PWHT of Amine Regenerator column

[rampokala]

Dear All,

We are going to carry out weld repairs on our Amine regenerator column during shutdown. Repair will be carried out by weld build up due to internal corrosion. At the same time there is a modification in the column we are adding two 12"Dia nozzles. at 1meter higher elevation from the weld repair location. Due to service requirement PWHT is mandatory. In order to reduce shutdown window there is a proposal to carry out carry out PWHT on newly added 2 nozzles and the weld repair location at the same time. Is it allowed to carry out the PWHT at the same time?

At Nozzles PWHT will be carried out by Bulls-eye technique and at the weld repair location PWHT will be carried out by circumferential band heating of the complete column.

Is there going to be any issue with the deformation etc. Kindly share your experience.
the details of the column are as follows:

1. Material: A516 Gr.55
2. Diameter: 4meter
3. Height: 20 meter
4. Thickness: 11mm
5. location of nozzle addition: 4 meter from top
6. location of the weld repair: 5meter from top

Appreciate your advises.

with best regards
Ram Pokala

 

[APItips]

Yes, it can be done as long as paragraph UW 40 a)8) is met and during the holding period, there shall not be a greater difference than 150°F (83°C) between the highest and lowest temperature throughout the portion of the vessel being heated .Paragraph UCS 56 d)3).

 

[metengr]

PWHT of an in-service vessel can be done with multiple locations provided an engineering analysis is performed to ensure no bucking or permanent deformation of the vessel itself as a result of local PWHT exposure. You should have an analysis performed to determine if local temporary supports are required during execution of PWHT.

 

[pradipgoswami]

Hi Rampakola,

The diameter of the vessel is large and wall thickness is small. Hence as sugegsted by Metengr, PWHT with temeporary support and an engineering analysis to get an idea reg the extent of buckling would be a good way to go.

Regular PWHT @ 600-620 Deg C could cause deformation.Alternatively low temperature PWHT as per UCS-56.1 could be an option also.However in amine service API-RP945 and many clients' specifications calls for 200 HB(max) hardness in the weld and HAZ.Should hardness control is a requirement a new WPS/PQR may be required.

PWHT with resistance heating blanket would be the way to go. You may incorporate multiple TCs for different weld areas in one PWHT cycle as per AWS D-10.10.

Thanks.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario, Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299