What is it?

[firebird]

Hi
I picked this up for £10.00 at an antique fair. Its copper, fairly heavy, 3 inch diametre and about 10 inches in length. The thread in the end is approx 7/8. I have it in mind to make a small boiler for a stationary engine out of it. Its clearly a pressure vessel of some sort. I was just wondering before I set to with a hacksaw if anybody knows what it is? or should I say was. I doubt that I'm going to destroy a valuable antique but you never know!

Cheers

 

[rickharris]

This is a considerable guess but I would suggest it might be and old fire extinguisher minus it's red paint.

 

[PTsideshow]

Could be a fire extinguisher bottle, of the pressure type possibly CO2 for a location that. I have a all brass one that was made for my governments warplanes.
Secondly I see there is a solder joint near the neck and there is a brass ring collar attached too the end.
The only draw back is the wall thickness will take a will to heat up and transfer to the water on the inside.
;D

 

[gilessim]

I don't know what it is, but I do have an old fire extinguisher from the 20s, from a Rolls Royce that looks similar ,but mine's definately not copper, that sounds like 1/2 whitworth pipe thread, maybe from some kind of soda syphon?

Giles

 

[Loose nut]

In regards to making a boiler out of it, DON'T, it's an unknown quantity. You don't know the grade of material or how good the seams are or even what service it was in, it may have had chemicals in it that could have detrimental properties in regards to it being a pressure vessel (chemical cracking and corrosion).

Boilers, even small ones for models are potential bombs and even doing pressure testing on it would not be adequate enough to guarantee your safety. Materials for a proper small boiler don't cost enough to take a risk.

 

[Mcgyver]

what Loose said. Although it does look very robust, but with unknown pedigree, just not worth it imo.

Still, nice sculpted piece of copper, hopefully someone can identify what it is.

 

[Bogstandard]

It is in fact what everyone said, a fire extinguisher. The soft soldered joint at the top is a safety feature. If it was ever trapped in a fire, the joint would melt and release its contents. Otherwise if it wasn't a failing joint it would explode when the pressure reached burst pressure of the vessel.

I have seen these used before as boilers, but as mentioned by other people, because of its history and unknown quality of the metal, it should not be used for boiler construction.

John

 

[Loose nut]

Take it to your favorite bar and tell everyone it's an antique copper beer bottle and see what they say.

 

[lugnut]

My first thought of "what is it", It's a container or Flask for mercury. I know that they used to use metal container to transport mercury in because glass would break if the volume was much over a few liquid ounces.
Mel

 

[firebird]

Hi

Thanks for all the comments guys. I have been getting a few different opinions. I showed it to a couple of steam enthusiasts and they think I will be ok to make a boiler out of it. I didn't mention in the original post that that 25 psi is the max I was thinking of running it at. At the risk of starting a great debate ( I posted the question cos I value the advice of you guys) I took the bull by the horns and took the flask to the band saw and chopped the end off. It looks to be fairly clean inside and has a wall thickness of .050. inch. Could I trouble you for a few further comments.

cheers

 

[CrewCab]

I don't know if this helps but domestic cold water pressure in the UK is should be around about 25psi (very roughly 1.5bar) ............. but .....all those folk with low water pressure don't pm me, contact your local water authority :

Anyway ........... copper water pipe has a wall thickness of between 0.7 and 0.9 mm (0.028" - 0.035") so your "purchase" would appear to have a good safety factor.

Must confess I'm looking forward to seeing how your going to reconnect it ......... don't think my soldering is up to that standard

atb

Dave

 

[firebird]

Hi Dave

The plan is for a horizontal boiler. I would make a flanged plate and silver solder it in.

cheers

 

[CrewCab]

Well, I will look forward to seeing that but .............. I was hoping you could show us how to make a realy neat soldered joint like the one on the original neck

Dave

 

[Loose nut]

I know you are planning on running at low pressure but 1/8" is the usual minimum thickness for small boilers. Is 0.050" safe for that pressure.

 

[lugnut]

Well there is one thing for sure, What ever it was, it sure ain't one any more ;D Hope you can make a usable boiler out of the pieces. Keep us informed with lots of your great photos.
Mel

 

[ianjkirby]

Hi Firebird,
I am a little reluctant to get into this from a distance, but maybe I can help. In one of my other lives, I am chairman of the Australian Miniature Boiler Safety Committee, a group which has been operating in Oz for just on 40 years, and we have published design and construction codes for use by amateurs, and maintain an inspection and certificating system throughout the country which is approved by the authorities and our insurers.
That said, and based on the information you have given, I can suggest that your piece of copper tube is more than adequate for the pressure at which you have stated you wish to operate it. I will have to leave it to you to determine that it is in fact "pure" copper ( you should perhaps get the cut-off bit chemically tested ), and to verify that the wall thickness is in fact 0.050". The picture showing the vernier suggests to me that it may be less than this, because the flats of the vernier faces are on the tube wall, and this will NOT give an accurate measurement. The flanged ends you intend to make and fit should have an internal radius at the flange not less than the material thickness, preferably twice the thickness ( which also makes it easier to create the flange! ). Depending on the thickness of the flanged end pieces, these may need one or more longitudinal stays between them. When all is completed ( ie, all threaded bushes for fittings soldered in ), plug off the bushes and pump it up with cold water to 1.3-1.5 times working pressure ( you will obviously need a pressure gauge for this ) for 15-20 minutes, and see that there is no movement of any of the material.
There are any number of books dealing with miniature boiler construction - if you don't have any, check out a library, or friends, or booksellers, or whatever. Lots of articles have been published in a variety of magazines around the world.
Be sensibly careful and you shouldn't have any problems.
Regards, Ian

 

[firebird]

Hi Ian

Thats very informative and helpful. Do you think the formed end would be usable as is? For hydraulic testing I thought of using the hydrolastic kit we have at work (I'm in the motor trade) thats used for pumping up the suspension on older BL/Austin/Rover cars. I chucked the cylinder in a pickling bath last night to clean it up a bit. It appears to be free of any marks or damage.

Cheers

 

[Loose nut]

Another point to think about is what grade of copper is it, boilers should be made of the right grade, I don't remember which one (K,L,M) is best, especially for the tubes otherwise you could spend a lot of time for nothing, the wrong grades won't last.

 

[ianjkirby]

Hi Loosenut,
It is my undertanding that the designators K,L,M refer to the 'class' of copper, which mainly involves manufacturing tolerances for things like wall thickness in tubes. The 'grade' of copper is something quite different, and refers to the chemical makeup of the material. With regard to miniature boilers, grades 101, 102, 106, 110 are all suitable, as they are largely oxygen free. With qualification, I can say that almost any copper which is at least 99% pure will be ok for miniature boilers operating at less than 100 psi. The website below [ just one of many ] offers a good explanation of the 'classes' K, L, M if you wish to look at it. A large amount of information is available by entering 'grades of copper' into a google search window.
Regards, Ian.

http://www.zincwirespray.com/copper tubes,type K,L,M.htm

 

[SandyC]

Hi Firebird,

I have done some calcs on your copper vessel...... given the wall thickness of 0.045" (as shown on the other site) the loop stress calculations show that your 3" dia material is safe for 96.65psi Max

The 0.070" x 2 1/2" alternative material is safe for 185.38psi.

Given that you don't have the exact specification for the copper used, I would suggest that you play extra safe and use half the above values as a max.

The calculations have already allowed for a safety factor of 8, however, these are based on Known copper type (normaly C106 would be specified for small boilers).

I would think either piece would make a very useable small test boiler for the sort of pressures you are talking about.

If you go to 'Plans' - '3 inch vertical boiler and burner plans' - and look at the last post I made on this (28 Feb 2008 in answer to 'ORRINS' request for numbers) you will find a PDF attachment showing the calculations made for this boiler...... the same formulii work for yours.

If you base your design on my 'Horizontal 3 1/2" boiler (adjust for smaller dia) then you won't go far wrong.

I would not use the pre-formed end, but suggest you make 2 flanged end plates (of at least 16swg (0.064") with corner radius of 1/8" inside rad min.
You would need at least 2 horizontal stays for a centre flue type (as shown on the 3 1/2" plans.

Hydraulic test to TWICE working pressure.... be sure to get all the air out before pumping up.
The test rig you propose should be sufficient, however, make sure the pressure gauge is accurate (calibrated)


Hope this is of some use....but just ask if you have any more questions.

Good luck.

SandyC ;D ;D