API 579 FFS - Allowable Minimum Measured Thickness of Pipe
API 579 FFS - Allowable Minimum Measured Thickness of Pipe
(OP)
Hello,
I have a question about API 579, will pipe always fail Level 1 and 2 assessments and require a Level 3 analysis if there is a minimum thickness measurement below 2.5mm/0.1"? (Per Table 4.4)
If it's B31.3 and the supplemental loads are neglible such that you can perform a Level 1 analysis, must it still pass the tmm >= 0.1"? 4.4.2.1 d) seems to suggest this. How does this effect small D pipe especially 5S where tnom is less than 0.1" up to size 4"?
Thanks in advance for any help.
I have a question about API 579, will pipe always fail Level 1 and 2 assessments and require a Level 3 analysis if there is a minimum thickness measurement below 2.5mm/0.1"? (Per Table 4.4)
If it's B31.3 and the supplemental loads are neglible such that you can perform a Level 1 analysis, must it still pass the tmm >= 0.1"? 4.4.2.1 d) seems to suggest this. How does this effect small D pipe especially 5S where tnom is less than 0.1" up to size 4"?
Thanks in advance for any help.





RE: API 579 FFS - Allowable Minimum Measured Thickness of Pipe
have you read the API 579 & A S M E FFS 2 (2009) Fitness for Service Example Problem?
RE: API 579 FFS - Allowable Minimum Measured Thickness of Pipe
RE: API 579 FFS - Allowable Minimum Measured Thickness of Pipe
8"NPS Sch 5S = .109" 2.8mm Sch 10S = .148" 3.8mm
3"NPS Sch 5S = .083 2.1mm Sch 10S = .120 3.1mm
It is impossible for brand new pipe that is at the nominal wall thickness to be deemed as below necessary thickness. You are in the wrong book.
RE: API 579 FFS - Allowable Minimum Measured Thickness of Pipe
I'm somewhat confused as API-579 does include piping and API-570 specifically refers to API-579. There is a specific requirement for piping components that minimum measured t >= 2.5mm in Table 4.4 of API579.
I agree that this requirement doesn't make sense, and the RP seems much better written for vessels and piping, however, that acceptability criteria is still there for piping.
Has anyone run into this before or received clarification? It seems unnecessary to jump to a Level 3 assessment when you're confident it's already acceptable.
RE: API 579 FFS - Allowable Minimum Measured Thickness of Pipe
OT: I don't see any means to edit my post.
RE: API 579 FFS - Allowable Minimum Measured Thickness of Pipe
When you calculate the pressure-based minimum thickness of pipe, the numbers are usually at or below 2.5mm. So the limiting condition is Span. Thus the evaluation becomes "Is the existing wall thickness sufficient for the weight of the unsupported span?"
And yes, the answer usually arrived at is that 2.5mm or more is needed to span the gap between hangers. The point is that "one size fits all" is no more applicable in piping than it is in underwear. When you approach 2.5mm, evaluate your condition. Do not automatically reject it without an evaluation.
RE: API 579 FFS - Allowable Minimum Measured Thickness of Pipe
HAVE YOU READ Overview of Process Plant Piping System Maintenance
and Repair AND THE 3 EXAMPLES
ht