PWHT Per ASME B&PVC Sec. VIII Div 2 ?

[mimo3216]

Per ASME Sec VIII Div II I am required to PWHT my new nozzle to my existing pressure vessel. Original "layered" pressure vessel material is MLP1146 (single layer thickness = 1/4" and 9/32" using Grade A min tensile = 105,000 psi and min yield strength = 82,500 psi). New nozzle material is SA-105. How do I find the temperature range, heating/soaking time, rate of heating, rate of cooling, etc needed to describe to the welders how to PWHT? The weld details that I am using to join these materials is Figure 4.13.9(a) from Division 2. Also does anyone happen to know filler material to use for this weld joining the different materials. I know very little about the MLP1146 material.

 

[metengr]

mimo3216;
Are you installing a new nozzle into an existing Section VIII, Div 2 vessel???? The MLP1146 means nothing in terms of steel specification. You need to review the data report for this vessel and determine the SA material specification.

 

[mimo3216]

The existing vessel is not a stamped vessel. It was built back in the '60s. Per customer requirements repairs and alterations must be in accordance with the current ASME code. When plugging in existing dimensions and original design temperature and pressure the existing pressure vessel does not meet the Division 1 requirements for shell thickness. Since we have data reports I then dug into Division 2 for alternative rules to pv design. Back in '98 the customer did a design package that proved the same results but would not take on the layered vessel repair or was not provided the funds to make the alteration. Now we are at the point of customer having funds and wanting this pressure vessel to work to the MAWP. Original design pressure is 5000 psi but even now the vessel dimensions won't reach that pressure (close thou). I have their original specification sheet for the MLP1146 - it's a high strength low-alloy steel plate. It does state that material furnished under theis spec shall conform to the applicable requirements of the current edition of Specs for General Requirements for Delivery of Rolled Steel Plates of Flange and Firebox Qualities, ASTM A20. So do I consider this a carbon steel for weld properties.

 

[metengr]

it's a high strength low-alloy steel plate. It does state that material furnished under theis spec shall conform to the applicable requirements of the current edition of Specs for General Requirements for Delivery of Rolled Steel Plates of Flange and Firebox Qualities, ASTM A20. So do I consider this a carbon steel for weld properties.

Bad assumption. What is the ASME SA number and Grade for this steel? You need this to determine the P-No for welding procedure qualification. Second,

Per customer requirements repairs and alterations must be in accordance with the current ASME code.

You may be at significant risk with this vessel especially if you intend to want to go back to the original MAWP> What if current Code rules imply a much lower MAWP? What are you going to do?????

Also, for re-rating purposes you should be following either the National Board Inspection Code (NB-23) or API 510. If the vessel is insured, I can guarantee that this vessel will need to be altered to either Code above in addition to following the code of construction requirements.

 

[mimo3216]

It doesn't tell any of that information. That's why I was asking if anyone knew anything about this MLP1146. That number may not help anyone, but that is what the original design company called it.

Original design pressure was 5000 psi. When vessel was reanalyzed in the '80s by the '77 Division 2 code the vessels were de-rated to 4200 psig due to the 1" nozzles not being able to handle that much pressure. Here we are today and analysis performed by '07 Division 2 code the vessels could be rated to 4700 psi however the 1" nozzles needed to be re-designed because the original thickness could not handle that much pressure. That is pretty much our job - the nozzles would not hold up so we needed to design new ones that would. I have followed Div. 2 rules and the nozzle is much bigger than the original one (10.5" od, 1.0" id, 10" tall - new nozzle). I chose SA105 due to high stress values needed and availability. Now I need to weld them together and need help on post weld heat treat.

 

[curtis2004]

mimo3216,

If your customer wants "...repairs and alterations must be in accordance with the current ASME code", I'm afraid your only option will be to order a new vessel with "U" stamp. If the vessel wasn't built in accordance to ASME code in the first place how you can repair it to confirm the code? Material used dosn't confirm. Shop where it was built doesn't confirm. Quality procedures wasn't followed. MAWP even doesn't meet working pressure.
How much does it cost to replace it?

Regards,

curtis

 

[metengr]

mimo3216;
I would go back to the client and recommend they retire this vessel because it does not meet Code requirements for a pressure vessel. You are at significant risk with this job because heaven fobid if there is a failure, your company will be on the hook trying to defend yourselves in court with nothing to stand on in terms of design.

What is the condition of the high strength low alloy steel layers? Has there been a proper condition assessment of the entire vessel to ensure adequate condition from past operation and safety margins for the MAWP.

PWHT is the least of your worries. And as I stated before you need to know the specific chemical composition and mechanical properties of the high strength low alloy steel so that you can determine if PWHT is for P-No 1, or other. Using steel is equivalent too or nearly the same as is not good enough for a re-rating.