What is Spiral Wound Gasket?
A spiral wound gasket consists of a V-shaped / W shaped stainless steel strip that is wound into a spiral and non-metallic tape which separates the metal layers. And the non-metallic tape gives a good resilience and sealability. That’s why we call these type gaskets as spiral wound gasket.
Usually, a spiral wound gasket has three parts:
- Outer ring: It’s also called a centering ring or guide ring which is made of carbon steel or other stainless steel. The outer ring is for fixing the gasket into a bolted flange joint.
- Inner ring: It’s made of stainless steel and always the same material with the winding. And the inner ring prevents windings from bulking inside the pipes, reduces the turbulent flow of process fluids and minimizes erosion at flange faces.
- Sealing element: It provides scalability and prevents leakages while the gaskets are in use.
Its inner and outer diameters are reinforced with several layers of the metal strip without non-metallic tape, in this way it can provide greater stability and better compression and sealing function.
When should we consider using a spiral wound gasket?
When a flat gasket cannot provide a better seal over a long time, or there’s high-temperature and high-pressure conditions and corrosive media, or the flanges are out of parallel and the gap between them varies or the gap is smaller and needs material to be compressed more, it’s time to consider a spiral wound gasket.
Why we need a spiral wound gasket?
The spiral wound gasket works well in high temperature and high-pressure environment, it can adjust for temperature changes, shock, and vibration. With compressibility and recovery, spiral wound gaskets are the best semi-metallic gasket for most flanges. They can be used in pipes, heat exchangers and even sometimes take favor over Ring Joint Gasket for high-pressure flanges.
Where do we use a spiral wound gasket?
The spiral wound gasket is always used under the high/low temperature and high/low-pressure conditions, and also used in metal-to-metal joints and have a good tolerance for flange surface finish irregularities. The spiral wounds are used to prevent any leakage of toxic fluids or corrosive media in the petrochemical industry and similar industries.
Can a spiral wound gasket be re-used?
It is not recommended to re-use a spiral wound gasket. As when a spiral wound gasket is underuse, the flange load permanently compresses the sealing element of the gasket, over time, high temperature, high pressure and the huge amount of liquids may destroy the overall structure of this part and second use of the gasket will often lead to leakage.
What is the thickness and compression of a spiral wound gasket?
According to standard, there are two thicknesses (1/8”/ 3.2mm and 3/16”/4.5mm) suitable for most applications. Compressibility and recovery make the gasket the best metallic gasket for most flanges, It’s critical to know the compression. For 1/8” thickness gaskets, compression to a thickness of 0.1000” to 0.005” is recommended while 0.130” to 0.005” for 3/16” thickness gaskets.
What are the types of spiral wound gasket?
Usually, there are four types of spiral wound gasket:
- Style CG: It is a spiral wound gasket with only an outer ring/center ring. The outer ring will center the gasket on the flange face and prevent the gasket blow-out and acts as a compression stop. This type of sealing gaskets is suitable for flat face and raised face flanges.
- Style CGI: It is a gasket with the inner and outer ring or CG type with an inner ring. Besides the advantages of CG type spiral wound gaskets, the internal ring can work as a barrier to prevent flange erosion and also act as a compression stop. It is suitable for flat face and raised face flanges.
- Style R: It is a basic type of spiral wound gasket without inner ring and outer ring and used for tongue and groove, male and female type joint of flanges.
- Style RIR: It is a gasket with only an inner ring. The inner ring prevents the accumulation of solids and works as an additional compression stop. It is suitable for male and female flanges.