Post-Weld Heat Treatment (PWHT)

Overview

TCR Engineering has expanded its services range with a dedicated division that offers both gas and electric post weld heat treatment services including:

• Electric resistance localised PWHT of butt welds for piping projects
• Temporary / permanent furnace heat treatment and normalising.
• Internal high velocity gas firings of spherical and bullet tanks and other large storage tanks / vessels.
• Localised PWHT of vessel closing weld seams.

TCR Engineering undertook PWHT services for Essar Construction at the BF Shell Project at Jindal Steel in Angul, Odisha and at the HURL site as well. Having our base pan-India helps us mobilise faster as well as provide the necessary repair and maintenance of our machines in a rapid manner. Our team members are dedicated and are backed with our supervisory skills gained over TCR’s 53 years of service towards quality assurance to the Indian Industry.

Preheating Services

TCR undertakes preheating of weldment to eliminate weld defects and improve weld quality by avoiding cracking in the heat affected zone (HAZ) or at the weldment.

Furnace Heat Treatment (Static / Temporary / Gas / Electrical)

Within the TCR's lab environment, we have high velocity gas fired burners which create a ‘scrubbing action’ of hot gases against the walls of the component eliminating any cold spots.

Electric Resistance Localised Post Weld Heat Treatment

Carefully controlled localised post weld heat treatment by electric resistance, by TCR's expert heat treaters, tempers the metal and reduces tensile stresses, minimising the risk of brittle fracture, stress and corrosion cracking and metal fatigue.

Post Weld Heat Treatment (PWHT)

TCR Engineering Services offers a diverse range of Heat Treatment Services including pre-heating, post-heating; stress relieving (SR), intermediate SR, normalising, solution annealing, water quenching, tempering, step cooling and drying of the refractory material.

The experienced technicians at TCR are capable of performing heat treatment on weld joints, piping, regenerators, stripper columns, pressure vessels, boiler headers, modules, deck pipelines and structure, boiler heater tubes, and DOTHERM testing. The team is also capable of carrying out 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. It can design, fabricate, calibrate and run a customized electrical furnace for clients.

Post Weld Heat Treatment Services (PWHT) is performed after welding/machining, to improve the chemical and mechanical properties of weldment / machined surfaces. TCR offers post-weld heat treatment by using electricity as the source of heating for stress relieving of weld joints. All TCR’s heat treatment services are designed to minimise downtime, improve structural integrity and enhance effective plant life. Additionally, depending on the mobility of the required equipment, many of TCR’s heating processes can be applied on-site or at client’s facility.

Stress Relieving

For steel fabrication, the most common procedure used is Stress Relieving where machining and/or welding induces stress in parts. The bigger and more complex the part, higher is the amount of stress. Stress Relieving is done by uniformly heating the fabricated equipment, a vessel or a part of the vessel to a sufficiently high temperature, but below the lower transformation temperature range. It is then subjected to a thermal retardation for a sufficient time depending upon the material thickness and then finally cooled uniformly.

TCR has specialised fully automatic programmable equipment capable of controlling Heating rate, Holding time and cooling rate as well as carrying out a wide range of heat treatment processes like post-weld heat treatment of PQR test coupons and various components. TCR has at its disposal, well-equipped tools including electrical furnace with 220- and 80-Volts panel, latest 12-point recorder with digital display, coil and pad-type heating element, oil firing systems and extremely skilled technicians. The Heat treatment equipment is supplied with a chart recorder to record up to 8 thermocouples simultaneously to meet the critical requirements of heat treatment.

Oil Firing on Pressure Vessels

TCR Engineering has a talented crew that uses diesel fuel as the source of heating for stress relieving of pressure vessels with the sole objective of reinforcing process, component integrity, and high quality. The heat treatment specialists from TCR have all the necessary experience and equipment to develop a custom configuration as per specific processes. Our heating processes include low-Range, Mid-Range & High-Range Temperature Heating.

TCR's high-velocity burners enable excellent temperature distribution and uniformity at all times because of the intense scrubbing action. They are also able to construct temporary furnaces at client sites where internal firing is not a practical or cost-effective option.

The heat treatment operation is affected by the firing of the furnace, using one or more gas/oil high-velocity burners with a nominal rating of 1,500,000 kcal/hr (6,000,000 Btu/hr) per burner. Each burner is connected by an armoured flexible hosing to Combustion Air Fan (s), with a maximum output of 2,800 Nm³ per hour via a 150mm diameter outlet, at a pressure of 700mm W.G. The burner is fitted with a (25/20) stainless steel outlet nozzle designed to clear the furnace wall adjacent to the intended opening(s), in such a way that it eliminates the possibility of any direct impingement on components.

Reference engagements.

• HURL Sindri: PWHT via electrical resistance coil method, contract value Rs. 31.85 Lakhs.

• JSOL Blast Furnace 2: PWHT engagement.

• Tata Projects JSOL Coke Oven Battery 5 and 6: PWHT engagement.

Equipment: In-house controlled-rate furnaces. Field equipment for on-site PWHT: induction-coil systems, ceramic-pad resistance heating, oil-firing systems for large pressure-vessel local stress relief. Calibrated thermocouple placement and chart recording.

Standards: ASME PCC-2: Repair of Pressure Equipment and Piping (2022 ed.); AWS D10.10 for thermocouple placement; API 582 for welding guidelines that govern PWHT requirements; ASME B31.3 Process Piping (2024 ed.); ASME B31.4 / B31.8 Pipeline Transportation Systems (2022 eds.); ASME BPVC Section IX.