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.
Sent: Sunday, January 11, 2015 7:47 PM
To: materials-welding@googlegroups.com
Subject: RE: [MW:22705] tube to tube sheet welding
- 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...
- 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.
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
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.
Sent: Saturday, January 10, 2015 9:53 AM
To: materials-welding@googlegroups.com
Subject: RE: [MW:22701] tube to tubesheet welding
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
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.
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. 1If 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 iPhoneDear 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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