1. When it is necessary to qualify a welding procedure for repairing a defect in a pressure vessel (tower/column). I mean that when I have a crack detected by an NDT method in an in-service pressure vessel, in this case and in order to repair it, should I use the same original welding procedure specification used in the shop or shall I qualify a new one? And what are the conditions or provisions if any?
2. According to 188.8.131.52 in API 510 code, what is the joint preparation geometry, should I make (or machine) a V chamfer shape in the same coupon plate and fill it with welding or should I join 02 plates forming a coupon with a V groove weld and join them by welding and carry out the necessary tests by the ASME IX code.
I will be very obliged to you should you answer me promptly.
AS per API 510 any Repair or alteration in welding is to be done in accordance with Applicable ASME Codes,
The procedure to be used for welding should be a qualified procedure. So u can use the same original Welding procedurec if it is qualified.
184.108.40.206 of API 510 refers ASME SEC VIII Div I UG84,
UG 84 (f) Impact Testing for Weld
As per this your Imapct test plate should be in accordance with your Welding Procedure Used and in your WPS there is no such joint configuration so u have to follow the weld map which is mentioned in your WPS.
Any API 510 Inspector would give u more and confirm detail about this.
Racid, there are no 'Repair' weld procedures -- WPS's -- required. Any appropriate WPS qualified per ASME Sect. IX may be used. In addition to impact testing that may be required, because it was a requirement when the vessel was made, you also have to consider several other items.
Post-weld Heat Treat -- If the original weld required PWHT, the repair probably will. It may be possible to use a Temper-Bead weld technique to avoid PWHT. Check with your API-510 Inspector.
Hydrostatic testing may be required, or waived by the 510 Inspector.
Preheat -- based on the actual thickness of the base metal at the repair location, and the P-Group of this metal, and the welding WPS's requirements, a significant preheat may be required. Ask your 510 Inspector.
To maintain the Code status of the vessel being repaired, there has to be a Repair Procedure -- a step-by-step checklist of how the repair is to be accomplished. This Procedure [typically refered to as a 'Traveler' in the USA] gives the method of defect removal, type of NDE required to verify removal, WPS [welding procedure(s)] to be used to reweld the removal area, and NDE to accept/reject the final weld, PWHT requirements [if any] and any further testing [like hydrostatic] required. This procedure must be pre-approved by a certified API-510 Inspector, and will include 'HOLD' points. When the work reached a HOLD point, the Inspector must inspect and sign for that stage of the repair.
Bottom line -- no repair of a Code vessel can be conducted without lthe participation and concurrence of an API-510 Inspector.
Please note the 'capital "I" Inspector'. This denotes a person that is certified to oversee and accept repairs and alterations of pressure vessels, typically holding an API-510 certificate. Without an Inspector, the "U"-stamp on ASME Section VIII vessels stands for "U don't mess with it"
I like the meaning of "U" Stamp Described by you,
As you mentioned above the Repair procedure i have a small doubt that this procedure is to be approved by ASME Authorised Inspector or and API 510 Inspector can also review and approve the Repair Procedure.
And what are the steps if the Vessel is having a National Board Registration No for carrying out any repair work.
Thank You all for your answer however, I still would like to
Thank you all so much for your responses.
It's really the most clear one I have had concerning my intended work (qualification of a repair WPS according to the API 510 Repair and Inspection Code).
For the fisrt question: I totally agree with you.
But for the second one: I have to notice that the API 510 Code mentiones in page 7-2 paragraph 220.127.116.11.d: Controlled-Deposition Welding Method (Notch Toughness Testing Required) the following:
point d: A weld procedure specification shall be developed and qualified for each application. The wledign procedure shall ...The qualification thickness for the plates and repair grooves shall be in accordance with table 7-1.
Please note the words shall and qualified.
The table is shown in the bottom of page 7-2. So I want some more details about the groove and if it is in the same plate or constituted from two (02) plates that should be assembled together by welding.
Racid, I believe that you have an old 510 in your hands. The current 510 is 9th Edition [no addenda]. The new paragraph # is 18.104.22.168.2.3.
The 'Controlled Deposition' technique is to remove the need for PWHT, thus the notch-toughness and hardness of the deposited weld in the test coupon need to be measured. This coupon should be one piece, as you are simulating a weld repair in a completed vessel. The shape of the groove should also simulate a repair.
Personally, mine would be a 2.1" [52 mm] or thicker coupon about a foot square [300 mm] with a 1" deep [25 mm] U-groove about 6" long [150 mm]. Groove to have an included angle of 65-80 degrees, and a 3:1 taper at both ends of the groove. This coupon thickness will qualify you for 'Unlimited' base metal thickness, and a maximum depth of repair of 25 mm.
Please note the requirements in 510 for recording heat input on each layer. It would be best to have the welder travel slowly, to give a fairly high input value, as this will become the Procedure's maximum input.
I recommend the 'Temper Bead' method. It has the best overall results, and is the industry standard.