I would have to agree with Kelly regarding fusible plugs. Like everything else on a steam locomotive, these plugs have to be inspected and maintained on a regular basis. I would guess that many railroads chose not to have them to avoid that inspection and maintenance cost and focus on just keeping the water above the crown sheet. This was done through training and proper maintenance of the feed water systems and water glasses, gauge cocks and associated spindles and valves. See
49 CFR Part 230.59 regarding maintenance, if equipped, of fusible plugs.
With that said, when they were maintained properly they worked, but not necessarily every time. The SP 745 incident in 2006 showed that they did work, with 5 of the 6 plugs functioning as intended. The attached document is from some research I was doing when preparing a steam training module. I am not sure what publication it came from, but I believe was written during WWII and explains the development and use of fusible plugs. The bottom line, like everything else on a steam locomotive, if it isn’t inspected and maintained properly by personnel that have been trained on how to do it, they are just something else on the locomotive that can fail.
Based on my experience and multiple recent events, I am afraid that the lessons learned at Gettysburg have been lost to some of the current generation working with steam. In my travels with my job and consulting with others in the industry, I see training, inspection and maintenance practices are no longer a priority.
Off my soap box….
MD Ramsey
Fusible Plugs.pdf