PED Joint Coefficient

[tim042159]

Can someone explain 7.2 of the 97/23/EC PED dealing with joint coefficients?

 

[prex]

You are referring to this text:

7.2. Joint coefficients
For welded joints, the joint coefficient must not exceed the following values:
- for equipment subject to destructive and non-destructive tests which confirm that thewhole series of joints show no significant defects: 1,
- for equipment subject to random non-destructive testing: 0,85,
- for equipment not subject to non-destructive testing other than visual inspection: 0,7.
If necessary, the type of stress and the mechanical and technological properties of the joint must also be taken into account.

This is quite common and also quite general: standards (like EN13445) will be more specific on the subject.
Can you better specify your questions?

prex

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[KaiserMech]

My question is for the first indent. What do they mean when they refer to destructive testing in terms of frequency and method ? Obviously, you can't test the finished product, so this is confusing because destructive testing could be considered design validation.

Willem Mast
wmd2

 

[prex]

I confirm: it is a quite general statement, you cannot take it as prescribing specific procedures. Destructive testing will generally be done on weld coupons used to validate weld procedures.
What that statement tells you is that the testing will need to be extended to the entirety of the weld joints to adopt a coefficient of 1. What kind of tests it is not specified here, it is the purpose of the technical rules.

prex

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: Online engineering calculations

http://www.megamag.it

: Magnetic brakes and launchers for fun rides

http://www.levitans.com

: Air bearing pads

 

[Drexl]

Is this coefficient only for circular welds used to join piping components such as straight pipes, elbows and tees?

Or do i have to use a welding component also if i buy prefabricated piping components such as welded pipes and tees?

For pressure pipes and piping components, when would you use a lower coefficient than z=1.0? Obviously when the weld is not 100% tested, but when would that be?