Monday, September 6, 2010

[MW:6886] MW: 6833] MW: 6831] tempering temperature of P4 material

Takseen,

Thank you for sending me the required specification, Aramco-32-SAMSS-004 :-Manufacture of Pressure Vessels-2009 version. Clause 15.4 which applies for PWHT  is basically same in 2005 version which I had referred in my earlier email. This specification is clear with respect to PWHT temperature:-

  •      it should not be more than Mill Tempering Temperature or 700 deg C max for Cr-Mo, SA-387-Gr 12 Cl2 steel.
 
The  plates were procured with Mill Tempering temperature of 660 deg C, while later Aramco came back with the recommendation that plates should have undergone tempering at 680 deg C minimum. Looking at the overall scenario redoing the simulation HT at 680 deg C as recommended in my earlier email (see below) could be a feasible solution for your organization.
 
Is the PQR qualified for this project, if so, what're the results?i.e Tensile , Impact, and Hardness.What was the PWHT cycle followed? Was this PQR qualified on the present plates, tempered at 660 degC.If not what's the tempering details of the PQR plates. Highlighting these information would be helpful for a good solution of this problem
 
I've attached the queries on the similar issue posted in another forum. Use these back up information as a help to solve your problem. 
 
Appreciate your response.
 
Thanks. 
 

Pradip Goswami,P.Eng.
Welding & Metallurgical Engineer/Specialist
Ontario Power Generation Inc.
Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net


________________________________

From: pgoswami [mailto:pgoswami@quickclic.net]
Sent: Saturday, September 04, 2010 12:15 AM
To: 'materials-welding@googlegroups.com'
Subject: MW: 6833] MW: 6831] tempering temperature of P4 material



Takseen,

Your query seems to be related to Aramco-32-SAMSS-004 :-Manufacture of Pressure Vessels. The PWHT requirement from this specification is as mentioned below. In addition the API requirements on PWHT for similar equipments are as mentioned below. I am not sure if Aramco calls for API recommended practices to be followed. In case of any discrepancy between two specifications" client's decision if final. The extracts from Aramco and API documents are as follows:-

1.      Aramco-32-SAMSS-004 :-Manufacture of Pressure Vessels:-

 Clause 15.4: The maximum postweld heat treating soaking temperature for quenched and tempered carbon steel and C-½ Mo materials shall not exceed the temperature at which the test pieces were heat treated, as shown on the Mill Test Reports or 650°C maximum for carbon steel, 690°C maximum for C-½ Mo and 700°C for low chrome alloy steels.

2.      API-934E -Recommended Practice for Materials and Fabrication of 1¼Cr-½Mo Steel Pressure Vessels for Service above 825°F (441°C).

Final PWHT:-PWHT shall comply with the minimum requirements of the applicable code except that all 1¼Cr-½Mo and 1Cr-½Mo weld joints shall be PWHT at a minimum of 1225°F (660°C), and the recommended post weld heat treat range is 1225-1275°F (665-690°C). Post weld heat treatment temperatures above 1275°F should be considered when the primary failure mechanism for the welds is creep, but these steels should not be post weld heat treated at temperatures above 1350°F (730°C). The use of higher post weld heat treat temperatures helps prevent reheat cracking, but higher post weld heat treating may result in lower steel tensile strength. The post weld heat treatment used will affect the steel fracture toughness, and this should be taken into account because many refinery pressure vessels are pressurized at low temperatures during start-up and shut-down.

 Coming back to your query:-

Sec-VIII, DIV-1 requirement for min PWHT on SA-387-Gr 12 Cl2 ( 1Cr-0.5Mo steel) is 650 degC. However based on the tempering temperature adopted in the mill , during plate manufacturing , fabricators may have allowance to choose high PWHT temperature than what's specified by code, However PWHT  temperature  preferably shall  preferably be lower than Tempering temperature done at the mill. 

If the plates i.e 65,70, 80 mm thick were  purchased with tempering  done at 660 deg C , then it's a non conformance to ARAMCO specification. As per my opinion it could be salvaged as such:-

1.      Perform simulation HT  of plates @ 680 deg C  for each thickness i.e 65,70, 80 .The  soak time as required by ARAMCO, or typically total soak time as per the code for each thickness  + 2 repairs (One Shop and another in the later years when the vessel is in service).

2.      If the mill  MTR of the plates tempered @ 660 deg C show good mechanical properties, then simulation HT at 680 deg C  may be a success.

3.      If the results are encouraging use these results as the basis for final PWHT, i.e 650deg C minimum as per Sec-VIII, DIV-1 or more.

4.      NOTE:- If your organization have to redo the testing as stated above , welding procedures qualification(if any), production coupon plate welding all have to be done with extreme control.

If the results of simulation test @ 680deg C are not a success, then you've to convince the client to accept the scenario based on the tempering results done at 660 deg C at the mill.

I hope this would help you and guide further on this issue. If  there're more Aramco requirements, feel free to share.

Thanks.



Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Ontario Power Generation Inc.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net





________________________________

From: pgoswami [mailto:pgoswami@quickclic.net]
Sent: Friday, September 03, 2010 6:49 AM
To: 't_ingole@yahoo.co.in'
Subject: FW: 6833] MW: 6831] tempering temperature of P4 material

Hi did you have a chance to look at my query.



Thanks.



Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Ontario Power Generation Inc.

Email-pgoswami@sympatico.ca, <mailto:sympatico.capgoswami@quickclic.net>

pgoswami@quickclic.net





________________________________

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of GOSWAMI Pradip -THERMAL
Sent: Thursday, September 02, 2010 10:36 AM
To: materials-welding@googlegroups.com
Subject: [MW:6833] MW: 6831] tempering temperature of P4 material

Takseen,

Aramco has tons of design specifications. I've many of them. Which specification applies to your project? What they're asking for is based on good common sense engineering.

If you could let me know the specification no or email  me the specification  @ my personal email as below, I would get back to you.


Thanks.



Pradip Goswami,P.Eng.
Welding & Metallurgical Engineer/Specialist
Ontario Power Generation Inc.
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net



From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of THAKSEN INGOLE
Sent: Thursday, September 02, 2010 5:57 AM
To: material welding
Subject: [MW:6831] tempering temperature of P4 material




Dear all

There is a clause in Saudi Aramco documents stating as below

The maximum PWHT soaking temperature for quenched and tempered carbon steel and C-1/2Mo shall not exceed the temperature at which the test pieces were heat treated as shown on mill test reports or 650 deg C max for carbon steel ,690 deg C max for C-1/2 Mo and 700 for low Chrome alloy.

Our material is SA-387-Gr 12 cl2 (C -1/2Mo) which is P4 material. The min PWHT temp as per code (VIII Div 1-U stamp) is 650 deg C.

Now aramco has commented on our documents that they need a PWHT temperature to be 25 deg C less than tempering temperature as specified on MTC for the plates. So we need to have a tempering temp of min 680 deg C  so we can carry out the PWHT at 650 deg C but the plates MTC shows the tempering temp as 660 so we are 15-20 deg below. The plates are already purchased which are 65,70,80 mm thick.

My first query is no where in the aramco document we can find a clause of have PWHT temp 25 deg C less than tempering then what is the reason for asking this requirement.


What is the solution that we can offer them.

Regards
Thaksen  



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