The domed ends of a pressure vessel – often called heads – are formed separately, then welded to the shell. The two most common methods are hot pressing and cold spinning. Both have tricks that can make or break PED compliance.
In hot pressing, a circular disc is heated evenly in a furnace, then placed between a male and female die. A hydraulic press squeezes it into shape. The danger? Uneven heating or a too‑deep draw can thin the crown beyond the design minimum. PED requires that the minimum thickness after forming be verified by measurement – no guessing. A head that fails thickness is scrap metal.
Cold spinning works differently: a disc rotates on a lathe while rollers push the metal into a dome. No heat means no scaling, but cold work can cause micro‑cracking in the knuckle region. PED demands that after cold spinning, the knuckle area be examined by a non‑destructive method (usually magnetic particle testing for carbon steel). Only when the head shows no cracks or excessive thinning can it move to welding. A good head is a quiet triumph – and the paperwork proves it.
Post time: May-22-2026