Materials & Welding: [MW:4808] PWHT of Hydrotesting vents in Sour gas service

Dear Friends,

The recommendations put forward by Mr. Prabhu Kumar is quite appropriate. Some back ground would help all on understand the issue.

The design code is ASME B-31.3. In appendix-F of this code it is specified that:-The following are some specific considerations that should be evaluated when applying certain metals in piping:-

· the possibility of stress corrosion cracking when exposed to cyanides, acids, acid salts, or wet hydrogen sulphide; a maximum hardness limit is usually specified (see NACE MR0175 or MR0103 and RP0472).

· NACE MR -0175 applies for oil and gas production, MR.-0103, applies for refining environments, RP-0472-explains the ways to avoid environmental cracking e.g. SCC in refining environments.

· The last standard (RP-0472) puts a lot of emphasis on controlled welding environments, such calculation of C.E for base metals, control of welding consumables, application of controlled heat input while welding, application of temper bead technique if required.

For sour gas service , if NACE MR-0175 is applicable over and above B-31.3 design codes, then the requirements of Annex-A of this standard would be applicable. It specifies the following conditions for welding:-

· Welding and weld hardness shall be as per clause 7.3.3(hardness surveys for welding procedure qualification, explained through sketches)

· Acceptable maximum hardness values for Carbon, carbon manganese steel and LAS shall be as per Table-A.1. As welded carbon, carbon manganese steels and low alloy steels are acceptable provided weld and HAZ does not exceed 22HRC.

· Carbon, carbon manganese steels and low alloy steels , which does not comply with above clauses shall be PWHT @ 620⁰C

Since requirements for “sour services” are very specific and restrictive, a weld mock-up or PQR should be done to satisfy 22 HRC criteria.

Assuming that a PQR already exists on C.S# C.S or equivalent PNos with ferritic electrodes, e.g. ER-70S2 and /or E-7018-H4, the above PQR/Mock-up could be used only to supplement the hardness requirements of 22 HRC max for seal welds. However it is advisable to know the composition of the coupon materials, such that the welding heat input and weld parameters could be decided to arrive at the above hardness limits.

Use of austenitic electrodes (e.g Inconel-82 or equivalent or 309S.S) would also call for 22HRC hardness requirements for weld and HAZ.

Thanks.

Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Component Integrity Section.

Engineering and Training Services

Ontario Power Generation Inc.

Res:-88,Garth Trails Crescent

Hamilton,Ontario, L9B2X1,Canada

Email-pgoswami@sympatico.ca

Email-pgoswami@quickclic.net

Tel-905-679-9677

Subject: RE: [MW:4801] PWHT of Hydrotesting vents in Sour gas service
Date: Mon, 12 Apr 2010 18:46:45 +0530
From: l.prabhukumar@saipem-india.com
To: materials-welding@googlegroups.com

Dear Suresh,

If you want avoid PWHT, you can carryout mock-up test weld to test hardness within HRC 22 and can be proposed to client for approval. E7018 or ER70S-2 type filler metal can be used. Since, it is only for seal welding, client may accept the proposal.

L. Prabhu kumar,

Sr. Principal Engineer,

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of suresh venkat
Sent: Monday, April 12, 2010 5:57 PM
To: materials-welding@googlegroups.com
Subject: Re: [MW:4800] PWHT of Hydrotesting vents in Sour gas service

Hi,

Material of construction is Carbon steel suitable for sour gas service with P & S restriction. Code- B31.3.

In original plan, all Sour gas pressure pipeline Hydrotest vents were of flanged connection with Blind flange.in the existing plant, we encountered lot of leakages in this flanged joint which leads to emergency shutdowns.

So we want to avoid flanged joints for closing Hydrotest vents. The no. of hydrotest vents are more, there is a serious concern

Our specification says threaded joints are not acceptable for Sour gas service, as there is possibility of leakage due to corrosion.

To balance all the criteria, we planned to provide threadolet on the pipelines as hydrotest vent.

After PWHT & hydrotest all the vent ends will be closed with Plugs( threaded joint).

To avoid any leakage we want to provide a seal weld (fillet joint). as the rating of joints are 600# & above.

This fillet joint is critical as we don't want to end up again in same trouble in a different way.

Please advise on avoiding PWHT for this joint & suitable electrode for this CS joint.

Thanks

Suresh

On Mon, Apr 12, 2010 at 2:40 PM, Kathalingam Babu <kathalingam.qaqc@ppl.com.sg> wrote:

May i know, which spec. says , sour gas service needs mandatory PWHT ?

Regards,

K.Babu

----- Original Message -----

From: Prabhu Kumar L

To: materials-welding@googlegroups.com

Sent: Monday, April 12, 2010 12:30 PM

Subject: RE: [MW:4793] PWHT of Hydrotesting vents in Sour gas service

Dear Suresh,

Please note that the intension of PWHT is to relieve the stresses from HAZ and weld metal as well. Use of Inconel or any other electrodes will not relieve the stresses from HAZ, and it remains same for all electrodes. Hence you cannot avoid PWHT. In order to reduce difficulties in PWHT you can propose the method as follows.

Buttering (weld overlay) of 5mm (if it is CS you can use same electrode) on the locations where weldolets to be welded to main pipeline.
After buttering, local PWHT shall be carried out as per procedure.
Welding between weldolet to buttered layer shall be done without PWHT.

The HAZ is a critical area which need to stress relieved. Also note that in general, the weld metal is softer than HAZ since, it contains very low % carbon and other minor alloying elements to improve slight toughness also.

Regards,

L. Prabhu kumar,

Sr. Principal Engineer,

Equipments & Materials Dept.,

Saipem India Projects Limited,

Nungambakkam High Road, Chennai - 600 034, India.

Tel:+91 44 43906588, Ext.: 588, Fax:+91 44 66840345,

Mobile Ph. No.: +91 9003010978.

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of suresh venkat
Sent: Sunday, April 11, 2010 4:49 PM
To: materials-welding@googlegroups.com
Subject: Re: [MW:4786] PWHT of Hydrotesting vents in Sour gas service

My intention was to weld with Inconel Electrode so as to have soft weld metal.

Further opinions will be more helpful.

On Sun, Apr 11, 2010 at 4:10 PM, Raghuram Bathula <raghurambathula@gmail.com> wrote:

what if you weld with SS (ER/E309) or Inconel? members pl share ur opinion

On Sat, Apr 10, 2010 at 10:46 PM, suresh <atozsuresh@gmail.com> wrote:

we have sour gas pipelines with higher & lower pressure. All the
pipelines are with Hydrotest vents which will be closed after
Hydrotest.

For low pressure pipelines we use flanged joint with a Blind flange.
For high pressure pipe line with flanged connection there is
intermittent leakages which needs immediate attention even sometimes a
shut down.

We intend to use a threadolet as vent & will be plugged & seal welded
after hydrotest. The problem is with PWHT. As all the lines in Sour
gas services shall be PWHT.

We want to avoid PWHT of this small fillet joint, Due to the location
of these joints & difficulty in PWHT. but it is dangerous to leave it
without PWHT as it may crack due to residual stresses.

Can you suggest any welding procedure & electrode to have this welding
with reduce hardness HRC 22 Max by which PWHT can be avoided.

Thanks

Suresh

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DISCLAIMER: The information contained in this communication is intended solely for the use of the individual or
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The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

To post to this group, send email to materials-welding@googlegroups.com
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The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

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DISCLAIMER: The information contained in this communication is intended solely for the use of the individual or
entity to whom it is addressed and others authorized to receive it. It may contain confidential or legally privileged
information. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution
or taking any action in reliance on the contents of this information is strictly prohibited and may be unlawful. If
you have received this communication in error, please notify us immediately by responding to this email and then
delete it from your system. Saipem India Projects Limited (SIPL) is neither liable for the proper and complete
transmission of the information contained in this communication nor for any delay in its receipt.
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THIS MESSAGE IS ONLY INTENDED FOR THE USE OF THE INTENDED RECIPIENT(S) AND MAY CONTAIN INFORMATION THAT IS PRIVILEGED, PROPRIETARY AND/OR CONFIDENTIAL. If you are not the intended recipient, you are hereby notified that any review, retransmission, dissemination, distribution, copying, conversion to hard copy or other use of this communication is strictly prohibited. If you are not the intended recipient and have received this message in error, please notify me by return e-mail and delete this message from your system. Ontario Power Generation Inc.

Materials & Welding

Tuesday, April 13, 2010

[MW:4808] PWHT of Hydrotesting vents in Sour gas service

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