Material certification for flange bolting

[hippocrocopig]

Colleagues,

I'm conducting a straw poll on general good practice in ordering bolts for pressure vessels (not a question on what is mandatory due to international codes).

Is it satisfactory to use flange bolting which only has a certificate of conformity (2.2) rather than a mill cert (3.1)? I am of the opinion that it is, as long as the bolting is not used in a highly critical application (v high pressure, lethal service etc.). My reasoning is that defects in bolting materials result in leakage rather than catastrophic failure (as, for example in a shell plate) and also that any such defect at site would simply lead to the faulty bolts being replaced, whereas a defect in a pressure plate would have to be traced back through chemistry, heat treatment, etc and may also involve weld repair.

Thanks,
HCP

 

[SJones]

Your reasoning would appear sound. ISO TR 13881 may help you to place your reasoning within a more auditable framework.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[roca]

It all depends on your client.
The big boys would require a 3.1 minimum for pressure bolting.

 

[PVinspector]

There is a Guideline (number 7/8) to the European Pressure Equipment Directive 97/23/EC which states the folowing:

"When these components contribute to the pressure resistance, their materials shall fulfil the relevant requirements of annex I, section 4.
Regarding section 4.3 of Annex I, a bolt is not considered to be a main pressure bearing part unless its failure would result in a sudden discharge of pressure energy.
When bolts are used as
- main pressure bearing parts a certificate of specific product control is required (unless the item of pressure equipment itself is in Category I)
- pressure bearing parts a test report is sufficient,
- non pressure bearing part a certificate of compliance is sufficient"

So the PED position is if the failure of that bolt would result in a "sudden discharge of pressure energy" it is a main pressure bearing part and would need 3.1, otherwise 2.2 would be acceptable. Kind of fuzzy.

Roca probably has it pretty close, depends on client, notified body, situation. One size does not fit all.

 

[gr2vessels]

roca is right, but in pressure vessel fabrication the 3.1 is indeed the minimum requirement. I believe that the certification is only standard for the bolting fabricators, including (at request) all the supplementary testing requirements of ASME SA 193, SA 194, SA 320, etc...
cheers,
gr2vessels

 

[unclesyd]

I have a friend in the fastener business who mainly handles studs. He only issues MTR's, no certificates, on all products that leave his business. He stated that almost to a person his customers insist on the MTR's. He did say that some of his customers who are distributors will issue a certificate of compliance based on the MTR.
He is able to use the MTR since he buys stud stock in single heat lots and does all the cutting, beveling, and stamping in house. Otherwise it would be a logistics nightmare.

 

[MJCronin]

hippo...

You are discussing "bolts on pressure vessels"..

To me, that involves only two general categores:

- Bolts on piping flanges, and are therefore under the rules of the piping code and,

- Bolts on manways, SRVs etc which are not part of a piping system,

It is my understanding that piping design codes such as ASME B31.1/B31.3 govern these bolts on piping systems.

Certificates of compliance (and all other similar documents) are the only material certification required by the piping code for these joints

-MJC

 

[hippocrocopig]

Thanks all.