How many automatic low-water fuel cutoff devices are required for each automatically fired high-pressure steam boiler?

For each automatically fired high-pressure steam boiler, a minimum of two automatic low-water fuel cutoff devices is required. This is an important safety measure designed to prevent the boiler from operating without sufficient water, which can lead to overheating, damage to the boiler, or even catastrophic failure.

The first low-water cutoff device serves to automatically shut off the burner when the water level drops below a predetermined point, ensuring that the boiler does not run dry. The second device provides redundancy; if the first device fails for any reason, the second will still operate to maintain a safe water level and prevent boiler damage. This dual-device requirement is a critical element of boiler safety protocols and regulations, ensuring that operational reliability is maintained.

Single devices might not provide adequate protection because there exists the potential for a single point of failure. By mandating two devices, codes and regulations enhance safety within high-pressure steam boiler systems. This is why the selection of two automatic low-water fuel cutoff devices is the correct answer.