25 June, 2024

PG-ML – a gasket sheet made of stainless steel and flexible graphite

23 October, 2019

Expanded graphite is the most commonly used sealing material for high temperature applications. It is employed in the construction of a wide variety of styles including flat sheet gaskets, semi-metallic gaskets such as spiral wound, compressed valve packings and die pressed rings; it is the sealing material of choice for the refining, petrochemical and power industries.

[subhead] Excellent chemical and thermal resistance

Expanded graphite – natural graphite flake that has been expanded and then compressed – is a material that combines the inherent temperature and chemical stability of graphite with an ability to compress and conform, properties that result from the expansion process. It is material that is claimed to have excellent chemical and thermal resistance, very good load retention properties and outstanding conformability to the irregularities in a flange surface.

But when manufactured as sheet material, a reinforcement material is required to improve handleability. The reinforcement can be either metal foil, which is bound to the graphite with an adhesive, or tanged, which a perforated metal sheet that is mechanically bond to the graphite layers. While both forms are suitable for general industrial use, they cope less well in arduous conditions of high temperature and pressure; adhesives tend to weaken load retention at elevated temperatures and the tanged reinforcement can increase leakage. The user is then limited to semi-metallic gaskets for these applications which can be expensive and are difficult to fabricate in complex shapes or in thin sections.

[subhead] Improved handling and scratch resistance

PG-ML is a gasket sheet made of several layers of stainless steel and high oxidation-resistant flexible graphite. The layers of graphite and stainless steel sheets are bonded to each other using a specialised adhesive free process and the outer layers are impregnated to reduce leakage and improves handling. The result is a product which is able to operate in conditions well beyond the scope of the traditional reinforced graphite gaskets. It can accommodate pressures of up to 250 bar and operating temperatures of between – 250degC to 500degC and has improved handling and scratch resistance due to the special impregnation.

PG-ML finds applications in tongue and groove flanges, heat exchangers, sight glasses and O.E.M. equipment. It is also suitable for common pipework and vessel designs. Its properties benefit the chemical, refining and nuclear industries, as well as OEMs such as pump, valve and turbocharger application.


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