Danlap
Mechanical
- Sep 17, 2013
- 321
Good day,
I was wondering if someone have similar experience with pinhole and maybe have done some root cause analysis. Subject is Monel globe valve for HF service.
Fully aware that Monel valves have common challenges such as casting shrinkage or micro porosity which later susceptible to be 'attacked' by HF. UOP and MSS SP-160 committee relentlessly trying to incorporate additional testing criteria to tackle this issue.
Green spot is beginning of the leakage
black remarks
What struck me the most is that we have two incidents on two different brand however on identical location above the bonnet.
Have dealt with pinhole several time but mostly on vena contracta body area due to flow/turbulence induced erosion, now I am clueless as bonnet/yoke is not typically subject for internal errosion.
Is this more about the nature of foundry process wrt residual stress, thinner wall thickness on this part, etc.?
Valves are 2-7 years old, creeping of HF into cracks are like timebomb. And cracks as well as weld repair sometimes cannot be spotted even with 100% Xray
Thank you for the brainstorming in advance.
Regards,
D
I was wondering if someone have similar experience with pinhole and maybe have done some root cause analysis. Subject is Monel globe valve for HF service.
Fully aware that Monel valves have common challenges such as casting shrinkage or micro porosity which later susceptible to be 'attacked' by HF. UOP and MSS SP-160 committee relentlessly trying to incorporate additional testing criteria to tackle this issue.
Green spot is beginning of the leakage
black remarks
What struck me the most is that we have two incidents on two different brand however on identical location above the bonnet.
Have dealt with pinhole several time but mostly on vena contracta body area due to flow/turbulence induced erosion, now I am clueless as bonnet/yoke is not typically subject for internal errosion.
Is this more about the nature of foundry process wrt residual stress, thinner wall thickness on this part, etc.?
Valves are 2-7 years old, creeping of HF into cracks are like timebomb. And cracks as well as weld repair sometimes cannot be spotted even with 100% Xray
Thank you for the brainstorming in advance.
Regards,
D
