Heat Treatment

Post Weld Heat Treatment Services ( 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.

Post weld heat treatment reduces the residual stresses formed during welding. It also restores the macro structures of the steel. PWHT requirements are to be strictly followed in high pressure applications to avoid component failure.

PWHT eliminates the effects by heating , soaking & cooling the weld area in controlled manner to temperature below the first transformation point , giving the macro structure sufficient time to readjust to its original state & removing the residual stress.

Heat Treatment Services

BISCO offers Heat treatment services such as stress relieving, normalizing, solution annealing, hydrogen diffusion, intermediate stress relieving, tempering etc. BISCO provides post weld heat treatment by using electricity as source of heating for stress relieving of weld joints as well as also uses diesel fuel as source of heating for stress relieving for pressure vessels. Our heat treatment services are designed to minimize downtime, improve structural integrity, and enhance effective plant life. Additionally, depending on the mobility of the required equipment many of our heating processes can be applied on-site or at your facility.

Heat treatment process is carried out by using following methods

+ Electrical Resistance Heating Method

+ Internal Heating Method using Gas / Oil Fired High Velocity Burner.

+ Temporary Gas / Oil / Electrical Fired Furnace.

Product Range

+ Furnace Equipments

+ Heat Treatment Equipment – Mobile

Internal Heating Method

Jobs such as Horton Sphere, Mounded Bullet, Thin Wall Tank, LPG Bullet, Columns,Pressure Vessel, Penstock can be heated by internal heating method using Gas,Oil fired burner system. Other jobs, which required Refractory Dry out and Coating Curing, can also be performed using internal heating method.

Temporary Furnace Heating Method

The Pressure Vessel, LPG Bullet & Structural in bulk quantity can be heat treated in Permanent or Temporary Furnace using Electrical Gas or Oil Firing method

Local Electrical Heating Method

Various pipes, Cir Seam joints, heat exchangers & Structural jobs of intricate shape can be heat treated-using Electrical heating Method.

BISCO has specialized personnel and equipment to carry out a wide range of heat treatment processes like post weld heat treatment of vessels, piping, spheres and fabricated spools , local Post weld heat treatment of carbon steel piping welds (pipe-work, headers, flange joints, valves and branches) by means of the electrical resistance method, in the form of ceramic heater pads.

PWHT Equipment

All PWHT equipments are well maintained & have a valid current calibration certificate. Electric power sources are 380/440V 3 phase 50Hz primary supply step down transformer secondary output (heat treatment unit) giving low voltage circuits. Temperature control equipment is either manually operated through energy regulators or automatically operated using modular controls. Recording of temperature, for the electrical resistance method, or the induction heating method is by means of calibrated chart type temperature recorder. Calibration frequency of recorders will be one year

BISCO Reference Codes and Standards for heat treatment

+ ASME B31.3 : Process Piping

+ ASME Sec IX : Welding and Brazing Qualification

+ AWS D10.10 : Local Heat treatment of Welds in Piping and Tubing.