Caledonian Railway Company

           McIntosh 812 Class

The Boiler Overhaul

The boiler overhaul workscope took a lot longer to finalise than was originally anticipated. Several boilermakers were approached and asked to tender for the overhaul work. Although there was general agreement that replacement of the boiler barrel was required there were a number of different proposals that had to be evaluated. The final decision taken was to accept  a quotation for a workscope that included the manufacture of a welded steel barrel of 4' 91/4" diameter (as per the original) with a welded steel tubeplate. The new barrel will be riveted to the existing firebox. The boiler tube arrangement will be unchanged from the original although it is possible that the lowest row of tubes will be blanked off to eliminate problems with poor water circulation in the lower levels of the water space.

Work on the firebox will include renewal of corroded steel rivets in the lap seams of the copper inner firebox. Since we are not removing the inner firebox during this overhaul the corroded rivets will be renewed using screw rivets. The copper platework appears to be in good condition and it is felt that screw rivets will provide a successful method of repair for the next ten years of service.

On completion of the overhaul the boiler will be fully tested (hydraulically and under steam) before being returned to Aviemore for assembly onto the locomotive. The agreed timescale for the overhaul is 6 - 12 months.

More information will be posted on this page as the overhaul progresses.