3 replies to this topic

[3omar]

I want to check if the pressure used in the calculation of the 3% role is gauge or absolute?


pressure drop %=(Inlet pressure - outlet pressure)/(P inlet absolute or gauge) 

and there is  another question

Is the pressure value used in calculations is stagnation pressure or static pressure?

 

Thanks in advance.

[SIVAMOORTHY]

I want to check if the pressure used in the calculation of the 3% role is gauge or absolute?


pressure drop %=(Inlet pressure - outlet pressure)/(P inlet absolute or gauge) 

and there is  another question

Is the pressure value used in calculations is stagnation pressure or static pressure?

 

Thanks in advance.

Hi.. 

 

Pressure drop is based on your given inlet and outlet pressure unit... 

For example, if you consider 103 psi in inlet and 100 psi in outlet (whether it is gauge or absolute pressure, but it should be same for both ends), the pressure drop will be 3 psi per column/pipe length....  and the percentage pressure drop will be 3 %.  

 

and.... i think that it is stagnation pressure..

[latexman]

Why not look at the definitions?

 

"The total nonrecoverable pressure loss between the protected equipment and the pressure-relief valve should not
exceed 3 % of the PRV set pressure except as noted below:
— thermal relief valves (see 7.3.8);
— remotely sensed pilot-operated relief valves (see 7.3.9);
— an engineering analysis is performed for the specific installation (see 7.3.6)."  3% rule in API 520 Part II, Section 7.3.4.

 

"3.53
set pressure
The inlet gauge pressure at which the pressure-relief device is set to open under service conditions."  Definition in API 520 Part I, Section 3.53.

 

Gauge pressure = static pressure.

[fallah]

I want to check if the pressure used in the calculation of the 3% role is gauge or absolute?


pressure drop %=(Inlet pressure - outlet pressure)/(P inlet absolute or gauge) 

and there is  another question

Is the pressure value used in calculations is stagnation pressure or static pressure?

 

 

3omar,

 

The 3% rule (not role!) is based on gauge set pressure...

 

It's static pressure...