Three distinct elements of a flanged joint must act together to provide a leak-free joint:
- the flanges,
- the gasket, and
- the bolting
Factors that affect performance include the following:
(a) Selection and Design
(1) consideration of service conditions (including external loads, bending moments, and application of thermal insulation)
(2) flange rating, type, material, facing, and facing finish (see para. F308.2)
(3) gasket type, material, thickness, and design (see para. F308.4)
(4) bolt material, strength (cold and at temperature), and specifications for tightening of bolts (see para. F309.1)
(5) design for access to the joint
(b) Installation
(1) condition of flange mating surfaces
(2) joint alignment and gasket placement before boltup
(3) implementation of specified bolting procedures
Source: ASME B31.3 Appendix F