Out of curiosity (and this may be a daft question) a boiler build started some years ago and with only the internal construction started, has been built to the original design with girder stays at the crown.
Would it generally be acceptable in the UK to complete the remainder of the boiler or are girder stays now frowned upon, even if that is what is specified in the design?
I'm not able to contact my local BI at the moment so have done some reading but couldn't find anything much either way.
If thats what the published design is, and if its clear that the silver solder has flowed well around the flanges, then I don't think there should be a problem. IMHO. Plenty of boilers out there with girder crown stays.
Thanks for the take on it. That was what I had expected the case to be. Unless girder stays are now strictly prohibited which I don’t believe they are, it would seem pragmatic to be able to continue if the construction is sound.
I appreciate any calls are ultimately the discretion of the inspector but thought it worth checking whether it was something that would get an immediate ‘no’
Silver soldering the girder stay to the outer wrapper is going to be a challenge, unlike silver soldering the girder stay to the firebox crown, which was readily undertaken in an unenclosed position. The enclosed position made necessary for the girder to outer wrapper silver soldering only allows heat to be applied through the backhead aperture, so getting silver solder to the front of the girder stay is going to be difficult. Since the position of the boiler for undertaking this operation is up side down resting on the outer wrapper, heat cannot be readily applied to the outside of the wrapper as an alternative method of getting the heat forward. The design and position of the girder stays is an example of less than optimum staying. The distance between the girder stays is too wide allowing a large un-stayed gap at the outer wrapper position. The firebox has what appears to be a half girder providing double thickness of plate which counteracts the too wide gap.
Don't be drawn into thinking girder stays are inferior, or "not current practice". Take a look at Western Steam's gallery: Link to Western Steam and you'll see some boilers showing crown stays, bust most are as bald as Matt Lucas.
If the girder stays haven't been soldered to the outer wrapper yet, I'd do it with the boiler upside down, not too difficult to arrange some slim supports, heat from underneath, a perfect view from the end of when the solder melts and flows.
I usually either drill and tap through from the top of the wrapper and use bronze screws to pull the girders against the crown, or just drill and use bronze nuts and bolts, or you could use rivets, but you need some method of holding them against the wrapper.