Again -- Tried running the quincy compressor

I put the circuit on slightly bigger breakers and tried again. The
result is that my phase converter (17.5 HP idler capacity) is not big
enough to restart the compressor when PSI reaches 100. I do not suspect
unloaders, based on what I hear when it starts, unloaders do work.
This time motor overloads tripped, quite rightly. I would not try to
defeat them. The motor clearly was not doing well.
i
Reply to
Ignoramus20839
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If the pressure makes a difference, then the unloaders are NOT working, in some manner or other. Can you hear the unloaders cut out after the compressor spins up? There should be a VERY pronounced change in the sound of the compressor. Mostly it should make a whirring when unloaded, that changes to a deep rumble when loaded. Possibly, your phase converter is taking too long to start such a big motor with heavy inertia of the flywheel. You want the unloaders to wait until the compressor is fully up to speed, so the motor doesn't have to fight inertia plus pressure. The different sound my compressor makes can easily be heard rooms away when it switches between loaded and unloaded. (Actually, mine might be different, there are two pistons 180 degrees apart in rotation, and they are connected to one air filter. So, when unloaded, the air mostly shuttles back and forth between the two cylinders. Yours has a separate filter on each bank. So, it may still hum when unloaded, but the sound should get much louder/sharper when it is compressing.)
As for the overloads, you might check the voltage and line current, and see if your converter is holding up the generated phase under the heavy load, or if it is allowing the voltage to sag. A single-phase start will be REAL tough on a compressor load.
Jon
Reply to
Jon Elson
Will the motor take an empty tank up to desired pressure w/o exceeding FLA rating motor? Is FLA inside your phase converters capacity?
If so, you need to look at unloader system.
Wes
Reply to
Wes
It is not able to fully spin up when unloaders kick in. That's the issue. It starts spinning, accelerates slowly, then unloaders kick in, and it slows down, then it blows the overload.
Exactly.
You are spot on.
Are unloaders adjustable?
I am sure that the phase converter does not give enough 3rd leg voltage. I also feel that a little more idler capacity will make a differencwe. I could check, but I see little point, as I will be mounting an electronic drive on it anyway, hopefuly this weekend.
i
Reply to
Ignoramus3971
Yes, if it starts, it pumps to 150 PSI and stops properly as directed by the regulator.
Yes, running is OK, but starting loaded is not.
If I could adjust it somehow to close valves not 2 seconds, but 5-10 seconds into the run, I think that I would be fine.
i
Reply to
Ignoramus3971
I suspect your unloader sees head pressure coming up while not connected to tank so you are bleeding air as the compressor pumps. Eventually, as the head comes up to operating speed, the rate of venting can't keep up with the increasing rate of flow causing enough pressure to be developed to shut off venting and directly couple head to tank. Ed may need to do a rewrite on this :)
I'm thinking an electric valve and electronic timer in place of the head pressure sensing stuff that directly operates whatever valve connects tank to head. A guy into pneumatics could use a pneumatic timer too.
Wes
Reply to
Wes
Wes fired this volley in news: snipped-for-privacy@corp.supernews.com:
I'm thinking all you have to do is drill out the relief oriface so that the unloader doesn't close until a much larger airflow is felt. Alternatively, you could try a stronger spring on the poppet.
My shop compressor is a home-built with a Quincy head. It has a conventional unloader, and never struggles to start. For construction work, I have a portable Emglo with a "protracted open" unloader. The compressor is one of those high-speed types with a small motor, and needs to come up to speed before it can develop enough torque to run at pressure. The unloader doesn't close until the motor is almost at full rpms.
LLoyd
Reply to
Lloyd E. Sponenburgh
I am thinking I should just install that 25 HP electronic drive. If I was stuck with a phase converter, I would just add another idler.
i
Reply to
Ignoramus7291
On Fri, 26 Oct 2007 07:25:53 -0500, with neither quill nor qualm, Ignoramus3971 quickly quoth:
I understand that it uses hydraulic unloaders. Perhaps they have grime or jelled oil around them and simply need to be cleaned. I've never even seen the style, but that's the direction I'd look, FWIW.
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Reply to
Larry Jaques
On Fri, 26 Oct 2007 13:23:04 -0000, with neither quill nor qualm, "Lloyd E. Sponenburgh" quickly quoth:
If it were a Chiwanese hunka arn, I might agree. But it's a Quincy. I'd trust their engineers to come up with the best setup. Methinks it's a maintenance issue rather than a design issue. YMMV
Wouldn't that cause undue wear and tear on the components? (unless the original spring was weakened somehow)
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Reply to
Larry Jaques
The point is, unloaders do work. But the compressor does not have enough time to accelerate with my phase converter, until they rightly kick in. It accelerates, but not fully, and then they kick in in 2 seconds and it stops.
i
Reply to
Ignoramus7291
Well, it depends on how the things work. In most systems, air pressure operates the unloader. Apply air pressure, and a pin drops down into the intake port and tips the valve disc to hold the intake valve open. On many of the larger Quincy's, the unloader is operated by a valve that is controlled by oil pressure. That valve has to cut off air supply and then bleed the pressure off the unloaders to make the compressor start pumping. If you can find where the air escapes when the valve releases the air, and put an orifice there, you should be able to delay the loading of the compressor. The Quincy hydraulic unloader control valve # 110827 (may not be similar to the one on your compressor) has a 1/4" NPT oil port, and a 1/8" NPT air supply port opposite it. It has a 1/8" NPT outlet to the unloaders on the side. Opposite that is a slanted passage marked "vent" on the drawing. You might be able to epoxy a thin brass tube to the vent, and then attach a needle valve to the brass tube to get the delay you need. If your phase converter takes too long to spin it up, my guess is the VFD won't be able to go a whole lot faster. On the other hand, it could manage a nice acceleration with perfect phase balance, so that the overloads don't trip. (You wouldn't have the overloads conneced, anyway, as the VFD can sense an overload.)
Jon
Reply to
Jon Elson
I haven't seen an airflow-controlled unloader control on a Quincy. Most of the larger ones have a hydraulically-activated air valve. When oil pressure comes up, then the pressurized air that is holding the intake valves open is released.
Jon
Reply to
Jon Elson
Jon, the oil pressure can be only sensed in pressure lubricated compressors, right? Mine is splash lubricated.
I have some strange attachment near the pump where some thin copper lines go, which is separate from the regulator switch. I think that it is the unloader adjustment thingy, but I do not know how to operate it. I can take some pictures.
Re: the drive, I think that a 25 HP rated drive should accelerate the 10 HP motor just fine, not much slower than actual 3 phase power. I will probably know by Sunday.
Indeed I will not have overloads, however, I will probably mount a fused disconnect in before the VFD, as a CYA measure.
i
Reply to
Ignoramus7291
Just for the heck of it, did you check the crankcase oil level? On an old compressor with worn rings can allow a lot of water buildup in the sump, which also whips up the oil into goo, and can hinder the movement of the pistons.
Tony
Reply to
Tony
On Fri, 26 Oct 2007 10:03:33 -0500, with neither quill nor qualm, Ignoramus7291 quickly quoth:
Then you've already determined that it's a motor/timing problem. Is there any adjustment possible on the unloader timing? Orifice change or something? Have you talked directly to the guys at Quincy about it?
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Reply to
Larry Jaques

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