DISASTER!!! on 15F steam locomotive courtesy of fusible plug

You have to watch the video for 3 minutes and 40 seconds to see what happened!
A fusible plug, also known as a safety plug, or threaded fusible plug. It is one such safety device that is commonly used in steam engines. It ensures that in case of water levels recede to dangerous levels, operators will be alerted by a strong stream of steam, allowing them to take action.
A fusible plug is a threaded cylinder of metal, with a tapered hole drilled completely through its length. This hole is sealed with a metal of low melting point that flows away if a pre-determined, high temperature is reached. The initial use of the fusible plug was as a safety precaution against low water levels in steam engine boilers.
Typical locations for fusible plugs include the crown sheet (top of combustion chamber), rear tube sheet (Scotch marine boiler) and front tube sheet (firebox boiler). The location chosen depends upon the boiler design.

[@rudolfhough6226]

A fuseable plug has to be properly cleaned by wire brush and a correct dia tap used to clean the threads inside the plug. Then using salammoniac it must be tinned at the correct temp and can then be filled with lead and the date stamped on it. If it is incorrectly done the lead will not adhere to the copper plug and the water pressure will force it out. That would be the fitter,s fault and that can be seen by examining the dead firebed .If a hole is blown in the firebed then only a jet of water can do that and the glass must have been full. However , steam on a hot fire will not blow a hole in the firebed and that means no water over the plug with possible leaky stays or worse .If no damage then my guess is an ill prepared plug by the fitter. All plugs must ALWAYS be checked by each crewmember for possible dripping of water when coming on duty and reported in the logbook of each engine.

[@adriannettlefold9084]

We had one of our locomotives have the same thing happen. I believe it was a new style plug with a bigger orifice for the lead. It fused on it's first run.. luckily no one was injured nor the boiler damaged. Great videos by the way.

[@rudolfhough6226]

Giving more area for lead to pick-up heat is wrongthink in my opinion

[@hotboxxxexxxpress1509]

Did the injectors fail? What caused the low water level in the boiler? I hope the damage isn't extensive enough for a firebox replacement.

[@earthfirechannel]

The only damage was the ''melted' fusible plug that was later repaired as per the end part of the video. We never established, for sure, what caused the "disaster". It could have been 1) the fireman's negligence, 2) old fusible plug or 3) faulty fusible plug.