Transient pressure
Transient pressure
(OP)
Hi,
I have a pressure vessel designed for 16 Bar, but it will see a transient pressure of 18 Bar for a short period of time due to a pressure surge on pump shutdown.
Do I have to design the whole vessel for the 18 Bar pressure or is there some guidance on allowable transient pressures ?
Any help is appreciated.
Thanks
I have a pressure vessel designed for 16 Bar, but it will see a transient pressure of 18 Bar for a short period of time due to a pressure surge on pump shutdown.
Do I have to design the whole vessel for the 18 Bar pressure or is there some guidance on allowable transient pressures ?
Any help is appreciated.
Thanks





RE: Transient pressure
If this is an ASME VIII vessel, thou shalt design for all forseable conditions, not just normal operating. Since you are forseeing 18 bar, the DP on this vessel should be 18 bar plus a reasonable margin.
Piping on the other hand... if its B31.3 there is an allowance for short term loadings.
jt
RE: Transient pressure
The vessel code is PD5500, but I have seen some transient allowances on pipework and in particular plastic pipes.
I just wanted to know if there was any similar guidance on vessels in general, or if as you say thou shalt ......
RE: Transient pressure
There is very little safety margin in the assigned allowable stresses for pressure vessels built using using the PED pressure equipment directive, compared to the safety margins provided 40 yrs ago. The code may allow some overage during safety valve lifting events, but the exact amount is defined by code, and includes other pressure inaccuracies such as relief valve accumulation and error in setting the relief pressure. So, except for steam hammer ( 0.5 second duration)type events, overpressures above the code permitted relief vale overage is not acceptable.
RE: Transient pressure
RE: Transient pressure
Regards,
Mike
RE: Transient pressure
If the vessel also has to conform to the PED then you have to consider all possible loads to comply with the Essebtial Safety Requirements (of course being design to PD5500 does not automatically mean that it has to be to the PED as well, only if it is being used in an EU member state).
UG-22 is not relevant to PD5500, that's an ASME reference.
RE: Transient pressure
RE: Transient pressure
RE: Transient pressure
RE: Transient pressure
The surge specialist can't seem to design out the return surge with a return bypass, as the vessel is considerably more expensive if we go over 16 Bar I was looking for a way out.
RE: Transient pressure
Where does the surge eminate from? perhaps if a pump you could add a flywheel and increase the moent of inertia. If from a check valve change to a non slam type or if valve closing time then consider vave stroking times to change the system dynamics.
Check out www.pipingdesign.com for some papers on mitigating surge.
RE: Transient pressure
I would get more quotes, what size vessel is it?