Post Weld Heat Treatment is an essential part of both the Operation and Maintenance of assets in the fabrication, Oil & Gas and Power Industry. The welding process can unintentionally weaken equipment by imparting residual stresses into a material which can lead to reduced material properties. This said, Post Weld Heat Treatment (PWHT) is a method used for reducing and redistributing said residual stresses in materials ensuring that the material strength is retained after the welding course. It is also used as a method of hardness control or even to enhance material strength.
In some standards PWHT is compulsory for certain grades or thicknesses, otherwise it is dependent on the material type and the service requirements. Other factors that impact the need for this Inspection are the welding parameter’s, the likely mechanism failure, its alloying system or whether it’s been subject to Heat Treatment previously. Generally, the higher the carbon content and/or the higher the alloy content in materials, the more likely it is to need PWHT after welding activities.
If PWHT is neglected, residual stresses can combine with load stresses to exceed materials limitations which can lead to weld failures, weld cracks and make a weld vulnerable to brittle facture.
At SONOMATIC’s NDT Facilities, we have large specified areas for Heat Treatment activities which hold permanent Heat Treatment Machines and have the allocated floor space to accommodate all sizes of pipework. In addition, utilizing portable equipment, we can offer PWHT at our clients sites at both onshore and offshore locations. At our NDT Facilities we also provide the Non Destructive testing required both Pre and Post PWHT, including Magnetic Particle Inspections and Radiographic Inspections.