In what situations are necked butt weld flanges and flat weld flanges used respectively?
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In what situations are necked butt weld flanges and flat weld flanges used respectively?
There are no plate butt welds for PN63 and above
The stress conditions are different! The safety level is also different! Choose based on medium, temperature, and pressure!
Those with a neck have high pressure resistance; welding them also results in fewer weld defects, but they are expensive
From a process safety perspective: Both Class A and Class B pipelines currently require butt welding with reinforcement or lap welding with reinforcement in order to improve the quality of the welds, as well as for flaw detection purposes.
Flat welding flanges: Advantages include easy material availability, simple manufacturing, low cost, and wide application. Disadvantages are their relatively poor stiffness; therefore, they cannot be used in chemical process piping systems where there are requirements for resistance to stress, in environments with flammable or explosive substances, or in situations requiring high vacuum levels, as well as in highly hazardous environments. The seal surface types include flat and convex surfaces.