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Types of Flanges

Businesses in a variety of industries rely on flanges to join pipes or components together or to keep equipment secured to a surface. When it comes to choosing the best types of flange for your processes, you’ll want to take the time to research the different options...

Threaded Flange

Threaded flanges are probably the most recognisable of all flanges due to their screw thread design that is used to connect it to the pipe. Threaded flanges, also known as screwed flanges (for obvious reasons), require a male and female thread to create a connection...

Slip On Flange

A slip-on flange can also be known as a hubbed flange, which, as the name suggests, has a hub with a very low profile. Why is this important? Because this type of ring type joint gasket has an internal diameter larger than the connecting pipe, allowing you to slide it...

Weld Neck Flange

Also known as tapered hub flanges or high hub flanges, weld neck flanges are a specific type of gasket with a protruding ridge and long neck used to connect pipework and provide you with a high-quality seal. Weld neck flanges, in particular, are a popular choice when...

Nitrile vs Viton® – What is the Difference?

As you start to make a decision about what type of O-rings to purchase for your business, you might wonder what material is the most suitable for your unique needs. Every business operation has different requirements for their O-rings, such as the temperature,...

Aflas vs Viton

When it comes to choosing O ring suppliers in the UK, you’ll find that there are a wide range of materials on offer for you to choose from. Many people find that the options can seem quite overwhelming, with some materials having similar properties but offering...

EPDM Gasket

Both the automotive and construction industries have started to use EPDM gaskets more frequently in recent times. This rubber material is UV light resistant and has many fantastic properties that make this part highly effective for a wide range of processes. Keep...

Metal Gaskets

When comparing gaskets for use within your business processes, you’ll find that these can be made from a variety of materials. Metal gaskets are a very popular option, offering many advantages over other materials. When looking at sealing product options, make sure...

AFLAS o ring

O rings come in many different dimensions, thicknesses, and materials. And it is the various different materials that o rings can be manufactured from that make each o ring unique and suitable for specific applications. In fact, there are hundreds of different types...

O Ring Vulcanization Process

With years of o ring knowledge and experience in o ring vulcanization, we're one of the leading experts in providing the right sealing solution for you. To view our full range, visit our O-ring product page, with a wide selection and something to match every...

See our latest catalogue for all the services we offer.

Spiral Wound Gasket Compressibility and Pressure Ratings

Spiral Wound Gasket Compressibility and Pressure RatingsIn order to form a reliable seal, spiral wound gaskets do require a certain degree of pressure.  

The applied pressure allows the gasket to be compressed tightly between the mating surfaces preventing any leaks from occurring. 

Factors such as operating temperature and how the flanges are manufactured will affect the pressure that these spiral wound gaskets are placed under. 

Spiral wound gaskets are typically used in ASME B16.5 flat or raised face pipe flanges and pump applications with recess flanges. 

Knowing the maximum pressure, a gasket can withstand is vital to understanding how suitable it will be for your applications and processes. 

Gasket rating systems 

Spiral wound gaskets do come with class and pressure ratings, allowing you to evaluate and choose the right gasket for you. 

The seven pressure classes are as follows: 

  • 150 
  • 300 
  • 400 
  • 600 
  • 900 
  • 1500 
  • 2500 

The higher the pressure rating, the more pressure the flange can handle because it has been designed and manufactured using more metal. 

This means a gasket with a class of 150 will provide a reliable seal under a pressure load of 150lbs matched with a class 150 flange. 

However, for a spiral wound gasket pressure rating, these are typically labelled: 

  • 0-999 psi, 1000-3000 psi (pressure units). 

These ratings are used to identify windings only gaskets. 

Spiral wound gasket density 

Spiral wound gaskets are available in different densities to match various application loads. And it’s important to be aware that different manufacturers will use different filler densities to achieve the same pressure class, as currently, there is no standardisation for spiral wound gaskets in this area. 

Spiral wound gasket density can be defined by describing: 

  • Number of windings per inch 
  • Filler thickness 
  • Assembly pressure 
  • Number of windings without filler 
  • Spot welds, and 
  • Inner and outer rings used. 

These elements can affect the compressibility of a gasket under load and how well they effectively perform. 

The pipe flange standard B16.20 outlines that all inner rings for larger spiral wound gaskets must have specific fillers to prevent buckling. 

So, suitable gasket materials must be chosen, as should the flange design, in order for spiral wound gaskets to perform effectively in varying pressure and temperature applications and ensuring suitability to specific applications. 

Operating conditions affecting compressibility 

Spiral wound gasket compressibility if affected by several factors, including: 

Stress retention and stress relaxation – if a gasket starts to suffer from stress relaxation, its ability to withstand pressure will decrease, and a tight and secure seal will not be provided. Make sure to check the outer ring on spiral gaskets as this is what can prevent the winding from relaxing as pressure is maintained across the perimeter. 

Material thickness – ideally, we’d always advise you to opt for the thinnest gasket material as these are less likely to fail, helping you to avoid flange distortion and misalignment.  Ideally, you should be aiming for comparable compressibility. 

Flange quality – the quality of the finished metalwork can directly affect the sealing of a joint. Surface finish range ideally for spiral wound gaskets should be between 125 Ra to 250 Ra. 

Load sealability – regularly testing for leaks in applications will allow you to test the quality of the gaskets and the load placed on the joint -replacing any gaskets that aren’t performing before more serious issues arise. Use all recommended torque values along with the manufacturer’s specifications.

Find Out More Here!

Required gasket pressure 

Gaskets require a minimum compression set to provide a strong seal with the flange surfaces, and for additional compression, tightening of the flange bolts can help. 

The chance of leakages decreases as compression loads increase. 

It’s important to know that metal gaskets will require greater stress to compress and seal compared to flexible gaskets.  Whereas non-metallic gaskets rely on friction for their ability to hold internal pressure at the joint. 

Room Temperature Tightness (ROTT) is the universal test that identifies sealing pressure. 

You will find the ratings, class numbers, and pressure numbers (PN) prescribed on all gaskets and flanges.  

For further details on PN ratings and standards, call our team on 01535 274 776. 

Areas to be aware of 

  • For a seal to continue to be effective, consistent pressure must remain on the surface of the gasket.  

Note:  The compression pressure placed on the gasket must be greater than internal fluid pressure from side loading to prevent extrusion of the gasket. 

  • Increasing temperatures in applications can create gasket relaxation. 
  • If too much pressure is placed on flexible gaskets, it can cause extrusion around the flange. 

The team at Specialist Sealing Products can help provide the right technical support for choosing the correct gasket material for your application based on compressibility and pressure. 

Call 01535 274 776 or visit this page to learn more about our products.

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