PWHT Pressure Vessel

Following things are required for a deep analysis,

• What is the code of construction?

• What is the material specification aka Material Of Construction?

Why would you not test every area repaired?

Is a small area more likely to be perfect than a larger one ?

Some common sense must be applied here.

TEST ALL AND EVERY SIZE REPAIR completely.

To do less is negligence.

The product is H2S, do you accept any risk of a leak from an uninspected repair ?

Good Luck with that.

Inspect them all, to standard, and document the tests.

"My task is to perform PWHT" . Do your job. Completely.

Major embarassment.

My mind read Test as opposed to Treat.

Sincere apologies to all.

As I understand it, you are the heat treatment contractor, not the pressure vessel engineer. I don't know where this vessel is located, so I'm writing from a US perspective.

1. H2S exposure receives a lot of attention from the American Petroleum Institute (API) and NACE. The person or persons directing the repair work should be expert in the subject.

2. The rules for repair of pressure vessels are not necessarily the same as those for the original construction. The owner's agent and the insurer usually work together to develop a plan.

3. You, as the heat treatment contractor, should be expected to perform PWHT as and where directed. It is not your responsibility to determine where to treat.

P.S. Hopefully, the engineers will consider the effect of the lowered strength of the column while heat treatment is in progress, especially if done near the bottom of the column.

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 1m 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 , NACE tests in Germany and UK , all were made ; finite element method calculations are made to establish the size of soak band and more . I think you're right , I have to executing correctly what they tells me.Please forgive my poor English .

To avoid misunderstadings I will reply in your language:

Tensiunile interne consecinta a sudurii nu depind de suprafata sudata ci de cantitatea de sudura utilizata si mai ales de viteza de racire locala.

Asa ca fie mare, fie mica, zona trebue detensionata intru cat altfel riscul de fisurare este serios in special in zonele unde structura cristalina a bazei a fost afectata si care sunt dealtfel zonele unde tensiunile sunt maximale.

Thanks for your answer in Romanian

I think I found an answer here in ASME Section III Division 1 Subsection NC .

You don't mention, "he asks for all areas regardless of the surface".

He is the customer, after all. If he requires PWHT on all welds, that supersedes any specification, unless he signs of on the change in his requirements.

ASME, as most codes, are minimum requirements to be used in all conditions. Other conditions, such as H2S exposure, may impose more stringent requirements. That is why everything must be taken into account.

All post fabrication welding will require PWHT.

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 III and now no longer valid, in view of project engineer. Anyway I'll do my job as he is asking me.
Thanks for the advice and explanations that you gave it to me. Now I understand that you have to always take precautions so that you can be covered, generally speaking.