New pump

[Julian]

Just dewatered and at 70^oC the vacuum gauge reads just about 28"Hg, with a perfect vacuum being in the region of 30"Hg, it's a bloody good pump/venturi combination or my gauge is a little out ... I suspect the latter!

It started condensing at 65^oC, way lower than with the Leo, so looking good for demething.

One strange thing ... I had the PID set at 90^oC and the shutdown at 93^oC and left it to do it's stuff for a little while.  When I came back the PID had tripped out on high temperature.  This has never happened before and I'm wondering if the temperature rise I saw during testing had any effect.  I'm rather doubtful, but I can't think of any other cause.

Another bonus point, despite being much larger, the new pump seem quieter than the Leo.

[Head Womble]

Sounds like that new pump is transferring a lot of heat into the bio, is the impeller rubbing the housing ?

[julesandtash]

Any idea what power consumption is like on that pump Julian.

The spec says 1500W (as opposed to 330W for a TAM105) but then I suspect it would only use that pumping at it's ridiculously high maximum head of 65m.

I bet the starting current is pretty high though starting a motor like that with the pump full of cold oil.

[Julian]

Sounds like that new pump is transferring a lot of heat into the bio, is the impeller rubbing the housing ?

I'm sure.  It might have something to do with my pipe work and the fact that it's running against a 6mm venturi.

[Julian]

Any idea what power consumption is like on that pump Julian.

The spec says 1500W (as opposed to 330W for a TAM105) but then I suspect it would only use that pumping at it's ridiculously high maximum head of 65m.

I bet the starting current is pretty high though starting a motor like that with the pump full of cold oil.

Yes, the lights dim slightly when it starts, but according to Keith, it's not that big.

The business end looks to be the same size as Heather, so despite her much bigger motor, I'm wondering if she's the same/similar capacity.

[Jamesrl]

I'm sure.  It might have something to do with my pipe work and the fact that it's running against a 6mm venturi.

Oi, Acorn, your venturi should have a 9mm throat for that 75l/min pump.

Using 6mm jobby is just loading the pump mota and costing more to run.

[Julian]

I'm sure.  It might have something to do with my pipe work and the fact that it's running against a 6mm venturi.

Oi, Acorn, your venturi should have a 9mm throat for that 75l/min pump.

Using 6mm jobby is just loading the pump mota and costing more to run.

Ah ... I've made so many I lose track.  Thanks for the heads up, I'll untangle some of my pipe work and check the size.

What ever size it is, based on your calculations, it will probably be too small for the pump, but it seems to be performing surprisingly well.  Maybe need to open it up to keep the same suction performance, but see if I can get a better oil flow.

Just checked the wiki and for a 75 lph pump the throat should be 8.5mm, but I'll try a couple of batches as is before changing anything.

[Jamesrl]

The correct size of the throat is 8.92mm but 9mm is close enough.

[Julian]

As it stands, there are some wonderful noises down stream of the venturi.  Wonder if it could be cavitation?  If it is it might aid conversion.

[Jamesrl]

I see the venturi calculator uses a simplified formula, I don't know what it is but it's not producing the correct results.

[Jamesrl]

As it stands, there are some wonderful noises down stream of the venturi.  Wonder if it could be cavitation?  If it is it might aid conversion.

The noise could also be the vacuum collapsing on the low pressure side of the throat.

[Julian]

I see the venturi calculator uses a simplified formula, I don't know what it is but it's not producing the correct results.

Toooonyyyyy

[Julian]

As it stands, there are some wonderful noises down stream of the venturi.  Wonder if it could be cavitation?  If it is it might aid conversion.

The noise could also be the vacuum collapsing on the low pressure side of the throat.

Sounds to be coming from the down stream end of the discharge cone ... surely no vacuum at that point.  Also if the vacuum was collapsing and re-establishing wouldn't that show up on the gauge with the needle vibrating.

Just thinking back to that utube video where they were producing cavitation with a partially closed valve.

[nigelb]

What you've described there Julian is exactly what happens on my plant. As you may recall I recently added a new, more perfectly formed, venturi with a throat of 9.5mm . You may also recall that I mentioned the possibility of cavitation from the previous venturi (9.3mm). The new one is just the same.

I overcome the noise by allowing the vent valve to be slightly open.

[Julian]

Ran a batch today.  Very pleased with the pump, processing times are about 2/3 what they used to be and demeth time is brilliant.  I got a litre in the first 10 minutes and 5 ltrs in the first hour.

I ran it for an hour and a half and managed to squeeze 6 ltrs out ... well pleased with my 14 quid investment ... everything is good with the world ... well almost everything.  Just need a buxom blond waiting for me upstairs with a large glass of Laphroaig.