Building a Steel Boiler....

[MCW]

I have come across many websites about boiler building, and there 90% about copper boilers, which is fine if you want to build a copper boiler. I Have read the very helpful "Model Boiler making by G.L.Pearce", but again I feel it is more for the copper boiler builder. Well I believe I would have to build a steel boiler due to size, it works out to roughly 10" diameter x 38" overall excluding smoke box.

I have a copy of the Statutory Instrument 2000 No.128 - "The pressure systems safety regulations 2000. But I still have questions.....

1) Now I have read posts and topics on here and on other website about working to published or approved boiler design, is this true? How do I obtain these published or approved design??

2) Steel used in full size boilers is low carbon, aka boiler plate, do you have to use low carbon steel in the construction of miniature locomotives?!?

3) Expanding tubes, I am familiar with the process of tube expanding, but is this really pressure tight at 100psi + ?? could the tubes not be just welded in?!?

Sorry if these are relatively simple questions to the experienced builders, but they will be the first of many!!

If anyone wants to add anything on steel boiler building i haven't asked, then please feel I would like to know all I can on the matter.

Cheers
Matt.

[jasonb]

1. The published designs will have had all the relevant calculations done on plate thickness etc and been approved by the insurance companies. If you are not making a published design you will have to submit all the calcs for approval. Whats the model you are thinking of making, this will give us an idea if a drawing is available.

2. All materials will need the correct paper work so they can be traced and must be the right spec eg boiler plate.

3. Expanded tubes will be easier to remove when the time comes to replace them and yes copper or steel tubes expanded into steel will take the pressure ( they have to be hydralic tested to twice working pressure)

4. You will mave to be a coded welder with the correct codes if you plan to weld the boiler yourself.

5. It will be difficult to get insurance if you make your own and by the time you have had your welds tested and gone to an independant boiler tester may not be any cheaper than a commercial boiler

If you know what you are doing it is possible to source the materials and do all the weld prep yourself and then get a coded welder to put it all together.

Jason

[MCW]

Thanks for your reply Jason,

1. The published designs will have had all the relevant calculations done on plate thickness etc and been approved by the insurance companies. If you are not making a published design you will have to submit all the calcs for approval. Whats the model you are thinking of making, this will give us an idea if a drawing is available.

The locomotive I'm looking at building is for the 2' gauge Welsh Highland Railway "Gelert" which is Bagnal 3050, for 7 1/4".

Where are these published drawings kept and how do you get hold of them??

2. All materials will need the correct paper work so they can be traced and must be the right spec eg boiler plate.

Test certificates, thought as much, we where going to get test certificates for the plate, welding rods, filler wire, etc. Basically every thing we would be using on the boiler.

3. Expanded tubes will be easier to remove when the time comes to replace them and yes copper or steel tubes expanded into steel will take the pressure ( they have to be hydralic tested to twice working pressure)

Like I said in my first post I am aware of the process, but what is the best method to achieve the perfect expanded tube?

4. You will mave to be a coded welder with the correct codes if you plan to weld the boiler yourself.

I have this one covered! I'll be fabricating the boiler, my good freind is a coded welder, with the correct codes.

5. It will be difficult to get insurance if you make your own and by the time you have had your welds tested and gone to an independant boiler tester may not be any cheaper than a commercial boiler

If you know what you are doing it is possible to source the materials and do all the weld prep yourself and then get a coded welder to put it all together.

So its a case of having all the right paperwork to prove to the insurance that the boiler is built correctly?!?


Thanks
Matt.

[simonwass]

Oct 17, 2009 18:45:58 GMT MCW said:

Like I said in my first post I am aware of the process, but what is the best method to achieve the perfect expanded tube?

I presume you mean by using the correct roller tube expanders?
There is a formula you need to apply, you need the tubeplate hole dia, tube od and tube wall thickness. Basically you end up with a value to end up with for the new tube id after rolling it. I'm sure it will be on the net somewhere but if not I have it at work in my old training manuals. I'm back on Tuesday.
How nice it must be having a friend who is coded! I did a 6 week intensive course at work up to class 1, even did 'test' test pieces. Management then decided that paying for coding on staff wasn't worthwhile for the actual amount we would actually weld, contractors get the job. I was planning my 1st boiler whilst doing the training
Not sure if a coded welded can do his own boiler though?

[alanstepney]

The reason that you will see little on steel boiler making is that for many years, home-build of steel boilers was not allowed. (OK, I know there were exheptions, but that statement applies to most.)

I built a steel boiler (4" scale traction engine) back in the mid 70's, when we could do so and it was not long after that, that the rules changed.
Recently they have changed again so we can, if we wish, build steel boilers ourselves, subject to a long list of requirements.

The first question is the design.
Whilst the original may have been OK, once you scale it, it is a new design and as such, will need an engineer to check and certify the design.
Not a problem, but to save work, effort and cost, do all the claculations and show them with the drawings.

Once the design is passed, (and that will include weld types, specs etc) then it is just amatter of building to the design, and, as you say, having all the paperwork to prove it.

The first question is, who are you going to insure it with?
If it is your local club, discuss the design and all aspecys of the manufacture with their boiler inspectors.
If you are going through one of the commercial insurers, their engineers will have the final say, and it is worth involving them at an early stage.

[simonwass]

Just found this on the net, look at page 14.
www.elliott-tool.com/media/tube_expander_design_usage.pdf

[MCW]

Last night I wrote a huge post and then when I came to post it, the forum logged me out, grrrrr!! Start again.

Thanks for all the replies.

How nice it must be having a friend who is coded!

It has it's advantages, we both work for the same firm, but he was put through his codes in a previous job under a contract for Corus building a massive heat exchange. The guy is a walking talking welding encyclopedia, you name the metal he could tell how to weld it, he is into the science side of welding too. I could pass my codes easy, but I don't have the money to put myself through them as the firm we work for don't require coded welder on there work.

Not sure if a coded welded can do his own boiler though?

Can't see any issues in the Pressure vessel regs or the Boiler Testing and examination on building your own steel boiler, just has to be to spec.

The first question is the design.
Whilst the original may have been OK, once you scale it, it is a new design and as such, will need an engineer to check and certify the design.
Not a problem, but to save work, effort and cost, do all the claculations and show them with the drawings.

Once the design is passed, (and that will include weld types, specs etc) then it is just amatter of building to the design, and, as you say, having all the paperwork to prove it.

Well, the only formulas for the calculations I have are in the book by G.L.Pearce "Model Boilermaking", but I get the impression there are more formulas to be used. I have seen figures of bar litres, can someone explain how to get bar litres of a boiler?!? Is there a website or member who could give me the formulas I require??

The first question is, who are you going to insure it with?
If it is your local club, discuss the design and all aspecys of the manufacture with their boiler inspectors.
If you are going through one of the commercial insurers, their engineers will have the final say, and it is worth involving them at an early stage.

I'm currently not a member of a club, but I do intend to be, so I think I better speak to them.

Just found this on the net, look at page 14.
www.elliott-tool.com/media/tube_expander_design_usage.pdf

Thanks for that link, I found out a bit more on the expanders. Are there other meathods of tube expanding?? How do you get round expanding tubes in such a small space as a fire box??

Many thanks,
Matt.

[baggo]

Hi Matt,

I use a spreadsheet downloaded from here to check copper boiler designs but it deals with steel as well:

calslivesteam.org/calculations/Calculations.htm

It's an American site but they are pretty keen/strict on designs for boilers. It will at least give you an idea of plate thicknesses, stay spacing etc. to get you started.

It's worth having a look on The Home Machinist forum, an American version of this one. They build mostly in steel and there are a lot of posts that may be of interest:

www.chaski.org/homemachinist/index.php?sid=f0a8a8ae3e3ce3c3399695fa185eb388


Bar litres is simply the working pressure of the boiler in bars (1 bar = 14.5 psi) multiplied by the capacity of the boiler in litres (full to the brim). e.g. a boiler working at 100psi (6.9bar) with a capacity of 10 litres has a bar litre figure of 69.

John

[jasonb]

Details of bar/lts here as well as a bit about design & testing

www.ntet.co.uk/pdf/miniatures_exam_and_test_code_nov_08.pdf

Jason

[MCW]

I looked at this yesterday www.ntet.co.uk/pdf/miniatures_exam_and_test_code_nov_08.pdf , and for some reason I must have missed reading point 2.8!! opps!!

But, when you calculate the volume of the boiler in litres, I assume you deduct anything inside, such as tubes, regulator, etc.

[baggo]

Oct 18, 2009 13:39:43 GMT MCW said:

But, when you calculate the volume of the boiler in litres, I assume you deduct anything inside, such as tubes, regulator, etc.

Yes, it's only the space that will be filled with water on the hydraulic test that counts.

John

[steam4ian]

G'day Matt

I know you are building under a different jurisdiction but you may find the AMBSC Code Part 2 helpful. The respective Copper Code (Part 1) has a lot of design information so I see no reason why Part 2 the steel code would not also be of assistance.

AMBSC codes options can be seen on the AALS web site and purchased through "Australian Model Engineering" (AEM); deliveries are usually quite fast.

Regards
Ian

[MCW]

Thanks for the reply Ian, some interesting information there, thanks.

---

I have a couple more questions......

1)Can anyone tell me where you get hold of these Published Boiler designs??? I've heard/read this everywhere I look about boiler construction, but nobody has yet pointed me in the right direction on this.

2) Tubes, I gather you just calculate the thickness the same as you would for do so for the boiler shell??

Thanks again
Matt.

[havoc]

2) Tubes, I gather you just calculate the thickness the same as you would for do so for the boiler shell??

No, as they are in compression and theirfailure mode is collapse while a barrel is in tension and the failure mode is bursting. But data for collapsing tubes is rather hard to find.

[jasonb]

The published designs are available from most of the model engineering suppliers, all the models they sell castings for will have a set of drawings one of which will be the Boiler Drawing.

The only Bagnal that I know of is the one M J Engineering do but thats based on a 18" gauge not 24". There may well be others as Locos are not really my thing.

Links to suppliers of 7 1/4" drawings & castings

www.ajreeves.com/

www.blackgates.co.uk/body_7_25__gauge_locos.html

www.modelmakingsupplies.co.uk/

www.pollymodelengineering.co.uk/

Jason

[MCW]

No, as they are in compression and their failure mode is collapse while a barrel is in tension and the failure mode is bursting. But data for collapsing tubes is rather hard to find.

This is true, didn't think about that, so thank you. How do other people work out what thickness tubes should be?!?

The published designs are available from most of the model engineering suppliers, all the models they sell castings for will have a set of drawings one of which will be the Boiler Drawing.

The only Bagnal that I know of is the one M J Engineering do but thats based on a 18" gauge not 24". There may well be others as Locos are not really my thing.

Links to suppliers of 7 1/4" drawings & castings

www.ajreeves.com/

www.blackgates.co.uk/body_7_25__gauge_locos.html

www.modelmakingsupplies.co.uk/

www.pollymodelengineering.co.uk/

Jason

Right, I think I've got this Published Design thing now, took me long enough!! A published design is one that is one which is tried and tested through either a model engineer magazine and/or through a trader, like the ones stated above.

I've been reading up on "The Examination & Testing of Miniature Steam Boilers", and I have seemed to have solved the 'how get a design approved' situation. if I may I shall quote two part of it...

4.1
The constructor of a boiler to other than a recognised design available through the model engineering trade and/or press shall produce design drawings and demonstrate to the satisfaction of the inspector, either by calculation or by well-proven example, that the design and materials used, have adequate strength.

4.2
If no working pressure is stated on the drawings or published
accompanying text the boiler shall be treated as a new design
and calculations shall be produced and validated.

so if I'm reading that right, it means exactly what it says...

1) I have to produce full Engineering drawings for the boiler,
2) I have to calculate every formula to show the boilers strength to the boiler inspector.

If I work along side the local model engineer club in the whole design process of my boiler, then surely I would be able to produce a Verified design.

[jasonb]

Check with your club as some don't test or have members capable of testing steel or verifying your calcs.

You may be better talking to a professional inspector.

Jason

[chiptim]

Matt,
Model Locomotive Boilers by K. N. Harris has quite a lot of design calcs starting from the basics. Not having read the G.L.Pearce book though I don't know if it has anything to add.
Regards Tim.

[klendo]

1) You dont have to be a coded welder. If your not then the rules change slightly. Initial test is 2.5 times working pressure and double there after. As opposed to double on the initial then 1.5 times there after.

2) Technically speaking as in full sized practice the tubes are not considered a constructual part of the boiler.

3) Definatley Expand tubes in by hand and dont weld them.

4) Common mistake, make sure the front tube plate holes are 1/8" bigger in the front tubeplate than the firebox end. If not it will be a sod to re-tube.

5) We used 10 Gauge tubes in a 4" foster ( over kill yes ) but they were fine..

6) Esiest thing to do to save yourself a bit of bother regarding clacs etc is to use a boiler of a similar engine which has already been ratified. Example the 4" foster boiler designed by LSM actually can be used from quite a few obscure models where there are no castings available. but as the boiler has been ratified it makes things easier. Im sure this can be done in the railway world too.

[2671jason]

Just looking through some old posts about steel boilers.Is this correct what Klendo says about not having to be a coded welder.I've never heard this said before.