Author Topic: WVO Centrifuge Design - thoughs ?  (Read 467 times)

veggie

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Re: WVO Centrifuge Design - thoughs ?
« Reply #15 on: July 07, 2018, 05:27:31 PM »
UPDATE:

The project is slowly moving along.
I am now in the process of adding the circulation pump and interconnecting tubing.

« Last Edit: July 07, 2018, 06:44:12 PM by veggie »
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veggie

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Re: WVO Centrifuge Design - thoughs ?
« Reply #16 on: July 07, 2018, 05:29:27 PM »
Inline oil heater made from a pipe with threaded connections welded in place.
1000 watt , 120 volt element.
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veggie

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Re: WVO Centrifuge Design - thoughs ?
« Reply #17 on: July 07, 2018, 05:41:35 PM »
PROBLEM !

I am using a small 12 volt gear pump to move the oil around.
It runs fine when connected directly to 12 volts, but my plan was to drive it with a 12 volt PWM motor speed controller so that I can finely control the flow rate of the oil through the centrifuge.
When I tested the PWM controller on this 12 volt pump, the pump ran at a fixed speed regardless of where I dialed the Pot on the PWM controller. After 15 seconds there was a lot of "Magic Smoke" coming out of the PWM controller. GAME OVER  :'(

(The PWM controller cost me $17 so it's not a big loss)

My question to the group is...
Any idea why this controller would run my 12VDC fertilizer sprayer pump at various speeds but then cook itself when trying to drive this 12 VDC gear pump. Both pumps use 4 amps and the PWM modulator is rated higher than that.

Could it be Brusless vs. Brush type ?
I would really like to be able to vary the speed on this Gear pump.
Any ideas?

Here is the pump... (not the same seller as I used but still the same pump)
https://www.ebay.ca/itm/12V-Scavenge-Gear-Pump-Diesel-Fuel-Scavenge-Oil-Transfer-US-FAST-SHIP-Black-Pump/151707363632?epid=1441247850&hash=item235276a930:g:mX4AAOSwIeFbMwqt

Here's the pump...
« Last Edit: July 07, 2018, 05:43:16 PM by veggie »
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AdeV

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Re: WVO Centrifuge Design - thoughs ?
« Reply #18 on: July 07, 2018, 06:36:34 PM »
Possibly the pump ended up drawing a much larger than rated current. I've got a similar pump, when I tried loading it up through a spray head, it shot over it's 4amp rating, I think it peaked at about 9 amps.

I'm not sure why those gear pumps are so much more expensive than similarly rated diaphragm pumps. In my experiments, the latter never went over their rated ampage,  and produced a far superior pressure. They're also capable of holding back mains pressure water, which simply sluices through a gear pump like it wasn't there...

(I know: Why bother with a pump when you've got mains water, right? Metering... and solenoid or motorised valves are far too slow acting when faced with a bar or so of mains water... stop the pump, the flow stops instantly).
Cheers!
Ade.
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veggie

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Re: WVO Centrifuge Design - thoughs ?
« Reply #19 on: July 07, 2018, 06:43:11 PM »
Hi AdeV

When I tested the gear pump on the PWM controller it was not pumping liquid.
Just free wheeling and probably pulling only 1 amp.
Not sure why it would cook a controller. (Yes, I double checked the polarities  ;)  )

Veggie
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BruceM

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Re: WVO Centrifuge Design - thoughs ?
« Reply #20 on: July 07, 2018, 07:08:12 PM »
It seems unlikely to be a brushless 12 motor with integrated controller; they are more expensive at present.

I suspect that instead, you have an EMC problem with the cheap PWM controller and a nasty brushed motor, emi-wise. EMI from the motor is glitching the MOFET gate or gate controlling circuitry, thus you see full speed until failure.  Capacitors at the motor, and a common mode choke might solve it fairly cheaply. A better designed PWM controller might be able to handle it. If your 12V supply is also full of EMI, that should also be addressed via passive filtering since the controller may not handle that well either.

MOSFETs have amazingly low "on" resistance so can handle a huge load in a single small package.  They do have some serious issues with EMI; their gates are voltage controlled and are much more susceptable to glitching than older bipolar transistors which are current controlled. 

The solution to avoid glitching is suppression at the source (motor), but also to use a very low resistance gate drive (1-10 ohm). Many cheap electronics will not in order to save cost.

Solving the problem at the source is a cost effective solution as it prevents the same EMI from damaging or cause intermittent faults of other connected electronics.  For a "junk box" filter for this motor, I'd start with 0.0-1 uF ceramic, and 10-100 uF electrolytic, and a 3+ mH common mode choke rated for your max current or better. 
 
« Last Edit: July 07, 2018, 07:09:46 PM by BruceM »

glort

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Re: WVO Centrifuge Design - thoughs ?
« Reply #21 on: July 08, 2018, 12:43:14 AM »

.... And when all the oil is cleaned, you are going to rent the thing out to movie producers as a prop for the new Dr. Who movie they are Making Right?   :laugh:

As for the pump, those things had a poor reputation with pumping Veg oil here at least.  Always under performing in longevity or output.  I also see something that would put me off using them in this application if I were ever inclined.....
Designed for intermittent use only. Duty cycle: 30 mins

I would be using a mains powered AC motor/ pump for sure.  Even just the little chinese QB type pumps would be far better than one of these IHMO.  Mate used them on his Bio making setup and we ran hundreds of hours on them with no problem. You need 240 for the heater so may as well run the pump off the mains as well.

What power supply were you running the PWM/ motor off? Was it a battery or some sort of Plug pack/ Ac to DC converter?  If it was a converter, maybe the output was just too Dirty and that's what upset the PWM?

I would really encourage the use of a heavier duty mains powered pump./ You can get PWM's for those as well.  I have had one regulating my 3.6 KW Hot water heater  for months and not had a problem with it yet.

https://www.ebay.ca/itm/Hanchen-Instrument-Electric-Clean-Water-PUMP-110v-220v-QB-60/382512186313?hash=item590f80c3c9:g:qeIAAOSwESNZ92tZ

veggie

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Re: WVO Centrifuge Design - thoughs ?
« Reply #22 on: July 08, 2018, 12:52:51 AM »
BruceM

Thanks for that detailed explanation of the potential problem at hand.
The power source is a 12 volt deep cycle battery. Clean power.
I suspect poor Chinese electronics (again). In any case, it's dead. I won't be buy another anytime soon.
What do you think about using a Rheostat with an adequate amperage rating.?
Just vary the voltage instead of PWM.

Veggie
« Last Edit: July 08, 2018, 01:05:30 AM by veggie »
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veggie

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Re: WVO Centrifuge Design - thoughs ?
« Reply #23 on: July 08, 2018, 01:04:49 AM »
Hi Glort,

Ha...Ha. Yes Dr. Who was inquiring. It's a Tardis machine. It actually holds 3000 liters of WVO but it looks very tiny.  ;D

I have one of those pumps that you mentioned (330 gallons per hour). I use it on my BioD processor for circulation, but for this application the feed to the centrifuge is only 10 gallons per hour. Just a trickle.
That's why I was hoping to slow down the gear pump a bit.

I will dig around more to see if I can come up with a better pump running off mains power.
The centrifuge and pump will have to run for 3 hours per batch so I need a small pump that can handle that duty time.

Perhaps for the time being I can run this gear pump at normal speed with a bypass valve in the discharge line which can slip some of the flow back to the tank. I could adjust the bypass valve position until I get the desired flow rate into the Fuge.
The WVO is open circulation from the tank to the Fuge (no pressure) so maybe the pump will last a bit longer without pressure/amperage stresses.

cheers
« Last Edit: July 08, 2018, 01:08:38 AM by veggie »
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BruceM

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Re: WVO Centrifuge Design - thoughs ?
« Reply #24 on: July 08, 2018, 02:14:44 AM »
If adding a filter is too much for you, then yes,  a power resistor to drop the voltage could be used.  Let ohm's law be your guide for value and watt rating. 


glort

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Re: WVO Centrifuge Design - thoughs ?
« Reply #25 on: July 08, 2018, 03:00:28 AM »
It's a very good looking and beautifully presented machine that's for sure.
I don't think I have ever painted anything I have done like that.  I have always been of the opinion if it worked that was good enough. I am trying to come around though and make things look more presentable. I don't know why I never have taken more pride in what I have done before.
Messy mind, messy machinery I guess.  :embarassed:


The WVO is open circulation from the tank to the Fuge (no pressure) so maybe the pump will last a bit longer without pressure/amperage stresses.


I think that has a lot to do with Duty Cycle. The more under stressed a motor is the longer the heat build up takes and may dissipate it  completely.
Running a resistor should work, my favorite for 12V is just light bulbs. Limiting the current below the motors rating will also mean it can run at lower volts without having heat build up due to higher Current.

I use the 24V electric scooter motors on a modified Chev Small block oil pump for oil collection.  If I run the thing at 24V it will heat up after about 4-500L.  The thing still pushes about 70% flow at half voltage.  If I run it of 12V I can get 1000L through it and it's still fine.

If this were a centrifugal pump you could just limit the inlet and it will reduce the motor load as well. being a gear pump and positive displacement, any limitation would make the motor labor significantly.  My Chev gear pump will stall a 3HP petrol motor of you block it OR simply burst a hose or connection.
I tweaked the pump right up internally with clearances so it does max flow and pressure.  The by pass is also blocked so it only be reduced in output by slowing the drive speed. Yours will be much the same even as is and not possible to slow flow rate only the drive.

Bulbs are good resistors as you also get an indication of the current flow and you can parallel or series them or switch them in and out for different speeds and they never over heat.

The thing with these 12V motors is they tend to run plain bearing and brushes are are just not good logging up decent run hours. AC motors generally have ball races and can run 24/7 for years at a time.  A low voltage motor capeable of the same endurance will cost more than an AC motor would anyway.

What temp are you going to run your oil at?  I used to run mine in my processor up to 80C to speed up the drying process.  I limited it to that as I was worried about heat going back to the motor but mainly the softening of the hoses I was using and the filter being rated to much less than that.  never had a problem with it though. I used a veg oil burner so I was able to heat it fast. Once up to temp I let it run from there. Time it got to 50 the oil was well filtered and dried and ready to put into the clean tanks.

To aid drying I had a fan SUCKING air out the tank. I tried blowing into the tank and curiously, it was as bad as having no air circ at all.  If You could have an open section to your system where the moisture could evaporate, you would be able to dry at the same time.  As fuges don't inherently do that, it was one reason I stuck to settling  and filtering. 

Have to go start collecting some oil again soon.

veggie

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Re: WVO Centrifuge Design - thoughs ?
« Reply #26 on: July 08, 2018, 03:10:00 AM »

All good ideas Glort. Thanks.
Yes, there is an open steam port of the lid of the unit. I will report back on how effective that is.
The planned temperature for oil entering the Fuge is 80C.

BruceM, I will look into sizing a heavy duty resistor for dropping the voltage (speed) to something usable.
Maybe a light bulb or two as Glort suggested as an initial test.

Updates to follow...
Veggie
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BruceM

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Re: WVO Centrifuge Design - thoughs ?
« Reply #27 on: July 08, 2018, 04:18:25 AM »
I also use 12V light bulbs for power resistors, I've got 15, 25 and 50 watt bulbs in standard lamp bases. Walmart carries the 50 watt ones.  I also have a 30 year collection of power resistors left over from various projects, and where I guessed wrong on value.  Adjustable ceramic wire wound unit's in fairly high wattages are very handy...Digikey carries those.

I like induction motors, too, for something like this. A brushed DC motor on a load resistor will vary in speed with load.






AdeV

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Re: WVO Centrifuge Design - thoughs ?
« Reply #28 on: July 08, 2018, 11:04:32 AM »
BruceM, I will look into sizing a heavy duty resistor for dropping the voltage (speed) to something usable.
Maybe a light bulb or two as Glort suggested as an initial test.

Why not see if you can get a blower fan speed controller from a scrap car? Certainly in older cars, these were simply resistor packs wired in series with the blower motor... If you can find a 3- or 4-speed one, then you've got a realtime speed control system AND a natty dashboard :D
Cheers!
Ade.
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glort

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Re: WVO Centrifuge Design - thoughs ?
« Reply #29 on: July 08, 2018, 12:26:18 PM »

Good idea but be aware that the resistor is generally in the blower housing and is a flat unit that sits in the airstream for cooling.
You'll want the resistor the switch and at least the ends of the wiring harness they connect to.

Newer cars ( up to 10 YO) can have 3 phase blower motors and are controlled by a PWM from the computer or a separate control box.  Your best bet will be something 10 yrs+ .