is such practice for fatigue analysis normal?

[YuJie_PV]

hi all,
i come across an issue regarding how to exempt the fatigue analysis for the air cannons.

the situation is such that i am working with an equipment to which several air cannons are attached. the cannons are used to prevent accumulation of powder in the filter.
the air cannons are just like this:

it's subject to pressure fluctuation from zero to approx. 5 bar for tens of thousands of times during the expected life. therefore, the cannon definitely needs fatigue analysis per ASME VIII-2 part 5.
i consult with the manufacturer of the air cannon, who just states that they sell thousands of the cannons to market every year and never performed any fatigue analysis or ever been requested to perform such analysis.
i've encounter several cases of such kind, that no fatigue analysis ever performed for a vessels definitely needing fatigue analysis.
it seems all users have no issue with such situation
is it normal?
i am really curious to such phenomenon.

thanks in advance.









END

 

[IdanPV]

Refer to 5.5.2.2, if successful experience over a sufficient time frame is obtained with comparable equipment subject to the a similar loading histogram, then a fatigue analysis may be exempted.
Note that when evaluating experience comparable equipment, you shall evaluate the effects of the design features of (a) to (f).

Note that some Jurisdiction do not allow to use this paragraph.

 

[YuJie_PV]

Thanks @IdanPV,
i know the screening option based on 'experience with comparable equipment'.
if i choose this option, there are so many hoops to be jumped through.
is there any guidance?
For example, i've ever read TSG4's statement on what constitutes 'sufficient time'.
"if you can demonstrate 400 years of successful service, then I might accept a 20 year life based on past successful service."

https://www.eng-tips.com/viewthread.cfm?qid=431553

of course, i always trust TGS4's statement, just regarding this one, if it's true, this screening option would be useless.
of course, it's not me to do the paperwork, which is the vendor's scope.
what shall i ask vendor to submit to demonstrate the successful experience of the comparable equipment?

Thanks in advance.

 

[geesaman.d]

There is no fatigue analysis that is superior to having made hundreds or thousands of the component that have operated without failure over the course of years. If that is indeed true and they have adequate quality controls.

Is this component advertised and sold as being compliant to BPVC or another code?

 

[r6155]

If you have doubts, you can do the verification yourself, or hire this service.

Regards

 

[YuJie_PV]

@geesaman.d .
yeah. the cannon is stated to be constructed to ASME Code.
i concur with your opinion, just the issue lies in how to demonstrate that.
if i get the vendor's some oral promise and let it go, it seems ridiculous.

Thanks.

 

[IdanPV]

Ask them to show you the MDRs of the vessels constructed according to ASME.
The drawing number shall appear on the MDR, verify that is the same.
Try to get the oldest MDR you can get, if they have registered the vessels within the NB, that won't be a problem.

Ask them to show you the production drawings, and evaluate the effects of the design features of (a) to (f).

 

[TGS4]

I'm not opposed to successful service experience, and many different installations certainly helps to bolster the manufacturer's claims. I would highly recommend "trust-but-verify" because I have seen too many instances of where the manufacturer is not aware of in-field/in-service failures.