Venturi, or tip in before the pump?

[greasemonkey]

I don't really want to make (or buy) a venturi just at the minute. If possible, I would like to have methoxide introduction through a port, just before the pump.

What do I need to consider?
Will the methoxide go in, even if the container is lower than the level of the oil in the reactor?
Introduce it as close to the pump, or further away, or no difference?

Would it be beneficial if the port was larger/smaller than the pipework? (22mm pipework)

Cheers.

[julianf]

Ages ago, i used to routinely suck in the methoxide using the sight tube...

This was irritating and clumsy, but there was no real problem with introducing it like that (possible explosion / non atex issues aside : )

[Rotary-Motion]

use a lever valve + rubber pipe, teed off main flow,  into meth container,  before pump, open slightly to suck meth...

[Tony]

It's one of those things that sounds like it should work better than it actually does...

[Julian]

I think KH uses the pump to entrain methoxide.


I've wondered, and posted on here, if that's not a better way of doing things as the two constituents travel to The pump quickly and under go intense mixing.

I think it should be OK if two parameters are met:  1) you use the sight tube (as Julian suggests) as an indication that the pipe is under suction and 2) that you don't introduce the methoxide so quickly that you have a dangerous mixture hitting the pump.

I'm sure Keith will be able to elaborate.

As an alternative, if you have compressed air handy you could introduce the methoxide by means of pressurising the container using suitable safety measures.

[Rotary-Motion]

the lever valve idea i wrote above did come from K.H's setup... think it works very well.

not sure if his pump was atex rated or not? think lever valve only needs a slight / tiny openning to pull in very slowly to mix, could use a reducer pipe say down to 8mm, to allow valve to open fully and keep the same delivery speed for every process / batch.

[nigelb]

So long as the level in the methoxide container is above the pump at the start of the suck it'll continue to the bottom of the barrel. It goes without saying....but I'm saying it anyway...the bottom of the reactor needs a valve on it so it can be closed off during induction.

Having said that...a venturi will give you some versatility within the plant to reintroduce any samples taken during production. Also good for small additions of methoxide that you may need to take the reaction to completion.

I wouldn't be without mine. I think, when rigged with the right pump and pipework, they're great.

[K.H]

Everything goes in via an inlet before the pump, meth, glyc water and one marble!, it has a length of pipe on it which i just stick in the tub, half shut down the valve before the pump and open the tee,d off inlet and in it goes, both valves will control the intake rate, no worries about the height of the container, i just sit it on the floor, the valve can also be used for samples and draining if you wish.
It will empty a 20 litre cubie in under a minute when im sticking water in although i slow it down for the meth.
I wonder what the optimum mix is?, i know common wisdom has gone from 20 minutes to as fast as possible now
Oh and non Atex pump

[Julian]

...the bottom of the reactor needs a valve on it so it can be closed off during induction.

If I've understood what you're suggesting, I think that statement should read "... so it can be restricted during induction."  If it's closed the implication is that you'll be pulling neat methoxide through the pump which would be a big no, no.

[greasemonkey]

Brilliant, thanks guys. It did occur to me today that the spec on the pump I have says it will lift so many meters, so it should draw out just fine. I'lll have a valve on the bottom of the drum to restrict the floww, or shut it off all together if needed.

It would be nice at some point to fit a venturi, but right now it's just a case of the cheapest and quickest way possible to get the thing running.

Many thanks.

[Julian]

Read the Appleseed section of the wiki.  Methoxide is drawn into the system using the pump in the same way.  having just read it I think it needs altering to say restrict the main flow via V1.

Found a mistake in the table too ... now corrected!

[nigelb]

...the bottom of the reactor needs a valve on it so it can be closed off during induction.

If I've understood what you're suggesting, I think that statement should read "... so it can be restricted during induction."  If it's closed the implication is that you'll be pulling neat methoxide through the pump which would be a big no, no.

What I've described is what I do for the induction of my oil and also my glyc for the prewash. This I failed to explain. However, if inducing methoxide you may need to do the same in order to draw the fluid into the reactor!

Why is pulling neat methoxide through a pump a no no? What is the issue? Is it the flammability or the corrosive aspect of the solution you have issues with?

Whatever the outcome of the opinions you put forward, surely this drives home the need for a venturi.

What  methoxide/oil ratio do you deem safe when using the pump induction method?

[Rotary-Motion]

does it need V2 and V3 ?

[Head Womble]

...the bottom of the reactor needs a valve on it so it can be closed off during induction.

If I've understood what you're suggesting, I think that statement should read "... so it can be restricted during induction."  If it's closed the implication is that you'll be pulling neat methoxide through the pump which would be a big no, no.

What I've described is what I do for the induction of my oil and also my glyc for the prewash. This I failed to explain. However, if inducing methoxide you may need to do the same in order to draw the fluid into the reactor!

Why is pulling neat methoxide through a pump a no no? What is the issue? Is it the flammability or the corrosive aspect of the solution you have issues with?

Whatever the outcome of the opinions you put forward, surely this drives home the need for a venturi.

What  methoxide/oil ratio do you deem safe when using the pump induction method?

I have found that when introducing neat methoxide straight into the pump it boils and cavitates in the pump,
so it needs to be done slowly.

[thewormman]

It would be nice at some point to fit a venturi, but right now it's just a case of the cheapest and quickest way possible to get the thing running.

How much do venturis cost then?