Basic type of PTFE spiral wound gasket

Introduction of spiral wound gasket

The spiral wound gasket is made of high-quality SUS304, SUS316 ("V" or "W" shape) metal strips and other alloy materials alternately overlapped with graphite, asbestos, PTFE gasket, non asbestos and other soft materials. The metal strips are fixed by spot welding at the beginning and end. The metal spiral wound gasket is one of the semi-metal sealing gaskets with good resilience. The structural density of the metal spiral wound gasket can be made according to different locking force requirements, and the maximum compression degree can be controlled by using the inner and outer steel rings. The surface accuracy of the flange sealing surface contacted by the metal spiral wound gasket is not high. The spiral wound gasket is especially suitable for the occasions where the load is uneven, the joint force is easy to relax, the temperature and pressure change periodically, and there is impact or vibration. Spiral wound gasket is an ideal static sealing element for flange joints of valves, pumps, heat exchangers, towers, manholes and handholes.

1、 Basic spiral wound gasket

Structure type, code and flange type of spiral wound gasket:

Basic form Code Applicable flange sealing surface Thickness (mm)

V-primitives / rings W-type primitive / ring

Basic type Type A or R Tenon surface, concave convex surface, plane and groove surface 3.2; four point five 4.8; 5.5; seven point five

With inner ring Type B or RIR Tenon surface, concave convex surface, plane and groove surface 3.2/2

4.5/3 4.8/3.0

5.5/4.0

7.5/5.0

Outer ring Type C or CG Plane or convex

Type with inner ring and outer ring Type D or CGI Plane or convex

2、 Materials:

1. Spiral wound gasket metal belt

A. SUS304, SUS316L, SUS321 and other cold rolled steel strips with thickness of 0.15mm ~ 0.25mm shall be adopted or determined by both parties through negotiation.

B. The metal strip shall be preformed V-shaped or W-shaped narrow strip, and its surface shall be smooth and clean without rough, uneven, crack, scratch, pit, rust and other defects

C. Hardness value of stainless steel HV ≤ 200

2. Spiral wound gasket non-metallic tape (filling)

A non metallic filler is special asbestos tape, flexible graphite tape, polytetrafluoroethylene tape, non asbestos fiber tape, mica tape, etc. The thickness of the strip is 0.3-1.0 mm.

B. Loss on ignition of special asbestos must be less than 25%

C. Chloride ion content of non-metallic belt ≤ 100ppm

D. Recommended service temperature and pressure of various media and nonmetallic belts

3、 Main technical parameters of various non-metallic materials of spiral wound gasket:

Material Science Identification code Temperature (℃) Maximum working pressure Applicable medium Compression ratio% Rebound rate% Stress relaxation rate%

expanded graphite  F.G. - 220--550 250 BAR Corrosive medium 18--30 ≥17 ≤18

Special asbestos belt ASB - 150--450 100 BAR General air tightness 18--30 ≥19 ≤28

teflon PTFE - 200-- 250 100 BAR Corrosive medium 18--30 ≥15 ≤13

Non asbestos material NAF - 100--350 100 BAR General air tightness 18--30 ≥19 ≤28

Mica MICA - 150--800 100 BAR Extra high temperature 18--30 ≥19  

 Ceramics CER - 200--1090 100 BAR Ultrahigh temperature 18--40 ≥19  

 The following table is used for material selection of inner ring and winding metal:

Material name Abbreviation mark Hardness (HB) Temperature（ ° C)

SUS 304 three hundred and four 130~180 - 195~+550

SUS 316L 316L 130~180 - 100~+550

SUS 321 three hundred and twenty-one 130~190 - 195~+760

HASTELLOR-B2 HASTB two hundred and fifteen - 185~+1090

INCONEL-600 INC600 one hundred and fifty - 100~+1090

MONEL-400 MON one hundred and fifty - 130~+820

titanium TI two hundred and fifteen - 195~+1090

Thickness tolerance of spiral wound gasket basic body:

project Thickness (mm) Tolerance (mm)

Gasket thickness 4.5, 3.2 + zero point two

-0.1

Ring thickness three ± zero point two five

The following table shows the diameter tolerance of spiral wound gasket (i.e. nominal pipe diameter for flange)

DIN (mm) ANSI B16.5 

BS1560 (mm)

Mss sp-44 API 605 tolerance

Inner ring diameter

Inner diameter of gasket <= six hundred <= 24" >= 26" and <=34" ± zero point five

>600 and <=800 > 24" and <=34" >= 36" and <=60" ± zero point nine

>800 and <=1600 > 34" and <=60" ± one point three

>1600 > 60" ± one point six

Gasket outer diameter <= six hundred <= 24" <= 24" ± zero point nine

>600 and <=16000 > 24" and <=60" > 24" and <=60" ± one point eight

one thousand and six hundred > 60" ± two point two

Outer ring diameter >= 1/2" and <=60" ± zero point nine

<=600 <= 24" 0-1.0

>600 and <=1000 > 24" and <=34" 0-1.8

>1000 and <=1600" > 34" and <=60 0-2.2

4、 The main performance parameters of common metal graphite spiral wound gaskets are as follows:

Coefficient of spiral wound gasket m=2.5-4

Service pressure of spiral wound gasket ≤25MPa

Service temperature of spiral wound gasket - 196 ℃ - 700 ℃ (not higher than 600 ℃ in oxidizing medium)

Minimum pre tightening pressure of spiral wound gasket y=68MPa

5、 Technical standard:

1. The foreign manufacturing standards of spiral wound gaskets are: ASME b16.20, ASME B16.5, ASME b16.47 a (b), BS en1092, JIS, NF, etc

2. Domestic standard has hg20610-2009 spiral wound gasket for steel pipe flange, European system of Ministry of chemical industry

Hg20631-2009 spiral wound gasket for steel pipe flange

GB / t4622.2-97 national standard for dimensions of spiral wound gaskets for pipe flanges

JB / t4719-92 standard of Mechanical Department of spiral wound gasket for shell and tube heat exchanger

JB / t90-94 standard of Mechanical Department of spiral wound gasket for pipeline flange

JB / t4705-2000 standard of mechanical department for spiral wound gasket for pressure vessel flange. For more standards or requirements, please contact us

6、 Product introduction

This product is A-type metal wound gasket, which is made according to the national standard. The material is 304 steel strip and flexible graphite. The shape of the product is O-type, as shown in the figure below. The product is beautiful, excellent quality and strong applicability.