Final answer:
A low water fuel cut-off is another essential safety device that must accompany an ASME safety valve on hot water boilers. The low water fuel cut-off prevents the boiler from running dry, while the ASME safety valve protects from over-pressurization.
Step-by-step explanation:
In addition to an American Society of Mechanical Engineers (ASME) safety valve, another crucial safety device that should be installed on hot water boilers is a low water fuel cut-off. This device is essential as it protects against the danger of the boiler running dry. If the water level in the boiler becomes too low, the low water fuel cut-off will shut off the fuel supply to prevent damage to the boiler or a potential explosion. A purge valve may also be included as part of the overall safety system, but the low water fuel cut-off is specifically dedicated to responding to dangerously low water levels.
It is also important to note that steam safety valves are typically used on steam boilers rather than hot water boilers. These devices are designed to release excess steam pressure to prevent over-pressurization, which could also lead to boiler damage or failure.
Therefore, while the ASME safety valve prevents over-pressurization through steam release, the low water fuel cut-off complements this by ensuring the water level does not fall below safe operating limits, thus providing a comprehensive safety system for the boiler.