PWHT - [Part 4] PWHT - POINTS TO BE NOTED

General points to be noted in the Job selection for PWHT 

( Examples based on PWHT of pipe joints. )

1. Using a coil, pipes of different schedules should not be connected to PWHT.

2. Using a coil, pipes of different materials should not be heated even though the PWHT cycle is same.

3. The controlling and detecting temperature thermocouple should be taken only from joints only. The thickness of pipe elbow flange etc  will slightly different and tacking thermocouple on the parent material (adjacent to the joint) will cause error in temperature detection as more thickness requires more temperature for heating and in the meantime the less thickness portion will be overheated.

4. Thermocouple tacking shall be done by capacitance discharge method to the possible extend.

5. After the removal of thermocouple the thermocouple tacked area shall be visually inspected to see whether cracks or any defects are present.