Hydrostatic/Hydrotest Pressure as per UG99(b)
Hydrostatic/Hydrotest Pressure as per UG99(b)
(OP)
Hello,
A client of mine has their own regulation that imposed Manufacturer to use 1.3 x Maximum Allowable Pressure (MAP), however they are now requested to use 1.3 x Maximum Allowable Working Pressure. They claim it will reduce the cost, but I failed to understand why. Thickness is determined by Design Pressure, not MAP so how is this possible?
Thank you for your reply.
A client of mine has their own regulation that imposed Manufacturer to use 1.3 x Maximum Allowable Pressure (MAP), however they are now requested to use 1.3 x Maximum Allowable Working Pressure. They claim it will reduce the cost, but I failed to understand why. Thickness is determined by Design Pressure, not MAP so how is this possible?
Thank you for your reply.





RE: Hydrostatic/Hydrotest Pressure as per UG99(b)
RE: Hydrostatic/Hydrotest Pressure as per UG99(b)
RE: Hydrostatic/Hydrotest Pressure as per UG99(b)
I guess this is the reason why your client made the comment like that.
RE: Hydrostatic/Hydrotest Pressure as per UG99(b)
Well, this is a circular argument. Increased thickness to accommodate MAP based hydrotest leads to increased MAP...
With a tall tower wind or seismic can often require an increase in plate thickness. But only at the bottom. I've never seen wind or seismic govern the top shell course of a multi-course column. Thus, MAP for the vessel would be set by shell courses near the top, and the thicker shell courses at the bottom would have no influence on this.
My company's spec's use the MAP based (UG-99(c)) approach but we allow for the hydrotest pressure to be reduced in order to not exceed specified maximum stress levels. This is not unusual and there are several operating companies and major E&C's that take this approach. If this job happens to be for my company, I can state with absolute certainty that the plate thickness increase is not aligned with the intent of the spec. I'd suggest that asmediv1and2 ask their client check with the author and second sign-off on the specification for clarification.