Merddin Emrys was withdrawn on 14 September for the obligatory 10-year boiler overhaul, involving the routine replacement of all tubes and any other work that is required to give the loco a new 10-year boiler certificate.
Merddin was dismantled, with the bogies run out and stored in the Erecting Shop and the tanks and cab stored outside. The smokeboxes and chimneys were removed also.
Part of the boiler inspection involves checking the thickness of plate all over the boiler. As was found on the Earl of Merioneth a number of years ago, the plate in the lower corners of the inner fireboxes had suffered some wasting, requiring patch replacement. This is not unusual for forty year old boilers. The repair involves removing foundation ring rivets, cutting out the plate, weld prepping, welding in the plate and then, finally, re-rivetting of the foundation ring. This process uses heated rivets which are air-hammered
