GASKET DEFINITION

Gaskets are widely used products for pipelines and piping systems: flange gaskets create a static seal between the faces of the two flanges of a flanged connection. Flange gaskets, regardless their manufacturing material and type, fill the spaces and the irregularities existing on the faces of the mated flanges when they are bolted and tightened together. Gaskets generate a very strong seal that prevents fluids and gases from leaking out of the flanged connection. The installation of gaskets between flanges is a mandatory requirement, i.e. it is not possible and safe to tighten flanges without using gaskets inbetween.

There are several types of flange gaskets. The choice of the correct gasket depends on the following parameters: process features (fluid, temperature, pressure), flanges types / material, dimensions and manufacturing norms. There are three main families of flange gaskets, depending on the material used by manufacturers for their construction:

  • metallic gaskets (ring joint, spiral wound type)
  • semi-metallic gaskets (jacketed gaskets)
  • non-metallic gaskets (flat / soft / die-cut gaskets)

The norms applicable to gaskets are summarized in the table below:

GASKET FLANGE GASKETS NORMS
FLAT ASME B16.5 (gaskets for ASME ANSI B16.5 flanges), ASME B16.21 (gaskets for ASME ANSI B16.47 Series A and MSS SP 44 flanges), BS 3293, ASME B16.21 (gaskets for ASME ANSI B16.47 Series B flanges)
SPIRAL WOUND ASME B16.20 (gaskets for ASME ANSI B16.5 flanges), ASME B16.20 (gaskets for ASME ANSI B16.47 Series A and MSS SP 44 flanges), ASME B16.20 (gaskets for ASME ANSI B16.47 Series B flanges), NF E 29.900-3 (gaskets for ASME ANSI B16.47 Series A flanges)
RING JOINT GASKETS (RTJ) ASME B16.20 (gaskets for ASME ANSI B16.5 flanges), ASME B16.20 (gaskets for ASME ANSI B16.47 Series A and MSS SP 44 flanges), ASME B16.20 (gaskets for ASME ANSI B16.47 Series B flanges), ASME 16.20 (gaskets for API 6A type 6 and 6B flanges.

ASME B 16.20 / ASME B16.21

The key ASME norms related to flange gaskets are:

  • ASME B16.20 metallic gaskets for pipe flanges, i.e. Ring-Joint, Spiral-wound, and Jacketed gaskets: This Standard covers the dimensional tolerances, materials, dimensions and markings of metal ring-joint gaskets, spiral-wound gaskets, and metal-jacketed gaskets. These gaskets are dimensionally suitable for use with flanges described in reference flange standards ASME B16.5, ASME B16.47, API Specification 6A, and ISO 10423. This Standard also covers spiral-wound metal gaskets and metal-jacketed gaskets for use with raised-face (RF) and flat-face (FF) flanges.
     
  • ASME B16.21 non metallic flat gaskets for pipe flanges: This Standard covers types, sizes, materials, dimensions, dimensional tolerances, and markings for nonmetallic flat gaskets. These gaskets are dimensionally suitable for use with flanges described in the referenced flange standards.

 

 

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