tube to tubesheet welding

[venkkatesh krishnan]

Dear Experts,

             I need to do tube to tubesheet welding for CS Steel that is tubesheet material is SA 516 Gr.70 thk 20mm and tube material is SA 179 thk is 2.108mm welding process is GTAW, i have WPS in GTAW process with 3G welding my doubt is this WPS is suit for above mentioned statement or i need to qualify any welder qualification for welding this process. kindly please suggest me what ill do.


i am awaiting for your reply.

Thanks & Regards,

G.Venkkatesh.

[nithind...@gmail.com]

Hi,

What is the code of construction?

Considering welding code as Section IX and construction code Section Viii div. 1

If your PQR is qualified on 10mm plate in 3G, then both of ur tube as well as tubesheet, with range 1.5mm to 20mm. You can use it for welding tube to tubesheet welding. 

If your PQR thickness is less r more than 10mm then you may have to club it with any other PQR based on the ranges required.

Above info is valid only if construction code is ASME section VIII Div.1. If it is Div.2 then you have to qualify a pqr as per QW-193 of ASME section IX.

Hope above information is useful to you.

Sent from my iPhone

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[venkkatesh krishnan]

Dear Sir,

            Thanks for your reply, code of construction is ASME SEC IX & SEC VIII DIV.1, and i have PQR qualified thickness is 10mm with 3G position,my doubt is to initiate the tube to tubesheet welding process before i need to do any Welder Performance Qualification Record(WPQ)?

            I am awaiting for your reply, Thanks in advance.

Regards,
Venkkatesh

[Nithin Joseph]

Yes, Since it is a critical weld, you need to have a qualified welder to weld this joint.

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regards,
Dsilva

[Saravanan Sornam]

Dear venkatesh,
If your weld joint for tube to tubesheet is just a Seal weld and there is no special requirements from your client, then you can propose your client to use the existing pqr.
Check your client spec for any Mockups required as per ASME IX Qw193.
Is this for U stamp Project?
If yes, then you write a WPS based on existing 10 mm PQR , once it is confirmed as Seal Weld in your fab. Dwg
Seal weld is nothing but a fillet weld.
Read ASME QW 288 also for tube to tubewelds.
Regards
Sarav.

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[pgoswami]

Hello Venkatesh,

 

Tube to tube sheet welding is a special kind of welding, both process and technique wise.. Essentially the parameters , techniques adopted for a groove weld will not work for this type of weld joint.

 

A separate procedure and performance qualification is required.

 

Please see some of the extracts from Sec-IX,QW-193 below.

 

Hope this will clarify your query.

 

Thanks

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Specialist

Ontario, Canada

pgos...@quickclic.net

pradip....@gmail.com

http://ca.linkedin.com/pub/pradip-goswami/5/985/299

 

QW-193 TUBE

‐TO‐TUBE SHEET TESTS

When the applicable Code Section requires the use of this paragraph for tube‐to‐tube sheet demonstration mockup qualification, QW-193.1 through QW-193.1.3 shall apply.

QW-193.1 Procedure Qualification Specimens. Ten mockup welds are required to qualify each procedure. The mockup assembly shall essentially duplicate the tube hole configuration and tube-to-tube sheet joint design within the limits of the essential variables of QW-288. The thickness of the tubesheet in the mockup test assembly shall be at least as thick as the production tubesheet, except it is not required to be thicker than 2 in. (50 mm). The mockup welds shall be submittedto the following tests sequentially and must meet the applicable acceptance criteria.

QW-193.1.1 Acceptance Criteria

— Visual Examination.

QW-193.1.2 Acceptance Criteria

— Liquid Penetrant.

QW-193.1.3 Acceptance Criteria

— Macro‐Examination

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From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of Saravanan Sornam
Sent: Saturday, January 10, 2015 7:24 AM
To: material...@googlegroups.com
Subject: Re: [MW:22700] tube to tubesheet welding

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/CALV1rkLyqZ2Na--BCohe8cmz3GMAp%3Dx1jtk_96rD%2Bwnopj900Q%40mail.gmail.com.

[John Henning]

No.   Untold thousands (hundreds of thousands?) of heat exchangers have been built without problem without mockup  qualification.

 

Section VIII, Division 1, does not require qualification by mock-up.  Costly and generally unnecessary.  

Section VIII Div 2 design is the only ASME Code section that requires this. Division 2 transferred responsibility for qualification from VIII-Div. 2 Article F3 to Section IX, which created QW-193 etc to support Div 2 construction.

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From: material...@googlegroups.com <material...@googlegroups.com> on behalf of pgoswami <pgos...@quickclic.net>
Sent: Saturday, January 10, 2015 9:53 AM
To: material...@googlegroups.com
Subject: RE: [MW:22701] tube to tubesheet welding

 

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/6CF39F36C24D48D3B0EA099C9E3535FF%40HOME.

[pgoswami]

John,

 

Requirements of Tube -to Tube sheet (T#TS) welding has always been "not so clearly defined" in ASME codes. T#TS welding is a critical weld and a very specific weld joint , whose integrity can not be assured by groove welding qualification alone. The failure of a T-TS weld may scrap the whole exchanger in the corrosive environments.

 

Due to such inadequacies in the code many clients (e.g Oil and Gas, refining, petrochemicals etc) have or had their own specifications on T-TS welding, where the procedure qualifications had involved the following as essential variable:-

• materials, position, tube pitch( square, triangular), tube O.D
• typically the testing the T-TS weld block involved, Pull Out Test, Macro, RT, Leak Path calculation, etc...

Performance qualification involved many of the above parameters , except the pull out test is not asked for performance qualification coupon.

 

Tube to tube sheet weld these days involve heavy application of automated welding. No good fabricator would  dare to apply the equipment straight on the production joints without setting the welding parameters on the "mock up block. Qualification of the mock up block  may be  treated as a  combined  mock up for  qualification of welder and procedure and the equipment, based on design code, project specifications.

 

Same applies for manual  welding of T-TS joints. In the past there were very little details in ASME code on T-Ts joint qualification. The latest versions, 2010 onwards have some details as stated  below(my previous email).

 

ASME gives the leverage of using groove welding rules  for T-TS welding, however that does not address the real integrity of the heat exchangers to the best interest.

 

It's up to the fabricator how to treat T-Ts welding:-

•  just to go by the rule as in ASME Sec VIII codes. Fabricator does not get qualified for top of the line  high quality heat exchanger jobs
• or develop a full set of  qualified weld procedures on T-Ts welding including the welders/welding operators.

Unfortunately I had seen the later in more numbers that's why my mind set and the thought process is on qualifying T-TS welds separately  and treat this separately than conventional groove weld. Many good fabricators treat T-TS weld joint a very specific type of weld  and runs  procedure and performance qualification accordingly.

 

Hope this clarifies the various points.

 

Thanks.

 

Pradip Goswami, P.Eng,IWE

Welding & Metallurgical Specialist

Ontario, Canada

pgos...@quickclic.net

pradip....@gmail.com

http://ca.linkedin.com/pub/pradip-goswami/5/985/299

 

NONMANDATORY APPENDIX K:- GUIDANCE ON INVOKING SECTION IX REQUIREMENTS IN OTHER CODES, STANDARDS, SPECIFICATIONS, AND CONTRACT DOCUMENTS

 

K-302 RECOMMENDED WORDING — TUBE-TO- TUBESHEET WELDING:- When invoking Section IX for qualification of tube-totubesheet welding procedures and personnel, and qualification by use of mock-ups is desired, the following wording is recommended. “Welding procedures, welders, and welding operators shall be qualified using mock-ups in accordance with Section IX.”

 

Note that if qualification using mock-ups is not specified but qualification to Section IX is, tube-to-tubesheet welding procedures and personnel may also be qualified following the standard groove welding rules.

 

QW-288 TUBE‐TO‐TUBESHEET QUALIFICATION ESSENTIAL VARIABLES

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From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of John Henning
Sent: Sunday, January 11, 2015 12:01 AM
To: material...@googlegroups.com
Subject: Re: [MW:22704] tube to tubesheet welding

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/1420952437675.40387%40deltak.com.

[Saravanan Sornam]

Dear Pradip Ji ,

I agree with you .

I worked for Air Cooled Heat Exchangers Manufacturing Company in Korea, built as per API-661, we did MockUps as per Client requirements like BASF , PDO, Shell, Exxon, Technip, etc.

But , when the joint configuration is just a SEAL WELD for Non Coded Jobs, we used the Groove Weld Qualified WPS and restrict the Weld parameters like Max 135 Amps for 2.0 mm GTAW Filler Size, to weld 2.11 mm tube wall thickness in rewriting the WPS especially for SEAL WELDS and get approval from client, before we start fabrication. It depends on client acceptance too.

So, generally we make separate WPS with a joint sketch and get approval from client for SEAL WELDs too.

Weld Sequence like, 1st pass by just Fusion and 2nd pass with Filler, and the Filler Size is also important to be considered. 

But surely, we have to make some MockUp pieces for the welder to get practice and to give a perfect Sealing, before he weld the actual fabrication joint, just for Visual Inspection.

Incase of special jobs for BASF, Technip, Exxon, Shell , ofcourse we have to follow their Spec, make MockUps, tested like Macro to check MLP, Hardness, PT, Visual, Pull outs etc, with TPI witness, if required.

If the weld joint configuration is Groove With Fillet Strength Welds , as per ASME Sec VIII Div -1 Figure UW-20.1 ( Some Acceptable Types of Tube‐to‐Tubesheet Strength Welds ) , for example type "d " joint ,

welding is not at all easy. We need MockUps to ensure the weld soundness and NO DEFECTs.

Hardness , MLP will be more difficult to achieve especially when Tube and Tubesheet is a C/S like SA 516 Gr. 70 to SA-179 combination for Strength welds and MOCKUPs are must required to achieve all the test results. 

This is just my experience which I shared.

Regards,

Saravanan

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[John Henning]

I have been involved in making heat exchangers for many years.  Have been involved in both automatic and manual welding of, typically, J-groove strength welds.  The basic lesson for manual welding is to never hurry the root pass.  The root pass should be made with small diameter wire,  1/16 in.  This will assure penetration to the root and prevent bridging that occurs with larger diameter wires.  

Qualification (performance or procedure) by mock-up in no way guarantees that the t-ts weld will be good.  Having been burned by vendors has amply demonstrated that.  It is most problematic in shops where welders are paid on a piece work/pounds deposited basis.  In the remainder of shops, there can also be problems when management is pushing to hard for quick completion.  This is when excessive fill causes bridging of the root and almost guarantees premature failure.

Mock-up demonstration is expensive and unwarranted.  A review of welding procedures, shop practices, and previous history does more to assure a quality product then such qualification. 

Certainly, if exotic materials are required, the media is lethal or unusually corrosive it may behoove the purchaser to pay extra for special qualification.  Surprising how many demanding customers don't want to do that.

I will agree that if the these type welds are to be welded by automatic/machine processes, then a mock up qualification makes sense.  It is, as you point out, necessary to establish the correct parameters as there is only limited in process adaptability.

Please also note, that ScIX qualification does not require the tube sheet pitch and spacing be used.  The tube holes may be in linear string - Interpretation is on the way.

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From: material...@googlegroups.com <material...@googlegroups.com> on behalf of pgoswami <pgos...@quickclic.net>

Sent: Sunday, January 11, 2015 7:47 PM
To: material...@googlegroups.com
Subject: RE: [MW:22705] tube to tube sheet welding

 

To view this discussion on the web visit https://groups.google.com/d/msgid/materials-welding/699EB0922B354420B3092002647FB2AA%40HOME.

[Saravanan Sornam]

Dears ,

When we talk about mandatory Qualification requirements for Tube To TubeSheet welding as per ASME-IX other than Client Spec requirements, 

Ofcourse the Client spec rules first and must follow and fulfil their requirements.

 But, as given in ASME IX , QW-193 for Tube To Tubesheet Qualification, 

" When the applicable Code Section requires the use of this paragraph for tube to tubesheet demonstration mockup qualification, QW-193.1 through QW-193.1.3 shall apply ".

Sec. VIII Div. 1 does not stipulate as a mandatory requirement to apply QW-193, it is manufacturer’s option to choose between QW-193 otherwise normal procedure qualification in accordance with QW-250 tables.

However, in case of Sec. VIII Div. 2, application of QW-193 is mandatory in accordance with para. 6.3.4.

Hope my understanding is right Gentlemen.

Regards,

Saravanan

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[venkkatesh krishnan]

Dear Experts,

        Thanks for your reply,

              And i have one more doubt, i have WPS,PQR with combination of process like GTAW+SMAW process,

Description of WPS & PQR:

            Base metal thickness: 25mm
            GTAW Welding: 10mm
            SMAW Welding: 15mm
            Material: SA 516 Gr.70
            Position: 3G
            Code: ASME SEC IX

Tube to Tubesheet Welding:

            Tube material: SA 179
            Tube sheet material: SA 516 Gr.70
            Process: GTAW
            Tube thickness: 2.108mm
            Tubesheet thickness: 20mm
            Code of construction: ASME SEC VIII DIV.1

     I can able to use this above mentioned Procedure for welding this tube to tubesheet. or need to qualify?

Thanks in advance, Please send me your valuable reply as soon as possible.

Regards,
Venkkatesh Gopalakrishnan

[SSK,QC]

Dear Sirs, 

Please advice the following, for a Tube to TS welding

WPS

Tube Dia: 25.4mm

Tube Thk: 1.65mm

Pitch : 31.75mmm

Ligament: 6.35mm

PQR

Tube Dia: 19.05 mm

Tube Thk: 1.65 mm

Pitch : 25.4 mmm

Ligament: 6.35mm

My argument is as follows

PQR is not acceptable as supporting PQR for WPS as specified tube diameter is 25.4mm, on the other hand, tube diameter in the PQR is 19.05mm which is less than 90% of the specified diameter 25.4mm. It's against par. QW-288.1(d) of ASME Sect. IX. Hence VENDOR should submit another PQR or re-qualification is required.

PQR with dia less that 90% of OD 25.4 that is between 25.4 - 22.48MM dia shall support this WPS. See JGC comment on QW 288.

But technically as PQR is for lesser dia (of course same tube thk) than actual production/ WPS, it is acceptable.

Please confirm if am right or comment when am wrong.

Regards

SSKumarSelvam

[Manoj Prabakaran.M]

Dear sir,
I have one more doubt, we are fabricating CS heat exachanger ref construction code as asme sec viii div i.
Tubesheet thk as 150mm
Tube O.D as 30 X 2.5mm thk.
Wether preheating is required for this joint or Not before t/ts welding?
Kindly give me the solution,

MPK

[Prakash Hegde]

Hi!

Yes Ir is always recommended to have proper uniform preheating to reduce distortion of t sht .hlgher hardness .and cracks

Regards

Hegde p b

 B

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