PWHT is defined as one of heat treatments done after welding/machining to improve the chemical mechanical properties of weldment/machined surfaces. In concept, PWHT covers many different potential treatments. However, in steel fabrication, most common procedure used is stress relieving. When is it required? Machining and/or welding induce stresses in parts. The bigger and more complex the part, the more the stresses. These stresses can cause distortions in the part in long term. If the parts are clamped in service, then cracking could occur. Also, hole locations can change causing them to go out of tolerance. For these reasons, stress relieving is often necessary. How is stress relieving done? Stress relieving is done by uniformly heating fabricated equipment or the vessel or vessel part to a sufficiently high temperature, but below the lower transformation temperature range, then subjecting it to a thermal retardation for a sufficient time depending upon the material thickness and then finally uniformly cooling it which is also of utmost importance.

Advantages of PWHT/stress relieving: a much greater dimensional stability is obtained and maintained; the potential of stress induce cracking is reduced; metallurgical structure is improved; strength of the material and life of the equipment is enhanced; reduce down time; and heat treatment temperature cycle graph is taken with each batch. The company has 5 furnaces – size ranging from length 1.6 to 15 m x width 1.2 to 5 m, to cater various kind of jobs of PWHT and SR.

Products: Post Weld Heat Treatment (PWHT) & Stress Relieving