Author Topic: Centrifuging Biodiesel (Read 15081 times)

dgs · « **Reply #30 on:** September 07, 2015, 12:15:03 AM »

Ran it up again this afternoon, same thing. It really does sound like an internal metal to metal noise.

Centrifuge spec, at 90psi flow is 7lpm.

Pump spec, flow 9lpm, max pressure 180psi (12 bar)

Can't get the pressure above 75psi. I wonder if it's because it's bio and not oil.

Jamesrl · « **Reply #31 on:** September 07, 2015, 12:50:32 PM »

My pump has an adjustable pressure bypass, maybe yours has.

dgs · « **Reply #32 on:** September 07, 2015, 01:31:08 PM »

Yes it has Jim and it looks to be screwed all the way in, should I unscrew it to try.

I think I have sorted out the fuge problem, will post later when I have more time (will take a little explaining)

knighty · « **Reply #33 on:** September 07, 2015, 04:55:23 PM »

any idea what flow rate you're getting ?

can you catch some in a bucket and check ?

most gear pumps have a very flat pressure/flow curve

it's it's 9litres/min max pump, and the fuge is letting 9litres/min through it then they'll be naff all back pressure against the pump

it's like sticking your finger on the end of a hose pipe... you can move your finger around and change the pressure and how the water squirts out, but you still get practically the came amount of water through the pipe and out the end ?

dgs · « **Reply #34 on:** September 07, 2015, 06:31:32 PM »

Don't know Knightly, I'll have to check.

Fuge is rated at 7lpm at 90psi.
Pump is rated at 9lpm 12bar max (180psi)

With those figures I would have thought it should easily get the fuge up to 90psi but 70 it is!

I phoned stationary engines this morning who told me they don't sell centrifuges any more and haven't done for 2 years.
So, went into the bio room and had a ponder. Got hold of the fuge and tipped it upside down to slide the bowl up and down on the shaft. I did the same with the old fuge and found the bowl on the new one had a massive amount of float on it, probably 3 to 4 mms.

I've been told that overtightening the nut at the top of the bowl that holds the whole assembly together can lead to distortion so it should only be hand tight (even though it has 2x spanner flats on it!)
overtightening can lead to distortion apparantly and 'squashes' the bowl giving rise to end float.

With this in mind I placed a washer on the shaft before putting the cover on and ran the thing up and noticed the vibration noise was less. I then put 3x washers on the shaft and it improved again.

I then made a silicone 3mm washer for the shaft top and ran it again. Result was a near perfect run! I will have to do a little more adjusting but that seems to have sorted the problem out. So has the bowl been distorted by someone tightening the nut with a spanner- anyones guess.

All I have to do now is get to the bottom of this low pressure thing.

dgs · « **Reply #35 on:** September 08, 2015, 05:29:48 PM »

Spoke to Commercial Fuel Solutions today (suppliers of the pump) and they can't understand why the fuge won't pressureise to more than 70psi.

They said that they would get someone in the technical department at Piusi to phone me. No one phoned.

Jim, I checked the by-pass and it's screwed all the way in, if I unscrew it the pressure reduces. I am sure if I was pumping hot oil the pressure would be higher. Probably all the people I've spoken to don't realise some of us fuge bio.

I'll speak to the pump people again tomorrow and be a little more direct with them. After all they did confirm the pump would be more than adequate for the job.

It looks to me as if this is what I should be using.

http://www.commercialfuelsolutions.co.uk/piusi_viscomat_electric_oil_transfer_pump.html

Model 230/3m

Jamesrl · « **Reply #36 on:** September 08, 2015, 08:32:07 PM »

This is my pump Dave, not sure what make it is as the terminal box and fan cowling were smashed when I acquired it.

I printed new parts for it and 7bar doesn't bother it.

therecklessengineer · « **Reply #37 on:** September 09, 2015, 07:34:14 AM »

Quote from: dgs on September 08, 2015, 05:29:48 PM

Spoke to Commercial Fuel Solutions today (suppliers of the pump) and they can't understand why the fuge won't pressureise to more than 70psi.

Am I right in thinking that these fuges use a small turbine wheel and a nozzle for rotation?

If so, then the significantly lower viscosity of bio won't generate the same pressure against the nozzle as with lube oil. You'll need to run the pump faster, or use two in parallel. Or use a small nozzle - but then that might not match with the turbine - maybe.

dgs · « **Reply #38 on:** September 09, 2015, 09:15:50 AM »

That is something I have considered, using smaller jets but I don't know if they are available. I've considered using the jets out of the smaller centrifuge if they would fit but as you say they will not match the centrifuge. The easiest way is to use a stronger pump.
Even at 70 psi the thing is really turning at some speed but when I'm using it on bio my thoughts are in order to extract any remaining sub micron glycerol I need to get every ounce of efficiency out of it.

Until I get the pump situation sorted, probably tomorrow I will centrifuge the whole batch with soap tests before and after just to try and see what is happening.

knighty · « **Reply #39 on:** September 09, 2015, 10:39:15 AM »

can you put some cold oil through it to see what sort of pressure that runs at ?

and/or

you could fuge your bio, clean the bowl out, and then fuge it again... if the bowl is clean after the 2nd pass then the 1st pass cleaned the oil perfectly and you don't need any more pressure anyway ?

dgs · « **Reply #40 on:** September 09, 2015, 02:56:41 PM »

Rational Thinking, Knightly.
I've just done a similar thing. Soap tested some partially settled bio, fuged it once and tested it again.

Before 83ppm After 70ppm. I wouldn't have thought this was good. Quite a lot of liquid glyc in the bowl, not stuck to sides like the other fuge.

Right, found out the jets are interchangeable. So put the old jets out of the small fuge into the new, larger one and it easily pressurises to 100psi+. Lower rpm at higher pressure with these jets, noticeably smaller hole in them. I think this proves the pump isn't up to the job.

knighty · « **Reply #41 on:** September 09, 2015, 06:45:39 PM »

that's a shame :-(

is the pump new ? any chance they'll take it back ?

dgs · « **Reply #42 on:** September 09, 2015, 10:08:05 PM »

Quote from: knighty on September 09, 2015, 06:45:39 PM

that's a shame :-(

is the pump new ? any chance they'll take it back ?

It is new, and yes they will, but they are not pleased about it. After all they did confirm to me it would suit the fuge. One of the partners blew his top with me, saying he was a 'fluid engineer' and the pump was suited to the fuge. He told me
I should restrict the flow exiting the fuge then I would get more pressure, I told him I couldn't do that. He then got into a frenzy at the other end of the phone. What a strange man, but I kept my cool. I will speak to the other man there tomorrow and see if they are willing to supply me with the more powerful version. I hate situations like this, but I'm learning fast about fuges and pumps.

Manfred · « **Reply #43 on:** September 09, 2015, 11:02:41 PM »

What sort of fluid engineer would think that you could restrict the outlet of a fugue to increase its pressure ? Nob.

dgs · « **Reply #44 on:** September 09, 2015, 11:55:30 PM »

Exactly. The saga continues......................

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