Spiral Wound Gasket Materials

Metallic Strip

The metallic strip that holds the filler has a standardized thickness of 0.008 in. (0.20 mm) and the width according to the gasket thickness. The most common materials used for metallic strips are:

Stainless steel AISI 304 and 304L: the most widely used material. Good corrosion resistance and is affordable.

Stainless AISI 316 and 316L for chemical service.

Stainless steel AISI 321 for high temperature service.

Other usable materials can include: Monel, Nickle 200, Inconel, and Titanium.

Filler

The filler material is what provides gasket sealability. The edge of the filler should be flush or above the edge of the metal strip, never below. Here are some materials used as filler:

Flexible Graphite: This material is great for spiral wound gaskets due to its low permeability, thermal stability, low creep and chemical resistance. In neutral or reducing

services it can be used from 330EF (-200EC) up to 5430EF (3000EC). When used in

oxidizing services at a temperature above 660EF (450EC) it is necessary to encapsulate the gasket to protect it from direct contact with the oxidizing medium. Flexible Graphite can be used in oxygen, in any concentration, up to 930EF (500EC) as long as the sealing element is completely enclosed between the flanges. Its operational temperature limit for steam and hydrocarbons rich in hydrogen is 1200EF (650EC) . Flue gas service should be avoided at this temperature. Flexible graphite is also rated as fire-safe by The Pressure Vessel Research Comittee (PVRC).

PTFE: This material is used when higher chemical resistance is needed. PTFE filled gaskets should be confined in a grooved flange or with an inner reinforcing ring to increase its mechanical resistance.

Mica-Graphite: A chlorite, graphite and cellulose based Beater Addition paper with an NBR latex binder. This material is used as a subsitute for Asbestos paper because it has similar sealability and overall performance up to 450EF (232EC). In higher temperatures it degrades. NOT RECOMMENDED for use in refineries, chemical plants or any service with flammable media where a fire-safe gasket is required.

Guide Ring

Since it doesn't come into contact with the fluid being sealed, the guide ring is usually made of carbon steel AISI 1010/1020. When used in highly aggressive services the guide ring can be made of the same material as the Metallic Strip. Carbon steel guide rings are electro-plated or painted to avoid corrosion.

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