Spiral wound gasket, type CG.The first spiral wound gasket was developed in 1912. Spiral wound gaskets are manufactured by alternate layers of metal strip winding and non-metallic fillers spiral winding together into V-shaped, providing the gasket with mechanical resistance and resilience. It can be used for sealing flange joints, tube covers, boilers, heat exchangers, pressure vessels and valves. There are also some other shapes of strip winding, such as W & SU spiral wound gaskets. The spiral wound gasket normally includes the parts of outer centering ring and inner ring, it can reinforce the power of gasket. They are ideal for oil, steam, liquids, acids, various organic mediums and solvents.

Types of Spiral Wound Gasket

The standard spiral wound gasket can be categorized in four styles: reinforce (Style R), inner ring with reinforce (Style RIR), centering gasket (Style CG), centering gasket with inner ring (Style CGI).

Style R spiral wound gasket.	Style RIR spiral wound gasket.
Style CG spiral wound gasket.	Style CGI spiral wound gasket.

1)Style R
Style R is the basic type of spiral wound gasket. Style R’s inner diameter and outer diameter has a few laps metal strips that do not fill the fillers. They maintain the compression and sealing. The Style R spiral wound gasket is normally used for tongue and groove, male and female type joint of flanges.
2)Style RIR
The inner ring is between the bore diameter and the inner diameter of the gasket. It is designed to prevent accumulation of solids, reduce turbulent flow of process fluids and minimize erosion at flange faces. It’s used for male and female flanges.
3)Style CG
The centering ring accurately make the spiral ring on flange face. It provides an extra radial strength to protect the spiral ring. Style CG gaskets are suitable for flat face flange and raised face flange.
4)Style CGI
The style CGI spiral wound gasket is combined the advantages of centering ring and inner ring. Suitable for high temperature and high pressure. It can be used for above Class 900, corrosive medium or other harsh working conditions.
Spiral wound gaskets also have some other special types gasket,  like style HE, style 625 and etc. It can be used in special application.

Manufacturing Technique

The production of strip winding contain four step: cutting, forming, winding and spot welding. Gasket including reinforcing ring need extra processes of fabrcating and assembling. The inner and outer windings shall have a minimum of three plies of performed metal strip without filler. The initial two plies of inner windings shall have spot welds spaced around the inner circumference. The minium welds shall be three. The outer windings has a minimum of three welds along the circumference of a circle. The metal strip in the winding shall be 0.15-mm(0.006-in.) to 0.23-mm (0.009-in.) thick. The filler material thickness shall be determined by the manufacturer. The inner ring thickness shall be from 2.97 mm to 3.33 mm (0.117 in. to 0.131 in.). The inner ring inside diameter may extend a maximum of 1.5mm(0.06 in.) into the flange bore.

Characteristic of Spiral Wound Gasket

Spiral wound gaskets are widely used in various industries services. They are easiest to install, and suitable for the equipment, where the gasket suffering extreme temperature or pressure cycling, shock or vibration. Their solid construction provides stability and seallability even when the sealing surfaces are slightly corroded or bent.

Temperature & Color of Special Materials

Gaskets are color coded to help expedite the selection and identity of the gaskets. The color on the outside edge of the centering ring identifies both the winding and filler materials. The metallic winding material is designated by a solid color. The filler materials are designated by color stripes at equal intervals on the outside edge of the centering ring. Flexitallic color coding meets the industry standard for metal and filler materials listed in ASME B16.20.

Spiral wound gasket operating temperature with color codeing

Gasket Material	Operating Temperature		Gasket Color Code
	Minimum °F(°C)	Maximum °F(°C)
304 Stainless Steel	-320(-195)	1400(760)	Yellow
316L Stainless Steel	-150(-100)	1400(760)	Green
317L Stainless Steel	-150(-100)	1400(760)	Maroon
321 Stainless Steel	-320(-195)	1400(760)	Turquoise
347 Stainless Steel	-320(-195)	1400(760)	Blue
Carbon Steel	-40(-40)	1700(925)	Silver
Alloy 20	-300(-185)	1000(540)	Black
Hastelloy B2	-300(-185)	2000(1090)	Brown
Hastelloy C276	-300(-185)	2000(1090)	Beige
Monel 400	-200(-130)	1500(820)	Orange
Nickel 200	-320(-195)	1400(760)	Red
Titanium	-320(-195)	2000(1090)	Purple
Incoloy 800	-150(-100)	1600(870)	White
Incoloy 825	-150(-100)	1600(870)	White
Inconel 600	-150(-100)	2000(1090)	Gold
Inconel 625	-150(-100)	2000(1090)	Gold
Inconel X750	-150(-100)	2000(1090)	No Color

Filler Materials.

Filler Material	Operating Temperature		Filler Color Code
	Minium °F(°C)	Maximum °F(°C)
Ceramic	-350(-212)	2000(1090)	Light Green
Flexiable Graphite	-350(-212)	910(510)	Gray
PTFE	-400(-240)	500(260)	White
Mica Graphite	-350(-212)	1400(760)	Pink
Phyllosilicate	-67(-55)	1800(1000)	Light Blue

Centering ring doesn’t come into direct contact with fluid. It’s normally manufactured of carbon steel or painted to avoid corrosion. Other materials are available upon customers’ request. Inner ring is normally used the same material as the metal strip winding.

Manufacturer standard

Spiral wound gaskets are usually designed in accordance with ASME B16.20 and to suit with ASME B16.5, ASME B16.47 Series A&B, and BS1560 flanges, it is also designed in accordance with EN1514-2 to suit with EN1092-1. Spiral wound gasket can be also manufactured in other non-standard shapes like oval and oblong. The customer should provide the inside dimnesions, width and thickness.

EN1514-2 gaskets for EN1092-1 flanges

ASME B16.20 gaskets for B16.5 flanges

ASME B16.20 gaskets for B16.47 flanges