Boiler approval and testing

[Nick Clarke 3Participant @nickclarke3]

Posted by Hopper on 09/07/2022 22:52:29:

Which raises an interesting question: There are steam boiler codes and legal requirements for the building and testing of model steam boilers and the issuing of certificates. But are the operators of such models required to have any training and/or pass any kind of test on their knowledge of safe boiler operation?

Both the clubs I am a member of have testing and retesting regimes for driving and being a guard when carrying members of the public but when they are not present these are relaxed to allow training and practice to take place.

[Paul KempParticipant @paulkemp46892]

The Medina incident is not a good example to use for low water level failure as the boiler was clearly structurally unsound in the first place and also that there were no surviving witnesses to provide account of the events. There was also some dissent between the professional boiler inspectors on whether low water was the cause or contributory factor.

They were agreed that the crown sheet had extensive wastage of up to 77%, that the crown stays had wastage and the thread engagement due to crown sheet thinning was only about 30% of what would be required in some areas. The crown also showed signs of “bagging” (quilting in the uk) that may have been pre-existing. The pressure gauge was under reading, the safety valve rated for 125 psi did not lift until 253psi when tested after the event. The fusible plug was in place but was insulated on the water side by a build up of scale and was intact. Parts of the crown sheet towards the front of the firebox showed signs of overheating, those at the rear did not.

Taking all of the info and comments the one thing I did not see was a record of any inclination of the ground the engine was stood on at the time of failure – uphill slightly could lead to a circumstance where there was water over the back of the crown (where the fusible plug was located) but little or none to the front of the crown. My conclusion from all the evidence is if low water was the cause at the point of failure it can’t be proven (boiler had undoubtably experienced low water at some point though). What is beyond doubt is irrespective of the water level the boiler was structurally in a dangerous condition, had not been well maintained and thus a failure at some point was inevitable.

I will try and find the narrow gauge loco report I referred to earlier.

Paul.

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