Which of the following is included in the safety devices associated with boilers?

The inclusion of flame scanners as safety devices associated with boilers is based on their critical role in fire detection and prevention. Flame scanners are designed to monitor the presence of flame in the combustion chamber of a boiler. They ensure that the burner is operating with a proper flame and that fuel is being efficiently burned. If a flame is not detected when it should be present, the flame scanner provides a safety shut-off to prevent the release of unburned fuel, which could lead to explosive situations or other hazards.

In contrast, while thermocouples are instrumental in measuring temperature within a boiler system, they primarily serve monitoring purposes rather than direct safety controls. Flow meters, similarly, are used to measure the flow rate of water or steam and alert operators to variations in flow but do not directly prevent hazardous conditions. Temperature indicators serve a similar function by displaying temperature readings but do not actively engage in safety mechanisms. Hence, flame scanners are the most directly relevant to ensuring the safe operation of a boiler system.