Many industrial plant sites have assembly torque tables for standard ASME B16.5 flanges as part of their internal procedures for bolted flanged joints. It is common for end-users to change gasket materials and gasket designs to reduce costs and/or improve reliability or as processes evolve and change. As environmental awareness and regulations continue to increase, it is important to understand the different levels of tightness that can be achieved from various gasket technologies. Gaskets do not seal equally at the same assembly load. All bolted flanged joints sealed with a gasket have some emissions rate, albeit some vanishingly small on very tight joints.

The tightness parameter has an inverse relation to leakage; the tighter a joint, the less leakage it has. The less leakage, the less emissions result. Where emissions monitoring is intense, tighter gasket technologies are preferred. These tighter technologies are often more expensive. Where emissions are less a concern, river water as an example, more economical gasket selections are preferred. This paper explores gasket tightness performance of a number of materials and construction types common for industrial and power use. Material classes that will be explored include compressed fiber, polytetrafluorethylene (PTFE), flexible graphite (FG), and flexible vermiculite (FV). Construction types that will be explored include sheet materials, composites with metal inserts (flat or corrugated), grooved metal with soft facings (“kammprofile”), and spiral wound gaskets.

For the purposes of comparison, an example assembly torque table will be used. The table includes ASME B16.5 Class 150 flanges, sizes ½” through 24”, using A105 carbon steel flanges and high strength A193 B7 fasteners. With a better understanding of the general capability of a gasket class — the end user can more quickly select gasket materials and constructions suitable for a particular application. This work follows and expands earlier work done with more limited flange sizes. [1]

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