Repair And Fix it

There are several different reasons for why O-rings can fail. Checking for damage is relatively easy. In most cases it is easy to tell that the O-ring does not look normal, but when you identify the exact characteristics, you will know what the problem is and will be able to take steps to fix it. The following four patterns are the most commonly found with O-rings and tells much about the solutions to fix them.

Instructions

1

Examine the O-ring by checking for compression set. This is when the seal lines have become deformed and compressed to the surface and look melted and misshapen. If this has not occurred, continue to the other steps until you can identify the problem. However if it has, it means the material of this O-ring was not suitable, or that the operating system temperature needs to be reduced.

2

Look for extrusion and nibbling. Its characteristics are a "torn," ragged look of the O-ring. This occurs in hydraulic rod and piston seals because of high pressure causing clearance gaps which destroy the ring. If this is the case, you may need to decrease clearance, ensure that the O-ring is tolerant of machine fluid, or replace the O-ring with a harder, more durable one.

3

Check for spiral failure if you have not seen the above two patterns. This looks like the O-ring has been twisted. This occurs when the seal becomes caught on one side but but is sliding and rolling on the other side. This can be fixed by improving surface finish, increased lubrication, or replacing the O-ring with a harder one.

4

Inspect for cracks or splits in the O-ring -- these are signs of explosive decompression. This happens when the O-ring has been operating under high pressure gas, which is then reduced quickly leaving gas trapped within the structure of the O-ring, causing ruptures. To avoid this, slow down decompression time, and select a sealant with resistance to decompression. If this is ineffective, replace the O-ring with a metal seal.

5

Examine the O-rings for abrasion.This looks like the O-ring has been scraped. This occurs when a proper surface finish is not being used. Inadequate lubrication is also a reason -- you may want to use internally-lubricated O-rings. You may need to install filters to avoid contamination of fluid.

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.