The Low Water Protective Device is balanced by which pressures on its two sides?

The Low Water Protective Device is balanced by which pressures on its two sides?

• A. Air Box pressure on one side and cooling water pressure on the other
• B. Cooling water pressure on one side and Air Box pressure on the other
• C. Oil pressure on both sides
• D. Atmospheric pressure on both sides

Answer: (B)

The Low Water Protective Device detects a low-water condition by balancing pressures across a diaphragm assembly. One side is exposed to the cooling water pressure, while the other side is exposed to the pressure in an air-filled box. Under normal water level, these pressures balance the diaphragm. When water level falls, the water-side pressure drops, creating a differential with the relatively constant air-box pressure. This shifts the diaphragm and triggers the protective mechanism to shut in or shut off the feed, preventing damage. The device is not designed to use oil or atmospheric pressure on both sides, nor to rely on equal atmospheric pressure, so the meaningful sense for its operation is the cooling water pressure on one side and the air box pressure on the other.

The Low Water Protective Device detects a low-water condition by balancing pressures across a diaphragm assembly. One side is exposed to the cooling water pressure, while the other side is exposed to the pressure in an air-filled box. Under normal water level, these pressures balance the diaphragm. When water level falls, the water-side pressure drops, creating a differential with the relatively constant air-box pressure. This shifts the diaphragm and triggers the protective mechanism to shut in or shut off the feed, preventing damage. The device is not designed to use oil or atmospheric pressure on both sides, nor to rely on equal atmospheric pressure, so the meaningful sense for its operation is the cooling water pressure on one side and the air box pressure on the other.