boiler explosion. what not to do.

[comstock-friend]

Nothing in the ASME Code (of 1974) shows copper plate as allowable in boiler construction, but copper tubes ARE allowed:

John

 

[Bentwings]

Source for this please, Dan.

The ASME Code (which our little boilers are generally and thankfully exempt from) cold water pressure test for fired boilers is 1.5 times Maximum Allowable Working Pressure (MAWP). On pressure vessels it is 1.5 times MAWP times ratio of material allowable stress cold divided by material allowable stress at operating temperature. For our boilers hopefully the ratio of allowable stresses is 1.

The ASME Code safety factor is 4:1. That is if say your steel boiler shell material has an allowable stress of 60,000 psi, you only get credit for 15,000 psi when performing your thickness calculations.

Testing above 1.5 times MAWP can cause permanent yield of some components. Steam testing at 1.5 times MAWP can kill you.

Under steam, maximum boiler pressure accumulation is no more than 6 percent above the highest pressure at which any valve is set, or no more than 6 percent above MAWP.

For those who want to wade deep in the weeds for safety and relief valves... https://admiralvalve.com/site/wp-content/uploads/2018/04/Tech-Reference.pdf

John

thanks for the info I stand corrected. I did contact local regulations but our stuff is too small to worry about unless abused. Fire box in homes might be frown upon. That’s why I’ve elected to go electric . Besides it’s “ green “LOL. HAHA . My ultimate test will not be air pressure hydraulic n a water tank it won’t explode maybe push the end cap out or pull screws out . I’m hoping to get this fluid dynamics program up and running so I’ll have additional data. It’s been a long time since I’ve used it . So I’m stumbling around .
Byron

 

[Steamchick]

Hi Richard. I have seen simple designs of water heater as a single coil of copper tube in the flue of the rocket stove.... As long as the water flow is pumped and controlled by output temperature - so the water doesn't boil - the articles all shout "success".
But in the UK we don't have free wood, just expensive gas.
K2

 

[HMEL]

As I'm on the road of building a boiler, I should ask this right now. If I completely rivet a boiler together and solder the seams with soft solder, it should be fine, right?
At the moment I do not have enough heat to properly solder a boiler of such size (3x7,8 inch, if I remember correctly). It's going to be fired with wood or charcoal, whatever I can get for a run.

The bushings could go pop though. Should I invest in another blowtorch and silver solder it or will soft solder do? I'm hoping to go up to 2 bar/29,4 PSI pressure with this boiler.

Wrong-- You need to put the rivets in the right spacing. If they are too close together or too close to the edge you weaken the metals holding strength . Maybe somebody on the forum can help you go that route. You are asking the right questions at the right time. Silver solder is the way I would go. Find a good heating and air conditioning guy who does that work to learn how to do it properly.

 

[Richard Hed]

Hi Richard. I have seen simple designs of water heater as a single coil of copper tube in the flue of the rocket stove.... As long as the water flow is pumped and controlled by output temperature - so the water doesn't boil - the articles all shout "success".
But in the UK we don't have free wood, just expensive gas.
K2

That has a lot to do with why I am doing all this. I thimpfks that with a steam engine that uses ANY kind of fuel, one can heat one's house, cook, and make eletricity and power. This includes hot water, of course, which we use for hot chocolatl, on cold days, and coffee or tea on regular days, or for washing and showers.

the present way expensive gas is used is a farce, travesty or even a conspiracy. Most of the heat goes up the chimney when virtually ALL the heat could be harvested. Look at it this way: it's a cold winter day, the stock are all dying from not being able to drink water because of the cold, the frozen water, the grass does not grow because of a natural disaster, or maybe a nuclear exchange that has brung on nuclear winter, the sky is black, and yet it is July. The neighbors have all killed each other and turned to canabalism--those that are left, that is. But you, You sit cozily in your basement with your rocket heater providing electric power, heat and light for your grow lamps which also provide heat. Once a day, you have to go out in the freeze to gather tree limbs, grass or buffalo chips, about 20 lbs.

Well, I doesn't thimpfk it would ever be that bad, but thimpfk for a moment about your expensive gas--it REALLY could do double or triple duty. the law of energy is that it can never be destroyed. It can disipate out thru the cracks of the doors and windows, but the only reason it is not used twice or thrice is because we don't design our homes or society for the best use of energy. Even electric energy created by the huge damns in the Soviet of Washington (The most dammed up river, apparently, in the world is the Columbia River), is greatly lost by leakage right into the air by the thousands of miles of electric lines. The best place to generate electric power is right in the home--that is, when it is winter. During the summer, it creates excess heat that has to be gotten rid of unless you use solar in some manner instead of burning some kind of combustible fuel.

PS, what articles?

 

[kaolsen1728]

I normally get involved with steel boilers and not copper ones. I will add that in the US, the ASME code now only tests boilers such as those used in model steam engines at 1 1/2 times the calculated operating pressure that the weakest component computes to. Also the maximum pressure at least in Washington State for copper boiler is 100 psi. However, if the weakest component computes to less than 100 psi, then that will be the allowable maximum pressure. Note also that the ASME maximum material stress factor for copper in the calculations is 5,500 MAS. Mild steel plate (A36) is 14,500. So do the calculations and also I agree that silver solder is a must.

 

[Richard Hed]

I normally get involved with steel boilers and not copper ones. I will add that in the US, the ASME code now only tests boilers such as those used in model steam engines at 1 1/2 times the calculated operating pressure that the weakest component computes to. Also the maximum pressure at least in Washington State for copper boiler is 100 psi. However, if the weakest component computes to less than 100 psi, then that will be the allowable maximum pressure. Note also that the ASME maximum material stress factor for copper in the calculations is 5,500 MAS. Mild steel plate (A36) is 14,500. So do the calculations and also I agree that silver solder is a must.

Do you actually make boilers? Have you got one to show? How do you fasten it? Do you weld it or silver solder? I intend to TIG one I have planned. I made a prototype, got it up to 100 psi, then eventually cut it into pieces. as I knew certain parts were inferioer. Also, I had stick welded it and could not get a leak out of it. The next one, will have very high quality parts, have the cuts, and chips done FAR better than before and the welds TIG.

 

[Steamchick]

Richard,
I just searched "rocket stove water heater" (years ago) but there are still lots of guys who stick a heat echanger in the flue of rocket stoves - often just a coil of copper pipe, with a large water tank at the end. They are all atmospheric boilers, NOT pressure boilers.
How to Build a Rocket Stove Mass Water Heater, with Geoff Lawton - Bing video

Brilliant DIY Off-Grid Water Heater Using a Rocket Stove – No Propane! - YouTube
Rocket Stove Water Heater III Build -PT1- - Bing video
and loads more...
K2

 

[Steamchick]

Hi,
I know a lot of you guys have a lot of experience with boilers. I have some too. But only making small boilers for boats and bench, but not locos. (e.g. 3" or 4" diameter up to 6" long). I have also repaired old boilers - that were good - and destroyed some BAD boilers. My bible was the K. N. Harris book of model boiler making.
In the UK, as long as you have "a design" and can satisfy the examiner it is a sensible design, you can hydraulically test the "new" (or re-commissioned) boiler at 2 x NWP, then steam test at 1.5NWP, and if satisfied, the tester will issue a certificate witnessing those tests. He isn't saying it is safe, just that he has not seen anything he thinks is unsafe. He also checks safety valve operation, fixtures and fittings and water feed equipment.
Now, as I browse the net to improve my work, I found an article by Kozo Hiraoke in Live Steam and Outdoor Railroading. This was his attempt to rationalise everyone's individual ideas on what the ASME regs tell you that you must do, and are a lot more up-to-date than the ideas of my revered Mr. Harris. I strongly urge you to buy a back copy of the magazine - to print it and publish here would infringe lots of copyrights, so I won't go there. (The editor would block it anyway!).
But it is very simple: You can make safe and reliable copper boilers within the ASME regs: But limited to Silver Soldered boilers at up to 100psi MAWP (with properly designed joints).
However:
A few points NOT covered by Kozo-San:

• The compressive strength of copper at around 400deg.F. - the temperature at steam pressure 100psi. - is only around 21% of the tensile strength. I have spent months searching for more information on the web, without success - to try and find how this should be applied to boilers we make for models. E.G. The flue tubes carrying hot gases through the boiler are in compression from the surrounding water + steam at pressure. Likewise fire-tubes in many commercial boilers and "amateur" boilers. And the "conventional" firebox in a cylindrical vertical boiler has the inner tube of the firebox in compression, from the water in the surrounding jacket. - SO it is necessary to do the sums (hoop stress) and make sure these items are thick enough for the stress - when also considering the clear directive from ASME that you must de-rate the permissible strength value with elevated temperature. This means that many of the designs of Mr Harris and others who designed boilers before the age of Regulations, are "no good" to the standards we live with today. But by increasing wall thicknesses we can make them OK.
• Similarly, my Engineering professional work (going back to the 1970s) meant I was also trying to understand how "ASME" an co. consider stress concentrations from "penetrations" in boiler shells when performing hoop stress calculations. My first move was my 1970s references - text books from 1930s - and simple diagrams and values of stress concentrations. This led me to SCF of 2.2 to 3.1 for various applications, until someone posted an ASME statement that "all penetrations shall be considered to have a stress concentration factor of 3.5". So that covers all the holes for bushes for safety valves, whistles, fire-holes to access fireboxes, Top -feeds for loco-boilers, etc. Yet I cannot find any reference in books by Mr. Harris et al to tell us the MODERN and Engineering approved (by ASME) method of doing designs with such penetrations.

So perhaps (like me until recently) these matters have been missed through simple ignorance "because we didn't know". Which is why I have had to de-rate some old boilers that were made to designs that do not meet a FOS of 8. (I am in the UK).
But I suggest we Engineers should do our research and find out "what we don't know" and need to know, so we can guide and advise the "Newbees" correctly.
My final point is that correctly designed and Engineered boilers in "whatever material" are safe. The calculations and Regulations are there to ensure that. Ignore them at your peril. Even if you don't think they apply to you. The laws of physics and Engineering don't know you are exempt.
Here endeth the lesson.
Sorry if I prattle-on a bit, now shoot me down.
K2

 

[Steamchick]

Hi K A Olsen, re: your comment of "the ASME maximum material stress factor for copper in the calculations is 5,500 Max Allowable Stress. ".
Kozo-San (in his published article, quoting ASME Table 1B of section II, part D) stated that ASME limit the tensile stress to 6700psi below 100deg.F: from which he goes on to follow how copper UTS changes with temperature and gets a value of MAS of 5400at 200deg.F. Certainly 5400psi is not right for pressure boilers, as the water has not even boiled at 200deg.F. To extrapolate further, Kozo-San has the MAS of 3142psi at 100psi. - This is the value I have been using for my boiler design calculations (hoop stress etc.
And for tubes in compression, the hoop stress is compared to a MAS of 660psi, due to the dramatic loss of strength in compression. (E.G. Flue tubes, fire tubes).
Notwithstanding, where there are "penetrations" the reinforcement (bush, plate, etc) must be capable of carrying the stress where there is no shell material, and the hoop stress calculations must use an SCF of 3.5.
Life just isn't simple, now.
K2

 

[TonySteamHobby]

Could you guys clear something up for me?
I have been soldering jewelry for about 40 years using “silver solder”.

I buy it in sheets at the following melting points;
Easy 1240F 671C
Med 1275F 691C
Hard 1365F 741C

Plumbers, “silver solder” melts around 420-460F 220-240C
electrical solder (60/40) melts around 370F 188C

Which kind of “hard” and “soft” solder are you referring to?

I have hard soldered large copper pieces (1365F) and it takes a lot of heat, flux and patience!

 

[TonySteamHobby]

On another note, I have a couple of Jensen boiler/steam engines. I have often wondered what is in them (type of boiler) and how they are manufactured.
Are these soldered?

 

[methuselah1]

Could you guys clear something up for me?
I have been soldering jewelry for about 40 years using “silver solder”.

I buy it in sheets at the following melting points;
Easy 1240F 671C
Med 1275F 691C
Hard 1365F 741C

Plumbers, “silver solder” melts around 420-460F 220-240C
electrical solder (60/40) melts around 370F 188C

Which kind of “hard” and “soft” solder are you referring to?

I have hard soldered large copper pieces (1365F) and it takes a lot of heat, flux and patience!

Soft solder always contains tin, usually with lead, though not always, and a whole range of other metals.

Silver soldering (brazing, hard soldering) employs a filler material that always comprises copper and zinc, and various other metals, notably silver. (I used to regard brazing as a distinct process to silver/hard soldering, but apparently modern nomenclature uses the term "brazing" for both.)

An obvious rule of thumb might be, if you can melt it with a soldering iron, it's soft, if you must use a torch, and have to get things red hot, it's hard.

 

[Steamchick]

Tony H. Hard solder is without tin and zinc. Usual melting point over 620C.
Soft solder contains tin, lead or bizmuth, so usually melts between 140c and 220C. Lead solders are also "soft" - but can go up to 330C - I think? But I'm not an expert, just picked up what I was taught 50 years ago.
Maybe the web has a more accurate answer?
Zinc based solders and aluminium solders are between those... not sure how they are defined?
K2

 

[Steamchick]

The Jensen boilers are of a type referred to as "kettles" - they are a simple tank placed over a flame. Possibly a higher temperature lead solder? but more probably a silver solder. (applied as a paste on assembly then the whole job passes through an oven cycle to melt and solder the joints.) They will have less than 15psi for the pressure relief valve to avoid the rules of the day! - but be certified as "domestic use". You can set fire to you house with the meths easier than blowing up one of these!
K2

 

[awake]

the present way expensive gas is used is a farce, travesty or even a conspiracy. Most of the heat goes up the chimney when virtually ALL the heat could be harvested.

My understanding is that some (many? most?) modern heating systems do indeed harvest the vast majority of the heat that would otherwise go up the chimney, with a resulting efficiency of up to 98.5% - only 1.5% of the heat value of the fuel is lost! Here's one of many articles that popped up in a search for "high efficiency gas furnace": High-efficiency furnace | Benefits and Value | Goodman

 

[Richard Hed]

Hi,
I know a lot of you guys have a lot of experience with boilers. I have some too. But only making small boilers for boats and bench, but not locos. (e.g. 3" or 4" diameter up to 6" long). I have also repaired old boilers - that were good - and destroyed some BAD boilers. My bible was the K. N. Harris book of model boiler making.
In the UK, as long as you have "a design" and can satisfy the examiner it is a sensible design, you can hydraulically test the "new" (or re-commissioned) boiler at 2 x NWP, then steam test at 1.5NWP, and if satisfied, the tester will issue a certificate witnessing those tests. He isn't saying it is safe, just that he has not seen anything he thinks is unsafe. He also checks safety valve operation, fixtures and fittings and water feed equipment.
Now, as I browse the net to improve my work, I found an article by Kozo Hiraoke in Live Steam and Outdoor Railroading. This was his attempt to rationalise everyone's individual ideas on what the ASME regs tell you that you must do, and are a lot more up-to-date than the ideas of my revered Mr. Harris. I strongly urge you to buy a back copy of the magazine - to print it and publish here would infringe lots of copyrights, so I won't go there. (The editor would block it anyway!).
But it is very simple: You can make safe and reliable copper boilers within the ASME regs: But limited to Silver Soldered boilers at up to 100psi MAWP (with properly designed joints).
However:
A few points NOT covered by Kozo-San:

• The compressive strength of copper at around 400deg.F. - the temperature at steam pressure 100psi. - is only around 21% of the tensile strength. I have spent months searching for more information on the web, without success - to try and find how this should be applied to boilers we make for models. E.G. The flue tubes carrying hot gases through the boiler are in compression from the surrounding water + steam at pressure. Likewise fire-tubes in many commercial boilers and "amateur" boilers. And the "conventional" firebox in a cylindrical vertical boiler has the inner tube of the firebox in compression, from the water in the surrounding jacket. - SO it is necessary to do the sums (hoop stress) and make sure these items are thick enough for the stress - when also considering the clear directive from ASME that you must de-rate the permissible strength value with elevated temperature. This means that many of the designs of Mr Harris and others who designed boilers before the age of Regulations, are "no good" to the standards we live with today. But by increasing wall thicknesses we can make them OK.
• Similarly, my Engineering professional work (going back to the 1970s) meant I was also trying to understand how "ASME" an co. consider stress concentrations from "penetrations" in boiler shells when performing hoop stress calculations. My first move was my 1970s references - text books from 1930s - and simple diagrams and values of stress concentrations. This led me to SCF of 2.2 to 3.1 for various applications, until someone posted an ASME statement that "all penetrations shall be considered to have a stress concentration factor of 3.5". So that covers all the holes for bushes for safety valves, whistles, fire-holes to access fireboxes, Top -feeds for loco-boilers, etc. Yet I cannot find any reference in books by Mr. Harris et al to tell us the MODERN and Engineering approved (by ASME) method of doing designs with such penetrations.

So perhaps (like me until recently) these matters have been missed through simple ignorance "because we didn't know". Which is why I have had to de-rate some old boilers that were made to designs that do not meet a FOS of 8. (I am in the UK).
But I suggest we Engineers should do our research and find out "what we don't know" and need to know, so we can guide and advise the "Newbees" correctly.
My final point is that correctly designed and Engineered boilers in "whatever material" are safe. The calculations and Regulations are there to ensure that. Ignore them at your peril. Even if you don't think they apply to you. The laws of physics and Engineering don't know you are exempt.
Here endeth the lesson.
Sorry if I prattle-on a bit, now shoot me down.
K2

Thanx yew for that. You made me realize that at any opening on a steel boiler that I should weld a ring around that opening. For instance at the opening where I put water view tubes, pressure guages and steam pressure blow-offs, I should weld a ring around those holes. I never considered that before.

As for your vid of the rocket stove, I have never seen tht particular one before, but I have seen many others. Since I started watching those, there have been many more posted. My design, however, is a bit different. The internal coil will be up farther in the chimney section. a regular boiler will be below. the two have different purposes. The boiler is for power and heating, the coil is for water heating only which is potable.

 

[Richard Hed]

My understanding is that some (many? most?) modern heating systems do indeed harvest the vast majority of the heat that would otherwise go up the chimney, with a resulting efficiency of up to 98.5% - only 1.5% of the heat value of the fuel is lost! Here's one of many articles that popped up in a search for "high efficiency gas furnace": High-efficiency furnace | Benefits and Value | Goodman

I noticed that that article said this:

Each gas furnace model has an energy efficiency rating in the form of a percent. This number is its Annual Fuel Utilization Efficiency (AFUE), or the ratio of annual heat output of the furnace compared to the amount of annual fuel energy it consumes. For example, if a furnace has an AFUE of 80%, it means 80% of the energy in the fossil fuel is being converted to heat while 20% escapes and is wasted

Notice that is says "80% of the energy in the fossil fuel is being converted to heat". This makes me wonder if they are saying 20% is not burned. That seems absurd, so I thinmpfks that they mean, 20% is not absorbed by the heat exchangers. This is not clear, and, being suspicious person, I always thimpfks that they are hiding something when such an error is made. In this case, however, I thimpfks that it is just a way to shorten the explanation--I hope.

 

[Bentwings]

I normally get involved with steel boilers and not copper ones. I will add that in the US, the ASME code now only tests boilers such as those used in model steam engines at 1 1/2 times the calculated operating pressure that the weakest component computes to. Also the maximum pressure at least in Washington State for copper boiler is 100 psi. However, if the weakest component computes to less than 100 psi, then that will be the allowable maximum pressure. Note also that the ASME maximum material stress factor for copper in the calculations is 5,500 MAS. Mild steel plate (A36) is 14,500. So do the calculations and also I agree that silver solder is a must.

I called our local inspection and they said it’s too small to inspect unless it’s a fired boiler in and BC loses space like garage. Then maybe building inspector might recommend some thing bottom line just follow the local specs as they apply scaling down as needed essentially if it’s ok for air compressor it’s ok for model steam. Certainly don’t go for super high temps or pressures. A model steam rail road that pulls people is a different story. I think these guys have some other specifications. We visited several places that have these set up in our streetrods. There seemed to be much more safety in place automatically just by common sense. These guys are very fussy how their RR works and operate. We were impressed.
otherwise you can spend hours calculating using Roarks engineering calculations. Some knowledge Of strength of materials is needed. The note above regarding placement of rivits is quite valid.
As former precision welder I can only say if you can’t produce a decent weld . Leave it to the experienced I did a lot of test welds in industry. Inspectors would come by and have you weld a test coupon representing current work. Better pass or it was off to be re taught and further testing
Byron

 

[Bentwings]

I called our local inspection and they said it’s too small to inspect unless it’s a fired boiler in and BC loses space like garage. Then maybe building inspector might recommend some thing bottom line just follow the local specs as they apply scaling down as needed essentially if it’s ok for air compressor it’s ok for model steam. Certainly don’t go for super high temps or pressures. A model steam rail road that pulls people is a different story. I think these guys have some other specifications. We visited several places that have these set up in our streetrods. There seemed to be much more safety in place automatically just by common sense. These guys are very fussy how their RR works and operate. We were impressed.
otherwise you can spend hours calculating using Roarks engineering calculations. Some knowledge Of strength of materials is needed. The note above regarding placement of rivits is quite valid.
As former precision welder I can only say if you can’t produce a decent weld . Leave it to the experienced I did a lot of test welds in industry. Inspectors would come by and have you weld a test coupon representing current work. Better pass or it was off to be re taught and further testing
Byron

It’s good to know that one has over designed something thanks I’m really new here so I appreciate any comments. I’m pretty excited as the engine kit is supposed to arrive Friday I just got the new boiler tube and gave my son he big chunk of aluminum to start making chips. The hardest part is not being able to dig in myself. I just spend money and gather parts. LOL I’ve yet to have a hobby that didn’t require this. Baseball it was hard to keep up with bat tech even wood bats are now super tech. Bam boo being the latest. Bam boo is an incredibly strong wood. Laminated with carbon fiber make a nearly un breakable bat. A $30 bat now costs $300. You need 3 of them . Why? You can only use one at a time? It’s come to. Need a base hit? Extra base hit? Or home run? Bat for each condition the issue is can you hit the ball in the first place ? Real good hitter has only 40% chance of A base hit let alone a long ball. We don’t get paid one dime to play senior ball . We bough our own equipment, including uniforms and yearly season charges. Almost as expensive as racing cars or building streetrods I’ve now got a whole season of steam toys already.
I feel for European fuel costs we think $ 4 gas is terrible it was effectively more than that 30 years ago when I visited Europe on business. Just having a car to get around was considered a luxury. I laughed at riding bikes everywhere was common. Guess what? Next summer I’ll be riding bike for shopping I can’t do on this keyboard. It won’t be funny at all I have a Streetrod but I’m not supposed to drive doc didn’t say anything about using bike. I’m just supposed to get daily exercise. Should I live to see another winter I just found studded bike tires even mini chains. Chains on a bike what’s this world coming to. ? Maybe I can use a drone for shopping. LOL

BYRON