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PWHT Pressure Vessels

PWHT Pressure Vessels

PWHT Pressure Vessels

(OP)
My task is to perform PWHT on a pressure vessel working with H2S after repair by welding of cavities appeared after corrosion and erosion. Defects were repaired by welding plating temper bead welding method .
dimensions are 68 m high, 5m diameter, wall thickness between 65 and 70 mm, low alloy steel.
Local PWHT shall be performed by the method of heating with electrical heaters in each circular band containing the defects repaired.
My question is: what is the minimum surface repaired which is not mandatory to be PWHT?
For example, a cavity repaired with dimensions 100mm long x 300mm wide x 15mm deep ; this means 0.03m square
This requires PWHT ?

The pressure vessel is located in a plant in Romania.
I am the contractor for heat treatment and I have done PWHT in the past on similar vessels here.
For repairs performed two years ago, project engineer requires PWHT for repaired areas exceeding 0.064m square, but now he asks for all areas regardless of the surface. He says there is a stipulation in ASME that require PWHT for all repairs to pressure vessels working with H2S.
NDT inspections , Destructive Testing , NACE tests in Germany and UK , all were made ; finite element method calculations are made to establish the size of soak band and more .
 
Igor Gradinarescu Steel Heating Services

RE: PWHT Pressure Vessels

Igor,
You mention ASME in the later part of your post - are you working to ASME VIII Div 1 ?
You mention "low alloy steel" - list the actual material, much easier for someone to assist.
There are some very experienced PV personnel who are much more knowledgeable than me on this forum so will leave for them to respond to your request.
Cheers,
DD

PS to Forum Members: Some people get upset at double posting but I would think this is a perfect example of something that could fall into either "Boiler & Pressure Vessel Engineering" or alternatively "ASME Code issues" ???

RE: PWHT Pressure Vessels

Post weld heat treatment in ASME Boiler and Pressure Vessel Code is based on thickness of either the deposited weld or base material being welded. The chemical composition of the base material will control the need for PWHT. PWHT is not based on area or size of the repair.

It is ok to post in another forum as long as a link is established so responses can be viewed in one forum and the other. Not all responders view the same forums.

RE: PWHT Pressure Vessels

The section you referenced deals with surface area limits using the temper bead weld repair method only for Section III vessels and nothing to do with PWHT, and Section VIII, Div 1 vessels.

RE: PWHT Pressure Vessels

(OP)
Please forgive me for my poor English, but I mentioned that the defects were repaired with temper bead welding method.
My misunderstanding is that two years ago was valid Section 3 and now no longer valid, in view of project engineering.
Anyway I'll do my job as he is asking me.

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