RE: [MW:22705] tube to tube sheet welding

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

pgoswami@quickclic.net

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

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

 

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

pgoswami@quickclic.net

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

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.

On Jan 10, 2015 12:00 AM, "venkkatesh krishnan" <venkkateshkrishnan@gmail.com> wrote:

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

On Thursday, January 8, 2015 at 11:17:26 PM UTC+5:30, Josnit wrote:

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

On Jan 8, 2015, at 19:09, venkkatesh krishnan <venkkates...@gmail.com> wrote:

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.

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