Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

How many times PWHT can be done

How many times PWHT can be done

How many times PWHT can be done

Hello All;

A pressure vessel was constructed with SA 516 Gr.70 has undergone PWHT initially in 1975.
How many times the vessel could undergo repair & PWHT in its lifetime? Are there any maximum times can anyone do PWHT?
Will metallurgical changes occur during subsequent PWHT?
Where I can find supportive answers in terms of metallurgy and codes?

Appreciate all your commentsdazed

RE: How many times PWHT can be done

Check API 510 if you are re-rating the vessel.


RE: How many times PWHT can be done

If it exists and can be located, the history docket from original construction will be helpful.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: How many times PWHT can be done

With the exception of pressure vessels subject to impact testing per ASME VIII, Div.1, ASME IX and the NBIC, there are no limits imposed. I have practical experience of 4 PWHT cycles with SA-516 up to 12 hrs total time at temperature below 1200F without adversely affecting mechanical properties.

At 1300 F I have seen reduction of mechanical properties below the specified minimums, especially the deposited weld metal, with as little as 2 hrs hold time.

RE: How many times PWHT can be done

You can look at ISO/TR 14745 Welding - Post-weld heat treatment parameters for steels.
There is some info about holding time and temperature, multiple heating cycles, Hollomon-Jaffe parameter and so on.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Research Report - How Engineers are Using Remote Access
Remote access enables engineers to work from anywhere provided they have an internet connection. We surveyed our audience of engineers, designers and product managers to learn how they use remote access within their organizations. We wanted to know which industries have adopted remote access, which software they are using, and what features matter most. Download Now
eBook - Managing the Context of Product Complexity Using the Digital Twin
Keeping track of changes to complex products is difficult—think Aerospace & Defense equipment, new generations of commercial aircraft, and software-based automobiles. A new way to managing the digital context of the physical product is required and the answer is the Digital Twin. This ebook explores the opportunity available for Operations and Maintenance for the Digital Twin. Download Now
White Paper - Trends in Industrial Filtration
Substantial progress has been made in filtration technologies in recent years. New filter media materials, designs and processes have led to filters that are more efficient, reliable, compact and longer lasting. This white paper will discuss the various trends that are impacting operational responsibilities of MROs today and the resources that are available for staying up-to-date on the latest filtration solutions. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close