Mako K15 95

[Caveman17]

Hello, I hope I do not offend as I own a paintball field and use this compressor in that capacity.
I have browsed here and can see that there are folks here with much expertise and I hope to be able to tap into that as this is my first foray into the HP compressor world.
The issue I am having is after using this used unit for the last season it has begun to bubble air back through the case upon shutdown, sounds like the oil is boiling, but only until the pressure drops off. It seems to me I have a check valve somewhere that is not working, but without a manual, I have no idea where to begin troubleshooting. the folks at 5000psi (dot) com thought I might have a bad 4th stage, so I have just replaced that with no change in behaviour.
Also, what does the valve at the discharge do? It has the Barksdale pressure shutoff switch on one side, the discharge on the other, and an allen wrench/locknut adjustment on the top. It seems that adjusting this keeps my cascade from bleeding back through the pump, but I'm not sure how or what it should be set at.
Thanks in advance for any help, you guys are the gurus!

 

[Wookie]

The rectangular valve with the Barksdale on one side and the discharge on the other is called the priority valve, it extends the life of your breathing air filters, and is set at about 1700 lbs. You likely don't have breathing air filters if you are only using it for paintball, so the priority valve is acting somewhat as a check valve. You should have an actual check valve in the outlet too. These go bad every few years, and need to be replaced/rebuilt. The check valve is usually external to the case in the discharge piping. Without knowing what you have for filtration it is difficult to describe where to go looking for stuff to you.

Finally, is it a mako or a k-15. Mako designator for a 15 CFM unit is 5407, Bauer makes the K-15. Mako hasn't used blocks from Bauer since the 80's.

 

[Caveman17]

Thx for the reply. The plate on the case says Mako K15 95, but reading here I wonder if it is the same as a Bauer.
It does have the breathing air filters as it came from a fire dept. I have wondered if I could remove or bypass these.
So I need to look on the discharge piping prior to the filters for a check valve?
Thx for the advice!

 

[CraigAClark]

Picture(s) = 1000 words.

Craig

 

[Caveman17]

Ok, thx Craig, Here's a couple of pix.

 

[Wookie]

Craig is your man. However, the aluminum valve (gold anodized) between the short chamber (final separator) and the tall chamber (air filter) is your check valve. It is an aqua-environment AE-684. The check valve repair kit is a AE-684-8 and is available here: Aerocon Systems Aqua Environment. They will also have the priority valve rebuild kit (AE-211-12). It looks like that machine has a manual drain, which I have never used. You need to open the 4 valves on the drain block every 15 minutes or so, and open them when you shut down the compressor. Again, Craig knows far more about this compressor than I do, and will know exactly how to work the drain system. If it were my compressor and I were filling paintball guns, I'd keep a filter in the filter chamber, probably a Mako 1503, which is just desiccant, to keep my customers cylinders dry so that their guns don't jam up.

Frank

 

[Caveman17]

Thx all!
My son (who runs our paintball field) informed me that it is a K14 95, not a K15...
I'll go stand in a corner now...

 

[CraigAClark]

Indeed that is a version of a K-14. The last two digits of the block number will indicate what modification it is.

There are a few reasons that air will blow back through the oil regulator at shut-down. Worst case is that the final piston and liner are worn out. Final stage discharge valve is bad. The seat in the regulator could be worn, but you would see blow back in the sight-glass during operation as well. It is possible that the oil pressure is set too low for the final pressure the machine is running at, but again you would probably see blow back in the sight-glass while running. Did you make an increase to the air pressure switch and final safety when you put the machine in operation? Most of the machines at the time were only operating to 3600 psi and the oil pressure was around 750 psi. Once 4500 psi became the norm, the oil pressure was set to 850-900 psi.

Craig

 

[Caveman17]

Thx Craig,
We have made no adjustments / modifications to this pump, just put it into service. The company we bought it from said it was serviced and checked it out, and it has operated as expected for abt a year.
We just installed a new 4th stage piston and sleeve as that was thought to be the issue initially.
There is a clear oil tube that runs from what I think the oil pump must be, up to the top of the 4th stage (regulator?). We saw bubbles in the tube when the priority valve was set too high, but reducing the setting on the priority valve eliminates the bubbles, but doesn't change the backflow at shutdown.
The oil press runs around 800, and again, I don't know where or how to adjust that. Final pressure has been about 4800 (I will reduce that...).
Unfortunately this hasn't been a series of methodical troubleshooting steps, but a fairly mechanical novice performing trial and error with a hand on the disconnect...
I do savor your knowledge and appreciate ALL of the assistance.

I do have a booster we used to use. Is there any interest in those anymore?

Thx!

 

[CraigAClark]

Can you take a picture of the 4th stage? In the pictures you posted, the filter tower is blocking a clear view. This unit may have an older style regulator that screws into the final stage (probably what gave the impression of it being a K15 as they all used that style oil regulator), along with an oil sight-tube (another feature of the K15).

Craig