RIMS Tube = Pipe bomb?

[Facinerous]

So I just built a RIMS tube for mash recirculation.

Put er to the test last night and it will raise 5 gal of cycled water 20 degrees f in about 15 min. It can maintain temperature in the cycled liquid with 3 minute bursts of heat to the tube.

Essentially, like all Rims tubes, its a 1500 watt heating element enclosed in a 1" copper pipe. I chose to use a 1" inner tube for the heating and a 1.25" outer copper pipe for the wort. The inner tube holds about one pint of liquid. The inner tube is 10 inches long, and the outer tube is about 16 inches long.

When the element turns on I can hear the water in the inner tube hiss. I know the element gets pretty darn hot, and the entire volume of liquid in the inner tube is not boiling. (At least I think I know that) What I am concerned with is the pressure that is developing within the inside tube.

If I were to have the heating element on for say 20 min, trying to step up a mash about 15 degrees the element would be on I'm thinking about 75 to 90 percent of the time. My intent is to run the pump cycling wort through the outer tube at about .25 gpm.

So my question, trying to have explained the details of the Rims tube. Is how much pressure would you think would be developed inside the tube running the element for 20 minutes with a cooler sourse (wort at about 150 degrees) leeching the heat from it.

I'm hoping that the typical answer would be below 300 psi. As I am fairly confident that the tube should be able to withstand that pressure. What I don't want is a potential pipe bomb sitting there while I am brewing away.

I intent to make an enclosure for this, but I have not done so as of yet.

Thanks for any input.

 

[GotPushrods]

You have a heating element in a fully sealed tube?!?!

 

[Facinerous]

Heck yes I do. Its awesome!!! Except for the potential bomb part. I turned it off after realizing my folly. Which is why I created this thread.

 

[TallDan]

Do you have pictures of this build? What is the point of having water in a fully sealed compartment with the element? This doesn't sound like any RIMS build I've seen anywhere else. I hope for your sake it's well thought out and safely designed.

 

[Facinerous]

Well, thats why I created this thread before I put it to a full test, trying to raise temperature any amount. Hoping that someone would tell me I am an idiot, or by helping reassure me that the pressure within the inner tube can withhold my demanding pressures.

I found through an engineers site that the boiling point of water at 100 psi, which is well within the coppers burst threshold is 328 degrees f.

I knew that pressure would build up within the inner tube, but I guess I just don't know how much.

(EDIT)
The actual heat exchanger is a manfactured product that I have repurposed as a rims tube. The pressure rating of the actual exchanger is 450 PSIG or 31 Bars. This should limit my weak points of the build to the end cap which is copper and the silver solder which I used.

 

[TallDan]

Well, based on what you're telling us here so far, i hate to say it, but it sounds like you're an idiot.

Yes, at 100psi, water will not boil until 328 degrees, but why on earth do you want want to create that pressure in the first place?

Can you post a link to the heat exchanger?

 

[Facinerous]

Here you go Dan. Just cause You asked.

I would take I am an idiot if you had founded supplemental information. Aside from that, thanks.

 

[GotPushrods]

The majority of people posting here at night are imbibing... You just have to let a few go here and there.

You're not an idiot, that's a fine piece of equipment. That being said, I think it is (very) dangerous and I would NOT use that as a RIMS tube.

But please don't seal shut a heating element.

With a PID and low watt density element you don't need to fear scorched wort. Just let it pass directly over the element.

 

[Facinerous]

No worries about the peanut gallery. I can let most comments like that float.

Thank for your reply PushRod. I was thinking about salvaging my creation with a pressure relief valve. Aside from that I was going to put the silly thing in an enclosure to isolate myself and others from potential harm.

The idea behind the sealed heating element was: For simplicity, and for increased temperature for faster heat exchange.

I'm going to go ahead an see if I can crunch a few numbers, though I am relatively uneducated involving thermodynamics, and see what I can expect involving worst case scenarios. I'll post what I find and see if someone more educated than I can fix the errors of my ways

 

[GotPushrods]

Yes a PRV at a minimum. It's what keeps a water heater safe.

Now I'm not outright disagreeing with the peanut gallery... I'm just being polite.

Water and electricity demand respect on their own. You add a pressurized metal tube and you are correct with the pipe bomb analogy. This thing could kill you. Dead. It's a cool idea, and I've done some dumb stuff in my life. But in my opinion, this just isn't worth it.

 

[Facinerous]

Oh no... You and the peanut gallery are right. After have doing some simple math the numbers are nuts. This is dangerous and I wouldn't recommend it to anyone. I'm going to leave this thread up as note for anyone looking into rims tubes involving what not to do.

1500 watt heating element produces 5118 btu/hr
There are 8 pints in a gallon
1 gallon of water is 8.34 pounds
1 pint of water is 1.034 pounds
5118 btu is 84 btu a min
1500 watts can heat 1 pint of water 84 degrees f a min
1500 watts can heat 1 pint of water 1680 degrees in 20 min

The laws of thermodynamics are beyond my understanding and well beyond my education. So this is some very simple math. I'm sure there are those who could get way more in depth with heating of fluid in an enclosed vessel, and heat loss dues to fluid passing in an outer jacket.

This bit of time I have taken proves that I am an idiot though :cross:

I'll be on the drawing board now.

 

[terodox]

Edited out.

 

[TXCrash]

A man was killed today while doing a dangerous new hobby experts are calling "home brewing". Police tell us that a new fad involves building a copper pipe bomb.

More details at 11.

 

[Bobby_M]

There's just no reason to isolate the wort from the element itself if you use a low watt density. Having the controller's temp probe inside the tube also keeps from overheating too much in the case of a flow issue. Keep in mind that putting a PRV on your pressure chamber is a minimum, but when it blows off, it's scalding steam too.

 

[horseinmay]

Did you build that thing, or find it somewhere? If you found it and are repurposing it, then maybe it was originally used with some kind of oil as the heat transfer fluid. The oil would probably not boil/burn at temperatures that it was being used at.
If you built that from scratch, I applaud your handiwork, but not your common sense. Build another one with the element exposed to the wort.
A PRV is not a good idea either, as it will let out steam at some pressure, and you'll eventually run the element dry.

 

[Stealthcruiser]

I would like to see it assembled.
You could mount it vertically,( element hanging down), and on the "sealed" chamber, tap off of it with a vertical column, upper end open to the atmosphere, and let that be your "expansion tank" for your heating medium.
I have a buddy who re-purposed a steam kettle, and he fills the jacket with water, fires the outer jacket with propane, and the water expands into an old water type fire extinguisher as his expansion tank,which is fitted with a "glass" sight glass to see his tank level.

He uses it to make 60 gallons of Brunswick stew at the time, with no scorching!

 

[Blitzkrieg]

Reminds me of that mythbusters episode where they took the PRV out of ordinary hot water tanks, when they popped they went clear through two floors and out the roof.

 

[Facinerous]

I never saw that mythbusters episode. I'll youtube it.

Through out the day I have been designing a revision to this while at work. Nothing is on paper yet but the concept is very similar to what Stealthcruiser is explaining. I like the idea of using an old fire extinguisher, I was just gonna goto the scrap yard and see what I could find.

Rather than have a closed vessel and a PRV, (which the more I thought about the less I liked) I will utilize a liquid reservoir in conjunction with my made heat exchange tube. It will no longer be sealed. I plan to drill a hole in the end with the pipe cap that will fit 3/8 NPS male fitting and silver solder in place. The fittings come with a flared section after the threads for tightening purposes so I plan to fit that from the inside of the tube threads out. Second hole will be drilled near the element side, same 3/8 nps fitting but threaded into the tube and soldered.

Then just run some 3/8 line to the reservoir, upper line from pipe cap to top of reservoir and lower line to the lower side of the reservoir. The tube will be vertical with the element down.

This should provide a cycling of the water from the tube to the reservoir much like a coffee maker which will help in maintaining levels and allow any boiled water to vent off through the reservoir.

If anyone was interested or sees any flaws in this idea let me know. I could post the design drawing if anyone is interested, and I will probably post a pic of the finished product which will be in a few days. Thanks for the help in this everyone. I appreciate it.

 

[The_Bishop]

It sounds as if you are over-complicating what should be a somewhat simple thing.

 

[Demon]

You are WAY over thinking this.

 

[heckels]

I find it somewhat amusing that your original post says that your RIMS tube is like any other with a sealed tube inside a tube yet none of us on the forum have ever seen anything like it.

I agree you're over complicating the concept. All you need is a 1-1.5" tube, a ULWD element and a temp probe (along with a couple fittings).

I applaud the ingenuity, but do yourself a favor in this case and use a proven method like Bobby's.

http://www.brewhardware.com/rimsherms-parts/169-newrims

Cheers!


Sent from my iPhone using Home Brew

 

[Facinerous]

Meh. Over complicating a simple thing is actually pretty fun to me. You are right. Why make something difficult when it can be simple. Simplest explanation is, I like geeking out on projects. I like to fail at something, figure out why. Then fix the problem.

My problem now is, I didn't account for pressure in an enclosed space. Thats my fault, but I have time and money invested in this little project and I have determined the cost of making a fix for what I have created should be cheeper than creating a new tube.

That and why not do it a little different? Advance in any industry is provided by doing things different. You win some you lose some.

 

[The_Bishop]

There's a difference between finding a new way to do a thing and finding a way to explode yourself.

In plain language, if you can't figure out that putting a heating element in water inside a sealed vessel is a horribly flawed and outright dangerous idea then you shouldn't be messing around with this stuff; you don't have the required skill set/knowledge to 'try new things' without hurting yourself/others. I'm not trying to insult you, I just don't want to see anyone get hurt. Your current approach of 'try and fail, then fix it' in this case could lead to missing fingers/hands/eyes, horrible steam burns, or even death.

 

[Facinerous]

I'm just going to have to go ahead a question in attempt to defend myself just a little bit.

I would simply like to ask you how many times you have done something in your life which after having done said thing you think to yourself? "Well that was stupid"

Essentially this is one of those moments for me. It happens. I'm not asking for a response to the question.

I guess I just chose to post about it which makes my folly more noticeable than most.

 

[Hamaki]

So my question, trying to have explained the details of the Rims tube. Is how much pressure would you think would be developed inside the tube running the element for 20 minutes with a cooler sourse (wort at about 150 degrees) leeching the heat from it.

I'm hoping that the typical answer would be below 300 psi. As I am fairly confident that the tube should be able to withstand that pressure. What I don't want is a potential pipe bomb sitting there while I am brewing away.

I intent to make an enclosure for this, but I have not done so as of yet.

Thanks for any input.

I think you were asking a question, but were looking for a mathematically supported answer rather than one based more on experiences, or lack thereof since this seems to be a new concept. It is probably dangerous enough that serious design before construction and use would be strongly advised. Maybe it won't explode, maybe it will just leak & ruin batch after batch before you recognize what's going on.

 

[Facinerous]

Hey... Thanks for bringing that up Hamaki. Although my build is changing due to the potential danger of using a sealed vessel with a heating element, I am actually still incredibly interested in my original question involving the PSI developed within the tube.

I did do the simple math involving heat generated by the element, but there are factors beyond my mathematical knowhow to develop an answer. There would be major heat dissipation involved within the tube but that is more than I know how to figure.

I would like to see this thread end up being somewhat informational and productive rather than continuously reiterating my design error.

 

[uatuba]

Hey...who doesn't like to brew at least 100 ft away from their mash tun, behind a sheet of Lexan?


Sent from my iPad using Home Brew

 

[TallDan]

I would like to see this thread end up being somewhat informational and productive rather than continuously reiterating my design error.

The primary problem you have here is that there is no apparent benefit to your design over the standard design that everyone uses. Why would anyone here be interested in a new design that is more complicated and dangerous than the generally accepted design? So this just makes it an academic effort...

...which brings us to the secondary problem. This is not a board of physicists and material scientists, it's a board of homebrewers. While there is a wealth of knowledge here about heating and cooling wort and the physical and electrical components involved, there would be very few here that have the knowledge and experience to tell you how to figure out exactly when your pipe bomb will explode. A large number of us can take a quick look and say that it's a bad idea and likely to explode, but exactly when would depend on how much power is supplied to the element, the thickness of the copper walls, the strength of your seals, temperature of wort, flow rate of wort, ambient temperature any many other factors that you have not and likely can not provide data on.

We're all about innovation and finding new and better ways to do things, that's why i clicked on this thread to begin with, but there are good ideas and bad ideas. Based on my limited knowledge of what is involved here, it's my strong, but uneducated, opinion that playing with high pressure steam with questionable vessel strength in a typical home environment is a very bad idea. Maybe I'm wrong, and before there is enough steam pressure to blow the cap off of your tube, the element will burn out because it's created enough steam around itself to insulate and overheat. That would be lucky to just destroy the element instead of doing that AND injuring yourself or others. And by the way, yes you will create steam starting at the boiling point of water because you sealed your tube somewhere near STP (Standard Temperature and Pressure). The pressure will not start to climb until you boil some water and create steam. That is of course, assuming you have distilled water in the tube and have managed to seal it without any air inside...

 

[horseinmay]

I would like to see this thread end up being somewhat informational and productive rather than continuously reiterating my design error.

If you want to take what you've already made, and turn it into something that will work, AND make it a novel idea just for kicks, try this:

What if it worked as a sort of steam injected RIMS tube? Instead of having the element in contact with the wort (standard) or having the element in a sealed fluid chamber (dangerous) make it so that the element is heating water for steam and injecting into the wort as it flows through a chamber. This would not really require building pressure, because the steam, as it condenses on contact with the wort, will give it plenty of heat energy. It can all be done at atmospheric pressure. You'll likely need a larger reservoir than just one pint.

Nobody wants to call you out for trying something new, just for accidentally creating something so dangerous. Every time a homebrewer himself up, it makes us all look bad.

 

[TallDan]

What if it worked as a sort of steam injected RIMS tube? Instead of having the element in contact with the wort (standard) or having the element in a sealed fluid chamber (dangerous) make it so that the element is heating water for steam and injecting into the wort as it flows through a chamber. This would not really require building pressure, because the steam, as it condenses on contact with the wort, will give it plenty of heat energy. It can all be done at atmospheric pressure. You'll likely need a larger reservoir than just one pint.

It's worth a shot since the OP has the hardware and the desire to try something new, but I suspect that the tube doesn't have the surface area needed to be effective at this. consider the large surface area that a HERMS tube has in a HLT, it's huge compared to what's here. The typical RIMS setup works with a small tube because the wort is directly in contact with the heating element, which is a very efficient design. I don't think a steam jacketed tube would be as efficient, but I could easily be proven wrong.

 

[horseinmay]

TallDan,

I don't mean steam jacketed, but actually using the pressure in the chamber with the element to inject steam into the wort as it flows through the rims. There is no need for surface area contact, just let the wort recirculate, and the steam will go into that stream and condense, releasing its heat energy. All he would have to do is puncture the pressure chamber and make some minor changes.

 

[sablesurfer]

Thank for your reply PushRod. I was thinking about salvaging my creation with a pressure relief valve. Aside from that I was going to put the silly thing in an enclosure to isolate myself and others from potential harm.

LOL...now I am envisioning the MythBusters trying to brew from behind their blast shield.

(HAHA...now that I have read whole thread, I am not the only one.)

Don't let the doubters get you down, I learned something from this and went, "oh yeah" while I was still trying to figure what you were attempting.

((As for a 'what the hell did I just do?!?!' moment in my life...at a backyard fireworks party with some SERIOUS planners, I put a random bottle rocket into a tube, lit it, launched it. ONLY THEN did I realize I had used a MORTAR tube from the FINALE portion of the night to launch my pissy little moon rocket from....to this day I think..."OMG"

 

[ajwillys]

I personally think this is a pretty decent idea but with a fatal flaw. No need to re-hash, it's been covered. I would just make a "stovepipe" type thing that sticks out vertically and attaches to the inner tube. You could use it to fill/empty the inner reservoir and would allow for the necessary expansion.

This is a HERMS not a RIMS. HERMS exchange the heat, RIMS immerse the heat. I had considered making something not totally different from this except it was more like a paint can with an element and a copper coil wound inside. It was open though, not closed.

 

[Hamaki]

I thought about the open ended idea too; safe but won't heat above 212 F at 1 atm so you'd need the surface area ajwillys describes for adequate heat transfer...essentially a herms design. If the inner chamber were filled with another fluid with an extremely high boiling point, like say mercury, now then you'd have something...probably brain damage or kidney failure.

Rims with ULWD element and a reliable pump should prevent scorched wort. Herms and an unreliable pump would not result in scorched wort. I don't know squat about steam injection but you can search steam infusion mash systems (SIMS) on this forum for more info.

 

[VladOfTrub]

A copper packless K wall, vapor to liquid heat X max working pressure on the shell is 650 pounds at 100F. The transfer side 400 pounds at 100F. In your Rube Goldberg design, the superheated water is sealed inside of a tube, inside another tube. If the inner tube ruptures, the release of energy into the wort side might rip the plastic transfer tubing you may be using, out of the kettle, spewing hot wort. The outer shell won't rupture. The open tubing becomes the relief device for the outer shell. The soft soldered joints or the fusite on the element will blow before the copper. If you used M wall, the copper may fracture, due to expansion/contraction of the thin wall. The element isn't designed to operate at superheated temps and high pressure. Superheat is the temp of a liquid above its boiling point. Water at 213F has one degree superheat. Superheat is part of a pressure thing. When superheated water changes state, kind of what would happen if a rupture occurs. A lot of energy is released. A BTU is 1 lb of water raised 1 degree, until the point of change of state.

You are right, we learn from mistakes. Only, if we survive. If we don't survive, others learn from the mistake.

 

[brew_ny]

You are right, we learn from mistakes. Only, if we survive. If we don't survive, others learn from the mistake.

truth to that

 

[bajaedition]

truth to that

Yeppers sure is

I think we can all look back at stupid mistakes we almost did not survive

but before you are old and wise you had to survive young and dumb

 

[VonRunkel]

Mechanical engineer here:

To mathematically/thermodynamically tell you why this is a bad idea we can assume the water inside the pressure vessel is ideal. And while it isn't exactly the right law to use, it will suffice to use the ideal gas law== PV=RT, with R being the universal gas constant.. essentially you can change any two of the three variables and it will fix the third.

In this case you have a fixed volume with a variable temperature, which will fix your pressure, BUT the temperature is changing so your pressure will change proportionally. This is where you may reach your pressure threshold and cause an explosion.

My solution would be to install a reservoir vented on one side of the pressure chamber and a U vent (to collect condensate) on the other. The trick would be to keep the reservoir full of water and at the same level as the U seal. This way the water level would be in equilibrium (something about fluid hydraulics and Pascal's law) and as the heater boiled off water you would be able to ensure that the heater was still covered.

Other people might have better ideas, but this will reduce the impending explosion probability.

 

[Hamaki]

Mechanical engineer here:

To mathematically/thermodynamically tell you why this is a bad idea we can assume the water inside the pressure vessel is ideal. And while it isn't exactly the right law to use, it will suffice to use the ideal gas law== PV=RT, with R being the universal gas constant.. essentially you can change any two of the three variables and it will fix the third.

In this case you have a fixed volume with a variable temperature, which will fix your pressure, BUT the temperature is changing so your pressure will change proportionally. This is where you may reach your pressure threshold and cause an explosion.

My solution would be to install a reservoir vented on one side of the pressure chamber and a U vent (to collect condensate) on the other. The trick would be to keep the reservoir full of water and at the same level as the U seal. This way the water level would be in equilibrium (something about fluid hydraulics and Pascal's law) and as the heater boiled off water you would be able to ensure that the heater was still covered.

Other people might have better ideas, but this will reduce the impending explosion probability.

As mentioned earlier, this approach would be safe but with water as the heat transfer fluid in the inner chamber temps would reach no more than 212F at one atmosphere. This does not allow much delta T to affect wort temp. For this concept to work safely there would need to be a heat transfer medium with a much higher boiling point at one atmosphere or a safe method of holding a higher pressure on the water to raise boiling temp appreciably. If a pressure release & water are used I would assume that there is some risk of boiling off enough water that part of the element would be exposed. Although I've heard some claims about ULWD elements being able to withstand dry firing, I'm not sure how long or how frequently this can be done without damaging or destroying the element. Though a method might be devised to maintain a high liquid volume in a pressurized inner chamber to keep the element immersed I suspect it would be beyond the means or ambition of most home brewers.

 

[Facinerous]

Thanks for all the responses everyone. You have all help me find a solution to my stupidity. With respect to ambition I would like to toot my own horn by saying there is no lack of. Ajwillys is right in that this is technically a HERMS, not RIMS, concept.

I have been delving into the wonderful world of thermodynamics, and all of its awesome confusing ways. Its actually not to bad, but including time in the equation has got me stumped at the moment. This is mainly to determine temperature change of wort entering the the heat exchanger and heat of wort exiting the heat exchanger with known temperatures.

I agree that using an open vessel would be the safest means of utilizing what I have created. I need to prove that this would be adequate though before I commit to a final design. The temperature difference may not be enough to raise the wort temperature any appreciable amount in order to provide the ability to use a step mash process. I believe that it would be adequate in maintaining temperature though.

This is all with regard to post #18 in this thread in which I explain a design concept to alleviate my original design flaws.

I have a tertiary design worked out in my head which would allow for pressure to be developed within a closed heated system with the appropriate safety features incorporated. Before I decide on which system I ultimately use I need to rough out the math first though.