant manufacturers have often already performed studies to determine product compatibility. If no study is available, the lubricant manufacturer may perform one provided sufficient economic justification exists. One should keep in mind that it is possible for two lubricants to appear compatible in the laboratory but prove otherwise in service due to contaminants or service conditions. If the decision is made to mix the lubricants without draining and flushing the system, it should be closely monitored using oil analysis to ensure product performance.

For more information on compatibility testing see the following articles:

Managing the Risk of Mixing Lubricating Oils

Testing Lubricants for Compatibility

Jarrod Potteiger, Technical Consultant, Noria Corporation

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