Coolant pump

I have a coolant pump on my lathe but it can't push the coolant up to the outlet! The pump states RPM 2800 but 2000 is the max I get! It's 3 phase and I'm running it through a converter, how do I test it's getting the correct volts, 3 wires on the back of the pump 1 2 3 terminals, and an earth,. Also when the pump is running fluid is coming out the drive shaft see photo, should it do this? I have got it apart but there are no seals around the shaft just a small gap say half a mm, I will put the photos on in a moment as they are on my iPhone .

rob

Hi Rob

sorry to state the most obvious but is the rotation correct. Yes a gap in the housing to shaft is normal to allow the outlet on the discharge to be throttled and release the excess flow back to the tank.

Is the converter variable speed

Eric

Hi Eric, I have tried both rotations with the same effect, the converter has 6 setting the higher the number the more power, I use it on my surface grinder running all 3 motors, if I increase the power say number 3 the pump slows! Almost to a stop, So on number 1 it runs but not at full speed! & the boost light stays on! normally it gos out when the motor it's driving get to full speed.

rob

Hi Eric, I have tried both rotations with the same effect, the converter has 6 setting the higher the number the more power, I use it on my surface grinder running all 3 motors, if I increase the power say number 3 the pump slows! Almost to a stop, So on number 1 it runs but not at full speed! & the boost light stays on! normally it gos out when the motor it's driving get to full speed.

rob

How can you see fluid coming out of the drive shaft? The part in your last photo is the impeller housing which must be submerged in the coolant, there is a spigot on this for the delivery hose. If you are using a converter (not a VFD) you should not run the pump without the main motor, 3rd leg voltage can rise excessively and damage pump windings, minimum load for converter is usually around 1/2 HP. Voltages from converters can be lower than expected but would not affect RPM. Check impeller, check pipe and valve for blockage.

Dave

Rob, as Dave says above, the pump housing must be fully immersed in the fluid being pumped, most run with fluid covering the pump by a good couple of inches.

Most of these pumps (that I've seen) do pour out a fair bit of fluid from the shaft housing when running, this is to prevent cavitation (and the noise that ensues) when the pump outlet is stopped off and also helps to maintain a good mix of coolant fluid.

Edited By Lofty76 on 09/11/2013 22:43:41

I can suck fluid up with my mouth, so I would say no blockage. As for the impeller' like I say its in good condition . Will put it in a bucket and well cover the housing and shaft, see if that helps, but with the motor running 1000rpm lower! Then I can't see things improving.

rob

Rob

Low rpm will cause significant pressure drop due to the square law. Coolant pumps generate low head to start with, so that could be your problem. Have you checked that the pump is turning freely with no tight bearings? Not running at synchronous speed is both strange and rather unhealthy for it. In my experience, excessive loads are the major cause of healthy motors not getting to speed. Worth checking the windings with a meter, and tighten all electrics.

Edited By jonathan heppel on 10/11/2013 08:58:32

Hi Rob,
From the label on the motor it requires about 400 volts between phases. You use the term "converter" so I assume it uses capacitors to produce some phase shift. (Rather than being a true three phase inverter.) I suspect you do not have 400 volts between phases. Measure the voltage between each of the three phases and report back with these readings. Also check the pump turns freely as Jonathan suggests.

Les.

My money's on Les's solution. If you are using an ordinary inverter, the output is 230v 3 phase not 400v.

Andrew M

Yes Les your right about the converter, and will check the voltages tonight, at work now. The motor turns as free as a bird so no holding back there, the converter has a sticker on the out plug 415v but like you say each phase could be adrift! I had an electrician look at it last week and different volts was confusing him he his getting some advice from the maker of the converter and was due to come on Saturday to check it, but my son needed him on the farm and that is priority so may get him back this next week. Al204 his coming over today to get his van service by my other son, he said he would bring over his converter to try it on the pump, so when I get back to night I will be loaded with info for you all, pending the grandchildren not carting me off to do something for them, it's all go.

Rob

The converter Rob is using is a Transwave 3.7KW

It's not clear if you're trying to run the pump by itself or in parallel with a higher power motor. A converter that size most likely needs a pilot motor running simultaneously in order to pull the phases closer to 120° separation rather than the 180°/90° which that type of converter produces. 

Edited By jonathan heppel on 10/11/2013 12:38:40

The motor is 1 hp and should do 2800rpm but will only run between 1800-2000rpm Rob checked this with a taco graph or what ever you call it, while i was on the phone to him last night he checked the rpm on the surface grinder should be 1800 taco said 1820rpm so we think the problem is the motor but not sure, the surface grinder spindle motor is 1.5hp i think so you would think it would run the slurry pump motor with out any problem, the other thing is when the surface grinder motor is up and running the boost on the converter stops, but not when you do the same thing with the slurry motor, i think rob would like to know how to check the motor to see if there is a fault with it.

Alan.

Sorry the surface grinder runs at 2800rpm and is correct.

Al.

Yes Jonathan just running that 1 hp motor on its own, the lathe as it's own inverter.

rob