Calculation Method for Pressure Stabilization of Fire Protection Air Pressure Tanks

Design Calculation of Air Pressure Tank

The pressure tank of this invention comprises two primary components: calculating the pressure value at the reference point to determine the tank's total volume, and managing each pressure control. Diesel fire pumps are categorized into different types based on various classification methods. With their fully sealed, leak-free, and corrosion-resistant characteristics, they are widely used in environmental protection, water treatment, and firefighting sectors for pumping various liquids. They are ideal pumps for creating leak-free, pollution-free workshops and factories. The pump types used in firefighting systems are similar, differing only in head and flow rate. For deep well fire pumps, remove the plug to allow excess grease to drain automatically. For oil-lubricated pumps, drain oil to the correct level. Fire gas pressure equipment is categorized into different types based on various classification methods. With its fully sealed, leak-free, and corrosion-resistant characteristics, it is widely used in environmental protection, water treatment, firefighting, and other sectors for pumping various liquids. It is an ideal pump for creating leak-free, pollution-free workshops and factories. The pump types used in firefighting systems are similar, differing only in head and flow rate. The total volume calculation for the selected pressure tank capacity was determined, and the calculated pressure was used to establish the values within the start-stop pump regulator and fire pump activation pressure range.

Total Volume V of the Air Pressure Tank

The total volume of the air pressure tank is typically calculated using the formula V = VX (1 - b).

In the model, V represents the total volume of the air pressure tank (m³), VX denotes the total firefighting water volume (equal to the sum of stored firefighting water, buffer water, and pressure-stabilizing water), and the volume coefficients for horizontal, vertical, and diaphragm-type air pressure tanks are 1.25, 1.10, and 1.05, respectively. b is the ratio of the minimum working pressure to the maximum working pressure (absolute pressure) of the air compressor tank.

Total Fire Water Storage Volume (VX): The pressure tank design ensures that one fire hydrant and nozzle maintain pressure during high, initial, and pre-spring startup phases without requiring fire pumps. This duration is approximately 30 seconds. In a fire hydrant supply system, when two nozzles (each with a flow rate of 5 L/s) are used simultaneously, the required fire water storage is 2 × 5 × 30 = 300 L. For an automatic sprinkler system, when all five sprinklers activate simultaneously, the required fire water storage is 1 L/s × 5 × 1 × 30 = 150 L per sprinkler. per sprinkler. When both systems share the pressure tank, the total fire water storage tank capacity is 300 + 150 = 450 L.

The buffer water working volume V1 is typically no less than 20 L, while the pressure-stabilizing water volume V2 is generally required to be no less than 50 L.

Calculation of Pressure Control Point Value

The pressure control point is set at pressure tank 4, as shown in the diagram. Where: P1 is the minimum working pressure at the tank pressure point or the spring-loaded pressure tank's inflated pressure, i.e., the lower pressure level where the fire storage volume equals the expected pressure at the most unfavorable point (HMIN) fire hydrant, calculated using the booster pump; P2 is the maximum working pressure when the fire pump starts. The calculation formula is: P2 = (P1 + 0.098)B - 0.098.

P01 is the lower limit system pressure for constant-pressure water supply, at which the constant-pressure pump can start; P02 is the upper limit pressure-free water level for constant-pressure water supply, i.e., the maximum pressure of the pressure management working environment water tank, at which the constant-pressure pump stops.

The pressure differential between the upper and lower limits of the buffer water shall not be less than 0.02 ~ 0.03 MPa; the pressure differential between the upper and lower limits of the stable water flow shall not be less than 0.05 ~ 0.06 MPa. Due to pressure sensor accuracy and stability: P01 = P02: 0.02 ~ 0.03 MPa P02 = P01: 0.05 ~ 0.06 MPa P2 = 0.07 ~ 0.09 MPa.

Calculation Example:

For buildings closer to Class I national standards over 100 meters tall, with vertical tank pressure control regulators, the distance from the tank to the top outlet of the fire hydrant at the top floor anchor rod: H = 4 meters. The head loss from the top of the fire hydrant tank to H = 0.82 meters.

Pressure ratio for the pneumatic tank operating environment: b = 0.76

Total bellows volume: v = V × (1 - b) = 1.1 × (300)² + 0.205 × (1 - 0.76) = 1.70 m³.

Selection: SQL10000.6 pressure tank

Pressure tank charging pressure:

P1 = Hmin = Hq + Hd + HKh - H = 0.160 + 0.010 + 0.020 + 0.0082 - 0.04 = 0.