Local PWHT between P-1 and P-4 materials 1

[jtseng123]

Dear all,

I have a revamp project by replacing a 54" nozzle in a vertical tower as shown in the attached sketch.
Does anyone have experience how the PWHT to be proceeded between P-1 and P-4 to prevent damage the carbon steel section which supposedly not to see temp greater than 1200F ?

 

[metengr]

Carbon steel can be safely subjected to a maximum PWHT of 1300 deg F max, where did the 1200 deg F limit develop? Yes, you have several options. Qualify a temper bead WPS for P-No 4 to P-No 1 base material. If this is not an option, you weld the nozzle plate weld prep with 7018, perform PWHT at 1250 deg F, install to complete the remainder of the weld using a P-No 1 (weld prep overlay) to P-No 1 WPS with 7018 at 250 deg F preheat. If you need to perform PWHT for hardness requirements, PWHT can be performed between 1225 to 1275 deg F, based on nominal thickness. Make sure you perform an analysis to ensure no buckling to the tower shell while performing PWHT.

 

[jtseng123]

Metengr, thanks for the reply. There is no technical data I can find beyond 1200F for CS, so we try not to heat CS section beyond 1200F because stress can not be verified, especially this is an existing vessel with large diameter, the new vapor inlet nozzle is located at the bottom of the tall tower, that compressive stress will be governing during circumferential local PWHT band.

The local PWHT will be sub-out, I will check if they can perform temper bead. I also heard of reduced PWHT temp with prolonged duration. Where can I find the guideline ?

 

[metengr]

I also heard of reduced PWHT temp with prolonged duration. Where can I find the guideline ?

Table UCS-56.1 in Section VIII, Div 1.

Regarding maximum PWHT temperature for carbon steel, there is elevated temperature property data above 1200 deg F based on a percentage of YS and TS.

 

[r6155]

Be careful with transition between 1,25” shell thk SA 516-70 (138 MPa) and 2,5” insert plate SA-387 12 CL 2 (123 MPa), considering design temp. 200ºC

I prefer insert plate SA-516-70, round and not square plate. Nozzle 54” welded as per figure UW-16.1 (a). In this case PWHT is not required, only preheat to 120ºC.

Regards
r6155

 

[jtseng123]

r6155, your probably mess up my post with other people's post. In my case I have inlet temp close temp 1000F, and expand into a huge vessel space. Insert plate to be Cr-Mo and we do not use round insert from construction point of view.

 

[r6155]

jtseng123 I have read all post.
What is your design metal temperature?, 1000ºF?

See ASME II Part D notes G10, S1 and T2 for SA-516 70, and S4 and T5 for SA-387 12 Class 2

Regards
R6155