What is the working principle of a pressurized water tank?

Core Principle: Utilizes the compressibility of air, in conjunction with a pressure switch that automatically controls the starting and stopping of the water pump, to stabilize water pressure within the piping system.

1. Initial State:

The sealed tank contains a volume of air in the upper section and water in the lower section.

It is equipped with a pressure controller (pressure relay), pressure gauge, safety valve, air-charging valve, and drain/discharge valve.

2. Water Pump Refill Phase:

As the pump delivers water into the tank, the water level rises, compressing the air above and causing the internal pressure to increase.

Once the pressure reaches a preset upper limit (typically 0.3–0.4 MPa), the pressure switch is triggered, cutting power to the pump and stopping its operation.

3. Water Consumption/Discharge Phase:

When a faucet or water outlet on the ship is opened, the compressed air expands, pushing water from the tank into the piping system—eliminating the need for the pump to start immediately.

As water continues to be drawn, the water level drops and the pressure decreases.

When the pressure falls to a preset lower limit (typically 0.15–0.2 MPa), the pressure switch resets, automatically restarting the pump to replenish the water; this cycle then repeats.

4. Safety and Maintenance:

- Safety Valve: Automatically releases pressure if it exceeds safe limits, protecting the tank.

- Air-Charging Valve: Used to periodically replenish air—compensating for air lost through dissolution in water or leakage—thereby preventing the tank from becoming "waterlogged" (filled with water and lacking sufficient air), which would otherwise cause the pump to cycle on and off too frequently.

- Drain/Discharge Valve: Used to drain water during maintenance or system flushing.

> The operating principles for seawater and freshwater pressure tanks are identical; the only differences lie in the materials used, anti-corrosion measures, and specific water quality requirements.