Stainless steel boiler

[86turbodsl]

That ought to be enough of a subject to get some attention...


Hello, I just joined. I thought this might be a good venue to ask a question or two.
I'll start off by saying I'm new here, but not to forums. Please be gentle. I'm going to ask a few controversial questions.
I am not trolling. I'm serious.

I'm a mechanical engineer, working in internal combustion engine design for one of the automotive oems. My background is
in heat transfer and base engine design, not steam. But i have an application that i want to discuss.

I'm not into steam engines, although i think they are neat. One of my other hobbies is homebrewing beer. As a result of that hobby,
there is a process i'd like to add to my brewing that involves generating a fair amount of steam. Steam because it's gentler on the
beer during the brew process.

Now that's out of the way, let me ask my question.
I want to build a stainless steel boiler. I know before anyone says it, that stainless is a very poor choice. I'm aware of the stress corrosion issues with stainless austenitic series steels with this application. However, I need very very clean steam. I'm injecting it right into a food/drink. I am very worried about rusting over time causing issues with quality. Now let me clarify my operating point. I am planning to run this boiler at about 10-15 psi / 240-250F, pretty low pressure. It's mainly about getting the correct temp into the product. less than 212F, no heat moves. Over 250ish, you burn the product.

I wanted to build this boiler out of a 1/4 barrel beer keg, which is comprised of the following:
14 gauge stainless (approximately 0.0751" thickness, 304 series)
Approximate diameter 16"

Running the pressure vessel calcs on it:

85,000 psi * 0.0751 / 8" radius = about 800 psi burst.

Give it a 10X safety factor, i'm at about 80psi safe operating pressure.

Run it at 10-15 psi, i'm at about 50X safety factor.

So the final question, IS THIS SAFE with proper boiler inspection/maintenance? IE, i plan to have a pressure relief, water level indicator, low water cutoff, and it will be electric element fired through a controller. It will only be fired on a brew day. The rest of the time, it will sit with water in it.

And that's my summary. Am i crazy?

[SP&S700]

86 turbo diesel
What make is the turbo? and welcome from me any way. I love reading the replies on the SS boiler stuff, its great fun. My only comment would be the size. Here at the LC Oregon boiler code last time I checked was below 12" diameter inside diameter. Larger than that it should be a certified boiler maker. 100 psi operating pressure. There I believe is a cubic foot or inch regulation in Oregon too. As I recall even if you built a 1 1/2 NP Yellowstone 2-8-8-4 the boiler volume would be below that. Most states have some type of size limit to the hobby boiler, check your area. As far as I'm concerned SS should be fine for hobby use, have I built one no. Your question should spark a lot of you can't do that and its dangerous replies. I would just check the steam industry for their SS specs on Heat exchangers and flange grade SS for firebox material. There are some hear sho use SS flues and time has proven them to be very viable. You can also search SS and see the relies from the past.

Have fun

Clint

[EnidPuceflange]

Yep, this should run and run

Just some random thoughts -

If cleanliness and lack of contamination is a big issue, I'd be trying to remove the heating element outside the vessel.
How much steam do you need? How many heating elements are you planning to use?
How good are you at welding and working with stainless? Personally I'm OK with regular steel, but sanitary welding and so on (which I think is what you'd need) would make ME pause and try to find another way.

Based on the stainless beer kegs I've seen, 800 psi burst seems at least an order of magnitude too high to me. They aren't a single piece - they are a composite, with seams and ends welded on, with fittings, and they are intended to operate at perhaps 20psi at most. I'd be very surprised if in good condition they would take much more than 100psi without coming apart quite rapidly.

If it were me, I think I'd strongly consider something like this: http://www.mrsteam.com/generators

Just my $0.02.....

[ken572]

That ought to be enough of a subject to get some attention...


Hello, I just joined. I thought this might be a good venue to ask a question or two.
I'll start off by saying I'm new here, but not to forums. Please be gentle. I'm going to ask a few controversial questions.
I am not trolling. I'm serious.

I'm a mechanical engineer, working in internal combustion engine design for one of the automotive oems. My background is
in heat transfer and base engine design, not steam. But i have an application that i want to discuss.

I'm not into steam engines, although i think they are neat. One of my other hobbies is homebrewing beer. As a result of that hobby,
there is a process i'd like to add to my brewing that involves generating a fair amount of steam. Steam because it's gentler on the
beer during the brew process.

Now that's out of the way, let me ask my question.
I want to build a stainless steel boiler. I know before anyone says it, that stainless is a very poor choice. I'm aware of the stress corrosion issues with stainless austenitic series steels with this application. However, I need very very clean steam. I'm injecting it right into a food/drink. I am very worried about rusting over time causing issues with quality. Now let me clarify my operating point. I am planning to run this boiler at about 10-15 psi / 240-250F, pretty low pressure. It's mainly about getting the correct temp into the product. less than 212F, no heat moves. Over 250ish, you burn the product.

I wanted to build this boiler out of a 1/4 barrel beer keg, which is comprised of the following:
14 gauge stainless (approximately 0.0751" thickness, 304 series)
Approximate diameter 16"

Running the pressure vessel calcs on it:

85,000 psi * 0.0751 / 8" radius = about 800 psi burst.

Give it a 10X safety factor, i'm at about 80psi safe operating pressure.

Run it at 10-15 psi, i'm at about 50X safety factor.

So the final question, IS THIS SAFE with proper boiler inspection/maintenance? IE, i plan to have a pressure relief, water level indicator, low water cutoff, and it will be electric element fired through a controller. It will only be fired on a brew day. The rest of the time, it will sit with water in it.

And that's my summary. Am i crazy?

Hello 86turbodsl

Welcome to The Home Machinist!

1) Check with your State Boiler Inspector
for his advice on your design idea's and
methods.
2) Use 316 Food Grade Stainless Steel.
Passivate all your welds inside and out.
You don't want to get your party guests
sick from your beer.
3) Make sure you get it inspected so you
can get your Pressure Vessel (Boiler)
certified, so your Home owners Insurance
will cover you if you have a problem.
4) That should get you on the right track.

As you have found out, we have members
that really enjoy helping each other, and
sharing there skill’s and or knowledge,as
well as there project’s, idea’s, and more.

In order for this to happen smoothly there
are a few things that are NEEDED:

1)Correct brand names of what ever
you are asking and/or talking about.

2)Correct Serial numbers, Model No,
Date, and or Country of Manufacturer,
Size’s, Colors, Clear Picture’s of the item,
and or it’s data plates, and anything else
you can supply for the members to work
with.

3)Do you already have, or need
Operator and Parts, Manual’s

4) Making sure that you put your
WORLDLY LOCATION in your
PROFILE so it show’s up to the left
of all of your POST’S under your name.
VERY HELPFUL, to member’s trying
to assist you.

5) It is always nice to THANK the members
that spend time HELPING YOU and when
your problem is solved, it’s nice to UPDATE
and share your FIX / REMEDY to help the
next member, to read and learn from.

NOTE: CLEAR PICTURE’S
(ARE ALWAYS)
VERY HELPFUL.

Ken.

[redneckalbertan]

Check with boiler code but as far as I know anything less than 15 psi is not considered a pressure vessel. So you shouldn't have to have it certified with ABSA... But I'm just a welder, and can't quote boiler code. Depending on joint design you are likely to be TIG welding it. Get a good welder to do it. Stainless is different than steel to weld, watching your heat input is very important.

There are several threads on the site here dealing with stainless boilers for scale locomotives, they may contain some helpful information to you. But if they don't, they will open your eyes to the hints that have been given in the previous reply to stainless boilers opening drum (not cans, drums) of worms!

There are lots of food grade and stainless pressure piping out there so I think it's just a question of how not can it be done.

[86turbodsl]

86 turbo diesel
What make is the turbo? and welcome from me any way. I love reading the replies on the SS boiler stuff, its great fun. My only comment would be the size. Here at the LC Oregon boiler code last time I checked was below 12" diameter inside diameter. Larger than that it should be a certified boiler maker. 100 psi operating pressure. There I believe is a cubic foot or inch regulation in Oregon too. As I recall even if you built a 1 1/2 NP Yellowstone 2-8-8-4 the boiler volume would be below that. Most states have some type of size limit to the hobby boiler, check your area. As far as I'm concerned SS should be fine for hobby use, have I built one no. Your question should spark a lot of you can't do that and its dangerous replies. I would just check the steam industry for their SS specs on Heat exchangers and flange grade SS for firebox material. There are some hear sho use SS flues and time has proven them to be very viable. You can also search SS and see the relies from the past.

Have fun

Clint

Thanks Clint,

I picked my username from my 1986 Ford F250 6.9 diesel with an ATS turbo. Beast of a truck.
I think there's no high temps involved here really, as this is planned to be an electric element.

[86turbodsl]

Yep, this should run and run

If cleanliness and lack of contamination is a big issue, I'd be trying to remove the heating element outside the vessel.
How much steam do you need? How many heating elements are you planning to use?
How good are you at welding and working with stainless? Personally I'm OK with regular steel, but sanitary welding and so on (which I think is what you'd need) would make ME pause and try to find another way.

Based on the stainless beer kegs I've seen, 800 psi burst seems at least an order of magnitude too high to me. They aren't a single piece - they are a composite, with seams and ends welded on, with fittings, and they are intended to operate at perhaps 20psi at most. I'd be very surprised if in good condition they would take much more than 100psi without coming apart quite rapidly.

If it were me, I think I'd strongly consider something like this: http://www.mrsteam.com/generators

Just my $0.02.....

Hello, i can get stainless heating elements. Not a big deal. I think one 5500W heating element should do it. I haven't worked out the steam calculations yet, i have seen others doing this using similar devices, one of two ways, either a flash boiler, or a stainless container with an element. I actually want to take the time to engineer it. Nobody has used a keg yet though to my knowledge.

I've heard that kegs may hold up to about 600 psi. They are rated operating pressure at 60psi. But that's cold too. I don't think that steam generator would supply pressurized steam. likely it would make atmospheric steam. I need pressure to move the steam.

As far as the fabrication, i have not welded stainless, but do weld a lot at home. I have access to a very good stainless weldor at work, he's done lots. We have a Miller Dynasty 350 on order to replace the giant Lincoln TIG. I suppose i could stick at home too. I have a very big Miller stick. I do have some MIG stainless wire around too, but have not used it. My mig is an old Miller feeder on a CV power supply.

[86turbodsl]

1) Check with your State Boiler Inspector
for his advice on your design idea's and
methods.
2) Use 316 Food Grade Stainless Steel.
Passivate all your welds inside and out.
You don't want to get your party guests
sick from your beer.
3) Make sure you get it inspected so you
can get your Pressure Vessel (Boiler)
certified, so your Home owners Insurance
will cover you if you have a problem.
4) That should get you on the right track.

Ken.

Thank you Ken. I am not sure after reading the responses if this falls into a true pressure vessel area? 10psi is probably where i'd run it. Just enough to get the temp up to 240ish and move the steam into the beer for heating. Would this project require inspection? I have not heard of anyone doing this in other states being inspected, although i suppose laws are different in every state.

[86turbodsl]

Just so everyone knows where this idea started, here's an example of a steam boiler made from a stainless cornelius keg. While i dont think i'd want this form factor, it's the right idea. I would have all welded fittings and probably no clean out as shown here. Corny kegs are rated at 150 psi.

http://www.homebrewtalk.com/f253/diy-st ... uri-27070/

[EnidPuceflange]

Just so I'm clear what you're doing (I too brew, so I'm curious ) - you're using this to step mash, right? For non-brewers, this is the process where the grain is heated to a very specific temperature in water (it looks a lot like oatmeal) and the steam (if I understand correctly) is being used to raise the temperature of the mix by specific steps.

If that's the case, then you don't care about sterility - it'll be boiled afterwards anyway - but you want a lot of steam on demand, and the ability to shut it off and turn it on (which might cause some issues here).

Of course I could be totally wrong on this, like so much else

[RET]

Hi,

I'm sorry, but 10 psi. isn't going to give you what you want. Water boils at 212 degrees F at sea level. If you want to raise the temperature to 240 degrees F, you will need a pressure of 240-212 or 28 psi., since for the first 100 psi. of steam pressure, the steam temperature rises by 100 degrees Fahrenheit. I'm not sure what happens after that, but for the first 100 psi., the pressure/temperature curve is linear (or close to it) at 1 psi. per degree Fahrenheit.

The 10 - 15 psi range is about what you would see in a pressure cooker (1 atmosphere), but 30 psi. would give you quite a bit more stored energy and when misused, even pressure cookers can fail quite spectacularly. I'm not saying, "don't do it;" I guess what I am saying is that it does require a lot of thought to come up with a safe, workable solution. Probably some form of periodic hydrostatic testing at multiple times working pressure should be incorporated in the plan to be on the safe side.

You should also have at least two safety valves (required on our steam locomotives) in case one fails and also some form of pressure switch or sensor that would cut off the power to the heater if it goes over the normal operating temperature.

Just my ideas, I'm sure others will have more.

Richard Trounce.

[hammermill]

some thoughts. many comerical steam kettles as used in restaurants are in essence what you are talking about. one stainless element like you mention can also be found in dishwashers and in the surplus world at one time I thing surplus sales has them.

as you may know many a piece of brewing equipment has been ruined by someone leaving water with a chlorine concentration in it stand . a whole new brew pub suffered this fate a few years back.