Venturi won't suck up methoxide.

[neisel]

So then, the plan is to take off the straw / pipe & the shiny metal 'L' shaped bit it's seated in, have a look for leaks, cracks etc that are killing the vacuum & fix it if possible or get a replacement.

Anybody know where I can buy a new one of these things, should I need one?

BTW, the AAF try has not been a success. 140 litres of crystal clear oil taken from the top of an IBC after sitting for about 8 months was only about 50% converted after 20 litres & 980 grms of KOH, a further 10 litres & 450 grms inexplicably seemed to have absolutely no effect whatsoever on converting the rest, so great big bolshy yarblockos to that!

I've pretty much given up on that now, I'm going to wait until my machine is working & do it the old fashioned way.

[Jamesrl]

Did you dry the oil first then heated to at least 60c befor you pumped it in ontop of the methoxide?

As for the vacuum repare get rid of the bend and pathetic piece of tube. You need a 3/4" or 1" to 15mm compression fitting and a short length of 15mm copper tube, once fitted use 13mm braided pvc as the flexi part and don't forget to use a jubilee clip on the joint.

[Julian]

Just for a balanced view and to indulge a little controversy ...

I use 6mm silicone tube to pickup my methoxide, and it's connected to the venturi suction via a lightly barbed hose tail without a hose clip!

I know the 15mm plumbing push-fits are pants at holding vacuums but I'd have thought with the compressed air fittings and Nylon tube, you'd stand a fighting chance.

Also I've used Nitrile O rings in the assembly of my venturi for several years without problem.  In normal sealing applications, only a tiny surface area of an O ring see the fluid it's sealing.  Even less if less if ant at all if anti-extrusion rings are used at higher pressures.

[greasemonkey]

I can see what you are saying, and no doubt with a venturi, it would stick a little bit of air ingress, and just keep sucking.

Getting it in before the pump is a little more tricky, and as soon as the tiniest bit of air gets in, the whole lot collapses.

I'm not entirely sure why, but it's either working, or not working, there doesn't seem to be any in between.

[Tony]

Venturis work best with a reasonable amount of pressure driving them, is the pump up to the job?

[Tony]

An absolutely minute inward leak on a vacuum tube will stop the system working.

Outward leaks on a vacuum tube, on the other hand, are nothing to worry about!

[neisel]

JamesRL,

Last June the oil, clear & without whites, was run through a tight sieve & & has sat in an untouched IBC since. It was heated to 70 & glyc washed for an hour, then dropped out of the processor. Methoxide in, oil back on top, pump turned on & away we went.

I'm surprised as I thought the logic behind this made sense. Don't know what happened, maybe I did something wrong but TBH the way I've been doing BD, with my silly straw & all, has worked very well for thousands of litres of good quality BD & once the sucky device is up & running I shall be returning to the way I've been making it.

Greasemonkey,

As I mentioned in my post with the pictures, a small amount of oil can be seen weeping out of the tube where it meets the shiny metal coupling so I reckon there is a leak there. I'll take it off on Tuesday when I have time & investigate. Can you suggest where I can buy a replacement?

[Jamesrl]

JamesRL,

Last June the oil, clear & without whites, was run through a tight sieve & & has sat in an untouched IBC since. It was heated to 70 & glyc washed for an hour, then dropped out of the processor. Methoxide in, oil back on top, pump turned on & away we went.

And there's the problem, you need to pump the oil into the methoxide to start a super reaction, not dump the lot in and the start mixing.

I pump hot oil, approx 70c, into the methoxide at 12m/sec through a 6.5mm nozzel at approx 40lmin. If I'm aiming for a single stage I can get a clear 10/90 in as little as 15mins. Two staging I get 90%+ with only 15%meth and 3g/ltr NaOh.

Done right AAF really works.

What you did was a poor version of a normal mix hence the result

[greasemonkey]

Venturis work best with a reasonable amount of pressure driving them, is the pump up to the job?

It ain't a venturi. It just works be carefully balancing the valves, to get the pump to suck out of a container.
I'm not entirely sure how it does work actually. Is it the pump picking the liquid up, or the vacuum created by the oil moving through the pipe that picks it up? Either way, once it gets going, it sucks pretty good. Just gotta be real patient with the valves.

[greasemonkey]

As I mentioned in my post with the pictures, a small amount of oil can be seen weeping out of the tube where it meets the shiny metal coupling so I reckon there is a leak there. I'll take it off on Tuesday when I have time & investigate. Can you suggest where I can buy a replacement?

All I've got is a piece of garden hose whacked over a piece of 15mm copper, which is soldered into a fitting, on the bend that comes out of the processor, and into the pump. I just warmed the hose up on the stove, and pushed it over.
It's crude, the the hose is brittle till it's warm, but it works. One day, the hose will snap off altogether.

Any plumber or builders merchant will have the some bits to bodge it up. They may not be the cheapest, but it's only gonna be a few quid.

[neisel]

Turned out to be just an O ring.

Easy fix & now works better than before.