Thursday, October 3, 2013
Viton O Ring Specifications
Viton, a registered trademark of DuPont, refers to a substance known as an fluoroelastomer that has multiple uses where continual functioning in extreme heat is essential, such as automotive engines. Fuel systems, in order to meet stringent emission requirements, place a burden on the parts in the system, which includes o-rings that must hold their seals. These o-rings are often specifically designed and manufactured with Viton to meet all the demands.
Heat Resistance
O-rings, like other parts in the automobile engine, sustain high temperatures on a continuing basis, and must hold their seal over a long period of time. Viton rings specify resistance to temperatures up to 200 degrees Celsius, or 392 degrees Fahrenheit. According to DuPont, their o-rings display a maximum continuous service temperature of 204 degrees Celsius.
Ability to Hold Seal
Volume change, or swell, denotes movement in the physical nature of the o-ring, caused by the extreme heat of the engine. In measuring the ability to hold a seal and not leak, Viton must be resistant to most swell. According to test results reported in Problem Solving Products, after 100 hours in air at 150 degrees centigrade (a temperature equal to or greater than a typical engine), Viton o-rings retained more than 90 percent of their original sealing force.
Hardness
One specification for o-rings involves the hardness of the substance, which relates to its ability to withstand adverse forces in the engine. A Shore (Durometer) hardness test remains a standard for assessing this specification, with the Shore A scale being used for o-rings. Measurements range from 0 to 100, with the higher the number, the harder the substance. According to Marco Rubber, the following are the results for this specification: ETP o-rings 78, GLT o-rings 75, GFLT 73, B 75 and F 79. To put this item in perspective, SubsTech lists shoe heels as a 70 and shoe soles as an 80.
Tensile Strength and Elongation
According to MatWeb, tensile strength measures the force per unit area (MPa) necessary to break a substance, and tensile elongation measures the percentage increase in length before breaking. For this specification, ETP o-rings measured a tensile strength of 17.9 and an elongation of 145 percent. Other Viton o-rings rated from 13.6 to 17.6, with elongation ranging from 140 to 240 percent.
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