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[Solitary Sailor]

Well  here goes. My first attempt at a boiler. If you spot any howlers, please don't hesitate, I need all the help I can get.   

OK, what I'm trying to make... a 5" dia marine boiler 12" long, with a pressure vessel length of 9". There will be 2 flues/firetubes of 1.5" dia. with 11 cross tubes in each.

The above picture is of the first flue. For this part I have used oxy/acty with a brazing rod with 5% silver. From work experience I know that these joints will easily withstand pressures of around 250 psi. under pressure and are quite  safe even up to 500 psi.

[Solitary Sailor]

The cross tubes are 1/4" ID and are spaced every 3/4" on centres, but offset approx 30* for the second and third tube, before reverting to the original line. This is to create a swirling of the flue gasses (I hope) thereby holding the heat in the fire tube that little bit longer. This pattern repeats down the line.

[Solitary Sailor]

OK. Here's a slightly better picture of the cross tubes, at least the first 3. Sorry about the grainy interior of the pipe, well, at least the background is nice and clear 

[gondolier88]

Fantastic news, well done!

We need more boiler making in our hobby.

One thing- the brazing rod you have used- although it's rated to those pressures, are you sure they are suitable for steam temperatures- I have been looking at a few different (cheaper!) alternatives to Silver Solder, but not all of them were suitable for the temperatures I wanted it for.

Greg

[Circlip]

"Silver Solder" means different things on opposite sides of the pond, big debate on HMEM regularly between various and Boggy on this one. Are you building to a "Standard" design or is this a home cooked boiler? Trust you Designed it following the proper rules. Not a nark, just thinking of your own safety (AND others)

  Regards  Ian.

[Solitary Sailor]

In reply to Greg and Ian.  First off, yes, this is not a "silver solder" as understood by the modeling fraternity, it is a brazing stick with 5 percent silver content.  Given the temperature required to melt the solder, after all, an oxy/acty torch burns at a much higher temperature than  a propane / butane torch; I feel confident that the heat from the boiler's burners will have no adverse affect.

This type of solder is often as strong as the pipe it welds together. Also, it is used in circumstances where extreme temperature changes can occur very rapidly.

Now, if anybody knows of any possible chemical or structural adverse reactions that may occur, by all means let me know, and I will toss the first attempt out the window...not the first time I've wasted half a day's labour  

Having had conversations with both Bogstandard who said "no way", and Nick from Monohan Models, who said absolutely OK, and given that Nick makes these things professionally ... I'll differ to the professional. Not that I don't value Boggy's opinion, I just feel that Nick would have more experience in this field. We all, after all, are more comfortable in what we are used to.  

[Solitary Sailor]

As I recall, Boggy's opinion was more to do with the structural changes occuring in the copper piping  due to the higher temperatures involved during the brazing process.

Strictly speaking the actual process is known as "Sweating", but by going round talking of sweating, people might end up thinking they're talking to some weirdo from the tropics  

As to safety Ian. I plan on capping the ends of each pipe and pressure testing with Nitrogen to 350 psi. This will reveal any leaks as well as demonstrate the structural strength

[MONAHAN STEAM MODELS]

Nice work so far.

Here's some additional info:

Silver brazing or silver soldering is the preferred method of joining components together during the construction of copper model boilers.

However in the AMBSC Code Part 1, Issue 7 - 2001 Copper boiler code book bronze brazing is acceptable as long as its preformed by persons experienced in the process. Excessive temperatures and prolonged heating shall be avoided during bronze brazing to minimize damage to the parent metal. Filler material must be comply with AS1167.1 - 1993 Welding and Brazing - Filler Metals. Alloy RCuZnA Tobin Bronze.

nick

[Circlip]

I plan on capping the ends of each pipe and pressure testing with Nitrogen to 350 psi. This will reveal any leaks as well as demonstrate the structural strength

  So you're planning on a running pressure of 175psi.?

  Regards  Ian

[around]

As to safety Ian. I plan on capping the ends of each pipe and pressure testing with Nitrogen to 350 psi. This will reveal any leaks as well as demonstrate the structural strength

Can I suggest a hydrostatic test of the boiler components as opposed to a test with pressurized nitrogen.  A failure during a hydrostatic test is much less of a hazard than a failure when the vessel contains pressurized gas.  There are very ggod reasons why pressure vessels are tested/re-certified using hydrostatic testing!
oCheers,

Adrian

[gondolier88]

Nice work so far.

Here's some additional info:

Silver brazing or silver soldering is the preferred method of joining components together during the construction of copper model boilers.

However in the AMBSC Code Part 1, Issue 7 - 2001 Copper boiler code book bronze brazing is acceptable as long as its preformed by persons experienced in the process. Excessive temperatures and prolonged heating shall be avoided during bronze brazing to minimize damage to the parent metal. Filler material must be comply with AS1167.1 - 1993 Welding and Brazing - Filler Metals. Alloy RCuZnA Tobin Bronze.

nick

Thanks NIck, my fears are allayed now, perhaps if Solitary Sailor had told us exactly what he was using he wouldn't have been patronised as much

With Adrian on this one- ALWAYS hydro test- there should be no gas content in a boiler under test- gas expands- and thus explodes under a breach of integrity- water on the other hand, because it can't be compressed will not explode- it will drip, or spurt out of any leaks.

Would you mind showing the calculations you used to decide upon the gauge of tube you are using?

Keep up the good work, again well done!!!!

Greg

[ooyah/2]

The Blue Book on   THE EXAMINATION & TESTING OF MODEL STEAM BOILERS----( Revised Adition 2008 ) and Authorised by Sun Alliance who insure most clubs for
steam boilers on page 16 clearly says that  " WELDED BOILERS ARE ACCEPTABLE, PROVIDING THE PERSON UNDERTAKING THE PROCESS IS COMPETENT TO DO
SO"

If the welding is undertaken by a person who is not a coded welder all sorts of conditions apply.

So in the U.K. welding of boilers is acceptable.

I have over the years made many boilers and always used Silver Solder with a 42% sliver content and found that the solder flows easily and allows many joints to be done at the one time, where as welding I think would take longer as each individual joint would have to be made, as I have never tried welding I can only surmise.

Keep at it Sailor if you find welding easier , go for it, bet you wish you hadn't mentioned it !!!!!
Here are a few pics of some of the boilers made with Silver Solder.
George.



















THIS WAS A VERY BIG YARROW TYPE BOILER THAT COULD WORK UP TO 100 psi  all Silver Soldered. 

[ooyah/2]

Ment to say that I agree with Hydraulic Testing, much safer, better with a jet of water than a jet of gas,
George.

[Solitary Sailor]

Thanks for all the tips guys.

George, those boilers definitely look like you've had a bit of practice  
Also, I think silver soldering allows for a cleaner finish. I just think, (due to work experience) that brazing / sweating makes for a stronger joint. The only time I have seen one break apart is when the original brazing was done incorrectly ... ie. not get the joint hot enough to get the solder to flow properly, and I've seen plenty of these pipe joints under stresses of 450 psi and more (due to restrictions in the system), and this includes systems operating with some pretty big compressors (20 - 25 tons); these joints seem to hang in there with no problem

Nick, the approach I use is to set up most of the cross tubes in place, then heat up and braze each joint, one after the other. I think my average time per joint would be between 30 - 45 seconds, then on to the next. (The first joint taking a while longer as the surrounding metal has to be warmed up enough to stop bleeding off of the heat at the solder point). So I tend to move to a different section of the tube relatively quickly, although the in aggregate, I guess the whole assembly does get pretty warm, and   I do tend to use a hot flame, just to minimize the time where the flame of the torch is in contact with the metal; as can be seen however ( by the dis-colorization of the copper) it does get hot. Needless to say, I have to wait for a few minutes for the metal to cool off before trying to grab a hold of it to set up for the next operation...finishing off on the missing cross tubes.

Greg, I simply went for the heaviest gauge available. The 1 5/8" pipe is refrigeration type 'L' hard drawn, with a wall thickness of 1/16" Incidentally, refrigeration copper sizes are spec'd outside wall to wall, where plumbing is inside dimension, so my 1 5/8" is actually 1 1/2" inside dia.

The barrel arrived today, now that's a heavy piece of copper

[Solitary Sailor]

 

So you're planning on a running pressure of 175psi.?

 Ian


Er...not quite. Just testing to verify a high standard of integrity. My aim is for the boiler to operate between 65 - 80 psi, with the lower figure  probably sufficient for the twin cylinder engine I'm in the process of making; progress being very slow on that one right now ... actually more like coming to a grinding halt due to frustration...however, will return to the fray when the memories of rage disappears down the memory hole, which given the advancing years wont be too long  

As to every ones concern for pressure testing. I feel pretty confident with this method as I have done it many times to check for structural integrity. However, in consideration of your concern, I will go for an alternative method, I'll draw a vacuum of 29 inches water gauge, and verify it maintains vacuum for 60 Minutes. Don't know what it is about a vacuum, but when you think everything is A OK, pulling a vacuum will invariably find the weak spots. If that doesn't meet with every ones approval, I guess I'll have to go out and buy some more tools ... Oh goody 

[ooyah/2]

Hi Sailor,
Pulling a vacuum is O.K. but how do you find the leak, not sure how you would do this.
If you hydraulic it a jet of water can be seen,
Another way for small boilers and firing tubes is to solder plates on the end and solder on a bicycle valve, immerse it in a bucket of water and gently pump up and if leaking you will soon see the stream of bubbles.  Be careful as you can pump up to 60 psi very quickly with a hand pump.

Another way and not to be recommended ( unless you know what you are doing ) is that when your boiler is complete and the fire tubes are O.K. is to put a pressure gauge into one of the boiler bushes, fill the boiler FULL of water and gently heat it with a torch and bring up to the test pressure , be aware that when it gets near the test pressure it can whip up very quickly

I don't know if you have made a boiler before but just in case you don't know I would leave 1/4" bridge as a min, between your firing tubes and 1/8" min between the tubes and the boiler internal circumferance.
George.

[Solitary Sailor]

Thanks for the tip George. As to finding a leak under a vacuum, that is surprisingly easy...you can see it on the gauge, and you can hear it, provided it is not a tiny fracture, but you will still see it in a loss of vacuum on the gauge. To find the small leaks, simply charge with a small amount of nitrogen, 20 or 30 psi and set to with some dish washing soap, the leak will soon reveal itself, or, as you suggest, immerse in water.

I think everybody here is so used to the standard silver solder process, and is very aware of its possible shortfalls, especially when incorrectly done.  Introducing a different concept does bring out concerns, both legitimate and not so. Brazing with oxy/acty is a much tougher proposition from the point of view of its inherent strength when correctly  fabricated. Yes I concede that I have much to learn. But unless there is something I am unaware of regarding chemical interactions within the processes of a boiler, I suspect that my approach, especially regarding the fire tubes, will be successful. There again, this is a project in motion, and so subject to revision and outright rejection when errors occur or are revealed by superior experience. So please don't think I am brushing your concerns aside, which my holding to my course would seem to imply. Please keep the comments coming, and hopefully we can all learn something.

[steamboatmodel]

At one time I thought that I had found the ideal brazing rod, It was cheaper and easier to use than silver solder, I asked about it and was shot down in flames every where I asked. Then someone finally posted why you should not use it. Unfortunately when I copied it I forgot to copy where I got it.
"Quote from: steamer on August 15, 2010, 05:06:35 PM
Please check my last post for an important edit....Don't use Silphos on boilers. - Dave
Back in the early 1960's, Sil-Phos (aka, phos-copper brazing alloy) became popular in US live steam circles as a cheaper substitute for silver solder.  Another attractive attribute was that it was flux-less for copper-to-copper joining.  Inexpensive, flux-less, and readily available, wot's not to like?  One of the reasons for phos-copper's popularity in the 1960's was that IIRC the original Little Engines Co (of Lomita CA) suggested it for use on their cast-in-1-piece bronze fireboxes and at that time perhaps 80% of live steam locomotives being built in the US were of one Little Engines design or another. 

But after a few years a curoius thing appeared.  Boilers assembled with phos-coppers began to spring pinhole leaks in the most inconvenient places, inside front firebox flue sheets for example.  (Also, in fairness to phos-copper, the Little Engines 1-pc cast fireboxes were notoriously pourous.)  To make a long story short, it was determined by the mfgs that phos-copper, which was originally intended for cold water plumbing, deteriorated in hot sulphurous atmospheres and what could be hotter and more sulphurous than the firebox of a coal-fired model locomotive.  Naturally disagreement sprang up over its use (Disgareement amongst live steamers?  Surely not?), and a few die-hards remain, but generally speaking phos-copper for live steam is no longer accepted."
Regards,
Gerald.

[Solitary Sailor]

To make a long story short, it was determined by the mfgs that phos-copper, which was originally intended for cold water plumbing, deteriorated in hot sulphurous atmospheres and what could be hotter and more sulphurous than the firebox of a coal-fired model locomotive. Gerald

Given that these will operate in a GAS fired environment is the same liable to hold true?

Thanks Gerald I will definitely have to check with a welding supplier, maybe even throw Nick's comment his way, and see his response.

Filler material must be comply with AS1167.1 - 1993 Welding and Brazing - Filler Metals. Alloy RCuZnA Tobin Bronze.

So yes, maybe my first attempt is not safe from the scrap heap yet. Far cheaper to throw that out than that 5" barrel 

[Bunkerbarge]

My biggest concern here is not the method of joining the parts but the seemingly cavalier attitude towards testing the shell afterwards.

There is no comparrisson between pressure testing hydraulically and drawing a partial vacuum.  It is quite conceivable that a flaw could be closed up under the unusual forces generated on the parts by a partial vacuum and you could miss a leak.  Also 'hearing' the leak will not be accurate enough to be able to identify it and allow you to remedy it.

If you were in the UK your boiler would need to be checked by an inspector at a couple of agreed points during the build process and then, when completed, it would need to be pressure tested hydraulically at twice the working pressure.  The working pressure would be determined by the drawing, if built from a plan, or by calculation, if made from a personal design.  The only way to test a boiler shell is hydraulically, any other method is not reliable and would not be acceptable.  The subsequent certification includes the working pressure and the test pressure.  We seem to be drawing numbers out of the air here and then using a 'suck-it-and-see' process to test them.

I think I need to make it quite clear at this point that the views expressed within this thread are not necessarily the views of the Modelboatmayhem team or it's ownership.  Pressure testing of boilers is an extreemly serious process and should only be conducted under the guidance and supervision of an experienced and qualified tester as identified by an accredited club.

[Circlip]

Haven't noticed on this forum (having said that, I haven't seriously looked for one) but on other fori which have a "Safety" element involved, I have sent a PM to the site owners to add, for their OWN security, a disclaimer so that anyone injured by blindly following "I saw it on whatever so it must be OK" threads have no recourse for a "Blame Claim".

  In general, toy boats don't normally constitute a danger to the owners or general public but steam is an exception and as such, due to the fact that some think they can claim for tripping up over a matchstick, perhaps Martin should cover his a-- posterior and add one for his own safety.

  Regards  Ian.

[pugwash]

I think Circlip has some merit in his argument.  As he says people will sue under any grounds
and sometimes insurance companies will settle rather than have the hassle of a court case.
Finally who knows which side will the court will favour, there have been some very strange
rulings recently. Lets face it when we all get heated up over certain topics we have some
very radical views which some who may be visiting the forum may find offensive but they
can't be held as Martins' personal opinions.  A disclaimer somewhere prominent should nicely
cover Martins' back.
Geoff

[Bunkerbarge]

Rather than have one too prominent and take up valuable front page real estate we tend to add a statement such as the above to make it very clear that Mayhem does not necessarily condone the views of the membership etc...etc...

We've actually got it written out somewhere but I couldn't find it in time and I wanted to get something up quickly.

[Bunkerbarge]

This is what I was thinking of which is obviously far more sales related.  Maybe we need to make it a bit more all encompassing.

http://www.modelboatmayhem.co.uk/Disclaimer.htm

[Solitary Sailor]

Bunkerbarge ... obviously the opinions I am expressing are my own and in no way can be construed as being endorsed by Modelboatmayhem, its owners, or its members.

As I have stated above, I realize that these methods are not those which are normally accepted within the modeling fraternity, I am bringing a different experience to this project. One from a lifetime spent working with pressure containing systems, not water boilers true, but pressure containing closed systems. Believe it or not Bunkerbarge, my desire is to have a boiler as safe as you or anyone else could wish it to be.

I am simply trying to ascertain the structural integrity of these fire tubes before proceeding with any further construction.

Your disapproval is duly noted.