Spiral wound Gasket – Basic Characteristic and Styles

In this article, we will learn about Spiral wound Gasket – Basic Characteristic and Styles

Introduction

The spiral wound gaskets consist of a V-shaped strip of metal which is wound into a spiral. Hence it is called Spiral Wound Gaskets. Normally the metal layers are separated by a filler, usually asbestos. The asbestos provides a good resilience and sealability property to spiral wound gaskets.

Basic Characteristic of Spiral wound gaskets

The spiral wound gaskets are widely used in moderate to critical services in various industries. They are most suitable for the application, where the gaskets subject to extreme temperature or pressure cycling, shock or vibration. These gaskets have the best resistance property when compare with other metal and asbestos type gaskets.

Spiral wound gaskets are used where no gasket centering or compression limiting device is required. Also used in metal-to-metal joints and have a good tolerance for flange surface finish irregularities. Sealing action of the gasket is due to the flow of metal spiral and asbestos fiber as a result of gasket compression.

Spiral-wound gaskets are used for any circular or moderately non-circular applications where an approximate compressed thickness of either 3/32″ or 1/8″ can be tolerated. Excellent performance in joints restricting compression is provided since their resiliency will compensate for modest separation.

Spiral Wound Gasket Thickness and Compression

The compressibility of the gasket will be controlled to some extent for a specific bolt loading by varying the density. Two gasket thickness, 1/8″ and 3/16″ are standard and suitable for most applications.  For 1/8″ thickness gaskets, compression to a thickness of 0.100″ to 0.005″ is recommended. For the 3/16″ thick gaskets, a compression of 0.130″ to 0.005″ is preferable. In the case of non-corrosive services at least 80% of applications could use type 304 range of -320 to +1000 ^oF.

Types or Styles of Spiral Wound gaskets

They are four styles of spiral wound gaskets are available in the market. They are

• Centering Gasket (Style CG)
• Centering Gasket with Inner ring (Style CGI)
• Reinforce (Style R)
• Inner ring with Reinforce (Style RIR)

Centering Gasket (Style CG)

In this style of spiral wound gasket consisting an external solid metal centering ring and the asbestos spiral ring inside the solid metal ring. The external ring which accurately centers gasket on flange face. Also, provide an additional radial strength to prevent the gasket blow-out and acts as a compression stop. A general-purpose gasket suitable for both flat face and raised face flanges.

This style is widely used in both Petrochemical and refinery applications.

Centering Gasket with Inner ring (Style CGI)

This style is similar to Style CG, but it additionally consists of an inner ring. As discussed above the outer ring is used for centering and the internal ring used as an additional compression limiting stop. The internal ring also serves as a barrier to protect the gasket from heat and corrosion and prevent the flange erosion. Suitable for use with a flat face and raised face flanges. It is an ideal gasket for vacuum services.

Reinforce (Style R)

It is a basic configuration of a spiral wound gasket. In which the Inner and outer diameters are reinforced with several plies of metal without filler to give greater stability and better compression and sealing characteristics.  This type of gasket is used for tongue and groove, male and female type joint of flanges. This type of gasket is also used for sealing the pump casing joint and valves bonnet and body fixing joints.

Inner ring with Reinforce (Style RIR)

This style of the gasket, the solid inner metal ring acts as a compression stop and fills the annular space between flange bore and the inside diameter of the gasket. It is designed to prevent the accumulation of solids, reduce turbulent flow of process fluids and minimize erosion at flange faces.

 

Suitable for male and female pipe flanges

Temperature Limits of Gasket Metal Rings and Color Coding

Advantages of Spiral Wound Gasket

The spiral wound design is most popular because it makes a good all-round gasket. It can adjust for temperature changes, shock, and vibration, and can be used at fairly high temperatures and pressures. Besides the multiple sealing actions of the metal edges, the filler compresses under the bolt load to make another barrier against leakage. It can thus fill minute imperfections in the flange faces, while the spring action of the metal helps to create and maintain a tight seal.

Spiral wound gaskets are available in a wide range of materials for various services