vfd booster pump control
vfd booster pump control
(OP)
WE have a problem with water pressure at our plant.The pressure ranges from 70psi to 40psi and often there is a significant enough change in pressure to shake the water lines.The booster pump we have is driven by constant speed motor at 1750rpm which we would like to be able to control the speed and try to maintain a smoother water pressure.We
have installed a vfd(Yaskawa G515) and inverter duty motor for the booster pump.The way we are controlling the vfd is by a pressure transmitter(4-20ma)signal insalled on water line, to a honeywell controller(udc2500) and have the honeywell control the vfd and tune the PID on the controller so there is the correct response.Do you guy's think this will work and if you have any suggestions I would appreciate the advise.
have installed a vfd(Yaskawa G515) and inverter duty motor for the booster pump.The way we are controlling the vfd is by a pressure transmitter(4-20ma)signal insalled on water line, to a honeywell controller(udc2500) and have the honeywell control the vfd and tune the PID on the controller so there is the correct response.Do you guy's think this will work and if you have any suggestions I would appreciate the advise.





RE: vfd booster pump control
Some VFDs have the PID control function built-in, I would have thought the Yaskawa was among them. But no matter, I actually favor doing it the way you did because if anything goes wrong with the VFD, the loop controller stays behind and is already set up to control another VFD, of any make, model etc, that you could get in a hurry.
RE: vfd booster pump control
RE: vfd booster pump control
RE: vfd booster pump control
What you need is what we electrical engineers use a to eliminate or control sudden voltage fluctuations - a capacitor! In your water realm this would be a bladder tank. Every domestic well typically has one. It is a tank with a rubber bladder stretched across the middle. The bladder has about 8psi on one side. The other side is directly hooked to your water system. The water will fill the tank almost full which compresses the air on the other side to the water pressure.
In a well system this will greatly reduce the pump from thrashing as it allows the pump to fill the bladder tank while storing energy. Once the system pressure reaches cut-off the pump is stopped and the user can continue to use water for quite a while until the energy stored in the compressed air diminishes to a fraction of the charged state.
In your case this would represent extra water capacity that could be distributed throughout your facility. I'd put them near any large use point that has a cyclic nature. You would also want to put them at the end of long runs away from your source. This would allow small runs of pipes or runs that have become too small over time, to continue to service large sudden demands. This prevents the water velocities in the long pipe runs from having to skyrocket to meet a sudden demand, not being able to accelerate the water, resulting in banging and pressure drops.
Most large plant air distribution systems use this same method with Accumulators spread around to greatly reduce air pressure spikes and variations.
Since you've already installed the VFD, fear not, as your VFD would work exceptionally well with this distributed storage. It would also have something to work with rather like the aforementioned domestic pump, working with the storage to keep the pressure up, and steady. I don't believe you will have any real success without distributed storage.
Bladder tanks come in all sizes from about 1/2 a gallon to hundreds of gallons.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: vfd booster pump control
RE: vfd booster pump control
Example: A large demand is made near a distant storage tank. The demand is a step function like a valve opened to fill a product mixing tank. The otherwise sudden drop that would occur is covered by the storage tank but the flow continues and the pressure would drop as related to how big the demand is verses the tank's sizing. Meanwhile the VFD/pump has time to bring the pressure back to the desired level and the new open-valve flow, coming in smoothly to the target.
Here's the first link I hit on Bladder Tanks, also called diaphragm tanks.
http://www.watertanks.com/category/48/
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: vfd booster pump control
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RE: vfd booster pump control
The sudden transients are a separate issue and the accumulator tanks sound like a good idea to correct that.
Actually, as already mentioned, the combination of accumulators and VFD pressure control make for premium performance and would be highly recommended for the situation described.
RE: vfd booster pump control
RE: vfd booster pump control
RE: vfd booster pump control
RE: vfd booster pump control
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: vfd booster pump control
RE: vfd booster pump control
And, of course, if the pump hp and motor hp match at motor base speed, overspeed isn't possible but that is a rare case. Almost always, the motor is oversized for the pump so you can take advantage of that.
RE: vfd booster pump control
So, unless you oversized the motor even more than it needed to be derated to run on the drive, then you cannot increase the speed above nominal.
If he needs the same flow rate at 70 PSI that he is now getting at 40 PSI, he will need to almost double the size of the pump and motor. The pressure will increase by the square of the speed but, the flow will only increase in exact proportion to the speed. So I don't think he would be able to speed up the pump enough to get this done.
Therefore, a bigger pump is needed to maintain 70 PSI. Then you need to vary the flow rate with a valve or a drive to lower the flow when needed and still maintain 70 PSI.
RE: vfd booster pump control
You probably need the pressure tank for 2 reasons. #1 is to absorb the surges in the water system. #2 is to provide extra water capacity during the high flow demands. So, you need pressure tank(s) large enough to source the water and maintain the pressure during the high flow demand periods.
Of course, if the pressure of the water is not that important then you could attempt to maintain something like 40psi or 70psi (or some value in between) and just let the pressure fall when the demand is high.
Is it possible to slow down the operation of the water valves in the system? The water hammer sounds like you have electric solenoid valves that are slamming shut very fast. I doubt you can slow them down but it's worth at least a quick look. The valves switching the water on and off are the source of the problem so look there first.
RE: vfd booster pump control
I don't recall the original poster saying he needs 70psi. If less is acceptable, the drive/motor/pump might just barely be big enough.
You are correct about the pump hp increasing rapidly with overspeed. My post says "the small amount of overspeed" just for that reason.
My whole point is that the OP has the existing equipment but isn't using all of it. Why not use it to the max and see if that's enough. If not, its time to buy something, maybe even the valves you are so in favor of!
RE: vfd booster pump control
Forget the pump for now, it won't affect water hammer that much except to possibly make it worse.
At each point that the flow is suddenly reduced (usually a valve closing) install a surge suppressor such as itsmoked recommended. It is plumbed in ahead of the valve so as to provide a cushion for the moving column of water (the moving water in the pipe supplying the valve).
If you have pipes banging at 40 PSI, you may well have pipes breaking if you are able to maintain 70 PSI.
Sorry but pipes banging when the flow is stopped is the wrong problem for the solution of installing a VFD.
If the varying pressure is causing other problems in your plant then the VFD will probably correct those problems but it will do nothing for water hammer and will very possibly make the water hammer worse.
respectfully
RE: vfd booster pump control
RE: vfd booster pump control
http://www.cla-val.com/pdfs/B-59.pdf
RE: vfd booster pump control
Also DickDV, here is an example of why most motors running on VFD should be derated. A customer has a 100 HP turbine pump. Service factor amps are 137. When running across the line the full load is only 124 amps as the incoming voltage is 485. When running on the drive the voltage to the motor is only 462. This makes the full load amps 138. The drive manufacturer upsized the drive with no different effect. The drive manufacturer finally said that was the best they could do, and if the owner did not want then motor running in the service factor, he need to derate the motor by installing a 125 HP.
RE: vfd booster pump control
462 volts at 60 Hz. = 7.7 volts/Hz.
Did you try configuring the VFD for motor voltage = 485?
respectfully
RE: vfd booster pump control
We could trim the pump but, we need the maximum performance. The pump will do what we want when running across the line. Just heats up the motor and trips out when running on the drive.
RE: vfd booster pump control
Second, you didn't say what the motor nameplate voltage is. I know that pump motors are a world of their own but, if the nameplate is 460V, you should be able to get the full load out with only nameplate amps. If not, the nameplate values are not trustworthy. On the other hand, if the motor is nameplated 485V as you seem to imply, you have an odd bird indeed, not at all typical of normal duty motors.
Third, if you are sizing the motor based on service factor amps rather than full load amps as is so often done in the pump world, then the drive will not be sized correctly if based on hp. In fact, as a general rule, drives should be sized on amps, not hp. Whoever sized the drive as you describe, simply doesn't know enough about the drive/motor world to do the sizing based on, first, continuous amps, and then, short-term overload amps.
As for sizing the motor, in pretty much any application including pumps, sizing motors based on hp is a high-risk venture too. Motors should be sized on continuous amps and then, short-term peak amps. As in drives, you take the short cut and you pay the price. Experience will teach you a better way if your eyes are open and your mind is receptive to new knowledge.
RE: vfd booster pump control
It's a 480 volt motor and Square D sized and resized the drive, and it's still running above the service factor. If you can tell me how to program the drive to output higher or at least as high as the incoming voltage, I would greatly appreciate it. I can pass it on to the manufacturer and then maybe we can get the amperage below the service factor.
RE: vfd booster pump control
You mention a motor-lead reactor but I'll bet there's a drive input reactor built into the drive as well.
You should contact the major reactor manufacturers for better solutions to both the input harmonics suppression and the motor lead filtering. There are other technologies out there that do at least as good a job with less voltage drop. You may also find that raising the carrier frequency on the drive output will permit a lower loss filter design as well.
Major manufacturers are TCI (Transcoil Inc.) and MTE (Milwaukee Transformer and Engineering). Both are located in the Milwaukee WI area and have websites.
Good luck finding a solution.