Gents,
I bought this 1982 Campbell Hausfield 2 stage 80 gallon, 5 Hp air compressor. It runs well appears to but a few odd things I need answers on. The bottom of the tank doesn’t have a drain petcock.., it has a pressure relief valve that the factory cable attaches to that and goes to the pressure relief valve on the top of the unit. I did find a query on Google that confirmed these old CH big compressors were set up like this. The bottom valve leaks, needs replaced, granger couldn’t help me, wondering a couple things.
1. Does anyone know where I may aquire this part?
2. Can I just put a drain petcock in the bottom and eliminate that relief valve and just run off the top one?
I did take a bore camera to see how much rust is in the tank, nothing up top, obviously scaly on the bottom.Curious how the tank drained with just a pressure relief valve on the bottom?
Any help would be appreciated, see pics






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That isn't the drain valve (below)? If not, what is it?

 

That (below) looks like the pressure relief valve. Which would in many air compressors be mounted top side. I'm not sure what the metal/plastic cased lanyard is all about. But, yeah...looks like that lanyard is attached to the pressure relieve valve "ring" (which you pull) and maybe someone installed it to remind themself to open the tank drain valve each time they bled the compressor at the relief valve? Not sure.

 

No as stated , this is a factory pressure relief valve on the bottom, attached by steel cable to another factory relief valve on top. It has two relief valves, no drain petcock. Thats my question? The bottom one is bad, can I just put a drain valve nd run off the top relief valve? Or wher can I find the correct bottom relief valve to replace? Again I am curious how the tank was drained unless once pressure was at zero and the bottom relief valve just opened up to release moisture?

 

I would imagine the bottom pressure relief valve is junk. All the crap collects at the bottom of the tank, right where that valve is located. I bet if you remove it, you will find it gummed up.

As long as it has a pressure relief valve somewhere, and it’s of the proper rating, I’d remove the one on the bottom and install a real drain valve.

That’s my opinion, but I’m not an expert of compressors. If there is an expert in readerland who disagrees with me, I’m perfectly content to retract my comment and let the experts educate us.

 

I pulled the bottom valve out, seemed to work fine, not gummed up. I used a bore scope to look at the bottom, of course scaly rust like all vertical tank bottoms. Once I get it figured out on pressure relief valves, placement etc I probably should do a hydro test on the tank

 

I wouldn't put faith everything posted to the Internet & located on Google is fact. The bottom valve has no pressure ring, as can be seen clearly in the top pressure relieve valve. I recognize some of these old beasts did not incorporate what has been commonly referred to as a "petcock". I remain suspicious & believe the bottom valve warrant additional examination. Remove the valve and validate for yourself. The very bottom of the pressurized tank would be (IMO) the most unlikely location to place a pressure relief valve esp. in consideration (1) a pressure relief valve already exists topside; and (2) a drain valve is always located at the very bottom of the tank.

EDIT: Well, Matt & yourself posted while I was researching and editing my post. Again, I'd be very suspicious that's a relief valve and not a drain valve. I'm not an expert. I'd love to see where you garnered the notion that's a bottom pressure relief valve, though.

 

Because when you pull on the factory steel cable attached to the bottom and top it releases air. And the fact that that’s the one that’s leaking. I have a video of it, but it’s too long to post on here. It’s where the leak is the bottom relief valve. It’s a relief, it’s not a drain peacock believe it. If you look at it, it has a ring attached to a release nozzle that goes up through the bottom of the tank.

 

Alright, I'm not an expert. PRVs (Pressure Relieve Valves) as they're called are rather simple but they do share one thing in common - I've never seen a PRV which did not contain a valve "disc" and a valve "spring". When incorporated into the manifold of the compressor they function as a, so called, emergency PRV - opening (I believe that's called overcoming stiction) when the pressure rises above ~10% of the set limit. I mean, maybe they installed two PRVs on this compressor. It's a fact the bottom valve is not incorporated into the manifold which means it doesn't function/operate as an emergency PRV. I just find it very, very odd they'd install a PRV at the bottom of a pressurized air tank where moisture which condenses into water is located. Well, good luck in your quest.

 

BTW, I am NOT referring to the circular "ring" I think you're referring to. I'm talking about the PRV air release ring. I'll find an image or use yours.

 

ok, all I can tell is that stem coming out of that pot or apparatus whatever you wanna call it on the bottom of the tank is spring loaded heavily spring loaded when you pull on that ring it releases pressure in fact it’s leaking right now that’s why I want to replace it. So you can call it what you want, but it’s not a Petco and it is a factory piece

 

Instead of ring, I should have referred to it as an additional collar w/ an orifice. Now, there truly is a difference between an Emergency PRV and a std. PRV. An emergency PRV would be tapped into the manifold and contain a spring/disc. Your top valve is likely tapped into the manifold and operates as an emergency PRV. Again, I'm not an expert, I haven't seen a PRV at the location of the bottom of a air compressor tank but I believe what you're saying. None-the-less, you'd expect to see at least one orifice on a PRV to act as a vent to allow air to escape. To that end, the point I was trying to make is it doesn't appear to be a normal PRV. Again, good luck.

 

OK, OK...I'm learning something here. Very unusual still. A PRV located at the bottom of an air compressor tank - strikes me as odd. Can it be some type of dual action PRV/drain. I mean seriously, what engineer would design an air compressor tank with no drain valve? Huh?

 

This is fairly simple. This tank is huge. The top pressure relief valve is a high pressure relief valve. It's got vents to vent air in safe directions. The bottom valve, which does release air, is a different design. My theory is one of two things:

1. Either the idea was to vent the high pressure air, then get underneath it, hit the lower one for the last bit of air, then take the valve completely out and drain through the hole or
2. The bottom one is actually a liquid drain valve and just happens to vent air, too, when there is pressure.

I am of the opinion that it is #2. You vent the air through the top valve, and, with a little air left, pull the cable and the air and water shoots out the hole in the bottom.

The compressor I have has a screw in plug with a handle for a drain and a high pressure spring relief pull ring valve like this one. I would recommend taking a picture of the model, taking a picture of the working high pressure valve, and taking the leaking lower valve to a decent compressor store or real hardware store, source a new valve of the same type, and use it like discussed above that way you don't have to get under the thing to drain it.

 

Does the lower valve pin move side to side when you pull on the cabel or does it only move straight in/ out? In other words, Do you need to pull straight down on the cable to vent the lower valve? If it vents when you pull it side to side or by pushing it straight up, it is not a pressure relief valve. If it drains the tank when you pull the pin to the side, that IS the drain and that is why the cable it attached up top. You simply pull on the cable to drain the tank. The cable does not need to attach to the upper pressure relief, that was likely the most conveint place when these were built. The seals have likely gone so it is leaking. How long have you run the compressor? Some drains are designed to open at a low pressure. You may have to build up 5-20 psi before that lower valve closes.

 

‘When you pull the steel cable it activates the top valve and the bottom, so as Koda said it’s probably some type of dual assembly for pressure and water both. The bottom one bleeds out all the air, you can hear it when you power up the unit. It pumps from zero to 150 psi on the gauge in like 8 minutes, then you can hear the pump stop as designed and that lower valve is pissing air. Its a 1982 so wondering if I can find a replacement or just put a petcock on there to drain?

 

‘I believe your are correct, hopefully I can find a replacement..then onto hydro testing the tank. Old beast is a work horse

 

The lower one is not a pressure relief valve. It is a pull-type water drain as stated above. The give away is the fact that pulling on the cable up top opens it. The seals have gone bad which is why it is leaking without pulling on it. The reason the cable is attached to the upper valve is because the cable could be easily secured in the spring ring at the factory. Nothing more, and no connection to the operation of the pressure relief valve. Here is a link to a replacement, or you can remove it and replace it with the drain valve of your choice.
https://www.napaonline.com/en/p/TWDV...e_google&gQT=1

 

Thank you, you are the MAN!! I just ordered it, what a lifesaver..

 

As mentioned in Post #15

 

see post 20

 

To clarify, I agree it's a drain. If there's pressure in there, it will come out, too, just by the nature of things. I do not recommend hitting it at anything more than minimal pressure.