Prevent NARs With Parker Sure Torque Assembly And Gaskets

Reduce NARs With The Parker Sure Torque Assembly And Gaskets

When shipped by rail, many liquids are shipped in tankers, where the contents are accessed via a hinge and bolted cover known as a manway. Having a dependable O-ring seal between the tank and the cover is important to prevent leakage and contamination. When hazardous materials are being shipped in the tanks, which is the case with 1.5 million tanker shipments each year, the risk of seal failure means the release of possibly toxic chemicals into the air. Since ethanol and ethanol related products comprise 330,000 tanker shipments, the risks are particularly high with this product. As reported by The Renewable Fuels Association, between 2007-2012, there were over 730 reported Non-Accident Releases (NARs), with nearly a third of these traced back to a problem with a hinge and bolted manway.

A manway consists of a hinged cover that closes against the nozzle of the tank with an O-ring gasket. The assembly is held in a closed position with a series of eyebolts attached to the nozzle that protrude above the cover and are fastened in place with a washer and nut. This assembly is intended to remain in place throughout shipment, but is subject to fail in certain conditions:

  • The gasket has imperfections that prevent proper sealing.
  • There is not sufficient pressure on the cover, nozzle, or gasket surfaces based on both the temperature range and the internal pressure on the joints.
  • As a result of corrosion, self-loosening, galling or cold welding, or stress corrosion cracking hardware, the eyebolt fails.
  • Either the eyebolt or the gasket stretches or relaxes when temperature and pressure change.
  • The gasket, which should be replaced each time the manway is opened, is reused.

In most cases, the gasket itself is effective when properly replaced and when the bolts are tightened or torqued in the way specified by the Association of American Railroads. The approved method is to tighten them three times with a calibrated torque wrench in a star pattern. However, technicians often use the impact wrenches and do not check old tension requirements, which results in uneven bolt torque, poorly seeded gaskets and lids, and failure of the unit to prevent NARs. Even if the technician properly installs the gasket, tanks can lose up to 60% of their pre-load torque.

While supplying high quality gaskets to the industry, Parker O-rings supplied by Performance Seal avoid many of these problems due to the Sure Torque™ system which preserves the gasket and makes installation failsafe.

Why is The Parker Sure Torque™ Assembly So Effective?

In most installations, the gasket seated on the manway nozzle interfaces with the hinged lid. This makes factors such as gasket placement, worn gaskets, and gasket deterioration more likely. The Parker product protects the gasket so that the bolt does not catch on the gasket and the closure is metal to metal to metal, as the cover and nozzle are closed via the bolt. The technique reduces 52% of NARs, as the bolts, which can now be tightened with an approved impact wrench, retain the proper torque and loses less than 1% pressure. In addition, gaskets can now be used up to 30 times, rather than replacing them frequently with each torque - a cost saver that also preserves the integrity of the material in the tank.

Since the Parker assembly is compatible with most nozzles, tank owners can economically convert an entire fleet of tanks, which will result in reducing or eliminating the major causes of manway-related NARs: loose bolts, gasket misalignment, gasket deterioration, or missing gaskets. For information about the Parker Sure Torque™ Assembly and the Parker Manway Nozzle Gasket, look to Performance Seals.Click here for a catalog or contact us via our website.

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