Inspecting the Boiler

The boiler has now been fully inspected by the Project Team plus a number of third parties including:

The consensus is that the firebox is in reasonably good condition with no unexpected defects and the repair workscope will contain nothing unusual. The boiler barrel which forms the other principal component is in less satisfactory condition. At some time (probably in the late 1950s) British Railways made a patch repair which takes the form of an internal doubler plate running from the firebox throatplate to the smokebox tubeplate, i.e. the full length of the boiler barrel. The doubler plate extends from the four o'clock position downwards and round to the eight o'clock position. The firebox palmstays have been riveted to this doubler plate. (The top edge and riveting of the doubler plate can be made out on the right hand side of the first picture on the page Inside the Boiler) The reason for the repair is not immediately clear but it appears that BR had concerns over the integrity of the barrel lower section - perhaps through excessive corrosion in the lowest sections of plate. The doubler plate is very securely riveted to the boiler barrel but close inspection shows that water has been leaking for some time and has cause serious external corrosion of the outer surface of the barrel - particularly where the two barrel sections telescope into each other.

The question was whether to try and repair the existing barrel by cutting out the area of the doubler plate and forming and butt-welding a replacement lower barrel section or accepting that the barrel is life expired and should be renewed.

The majority opinion and advice offered to the Strathspey Railway Company was that the boiler barrel should be renewed. Although this is the more expensive option it is the one which the Strathspey Railway Company and the Heritage Lottery Fund accepted. The justification for the recommendation was that it would give the best opportunity for a long-term extension of the overall boiler life.

With Project Engineer Graham King in close attendance an ultrasonic inspection of the firebox outer wrapper plate thickness is performed by Mr C Reid of Motherwell Bridge Ltd. Except where already expected very little thinning was found. There appeared to be no evidence of grooving ( a common boiler fault).