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Up Topic Welding Industry / General Welding Discussion / thickness of patch
- - By rainbow202 (*) Date 01-08-2021 06:14
i need to weld patch  on vessel because there is hole on it.
the thickness of  vessel is 12mm, so what is thickness of patch which must be welded??
plz help me :cry::cry:
Parent - - By Lawrence (*****) Date 01-09-2021 00:03
Code of construction, material type and intended service, among many other things must be known before any advice can be put forth.
Parent - By rainbow202 (*) Date 01-12-2021 19:35
hello
the vessel is distillation tower
the material is ASTM A285 grade C
no PWHT
is this information enough???
thanks
Parent - - By Jim Hughes (***) Date 01-09-2021 17:44
rainbow202,
the thickness of the patch is the least of your worries. There is a lot of information needed first. Material, PWHT or not, what service?  Is this vessel stamped? Is there a U1 for it? If there is a U1, a lot of these questions can be easily answered. Do you have the authority to weld on a vessel? Do you have a NB R certificate? If so have you spoken to your A.I about this hole?
Parent - - By 803056 (*****) Date 01-10-2021 17:23
Jim gave you some worthwhile direction. Lawrence touched on an important question as well.

What is the the vessel used for?
Is the vessel a code stamped vessel?
Is the tank located where code compliance is a legal requirement?
What is the material of construction?
What the vessel subject to PWHT?
Was the vessel subject to NDE per a code requirement?

As Jim noted, it it is a code stamped vessel, many of the questions can be answered by the U1. If the vessel is not a code stamped vessel, you have a lot of leg work to do before arcing and sparking.

Al
Parent - By rainbow202 (*) Date 01-12-2021 19:32
hello
the vessel is distillation tower
the material is ASTM A285 grade C
no PWHT
is this information enough???
thanks
Parent - - By rainbow202 (*) Date 01-12-2021 19:33
hello
the vessel is distillation tower
the material is ASTM A285 grade C
no PWHT
is this information enough???
thanks
Parent - - By Jim Hughes (***) Date 01-13-2021 16:16
rainbow202,
To answer your question, yes it can be repaired, (Review NBIC part 3 to find out for sure) If your company has code stamps (R -Repair stamp) in good standing with the National Board (meaning its current) then you will have a ASME Code Manual some where. Then your next step is to reach out to your A.I and go over the repair plan with him. Is this vessel stamped? Is there a U1 for it? If there is a U1, a lot of these questions can be easily answered. Do you have the authority to weld on a vessel? These questions need to be answered. It's just a guess but I'm thinking a distillation tower is going to meet the definition of a ASME Sec. VIII vessel, if it's located in the US. Please be advised. This is a big deal and you should not just weld on it without answering these questions.
Parent - - By rainbow202 (*) Date 01-15-2021 14:43
hi
it is located in Egypt.
yes  a distillation tower is going to meet the definition of a ASME Sec. VIII vessel
there is hole on a vessel and i want to know the thickness of patch which should be welded on hole what is the standard that useful to me??
the origin thicknesses of vessel is 12 mm
help plz
Parent - By 803056 (*****) Date 01-15-2021 16:34
If it is a code stamped vessel and you wish to maintain the code status, your repair will have to meet the requirements of the NBIC and you will have to involve an Authorized Inspector. When all is said an done, the "repaired" vessel will be as "good as new". 

It isn't just a question of what thickness you should use and "slap on" a patch unless you are going to repurpose the vessel as an artificial coral reef.

Best regards - Al
Parent - By Joey (***) Date 01-25-2021 01:28 Edited 01-25-2021 01:32
hi

Your issue may be referred to API 510 that covers the in-service inspection, or repair of pressure vessels that have been placed in service. Here what API 510 says:

Fillet-welded Patches
8.1.6.1.2.1 Fillet-welded patches may be used to make temporary repairs to damaged, corroded, or eroded areas of
pressure vessel components. Cracks shall not be repaired in this manner unless the engineer determines that the cracks will not be expected to propagate from under the patch. In some cases, the engineer may need to perform a FFS analysis. Temporary repairs using fillet-welded patches shall be approved by an inspector and engineer.

API 510 never stated the minimum thickness of the patch plate, my guess is the thickness should not be lower than the required min thickness + the corrosion allowance. However, you need to get this information from the Pressure Vessel Engineer.

7.6 Required Thickness Determination
The required thickness shall be based on pressure, mechanical, and structural considerations using the appropriate
design formulae and code allowable stress. For services with high potential consequences if failure were to occur, the
engineer should consider increasing the required thickness above the calculated minimum thickness to provide for
unanticipated or unknown loadings, undiscovered metal loss, or resistance to normal abuse.

Hope the above helps.

Joey
Up Topic Welding Industry / General Welding Discussion / thickness of patch

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