Rebuilding my Back Pressure Regulator (BPR/PMV)
- Last Fall when I disconnected the filter array from my compressor (so I could bring the compressor indoors for the winter), I noticed that there was air coming out of the BPR when I turned on the compressor. It's supposed to hold back air until the pressure reaches 1800 psi... This is in order to condense nearly all of the water out of the air before it reaches the filter array. Leaking here is not good. So, I ordered a BPR rebuild kit from August Industries on line. Complete illustrated instructions are included. Here's a "BEFORE" photo before I did the re-build.
- Here's another photo that shows the original configuration of air inlet, gauge and air outlet on the bottom of the BPR. Note the label on the side of the BPR says "1500 psi". The manual says 1800 psi and that's what it was actually running on when I did the BPR video last year. The rest of the parts you see to the left of the BPR are a check valve, a 3600 psi safety release valve, and a small bleeder valve.
- I have been bleeding some water out of the line using the little bleed valve at the lower left... So now I'm looking at the air outlet on the bottom and thinking, "Why should the air outlet be at the bottom where water is likely to drain?" Hopefully the reason there was still water in the line is because the BPR was leaking and after re-building, it shouldn't have water in the line anymore. Still, I resolved to put the air outlet on top of the BPR when I put it all back together. Okay so I disassembled the BPR and this is what I found (below).
- As you can see above, the old BPR valve seat has a lot of corrosion and is missing a backing washer for the grease packed O-Ring that seals it. The O-Ring is supposed to be packed with silicone grease because the seat actually moves in and out on its shaft. I cleaned up the inside surfaces of the housing and installed the new seat parts. I re-arranged the plumbing to put the gauge where I can read the pressure coming out of the compressor. And while I was at it, I changed the air outlet position to the top of the BPR as described above.
- The last step in the rebuilt process was to adjust the BPR to hold back air until the pressure reaches 1800 psi. So, I turned on the compressor and watched the needle go up to 500 psi and stop. Air was coming out. Turned in the BPR adjustment screw and it shut the air off until the needle climbed a few more hundred psi. I repeated this until it held back air up to the 1800 psi RIX specification. I then tightened the lock ring on the adjustment screw, turned off the compressor and drained the pressure with the drain valves. Closed everything up and turned on the compressor. It held back the air with no leaks right up to the 1800 psi mark and then released the air... maintaining the 1800 psi pressure level. I repeated this test a couple of more times to be sure it worked and the 1800 psi setting was consistent.
- Final Thoughts... The RIX SA3 and SA6 are named "SA" for "Sweet Air". If I understand correctly, the BPR and two water condensation towers removed water well enough that the Navy divers filled tanks right off the compressor with no additional filtration. The air was "Sweet" because the oil-less compressor had no oil induced taste or smell AND the air was slightly moist and comfortable for breathing... i.e. No dry mouth. This is why (I think) the pressure gauge was mounted on the BPR... Because the whip came off the BPR and the gauge read the tank pressure. Probably also why that check valve is there in front of the BPR... So that tank pressure wouldn't feed back into the compressor.
- I don't think there's any reason for me to put the gauge on the BPR because air goes from the BPR to my filter array, which has its own tank filling pressure gauge and check valve.