Tuesday, December 13, 2011

Air Compressor Drain Valves

Where I work, we have a big Campbell-Hausfeld air compressor. It's a 5 hp, 80 US gallon unit, and we tend to be a bit lackadaisical about draining the condensed water out of its tank. Every couple or three years we get around to thinking about it.

The other day, the boss came in with a new drain valve for it. (The drain valve that's in it leaves a bit to be desired.) I quite like the looks of the valve he bought; it looks to me like a well-thought-out, well made bit of gear. It's a Porter-Cable "PDRAIN-14M". Here's a view of it.

When I first looked at it, I wondered, "Where are the 'wings' for cranking it open and closed with? There's just that knurl on the end of it." I cranked it open and it made sense.

It's fully open in the photo. Note that the valve has an O-ring doing the sealing, not a metal-on-metal stem and seat, so no great amount of torquing is needed to open or close it -- a very nice bit of engineering, that.

There was just one little problem with installing it -- it has a 1/4" NPT threaded body,[1] and the compressor takes a 3/8" NPT bodied[2] valve, like so.

A reducer would be needed to install the Porter-Cable item in place of the original, and that would bring the valve even closer down to the floor, which it's quite close enough to already. The boss will take the Porter-Cable valve back to the store, and see if they have a 3/8" NPT Campbell-Hausfeld part.

The original valve in the above photo has a nicked valve stem, so it leaks a bit. Wrapping the stem's end with Teflon tape before reinstalling and closing it takes care of the leak, but with that bit of hassle thrown in, the thing may as well be replaced by a plug. When the tank needs draining, unscrew the plug and there's your drain opening.

Anyway, the tank is now drained. I got about 1.5 litres of remarkably clean water out of it that had accumulated in about three years of operation.

If we all get past 2012 intact, maybe I'll have another go at it come 2014 with a replacement valve that fits -- or maybe just a 3/8" NPT plug. Whatever.

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[1] Hex is 9/16" A/F.

[2] Hex is 11/16" A/F.

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