For the proper operation of gas feeders, an important item for consideration is the necessary hydraulic conditions. Hydraulics include the water supply necessary to operate the ejector, piping sizes and distances, pressure, and other factors. All are critical for optimum performance.

The power developed by the ejector allows the chlorine to flow from the supply containers through the chlorinator and then through the ejector vacuum line to the ejector inlet. At the ejector, the chlorine dissolves in the make-up water to form a mixture of hypochlorous acid (HOCl) and molecular chlorine (Cl₂). This is the chlorine solution which flows in the solution line to the diffuser at the point of application.

In general, the ejector locations in a system are currently used with two types; 1) Remote ejector mounting which is remotely mounted at the point of application of chlorine solution, 2) Local ejector mounting which is mounted away from the ejector point and is requiring a chlorine solution line from the ejector to the diffuser located at a remote ejecting point.

The latter mounting is mainly used to the cooling water chlorination system, since it is most reasonable to install the ejector in the make-up water supply line and then to locate the diffuser in the front of the screen of sum pit of cooling water circulation pump per the below schematic.

As previously described, the solution line should be kept to an absolute minimum. The correct diameter of a solution line is determined by:

• Rate of solution flow
• Allowable friction loss

For a gas feeder to operate properly, a sufficient differential pressure (Ps - Pb) must exist across the nozzle of ejector. It is the flow of water through the nozzle which creates the vacuum for operation. The differential pressure and water flows vary with gas feeding rate and other factors.

1) Ejector Back Pressure (Pb)

The first condition which must be considered is the back pressure which will exist at the ejector. The total back pressure is the sum of the static pressure at the point of injection (Pk), plus the friction losses (Pf) in the solution piping to the point of diffuser. The back pressure should never be allowed to drop below 2 psi.

2) Ejector Supply Pressure (Ps)

The supply pressure to the ejector is important for proper operation.