When taking oil supply from the top of an oil tank, where must a thermally operated shut-off valve be installed?

The correct choice is to install a thermally operated shut-off valve at both the tank and the burner. This requirement is grounded in safety and operational reliability.

By placing the valve at both locations, it ensures that in the event of excessive temperature rise, which could indicate a potential hazard, the fuel supply can be shut off both at the source (the tank) and at the point of use (the burner). This dual placement protects against the escalation of dangerous situations, such as fuel leaks or fire, by providing multiple failsafe points.

If the valve were installed at only one location, it could still leave other components vulnerable to overheating or malfunction, thereby undermining the system's overall safety. The requirement for two valves serves as a critical safety protocol to mitigate risks associated with the handling of oil fuels.