335 ASSEMBLY AND ERECTION
335.1 Alignment
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(c) Flanged Joints
Unless otherwise specified in the engineering design, flanged joints shall be aligned as described in (1) or (2), and (3).
(1) BEFORE BOLTING, mating gasket contact surfaces shall be aligned to each other within 1 mm in 200 mm (1/16 in/ft), measured across any diameter.
(2) The flanged joint shall be capable of being bolted such that the gasket contact surfaces bear uniformly on the gasket.
(3) Flange bolt holes shall be aligned within 3 mm (1/8 in.) maximum offset.
335.2 Flanged Joints
335.2.1 Preparation for Assembly
Any damage to the gasket seating surface that would prevent gasket seating shall be repaired, or the flange shall be replaced.
335.2.2 Bolting Torque
(a) In assembling flanged joints, the gasket shall be uniformly compressed to the proper design loading.
(b) Special care shall be used in assembling flanged joints in which the flanges have widely differing mechanical properties. Tightening to a predetermined torque is recommended.
335.2.3 Bolt Length
Bolts shall extend through their nuts such that there is complete thread engagement for the full depth of the nut.
335.2.4 Gaskets
No more than one gasket shall be used between contact faces in assembling a flanged joint.
335.2.5 Flanged Joint Assembly
Assembly requirements for bolted flanged joints and flanged joint assembler qualifications shall be considered in the engineering design.
For guidance, see ASME PCC-1, Guidelines for Pressure Boundary Bolted Flange Joint Assembly, and ASME BPVC, Section VIII, Division 1, Nonmandatory Appendix S.