Monday, 9 March 2015

Chuff Proofing (1)

Sentinel 7109's boiler top has received a lot of attention in the last five months, particularly since it has been indoors. Last October, there were no chimneys and the cab actually felt quite roomy!

The first photo below shows where the four-ringed superheater inlet dips below the boiler top surface.
October 2014
The second photo shows the first of two three-part 'superheater steady plates' to keep the superheater tubes well sealed and to prevent air being drawn in with each chuff. (Co-owner Nigel's handy-work with cardboard templates and sheet stainless steel here).
March 2015
Eventually there will be some ceramic wool etc. applied to seal the gaps even better (when we've figured out how to do it!).

Eagle eyed observers will of course notice that the first photo shows the superheater's inlet and the second shows the superheater's outlet. The inlet steady plate has still to be done. The three parts are not easy to make and have to be shaped carefully for a snug fit.

The gaps have to be well sealed in the same way that a conventional steam loco has to have a sealed smoke-box door. In either case, if there are leaks, when the loco chuffs, it draws air in through the gaps instead of up through the fire. The consequence being that it will lose steam generating efficiency.

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