Control Devices-NC25-1UK002 NC Series Brass Non-Code Safety Valve, 25-200 psi Adjustable Pressure Range, 1/4" Male NPT

I purchased this for an air compressor I bought which had an under-spec relief valve. This valve solved my problem, and I love that it is adjustable. Some common sense is required to put the valve together, it doesn't include any written instructions, but then again, if you do not understand how this valve works, and how to put it together, then perhaps you shouldn't be operating whatever it is that you are screwing this valve into. Hmm??? Regardless, adjusting the valve is as simple as squeezing the springs between your fingers. The softer the spring, the lower it's operating range. The springs are color coded so it is easy to identify them. Once you find the correct spring for the range you are seeking (in my case I needed the blue spring 100-200 PSI), it is as simple as dropping the spring in, and turning the adjusting knob until the valve attains the pressure you are seeking. In my example, I screwed in the knob about 3 turns, and cranked on my compressor. At about 100 PSI the valve discharged. I then screwed it in another 1.5 turns. The compressor shut off at it's operating pressure of 150 PSI. I slowly backed the knob off until the valve began to discharge air, and from there screwed it back in a half turn. Works great! Compressor reaches it's operating pressure, and connecting loads, and adjusting the feed regulator does not discharge the valve. I'm extremely pleased with both the valve and the compressor!

I bought a cheap pressure paint pot from Harbor Freight Tools and the pressure relief valve kept blowing at 30 psi. I bought this as a replacement and it works perfectly. It's very easy to dial in the exact pressure for which you need it to release.

It's a solid piece that provides effective protection against over pressurization. It seems to be geared towards professionals or those with experience who can manage without any info. I used it to prevent excessive build-up in the supply line of an air delivery system for the short amount of time when all its valves would be intermittently closed. As long as it's over 25 psi, with some adjustments and tinkering you can get the cut-out and cut-in pressures you want. I think it should come with more information to help those less inclined with achieving these setting instead of having to refer to that provided by other reviewers.

I had to do a lot of research to determine that this SAFTY VALVE is a great solution to my Harbor Freight Pressure Pot for casting resin conversion.4 Color Coded Springs - Yellow 25 to 50 psi, Red 51 to 100 psi, Silver 101 to 150 psi, Blue 151 to 200 psiChange the internal spring to the red spring, set the compressor to MAX at 60PSI. Open the valves to the pot from the compressor with the valve installed. Open the valve until it starts to release pressure. Then screw it in a quarter-turn.Discharge the pressure and start over, but increase the compressor pressure to 70PSI. Wait for the pressure to rise. The valve should pop around 60PSI. If not, adjust the valve open a bit and retest.Once you are happy with the pressure for the safety valve, set the HF pressure regulator to max something below the safety valve.

impressed with this product. It comes with 3 spring to cover the 25-200psi range.

Came with the blue 150-200psi spring installed, my 60gal compressor wants 140psi max, so I installed the smaller "gray" spring that is good for 100-150psi. Disabled my electric pressure shut off, ran the compressor up to 155 psi, then slowly backed off on the adjustment until it triggered as I had it too tight. I let it bleed pressure until it shut itself off, backed off the adjustment a little more, let the compressor fill the tank again and this valve released at exactly 150psi. Tightened down the locknut, enabled the electric cut off and tested again. My electric cutoff triggers at 140psi, it triggered like normal, I disabled it, let the compressor keep going, and this valve triggered as it should at 150psi.So all in all works as it should. Things to keep in mind below:It's a spring, so if you crank the adjustment knob all the way down you can completely compress the spring and it'll never release. This is the same as if you just blocked off the pressure relief entirely, so start with the adjustment only screwed in a little and adjust to raise the pressure.When it pops it'll bleed off about half the pressure needed to activate. Mine activates at 150psi, it'll stay open to bleed pressure until about 75psi. Yes, this is annoying, but it's not meant to be a pressure control, it's meant to be a safety valve to keep your tank from exploding and you from dying.I don't trust anything fully, so I'll test this on a monthly basis to ensure it still works as designed. Will update this review if any changes are needed or made.

Very disappointed with this little relief valve as the springs supplied DO NOT match the pressures in the product which I relied on. I could not calibrate to the required pressure as supplied. Further, the "color coding" of the springs was not different. This was a returned item which I knowingly purchased and I suspect the springs of other valves may have been returned from an earlier purchase of this valve. Now I have wasted critical time for this project.

Fit was OK, but the accuracy seems to drift... Is doing job, but I am keeping an eye on it...