Standard of spiral wound gasket: challenges brought by new requirements of ASME b16.20-2017

ASME b16.20 metal gasket standard for pipe flange is one of the most widely used gasket standards for pipe and equipment flange, and the spiral wound gasket is the most frequently used standard in this standard.

Today, I would like to share the changes and challenges of ASME b16.20-2012 and 2017.

The ASME B16.20-2012 edition provides the details of the gasket structure and dimensions, but only the compression test requirements are put forward for the performance requirements, which has led many people to question its effectiveness because it cannot guarantee its proper gasket Sheet sealing performance.
The ASME B16.20-2017 version not only modified the compression test requirements for spiral wound gaskets, but more importantly, increased the sealing test requirements for spiral wound gaskets. This is a fundamental change to the performance requirements of spiral wound gaskets. The details are shown in:

Changes in compression testing requirements

The American Standard ASME B16.20 has only one requirement for spiral wound gaskets, which is the requirement for gasket compression performance. Specifically, it can be divided into two parts:

  • The first part, 150, 300 and 600 pounds of NPS1/2, NPS3/4 and NPS1 bolt spiral wound gaskets, should be designed as follows: based on the nominal bolt root diameter, under 172MPa (25,000psi) uniform bolt stress, the gasket The thickness will be compressed to 3.30 mm ±0.13 mm (0.130 in. ± 0.005 005 in.).
  • In the second part, gaskets of all other specifications and pressure levels shall be designed such that the thickness of the gasket will be compressed to 3.30mm ± 0.13mm (0.130 in. ± 0.005 in.) under a uniform bolt stress of 207 MPa (30,000 psi).

The latest version of the ASME B16.20-2017 metal gasket standard is divided into three parts for the compression performance requirements:

  • In the first part, for the 150-pound spiral wound gasket, calculated based on the gasket inner diameter and outer diameter in the ASME B16.20-2017 dimension table, under a gasket stress of 52MPa, the thickness of the gasket after compression should not be less than 3.43mm (0.135 in.).
  • The second part, for spiral wound gaskets of 300 to 600 pounds, under the gasket stress of 70MPa, the thickness of the gasket after compression should not be less than 3.43mm (0.135 in.).
  • In the third part, for spiral wound gaskets of 900 pounds and above, the thickness of the gasket after compression should not be less than 3.43mm (0.135 in.) under a gasket stress of 140MPa.

New leak test requirements are added

In addition to the fundamental change in the requirements for compression testing, a new requirement has been added, which is the testing of gasket sealing performance. The specific requirements are as follows:
For finished spiral wound gaskets of all sizes and pressure levels, they should be able to meet the maximum allowable leakage rate of 0.0137mg/s∙m. The length of the circumference must be calculated by the outer diameter of the gasket (sealing surface) size in the dimension table. The test must use an external calibration gas source with a known methane concentration at room temperature, and the flow rate of the test gas is 1L/min.

  • Test equipment: The surface roughness of the test equipment must comply with ASME B16.5, be able to isolate the gasket in order to direct any leakage to the detection probe, and be able to test during the pressurization of methane (minimum purity of 97%) inside the gasket Provide a uniform load on the gasket sealing element.
  • Gasket stress: The stress uniformly applied to the gasket should be 35MPa (5000psi) for the 150-pound spiral wound gasket, and 56MPa (8000psi) for the 300- and 400-pound spiral wound gasket, 600 pounds and above Spiral wound gaskets use 70MPa (10000psi).
  • Test pressure: The test internal pressure should be 20bar (290psi) for spiral wound gaskets of the 150-pound class and 40bar (580psi) for the 300-pound and above spiral wound gaskets.
  • Test result: The test pressure should be maintained for at least 4 hours. After that, take 3 readings every 5 minutes or so, and then compare the average of these 3 readings with the maximum allowable leakage rate.

The following picture shows typical test equipment:

20201213040402 90756 - Standard of spiral wound gasket: challenges brought by new requirements of ASME b16.20-2017

Now that the new version of the ASME B16.20 standard adds test requirements, what challenges will this bring to the sealing industry?

First of all, the ASME B16.20-2017 standard does not specify the type test of a spiral wound gasket of a certain specification and pressure level like the spiral wound gasket of the national standard, and the test results can meet the standard.
In theory, the spiral wound gasket of the ASME B16.20-2017 standard needs to be tested for every specification and pressure grade of spiral wound gasket, and a separate manufacturing process is developed to meet the requirements of the standard. In fact, It is impossible to meet this requirement. Only the capabilities of the experimental equipment (including the maximum load of the compression testing machine and the size of the pressure plate) can hardly meet the testing requirements of all specifications of spiral wound gaskets.
Secondly, the test medium for the leak rate of the ASME B16.20-2017 standard has changed from the normal nitrogen used in the country, and methane is used as the test medium. Since methane is a flammable medium, there are strict regulations for laboratories and safety protection and operation. It is destined that not every spiral wound gasket manufacturer can test and inspect spiral wound gaskets in accordance with the requirements of the ASME B16.20-2017 standard.
Due to the above changes and challenges, it is necessary for our spiral wound gasket users, designers and manufacturers to have a unified understanding of how to test and certify the performance of gaskets. For example, after passing the gasket test of a certain specification and pressure level , Whether it can be determined that a certain series of gaskets meet the standard requirements, this is worth exploring, and it needs to do enough basic tests to reach a conclusion. This is also a new challenge for the use, design and manufacture of spiral wound gaskets brought by the standard revision.

Source: China Spiral Wound Gaskets Manufacturer – Yaang Pipe Industry (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@steeljrv.com

Please notice that you might be interested in the other technical articles we’ve published:

References:

  • 1. ASME B16.20-2012 Metallic Gaskets for Pipe Flanges
  • 2. ASME B16.20-2017 Metallic Gaskets for Pipe Flanges
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standard of spiral wound gasket challenges brought by new requirements of asme b16 20 2017 - Standard of spiral wound gasket: challenges brought by new requirements of ASME b16.20-2017
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Standard of spiral wound gasket: challenges brought by new requirements of ASME b16.20-2017
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The ASME B16.20-2017 version not only modified the compression test requirements for spiral wound gaskets, but more importantly, increased the sealing test requirements for spiral wound gaskets.
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