Boiler Pressure Relief

[Jacksonbrown]

This may cause some cringing but I’ve been a bit concerned about the lack of pressure relief in my boiler.
It’s a completely open system but a blockage in the column could happen and might turn a good day bad.
The cheaper popit valves available aren’t sized correctly to work safely IMO and a commercial pressure relief valve that’s guaranteed to work is a bit pricy.

What about a cheap homemade bursting/rupture disc?

As long as it’s the weak point in the system, it doesn’t need to be certified (commercial, certified bursting discs are VERY expensive)

Three layers of alfoil clamped to my filling/inspection port over a gasket.
I used an old heating element blank but a plain ferrule would do the trick too.
I wanted to test the break point but didn't have the air fittings at hand. Perhaps someone else needs an excuse for some shed time.
It’s a bit rough but I think the idea has merit?
Any suggestions on a better material to use? The foil under a Milo tin?

Ideally I’d like some 304 or 316 foil but I’m not sure if it even exists.

Thoughts?

[Brendan]

My thoughts are: What's going to block your column at a hobby level?

From my understanding, a neglect of cleaning plates in a large scale commercial still has the very minuscule possibility of causing some sort of blockage...and due to their much larger scale, the column pressure between plates can be higher than seen at a hobby level...

But you're talking about a 2" pot column becoming blocked...?

[FreeMountainHermit]

here ya go. http://www.generant.com/VRV.shtml" onclick="window.open(this.href);return false;" rel="nofollow

http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40" onclick="window.open(this.href);return false;" rel="nofollow

FMH.

[Jacksonbrown]

It's a bit like seat belts. I don't plan on crashing any time soon but...

At our hobby level people can still blow themselves up. At our our hobby level how 'bout a particularly gooey wash foaming up clogging the packing. Fruit pulp, excess protein, spent grain, unconverted starch, gerbils I don't know.

I came back to this place after over 6 years hiatus and I think the flavor may have changed. I've heard that term a few to many times me thinks. 'At our hobby level' is a sure way to kill any progression at our hobby level.

Any idea what kind of volume those valves are capable of relieving? I don't know what SCFH is but no point installing them if they're not up to the task.
An open 2" port and a few cents of foil is what I'm wondering about.

4400W with 30l of god knows what in a 50l vessel. Anyone know how to correctly size a relief valve?

[FreeMountainHermit]

How do you like the Torpedo ?

FMH.

[Jacksonbrown]

I just use it as a combined reducer/port. It's had a sight glass in there and temperature transmitter when testing. Usualy it's blanked off. I'm think of making a lance to go in there and pumping air in the product outlet to empty the boiler. Emptying hot wash is a PITA and I haven't seen a good drain design for a keg yet.

[NZChris]

You could hang a U tube on the wall. 27" of water/lb of pressure. You could then keep an eye on the pressure in your still, plus you could use it to double as pressure relief, exhausting any blowouts to outdoors. I'm sure there would be an easy way to get the blowout to cut the heat as well.

I love my dump valve. I can have the heat on the next charge a few minutes after I finish a run. The still is hot and start up time is reduced.

[Brendan]

I came back to this place after over 6 years hiatus and I think the flavor may have changed. I've heard that term a few to many times me thinks. 'At our hobby level' is a sure way to kill any progression at our hobby level

I think you took this the wrong way mate. My evaluation of 'at a hobby level', was referring to the physical size of typical equipment...people don't tend to run 24 inch diameter columns 'at a hobby level'.

I didn't take your query lightly and fob it off...I have looked into this topic in detail myself, including typical pressures seen in commercial sized and hobby sized stills. That term was purely for scientific evaluation referring to a typical size range of plated columns

[Maritimer]

Hi Jackson,

If you are an American, you can get SS foil from McMaster-Carr : http://www.mcmaster.com/#stainless-steel-foil/=q7wgye" onclick="window.open(this.href);return false;" rel="nofollow

A still runs at around a pressure of 7 mm water.

A major safety concern for me is loss of coolant, which would let ethanol vapour belch from a still. McMaster also has flow switches: http://www.mcmaster.com/#flow-switches/=q7wjzl" onclick="window.open(this.href);return false;" rel="nofollow but they are expensive and require a filter. Here is my home-made flow switch : http://homedistiller.org/forum/viewtopi ... 0#p7099554

M

[Jimbo]

Drill a hole in the top and stuff a tapered wine cork in it. If the pressure builds the cork will blow out. It also provides a great place to mount a thermometer by drilling a small hole in the cork.

[DAD300]

+1 Jimbo... that's my fill and siphon port also.

[NZChris]

Because I've seen a pressure cooker safety blow out, I'm not convinced that using a blowout disk is such a great idea for a still. I would see it as the last resort and other safety mechanisms should have to fail first.

When a safety blows, the liquid is boiling at about 3 degrees F higher than at atmospheric for every 1lb of pressure. The liquid boils vigorously until it reaches its boiling point at atmospheric, in the case of a still, venting explosive gas and boiling puke. If you haven't vented to outside, you might have a big problem.

A pressure switch to automatically shut off the heat could be set to operate well before burst pressure is reached.

[Odin]

Yes, NZ, that works well! I have one in mine and it auto shuts down the rig when over or under pressure situations occure.

Odin.

[FreeMountainHermit]

Any idea what kind of volume those valves are capable of relieving? I don't know what SCFH is but no point installing them if they're not up to the task.
An open 2" port and a few cents of foil is what I'm wondering about.

4400W with 30l of god knows what in a 50l vessel. Anyone know how to correctly size a relief valve?

Relief valve is going to relieve excess pressure above your wash.

SCFH ??? Well that took about 4 clicks of the mouse. Sheeeeeeesh.
http://www.google.com/search?q=+SCFH+&ie=UTF-8&oe=UTF-8" onclick="window.open(this.href);return false;" rel="nofollow

You could fit a weight from a pressure cooker or a simple vent to the atmosphere .

[FreeMountainHermit]

Hi Jackson, A still runs at around a pressure of 7 mm water.M

Assuming Maritimers input is on the money then 7mm of WP = .01 psi.

http://www.kylesconverter.com/pressure/ ... quare-inch" onclick="window.open(this.href);return false;" rel="nofollow

OP is overly concerned . JMHO. A simple vent installed so as not to vent towards a heat source should be more than sufficient .

FMH.

[Jacksonbrown]

No worries Brendan .

I toyed with the idea of a hose with water in it but I didn’t have a fittings in my stash to do it. Just like a homemade manometer.
Do you end up with product condensing in the tube?

I like the idea of a silicon bung. Easy to source and effective.

A pressure switch is another option but also getting up there in price.
I don’t think the foil would allow a few pounds of pressure, the break point would have to be tested though. I certainly agree that any build-up of pressure suddenly venting off should be avoided.

I’ll look into adding a flow switch to my cooling recirc as this is another area that concerns me although my flow rates are quite low so getting the right part at the right price will be a challenge.


A boiler in fire can give you a bit of a runaway system that keeps going, a bit like diesel engine runaway.

Or worst case http://en.wikipedia.org/wiki/Boiling_li ... _explosion" onclick="window.open(this.href);return false;" rel="nofollow

[Brendan]

Hi Jackson, A still runs at around a pressure of 7 mm water.M

Assuming Maritimers input is on the money then 7mm of WP = .01 psi.

http://www.kylesconverter.com/pressure/ ... quare-inch" onclick="window.open(this.href);return false;" rel="nofollow

OP is overly concerned . JMHO. A simple vent installed so as not to vent towards a heat source should be more than sufficient .

FMH.

These are similar to figures that I had researched also in regards to hobby sized stills.

The higher pressures were usually only seen in very large plated columns, where the vapour could collapse between plates and cause a pressure differential. On a big commercial column, it's also much harder to clean which is why they use the CIP systems.

0.01psi sounds about what I found for plated columns under 6inch. In terms of a standard pot/reflux still, the only issue I can see even possibly arising, is a puke in a very small diameter column which is too tightly packed with packing material and just somehow an issue arises...I just can't see how it's possible...I mean we're talking about a completely solid obstruction in a 2inch+ column...

I'm not trying to play down the issue, just highlighting the values and trying to identify potential risks. People need to be more worried with the use of gas/open flame around ethanol vapour which could leak, or in liquid form being spilt from a collection vessel.

[Maritimer]

I remember that 7 mm water pressure from Riku's book.

An always-handy units converter is right in the Google query box. Just type in "7 mm water in psi" and the answer will appear.

M

[cob]

even a single layer of aluminum foil holds more pressure than i would be comfortable with.
http://www.spudfiles.com/spud_wiki/inde ... k_material" onclick="window.open(this.href);return false;" rel="nofollow
another site tested 1 layer of foil and 1 layer of postit paper at 1/2" diameter. burst at 144psi.
my old revenoor came with a 1psi pop off upon testing proved to be stuck shut.
think about a stainless foil disk as a diaphram to actuate an NC microswitch to cut power.
if you know a real gunsmith stainless foil is used for heat treating.

[heartcut]

IMO a water manometer vented somewhere safe is the most reliable approach to overpressure, a slip fit cork or fitting is second place but still effective. I monitor my output and coolant flow while running and consider coolant failure to be my biggest potential safety issue. Do think the filling a cup flow switch is a good approach to coolant flow monitoring, I alarm on high product temperature and have plans to automate that into a heat shutoff, so far it's just plans.

[Jacksonbrown]

Great info and link cob. Thanks.

[NZChris]

http://murrayledger.com/news/distillery ... 22073.html

“It’s an ongoing investigation,” Compton said. “There was a catastrophic failure of the still, which caused the still to be catapulted through the building and into the gravel driveway of the facility. What exactly caused the still to overpressurize and fail, at this point, we don’t know; it’s still under investigation.”

[bellybuster]

instantaneous release of pressure on a boiling vessel is not a good thing. Instant shut down of energy input is a better option.

[badbird]

Cob is right, one layer of standard aluminium foil holds back a surprising amount of pressure.
I remember seeing posts about this subject on one of the non English forums, maybe HD.ru

I think after some tests the thin foil wraper from chocolate bars was found to be about right.

bb

[rad14701]

It was some years ago but "rupture discs" or "burst discs" have been discussed here... And, yes, standard aluminum foil has far too high of a rupture point... And when these are implemented, the rupture disc assembly must be configured so that the pressure released is vented either into a very large capture vessel or out of the building into the atmosphere in a safe location...

[shadylane]

I'm probably beginning to sound like a broken record.
A 3/4 inch 15 psi steam rated safety valve costs $20 and a manometer can be built for less than that.
I use both, $20 is cheap insurance, I don't want any drama when I'm running a still..
http://www.amazon.com/Apollo-Valve-13-5 ... B002KTZARW" onclick="window.open(this.href);return false;" rel="nofollow

[zach]

I would not worry about a boiler relief valve unless you have a way to isolate the boiler like a hand valve.

I've seen a few boilers on this site that use a keg boiler to steam mash that have an isolation valve on the output to the mash barrel.

An operator error (closed discharge valve) could cause an unsafe condition in this type of boiler.

1 kw (3,412 Btu/hr) of heat input to a boiler will vaporizer about 3.5 lbs an hour of steam.

I would pick a relief valve with the lowest set point I could find for a keg boiler. Like this one with a 15 psig set point.

http://www.grainger.com/product/AQUATRO ... alve-3ERJ6" onclick="window.open(this.href);return false;" rel="nofollow

At 15 psig this safety valve has a capacity of 37 lbs/ hour of steam. ( 130 series 1/4") see chart at:

http://www.aquatrol.com/pdf/Series130.pdf" onclick="window.open(this.href);return false;" rel="nofollow

At 15 psig, water requires 969 Btu/lbs to vaporize the water to steam.

The heat input this safety relief valve could remove from the boiler is:

37 lbs/hr steam x 969 Btu/lb = 38,853 Btu/hr = 10.5 KW boiler heat input.

So if you have a boiler under 10 kw, this safety relief valve will keep the pressure in the boiler under 15 psig.

The aluminum foil is likely useless as the burst pressure is way too high. The monometer is not a bad idea.

I would not use a safety valve in an application where material in the boiler could plug the safety valve- like a still.

[Brutal]

I'm probably beginning to sound like a broken record.
A 3/4 inch 15 psi steam rated safety valve costs $20 and a manometer can be built for less than that.
I use both, $20 is cheap insurance, I don't want any drama when I'm running a still..
http://www.amazon.com/Apollo-Valve-13-5 ... B002KTZARW" onclick="window.open(this.href);return false;" rel="nofollow

I was looking for a picture of your manometer a few weeks ago, and it looks like I found it. I just found this tab way in the back of my browser.

I wonder if anyone has tried to modify one of these pressure release valves for a lower pressure? Seems like if you could get the spring out you could just cut some coils off it to lower the pressure. I would like a 5-6 psi pressure valve.

[shadylane]

I haven't messed with the pressure relief yet, but I suspect the pin holding the lever can be pushed out and there's a threaded adjustment that sets the spring pressure. I'd prefer a relief pressure of 2 or 3 pounds

[Max_Vino]

I use two very simple pressure relief systems. For the boiler I have a stem. Liquid only escapes in a over pressure situation. For the condenser I place a stainless steel ball over an opening. Any buildup of pressure causes the ball to rattle. Simple.

Cheers,
Max