Kellogg american 321 air comp trouble

[Harleyman2169]

Hello all
First time post for me on this forum hope this is in the right category. I was given a 80 gal Kellogg american upright air com model 321. Had not been running for at least 15 years. Wired it up and it does run but air constantly blows from the unloader valve. Removed valve oiled it blew it out and still same problem. Compressor runs but runs slow then fast then slow with air blowing out this valve. From research the valve sounds bad? Should I replace the check valve as well? What else could do this? Really would love to have this running or should I sell or scrap it? Is it a safety hazard now that this giant is 40 years old?

 

[LS6 Tommy]

I would replace the unloader. If that works I would also get the tank hydro tested before putting it into service..

Tommy

 

[Harleyman2169]

Thank
Saw a valve online for 15 bucks. I know those old compressors are bulletproof but dont want the tank having an issue! Theres some surface rust on the outside. Have managed to get 100 lbs but not much more with the leak.

 

[quietsailor]

Thank
Saw a valve online for 15 bucks. I know those old compressors are bulletproof but dont want the tank having an issue! Theres some surface rust on the outside. Have managed to get 100 lbs but not much more with the leak.

If the compressor hasn't been ran for 15yrs there could be internal rust which you can't see and it causes a weak spot. The worst case scenario is a tank rupture which you do not want to be anywhere near at all.

Can you open the tank anywhere and get a good look inside. I know what I'm posting sounds like scare mongering but it isn't -- please don't run this tank at pressure until you've a) verified it has no or very little internal rust b) tested it hydro statically.

I used to work on ships and a large part of the safety documentation was pressure vessels - everyone thinks about and worries about the steam boilers but from talking to surveyors they said air vessels worried them just as much* as people tend to faithfully maintain steam boilers as they are scary (if they go wrong) but tend to forget about the air vessels as they feel "safe", after all we work with air tools every day don't we???

* = the funny thing was our air vessels were ran at 26-28 bar for starting the engines and the boilers only ran at 6-8 bar so the air vessels were rated much higher.

 

[Fixnair]

You mentioned that it slows down. Big hint here. That unloader valve is operated by a set of centrifugal flyweights inside the crankcase. When the compressor is running the flyweights extend outward and the unloader valve is closed. When the compressor stops the flyweights collapse and a pushrods opens the unloader and allows the head to relieve any pressure in it so next time it starts it will be unloaded. Slipping belts will cause the compressor to slow down and allow the flyweights to collapse & open the unloader. Adjust the belts to cure this.
If, When stopped, air continues to bleed from the unloader then the discharge check valve is leaking and needs to be cleaned or replaced. The 32
1 is a good little compressor.