Spiral wound gaskets are semi-metallic gaskets that are used for high temperature and high-pressure applications. The main parts of spiral wound gasket are metallic windings and filler material.
Criteria for Selection
- Nature of fluid i.e. corrosive nature, fluid concentration et,
- Operating temperature and pressure.
- Material cost.
Materials of Construction
- Commonly used material for winding are Stainless steel 304, 316 and 321.
- Alternate winding materials also can be used depending upon the services.
- General filler material used are Asbestos and graphite.
- Graphite filler are recommended for very high temperature application.
- The material of the inner ring should be compatible with the process fluid.
- Gaskets with inner ring are used in vacuum service.
- Combinations of metal strip and filler are selected to suit the specific fluid media and operating conditions.
- High Temperature service
- Corrosive fluids.
- Flammable Fluids.
- These gaskets are suitable for high pipeline pressure on flat or raised flange faces.
- Temperatures from cryogenic up to 1000 °C.
- Spiral wound gasket is recommended with flange face finish of 63-250 AARH.
- Due to its excellent compression resilience, it is suitable for sealing spots where the alteration of temperature and pressure are frequent.
- These are Quick to install and remove.
- Gasket are made in a wide variety of sizes and shapes.
- Support rings, inside and Outside the spiral, improve the gasket’s handing, fitting and Versatility.
Construction of Spiral Wound Gasket
For proper positioning, spiral wound gaskets are provided with outer centering ring made up of Carbon Steel. Spiral wound gasket is formed of V-shaped Metallic strip and soft non-metallic filler.
Parts of Spiral Wound Gasket are :
- Filler Material
- Spiral Winding Material
- Centering Ring (Outer)
- Inner Ring
- Inner Ring : Solid inner metal ring acts as a compression stopper. To prevent accumulation of solids, reduce turbulent flow of process fluids and minimize erosion, damages of gasket between flange bore and the inside diameter, the annular space is filled up by solid inner metal ring. – Suitable for male and female pipe flanges.
- Centering Ring : Solid outer ring accurately locates the gasket on the flange face to give the additional radial strength to prevent the gasket blowout and acts as a compression limiter. In case of installing the outer ring, it is very easy to install the gasket to flange face because the end of outer ring will touch at bolts – Suitable for use with flat face and raised face flanges. For class 900 and above an internal ring is recommended.
Types/Styles of Spiral Wound Gasket
Type / Style R
Basic construction, inner and outer diameters are reinforced with several piles of metal without filler to give greater stability and better compression characteristics. Suitable for tongue and groove or male and female or grooved to flat face assemblies.
Type / Style RIR
Solid inner metal ring acts as a compression stop and fills the annular space between flange bore and the inside diameter. Designed to prevent accumulation of solids, reduce turbulent flow of process fluids and minimize erosion of flange faces. Suitable for male and female pipe flanges.
Type / Style CG
These gaskets contains only external ring along with spiral wound portion. This external ring accurately centers Gasket on flange face. Italso provides additional radial strength to prevent Gasket blowout and acts as a compression stop. It is a general purpose Gasket suitable for use with flat face and raised face flanges.
Type / Style CGI
This gaskets contains both internal as well as external metallic ring. These are suitable for use with flat face and raised face flanges and specified for high pressure/temperature service or where corrosive or toxic media are present.
ASME B16.20 which covers spiral wound Gaskets requires the use of solid metal inner rings in
- Pressure Class 900, nominal pipe sizes 24” and larger,
- Pressure Class 1500, nominal pipe sizes 12” and larger,
- Pressure Class 2500, nominal pipe sizes 4” and larger,
- All PTFE filled Gaskets.
Type / Style HE
Type HE Gaskets are used for heat exchangers where pass bars may be required. The outer portion is of standard spiral wound construction, whereas the rib partition is normally of single or double jacketed Type, securely fastened to the I.D. of the spiral wound portion.
Sample Piping Material Specification
- Type : Spiral Wound
- Dim Std : B16.20
- Flange Std : B16.5 and B16.47
- Rating : 150#, 300#, 600#, 900#
- Filler Material : Graphite
- Spiral Winding Material : 316
- Centering Ring : CS : Optional based on service
- Inner Ring : 304, 316