Section VIII Pinholes Open to Surface - Criteria

[WBH]

All,

Researching acceptance criteria for pinholes and elongated indications open to the surface. The item in question meets acceptance standards for Appendix 6 for MT and Appendix 8 for LPT that can be open to the surface. UW-38 address repair of defects and states pinholes open to the surface shall be removed. Does this mean that pinholes regardless of size, open to the surface are defects and not acceptable?

Thanks in advance

 

[XL83NL]

Yes

 

[weldtek]

I have to disagree, respectfully - of course. To say that UW 38 means that all pinholes open to the surface and detected visually, must be removed does not mesh with other Code paragraphs, such as App 6 & 8. See Interpretation VIII -1-89-88

 

[XL83NL]

Perhaps the definition of pinholes Im aware of is different; I meant tiny holes (less than 1 mmdia) that go from the inside to the outside, straight through the wall, making a free path for any containment to get out of a pressure vessel (or piping system), hence making the system sorta like 'atmospheric'.
Not sure how the Code addresses those defects, but I cant imagine it will allow them. Refer to this example of a video showing the pinhole leak I meant. This is a video of a leak though apinhole we found a few years ago in a piece of piping during installation of that piping in a skid.

 

[WBH]

Weldtek

I tend to be in agreement with your assessment, however what is the purpose of UW-38? This is my hold back,UW-38 is applied after conducting RT repairs as noted in UW-51. Would any other weld area not RTd be required to meet UW-38? Or just weld repair area?

Thanks guys enjoy the input and learning experience.

 

[weldtek]

What is the purpose of UW-38? It's simply stating that defects are to be removed and rewelded.

This is my hold back,UW-38 is applied after conducting RT repairs as noted in UW-51. It can be, but it also refers to VT.

Would any other weld area not RTd be required to meet UW-38? Or just weld repair area? I don't see anything in UW 38 that restricts it radiographed joints or to repair areas.

 

[boaz6636]

I have read UW-38 and agree with the input from everyone. I want to know if anyone had ever heard of using the acceptance criteria from B31.3 Sevier Cyclic to set an acceptance criteria for pinholes and elongated indications open to the surface on a project where the client (Me) does not want these types of indications accepted on my ASME Section VIII Div.1 Pressure Vessels. I run into this question a lot and I want to put it in writing to my folks so that there is know question in want we expect from the fabricator.

 

[Haiker]

See the interpretation below:
Are pin holes which may propagate through thickness the issue or is porosity the issue.

Interpretation: VIII-1-89-88
Subject: Section VIII, Division 1 (1986 Edition, 1988 Addenda), UW-38
Date Issued: May 10, 1989
File Number: BC86-519
Related Documents:

Question: Does UW-38 prohibit all visible surface porosity in welds?
Reply: The Code has no specific requirements in this regard. The Manufacturer shall establish workmanship criteria consistent with the material and/or service requirements.

 

[DekDee]

boaz6636,
You as the client can impose any additional requirements that exceed the code requirements as long as it is reflected in contract documents.
Generally this is by way of a project specification.
Hope that helps,
Regards,
DD

 

[XL83NL]

Can someone provide of of give the definition of a pinhole?
Is a through-thickness pinhole also regarded a pinhole in this respect, or is surface porosity in general a pinhole? To my believes it matters a lot if it's through thickness or not.

 

[DekDee]

XL83NL,
Pinhole is a non standard welding term that is generally used for castings or surface treatment (painting etc).
As I am sure you are aware if gas is entrapped in molten metal it can sometimes break through to the surface and create surface porosity.
The really small ones are called pinholes (again - non standard terminology).
A through thickness "pinhole" would be extremely difficult on a single run weld, virtually impossible on a multi run weld.
Cheers,
DD

 

[XL83NL]

A through thickness "pinhole" would be extremely difficult on a single run weld, virtually impossible on a multi run weld.

Agreed, yet Ive seen them. Refer to the link in my 2nd post here.

Google-ing on pinhole shows defects that seem be caused by improper setting on the welding machine like e.g. incorrect downslope.