3 replies to this topic

[AndyChemEng]

Hi,

 

I'm looking at the pressure requirements for a new liquid ring vacuum pump system and I noticed that the existing one has an 'Administrative Process Control Procedure' (APCP) valve to the vent header to prevent overpressure.

 

The only recognised case of overpressure is by external fire (6 barg rated system with a volume of 90 litres). 

 

My question is, when is the use of an APCP valve acceptable? as I'm struggling to find any information on their use over a bursting disc/SV set-up?

 

Any advice is much appreciated.

[SawsanAli311]

Hi,
If APCP you are referrig to is the locked open valve, as far as I remember, relying on adminstrative controls for non fire overpressure protection would be allowed if the pressure resulting from the overpressure scenario would not exceed the corrected hydrotest pressure otherwise it won’t be acceptable.
I dont think that fire case protection can be relied only on adminstrative controls as the only mitigation measure, a non spared PSV sized for fire case would be needed for a live system. However, If the equipemt is isolated, depressured (for standby equipment) the use of valve locking as adminstrative control is accepted.
Considering your system is 90 L (less than 500 L) then if fire is the only overpressure scenario and the boiling point is more than the ambient temperature , there is no requirement for psv.

[AndyChemEng]

Hi SawsanAli311,

 

Thank you for your response. 

 

You mention that 'Considering your system is 90 L (less than 500 L) then if fire is the only overpressure scenario and the boiling point is more than the ambient temperature , there is no requirement for psv'. 

 

Fire is the only overpressure scenario identified and the boiling point is more than the ambient temperature.

I was wondering where this statement (less than 500 litres) originates from?

 

I'm aware of the 250 bar*litre criteria in PSSR but if the pot is rated to 6 barg, which would make this system equate to 540 bar*litres?

 

Andrew

 

 

[SawsanAli311]

The criteria given is based on Shell standard.