Gaskets
Proper selection of gaskets depends upon following factors.
- Compatibility of the gasket material with the fluid.
- Ability to withstand the pressure-temperature of the system.
Based on the type of construction, gaskets are classified as:
- Full Face
- Inside bolt circle
- Spiral wound metallic
- Ring type
- Metal jacketed
For high temperature and high pressure applications, spiral wound metallic gaskets are used.
ASME B 16.5 does not recommend the use of 150# rating gaskets on flanges other than welding neck and lapped joint type.
The spiral wound gasket will perform when the flange face is 125-250 AARH finish.
Dimensional Standards for Gaskets
- API 601 -Metallic Gasket for Refinery Piping
- BS 3381 -Metallic Spiral Wound Gaskets
- ASME B16.20 -Metallic Gaskets for pipe flanges
- ASME B16.21 -Non-metallic Gaskets for pipe flanges
Insulating Gasket kits
Insulating gasket kits are used between dissimilar metals to avoid galvanic corrosion.
Bolting
For low pressure, low temperature services, machine bolts are used and studs are used otherwise.
Flanged joints using low strength carbon steel bolts shall not be used above 200oC or below –29oC
Material of Construction for Bolting
Bolting materials normally used are
- ASTM A 307 -Low Carbon Steel Bolting Material
- ASTM A 320 -Alloy Steel Bolting material for low temperature service
- ASTM A 563 -Carbon and alloy steel nuts
- ASTM A 193 -Alloy Steel Bolting Material for high temperature service
- ASTM A 194 -Alloy Steel nut material for high temperature service