Use of LapJoint Flanges on U Stamp Pressure Vessels

The flanges you intend to use are not accepted for use without the Vessel Designer proving they're adequate through Code Calculations. Otherwise you would need to use ASME B16.47 flanges to avoid the calculations.

Mark

A. According to ASME code Section VIII, Division 1, the use of lap joint flange (VAN STONE flange) is accepted per Mandatory Appendix 2, Fig. 2.4(1). But a vessel designer must proceed the required design.

B. For LWN flanges, the ASME codes don't imply any mention to those type of flanges, but we -as a designers- used them without any limitations.

C. For lap joint flange (composed from loose ring or flange and stub end) :

1. For a pressure vessel fabricated from carbon steel, you can use SA105 lap joint flange, where the flange (loose ring) is Hot Dipped Galvanized (or may be stainless steel), but the stub end which welded to the vessel shall be CS without galvanizing, because you are not allowed to weld any part after its galvanization.

2. For a pressure vessel fabricated from Nickel201, AISI 904L or AISI 304L, the flange (loose ring) can made from these materials or any other material, but the stub end which welded to the vessel shall be made from the same type and grade of shell material: Nickel201, AISI 904L or AISI 304L respectively.