Industrial Inspection

Post Weld Heat Treatment (PWHT)


PT. EMIRA ENERGI in executing its services. Due to the need for on-site preheat and post-weld heat treatment services. From this modest beginning in heat treatment, PT. EMIRA ENERGI has grown to become to a leading supplier of heat treatment equipment and services, offering electrical and gas or oil-fired heat treatment systems to customers.

Our services include local PWHT (for Pressure Vessel, Storage Tank, and Pipe), Preheating Local, Electrical Resistance Heating, Internal Firing by Gas, and Internal Firing by Oil, Furnace (Electrical, Oil Firing, and Gas Firing).

We also provide field services for pre and post-weld heat treatment to four main industry sectors-general engineering fabrication, power generation, petrochemical/refinery, and offshore/marine PT. EMIRA ENERGI a considerable experience on serving the customer. Our goal is to be a heat treatment solution for your steel.

In our services, we are supported by professional engineers, qualified and experienced personnel in Post Weld Heat Treatment Engineering, and Strength Knowledge in Metallurgy and Material.


Welding Preheat

The material thickness, size of the weldment, and available heating equipment should be considered2 when choosing a method for applying preheat. For example, small production assemblies may be heated most effectively in a furnace. However, large structural components often require banks of heating torches, electrical strip heaters, or induction or radiant heaters.

A high level of accuracy generally is not required for preheating carbon steels. Although it is important that the work be heated to a minimum temperate, it is acceptable to exceed that temperature by approximately 100°F (40°C). However, this is not the case for quenched and tempered (Q&T) steels, since welding on overheated Q&T steels may be detrimental in the heat-affected zone. Therefore, Q&T steels require that maximum and minimum preheat temperatures be established and closely followed.

When heating the joint to be welded, the AWS D1.1 code requires that the minimum preheat temperature be established at a distance that is at least equal to the thickness of the thickest member, but not less than 3 in. (75 mm) in all directions from the point of welding. To ensure that the full material volume surrounding the joint is heated, it is recommended practice to heat the side opposite of that which is to be welded and to measure the surface temperature adjacent to the joint. Finally, the steel temperature should be checked to verify that the minimum preheat temperature has been established just prior to initiating the arc for each pass.

Local Post Weld Heat Treatment (PWHT)

Local Post Weld Heat Treatment (PWHT) is usually performed for tempering and relaxation of 3residual stresses. Circumferential weld seams can be post weld heat treated by heating a band around the weld. Many factors have an influence on PWHT procedures and the heated width is the most important parameter controlling the effectiveness of local PWHT. However, the determination rules of this parameter are very different in the different codes.


Electrical Resistance Heating

Electrical resistance heating is an in-situ electrical heating technology that uses electricity and applies it into the ground through electrodes. The electrodes can be installed either vertically to about 100 feet or horizontally underneath buildings. Electrical resistance heating enhances the recovery of soils contaminated with volatile and semi-volatile organic compounds (VOCs and SVOCs). Electrical resistance heating assists soil vapor extraction (SVE) by heating the contaminants in the soil. It raises the vapor pressure of VOCs and SVOCs, increasing volatilization and removal. As electrical resistance heating dries the soil, it also creates a source of steam that strips contaminants from soils.

Internal Firing

In this case, the workpieces are heated by gas firing through nozzles. Vessels of suitable dimensions 4and arrangement of openings can be post-weld heat treated by internal firing. It is not advisable to post-weld heat treat vessels that contain internals in this manner. The outside of the vessel must be completely encased in insulating material, and again, at least a 12 point temperature recorder is advisable.

Temporary Furnace

In this case, the heating elements are used to heat the workpiece. Heating can be through resistant 5heating mats placed on a concrete floor or via gas burners placed at each end. The idea is to minimize the air space between the vessel and furnace walls, and they allow for faster heating and cooling.


Normalizing is a type of heat treatment applicable to ferrous metals only. It differs from annealing in that the metal is heated to a higher temperature and then removed from the furnace for air cooling.

The purpose of normalizing is to remove the internal stresses induced by heat treating, welding, casting, forging, forming, or machining. Stress, if not controlled, leads to metal failure; therefore, before hardening steel, you should normalize it first to ensure the maximum desired results.

Usually, low-carbon steels do not re-quire normalizing; however, if these steels are normalized, no harmful effects result. Castings are usually annealed, rather than normalized; however, some castings require the normalizing treatment. Normalized steels are harder and stronger than annealed steels. In the normalized condition, steel is much tougher than in any other structural condition.

Parts subjected to impact and those that require maximum toughness with resistance to external stress are usually normalized. In normalizing, the mass of metal has an influence on the cooling rate and on the resulting structure. Thin pieces cool faster and are harder after normalizing than thick ones. In annealing (furnace cooling), the hardness of the two is about the same.

Description of PWHT Unit

  • Manufacturer of unit: GLOBE (UK)
  • Electric resistance Type heating unit
  • Automatic temperature controllers and with a facility to record Temperature 6 points with 100 % duty cycle.
  • Three-phase power input requirement with 50 Hz
  • TRC (Temperature recorder channels) 6 in numbers
  • Thermal Insulation.
  • Thermocouple attachment unit

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