PWHT BS 1501-151-28A 1

[johnnymist2003]

Hi all,

we have modifications to do on two Separator Vessels, and two Columns.The vessels and columns have been in service since 1967.They were constructed from BS 1501-151-28A material.All of them are in wet sour service.When constructed, none of them were post weld heat treated.Code data book information is sketchy, with very little in the way of test certificates for the plates.We will be welding onto the vessels, and PWHT will be required for the mods.We wish to get a confidence level on the risk of PWHT of the exiting plates and the effect the PWHT will have on the mechanical properties of the plate.We are unable to get a test specimen from the vessels as they are in service.To remove a test piece during the shutdown, PWHT and test and then have a decrease in mechanical strength which would result in de-rating the vessel constitutes too high a risk.Does anybody have any experience in this regard?Can anyone provide any literature references which will provide some guidance?
Any help would be much appreciated.
Thank you
John

 

[andyenergy]

I notice that you havent had a response to this query. Hopefully this might help kick things off.

BS 1501 151 28A is silicon killed boiler plate material with the following composition:
C 0.25% max
Si 0.40 % max
Mn not specified
S 0.050 max
P 0.050 max

Ni 0.40
Cr 0.25
Mo 0.15
Cu 0.40

These latter four should totoal 0.80 max

Specified Mechanical properties are:

UTS 24 - 28 tsi
Yield 12 tsi min
Elongation 25% (for material under 3/8 inch min elongation values are reduced by 3)

This steel would be considered weldable, but vessel code requirements would dictate whether PWHT was required or not I'm not familiar enough with wet sour conditions to offer further advice in this regard, but a stress relief in the temperature range 580 - 620 (which is the range specified in BS 5500 - pressure vessels for thicknesses greate than 30 mm) would not produce any significant reduction in mechanical properties. Application of a preheat for thicknesses of greater than 30 mm will be required according to BS 5500, but again dictated by the relevant code.

Sorry if this is a bit vague, but hope it helps

 

[Carburize]

Copy of what I just posted on the Corrosion Forum ---

There is data on the effects of various PWHT cycles on BS 1501 151 in

"The influence of Stress Relief on the Properties of C and C-Mn Pressure Vessel Plate Steels"
by
Gulvin, Scott, Haddrill and Glen.

Journal of the West of Scotland Iron and Steel Institute, 1972 -73 Vol 80.