Compressed Air Drain Valve help

[zip95864]

Hey there guys,

I have a simple compressed air tank but was thinking of adding an auto drain valve so I never need to vent the air.

Would something like this work from McMaster Carr? Better recommendation?


Compressed-Air-Activated Moisture Drain Valve

Piston-powered valve automatically drains moisture each time your compressor cycles. It is activated by compressed air via a 1/8" NPT female pilot port (no electricity required).

Connect to your aftercooler, moisture separator, compressed air tank, dryer, or filter. Body has a rugged cast aluminum construction. Max. temperature is 150° F. Max. pressure is 200 psi. Inlet and outlet connections are NPT female.
Overall Size
Discharge
Cap., gpm Pipe
Size Ht. Wd. Dp. Each
0.25 1/4" 3 3/4" 2 1/8" 2 1/8" 4919K13 $50.81


http://www.mcmaster.com/#standard-moisture-removers/=frhza5

 

[PT Doc]

How long does it stay open?

 

[Provincial]

This type works if you have an unloader valve that is operated by compressed air as the compressor shuts off. Commercial Ingersoll and Quincy compressors (and others) use a different system and these valves will not work with them.

 

[dwm]

I have McMaster-Carr 41645K48 (which is a Parker 06D1NA) on the bottom of my tank and I like it for its simplicity. It just works, and is easily serviced if needed. But note that I had to cut a hole in my rolling platform to accomodate it. The ****** is McMaster-Carr 5788T62.

 

[browntown]

^ How does that work? Does the weight of the water open the valve, then get blasted out?

 

[mattrogers]

My filter/regulator has the same sort of drain that dwm posted. It's a passive drain that uses the air pressure on a float to seal when there's no water, but the water will then displace the float, and drain until the float reseals. It's honestly one of the most clever things I've ever seen.

I know this is about auto-drains, but if you're just tired of bending down to undo the wingnut, you can install a pull-cord drain at the bottom of the tank and then fasten the other end of the cord to the top of your tank (or wall, or whatever) and yank on that for a few seconds whenever you remember. Significantly cheaper. If you have a semi truck dealership or repair center nearby, they should have 'em in stock for $5-$6. Or you can find 'em online and buy it while not wearing pants: http://www.compressedairstore.com/Model-DP-Pull-Cord-Drain-Cock_p_3160.html

Attached is a picture of where the pull cord drain attaches on the left hand side to the top of my compressor. The drain valve is on the bottom.

 

[diesel research]

When the compressor turns off, there is a small amount of air trapped in the cylinder.

The next time it tried to turn on the motor would have a much harder time to try to start a pump at dead stop with 150psi in the cylinder. So there is a purge valve that discharges that small volume trapped in the cylinder each time the compressor turns off. That purge activates the drain until it is done purging the cylinder. The whole tank doesn't empty because checkvalves prevent it.

 

[dwm]

^ How does that work? Does the weight of the water open the valve, then get blasted out?

Basically like Matt said. Or you can think of it like your toilet float, but instead of closing a valve when the water reaches a certain height, it opens the valve.

My rolling platform is just the right height for me to put a Tupperware container under it to catch the water.

My old Craftsman oil-free had the unloader valve actuated type, I think I got it at Harbor Freight a long time ago. Some of the fittings were junk and I replaced them. It worked, and it was useful when I wasn't moving the compressor around. But I didn't want a long tube running up the side of the 60-gallon vertical so I went with the simpler type I posted above. I recently removed the unloader valve actuated one from my old Craftsman, only because it wasn't all that useful anymore. Since that's now only my portable compressor, it's often on unlevel ground so I need to tip the tank back and forth with the valve open to get all the water out. I now just have a 5' whip hose with cheap blow gun on the drain via an elbow.