Post Weld Heat Treatment (Pwht) Inspection Question and Answers

POST WELD HEAT TREATMENT INSPECTION QUESTION AND ANSWERS.

All Questions Answers in accordance of ASME B-31.3 & SAES W-011

1.

WHY PWHT PERFORMS?? (a) To reduce the residual stresses (b)Soften the steel partially (c)Soften the heat affected zone

2.

WHEN REQUIRED PWHT A)

B) C) D) E) F) G) H) I)

More than 20mm Carbon & low alloy steel butt welds requiring PWHT for Process Conditions & Services are as listed in. All caustic soda (NaOH) solutions .B) All monoethanolamine (MEA) solutions (all temperatures). All diglycol amine (DGA) solutions above 138°C design temp. Rich amino diisoprop (ADIP) solutions above 90°C design temp. All lean ADIP solutions above 60°C design temperature. Boiler Deaeratorserv (ambient temp vacuum deaerator = exempt) Hydrogen service for P-No. 3, 4, and 5A/B/C base materials. All diethanolamine (DEA) solutions.

3.

WHAT IS THE INTERNATONAL STANDARD FOR PWHT?

A)

ASME 31.3

4.

What are the documents required for PWHT INSPECTION?

A)

Drawing, line, machine certificate, calibration certificates, Checklist

5.

WHAT ARE THE HEATING/COOLING RATES /SOACKING TIME?

A)

Heating and cooling rates > 316°C shall not exceed 222°C/hr. ÷ weld thickness in inches, but in no case > 222°C/hr. And min soaking temp is 1hr.

6.

Area to be insulated?

A).

each side 300mm. below 150 °C should not remove insulation.

7.

WHAT ARE THE HEAT SOURCES?

A).

Electric resistance heaters, Induction heaters, semi-permanent or permanent furnace s using, gas or oil heaters.

8.

THERMOCOUPLE SPACED?

A)

PIPE DIA -12’’

-1TC

PIPE DIA-ABOVE 12” INCLUDING 24”

-2TC

PIPE DIA 24” and ABOVE

-4TC

9.

RECORDER CALIBRATION IS VALID FOR?

A)

Temperature recorders shall be calibrated every three months and a current calibration sticker shall be maintained on the recorder. The calibration frequency may be extended to 12 months with the approval of Saudi Aramco Inspection

10. WHAT ARE THE TYPES OF TC USED IN PWHT? A)

TYPE K (chromyl - alumel), TYPE J (iron –constantan)

11. HOW TO ATTATCH TC?? A)

TC shall be attached to the component by Capacitor discharge weld. 0.5meter outside from the insulated area.

12. HOW TO PROTECT EXTERNAL AREA SUCH AS FLANGE FACE THREADED BOLTED HOLES, THREADS DURING PWHT? A)

OXIDATION By coating with Deoxaluminite or suitable material.

13. WHAT IS THE NEXT STEP IF DURING PWHT, MACHINES GOT DISCONNECTED WHILE HALF OF THE TASK?. A)

Re perform PWHT once it cooled down. And report it to PID.

14. What is the heating/cooling rate of P5 material? A) i.e. 30.mm Heating & cooling Rate as followed. (222/ Actual wall thickness * 25.4) 222/30*25.4 =187/hr. thus it is calculated as - 200/hr. 15. What is the soaking time of CS material? A. i.e. 25mm Soaking time for CS as Followed. (Actual Wall thickness /25.4*60) (25/25.4*60) = 59mins Thus it is calculated as 60mins.

Prepared By Shajin.P

QCI Sadara. Al Jubail. Kingdom of Saudi Arabia . E- [email protected]