Metering Pump Requirements
April 1, 2008
Metering pumps for many years have proven to be the best solution for introducing chemical into cooling towers for water treatment. However, they do have some specific requirements in order to operate at their maximum efficiency after they are installed.
Metering pumps prefer straight runs from the liquid end to the supply and injection point. When bends are introduced, a rule of thumb is to allow at least five pipe diameters from any connection point and a bend to account for acceleration changes. In order to provide sufficient net positive suction head (NPSH), the suction piping should be at least one pipe diameter larger than the suction size of the liquid end, with the supply tank located as close to the pump as possible. Because of the physical location of cooling towers, it is generally accepted that the pump can be relatively close to the tower, as well as the supply tank. However, these small considerations should be observed when installing the pump locally.
Because the metering pump and the cooling tower system operate at nearly the same pressure, and generally at proportional flow rates, they are subject to the same hazards such as freezing and other weather hazards. As a result, care should be taken to locate the pump and supply in an area least susceptible to these conditions. Adding a small shield or insulating station where needed can help ensure that the pumps operate at maximum efficiency and provide the proper cooling tower chemical treatment.