All Pumped up!

Well a definite milestone was reached today; the boiler passed its official initial hydraulic test at 500psi conducted by our Boiler Inspector.

It will never need to be pressed that hard again, next we have a 375psi test with all the ancillaries fitted (gauges, valves, plumbing etc.) then we put some fire in its belly and prove that the safety valves will stop the pressure going more than 10% higher than its 250psi operating pressure – then we will be allowed to insure it and use it in anger!!!

This might seem like a bit of a palaver, but a boiler failure will typically kill everyone within many feet – so it pays to take care.

When you consider that the pressure trying to force each end cover off during the test is equivalent to a large African Elephant standing on it, you can see why it uses a bunch of M16 and M20 studs to hold everything together!

Boiler sitting at test pressure.

500psi on the clock

500psi on the clock

A Few Notes

It took three attempts to get everything perfect, and here are a few notes for other builders:

  • The dome nuts needed to be skimmed, as the imperfections in their surface were enough to produce a significant shower at 200psi as they prevented the dowty seals from working.
  • One of the tubes had not been expanded into the mud drum – that started leaking without any pressure!
  • The stays on the steam drum needed shortening by about 200-thou to stop them bottoming in the dome nuts (it’s a bit of a fiddly dimension, as you must ensure enough thread is engaged with the nuts even with one end completely screwed up to the limit.)
  • The upper end of some of the tubes were a bit long and clashed with the lower stays in the steam drum, resulting in an hour or so with a Dremmel and air-driven countersink, to provide the necessary clearance.

Either way, an important day on the route to launch day!

2 thoughts on “All Pumped up!

  1. Peter Bourke

    Hullo again Malcolm,
    I last contacted you some time back. I have spent the last nine months restoring – that is fairing and glassing – the hull of my 26ft Evintide. Cannot believe it took so long .Have just recommenced work on my steam engine [same design as your own] I built the bottom end some time back and and currently machining the cylinder / valve assembly. So I am obviously at the opposite end of the spectrum to yourself. I intend building a Yarrow type boiler and would be a bloody idiot not to follow you guys. As I live in Australia I seem to be having trouble accessing the plans through the UK Steamboat Association. I would certainly appreciate any advice on how to obtain the yarrow plans. Once again I must thank you for your fantastic blog.
    Hooray for all the steamboats with a sail;
    Cheers Peter

    1. sybefur Post author

      Hello Peter, glad to hear you are making progress – this boat building lark certainly demands a tenacious character. My plan was to be in the water in 2015, but it’s looking like next year now!

      The Engine is a nice one to build, and I think we have captured the main issues to keep an eye out for in the “Leak Hints and Tips” pages. I think the biggest struggles were the hand scraping of the main bearings & slideways and the valve timing – but I am conscious that it has yet to prove itself in practice.

      As to the boiler there are two sources – firstly the SBA provides drawings (of a couple of versions, from memory) as part of the boiler design service (but these principally just focus on the pressure vessel).

      Secondly John King sells a variety of designs of 2-drum and 3-drum versions. These are very good and include everything including all the ancillaries and an extensive manual. These are the plans I used. I know several have been built in NZ (more upside-down-folk!), and there is a great album of pictures of the build here.

      If you email me Peter, ( I can provide you with some contact details for both sets of designs – well done, keep up the good work.


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