CHOOSING correct replacement gaskets for tank trailers should be a top priority at wash rack facilities, said Kip Hart of Hart Industries Inc.
“All gaskets are not created equal,” he said at the National Tank Truck Carriers Tank Cleaning and Environmental Council Seminar April 2-3 in New Orleans, Louisiana. He added that a failure from an inappropriate gasket installed by a tank wash could have serious repercussions, including a spill incident that could involve the tank wash in litigation.
“Even with the best hoses and fittings, a load can be jeopardized because the choice of gasket is wrong,” Hart said.
Hart pointed out that several factors determine gasket selection, such as type and temperature of product hauled, chemical resistance, and type of component on which the gasket will be used. Another consideration for gasket choice has arisen with the introduction of alternative fuels to the market that may require certain specifications.
Personnel making gasket selections should become familiar with the various products, especially the materials used in their manufacture. Some may have a high initial cost while others may be more moderate. Despite the costs, however, gasket performance is based on different situations.
Hart pointed out that his suggestions are meant to be a general guide only and reference should always be made to appropriate resources, including fluid resistance publications, for specific recommendations. “Immersion testing is always recommended prior to use,” he said.
Suggestions for hose coupling gaskets:
Santoprene gaskets should be used in all chemical hoses except where another material is specified by the shipper or when Santoprene has an unsuitable rating. When Santoprene is not recommended, the choice can be gaskets made of polytetrafluoroethylene (PTFE) envelope or fluorocarbon elastomer (fkm or vi), whichever is recommended. Buna-N gaskets as a rule should only be used with buna-N (nitrile) hoses and are generally for petroleum products only.
Suggestions for pressure and vacuum vent seats:
Gatron is the most economical choice because the material has improved sealing capacity over PTFE, better chemical resistance than fluorocarbon elastomer, and lower cost than Kalrez. Santoprene also can be used in many applications, but should be scrutinized more closely in those applications.
Applications for QRB seat (donut gasket):
Gatron is recommended because it has improved seating capacity over PTFE and is more cost-competitive than fluorocarbon elastomer. Santoprene is not yet available in 1/2-inch thickness for QRB seat.
QRB gasket (bonnet):
Santoprene and Gatron are the best seals for these applications. They have superior sealing properties (fewer leaks during pressure tests) and can be cleaned and reused (3-4 times life over PTFE envelope gasket).
Clean out gaskets:
Santoprene gaskets should be used whenever possible because of improved cap sealing and better memory. Gatron can be used when chemical compatibility requires. Hart noted that nipple resurfacing can reduce gasket and fusible cap cost significantly.
Dome lid gaskets:
Santoprene gaskets should be used whenever possible because of these advantages: superior sealing properties, can be cleaned and reused, longer life, does not absorb odors like braided packing, and lower cost and low labor cost to install and pressure test trailers.