Dear All,

As per 5.1.3.4 of API650 Lap-welded joints, as tack-welded, shall be lapped at least five times the nominal thickness of the thinner plate joined; however, with double-welded lap joints, the lap need not exceed 50 mm (2 in.), and with single-welded lap joints, the lap need not exceed 25 mm (1 in.).

with detail point of view my question is when overlapping the roof and compression plate the dimensions will be follow as per above clause or we can give more than 50 mm overlap on Roof compression plate joint and if allowed what is the maximum overlap code is allowed. is code allowed 350mm or 400mm overlap?

Thanks&Reagrd's
Jamil

Dear Jamil,

I think you refer to something as shown in detail i of Figure .2—Permissible Details of Compression Rings.

In my opinion, the lap joint there is far enough from junction compression bar- compression ring, so you may apply the same rules as for the rest of roof lap joints. "Wh" dimension (width of the roof compression bar considered to participate in resisting the circumferential force acting on the compression-ring region) is chosen as the local effects of the junction are minimized.

However in practice the lap distance is more than that minimum; of course this is "allowed" considering the requirement is expressed as "need not to exceed".

I think you would review also API 620 requirements, since Appendix F of API 650 asks to consider also API 620. Please see F.7.2 "The design and welding of roofs and the design, reinforcement, and welding of roof manholes and nozzles shall be completed with consideration of both API 650 and API 620."

Best regards.