* P-185 plastic/rubber coupling breaking for a second time?

by Richard Ringuet
(Montreal Canada)

Hi, I have one of those Ingersoll Rand (IR) P185 tow behind air compressor. I bought it from an auction with 5000 hours on the clock.


We used it a bit and then the rubber coupling let go. We had the coupling replaced as well as the oil and on first use, the new coupling let go again???

We ordered a new coupling and replaced it for a second time and after start up, while warming up after 2 to 3 minutes the gear that fits inside the rubber coupling unlocked itself from the shaft (maybe it wasn't tight enough) and slipped inside the coupling disengaging the mechanism. And we feel pretty confident if the gear would have stayed in place, the coupling would have failed again!

While it warmed up, we could hear a whining sound and feel the motor had a hard time getting to speed, like it was over worked from the compressor end...

We understand this rubber coupling is there to fail first before major damages are done to the compressor section, but any idea what can cause so much strain in the compressor section either from air or oil to cause this breakage almost 3 times?

Thanks,
Richard Montreal Canada

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Nov 24, 2018
Something wrong...
by: Doug in s.d.ca.

Look for :

Pressure Regulator Adjustment Instructions

and check that, please. It's on page 54 of the manual I'm looking at. That may be key...

During the (attempted) warm-up, are you not getting any alarm or warning?

Nov 23, 2018
Something is wrong for sure
by: Richard form Montreal

Thank you Doug for the "very clear start up instructions" actually you recommended exactly what’s written in the operating manual (we forgot to read).

Here is what append, we made sure we had no pressure left anywhere before start up and we closed the service valves as recommended and the same thing happened. The motor wasn't able to get to speed.

We tried it several times without success. And then we tried it with the service valves open and on second try, the motor got to speed and we could close the valve to bring the compressor to "like" standby mode.

The coupling survived the testing and it was our entire fault when it unlocked from the air compressor before, too long to explain...

So, we understand the right start up procedure now but something is interfering in the process, we can't get a "standard" start up?

We are sort of cheating opening the service valves to allow the compressor to lower the load on the motor so it can get to speed and then we are in business! But if this way of doing keeps breaking the coupling, we are no better!

There has to be an explanation to this malfunction and forget about it in the "trouble shooting" section of the operating manual.

Thanks for any lead to identify our problem.

Richard

Nov 20, 2018
coupler fail?
by: Doug in s.d.ca.

"Actually, all the service air valves were open on start up and you could feel the air coming out at a good pace but very low pressure since the motor wasn't able to get to it's normal RPM."

Hmmm. Unless you have instructions to the contrary, you'd want to open the valves to make sure there's no pressure, then close them, then start, and after warm-up, press the service pressure switch, then open service valves as needed.

Please forgive me if this is stuff you know, but if you follow the above, the pressure should rise to 100 psi or so, and the inlet valve should close. If the pressure keeps rising, then there's a regulator/unload valve problem. If the pressure stabilizes, then the engine should be be running with nearly no load, and the coupler should hold.

Can you try it that way and see what happens?


Nov 19, 2018
Failing rubber coupling
by: Anonymous

For the record, we never had more than 10 or 15# air pressure. We took it apart today and we found the set screw had been tighten right on the edge of the key and just got loose on start-up releasing its lock to finally unlock the gear from the air compressor shaft.

We switched the gear around to get a good flat surface from that key and put it all back together but no more time to test...

I'll get back tomorrow with more info.

Thanks for the interest

Richard

p.s. again for the record, how is that gear supposed to be installed? Is the set screw supposed to be visible or not once installation completed? Now, our set screw is visible but before, it wasn't. It was behind that rubber coupling.

Nov 19, 2018
rubber coupling breakage
by: Richard

Actually, all the service air valves were open on start up and you could feel the air coming out at a good pace but very low pressure since the motor wasn't able to get to it's normal RPM.

We thought we tighted that set screw on the gear / air compressor shaft good enough but apparently not.

And before assembly, we rotated the screw and while a little heavy at first, it rotated good and no extra clearance from the screw, you could tell you were moving oil around.

Nov 19, 2018
P-185 coupler fail?
by: Doug in s.d.ca.

"after 2 to 3 minutes the gear that fits inside the rubber coupling unlocked itself from the shaft"

The driven/airend locked?

It sounds like you got pressure, but then it should have unloaded (if it ever loaded), and should have been turning freely.

Since it's "new", have you checked that the pressure relief valve is working, and/or did you notice what the pressure was when it broke/nearly broke?


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