In This Issue:

• Up Front: Don't Forget the Simple Things!

• Book Bits: Use Synthetic Lubricants for Better Flash Point Properties

• Today's Tip: New Grease Gun Caution

• Q & A: Upside-down Viscosity
  

Up Front

Don't Forget the Simple Things!

It is surprising how often simple methods of controlling oil contamination are overlooked. Companies may commit considerable resources to solve fluid contamination problems with additional filtration equipment, while little or no effort is made to determine the source of the contamination.

A case in point is turbine lube systems with vapor extractors. These systems maintain a continuous, partial vacuum on the lube oil reservoir to extract smoke and oily vapors from the system. It is common when working on dirty systems to find the gaskets on manways and reservoir covers to be severely cracked, or sometimes missing.

A failed or missing gasket may allow hundreds of cubic feet per day of dirty, moist air to be drawn into the lube system. This condition will negate even the best efforts at controlling oil contamination problems.

Keeping oil clean is a must to maintain a competitive advantage in today's market. Sometimes, by not forgetting the all-too- obvious "simple things", you can reap great rewards. Check your gaskets! (Submitted by Bob Picek, Lormar Reclamation Service. Thanks Bob!)

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Book Bits

Use Synthetics for Better Flash Point Properties

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

Addition of synthetic components to petroleum-based engine oils will do little to improve the flash point. Full synthetic engine oils usually exhibit the best flash point properties.

More information about "Synthetic Lubricants and High-Performance Functional Fluids".

Today's Tip

• Before installing grease into a new grease gun, consider disassembling the gun and cleaning it thoroughly. I have found metal shavings numerous times in different brands of new grease guns. The metal shavings appear to be from the manufacturing process of the grease gun. (Submitted by John Flynn, machine health analyst, R J Reynolds Tobacco Co. Thanks John!)

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Q & A

Upside-down Viscosity

"I've read that a high viscosity index (VI) is characteristic of a good lubricant, but in another publication I read about a synthetic lubricant with a negative VI. Does this mean that the lubricant increases its viscosity with the temperature?"

For liquid lubricants, oil viscosity decreases as temperature increases. Lubricants subjected to a wide range of operating and ambient temperatures require a lubricant that exhibits the lower change on its viscosity with variations in temperature. According to the definition in ASTM D2270, the Viscosity Index is an arbitrary number used to characterize the variation of kinematic viscosity of a petroleum product with temperature. For oils with similar kinematic viscosity, the higher the VI, the smaller the effect of temperature on its viscosity.

To better understand VI, we need to review how it was developed by Dean and Davis in the 1920s:

VI is a means of classifying the viscosity vs. temperature behavior of oils, on the basics of two reference oils selected to represent two extremes of behavior:

The reference oil for high (H) VI was assigned a VI of 100. The oil used was a paraffinic base oil from Pennsylvania crudes, which at that time were considered to display the best viscosity vs. temperature characteristics.

The reference oil for Low (L) VI was assigned a VI of 0 and was a naphthenic base oil from the coastal region of Gulf of Mexico, which shows a very poor viscosity vs. temperature relationship.

Using this simple approach, lubricants that exhibit less change in viscosity (with respect to temperature) than the reference oil H, will have a VI greater than 100. Lubricants having viscosity change (with respect to temperature) greater than the reference oil L, will have a negative VI. This means that a lubricant with a -15 VI will exhibit change in viscosity with respect to temperature more so than the naphthenic reference oil.

Gerardo Trujillo, Director de Servicios Tecnicos, Noria Latin America

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