pneumatic pressure adder

[pesy]

Does anyone manufacture a pneumatic pressure adder?

I have 2 pressures that I want to add together to provide a pressure signal to a Siemens SKP20 SSOV/regulator.

One signal is about 4"WC (natural gas) and the other varies from -0.5" to -2" WC (air). I want to add the two together and provide a modulating signal of 2" to 3.5" back to the regulator.

Alternatively, I want to take the -.5" to -2" pressure and invert it to a positive pressure for my signal.
(i.e. -5"=> +.5" and -2" => +2")

3rd option is to use some sort of pressure regulator that has 2 inputs. I have another available pressure source that is about 9-10"WC. I could use that as my "power" and regulate it down to my desired control signal (2-3.5") using the aforementioned pressure signals. Since this is a closed system however (no flow once the pressures are stabilized), the regulator would have to be a lock-up style.



Pesy

 

[MintJulep]

I'm sure it exists. Google for pneumatic logic. I have some catalogs in the office, I'll try to remember to take a look on Friday or next week when I get back in.

However, I am worried about mixing natural gas and air in the same device, especially if the air is below atmospheric pressure.

If you have an internal leak the gas will get sucked into your vacuum system. Potential BOOM. Check the codes.

Alternately you could do independant pneumatic to electric transducers on each, process the resultant electric signals, then go back to electric to pneumatic.

 

[tygerdawg]

Like MJ, I'm sure that pneu adders exist although I've never used them. You could do this electronically. Use a pressure sensor with analog or digital value output for each, send signal to a cheapo controller to do the math, then output a another signal to a third regulator.

TygerDawg