m.wasif
Mechanical
- Jan 1, 2017
- 40
I am writing with reference to the Heat Treatment of Air Cooler Headers of Petroleum Refinery.
As per Inspection recommendation, we need to carryout the replacement of both Plug Sheets of Air Cooled HX Headers having design pressure of 21 bar (gauge) and design temperature of 150 degree Celsius. The material of Plug Sheet is ASTM A 516 Grade 70 N having 25mm thickness. The subject job is almost completed in terms of welding and PWHT is still remaining as there is a bit confusion that still PWHT to be carried out or not.
As stated earlier that the subject job is replacement of Air Cooler Headers Plug Sheet only, it means that the Tubes are connected with Tube Sheets (through rolling / expansion) of that Headers whose Plug Sheets need to be replaced.
Based on API 661 Seventh Edition clause 9.2.1, all Carbon Steel and Low Alloy Chromium Steel Air Cooler Headers need to be Post Weld Heat Treated irrelevant of Thickness.
Whereas, Based on UCS 56 of ASME Section VIII Division I, PWHT is not mandatory for 25mm ASTM A 516 Grade 70 Plate.
In view of all above stated matter, you are requested to provide technical guidance in lieu of subject PWHT job that can we still carryout PWHT of Headers Plug Sheets with Tubes inside Tube Sheets of that Headers.
PWHT procedure is as under:
Heating and Cooling Rate of 60 degree Celsius per hour
Soaking Temperature of 600 - 650 degree Celsius
Soaking Time of 60 minutes.
As per Inspection recommendation, we need to carryout the replacement of both Plug Sheets of Air Cooled HX Headers having design pressure of 21 bar (gauge) and design temperature of 150 degree Celsius. The material of Plug Sheet is ASTM A 516 Grade 70 N having 25mm thickness. The subject job is almost completed in terms of welding and PWHT is still remaining as there is a bit confusion that still PWHT to be carried out or not.
As stated earlier that the subject job is replacement of Air Cooler Headers Plug Sheet only, it means that the Tubes are connected with Tube Sheets (through rolling / expansion) of that Headers whose Plug Sheets need to be replaced.
Based on API 661 Seventh Edition clause 9.2.1, all Carbon Steel and Low Alloy Chromium Steel Air Cooler Headers need to be Post Weld Heat Treated irrelevant of Thickness.
Whereas, Based on UCS 56 of ASME Section VIII Division I, PWHT is not mandatory for 25mm ASTM A 516 Grade 70 Plate.
In view of all above stated matter, you are requested to provide technical guidance in lieu of subject PWHT job that can we still carryout PWHT of Headers Plug Sheets with Tubes inside Tube Sheets of that Headers.
PWHT procedure is as under:
Heating and Cooling Rate of 60 degree Celsius per hour
Soaking Temperature of 600 - 650 degree Celsius
Soaking Time of 60 minutes.
