Can I use a VFD on a single phase pump? 1

[freeland90]

Hello,
I'd like a way to control the flow of this pump

https://www.piusi.com/products/panther-ac.

I read that VFD only works on the three-phase pumps, this model is available in 3 phases but it's utterly expensive. Wonder if there's a way to control a single phase?

 

[LittleInch]

You can, but for such small pumps why don't you just throttle the output with a decent globe valve or similar?

The losses in the VFD can be big and I don't understand what your benefits are.

But of course you can do it. A simple google found this e.g.

http://www.vfds.org/single-phase-vfd-with-220v-input-output-924125.html

https://www.amazon.co.uk/Variable-Frequency-Inverter-Converter-Dissipation/dp/B07WBVTVYL

But your motor needs to be suitable for this and I doubt it is.

Check out this

https://www.maderelectricinc.com/bl...e-frequency-drive-vfd-on-a-single-phase-motor

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[freeland90]

Hey Inchy! Thank you for your valuable input as usual. I'll be running this pump 24/7/365 and my problem is power consumption. Using a globe valve will achieve the flow I desire but with the same power consumption which is a waste. My only purpose for using a VFD is to decrease power consumption of the pump and increase its flow whenever I feel needed.

 

[1503-44]

It is the flow rate that demands the power, not the valve. In other words, reducing the flow by any means, by vfd or by valve, reduces power consumption. You can't just think vfd will be better and make it so. You have to run the numbers for vfd and valve and find out which will be cheaper. If you have to buy a motor suited for vfd use, your economics may not look so good either. A valve also reduces or increases flow.

A black swan to a turkey is a white swan to the butcher ... and to Boeing.

 

[freeland90]

Thanks. You really are the real deal. Ball-valve it is then!

 

[LittleInch]

freeland90,
" Using a globe valve will achieve the flow I desire but with the same power consumption which is a waste"
A common misconception as my friend mr 44 says.

Power of a fixed speed centrifugal pump is directly proportional to flow once you're in the reasonable efficiency zone.
Also changing speed changes the head by the speed difference squared. If you need a near constant head then VFD is not for you.
You always need to match the pump to the downstream system to see what is best. You've told us nothing about the d/s system.

However this is a vane pump. So more like a PD pump and hence why is comes equipped with a bypass valve to essentially do the same thing.

So something completely different. They are good for near constant flowrate at a variety of pressures, hence the flat nature of the curve listed. Then I tend to agree, the energy involved in sending some product back to the inlet is probably wasted.

So why a vane pump?

Also VFDs need special single phase motors and they also use about 8 -10% of the rated power in heat so make sure wherever the VFD unit is that it's somewhere free venting and include those losses in any power / cost calculation.

Oh and don't use a ball valve to throttle flow - doesn't work.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[freeland90]

Hey Inchy. You're right, I should have been more detailed. The pump is needed for a circulation cooling system using a diesel-like property of a fluid.

Basically, it'll be circulalting a 3,000Watts worth of hot liquid through a radiator and then back to a tank. To answer your question, why this pump? Well, there're two reasons; the first: the liquid I'm using (close property to diesel) needs a Viton-sealed pump and this one is. The 2nd reason is the constant flow. This system will be running 24/7/365.

I wish I knew what a vane pump is to give more details. When you said don't use a ball valve to throttle, I assume you meant that a globe valve is a better option?

This pump may be a good option or bad for this project. your opinion will definitely shape my final decision on whether I should get one of these Panthers.

 

[LittleInch]

A vane pump - look them up on google - are basically a form of PD pump, i.e. for every rotation of the pump a certain pretty fixed amount of liquid goes through it. The pressure out of the pump varies with the flow resistance and essentially floats from about 0.25 bar to about 2 bar.

So long as you want to flow at a constant rate of either about 55l/min, 70 or 90 l.min (at 50 htz) then it's all good. Just choose your model, pipe it in and turn it on and do nothing with it other than screw the bypass valve closed. If you're in 60htz land then you have different flowrates - see the table.
Your power consumption will depend on what pump outlet pressure you need. So long as its less than 2 bar then you won't use all the rated motor power.

Any other flow less than those figures then open up the bypass a bit and so long as you are within 10-15% your power losses are quite small.

DO NOT throttle the out put of this pump as it doesn't like it. The pressure will rise until it either breaks or the internal pressure relief system kicks in and sends some fluid back to the inlet - if it has one.

It does look a bit excessive for what you need, but if it fits the bill in other ways then looks ok.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[1503-44]

Great. Do exactly as "Inchy" says.

A black swan to a turkey is a white swan to the butcher ... and to Boeing.

 

[freeland90]

Alright, Thank you! If you think it's expensive. Can you recommend a pump that is designed for Diesel and is Viton-sealed, Regardless of flow rate? I only came across this PIUSI and March pumps. All other pumps seem to use EPDM or Nitrile rubbers, both rupture when exposed to hot Diesel.

Another question, If I may. What makes you say one pump can be throttled and one that cannot?

 

[1503-44]

Somebody here will know, but they're going to ask ...
How hot is it?

A black swan to a turkey is a white swan to the butcher ... and to Boeing.

 

[LittleInch]

I don't normally get involved in small pumps so if you want a specific seal then go ahead.

Or if you want to get fancy look at mag drive seal less pumps...

PD or positive displacement pumps like vanes pumps, screw pumps, piston pumps etc, like their name suggests, pump a fixed displacement at every rotation. If you try to throttle one of these, the pump still tries to pump the same displacement. Putting a restriction of flow after it simply raises the pressure until either the motor stalls, overheats and starts smoking or the pipe or flange breaks and spurts hot diesel type fluid all over your plant, catches fire and burns your facility down or some pressure relief valve opens somewhere and all the excess fluid goes somewhere, hopefully back to the tank or pump inlet, thus wasting energy.

Centrifugal pumps on the other hand essentially generate a fixed pressure over a wide flow range. So all that happens when you throttle is is that it goes left on its pump curve, maintains more or less the same outlet pressure ( within 10-20%) and so long as some flow (about 30% of the max flow) is still going through the pump all is good. Power is reduced, there is little to no losses and this is a common use of this type of pump.

Does that make sense?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[freeland90]

I see! Makes a lot of sense now. PD = fixed flow and pressure, Centrifugal = fixed pressure but variable flow. It makes alot of sense because when I asked for advice from a colleague who's doing the same project, he actually recommended a Centrifugal pump. I ignored his recommendation, but now that you explained it. I think it's the one for the job!

Thank you!

 

[LittleInch]

PD is fixed flow and variable pressure (up to some limit)...

"Fixed" is really within 10-20% here for both flow from a PD or pressure from a centrifugal, But I think you get the general idea.

I don't know how long your vane pump would last either as there are some continuous sliding components there and a cheapish pump might not last 365 days....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[freeland90]

Thanks for the tip.
Forty, the liquid is 50C.

 

[Compositepro]

A common practice with small liquid cooling loops is to use a small vertical centrifugal pump immersed in the fluid reservoir. The motor is mounted on top of the tank and a long shaft couples to the pump. There is no shaft seal. This is about as inexpensive and robust as one can get.

Just search for machine tool coolant pumps. You can get them from eBay or Amazon, too.

 

[LittleInch]

Or a submersible pump?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

Diesel at beyond 55-60degC or so typically requires a hazardous area classification electric motor.

 

[crshears]

Here'a a real-life anecdote regarding the throttling of centrifugal pumps:

Back in the day we used submerged-impeller centrifugal pumps to dewater the pits in the condenser circulating screen houses. The normal duty of these pumps was standby duty to supply open [raw] service water to the coal-fired generating plant, for use when their associated coal-fired generating units were shut down. As a result they usually ran at a discharge pressure of ~ 35 #, nicely within in their design operating envelope.

There was normally no issue with starting these up with the discharge valve wide open, as there was usually enough pressure already present in the system that there was only a brief higher current draw during pump spool-up.

When used for dewatering, however, their normal discharge valve to the plant service water was shut and a lateral discharge valve back into the inlet channel was cracked open only slightly before the pump was started, since at the beginning of the dewatering process there would be essentially zero head applied to the pump [stoplogs had all been installed in the gains, but the water level in the screen pit was still the same as the inlet channel level] and the pump would otherwise trip on overload. Once it was up to speed, the lateral discharge valve was slowly opened further until the pump motor got to rated current; as dewatering proceeded and the head across the pump steadily increased, the current draw would decrease, and the lateral discharge valve was therefore opened still further so as to maintain no more than rated maximum current draw while expediting the dewatering process.

Hope this helps.



CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[freeland90]

Compositepro : Thank you! I've seen it before but didn't know what's called. The Graymills one looks appealing to me! I like the idea of a submersible pump (like Alpine PAL3100) but they don't say if they're meant to run 24/7.
Thanks for the throttling experince!