DIY syphon nozzle

[Tony]

Well, this 2.4 nozzle arrived:

http://www.ebay.co.uk/itm/191576261067

Says 3.2 on the side (listing does show that actually).  Nozzle is 2.0mm at the flat end, 2.75mm at the threaded end.  No idea where 2.4mm comes from.  I guess I can drill it out or try the next size up.

Might try this one, SUPPOSEDLY 3.2mm

http://www.ebay.co.uk/itm/Draper-3-2MM-SPARE-NOZZLE-SPARES-CHARGES-/310488005442

£2.22 and it comes with a free tape measure, bargain!  Edit: And 10% off if you buy two.

[Tony]

I got the gear pump VFD back up and running (turns out a long press on the control knob puts it into remote control mode and the keypad is then ignored) and have spent an evening of experimenting.

The unfortunate conclusion is that it's designed to pump light lubricating oil only.  Anything too thick like glyc or even liquids that don't lubricate it enough like water cause it to stall.  Same with restricting the output.  So I suspect it was intended to pump lubricating oil onto cutting surfaces in a machining environment.  It pumps bio OK, which is what I've used it for before (low power circulation pump).

Too much flow and not enough torque (it's only 120W) to be a burner fuel pump - back to the drawing board!

[Tony]

I found this in the shed!  greasemonkey may remember it from a BBB where we tried to dismantle it and only succeeding in breaking a (very crumbly) circlip (don't judge us, we're both a bit obsessed with brass things):





Good job I checked the wiring before connecting it up, no earth..! 



Anyway, it runs (and pumps) and is a candidate for being a fuel pump for the burner.  I think it's a little vane pump in the style of Rotoflow pumps.

[Chug]

Good to see you're still at it Tony, keep up the good work!

[Tony]

Good to see you're still at it Tony, keep up the good work!

Hehe plugging away!  I think this pump has an integrated overpressure bypass, only one way to find out though

[greasemonkey]

Ah yeah, I remember that. Huge great motor, and a tiny little pump.
Might be worth sticking a circlip back in it.

[Tony]

Got one on order, I think it's a standard 47mm circlip.  That disc at the front keeps the liquid in as I found out playing with it in the garden, err, I mean, "technically assessing it".

The motor might be huge but it's only 1/6 HP. But that's old tech for you, it spun up after no doubt a decade or more of sitting idle.  I suspect it was built in the 80s.  It has some form of centrifugal start mechanism (additional winding switched in?) integrated into it.

[Jamesrl]

It has some form of centrifugal start mechanism (additional winding switched in?) integrated into it.

Cheap Chinese motors use that system, sort of a centrifugal switch making the capacitor a run one not a start cap.

Well summit like that.

[Tony]

Might try this one, SUPPOSEDLY 3.2mm

http://www.ebay.co.uk/itm/Draper-3-2MM-SPARE-NOZZLE-SPARES-CHARGES-/310488005442

£2.22 and it comes with a free tape measure, bargain!  Edit: And 10% off if you buy two.

The end port on this one is 2.25mm, at the thread end there is a little lip that restricts to 2.0mm - might be able to use this to my advantage to hold the 2.0mm OD stainless tubing, drilling holes for the airway.

It's M8 threaded, just need to adapt this to 1/4 bsp to test it, perhaps drill and thread a 1/4 bsp blanking cap unless anyone knows where you can buy such a crazy adapter?

[Tony]

Also I won this: http://www.ebay.co.uk/itm/Oil-Central-Heating-Pump-/171857673229

I'm assuming they are some kind of low ratio gear pump?

[julianf]

I think theyre bypass, rather than geared, if you see what i mean (indeed, if that is what you were asking?)

So, a gear pump with pressure bypass.  Some of them are configurable so as the bypass goes back to the tank, or is re-circulated.

That thing sticking out the side is a reed solenoid type thing.  Its normally energised by the burner control unit after the fan (motor) has got up to speed to (i assume) give a sharp start to the flow.

You will either need to energise that, or, possibly, remove it.

[julianf]

ps.

IIRC danfoss has reasonable diagrams of that one - i had to fit a new one to our burner once (same type, part number, i think)

[Tony]

Well I replaced the circlip on the scrounged vane pump and plumbed up some fittings with a needle valve to restrict the outlet (it has an internal overpressure bypass by all accounts) and tested it with water - no problems, beyond some weeping at the back of the pump head (must just need an o-ring or gasket).

Then the glycerol test.  As soon as it started POP!  The circlip and front plate blew out, along with a nice jet of glycerol.  I'm a bit gutted, had high hopes for this pump!



Back to the drawing board, and pinning my hopes on the boiler oil pump that's in the post!

[therecklessengineer]

If I was designing a burner to burn glycerol, I'd use a method to that used to burn heavy fuel.

There's normally a fuel system that heats the fuel with feedback via a viscosity meter. From cold, the plant is started on distillate to generate the heat - it's then switched over to heavy and blended until completely running on heavy. This keeps the viscosity within a certain range to keep the atomisation correct and fuel pumps happy. Normally 15-20 cS IIRC.

Smaller system use electric heating rather than steam/thermal oil.

edit: Attached a marine fuel system for burning HFO. It says engine, and no one uses pneumatic controls these days, but hopefully you'll get the idea.

[attachment deleted by admin]

[Tony]

Interesting.  I was thinking that with a larger gear pump the outlet could have a small feed for the burner and an overflow that goes via a coil close to the burner tube before returning to the tank, so it could be started on something thin and then switched to a thicker mix which would get heated.  But the heat delivered to the tank would be unregulated.