Safety valves. The safety valve is the most important safety device in a boiler or domestic hot-water system. It is designed to relieve internal pressure if a range of failures occur within the system. Although it is simple in design and straightforward in operation, something as simple as corrosion or restricted flow within the valve and its related piping can affect its operation.  

Water-level control and low-water fuel cutoff. Many systems combine these two separate boiler-safety functions into one unit. They are designed to ensure the water level within a boiler never falls below a predetermined amount. Should that situation occur, the system is designed to shut down the boiler by cutting off its heating power. Proper functioning requires operators to make sure no build-up of sludge or scale exists within the system that would interfere with its detection and operation.  

Water-gauge glass. Even with a functioning water-level-control system, operators must verify the actual level of water in the system. Here, too, a build-up of sludge and scale can give false level indications.    Electric Steam Boilers   

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