Treatment of special pipe fitting caps

　　The special pipe fitting caps will crack under the environment of nitrate, ammonia, alkaline sodium, etc., and the ASTM A234 Wpb Special Pipe fitting Caps will eliminate the residual stress; the austenitic stainless steel will crack under the specific environment with chloride ion, please select the appropriate data during the planning; the carbon steel vessel that needs hot-dip galvanizing or aluminizing needs to be heat treated first to remove the residual stress.

　　When splicing large-diameter special pipe fitting caps, the weld direction is only allowed to be radial and circumferential. This requirement may be cancelled for special pipe fitting caps in the future. The coefficient of welded joint refers to the ratio of the strength of butt welded joint to the strength of base metal.

　　Under the action of uniform internal pressure, the membrane stress of the thin-walled hemispherical vessel is half of that of the cylinder with the same diameter. Therefore, from the stress analysis, the spherical head is an ideal structure. But the disadvantage is that it is difficult to punch with large depth and small diameter as a whole. Special pipe fitting caps are often used on high pressure vessels.