[Ed from NY]

Hi, I have a Graymills IMV-100 1HP (50 GPM) coolant pump. I can run it full blast by just wiring it 3-phase and control on/off with a relay -- that would be fine, but... I was wondering if there is a cheap way to control the flow rate with dial of sorts.

Thanks!

[awemawson]

You need an appropriately rated three phase in three phase out inverter wired to a twiddle pot. OR it may be possible to choke the pump flow with a suitable gate valve.

[mactec54]

Ed from NY

Not that cheap but quite easy, because you have a 3phase motor, you can use a VFD drive to control the motor speed

[Geof]

If it is a centrifugal pump controlling the flow rate by controlling the motor speed is sometimes not so effective because the pressure drops off rapidly as the speed is reduced.

But if it is centrifugal it is more or less impossible to overload by choking the flow so just use a valve. To be picky it should not be a gate valve because these are intended to be fully closed or fully open, similar to ball valves. Use the other type, a poppet (?) valve. Or a big needle valve.

[Bubba]

IIRC, that is a centrifugal pump. Therefore, the flow is proportional to the rpm, the head (pressure) is proportional to the rpm(squared), and the power requirement proportional to the rpm (cubed). Yes, you can also choke it down with a valve on the discharge, but you do not want to run against a dead head (zero flow) for an extended period of time as this will cause heating in the pump.
A VFD is the way to go and is also what they are doing in a lot of industrial situations now.

[Ed from NY]

Hmmm it sounds like it would be something like this

GS1-21P0 Products

A bit on the expensive side, but it does have a knob and it ia 1hp. Sigh! I was hoping to grab a dimmer at homedepot :lol: -- well not really

[Geof]

A VFD controlling a coolant pump seems a bit of overkill to me. Get a cheap valve and just throttle the flow with this. Coolant pumps operate with the pump fully immersed so you are never going to overheat anything running the pump with the flow completely blocked.

[UUU]

Fit a branch in the flow pipe and route one side through a valve back to the tank. When you open the valve nearly all the flow goes straight back to the tank. As you close the valve more of the flow goes to the work. But the pump is always running at full flow, so there's no overheating issue.

[underthetire]

A VFD controlling a coolant pump seems a bit of overkill to me. Get a cheap valve and just throttle the flow with this. Coolant pumps operate with the pump fully immersed so you are never going to overheat anything running the pump with the flow completely blocked.

Never seen a 3phase pump "fully" immersed. Just the fountain type pumps. The VFd is a nice way to go, and that unit is super cheap Ed posted. Gate valves work, to a point. If you get them closed too much, the pumps will start cavitation and make a lot of noise and vibration, and can cause heat in the coolant. Hell, a 3 phase 1HP rated contactor is 80-90 bucks alone, not much more to go to the VFD.

[Geof]

The pump is fully immersed, the motor sits above the tank.

[Ed from NY]

I was planing to hook it up today but did not get to it -- need to run a bit of wiring and change to a larger coolant tank. We will see how much splashing we get. The one thing with the gate valve is that, as I have it set up now, I have to open the door in order to adjust it, which depending on the flow and where the splashing is going means waiting till the cycle is complete... I could change the plumbing, but then... well, we will see.

[Ed from NY]

I hooked it up today and the pump at full throttle is just what the doctor ordered. No need to reduce the flow, though you do need to turn it off before opening the door... or else

[Graymills Craig]

Hi, I have a Graymills IMV-100 1HP (50 GPM) coolant pump. I can run it full blast by just wiring it 3-phase and control on/off with a relay -- that would be fine, but... I was wondering if there is a cheap way to control the flow rate with dial of sorts.

Thanks!

Hi, Ed.

While an inverter can control the pump, the motor is not inverter duty. You risk damaging it if you run it too slow.

Can I ask what you're trying to control? With most single-stage centrifugal pumps, you can cheaply control output with a valve.

I'm happy to answer any questions you'd have.

Cheers;
Craig Shields, President
[email protected]

[Graymills Craig]

A VFD controlling a coolant pump seems a bit of overkill to me. Get a cheap valve and just throttle the flow with this. Coolant pumps operate with the pump fully immersed so you are never going to overheat anything running the pump with the flow completely blocked.

I'd agree with this post. Deadheading shouldn't be a problem with the IMV series.

[Ed from NY]

Hi, Ed.

While an inverter can control the pump, the motor is not inverter duty. You risk damaging it if you run it too slow.

Can I ask what you're trying to control? With most single-stage centrifugal pumps, you can cheaply control output with a valve.

I'm happy to answer any questions you'd have.

Cheers;
Craig Shields, President
[email protected]

Hi Craig,

Thanks a lot for the advice. I'm now running it on full and I intend to continue to do so. Love the amount of coolant it puts out!!!

The one unexpected issue has been that the mesh and traps I used to separate the shavings cannot cope with the amount of flow the pump puts out. This is because I use Mobilmet 426 as coolant. I should really switch to 423, but that is a different story. The combination of higher GPM and high viscosity carries the chips further and the oil itself does not pass through the mesh very quickly. So I'm having to adjust a few things to accommodate the increased flow.

[awemawson]

Thinking about it, a bypass valve dumping coolant back to the tank is the easiest way to go. That way the pump runs at it's full capacity, but the delivery pressure is fully adjustable. Inexpensive too only needing a valve and a bit of tubing you can place the valve whereever you want it.

[Graymills Craig]

Thinking about it, a bypass valve dumping coolant back to the tank is the easiest way to go. That way the pump runs at it's full capacity, but the delivery pressure is fully adjustable. Inexpensive too only needing a valve and a bit of tubing you can place the valve whereever you want it.

It's not a bad idea, so long as the increased agitation doesn't cause foaming. You can do a few things to minimize this, such as ensure that the return is below liquid level, and shoot it down the long dimension of your tank; hitting a corner with any force will cause foaming and spills. You can also try an eductor (eductor - Google Search), which will give you lower pressure.

We've done similar systems for our ink pumps (we actually sell an entire kit for this) with pretty good success.

Another idea is to use (strength depending on the pressure of your pump, natch) a flexible tube with a pinch valve and no bypass.

[Graymills Craig]

Hi Craig,

Thanks a lot for the advice. I'm now running it on full and I intend to continue to do so. Love the amount of coolant it puts out!!!

The one unexpected issue has been that the mesh and traps I used to separate the shavings cannot cope with the amount of flow the pump puts out. This is because I use Mobilmet 426 as coolant. I should really switch to 423, but that is a different story. The combination of higher GPM and high viscosity carries the chips further and the oil itself does not pass through the mesh very quickly. So I'm having to adjust a few things to accommodate the increased flow.

If you want to send me pictures, I can run it by our guys to see if we can suggest anything.

[Ed from NY]

I think I solved it by upgrading the mesh to a bit over 3 sqft and adding a shield so that the chips fall further away from the collection area

Graig, I sent you a PM in an somewhat unrelated matter.

Love the pump! The flow it puts out ROCKS