Acceptable tolerance for surface defects on pressure piping

[Mech 3D]

Hello Engineering Family,
I have a 6 inch stainless steel SAF2205 which operates at 40bar and 220 degrees Celsius.
During NDT inspection of the new pipe I found a surface crack , and I had to cut through a groove 2mm deep to check how far the crack is but beyond that the pipe is fine.
Is this pipe acceptable with a 2mm groove or I need to reject it? Any standard I can use?

 

[SWComposites]

How thick is the pipe wall?
2mm deep sounds really bad. Why not just weld the crack?

 

[Mech 3D]

How thick is the pipe wall?
2mm deep sounds really bad. Why not just weld the crack?

its 10.97mm originl thickness

 

[LittleInch]

How do you know beyond that it is fine?

Is it cracked from both sides?

Have you dye pen tested the cut out?

But for Stl Stl 2mm defect is pretty significant as it the size and length of the groove you have created (no pictures or details provided)

 

[ctopher]

Hopefully you have some type of internal spec, or industry standard, to follow that indicates what is acceptable?

 

[akpipelineengr]

Any standard I can use?

Start with the design code.

Then perhaps API 579.

 

[LittleInch]

I would reject it myself as its new, but otherwise you're into a Fitness for Purpose assessment where depth, length, amount of wall lost etc all comes into play.

Which is API 579 / ASME FFP-1

But why do that for a new pipe?

 

[rb1957]

why was it so thick to start with ? ie was it just a convenient size and much heavier than the design requirements require (unlikely) ?

remember there are many design requirements beyond static strength. A key one may be corrosion allowance.

how sharp is the cut ? or rather how blended ??

Are you the manufacturer of this tube, or did someone ship it to you, defect free ??

One thing you could do, to offset the loss of strength, is to impose an inspection of the part. This is usually enough for people to reach the right decision (ie scrap).

Early in my career I got called to the factory's lab, to their ultrasound tank. Inside this small room were people from every country in Europe, each going 20 to the dozen in their own language. At the tank were a couple guys from my factory, and they asked me "these are the hydraulic actuators for the new prototype fighter's flight control system. we're getting ready for first flight (soon). we've found surface breaking defects. do you think that's bad ?" seriously ! I think I replied, after some reflection and time to regain my composure, "you want to risk the prototype of next generation fighter with dodgy actuators ?? seriously??" (I don't think I said "are you effing nuts?" ... but I may have !?)

 

[EdStainless]

Reject it and require UT of the entire lot.
This doesn't meet the original requirements.

 

[mfgenggear]

I agree reinspect the entire lot. cutting a slot into the pipe reducing its wall strength is not an acceptable procedure. radio graph, Mark the location, drill out, not grind out, then reweld , then re ndt verify removal.