PWHT of P4 & P5 inaccordance with ASME B31.3

By Gerry Date 07-19-2007 08:51

According to ASME B31.3 2004 some minimum heat treatment temperatures (PWHT temperatures) listed in this code may be higher that minimum tempering temperatures required by the ASTM (or ASME) specifications; others have a minimum required PWHT equal to the minimum tempering temperature of the material specification, because ASTM material specifications do not take into consideration the application when PWHT condition applies.

For these normalized and tempered materials there is a possibility of reducing the mechanical properties of the base material by PWHT, and the tempering is destroyed if PWHT temperature is higher than the tempering temperature, invalidating the test results of the Material Test Report.

ASME also requires for high pressure piping, for fabrication, that the maximum PWHT temperature be at least 30°C below the minimum tempering temperature.

For some ASTM materials ASME B31.3 2004 requires that the PWHT used in manufacture of materials must be in accordance with ASME B31.3 2004.

Now the questions:

How does you handle such materials to prove conformance to code?
Do you require simulated PWHT cycles by the material manufacturer, simulated PWHT cycles by the purchaser or do you specify higher temper temperatures and limit the max PWHT?

By chall

Date 07-19-2007 11:49

I'm having a hard time following your comments. The specified PWHT temperatures are based on staying below the "lower transformation temperature". I don't remember anything in B31.3 that addresses the tempering temperature range.

To prove Code acceptability, a review of the MTR against ASME Section IIA is sufficient.

For ordering purposes, we state clearly on the PO: "The material must conform to (for example) SA335-P22; an MTR (traceable to the material supplied) must accompany the material delivery." We do not specify technical details, related to how to produce the product, to the supplier.

For ASTM materials: If they are used in an ASME Code "pressure boundary" appication, they must be acceptable (first) by the code of construction, and also be listed in QW-422 of Section IX. If either requirement is not met, the material is not used by us.

Charles

By jon20013 (*****)

Date 07-19-2007 13:29

I agree with Charles except would like to add in from my own personal experience; for the simulated PWHT, we just purchased an enormous quantity of steel that will be subjected to hot forming and PWHT. We had our material supplier perform the simulated heat treatments during normal mill testing and these were included in the MTR's. It was important to have this done so we would know the mechanical properties of the materials before running our PQR's.

By js55

Date 07-19-2007 14:15

I'm with Charles, I'm not really sure what your concern is. Sometimes I think we over think. And make things too complicated.
You verify your MTR's. You do a weld. You cook it. You pull it. You bend it. And even smack it with a hammer. You can smack it cold, pull it hot, do it with representations of long periods of time if you wish, and even dip it stuff that will eat it. The code has been complied with and then some. And you have a reasonable idea of at least the static properties of the material.
In jon's case, unless I misunderstood, its a question of information and financial and delivery schedule protection. Not wether or not you can confirm code compliance.

By js55

Date 07-19-2007 14:18

Oh, and I also think that you do not invalidate the results of the MTR. The MTR is a statement of the material as delivered. Nothing else. What you really do is 'addenda' the properties of the material with PQR results. Thats why you run a PQR.

By Gerry Date 07-23-2007 15:08

Hi
thanks for your reply's.
When you order's e.g. SA 182 F11 the material may be tempered at 680 degrees celcius. When PWHT must be do in accordance with ASME B31.3, the holding temperature must be between 704 and 746 degrees celcius, thus you exceed the temper temperature.

By js55

Date 07-23-2007 15:26

Agreed.
And what does that mean?
Or, do you consider this a problem?