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Written by Brent Elliott
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Oils and chemicals can damage belts
When oil or chemicals come in contact with a belt, they reduce the life span and operational characteristics. It then gets a bit more complicated. The concentration of the chemical or oil involved, the length and type of exposure, the belt type used and environmental conditions, such as heat and humidity, all contribute to the degree and speed of performance deterioration.
Two effects may be noted when belts are exposed to oil and/or chemicals. The most obvious is a swelling of the belt's cross section, so that it no longer fits the sheave or pulley groove properly. Less apparent at first glance is the deterioration of other physical properties, including adhesion between the belt components. If the degree of swelling, and/or loss of physical properties are significant, the effective use and life of the belt will be substantially shortened.
There are a large variety of chemicals like oils, acids and solvents present in different environments. No single synthetic rubber is resistant to all of these. Some compounds may be excellent in resisting one chemical, but will react poorly to another, and then be only adequate for still another.
Because of this varied reaction, all stock belts offered by members of the Rubber Manufacturers Association (RMA) are constructed to be reasonably oil and chemical-resistant. The nature of the compounds and/or belt construction may minimize swelling and deterioration, so that occasional splattering by oil and grease doesn't usually adversely affect standard belts.
There are a great many chemicals, however, such as gasoline, which will swell rubber, or extract ingredients from the belt-rubber compounds. This may cause brittleness, cracking or swelling of the belt, or other conditions that result in a deterioration of performance.
In this article, it's not practical to categorize all of the belt-destroying chemicals and materials without getting involved in the specific chemistry of each one. The problem is further complicated by the proprietary formulations of petroleum and chemicals by their manufacturers. Often times, the only real test of satisfactory belt performance versus any specific liquid is a lengthy and careful lab study.
Belt compounds themselves also vary from manufacturer to manufacturer, although usually, those that are specified as oil-resistant will withstand moderate attack from most common oils and solvents. If the drive is subjected to a considerable amount of oil and grease on the belt, the problem may become less of a chemical issue and move into being a physical one as well.
For example, a large accumulation of oil and grease on a V-belt may render the belt useless due to loss of friction. So, it's assumed that where conditions include a large presence of oil, a V-belt is simply not the right choice. Since synchronous belts aren't substantially affected by the loss of friction, they're capable of operation under these conditions and are the better choice. In fact, depending on the drive and the nature of the oil, it may even be possible to use a synchronous belt while it's submerged in oil.
The following general guidelines might be of use for prolonging the life of any belt-drive system that will be subjected to a chemical environment:
1. Prevent as much accumulation of contaminants on the belt and system components as possible;
2. If the belts are to be subjected to only occasional contact with contamination, a standard construction 'V', or synchronous belt can be used; and
3. If you want the belts to give long, trouble-free operation on an industrial drive and you know they will come into contact with oil, chemicals or solvents, consult manufacturers for the recommendations on which type of belt to use.
Brent Elliott is senior applications engineer with Springfield, MO-based Carlisle Power Transmission. For more information, visit www.carlislebelts.com.
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