An optional, open-ended pipe located in the suction piping near the metering pump is used to help overcome friction losses in piping from the chemical tank. Adequate pipe height is critical. Although not an absolute necessity, a calibration column is quite useful to the operator when attempting to verify the output of a chemical injection system. Chemical metering pump and drive. The pump must be selected for capacity, metering rangeability, pressure, materials of construction and type of control and drive.
Pressure relief valves.
A relief valve, relieving back to suction, on the discharge of each metering pump is mandatory to protect the pump in the event of line blockage. Back pressure valves. Adjustable back pressure valves in the discharge piping are necessary to prevent overfeeding of chemical if a vacuum develops in the process system. Varying from corporation cocks to open flow, the nozzle or method of chemical introduction to the process must be carefully considered for maximum effectiveness and to avoid blockages from crystallized build-up of chemical residue. Timers and controls.