So that was scary...

[NormandieStill]

So I've been working on a steam setup for stripping and, eventually, for cooking corn. In it's first iteration it lacked a PRV (it had a manometer and ahand-operated panic valve) and for the whole time that I was stripping I sat next to it with my eyes glued to the manometer. It was also all copper pipe which required some pretty good alignment of the two vessels.

So I bought some CSST and a PRV and split it into two modules. The first sits on the steam generator (a simple keg still) and the second is the steam pipe which feeds into the side of my normal still. The two can now be sat as I want and I can easily replace the second module with a steam wand for cooking corn.

Having finished the soldering and manual cleaning I thought I'd do a vinegar steam run which would double up as a test. And since I'm testing, I thought I'd close up the valve and check the PRV. After various calculations I'd decided on a 2 bar unit which still gave me 3 bar of margin over the rated pressure for the keg (which is still below the actual test pressure).

Knowing this is absolutely no comfort though, while watching the needle climb on the manometer and trying to work out how far back you can get while still reading the dial! I let it get to 2.3 bar before I heard the steam starting to hiss out of the PRV and the pressure stopped climbing. Then I opened the valve and ran steam through the wand.

Fuck me that's terrifying! The noise of steam at 2.3 bar releasing through a 22mm pipe will probably give me nightmares. It literally screams. After about 30 seconds it had finished dumping the excess pressure and settled down, pumping a steady stream of vinegary steam out of the wand.

I was already fairly wary about using steam, but this did nothing to calm me. Even with the PRV I suspect I'll be monitoring that dial like a hawk!

[Bradster68]

My household projects have kept me from venturing beyond the norm. And even the normal for the past few months.
That sounds like an awsome setup. Good luck and stay safe

[jonnys_spirit]

Did you happen to measure the internal temp whilst under pressure? That would be another metric to correlate a hazardous situation.

Cheers,
j

[NormandieStill]

Did you happen to measure the internal temp whilst under pressure? That would be another metric to correlate a hazardous situation.

I have no temperature gauge, but since temp and pressure are correlated, if my pressure gauge was correct, the exiting high pressure steam would have been somewhere around 135°C! Hot enough to make a mess.

[shadylane]

After various calculations I'd decided on a 2 bar unit which still gave me 3 bar of margin over the rated pressure for the keg (which is still below the actual test pressure).

OOOHHH shit.
2 bar, that's 29 psi for metrically challenged folks.

I'd recommend 2 psi max pressure and a 6 foot tall manometer.

[NormandieStill]

After various calculations I'd decided on a 2 bar unit which still gave me 3 bar of margin over the rated pressure for the keg (which is still below the actual test pressure).

OOOHHH shit.
2 bar, that's 29 psi for metrically challenged folks.

I'd recommend 2 psi max pressure and a 6 foot tall manometer.

I no longer have my working so I don't recall where I got the number from.

As a consequence I've successfully tested the soldered on ferrule where the element mounts and the original ferrule at the top is welded. The keg is rated for 5 bar. If I ever want to play with pressurised steam for running a closed loop heating system then I'm already good to go!

[LWTCS]

2 bar?
Don't need half of that to get the job more than adequately done at the hobby scale.

[NormandieStill]

Yeah OK. I'll replace the PRV with a slightly lower rated one. Maybe 0.5 bar.

[subbrew]

That keg rating is for an unmodified keg. Once you cut it and add ferrules and such that rating no longer applies. Steam contains a lot of energy. So keep plenty of margin of error.

But it is very cool idea and you seem to have it under control. I am impressed and a bit inspired. I really like the idea of steaming corn in place.

[Dancing4dan]

After various calculations I'd decided on a 2 bar unit which still gave me 3 bar of margin over the rated pressure for the keg (which is still below the actual test pressure).

OOOHHH shit.
2 bar, that's 29 psi for metrically challenged folks.

I'd recommend 2 psi max pressure and a 6 foot tall manometer.

Agree. Way high. Danger close! Check out my steam build. I can open the PRV with a gloved hand by lifting off the ball and it Uses a PRV and a liquid manometer. They will both provide pressure relief.

[shadylane]

Agree. Way high. Danger close! Check out my steam build. I can open the PRV with a gloved hand by lifting off the ball and it Uses a PRV and a liquid manometer. They will both provide pressure relief.

Plus one.

High pressure isn't needed, and progressively more stringent safety rules apply.
Boilers don't have just leaks but become prone to catastrophic failure.
Not something you want, especially if you're already committing a felony by distilling at home.
A 2 or 3 psi PRV (less than .2 bar) and a tall manometer is a safer option when taking risks.

Think of it as putting less stuff in your pockets and wearing a belt and suspenders to keep your pants from falling down and leaving your ass exposed.

[Dancing4dan]

Steam distillation is a great way to cook and strip on grain.

Unfortunately it comes with some potential inherent risk. Risk comes in when the issues are overthought. Off the shelf PRV and manometer gauges add significant risk, in my opinion. They are mechanical, operate at higher pressure than needed for distilling, small orifice to gauges and PRV that are prone to blockage with mash residue, expensive.

Look at a pressure cookers to design steam distillation.

Thumpers ARE a steam distiller.

Once you understand how thumpers and pressure cookers work your design gets pretty simple.

My PRV has a 1/2” orifice as does the liquid filled manometer. Has never vented during distillation even when running the element at 100%. Boiler is a keg. Distillation pot is 20 gallon SS.

Very little pressure builds up. I am able to easily clear the manometer and open the PRV just by blowing through them by mouth.

The path steam follows from boiler to distillation pot (AKA THUMPER) should run on an incline UP from from boiler to thumper. This allows any condensation that forms to flow back to the boiler rather than adding volume to the thumper.

Connection between boiler and thumper must be easy to adjust and connect. Tri clamps and elbows do this.

[TwoSheds]

FWIW, I run a converted keg with manometer coming off the top. The manometer is about 2' tall and I half fill it with water. By my calculations 2' of water would be less than 1 PSI and I can easily blow it out with lung pressure.

With my 5500w element on full blast and a still full of on-grain bourbon I don't see the manometer climb more than a few inches. The steam generator temp does get above boiling but not by too much.

Less of a safety concern, but don't forget about suction too. On shutdown you need to be able to open things up. That's tricky if the water in your steam generator is going to be above the boiling point when the pressure drops to ambient.

Stay safe!

TwoSheds

[HDNB]

yeah, you want a vacuum breaker on that thing too. that will really scare the shit outta you if you pull the vacuum break....they scream loud.

i use 15psi PRV on my supply to jackets and set the boiler to 11. popped it a few times throwing a valve closed quick, always an exciting blast of wet steam.
on the boiler itself i have a 3psi PRV / vacuum break. collapsed the vapour once when i accidentally hit the cip water valve and set the vacuum break off, just about shit a kitten, claws and all. I never want to test that 3psi PRV under any circumstance.

[Dancing4dan]

Less of a safety concern, but don't forget about suction too. On shutdown you need to be able to open things up. That's tricky if the water in your steam generator is going to be above the boiling point when the pressure drops to ambient.

A liquid filled manometer will work as a vacuumed break as long as the manometer tubing has a large enough diameter.