Author Topic: Venturi won't suck up methoxide. (Read 8187 times)

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?

Jamesrl · « **Reply #1 on:** March 27, 2015, 11:03:00 PM »

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.

julianf · « **Reply #2 on:** March 27, 2015, 11:47:20 PM »

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.

Glycer-rides · « **Reply #3 on:** March 27, 2015, 11:53:35 PM »

If you've an eductor, flick the lever valve on and you can back-flush any solid glyc. blockages out of the venturi.

neisel · « **Reply #4 on:** March 28, 2015, 08:37:12 AM »

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.

Chug · « **Reply #5 on:** March 28, 2015, 09:19:42 AM »

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.

neisel · « **Reply #6 on:** March 28, 2015, 09:54:12 AM »

I don't have an eductor.

How can I backflush with my set up?

julianf · « **Reply #7 on:** March 28, 2015, 10:20:50 AM »

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.

neisel · « **Reply #8 on:** March 28, 2015, 10:51:25 AM »

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?

Jamesrl · « **Reply #9 on:** March 28, 2015, 12:20:02 PM »

So where is the venturi?

?

neisel · « **Reply #10 on:** March 28, 2015, 01:48:34 PM »

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.

Jamesrl · « **Reply #11 on:** March 28, 2015, 02:18:06 PM »

It appears to be prepump injection and NOT a venturi.

No wonder you always had problems with it. What pump is on the machine?

neisel · « **Reply #12 on:** March 28, 2015, 03:54:34 PM »

One of jgs600's 50lpm pumps.

greasemonkey · « **Reply #13 on:** March 28, 2015, 04:11:48 PM »

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.

Jamesrl · « **Reply #14 on:** March 28, 2015, 05:18:30 PM »

Quote from: greasemonkey on March 28, 2015, 04:11:48 PM

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.

Biopowered - vegetable oil and biodiesel forum

Biodiesel

Biodiesel equipment

Venturi won't suck up methoxide.