Knowledge: Spiral Wound Gaskets
What is a spiral wound gasket?
Table of Contents
Spiral wound gasket is usually made of high quality SUS304, SUS316 (“V” or “W” shaped) stainless steel winding belt and graphite, asbestos, PTFE, non-asbestos and other soft materials alternately overlapping spiral winding, and the metal belt is fixed by spot welding at the beginning and end. The basic type metal wound gasket without inner and outer ring is generally used in low and medium pressure flanges with tongue and groove surface and flat or concave and convex surface.
Performance Characteristics of Wound Gaskets
Wrap-around gaskets have good compression and resilience, multi-channel sealing and self-tensioning function, less sensitive to surface defects on the flange compression surface, do not bond to the flange sealing surface, and can partially eliminate the effects of pressure. It can partially eliminate the influence of pressure, temperature change and mechanical vibration. Low temperature. High vacuum. It can maintain its excellent sealing performance under various harsh conditions such as high temperature, low temperature, high vacuum, shock vibration and other cyclic alternations.
Applications of winding gaskets
Static sealing parts of flange joints in pipelines, valves, pressure vessels, condensers, heat exchangers, towers, manholes, hand holes, etc. in petroleum, chemical, metallurgical, electric power, ships, gas, nuclear, aerospace, textile, pharmaceutical, and mechanical industries.
Winding gasket structure form and code and use flange category:
|Basic type||Code name||Applicable flange sealing surface||Thickness (mm)|
|V-shaped primitives / rings||W-type primitives / rings|
|Basic type||Type A or R||Tenon and groove surface, concave convex surface, plane and groove surface||3.2;4.5||4.8;5.5;7.5|
|With inner ring type||Type B or RIR||Tenon and groove surface, concave convex surface, plane and groove surface||
|With positioning ring||Type C or CG||Plane or convex surface|
|Type with inner ring and locating ring||Type D or CGI||Plane or convex surface|
Type with inner ring:
With positioning ring type:
With inner ring and positioning ring type:
Materials of Wound Gaskets
1. Basic winding metal strip
- A. Cold-rolled steel strip of thickness 0.15mm~0.25mm, such as SUS 304, SUS 316L, SUS 321, etc., or determined by mutual agreement between supply and demand.
- B. The metal strip is pre-formed V or W narrow strip, the surface should be smooth, clean, no roughness, cracks, scratches, pits and rust spots and other defects.
- C. The hardness value of stainless steel HV≤200.
2. Basic winding non-metallic tape
- A non-metallic filled with special asbestos tape, flexible graphite tape, PTFE tape, non-asbestos fiber tape, and mica tape, etc. The thickness of the tape is 0.3-1.0mm.
- B. Special asbestos burning loss must be ≤ 25%.
- C. Non-metallic tape with chloride ion content ≤100PPM
- D. The recommended use temperature and pressure for various media and various non-metallic belts are listed in the following table.
Main technical parameters of various non-metallic materials of winding gaskets.
|Material||Identification code||Temperature / ℃||Maximum working pressure||Applicable media||Compression ratio /%||Rebound rate /%||Stress relaxation rate /%|
|Expanded graphite||F.G.||330||250 BAR||Corrosive medium||18–30||≥17||≤18|
|Special asbestos tape||ASB||300||100 BAR||General air tightness||18–30||≥19||≤28|
|Teflon||PTFE||50||100 BAR||Corrosive medium||18–30||≥15||≤13|
|Asbestos free material||NAF||250||100 BAR||General air tightness||18–30||≥19||≤28|
|Mica||MICA||650||100 BAR||Extra high temperature||18–30||≥19|
|Ceramics||CER||890||100 BAR||Ultra high temperature||18–40||≥19|
The following table is used for material selection of inner ring and wound metal belt:
|The name of the material||Abbreviations tag||Hardness (HB)||Temperature (° C)|
|SUS 304||304||130 ~ 180||– 195 ~ + 550|
|SUS 316L||316L||130 ~ 180||– 100 ~ + 550|
|SUS 321||321||130 ~ 190||– 195 ~ + 760|
|HASTELLOR-B2||HASTB||215||– 185 ~ + 1090|
|INCONEL-600||INC600||150||– 100 ~ + 1090|
|MONEL-400||MON||150||– 130 ~ + 820|
|Titanium||T2||215||– 195 ~ + 1090|
Thickness tolerance of basic body of spiral wound gasket:
|project||Thickness (mm)||Tolerance (mm)|
|The thickness of the gasket||4.5, 3.2||
|The thickness of the ring||3.0||+ / – 0.25|
The following table shows the diameter tolerance of spiral wound gasket (i.e. nominal pipe diameter for flange):
|DIN (mm)||ANSI B16.5||API 605||Tolerance|
Inner ring inner diameter
Gasket inner diameter
|<=600||<=24″||>=26″ and <=34″||±0.5|
|>600 and <=800||>24″ and <=34″||>=36″ and <=60″||±0.9|
|>800 and <=1600||>34″ and <=60″||±1.3|
|Gasket outer diameter||<=600||<=24″||<=24″||±0.9|
|>600 and <=16000||>24″ and <=60″||>24″ and <=60″||±1.8|
|Outer ring outer diameter||>=1/2″ and <=60″||±0.9|
|>600 and <=1000||>24″ and <=34″||0-1.8|
|>1000 and <=1600″||>34″ and <=60||0-2.2|
Main performance parameters of metal graphite spiral wound gasket:
|Wound gasket coefficient||M = 2.5 4|
|Wound gasket using pressure||25 mpa or less|
|Service temperature of wound gasket||-196℃-700℃ (not higher than 600℃ in oxidizing media)|
|Minimum preload specific pressure of wound gasket||y=68MPa|
Technical Standards of Spiral Wound Gaskets
1. Foreign manufacturing standards for metal wound gaskets are: ASME B 16.20, ASME B 16.5, ASME B 16.47 A (B), BS EN1092, JIS, and NF, etc.
2. Domestic standards:
- HG20610-2009 steel pipe flange with wound gasket Ministry of Chemical Industry European system
- HG20631-2009 Wound gaskets for steel pipe flanges American system of the Ministry of Chemical Industry
- GB/T4622.2-97 Wrap-around gaskets for pipe flange size National standard
- JB/T4719-92 Wound gaskets for shell and tube heat exchangers Ministry of Machinery Standard
- JB/T90-94 Wrap-around gaskets for pipe flanges Ministry of Machinery Standard
- JB/T4705-2000 Wound gaskets for pressure vessel flanges Ministry of Machinery Standard, etc.
Source: China Spiral Wound Gaskets Manufacturer – Yaang Pipe Industry (www.epowermetals.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.)
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