NON-STRESS RELIEVED WELDED PRESSURE VESSELS

ABSTRACT Large pressure vessels and storage tanks can only with great difficulties be stress-relief heat treated. However, residual stresses in welded joints can be reduced significantly by means of warm pressure test. In that case steels and welding consumables should be chosen so as to achieve surficient fracture toughness in both base metal and welded joints. The fracture toughness - J IC - criterion should be assessed considering the actual level of residual stresses - S r - in welded joints. The results of residual stress measurements performed on welded plates /with the thickness ranging from 100 to 200 mm/ as well as on two model pressure vessels /with the wall thickness 45 mm/ in both as-welded and warm prestressed condition, have demonstrated the benefit of the warm prestressing method. Increased resistance of pressure vessels treated by this method to brittle failure has been proved in practice.