gas blanketing pilot operated regulator

[hadiamini]

hi everybody

i am in doubt about action of low pressure gas blanketing pilot operated regulator (Fisher Type 1190)
this PCV is on service for N2 blanketing for AST( Heavy end Hydrocarbon-S.G=0.8), Set point of this PCV is .008 Barg
but in operation, this pressure not acheived, and the tank pressure decrease until to .004 barg
i want to know why this problem happend, and how we can improve the function of PCV

for more information, below datas are in PCV Data sheet

size and type : 4 inch 1190
allowed Max Diff. Press. : 8.6 bar
pilot type : Y191
N2 inlet pressure : 7.o barg
N2 outlet pressure : .008 barg
N2 flow rat (Max/normal) : 7171/3094 Nm3/hr
Sizing Coefficient Cv (Max/Normal) : 77.182/33.124

 

[unclesyd]

Look at the data sheet for the valve and check the output pressure operating band. All these valves have a very specific pressure band that they will operate in. It just might be that this valve's pressure band is to wide for what you are try to do.

 

[Homayun]

it seems to me that the PCV is simply too large for this service. REducing the pressure from 8.6 to 0.008, with a 4" valve seems too large to me. The valve may not be able to regulate the flow properly. I would definitly check the size of the valve.

I did a quick calculation with our program and came to a 1" valve with a CV of 15. I think the valve is operating simply out of operability.

Hope this helps

 

[JLSeagull]

I have not looked up these models. However, the ACE series regulators are recommended for tank blanketing.

 

[hacksaw]

the valve cannot keep up pumpout i.e. hold setpoint with proportional only