100HP 480v

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mannyb

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Electrician
I posted yesterday about a 100HP 3phase 460v motor for water pump. This is a separate question to same problem. I have a customer that has a wash plant for washing sand. The water is feed from a lake that feeds into a reserve tank. The reserve tank feeds wash plant. My question is can a VFD be used to slow the flow of water going into wash plant with a VFD that could slow or turn off water going into wash plant. The is a simple wash plant so its not complicated system. The problem is that the tank drops couple feet at start up.I dont have much experience with drives but I am trying to figure it this is customer solution.
 
This could get complicated and we need to understand the problem better.

You have two basic things at odds. The need to supply a certain amount of water to "wash the sand" and the ability of the reserve tank to hold enough water to meet those needs.

IMHO the VFD should be tasked with (only) supplying enough water to wash the sand. Something else, probably hydraulic/mechanical in nature, should be tasked with maintaining water level in the reserve tank. If and only if, that control system can't maintain water levels, should it be impacting VFD operation.

I suspect a PLC and some transducers will be needed along with some level of programming. It could get easier if you tell me we can just stop washing sand until reserve tank refills.
 
It's tough to know what's right without seeing the operation.

To answer your question, yes, it may be possible to use a transducer with a VFD and PID loop to maintain a constant level but I'm not sure if a VFD is necessary here with so little info to go on.
 
Yes, a vfd can be set up to control pressure, flow, or level or a combination of those. Need more information to give you a more intelligent answer than thst.
 
mannyb said:
I posted yesterday about a 100HP 3phase 460v motor for water pump. This is a separate question to same problem. I have a customer that has a wash plant for washing sand. The water is feed from a lake that feeds into a reserve tank. The reserve tank feeds wash plant. My question is can a VFD be used to slow the flow of water going into wash plant with a VFD that could slow or turn off water going into wash plant. The is a simple wash plant so its not complicated system. The problem is that the tank drops couple feet at start up.I dont have much experience with drives but I am trying to figure it this is customer solution.
Click to expand...

What do you want to achieve?
Yes, a VFD could slow/control the flow. Do you need to do that on a continuous basis or just at start up? If just the latter, a controlled valve might be a simpler and cheaper solution.
 
Besoeker said:
What do you want to achieve?
Yes, a VFD could slow/control the flow. Do you need to do that on a continuous basis or just at start up? If just the latter, a controlled valve might be a simpler and cheaper solution.
Click to expand...

Thanks for response. The wash plant needs a certain flow of water to operate so yes it needs to be continuous. The 100hp gives them that but because its so fast the wash plant water start to over flow because the pump sits about 100' away. They need to be able to turn on pump and manage the flow before it reaches wash plant. I didnt think about the control valve until you mentioned it. Thanks for another idea. Or i need a way to control both the pump to wash plant and second pump at same time.
 
mannyb said:
Thanks for response. The wash plant needs a certain flow of water to operate so yes it needs to be continuous. The 100hp gives them that but because its so fast the wash plant water start to over flow because the pump sits about 100' away. They need to be able to turn on pump and manage the flow before it reaches wash plant. I didnt think about the control valve until you mentioned it. Thanks for another idea. Or i need a way to control both the pump to wash plant and second pump at same time.
Click to expand...

As it is a continuous process, a variable speed drive would be the way to go to avoid wasting energy. You may need a flow transducer so that the flow can be regulated automatically
 
How is a decision made as to the water flow rate feeding to wash plant now? If there is no flow adjustment now, what would be the criteria for making that decision? Are you looking for something automated, or are you thinking of having a person decide on the flow rate?

In wash plants that I have done, the flow rate of the wash water is somewhat dependent on the flow rate of material into the screen (the ones I have done all involved vibratory screen separators). If you want to automate the decision on water flow rate, you will first need to be able to measure flow rate of product into the system, which typically involves a "belt weigh" transducer system on the in-feed conveyor. These are not inexpensive and require a level of maintenance expertise that might be untenable for many unsophisticated users. The simpler (yet less accurate) way of doing this is to have an operator with a potentiometer observing the wash plant and deciding on how much water is needed, making manual adjustments either to the pump speed or a proportional throttling valve. In 99% of those that I have observed, the operator gets lazy and just runs it at full flow no matter what, making it all completely pointless...
 
Explain more about this reserve tank. From what you explained the water pump is 100’ away from the reserve tank. Is this correct or is the reserve tank 100’ away from the wash plant and the 100 hp motor is pumping out of the reserve tank into the wash plant?


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