Biopowered - vegetable oil and biodiesel forum
Biodiesel => Biodiesel equipment => Topic started by: neisel on March 27, 2015, 10:51:48 PM
-
Today I started making my first batch of BD since October (I make enough to last through the winter).
All going swimmingly until I need to suck up 20 litres of methoxide for stage 1 & the bloody thing just will not do it. I can see it's trying to as the liquid goes up & falls back down the tube but regardless of how I adjust the valves I end up with nothing sucked up & more volume than I started with as the feedstock runs out into my container. Makes no difference if it has to suck it up 18 inches or 2 inches. It has always been a bit quirky & fiddly to get going but fiddling with different positions & angles usually solves the prob, but this time I did it for about an hour to no avail.
Having a read on here I see talk about blocked pumps in relation to this problem but my pump seems to be pumping as it used to & is quiet. Could there be an air leak in my tube / coupling connector that's stopping this working?
Any ideas?
-
As your system has been idol for a while it'd be best to open the pump and check it out, you never know a couple of vanes could be blocked also check out all the lower pipework.
-
Depending on the design, check for fractures around the tee where the suction enters the main flow. Mine has failed a number of times at this point.
-
If you've an eductor, flick the lever valve on and you can back-flush any solid glyc. blockages out of the venturi.
-
No eductor.
The machine was left with whatever finished BD would remain after pumping out everything that could be pumped from the last batch.
Don't think there would be any glyc (which would be KOH glyc) or at the most only a tiny bit. More likely to be a few HMPEs which will have developed / settled out over time. Yesterday the pump ran for at least an hour at at least 70 degrees so I'd have thought that would have melted & flushed anything, if indeed there was anything to flush.
This a.m. I'm heating up the oil again & am going to finish the batch by using the AAF method, which has always interested me & seems to make sense. I'll soon see.
-
Had this myself, methoxide rises up the pipe partially then stops, you either have a partial blockage somewhere (I backflush as per Andy with eductor valve), or the pipes connections need re-tightening, or a leaking/cracked pipe/venturi.
-
I don't have an eductor.
How can I backflush with my set up?
-
If your venturi has two 22mm compression fittings, then it may be easier and quicker just to take it off and have a good look at it, than doing test after test in situ.
-
This is what I've got. There is a slight leak or weep from the point where the plastic tube meets the shiny metal bit when I'm trying to suck into the processor.
When I've finished this batch the machine will be empty, what point on the pipework does the panel suggest I take this thing off?
(http://i57.tinypic.com/bimiyb.jpg)
(http://i59.tinypic.com/71iazq.jpg)
(http://i60.tinypic.com/2drdzdu.jpg)
-
So where is the venturi?????
-
I'm guessing I'm using the wrong word for what's in the pictures if you are confused. I bought this processor, my first, used from Nathan of centrifuge fame & this sucky thing has always been referred to as the venturi. What is the correct name for it?
By opening the lever which appears to be green in the photos, first having reduced the flow from the bottom of the processor going back to the pump in the reinforced tube you see in the middle photo (by means of another lever you cannot see), as if by magic it empties a container full of methoxide or water, if I'm pump washing.
-
It appears to be prepump injection and NOT a venturi.
No wonder you always had problems with it. What pump is on the machine?
-
One of jgs600's 50lpm pumps.
-
I use the same method of induction. When it gets going, it is really powerful, but it is a fiddle to start it sometimes.
That straw it is sucking through looks like it is pushed into an air fitting, designed to hold pressure in the pipe.
My first thoughts are that maybe there is air getting in through there. It's not designed to keep air out of the pipe. The seal may have gone old and brittle.
You won't hear it sucking in, as soon as it gets a puff of air, it just stops sucking.
-
I use the same method of induction. When it gets going, it is really powerful, but it is a fiddle to start it sometimes.
That straw it is sucking through looks like it is pushed into an air fitting, designed to hold pressure in the pipe.
My first thoughts are that maybe there is air getting in through there. It's not designed to keep air out of the pipe. The seal may have gone old and brittle.
You won't hear it sucking in, as soon as it gets a puff of air, it just stops sucking.
You're spot on there GM, rubber seal and bio don't mix.
An absolutely minute inward leak on a vacuum tube will stop the system working.
-
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.
-
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.
-
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.
-
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.
-
Venturis work best with a reasonable amount of pressure driving them, is the pump up to the job?
-
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!
-
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,
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
-
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.
-
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.
-
Turned out to be just an O ring.
Easy fix & now works better than before.