Compressor questions

[Jimmer]

Normally the auto stop switch which installed on the shop compressors have combined with a unload valve, when the tank pressure reached to the set pressure the auto stop switch will trigger and cut off the power for the drive motor until the tank pressure dropped to a certain level the switch will reset and turn on the motor again, when the switch getting to rurn off it when the pressure reached to the set point, at the same time the working arm of the switch will also press the unload valve to release the pressure which remain in the section between the compressor discharge port to the check valve of the tank to help the compressor can be get a easy start up.

We are not call it as auto drain valve but just unload valve.

I understand how all that works, as I've built a couple of 60 and 26 gallon shop compressors for myself and friends. I'm interested in how these applications of pressure switches and unload valves specifically apply to high pressure scuba compressors.

 

[pp-1-3-5-7-9]

I understand how all that works, as I've built a couple of 60 and 26 gallon shop compressors for myself and friends. I'm interested in how these applications of pressure switches and unload valves specifically apply to high pressure scuba compressors.

The attached picture have show with a typical configuration of a normal HPA compressor, just as for your reference.

Certainly, if the system is for breathing purpose like scuba then an air filtration canister will need to be add to this configuration.

 

[Jimmer]

Thanks, that diagram explains a few things.

 

[Waterskier1]

I have a follow-on question to this. Once the desired pressure is reached, is the HPA compressor's power source (petro engine or motor) shut down/turned off automatically? Or, is excess air bled off until manual shutdown. Specifically, if I am filling a tank, and I reach 3000 psi, and I close the whip valve, bled the whip to connect to another tank, presumably the compressor output will rise to the relief valve setting (3500 psi?). I'm sure I don't need to shut down the engine to switch tanks, and then restart it when the next tank is connected, but I'm not sure where the excess air pressure goes, or should go.

 

[Jimmer]

Well if it's a fully automatic electric compressor, like most dive shops use, the electric motor will be shut down when the pressure switch hits its preset pressure.

 

[cool_hardware52]

I have a follow-on question to this. Once the desired pressure is reached, is the HPA compressor's power source (petro engine or motor) shut down/turned off automatically? Or, is excess air bled off until manual shutdown. Specifically, if I am filling a tank, and I reach 3000 psi, and I close the whip valve, bled the whip to connect to another tank, presumably the compressor output will rise to the relief valve setting (3500 psi?). I'm sure I don't need to shut down the engine to switch tanks, and then restart it when the next tank is connected, but I'm not sure where the excess air pressure goes, or should go.

If the output pressure exceeds the setting of the pressure switch the motor will be switched off.

The relief valve is a redundant "failsafe" that vents pressure if the PS fails.

Relief valves are often also present at other points in the system.

My compressor differs a bit from the diagram posted above in that the pressure switch senses the pressure in the filter tower ahead of the Back Pressure regulator and check valve, and each of the filter towers has it's own burst disk.

Tobin

 

[Waterskier1]

Does this hold true for small portable gasoline powered compressors too? I haven't got mine yet, but for some reason I didn't think I'd have to shut off the engine, disconnect the tank, hook another tank up, start up the engine again. Maybe that was just a big AssUMe-ption.

 

[pescador775]

I would be surprised if a gas engine compressor had auto shutdown. Did you buy it from Compressed Air Specialties or Brownies? Hard to tell what they might be installing on Yacht compressors.

 

[Waterskier1]

I would be surprised if a gas engine compressor had auto shutdown. Did you buy it from Compressed Air Specialties or Brownies? Hard to tell what they might be installing on Yacht compressors.

I haven't bought it yet, that will probably happen tomorrow. It's a custom made Stewart-Warner with a Honda gas engine. But, I don't think the new Colti or Alkin portable gas powered compressors are any different. I one I'm buying is the one I asked about in this thread.

BTW, I just joined the Yahoo group, but since this was being discussed here, I thought I'd ask here. Now that I think about it, I think the owner said you just open the coaloessor (sp?) vent valve and let the compressor run, while changing tanks....does this sound right? Should I every decide to bank air, I know I'd have to do something better.

 

[frogman62]

I have a slightly different take on the fittings issue which has served me well for over 40 years.
If it is wet or moist air, & prefilter, I use stainless tubing and stainless fittings. When it is in a storage system and after the filter and the air is dry , I use steel hydraulic fittings and most always AN 4 size, since air flow is really not restricted when flowing at 3-4000psi through a 1/4 in stainless tubing.
Check my web site (sheldensportinggoods.com)and consider joining our yahoo group (compressor_team). We have good technical members who are willing to help with information and parts if you need them.
Jim Shelden