How Does the Hydro-Pneumatic Tank Work?
A constant speed system requires a hydro-pneumatic tank to keep the line pressurized once the system is shutoff. When possible, the hydro-pneumatic tank is mounted adjacent to the system. This will allow for the tank to receive full, unregulated pressure by making its connection to the system prior to the pressure-regulating valve on each pump. While the system is experiencing low flow, the pump’s discharge pressure is rising. The PRV is holding a constant pressure, so any additional water pressure is diverted to the tank. The larger the difference between system pressure and final tank pressure (pump shutoff plus suction pressure), the greater the water storage in the tank bladder. The following is the formula to calculate storage capacity. It is also known as Boyle’s Law (P1V1 = P2V2). For this example let’s assume: Suction pressure = 30 psi, Pump shutoff = 45 psi, System pressure = 60 psi, and a 132-gallon tank. (Note: The usable storage in the tank is reduced 7% by the tank bladder
