Meth mixer ideas
Pump too much meth, too fast, into the oil in your pipework and you get all sorts of quality variances which will give disappointing results. Feed it in nice and slow, and results seem repeatably good.
What is 'too much' meth? Well, I've worked on the basis that because we aim for around 20% meth:oil ratio in the reaction tank, a similar concentration in the pipework should be a safe limit to work towards.
All we need is a way to limit that concentration, without having to carefully adjust valve openings each time. I want to be able to open a valve fully and know that I'm feeding in at the right rate. That way I'm going to be reasonably confident that my batches will be consistent, all other factors being consistent too.
Here's how I do it ...
I use 20mm inner diameter (22mm o.d.) copper pipe for oil feed and recirculation.
I figured if I feed meth in thru a tube with around 20% cross sectional area of the oil pipe, I should be somewhere around the right mix ratio.
Cross sectional area of pipe = Pi x r2 and I'm making a really rough guesstimate to the flow relationship!
So, I use 8mm inner diameter copper pipe for the meth feed, which is around 15% of the area of the oil pipe, but I have the meth pipe poke into the stream of oil by around 8mm, and that seems to give around 20% mix ratio.
I've ended up with the meth pipe being cut at a 45 degree angle and this seems to help give consistent flow rate, and probably helps add turbulence to improve the local mixing before it hits the pump.
The open face of the 45 degree cut faces downstream to help the oil 'drag thru' the meth.
Here are the parts I use...
From top to bottom...
- 22mm/15mm/22mm Tee
- 6cm of 15mm copper pipe
- A copper push-fit 15mm insert
- 7cm of 10mm o.d. (8mm i.d.) pipe, with a 45 degree cut one end
- A 15mm gas rated ball valve (yellow handle)
These are the 15mm push fits I used...
Slide the pushfit onto the pipe with 45 degree cut.. Have the collar of the pushfit come right up to the edge of the 45 degree cut. Gently crimp the pushfit with a pair of pliers so it stays put.
Now solder the pair together for permanent security.
Slide the 15mm pipe onto the assembly, and solder the collar in place. Try not to get solder on the outside of the 15mm tube, or you'll have trouble sliding on the compression fitting.
A simple way to avoid solder on the outside is to wrap masking tape all round the outside of the tube while you solder, then unwrap it when done.
Next fit the assembly into the tee piece and tighten up. Add ball valve, and you're ready to roll.
A closer look into the feed, from the downstream side...
Good luck, hope it helps you as much as it's helped me.
I've used parts easily available in UK, but I'm sure you can adapt the idea to suit whatever you've got available in your part of the world.
Graham
You can email me at grahamlaming at hotmail dot com
Posted Dec 29 2005
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