To combat the effects of pressure and temperature fluctuations, flexibility and recovery are essential.
Flexitallic spiral wound gaskets are a precision-engineered solution for flanged joints, heat exchangers, boiler hand-holes, manholes, and other high-temperature, high-pressure applications—providing resistance to virtually every known corrosive and toxic element. The necessity for a gasket to have the ability to recover cannot be over emphasized. The effects of pressure and temperature fluctuations, the temperature differential across the flange face, together with bolt stress relaxation and creep, demand a gasket with adequate flexibility and recovery to maintain a seal even under these varying service conditions.
SPIRAL WOUND GASKET STYLES
- Spiral Wound Gaskets
1. Style CG
Style CG spiral wound gaskets utilize an external ring which accurately centers the gasket on the flange face, provides additional radial strength to prevent gasket blowout and acts as a compression stop.
Gaskets for standard flanges are 0.175" (4.5mm) thick, fitted with 0.125" (3.2mm) thick solid metal rings. Unless otherwise stated.
Style CG spiral wound gaskets can be manufactured in accordance with all relevant gasket standards to suit the following flange designations: ASME B16.5, BS 1560, BS 10, ASME B16.47 Series B (API 605), ASME B16.47 Series A (MSS SP 44), BS 4504, and DIN Flanges.
A general purpose gasket suitable for use with flat face and raised face flanges up to and inclusive of class 2500. Class 900 and above an internal ring is recommended.
2. Style CGI
Style CGI spiral wound gaskets are a Style CG gasket fitted with an internal ring which gives an additional compression limiting stop and provides a heat and corrosion barrier protecting gasket windings and preventing flange erosion.
It is customary to select inner ring material to be the same as the metal winding.
*Note on use of inner rings - 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.
3. Thermiculite 835
4. Style LS & LSI
Style LS spiral wound gaskets have been engineered to provide an alternative to sheet gaskets in Class 150 and Class 300 service.
The traditional spiral wound gasket has its steel windings protruding above the compression stop. (See Traditional vs. "LSI" and "LS" at the bottom left.) This requires a significant loading stress to compress the gasket to its optimum operating thickness.
The LS and LSI gaskets have only soft Flexicarb®, Thermiculite™ 835 or PTFE filler protruding above metal windings and guide ring. Therefore as the gasket is compressed the Flexicarb®, Thermiculite™ 835 or PTFE filler is readily compressed thus producing the sealing mechanism at an earlier stage as compared to the conventionally manufactured spiral wound gasket.
5. Style R & RIR
Style R spiral wound gaskets embody all the exclusive features for keeping compression values in balance with bolting and providing adequate resilience to compensate for variable stresses encountered in service. Style R spiral wound gaskets are manufactured to a nominal thickness of 0.125" (3.2mm). Optimum compression is in the range of 0.090" to 0.100" (2.3mm to 2.5mm) thick.
Special Style R spiral wound gaskets are adaptable to non-standard flanges and can be designed and manufactured according to specifications for high and low pressure applications and for severe corrosive conditions.
Basic construction type, inner & outer diameters are reinforced with several plies of metal without filler to give greater stability & better compression characteristics.
Style RIR spiral wound gaskets are designed to prevent accumulation of solids, reduce turbulent flow of process fluids and minimize erosion of flange faces. The inner ring provides a positive stop preventing the gasket from over compression and possible damages.
Style RIR spiral wound gaskets are manufactured to 0.125" (3.2mm) thickness. The gasket features a solid metal inner ring nominally 0.090" (2.3mm) thick, as an integrated part of its design.
Special styles are available in other thickness.
Solid inner metal ring acts as a compression stop and fills the annular space between flange bore and the inside diameter.
6. Style M, MC & MCS
The Style M spiral wound gasket is designed for boiler manhole cover assemblies. They are usually round, obround or oval shape, depending of course, upon the manhole plate configuration.
Style MC spiral wound gaskets have pre-formed inner and/or outer rings made of spiral windings. This centering guide permits the gasket to assume its correct position and to compensate for inequalities in plate contours and fillets in cold-pressed plates as well as to prevent shouldering and pinching caused by radial misplacement.
Style MCS spiral wound gaskets are manufactured with a solid metal inner and/or outer ring which also prevents over compression of the gasket in high pressure systems.
7. Style T
Style T spiral wound gaskets are used for boiler handhole and tube cap assemblies. They are available in round, oval, obround, square, pear and diamond shapes. Please note Style T gaskets rely on internal pressure in the boiler to properly seat the gasket. This means, when a hydrostatic test is performed on the gasket, the pressure exerted against the plate will further compress the gasket-and it is necessary to tighten each nut to compensate for the additional compression of the gasket under load.
The design features of the basic spiral wound construction alleviate the need for sealing compound. Particularly suitable where old and pitted faces have rendered other gaskets ineffective.
Supplied in thicknesses of 0.125" (3.2mm) or 0.175" (4.5mm). The standard thickness of 0.175" (4.5mm) is recommended for use in assemblies where the seat is relatively broad and bolting load is low.
Standard materials are Type 304 Stainless Steel and Flexicarb®windings. Special materials to suit specific operating conditions are available.
8. Style CG-RJ & CGI-RJ
CG-RJ and CGI-RJ spiral wound gaskets are designed for use as a replacement maintenance item of standard oval and octagonal ring joint gaskets.
These gaskets are:
- Available for NPS 1/2" to 24" and pressure classes 150 to 1500.
- Gasket thickness is 0.175" (4.5mm) and the outer ring thickness is 0.125" (3.2mm).
- Style CGI-RJ gaskets are fitted with an inner ring 0.125" (3.2mm) thick.
- They are recommended for pressure classes 900 and above, and where operating temperatures are above 572° F (300° C).
- For Use in ASME B16.5 and API 6A Ring-Joint Flanges
This style designates a specially sized CG gasket to be used on standard ring joint flanges. The outer ring is dimensioned to cover the ring joint grooves and to prevent the spiral wound portion from entering the groove.
9. Style 625
Style 625 spiral wound gaskets are similar to Style R spiral wound gaskets, except original thickness is 0.0625". These gaskets are widely used wherever space restrictions indicate the need for a wafer thin gasket design capable of sealing high pressures. Style 625 spiral wound gaskets embody all of the exclusive features for keeping compression values in balance with bolting and providing correct resiliency to compensate for variable stresses encountered in service.
Style 625 spiral wound gaskets are manufactured to a nominal thickness of .0625", with compression to .050" - .055".
Style 625 was originally designed for clamp-type closures in aircraft, but are now widely used whenever space limitations indicate the need for a wafer-thin or narrow spiral wound gasket.