Bulge P-91 Pipe after PWHT

[pradip kumar Sil]

Dear Expert,

In P91 Material ( HRSG header Joint ) after pwht one joint is bulge.We did  Preheating ,Welding , Post Heating,& PWHT in proper way.

Can anybody explain why this bulge occurs & remedy.

During fit-up inspection & weld visual inspection all round the joint is perfect but after PWHT pipe is bulge 140 mm away from the   weld ment

Pic Attached

Regards,

Pradip

[shanmuganathan .subbiah]

Dear 

Both end closed or not during PWHT?

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Regards

SHANMUGANATHAN SUBBIAH

AIB- Vincotte International & Partners LLC

PO.Box-420, PC -116

MAF, Sultanate of Oman

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[pradip kumar Sil]

It is closed

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[VHEER RAJHU]

Mr shanmugan,

Job is kept in vertical condition where and when the job is heated locally the material softens  at that particular area where all the weight of the job is acted on that softened area which leads to bulging locally

Preferred to do PWHT HORIZONTALLY

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[pradip kumar Sil]

It is not possible to do PWHT horizontally because spool piece is welded at location

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[Thompson, Dennis]

Hi Pradap,

 

Please email us a drawing of the heater and thermocouple arrangement that was employed for your PWHT, along with a copy of your temperature-time chart.  Both are needed to help diagnose your failure.

 

Regards,

Dennis Thompson, P. E.

Team IHT Technical Support Manager

973-885-2148

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[Rems Okonkwo]

Hello Pradip,

I believe the bulging did not occur on the weld zone but rather on the pipe and I believe that this area where part of the PWHT heat band.

There are two possible thing that will lead to this bulge.

1. The pipe collapsing on its weight during the PWHT as a result of softening effect.

2. The PWHT soaking temperature might be greater than the material heat treatment during the forming process which will also lead to softening and both 1&2 combining effect can lead to this bulge.

You will have to find a way to support the collapsing weight of the vertical pipe and also check if you have exceeded during the PWHT the tempering temperature during the pipe forming.

Rems Okonkwo

IWE Nigeria

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[pradip kumar Sil]

Dear Dennis,

Pls find the PWHT chart & in 10" we used two nos of thermocouple with equal distance i.e 180 degree. We checked the hardness in the weldment as well as HAZ zone & found 210 to 238 HB but in bulge zone ( Parent Material ) which is 140 mm away from weldment is coming 155 to 175 HB.

Thanks in advance.

Regards,

Pradip

[Thompson, Dennis]

Hi Pradip,

 

Thanks for emailing us the temperature-time chart.

 

However, we still need a sketch or drawing of the heater and thermocouple arrangement.

 

You stated that you utilized 2 thermocouples, 180^o apart.  However, where were they relative to their heaters and relative to the header-tube weld?

 

Specifically:

 

1.      What are the diameters and thicknesses of the header and tube(s)?

2.      What size heaters were attached to the header, and where were they and their control thermocouples relative to the location of the header-tube weld?

3.      What size heater was attached to the tube, and where was it and its thermocouple relative to the header-tube weld?

4.      The fact that the softened, bulged section of tube was 140 mm from the header-tube weld indicates that the temperature of the tube at that location may have exceeded the PWHT soak temperature.

5.      Your sketch/drawing of heater sizes and thermocouple locations will help diagnose the cause of your problem.

 

Regards,

Dennis

[pradip kumar Sil]

Dear Mr. Rems,

Bulge happened just outside PWHT heat band.Pipe thickness is 12.70mm & did soaking 2 hrs. I already attached Time temp. chart. Header has eight nos of pipe but during PWHT only two pipes are bulge.

Thanks & Regards,

Pradip  

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[Kannayeram Gnanapandithan]

Why longer soaking for 12.7mm thick. The Hardness is very less on the bulged area, may be over heating?

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[pradip kumar Sil]

Pls find attached typical arrangement. Pipe is 10" with 12.7mm thickness

[george....@gr.bureauveritas.com]

Why you do not perform a calculation using as allowable stress the stress value at the PwhT temperature? Consider the Euler case which is closer to your configuration

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From: pradip kumar Sil Sent: Τρίτη, 24 Νοεμβρίου 2015 - 12:42 To: materials-welding Reply To: material...@googlegroups.com

Subject: Re: [MW:23914] Bulge P-91 Pipe after PWHT

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[george....@gr.bureauveritas.com]

You are suspecting that the material went in the creep area?

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From: Thompson, Dennis Sent: Τρίτη, 24 Νοεμβρίου 2015 - 14:08 To: material...@googlegroups.com; prad...@gmail.com Reply To: material...@googlegroups.com Subject: RE: [MW:23915] Bulge P-91 Pipe after PWHT

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[george....@gr.bureauveritas.com]

Are you sure that no lamination was in place?

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From: pradip kumar Sil Sent: Τετάρτη, 25 Νοεμβρίου 2015 - 04:50 To: Thompson, Dennis Reply To: material...@googlegroups.com Cc: materials-welding Subject: Re: [MW:23921] Bulge P-91 Pipe after PWHT

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[pradip kumar Sil]

How we will calculate allowable stress the stress value at the PwhT temperature by using Euler Case

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[pgoswami]

Pradip,

 

Something definitely had gone wrong with the PWHT process causing the headers to bulge. I’ve tried to put all of your back and forth correspondence in one place. The root cause analysis looks to me are as follows:-

 

• The PWHT temperature is not very clear, but something in the vicinity of 760-780 Deg C and of 2hrs of soaking time for ½” wall thickness is high.
• Please follow Sec-I guidelines (as below)
• The PWHT chart should be very clear. It’s not clear from the PWHT chart what was the temperature adopted vs the soaking time .Needs to be specified in the chart
• I’m not sure, but from the hand drawn sketch, it looks two heating pads were overlapped. If so it definitely would add to overheating .
• It’s not a mandatory requirement. However   as per D-10.10 it’s advisable to place additional thermocouples in the soaking and heating zone to monitor PWHT temperature accurately. This is required for CSEF steels such as Grade -91 Or else over tempering would destroy the Creep Resistance of this steel.
• I would think one needs to discuss these issues upfront with the heat treaters, then approve the PWHT procedure and monitor well in the field.

 

I hope the attached information would help you.

 

Thanks.

 

 

Pradip Goswami, P.Eng,IWE
Welding & Metallurgical Engineering Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

pgos...@quickclic.net

pradip....@gmail.com

All provided answer are personal opinions or personal judgements only. It's not connected with any employers by any means. 

 

 

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Subject: Re: [MW:23914] Bulge P-91 Pipe after PWHT

 

Dear Dennis,

Pls find the PWHT chart & in 10" we used two nos of thermocouple with equal distance i.e 180 degree. We checked the hardness in the weldment as well as HAZ zone & found 210 to 238 HB (This is fine)  but in bulge zone ( Parent Material ) which is 140 mm away from weldment is coming 155 to 175 HB.—Over tempered, Poor Creep Strength

Thanks in advance.

Regards,

Pradip

 

 

Dear Mr. Rems, Bulge happened just outside PWHT heat band. Pipe thickness is 12.70mm & did soaking 2 hrs. I already attached Time temp. chart. Header has eight nos of pipe but during PWHT only two pipes are bulge. Thanks & Regards, Pradip   From: pradip kumar Sil

Sent: Τρίτη, 24 Νοεμβρίου 2015 - 12:42 To: materials-welding Reply To: material...@googlegroups.com Subject: Re: [MW:23914] Bulge P-91 Pipe after PWHT

It is not possible to do PWHT horizontally because spool piece is welded at location

 

 

 

On Tue, Nov 24, 2015 at 12:26 PM, pradip kumar Sil <prad...@gmail.com> wrote:

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[pradip kumar Sil]

Dear Sir,

I already discussed with heat Treater regarding this matter & found thermocouple is placed in the middle so there is no overheating Chances.  Thermocouple Photo Attached.

We have Thermocouple & recorder calibration certificate.

Regarding the question of overheating/Overlapped the Heating band...... the joint is painted there is no color difference of the particular area of the heating band/ Bulge Area. Although machine will show that if it is overheated.

My question is all spool ( Eight Nos & each spool has two nos of joint ) is a common header ( Header weight is 6,3 Ton) downside is locked in the another header. Is it possible there is no expansion area of the joint & so the pipe is expanded at side ? 

Regards,

Pradip

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[Vishwas Keskar Welding Manager Pune India]

This bulging is due to restricted movement of the parts being post weld heated during PWHT .
Due to restraints at the end of the  pipes, the bulging might have taken place.
Also pl note  that PWHT temperature is a bit high ie 750 - 760 Deg C for GR 91   as compare of GR 22 , GR 11 ETC