Compressor Interstage Pressure Relief Valve Lifting

[larry4406]

I have a Puma TUE-7580 3 cylinder compressor that up till today has worked flawlessly for the past 10 years.

It is a a two stage compressor - Cylinders 1 and 2 are in parallel and feed Cylinder 3. There is a factory intercooler between 1&2 and 3 along with a pressure relief valve. Today this interstage relief valve started lifting.

I was painting in the garage with a spray gun today, 20' away. The interstage relief started lifting and I could see white paint marks spewing on to the compressor from its discharge (in the pics this is wiped off, sorry). Not sure why the filters did not catch this.

The interstage PRV is rated 70 psi per the stamping on it. This relieving limits the pressure buildup so the compressor runs non stop. If I hold the PRV stem in, pressure builds normally and then shuts off. There is the higher pressure PRV at the pressure switch at the tank so I was not endangering myself.

I assume the PRV fouled somehow with the paint droplets? It has been factory staked with a punch so I cannot disassemble it for cleaning.

Is it possible the reed/disc valves in the last stage cylinder or the check valve to tank have fouled?

 

[PCustoms]

I was painting in the garage with a spray gun today, 20' away. The interstage relief started lifting and I could see white paint marks spewing on to the compressor from its discharge (in the pics this is wiped off, sorry). Not sure why the filters did not catch this.

????

Are you saying you had so much paint in the air it sucked into the compressor and was going through the cylinders, then blowing out the relief?

 

[larry4406]

????

Are you saying you had so much paint in the air it sucked into the compressor and was going through the cylinders, then blowing out the relief?

Oddly that is is what it appears....

I was spraying white primer on some cabinets 25' away from the compressor. No cloud of paint in the garage - 16x7 door was open along with side service door.

I noticed the interstage pressure relief had lifted as it was audible. The relief port is aimed at the side of the compressor crankcase. There was some white paint residue there which appears to have impinged on the crankcase from the PRV discharge. Both air intake filters oddly are clean - there was some white dust on the interior of the air filter housing but the elements themselves are clean.



I am thinking its something with either the 2nd stage compressor head inlet valve or its gasket, stuck unloader, or tank inlet check valve. Linked threads below suggests these places to check when the interstage PRV lifts.
https://www.practicalmachinist.com/...y-valve-when-compressor-start-pumping-272337/
https://www.smokstak.com/forum/threads/leroi-dresser-600-compressor-stalling.149362/
https://www.practicalmachinist.com/...y-compressor-has-relief-valve-problem-336767/
https://www.industrialaircompressor... COMPRESSOR PISTON TROUBLE SHOOTING GUIDE.pdf

I will try to contact Puma today.

 

[redmondjp]

It's a leaky inlet valve on your second-stage cylinder. Pretty common issue - I've seen it myself twice. No clue on the white spray - I would start with removing that interstage check valve and looking inside to see how much white deposits are inside and go from there. If it really did **** in paint, it could have gunked up the reed valves so they aren't sealing properly.

Also check carefully for any air leaks past your filters - you should be able to see where the leaks are by heavier white deposits there where the air was flowing.

Make sure to post back and let us know what you found.

 

[Jswain]

Yep time for a valve job/clean and clean/replace/relocate the air filter

 

[larry4406]

Thanks all

I called Puma and they said that at 10 years, its pretty common for the inlet valve on the HP cylinder to go as it runs the hottest of the cylinders.

I ordered a valve plate assembly with gaskets ($31.65), a new PRV ($12.00), and new filters ($7.39 each). Their office in Memphis TN is working alternate shifts due to Covid so hopefully will ship out this week.

After looking at the unit more carefully, I think the white paint is a red herring. The blades of the compressor pully have overspray on it and this has carried over to and around the crankcase. I think that when the interstage PRV lifted it blasted the dust off clean creating the perimeter ring of dust/spray I observed which I (wrongly?) attributed to blow thru.

The threaded portion of the PRV and port were clean when I removed it.

The original interstage PRV was stamped 70 psi but they are sending one rated 100 psi. He said they up the rating on the PRV whenever they send out replacement valve plates. He had me run the compressor and report the tank pressure at which the interstage PRV relieved which was 120 psi. He said that with the new valve plate the compressor will discharge at a higher pressure and thus the reason they upsize the interstage PRV. Is this usual (pressure switch set points are unchanged)?

I will post pics and an update when I get the parts.

 

[larry4406]

Update 11/29/20

Ordered and received the valve plate assembly kit 3B13-AC0765. This kit comprises all of the gaskets between the cylinder and head and two reed valve plates on the last stage of the 3-cylinder compressor.

The upper plate was found to have a loose rivet which allowed the reed valve to be offset and thus not fully close off the port. Also there was a missing portion of the gasket between sides. Oddly one of the four head bolts was found loose, another just barely tight, and the other two needing a ratchet to remove.

Cleaned all of the gasket surfaces, removed the unloader piston and cleaned it, and reinstalled everything including the new interstage 100PSI PRV (Part Number 84006007). Back up and running properly.

The assembly of gaskets and plates was a bit tricky to install until I inserted finish nails into the head bolt holes and used them as alignment pins to hold the assembly while I fitted the head and head bolts one by one (socket head cap screws). The tech line would not provide torque specs for the socket head cap screws so I tightened them to what felt right.

I also replaced both air filters Part Number 1801.

 

[Jswain]

Nice job on the fix and good idea with the nails!!

 

[matt_i]

Thanks for the update, its great to see a follow-up post, many times the details are lost forevermore.

 

[larry4406]

Nice job on the fix and good idea with the nails!!

Thanks! Studs would have been ideal for this reason instead of socket head cap screws but I had to improvise. I think I got the nail idea from one of Zmotorsports threads.

Thanks for the update, its great to see a follow-up post, many times the details are lost forevermore.

I agree completely. I have found many threads of interest only to find no conclusion.

 

[nadogail]

I am glad to read of the decent customer service and your success in maintaining your compressor.

 

[metlmunchr]

Gotta say their parts prices are extremely reasonable. Seems like the standard procedure for many companies today is to price parts at levels where anything more than a gasket costs 1/3 to 1/2 as much as just buying a complete new pump.

 

[larry4406]

Gotta say their parts prices are extremely reasonable. Seems like the standard procedure for many companies today is to price parts at levels where anything more than a gasket costs 1/3 to 1/2 as much as just buying a complete new pump.

Frankly I was shocked (and pleasantly surprised) as well how inexpensive the parts were.

 

[Viper98912]

I'll be honest. I'm just impressed at the 3-cylinder setup. Puts my small simple compressor to shame.

 

[redmondjp]

I'll be honest. I'm just impressed at the 3-cylinder setup. Puts my small simple compressor to shame.

3-cylinder pumps aren't quite as common, but are out there - they come in two flavors - in this case, two primary cylinders pumping into one second-stage cylinder (2-stage pump).

There are also 3-cylinder single-stage pumps which look very similar - you can easily tell by counting the air filters - if there is one for each jug/cylinder, then it is single stage. These can pump 15-20cfm at 120psi or so on 5HP or a bit less.

 

[KenC]

Frankly I was shocked (and pleasantly surprised) as well how inexpensive the parts were.

Me too! I had a Devilbiss, cheaper model with the Italian made two cyl/two stage pump. Really common on several brands. It needed a valve plate and gaskets. About $120 bucks. Fixed it up and used it for 3-4 years and another valve broke.

Called to order another valve plate. Dealer quoted about 300 bucks this time. I now have a different and better compressor. One without reed valves.