Spiral Wound Gaskets for Uniflex (SUA) Unions

The Uniflex Union uses a spiral wound gasket as the sealing surface to ensure a tight seal.  The spiral wound style gasket has become the industry standard in sealing applications because of its diversity and resiliency.  In order for a gasket to provide a leak tight seal it must handle the effects of temperature and pressure fluctuations, stresses due to temperature fluctuations across a fitting face, and imperfections in pipe alignment and face imperfections.  The spiral wound gasket is the solution in such conditions with the ability to seal against almost all known corrosive and toxic media.

 The Uniflex Union, regardless of construction material, comes standard with a 304 Stainless Steel R-Style Spiral Wound Gasket with a Flexicarb filler.  Numerous alternatives are available for this gasket with variations in both the winding metal and the filler material.
The R-Style Spiral Wound Gasket consists of metallic windings and filler sealing element only with no guide or inner ring, like the CG style.  This type of gasket is commonly used in tongue and groove type applications where male and female flanges are found.  The inner and outer gasket diameters are reinforced with several plies of metal without filler to give greater stability and compression characteristics.  For detailed information regarding spiral wound gaskets reference ASME B16.20

 How to identify the winding material of a spiral wound gasket:

All of the R-Style gaskets pretty much look the same.  In accordance with ASME B16.20 the gaskets are identified through color-coding by marking the inside ring of the gasket.  This marking is painted to facilitate identification.

How to identify the filler material of a spiral wound gasket:

It is equally important to be able to identify the filler material in a spiral wound gasket.  Certain sealing applications require specific properties in a filler material.  When identifying this filler the face color of the gasket is observed.  The standard graphite based fillers, being the most prevalent, are gray striped.

 

 Filler material descriptions:

Flexicarb (Uniflex Standard)

This material is a high purity flexible graphite with no binders and fillers composed of 95 – 98% carbon.  It exhibits superior sealability, and excellent resistance to a wide range of chemicals.  Flexicarb can be used at temperatures from cryogenics to 900F in an oxidizing atmosphere, and up to 6000F in a reducing or neutral atmosphere.  Its unique combination of low permeability, inherent lubricity, and compressibility make Flexicarb suitable for critical gas and vacuum service.  Flexicarb also has the ability to flow into flange imperfections.  The leachable chloride content of Flexicarb is 100 ppm maximum.

 Polytetrafluoroethylene (PTFE)

This is used as a filler material in spiral wound gaskets where extreme chemical inertness is required for temperatures ranging from cryogenic to 482F.  PTFE is unaffected by any known chemicals except molten alkali metals and fluorine precursors.  Because of its low permeability, PTFE is frequently utilized on vacuum applications.

Ceramic Fiber Paper

This consists of aluminum silicate fiber with an organic binder.  This material has an excellent high temperature stability to 2300F.  It also resists attack from the most corrosive agents (except hydrofluoric and phosphoric acids) as well as concentrated alkalies.

FILLER MATERIAL TEMPERATURE LIMITS

 

Filler

 

Lower limits

 

Upper Limit

 

 

 

F

C

 

F

C

 

 

 

 

 

 

 

 

 

Ceramic

 

-350

-212

 

2000

1090

 

Flexible Graphite

 

-350

-212

 

950

510

 

PTFE

 

-400

-240

 

500

230

 

Mica Graphite

 

-350

-212

 

600

345