Making a pressure vessel starts with a flat steel plate. But before the first roller touches it, the manufacturer must check one critical thing: does this steel have a traceable identity? Under the Pressure Equipment Directive, every piece of material used in a vessel must be accompanied by an inspection certificate. That certificate stays with the part through cutting, rolling, welding, and testing – all the way to the finished vessel.
The rolling itself is a precise dance. The plate is fed into a three‑roller bending machine. The operator makes several passes, gradually increasing the curvature until the two edges meet with a uniform gap. For thick plates, pre‑bending the ends is essential; otherwise, the cylinder will have flat spots. Once the shell is round, the longitudinal seam is tack‑welded to hold the shape.
PED adds a practical requirement: if cold forming exceeds a certain deformation percentage (usually 5–15% depending on the steel grade), a post‑forming heat treatment is mandatory to restore ductility. Manufacturers document the actual deformation and, if necessary, send the shell to a furnace. The result is a cylinder that is not only round but legally compliant – ready for the next stage.
Post time: May-19-2026