The industry’s most recognisable type of gasket is the spiral wound gasket.
Unique in its appearance and construction, you will typically find this type of gasket in piping systems across several industries as it connects piping together while maintaining performance even in high temperature, high pressure, and chemical applications.
Spiral wound gaskets are renowned for providing an efficient and tight seal at all times, and at SSP, we stock a wide range of gaskets, all offering various sealing solutions suitable for a range of applications.
In this post, we look specifically at the construction of spiral wound gaskets and some of the benefits of this type of sealing solution.
Terminology of spiral wound gaskets
Spiral wound gaskets have been around for many years due to their versatility, flexibility, and practical sealing construction.
They can withstand high pressure and temperature ranges, making them suitable for a range of applications across various industries.
Spiral wound gaskets work when compressed between two surfaces; this compression creates a tight seal, preventing leaks and gaps in applications.
Various filler materials make up the spiral wound gasket, and as a consumer, you have the option of which spiral wound gasket material to choose from, depending on the application in which it is intended to be used.
Filler materials include:
PTFE – polytetrafluoroethylene – suitable for chemical and abrasive applications.
Ceramic – a good electrical insulator, ceramic offers solid resistance to high temperatures.
Non-asbestos – suitable where resistance to chemicals is required, and asbestos cannot be
used.
Mica – a heat-resistant material, making it suitable for high-temperature applications.
To find out more about various gasket types, check out our latest post on gaskets with metal eyelets.
Construction of spiral wound gasket
Over the years, you will notice that the spiral wound gasket has not changed in its appearance or construction by any significant margin.
There have been subtle changes, which we will look at below; however, ultimately, the SWG has and will always consist of the following:
A solid metal outer ring – typically constructed using stainless or carbon steel. The outer material helps to prevent over-compression of the gasket and allows correct positioning in
the application.
An inner ring – supporting the gasket, the inner ring prevents the windings that form the spiral part of the gasket from buckling. The inner ring will also be constructed from whatever material you opt for as the filler.
Winding – typically constructed using stainless steel, alternating strips of metal and soft filler material are wound together to create a spring-like function when compressed.
Filler – enhancing the gasket’s sealing properties, (make sure to choose the filler material compatible with the intended application).
As manufacturers continue striving for higher performance from their seals, some have slightly deviated from the ASME gasket guidelines.
This stray in spiral wound gasket construction has led to the development of low-stress gaskets entering the market.
These low-stress gaskets are constructed using additional graphite within its filler, requiring less torque. This makes these gaskets incredibly enticing since the most common cause of bolted joint failure is a lack of load.
Spiral wound gasket challenges
When we examine low-stress spiral wound gaskets and standard spiral wound gaskets, we understand the following:
Low stress means a softer winding, i.e., a thicker filler strip is used, but the winding has less tension (as fewer strips are required), creating a lower density. This spiral wound gasket manufacturing process produces a softer, looser wound gasket. In addition, the fewer strips used in construction mean that when compression takes place, the compression of the spiral wound gasket is higher.
However, when we look at standard spiral wound gaskets, we see that these gaskets are manufactured with a higher-density winding made up of thin metal strips of soft filler (achieving a tighter winding). These standard spiral wound gaskets meet ASME B16:20 requirements for their ability to remain effective under repeated compression as they continue to offer a reliable solution and high level of performance.
For those that comply with the standards, these gaskets will be stamped to ensure quality and reliability.
In 2017, there was a revision to the B16:20 ASME gasket construction, which outlines a maximum compression requirement as well as the required gasket stress per performance class, as well as performance testing requirements.
In addition, recommendations have been released announcing that spiral wound gaskets should have an inner ring as standard to ensure the gasket’s credibility, quality, safety, and reliability.
So, although low-stress gaskets may be able to alleviate some bolted joint failures, they at present can’t wholly meet industry standards. This means this type of gasket has now been removed as a reference for all piping specifications.
Benefits of spiral wound gaskets
- Offer excellent sealing performance
- Resistant to high temperature and pressure
- Corrosion and chemical-resistant
- Durable
- Long-lasting.
The construction of the spiral wound gasket makes them a suitable solution for oil and gas, chemical, pharmaceutical, and petrochemical industries.
To find out more and for further information, contact 01535 274 776 and see how we can help you today.
