What is not required for coil type and water tube type boilers that have forced circulation of water?

For coil type and water tube type boilers that utilize forced circulation of water, a low water cutoff is not mandated. This requirement primarily exists for certain types of boilers to ensure that in the event of insufficient water levels, the boiler would shut down to prevent overheating and potential hazards. However, in systems where forced circulation is used, the design of the boiler inherently mitigates the risk of overheating due to low water conditions, as forced circulation ensures that water is constantly moving to absorb heat and prevent localized overheating.

Pressure gauges, expansion tanks, and safety valves are critical components for ensuring safe operation. Pressure gauges monitor the internal pressure of the system, allowing operators to maintain safe operational limits. Expansion tanks accommodate the expansion of water as it heats up, preventing excess pressure that could lead to system failure or leaks. Safety valves are designed to relieve pressure if it exceeds safe levels, thus protecting the boiler from catastrophic failure. Therefore, while these components are vital for boiler safety and operation, the absence of a low water cutoff in this specific type of boiler design does not pose a significant risk, making it the correct response.