+/- Differential Pressure

[BEMPE16524]

Hello Guys,

I'm doing a maintenance/modification on a hydraulic system for a subsea equipment. I came across few +/- differential pressure switches as you can see on the following diagram:

My question is why does the system need +/- pressure switch when in all time the system pressure will always be more than zero?
FYI, they are for the load sensing.

R.Efendy

 

[mk3223]

why does the system need +/- pressure switch when in all time the system pressure will always be more than zero?

In terms of instrumentation, the pressure switch is made with +/- functions and will be allowed for either applications, instead of using only in the subsea system.

 

[BEMPE16524]

that is odd because i can get much cheaper price of sensor without "-" function. is that mean there will be no issue if i use 0-4000psi sensor?

R.Efendy

 

[Compositepro]

Your DP transmitters (not switches) measure the pressure difference across the piston of the hydraulic cylinders. The pressure reverses when the cylinders reverse, so you do need +/-.

 

[BEMPE16524]

thought so. i have the price for that transmitter. USD4400 each. Where as a one way transmitter is around USD200++.
I may put all the transmitter separately from the valve pack. and for the +/- i may use 2 normal transmitter without minus and calculate the difference in the software reading.

R.Efendy

 

[gruntguru]

Not a good idea if you need accuracy or resolution around zero DP.

je suis charlie