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Pipe Postweld Heating Treatment PWHT Stress Reliving

Pipe Postweld Heating Treatment PWHT Stress Reliving


Induction preheating PWHT machine is widely used for pipe/tube weld peheat and pwht, stress reliving and so on. 

Welding   is one of the most critical processes in the manufacture of pressure vessels like the boiler of a thermal power plant. The temperature of the molten weld pool during the process is in the range of 2000 deg C. The heat increase is rapid and instantaneous. When this small strip of molten pool cools down the shrinkage results in thermal stresses that are locked up inside the metal. This also can change the macrostructure of the steel.

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

PWHT consists of heating the metal after the welding process in a controlled   manner to temperature below the first transformation point, soaking at that   temperature for a sufficiently long time, and cooling at controlled rates. 

Induction heating is one method that is gaining popularity even though the cost is high. This is a more welder friendly process. Unlike resistance heating only the pipe becomes hot. The temperature gradients are uniform across the   thickness. 

The heating power is from 10KW ~ 120KW

Model: 10KW, 20KW, 40KW, 60KW, 80KW, 120KW and so on.

Heating temperature: 0 ~ 900 C

Max heating temperature: 900 C

The pipe / tube diameter: 50 ~ 2000 mm

Heating coil: Clamp coil or induction heating blanket  

The induction weld preheating machine include:

1. induction heating power source.

2. SOFT Induction Heating Cable

3.  Extend cable

4. K type thermocouple

5. Paper / Paperless recorder and so on.

 

Compare with ceramic heater and frame heater. It has more advantage.

1. Quickly heating speed and unfirom heating temperature

2. Energy   saving without any pollution

3. Long working time and more stable

4. Touch screen and PLC control, Easy to operate

5. Can suitable for different welding condition

  



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