Centrifuging Biodiesel

[Manfred]

                    http://www.bellflowsystems.co.uk/centrifuge-for-biodiesel-bio-diesel-engine-oil-and-waste-vegetable-oil-41

 Dave. I can't get the link but it might be my pad acting up.

[Julian]

Last link goes to their home page and searching their site for centrifuge yeilds no results.

Did a search on Google ... was this what you were after?

[Jamesrl]

I missed you Jim.

Of course you have, who hasn't!

Well, I ran the thing today. Slightly disappointed by the top pressure of 75psi with the by-pass valve shut. It certainly turns at some speed, however there is a problem. At pressures over 50psi a loud vibration starts, it sounds like a metal
to metal noise internally.

You need to get 103psi to get max rpm out of the fuge, as for the rattling, yes the bowl will lift at approx 75psi but has it been dynamically balanced or has the balance weight dropped off?

[Julian]

... yes the bowl will lift at approx 75psi ...

Just been looking at the drawing before you posted and was wondering if in fact the rotor moves vertically at all?

If it moves up (or down) it will need some sort of thrust bearing to take the force ... is there one?  I can't see from the detail on the drawing and you've obviously pulled one apart.

From the drawing it would appear that the rotor should be sealed to to the shaft otherwise dirty oil would escape into the clean areas.

[dgs]

The weight is intact Jim and the positioning arrows are exactly in line. When you say the bowl will lift at 75psi is this meant to happen.

[dgs]

I think the internal pressure acting between the shaft and rotor tube gives it low friction like a fluid bearing principle.

[Jamesrl]

The weight is intact Jim and the positioning arrows are exactly in line. When you say the bowl will lift at 75psi is this meant to happen.

There has to be a little vertical clearance to allow expansion of the bowl, don't forget these fuges are designed to filter hot engine oil not cold bio.

[Julian]

My guess (based on the drawing) is that the whole thing won't operate below a certain pressure.  There's what they term a "check valve" impeding the flow which must open at a specific pressure.  I struggling to see why that fitted to be honest.  It may be something to do with being fitted to operating engines which require a pressure in the rest of the system as a priority over running the centrifuge.

Dave, you could try running it without the spring and valve disk?  You may well get more flow that way.  Any pressures you are currently measuring will be of that valve and have little to do with the rotor assembly.

[dgs]

Don't think I can Julian. I think the valve is a safety feature, if the pressure is too high it pushes the valve against the spring and lets the bio bleed through a hole without going into the fuge.

[Julian]

Ah, cant see that on the drawing.  So as a safety measure it dumps dirty oil into the clean oil?

If there's no signs of mechanical contact on the moving parts, could the over pressure part of that valve blowing off be the source of you're noise?

[dgs]

I have considered that and it is possible. If for some reason the spring isn't strong enough the valve could be bouncing off it's seat. However the other thing I have noticed is when it is decelerating from whatever rpm it is doing at 50psi (it is still spinning at a high speed even at this lower pressure and takes around 25 seconds to stop) it goes through another vibration phase (very loud) as it is slowing.

When I phone them up tomorrow as they are only 9 miles away, with a bit of luck if I speak to someone who is helpful and considerate? they may even come out to have a look.

[knighty]

there's a chance there's nothing wrong with it and there's just some odd harmonics/vibration at certain rpm - it doing it again when it's slowing down suggests it might be this...

if you can get it to go faster you might push past the vibration so a spot where it's smooth again


it's a bit like when you have a tyre on your car that isn't balanced very well... it can be fine up to 60mph, start to vibrate, but then by 70 it's smooth again :-)

[dgs]

Thanks Knightly, yes it is possible.
I have a bio friend coming to see me today, he wants to see it working, I'll wait until he's here and 'give it the gun'

[therecklessengineer]

If you're really serious about getting your fuel clean, check out purifiers or as they're sometimes called, separators. Alfa laval and Westfalia are the two major manufacturers. I posted some photos of a strip down on here a while back.

https://www.google.com/search?q=alfa+laval+purifier

[dgs]

They look superb things but arn't they very expensive.