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Cass
08-07-2003, 03:26 AM
I need a super precision air pressure regulator such as made by Moore Products, Fairchild or Bellofram. These pressure regulators are pretty expensive and I wonder if anyone knows of a surplus place that might have something like this that is used. Ebay has nothing interesting. 250 psi. supply, regulation from 0-150 psi or so. Model 41 Moore Products (now owned by Siemens) is an example of the type of regulator I am talking about.

Ragarsed Raglan
08-07-2003, 11:21 AM
Cass,

I was looking for something similar a few years back, top dollar job with a bottom dollar budget (don'tcha just lovem!).

I finished up using a cheap adjustable PRV, but to reduce the hysterysis when the valve cracked, I set up a simple bleed type needle valve to control the flow. This stopped the PRV 'chattering' and when connected up to a high accuracy gauging system allowed the pressure fluctuations to be kept to an absolute minimum. Takes a bit of time to set up for each pressure but once there it was as good as any megabuck PRV.

RR

Cass
08-07-2003, 12:11 PM
I need about 10 cfm capacity at 130 psi. The object is to completely eliminated pressure variations resulting from compressor cycling from about 150 to 190 psi. I have lots of standard pressure regulators and needle valves but I don't understand how your idea works. My expensive pressure regulator is sticking someway. I have someone looking for a rebuild kit for a Moore Products Model 41. I have several precision regulators but all of them have a lower regulation range (1-60psi) than I need. A very small variation in pressure makes an unacceptable error in the parts.

Bruce Griffing
08-07-2003, 01:51 PM
If you can't afford a fancy regulator how about two in series? You would loose a little pressure drop, but the first would keep the input to the second about constant. Just a thought.

Shed Machinist
08-07-2003, 07:48 PM
That is about what i was thinking with 2 in a series. But would it be worth it for a homeshop? (really important)

Cass
08-07-2003, 08:54 PM
I have a lower cost pressure regulator downstream from the precision one that seems not to be working very well. The pressure variations I am concerned with are small enough that the less sensitive regulator never sees them. The precision regulator is still working but not very well. My suspicion is that with two just average regulators in series the slight variation in pressure from the first regulator would be small enough that the second regulator of the same quality could not respond to them. It might be worth a try to put a standard regulator up stream from the precison regulator if there were some wild swings in pressure such as some one using a blow gun. I don't have that problem at this time but it is something to think about. A standard technique for protecting against the blow gun disturbance is to put an air tank in the line next to the sensitive equipment to give some capacitance. I have the tank but have not installed it yet.

Rich Carlstedt
08-08-2003, 08:39 PM
If control is the issue and cost is not, then consider a variable (VFD) speed compressor..it would eliminate the cycling...

You may also want to add a spring loaded valve like a safety valve in your line so it would "bleed" off anything say over 130#
Regular safety valves "pop" and would not work, but a sensitive bleeder could be rigged for maximum pressure

More tank volume always helps !