COMPLIANCE INFO 2004 - 2006 - Laserfiche WebLink

Home Browse Search

AIVLJanuary 1991.: nualoypdater®U AWRON INTERNATIONAL Joie Fotkers, technical director for Ameron Fiberglass Pipe Division -Americas, addresses questions and concerns about 0 - rings in Dualoy 3000/LCX. The design of the new Dualoy 3000/LCX containment joint uses elastomeric 0 -ring gaskets. This article addresses the use and design of the 0 -ring to enhance under- standing of the LCX product. Material The material in the 0 -rings of the LCX joints is a fuel -resistant nitrile rubber. It is a Recognized Component by Underwriters Laboratories Inc. (UL). The 0 -ring is included in our UL Listing for the product. Recognized Component and Listing are very specific terms in the UL vocabulary. Their use indi- cates that the material has under- gone intensive testing in the fuel lab at UL and that the parts have passed all requirements imposed by UL for use in the intended ser- vice. The fuels in which the material has been tested include all cur- rent commercial fuel, as well as' additives, including MTBE (methyl-tertiarybutyl ether). Accelerated aging tests performed by UL demonstrate that no deteri- oration or breakdown of the material will occur. Application 0 -rings are typically placed in grooves which are dimensioned for either a static seal or a dynam- ic seal. A static seal is generally a tight fit, and allows little space for the 0 -ring. Dynamic seals are those in which a gasket seals against a moving part and is expected to seal against the part throughout its range of motion and through multiple cycles of movement. A dynamic seal is typi- cally a looser fit to allow this movement to happen without excessive resistance. The seal in the LCX joint is a stat- ic seal. There will be no move- ment or wear in the LCX 0 -ring. A common experience with 0 - rings is in water faucets. Nuisance leaks in these fixtures are repaired by replacing a worn-out 0 -ring. This may cause some concern when seeing 0 -rings in the ground at fuel sites. The.faucet gasket is a dynamic seal and is totally different than the static situation in the LCX joint. Ameron has used an 0 -ring joint in oilfield applications for 25 years (since 1972). During this period there has not been a single failure attributed to the degrada- tion, wear or any other cause associated with the 0 -ring. Design The large 0 -ring in the female end of the fitting of the LCX joint is slightly larger in outside diame- ter than the inside diameter of the part into which it fits. This puts the 0 -ring in a slight amount of circumferential com- pression. This is important for that period of time from when the fitting is made to before it is put into service. If the seal were in tension during this time, the compound could see some embrittlement and show some surface cracking . The fact that the material is in compression helps to preserve the seal surface. The smaller 0 -ring is in a neutral state as it is in (contlnued on page 2) 0 -ring suis in ntow 3000/L.CX G