My fuel processor just IMPLODED

[Tony]

So I was demething a batch, up to 90C, without running the pump and venturi, as you do (OK, so usually I do run the venturi to speed things up).

I come back and lots of lovely meth in the collection drum.  I know, I'll turn the pump on and see if any more comes out at the same temperature without heating it further just by using the venturi.

Pump goes on.

**WHUNK**

Distillate drum and processor simultaneously jump into a smaller shape, cracking the cylinder's insulation in the process.

I can only assume that the cold plug of liquid below the heater element being transferred into the 90C head space shrank the pressure so quickly the vent couldn't keep up.

Fortunately it retained structural integrity and I pumped the batch out to settle.

So now I've got to return it to its former shape, maybe with a few PSI of compressed air or by pumping oil into it with the vent blocked (and hope it doesn't split!)

[Tony]

A healthy blast of compressed air up the vent pipe seems to have returned it to an approximation of its former shape (after a number of alarming noises) 

[Julian]

Blimey Tony! Lucky it retained the bio and glad it's almost back to normal.

I had the vent block on my processor about a year ago but with less serious consequences.  It seemed to be "gunk" that had built up right at the end of the pipe outside.  I can only assume it was stuff that had condensed out and solidified, although I find it hard to believe.

I wondered then why GL put the vent where he did.  Any issue with the PD blocking or distillate container filling and backing up, blocks the vent.  I recon it would be better to vent with a dedicated, large bore pipe direct from the ullage space of the processor... or have I missed something.

[Tony]

One of my first builds was vented directly from the ullage space.  I only moved it to be like the GL design because I figured that if you're heating like I was (with the circulation pump off) then any methanol vapour won't be collected by the condensor.

[Keef]

Time to get that 400 litre steel jobby of yours finished?

[Tony]

Time to get that 400 litre steel jobby of yours finished?

It is a good motivator to get on with it.  Just need to refill my weld gas bottle!

[Julian]

Never heard of demething with the pump off ... is it very effective?

Perhaps an alternative would be a bursting disc arrangement.

Quite easy to make and test, just need  a weak, bio, methanol, caustic and heat proof membrane clamped between two flanges.

[Tony]

The top of my processor is a soft soldered bursting disc of thin copper carefully formed to seal against the inverted base of the copper cylinder which is much thicker - just in case of methanol explosion.  But clearly works rather too well under vacuum, didn't budge!

Yes demething without venturi works absolutely fine.

[Julian]

I was thinking of something like polythene ... I know it wouldn't take the heat, but that kind of thing.