boiler explosion. what not to do.

[Richard Hed]

Bentwings , I think you need to check some of your facts re boiler pressure testing .
Model boilers should pass a hydraulic test at TWICE the working pressure which should hold steady for 10 minutes.
A steam test should follow at one and a half times the intended maximum working oressure .
Soft solder is quite good enough for low pressure boilers , Mamod have been soft soldering their boilers for at least 50 years.
Dan.

Are you sure about the pressure of steam only being tested a 1.5X? Each state has their own rules. Where do you live?

 

[methuselah1]

Like Dan said! But you can bet your boots that the solder is carefully selected- there are many different flavours from the classic 60/40 tinman's solder to the domestic plumbing stuff which is 99% tin, with the remainder of copper - and everything in between.

I watched the video, and it's hardly surprising there was an explosion, firing a boiler like that with a propane/butane torch like that! Toy engines are spirit fired, which is far more gentle. That doesn't mean they are bulletproof; schools in the UK used to have at least one Mamod to allow physics teachers to demonstrate the principles. A few years ago a teacher was killed, and students injured when one blew. Should have checked the safety valve.

Full sized engines, like locos, have a "fusible plug" of lead positioned in the crown of the firebox, so if the water level becomes too low the lead melts, the steam pressure is relieved and the fire is extinguished. needless to say that dropping a plug is a source of unspeakable shame for any driver.

That plug has flames licking around it for the whole rest of the time, and is safe.

But I digress. To summarise, for low pressure boilers, in order of integrity-

Fully soft soldered (with an appropriate solder)

Fully soft soldered, with stays.

Fully soft soldered with rivets.

Fully soft soldered with rivets and stays (we're going over the top now- kinda depends on the size)

All the of the above using silver solder instead. More expensive, but it won't break the bank. The boiler won't blow your b*ll*cks off as easily, which might only happen once, and after which, silver solder would seem to be downright bloody cheap.

-Andrew UK

 

[Bentwings]

Thanks for additional info I was probably going off what I was previously told . This eases the requirements some I’m more concerned with leaks due to aluminum dimensional changes when heated.. I would have done more traditional copper but large diameter is jut not available here. Not to note that copper has become extremely expensive. I considered Tig welding but my vision just prevents precision welding I used to do . I’ve added a double seal on both ends as well as tie bar between end caps. There are some attractive aluminum boilers but they are flame heated and I simply cannot have that in my home I have nat gas heat but that’s not an option at all. I doubt I’ll need more than 50 psi but I’ll know more once I test the engine on compressed air. It’s supposed to run on just 20 but by calculation that’s not much torque on the crankshaft even with 4 double acting cyl. I have enough to do now so while I’d like to have some kind of dyno but I’ve got a great variety of driven features in the works. Post pictures when things start to come together . Chip making should start in a couple days . My son and grand son are helping in they shop . It’s really a treat for me to have them both . I just was given a tip about insulation of the boiler as aluminum will bee a terrible emitter of its heat. I had planned on using automotive exhaust wrap which I used on my street rods it’s pretty in expensive and can with stand glowing red heat. .I wondered ashy boiler of old had wood wrapped around them. Since I won’t have open flame I’ll use molded wood . I have almost unlimited supply of various woods plus I’d like a polished stainless wrap for appearance. I’ll monitor operating temps right from the start. I was going to use stainless to Star with but it too has risen in price. I used to do semi tank truck pressure vihicle repair so I had experience welding stainless pressure vessels . Plus I designed some military stainless battery pressure vessels in industry. I still have welding equipment I’m just not able to do the stuff now . Like “ Dirty Harry movies says” you have to know your limitations .
It’s hard becoming old LOL

I APPRECIATE ANY COMMENTS. I’m finding my mistake in not doing electrical engineers in parallel with mech eng. I now have to depend on others compete in this area. I’m always open to new things do I’m adding some ew thoughts to this hobby . I just was directed how to add a ew larger monitor to my laptop. I just happen to have a near ew one so it’s now n he table. Nw I just need to take advantage of I t maybe I can dispense with hunt and peck on this iPhone I see two of each letter so it’s like constant target practice Well I just heard Amazon so I’ll see what arrived

byron

 

[Richard Hed]

Thanks for additional info I was probably going off what I was previously told . This eases the requirements some I’m more concerned with leaks due to aluminum dimensional changes when heated.. I would have done more traditional copper but large diameter is jut not available here. Not to note that copper has become extremely expensive. I considered Tig welding but my vision just prevents precision welding I used to do . I’ve added a double seal on both ends as well as tie bar between end caps. There are some attractive aluminum boilers but they are flame heated and I simply cannot have that in my home I have nat gas heat but that’s not an option at all. I doubt I’ll need more than 50 psi but I’ll know more once I test the engine on compressed air. It’s supposed to run on just 20 but by calculation that’s not much torque on the crankshaft even with 4 double acting cyl. I have enough to do now so while I’d like to have some kind of dyno but I’ve got a great variety of driven features in the works. Post pictures when things start to come together . Chip making should start in a couple days . My son and grand son are helping in they shop . It’s really a treat for me to have them both . I just was given a tip about insulation of the boiler as aluminum will bee a terrible emitter of its heat. I had planned on using automotive exhaust wrap which I used on my street rods it’s pretty in expensive and can with stand glowing red heat. .I wondered ashy boiler of old had wood wrapped around them. Since I won’t have open flame I’ll use molded wood . I have almost unlimited supply of various woods plus I’d like a polished stainless wrap for appearance. I’ll monitor operating temps right from the start. I was going to use stainless to Star with but it too has risen in price. I used to do semi tank truck pressure vihicle repair so I had experience welding stainless pressure vessels . Plus I designed some military stainless battery pressure vessels in industry. I still have welding equipment I’m just not able to do the stuff now . Like “ Dirty Harry movies says” you have to know your limitations .
It’s hard becoming old LOL

I APPRECIATE ANY COMMENTS. I’m finding my mistake in not doing electrical engineers in parallel with mech eng. I now have to depend on others compete in this area. I’m always open to new things do I’m adding some ew thoughts to this hobby . I just was directed how to add a ew larger monitor to my laptop. I just happen to have a near ew one so it’s now n he table. Nw I just need to take advantage of I t maybe I can dispense with hunt and peck on this iPhone I see two of each letter so it’s like constant target practice Well I just heard Amazon so I’ll see what arrived

byron

Hey Bent, could you please insert more white space in your comments. You are giving ME double vision. Thanx

How many years did you do TIG? What did you make?

 

[Bentwings]

Hey Bent, could you please insert more white space in your comments. You are giving ME double vision. Thanx

How many years did you do TIG? What did you make?

pin taken I’ll use the space and return more. I really made a mess in the last post the spell check does updates even after I’ve already done them so I had to apologize for things that get out of context . I’ve had some retry rough injuries in sports over the years but this one is med and not healable or fixable. It’s frustrating

I tried he dictating thing but that even worse

gotta go . More thinking to do before daily exercise . Thanks again for the tip

byron

 

[Bentwings]

pin taken I’ll use the space and return more. I really made a mess in the last post the spell check does updates even after I’ve already done them so I had to apologize for things that get out of context . I’ve had some retry rough injuries in sports over the years but this one is med and not healable or fixable. It’s frustrating

I tried he dictating thing but that even worse

gotta go . More thinking to do before daily exercise . Thanks again for the tip

byron

Well as Simone suggested, I looked up boiler specs for the area or state in this case

turns out that by not using fuel or burner
I’m well within requirements . This boiler is just too small to fall into inspections. As long as I don’t manufacture them or sell them I’m ok .
next, if I stay under 300 degF and about 150 psi again not a problem . I don’t have to deal with structure issues as I won’t be modifying my home or garage. There won’t be any flammable materials even in the same room be it my hobby room or kitchen table. Even my wattage is far below any concern . It will have safety valve and peer timer cut off . Boiler level gage needs to be up higher to read actual level so that about the only change I need So electric heat was a wise choice for me I’m glad I did not choose to weld as technically. It might have had to be inspected. Or provided welt coupon or some kind of certification Most of the specs deal with commercial or home heating . So I’m completely out of the loop there all of my planned lumping is well within specifications I’m glad someone suggested I look this stuff up. Thank you I’ve started a note book entering my hoop stress numbers bolt and screw numbers fitting and hose specs or where to find them . I had note but spilled a full glass of hot water over them so I’m re constructing them now . There is a lot of monkey business, that we take for granted starting a new hobby .. I did a lot of this when I went to giant scale Rc airplanes. My big Zcorsair flew for 13 years with out structural failure even surviving some rough landings . My log book was over 2” thick not counting the build book . I’ll ad a section in my current note book for testing things and results I’m curious to see how the turbines respond to engine exhaust. There was a note. About a condenser which I’m working on now . Gathering information on how they work . That will be a test area as I know little about them. I have my own ideas that seem to vaguely
Follow what the specs noted . Again this is too small stuff to even get them to listen on the phone . It’s not like I’m contaminating ground water or the area.
I have to order the 1/4 x 40 ME tap and die . $ 50 for a tiny tap and die it will probably another $10 for postage

I also found 1/16” NPT. Pipe tap and die. I’m not even sure I could use these as I may have to make adaptors for 1/8 NPT to those too. Once I get the basic boiler parts I’ll decide on fitting size and location

byron

 

[Richard Hed]

Hey Bent, could you please insert more white space in your comments. You are giving ME double vision. Thanx

Well as Simone suggested, I looked up boiler specs for the area or state in this case

turns out that by not using fuel or burner
I’m well within requirements . This boiler is just too small to fall into inspections. As long as I don’t manufacture them or sell them I’m ok .
next, if I stay under 300 degF and about 150 psi again not a problem . I don’t have to deal with structure issues as I won’t be modifying my home or garage. There won’t be any flammable materials even in the same room be it my hobby room or kitchen table. Even my wattage is far below any concern . It will have safety valve and peer timer cut off . Boiler level gage needs to be up higher to read actual level so that about the only change I need So electric heat was a wise choice for me I’m glad I did not choose to weld as technically. It might have had to be inspected. Or provided welt coupon or some kind of certification Most of the specs deal with commercial or home heating . So I’m completely out of the loop there all of my planned lumping is well within specifications I’m glad someone suggested I look this stuff up. Thank you I’ve started a note book entering my hoop stress numbers bolt and screw numbers fitting and hose specs or where to find them . I had note but spilled a full glass of hot water over them so I’m re constructing them now . There is a lot of monkey business, that we take for granted starting a new hobby .. I did a lot of this when I went to giant scale Rc airplanes. My big Zcorsair flew for 13 years with out structural failure even surviving some rough landings . My log book was over 2” thick not counting the build book . I’ll ad a section in my current note book for testing things and results I’m curious to see how the turbines respond to engine exhaust. There was a note. About a condenser which I’m working on now . Gathering information on how they work . That will be a test area as I know little about them. I have my own ideas that seem to vaguely
Follow what the specs noted . Again this is too small stuff to even get them to listen on the phone . It’s not like I’m contaminating ground water or the area.
I have to order the 1/4 x 40 ME tap and die . $ 50 for a tiny tap and die it will probably another $10 for postage

I also found 1/16” NPT. Pipe tap and die. I’m not even sure I could use these as I may have to make adaptors for 1/8 NPT to those too. Once I get the basic boiler parts I’ll decide on fitting size and location

byron

Hey Byron, Where's the white space. White space makes it immensely easier to read. Thanx

 

[Bentwings]

Hey Byron, Where's the white space. White space makes it immensely easier to read. Thanx

I did space this all out what I thought would be much more open but in reading your post I see all extra spaces have disappeared thanks sell check I really did spend a bunch of time opening the message up as you suggested I even reviewed it before I posted. I’ll try again
and see if I can get around
this compression.
I’ve not noticed this before I’ll also check some other sites I visit to see if it is there
too. I’ ll review when

I go to respond but I just didn’t notice this event . I’m really sorry. I seem to have too many words as it Is . I did spread this out seems ok now preview looks ok so far

Byron

 

[Richard Hed]

I did space this all out what I thought would be much more open but in reading your post I see all extra spaces have disappeared thanks sell check I really did spend a bunch of time opening the message up as you suggested I even reviewed it before I posted. I’ll try again
and see if I can get around
this compression.
I’ve not noticed this before I’ll also check some other sites I visit to see if it is there
too. I’ ll review when

I go to respond but I just didn’t notice this event . I’m really sorry. I seem to have too many words as it Is . I did spread this out seems ok now preview looks ok so far

Byron

No need to be sorry. I just have a difficult time following the lines.

 

[Bentwings]

No need to be sorry. I just have a difficult time following the lines.

would it help if I use cap letter instead. I really don’t like to do that some ties I forget to turn them off

it did it again

byron

 

[Richard Hed]

would it help if I use cap letter instead. I really don’t like to do that some ties I forget to turn them off

it did it again

byron

No, that's horrible. Just try double or triple spacing every three lines or change of subject.

 

[Bentwings]

No, that's horrible. Just try double or triple spacing every three lines or change of subject.

Ok ,

next wordy ost I’ll at least double. Return each line each line.

byron

 

[Richard Hed]

Ok ,

next wordy ost I’ll at least double. Return each line each line.

byron

I can't believe you are writing on an iphone. I have a hard time doing that and I don't have eye trouble. Don't you have a regular laptop or computer with a keyboard? Yes, there are two and I believe now, even more, possible monitors for modern computers.

 

[Dynamite-ralph]

Bentwings, Just a comment about staying under 300 degrees and 150 psi,150 psi is at a temperature of 366 degrees.

 

[Bentwings]

I can't believe you are writing on an iphone. I have a hard time doing that and I don't have eye trouble. Don't you have a regular laptop or computer with a keyboard? Yes, there are two and I believe now, even more, possible monitors for modern computers.

Actually as I probably noted I have un correctable double vision . My fingers have long out grown iPhone keyboards even my iPad is hard to use. I use a stylus and hunt and peck try hitting bulls eye every time when you see two I’ve already tried eye patch but that doesn’t work. Face it I’m just messed up I have to I’ve with it I have tried the gun rang yet but that should be interesting haha I do have a very nice lap top I also hav a keyboard magnifying glass it’s nice but I’m so far behind times I just don’t use it much I received it as part of my late sons estate. He was a amer so it’s got all the memory possible and best of processors the games take up a huge amount of space I’m currently getting rid of them so gradually freeing space there is a nice cad program too but I’ve been away from that too for a long time so I’m just getting back into it. I lived with cad and analysis programs for year in engineering. I have a huge brand new PCs too but I was just getting it up when my son passed away. I’ve been picking up pieces eve since. I’ve had to give up all my hobby so I’m back doing steamers I just received notice my new engine kit is to arriv Friday I’m excited the weather is turning south today so I’ll be it shoveling again . 40-50 mph winds blowing snow misty freezing drizzle . Now this mess of compressed text . So far I have not found a fix I’ll have to try and be less wordy I really appreciate y’all’s patience we are going to start making chips this week. I’ll try and take pictures as we go or at least a chain as sssembly progresses. I have a new plastic assembly board so I can start assembl as soon as the engine arrives .

byron

 

[comstock-friend]

Bentwings , I think you need to check some of your facts re boiler pressure testing .
Model boilers should pass a hydraulic test at TWICE the working pressure which should hold steady for 10 minutes.
A steam test should follow at one and a half times the intended maximum working oressure .
Soft solder is quite good enough for low pressure boilers , Mamod have been soft soldering their boilers for at least 50 years.
Dan.

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

 

[Steamchick]

Hi John, most interesting! I always had understood that the UK, European and ASME rules always had a FOS of 8.... for the design of Copper boilers for steam....
Anyway, For ASME, I have followed the guide in Model steam and railroading published some years ago, that is the best "text book" on boiler making COPPER boilers, that I have seen. It uses and explains the ASME regs. Even down to specifying the Test pressures, etc. for hydraulic testing.
I have used it extensively to reverse engineer / check all my boiler designs that I have made, plus old boilers that I have brought back into service. Curiously, there are facets of ASME that I have picked-up from other (professional) sources, that have affected my rating of some of the older designs I have checked.
I'll study your info on Safety valves, as this is a special subject anyway, and I am unsure that all the models I have seen in-steam comply with the regs.
Although I am in the UK, where safety is concerned, the regs are usually common, worldwide. But different countries have different ideas on how much legislation is necessary, so there will always be differences. Though I doubt that boilers will be weaker in one country than another.
Thanks for your info.
K2

 

[Steamchick]

to defend myself, I did not have the internet at the time of the explosion. I was aware of the risks, I even had quite a few succesful 30 psi runs, but i will NEVER throw caution to the wind again.

I have been looking at boilers from this forum and other places on the net and I will most definatly build my next boiler with advice along the way. ;D

I'll be glad to advise - when you need it. Just for information, ASME recognise that Copper loses strength dramatically with temperature, similarly silver solder, so even using those materials we are limited to 100psi SAFELY. That is just good Engineering, not "big-brother", because there are real physical limits with the materials we use.
ASME prohibits riveted boilers, and prohibits soft soldered boilers, because there are too many accidents (like yours) in the history books.
To the regulators, one bad accident is more important to eliminate than a million successful operations.
Enjoy the hobby! (But Safely!).
K2

 

[Richard Hed]

As for myself, I don't care a twit about "awwwthenticity", I would never build a copper boiler AND I would never build a fire tube boiler, as WATER TUBE boilers are FAR safer but not necessarily easier to build. TIG welders are relatively cheap these days and thast is the best way to proceed. I bought a TIG machine that has been sitting for 3 weeks, untested, unplayed with. It is too cold to work outside with snow and winds but I have some projects to do and can hardly wait for it to warm up enough to proceed.

I have a small rocket stove I built but not quite finished that I need to work on but, as I said the cold is too much for me. To use the rocket stove properly, I need some fire bricks which I simply cannot afford right now. I need firebricks for foundry project too.

A few years ago, I built an outdoor stove/heater as a test for a design I found in a prepper book. It actually workt as designed but I feel the rocket design is even better. Had I known about the rocket design back then, I would have built it too.

Now I am mulling over a design to use the rocket stove, not only for a heat and/or cooking stove, but as a source for heating a boiler as well. Any ideas are welcome.

 

[comstock-friend]

ASME prohibits riveted boilers, and prohibits soft soldered boilers, because there are too many accidents (like yours) in the history books.
To the regulators, one bad accident is more important to eliminate than a million successful operations.
Enjoy the hobby! (But Safely!).

In 1974 ASME Section 1 (my last code book) Riveting was fine, and I assume it is now as most US Tourist Railroads and museums repair their locomotive boilers by riveting. Here is the Nevada State Railroad Museum's 'Glenbrook' in process of being riveted and as finished. She is fully approved by the State of Nevada's boiler inspectors and applicable insurance agencies..

Older joint configurations have been outlawed such as lap seams. And the interesting thing is that riveting does not require code certified personal such as welding would require, as a rivet is visually inspectable...

John