|
|
||||||||||||||||||
|
|
||||||||||||||||||
| The service life of a power transmission belt is closely related to its operating temperature. Excessive heat, from any source, is the single biggest detriment to belt life. Heat is generated both internally and externally when a belt is in motion. Internal heat is generated by the constant flexing, or hystersis, of the components. External heat is created by relative slip and creep between belt and pulley. | ||||||||||||||||||
|
High ambient temperatures increase both internal and external belt temperatures.
A common rule-of-thumb is that for every 35°F(19°C) increase in
ambient temperature above 85°F(29°C), belt life will be reduced
by at least one-half. For example, a belt operating in an ambient temperature
of 120°F(49°C) will run only half the life of the same belt at
the same conditions of load and tension running in an ambient temperature
of 85°F(29°C). |
||||||||||||||||||
|
|
||||||||||||||||||
| The most visible sign of temperature problems are shiny glazed belt sidewalls due to the material becoming hard and brittle. This will also lead to visible stress cracks, especially in the lower portions of the belt section. Belts which have reached this state should be replaced. If you have repeated failures of this type consider replacing the drive with a more temperature resistant design. | ||||||||||||||||||
| Most belt companies test their products and establish horsepower ratings for industrial belts at approximately 85°F(29°C) ambient temperature. Normal expected life at the rated horsepower, properly tensioned, will be approximately 25,000 hours when running in an atmosphere at 85°F(29°C). When the belt is run at the same horsepower load and tension but at higher ambient temperatures that belt life will be reduced in accordance with the general rule-of-thumb above. | ||||||||||||||||||
| There is no way to establish precise temperature ratings for a belt. Belts which run in ambient temperatures above 85°F(29°C) will experience reduced service life. When belts are subjected to ambient temperatures in excess of 160°F(71°C) the type of belt and proper maintenance are critical to achieving even minimal service life. In general, you will experience longer service life at elevated temperatures with belts that are more flexible. These belts will tend to generate less internal heat due to flexing and keep belt operating temperatures to a minimum. Examples of more flexible belts are cog v-belts, V-rib belts, and synchronous belts. Belts made of polyurethane should be avoided on high temperature drives; this material tends to soften at elevated temperatures. | ||||||||||||||||||
| Additional methods for improving service life on drives with high temperature problems include: | ||||||||||||||||||
|
||||||||||||||||||
|
||||||||||||||||||
|
||||||||||||||||||
|
This article is provided courtesy of PTDA. |
||||||||||||||||||
|
|
||||||||||||||||||
|
