A bit of an update on the IR P-125-SD compressor from post #7.
It has some quirks, good thing it's not a critical piece I'm needing right away.
Like many "deals" there needs to be some sorting out of details and maybe some
fixing up here and there.
After clearing the 'wad' from the oil cooler, I did a test run and it behaves very well as far as oil temp now. So I installed another larger micron filter before the cooler.
Then I got into the (lack of) pressure problem...
It was only making about 70 psi and unloading at that point. Even tho the hour meter says 135 hours, it's apparent someone has been fiddling with this unit.
The hour meter actually works, and a buddy pointed out that the lack of dirt, and the way the engine starts and runs so well may indicate that it is actual hours.
After some research and repeated head scratching, I spotted a spacer in the parts diagram that sits under the unloader spring.....spacer was MIA. So I made one up from Alu. bar stock and installed it. Also the throttle screw was backed off, and with a screw compressor, pressure is a function of RPM. More adjustments and I have easily obtained the 100 PSI unload point.
Problem is, as you open the service valve (air outlet valve) the pressure drops all the way down to exactly 50 PSI before the throttle opens and output increases.
That is not acceptable to me. I want a 80-100 or better yet a 90-100 PSI range.
At this point I have done considerable research, asked questions, talked to IR service
center techs on the phone, etc. and I can't figure out how to raise the "load" set point. I've been told a shop service manual is not available for this unit, only a parts manual which I have. I've had the unloader-modulating valve apart and inspected all the parts for wear and problems. It's not very complicated, and there aren't many parts in the assembly.
This unit is a 1985 year of manufacture, and supposedly was made Doosan.
I'm at the point where I'm questioning the engineering that went into the unloader mechanism. Like....did it always just work this way? It may have, and an operator with a Jack Hammer might not even notice the drop to 50 PSI when he pulls the trigger on the hammer, and at 50 PSI the throttle kicks up, RPM comes up, and then he's hammering at 80-90 PSI.
What puzzles me is, I've studied other unloader's on other screw compressors, and they seem way more complicated, and contain many more parts.
Also there are key components seen on most all screw compressors that are missing (from the factory) on this unit. No Minimum Pressure Valve, No Output Check Valve, No oil cooler Thermostatic Bypass Valve. It's like they left out parts to keep the price as cheap as possible.
I'd sure like to find another one of these units and test it to see if the pressure drop is similar. If it comes to a worst case scenario, I'm already exploring options, and have a plan to add some parts to enable it to unload electrically (12VDC) with a pressure switch similar to most electric motor driven compressors that have the "constant run" setup.
There is an IR plant not to far from me, and I've been told about a retired engineer that worked in the compressor research lab. I'm going to track him down and see if he'll let me pick his brain a bit.
Sometimes a piece of equipment requires some sorting and patience before it settles down into something useful. I get that. Been there-done that more than once.
The part I dislike is when Mr. Murphy feels he needs to come work along side me and "help".....
Like when I was doing some testing and a piece of rubber weather stripping worked loose, and wormed it's way into the oil cooler fan shroud...
I heard a "bang" and it turns out the end of the weather strip went INTO the plastic fan and cleaned 7 of the 8 blades off of it.
Now I've gone to the bone yard, and have a steel fan off of a S10 pickup I'm building a hub for.
Problems, problems....but soon it will settle down, the Gremlins and Murphy will get their fill and move on....
I never give up, but I'm (still) glad the previous owner did!
