Model boiler design information

Discussion in 'Boilers' started by Dan Rowe, Mar 31, 2010.

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  1. Mar 31, 2010 #1

    Dan Rowe

    Dan Rowe

    Dan Rowe

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    One of the best sources of information on model boiler design is the Australian Miniature Boiler Safety Committee. (AMBSC) The four books (1) Copper (2) Steel (3) Sub-miniature and (4) Duplex Steel
    http://www.smex.net.au/Store/Store_AALS-Codes.php

    Model Boilers & Boilermaking by K. N. Harris has a wealth of good design information and construction methods. Topics covered include fuel and firing and accessories. (Copper boilers)

    Model Locomotive Boilers by Martin Evans is also a good source of design information and methods. It covers welding equipment, workshop equipment, water, fuel and combustion, oil and gas firing, and testing. The testing is more than a simple hydro a full engineering test stand designed by J. Ewins is described with drawings of the boiler and test results. (Copper and steel boilers)

    Safety of Copper Boilers by Kozo Hiraoka this nine page article was first in Live Steam & O.R. (Vol. 40 No. 6 Nov-Dec 2006) and is included in Building the New Shay. The design rules are presented in graph form for simplicity with the ASME formulas and code designation listed in the appendix. All graphs have a metric and an imperial version. The graphs are (1) Minimum thickness for a cylindrical shell under internal pressure (2) Maximum allowable pitch of symmetrically arranged staybolts (3) Maximum allowable diameter of a circle enclosing an unstayed surface area (4) Minimum staybolt diameter. This book like all of Kozo’s books is a treasure trove of useful information for the model engineer.

    These are the four main sources of model boiler information in my stack. Several other model engineering books I own have boiler chapters but the information is not a complete design system. These include works by Greenly, LBSC, Tubal Cain, and Martin Evans.

    Cheers Dan
     
    robcas631 likes this.
  2. Mar 31, 2010 #2

    xo18thfa

    xo18thfa

    xo18thfa

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    Dan: Do you have a copy of the AMBSC?
     
  3. Mar 31, 2010 #3

    Dan Rowe

    Dan Rowe

    Dan Rowe

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    Yes Bob,
    I have a copy of all 3 sections of the AMBSC and I have read each one cover to cover more than once.
    That is the reason I recomended it as a very good source of boiler design information.
    Cheers Dan
     
  4. Mar 31, 2010 #4

    steamboatmodel

    steamboatmodel

    steamboatmodel

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    Hi Dan,
    What is the difference between a Miniature and a Sub-Miniature Boiler?
    The Australian Miniature Boiler Code - Copper Boilers. $24.40
    The Australian Sub-Miniature Boiler Code. $12.00
    Regards,
    Gerald.
     
  5. Mar 31, 2010 #5

    Dan Rowe

    Dan Rowe

    Dan Rowe

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    Hi Gerald,
    Here is a link to another source of the AMBSC boiler code with miniature and sub-miniature limits. There is also a link for the index of all three books. http://www.smex.net.au/Store/Store_AALS-Codes.php

    Basically the sub-miniature AMBSC is a lot more relaxed for boilers 3" OD, 75psi, 1 liter capacity and below.

    Cheers Dan
     
  6. Apr 1, 2010 #6

    xo18thfa

    xo18thfa

    xo18thfa

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    The reason I ask is because I was wondering how Kozo's article in the new Shay book compares.

    Bob
     
  7. Apr 2, 2010 #7

    Dan Rowe

    Dan Rowe

    Dan Rowe

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    If you compare the index to AMBSC Part 1 and the index I copied from Kozo Hiraoka paper on the Safety of Copper Boilers you will see that they both cover approximately the same material. Kozo’s work is directly traceable to the ASME code with all references given. Kozo states “The ASME code is more conservative than prevailing model engineering practice,” this most likely includes the AMBSC. The choice of which design system to use is often dictated by the location of the builder.

    I like the AMBSC nomogram for solving the relationship between boiler pressure, heating surface and safety valve orifice diameter better than what Kozo presents on this topic. For the same reason I think the graphs in Kozo’s article make working the calculations and what if’s simpler. The AMBSC has a lot more drawings of design examples and I like a lot of drawings with my model engineering.

    The link for the index to AMBSC Code Part 1 Issue 7-2001: Copper Boilers is here: http://www.smex.net.au/Store/Data/AMBSC_Code1-Idx.htm

    Safety of Copper Boilers by Kozo Hiraoka
    Index
    1 Advantage of Copper Boilers
    2 Reference Code (ASME Sec I, Sec II, Sec VIII)
    3 Safety of Copper Boilers
    3.1 Materials
    3.2 Cylindrical Shells Under Internal Pressure
    3.3.1 Surface Stayed with Symmetrically Spaced Staybolts
    3.3.2 Surfaces Stayed with Irregularly Spaced Staybolts
    3.4 Specifications of Plate Thickness
    3.5 Staybolts
    3.6 Ribs
    3.7 Crownsheet Stays
    3.8 Joints
    3.9 Hydrostatic Test
    3.10.1 Water Gauge
    3.10.2 Pressure Gauge
    3.11 Water
    Appendix 1 “Boilers Fabricated by Brazing” in Section I ASME Code
    Appendix 2 Cylinder Componets Under Pressure
    Appendix 3 Flat Surface Stayed with Symmetrically Spaced Staybolts
    Appendix 4 Staybolts
    Appendix 5 Hydrostatic Test Pressure
    5.1 Section I “Power Boilers” of ASME Code
    5.2 Section VIII “Pressure Vessels” of ASME Code
    Appendix 6 Boiler Fittings (Section I Power Boilers)
    6.1 Water Gauge
    6.2 Pressure Gauge
    6.3 Safety Valve

    Cheers Dan
     
  8. Apr 2, 2010 #8

    steamboatmodel

    steamboatmodel

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    Thanks Dan,
    It looks like the sub-miniature AMBSC is what I will add to my shelf next to the Harris's books.
    Regards,
    Gerald.
     
  9. Apr 5, 2010 #9

    Dan Rowe

    Dan Rowe

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    Can any of the UK members tell me where I can read or buy a current UK model boiler code for copper boilers?
    Both Harris and Evans were from the 1960's can they still be used for modern practice in the UK?

    Dan
     
  10. Apr 5, 2010 #10

    xo18thfa

    xo18thfa

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    Harris talks about rivet and soft solder caulk construction.

    Never heard a reason why that is so bad.

     
  11. Apr 5, 2010 #11

    Dan Rowe

    Dan Rowe

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  12. Apr 5, 2010 #12

    GWRdriver

    GWRdriver

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    Hi Bob,
    I've never seen a published point by point explanation of why, but when in the opinion of the overwhelming majority of designers and builders in the modern industrialized live steaming nations says abandon soft solder construction and to unilaterally adopt silver solder, I won't be wasting any of my time trying to argue and prove them wrong. My own take on the reason for it is it's not that soft solder construction is so bad, so much as silver solder construction is so good. It's just plain better technology. My understanding is the main problems with soft solder occured in fireboxes where even if 100% if the reqiired structural strength of the boiler was developed in the fasteners and staying, and that would not always be the case, the heat of coal fires is such that the soft solder caulking would break down and failures would occur.

    Although I don't know for sure, because I only have the previous edition, I think in the latest edition of Harris the references to soft solder construction have been deleted or annotated.
    Harry
     
  13. Apr 6, 2010 #13

    xo18thfa

    xo18thfa

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    Thanks Harry. I have the 7th edition of Harris (1977) and it's on page 33 (end of Ch 2) where he talks very briefly about it. I don't recall him mentioning it anywhere else, and he certianly does not specify it as a procedure.

    I would not use soft solder caulk. Just wondering why it fell out of favor. As you know, I am a big fan of LBSC and he always used it for sealing mechanically secured stays inside a firebox.

    Take care

    As you know, I am a big fan of LBSC. He used soft solder a lot to caulk mechanically secured stays inside a firebox.
     
  14. Apr 6, 2010 #14

    Maryak

    Maryak

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    Try page 86 on Caulking. (2000 edition).


    Section 2.6 of my copy of AMBSC for Copper boilers permits the use of 60/40 or 70/30 soft solder as caulking materials.

    Best Regards
    Bob
     
  15. Apr 7, 2010 #15

    Dan Rowe

    Dan Rowe

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    I checked the document linked by JasonB on the US boiler code thread for mention of soft solder. This is what I found:

    SPECIFIC REQUIREMENTS FOR
    NON-COMMERCIALLY BUILT COPPER BOILERS

    The materials used for silver soldered or riveted/soft solder caulked boilers must be suitable for purpose, although material certification is not required when these forms of construction are adopted.

    Complete text: http://www.ntet.co.uk/pdf/miniatures_exam_and_test_code_nov_08.pdf

    So I know that the formulas for the strength of boilers in both Harris and Evans are the same formulas used by all engineers for this type of calculation. The devil is in the details like what is the assumed max stress for copper and if there is material temperature compensation applied. Harris does not have a temperature factor and Evans does. The Maryland model code is temperature compensated. The AMBSC simply specifyes the minimum plate thickness for various pressures allowed. Kozo's paper uses a graphical method with temperature compensation and formulas given in appendix.

    So to get to the point can some UK member verify that the formulas in Harris can be used for current UK model pressure vessel calculations?

    Cheers Dan
     
  16. Apr 12, 2010 #16

    ianjkirby

    ianjkirby

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    Hi guys,

    I would like to add the following just for clarification.

    AMBSC code part 1 is for copper boilers up to 203mm dia, 25 litres water capacity, and 700kPa.
    AMBSC code part 2 is for carbon steel boilers up to 255mm dia, 50 litres water capacity, and 700 kPa.
    AMBSC code part 3 is for boilers than up to 76mm dia, 1 litre water capacity, and 520 kPa.

    A proposal for the use of stainless steel alloy 2205 (a duplex alloy, and quite specific in its welding requirements) is currently being investigated, and looks to be suitable at this point in time. Approval of statutory authorities is the next step in the process.

    Part 3 is essentially for gauge 1 (or garden gauges) non-passenger-hauling locomotives, and R/C model boats, and other similarly powered vehicles.

    With regards to the use of common (or leaded) soft solder, it is allowed in AMBSC for caulking purposes, but is highly discouraged for the fact that if it fails to fix leaks, repairs using silver solder are practically impossible, because it (silver solder) will not take over soft solder. If you need to fix a leak, try silver solder first. You will usually only get one chance with soft solder.

    Regards, Ian.

    (Recently retired Chairman, AMBSC)
     
  17. Apr 13, 2010 #17

    xo18thfa

    xo18thfa

    xo18thfa

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    I think I need a copy of Part 3
     
  18. Apr 13, 2010 #18

    ianjkirby

    ianjkirby

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    Hi Bob,
    The AMBSC codes are available from sources in earlier posts in this thread. Please keep in mind that they are only legal in Australia and NZ. They may be used as guides any where in the world, but have no authority outside Oz & NZ.
    Regards, Ian.
     
  19. Apr 13, 2010 #19

    xo18thfa

    xo18thfa

    xo18thfa

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    It's an up-to-date guide for sure. I just want to make sure what I am doing is right.
     
  20. May 8, 2010 #20

    clippermaniac

    clippermaniac

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