ASME VIII Div.1 Table UCS-56-1 PWHT Minimum Holding Time, Thickness over 50mm

[nacer16]

Dear All,

Can someone help me in this matter.

Equipment: Sphere
Design Code: ASME VIII Div.1
Shell thickness: 50.4 mm

PQR qualified according to ASME IX:
Material: SA 537 Cl 1
Coupon thickness: 32mm
Impact Test: YES
PWHT Holding Time: 240 minutes (4hr) (We planned this time to be able to do a 2nd PWHT if there is any repairs and for maintenance after the 1st PWHT).

WPS:
Material: SA 537 Cl 1
Thickness range: 16 to 64 mm
PWHT Minimum Holding Time : 120 minutes according to ASME VIII Div.1 Table UCS-56-1.

Our client rejected the WPS and requested that the Minimum Holding Time should be 135 minutes instead of 120 minutes as per Table UCS-56-1 [2 hr plus 15 min for each additional inch (25 mm) over 2 in. (50 mm)].

Note that Standard Units used are SI millimeters (mm)

In my understanding "15 min for each additional 25 mm over 50 mm" means:

50 mm + 25 mm = 75 mm ------------------------------> + 2hr 15 min = 135 min
50 mm + 25 mm + 25 mm = 100 mm ---------------------> + 2hr 15 min + 15 min = 150 min
50 mm + 25 mm + 25 mm + 25 mm = 125 mm -------------> + 2hr 15 min + 15 min + 15 min = 165 min

In our case the thickness is 50.4 mm, it has not reached 75 mm, so the minimum holding time should be 120 minutes and not 135 minutes !

Am I right or wrong?

Please, enlighten me on the subject because I have to answer as soon as possible to our client.

Thanks in advance

 

[nacer16]

Please correct:

50 mm + 25 mm = 75 mm ------------------------------> 2hr + 15 min = 135 min
50 mm + 25 mm + 25 mm = 100 mm ---------------------> 2hr + 15 min + 15 min = 150 min
50 mm + 25 mm + 25 mm + 25 mm = 125 mm -------------> 2hr + 15 min + 15 min + 15 min = 165 min

Regards

 

[david339933]

120 mins is correct soak time for 2" material (50.8mm), however your maximum qualified thickness of the WPS (64mm) cannot be satisfied with this soak time. You must either limit the WPS maximum qualified thickness to 2" (50.8mm) or increase the PWHT soak time:

64mm - 50.8mm = 13.2mm

13.2mm/25.4mm = .52"

.52" x 15 mins/inch = 7.8 mins.

Therefore minimum soak time for entire qualified thickness should be 128 mins.

 

[Duwe6]

Minimum Soak [holding] Time is "2 hr plus 15 min for each additional inch (25 mm) over 2 in. (50 mm)".

You wrote your own answer; revise the WPS to include this exact phrase. And try not to blame the client's Inspector for pointing out the problems you have caused by not having a properly written WPS for the current job. And david33 has given you the correct method of determining Soak Time for various thicknesses of steel.

 

[nacer16]

david339933,

Thanks alot for your reply and explanation.

Duwe6,

You also, thank you for reply.
Don't worry. I will not blame the client's Inspector. LOL

Regards