This is the second of eight articles in the series Sizing & Selecting the Right Chemical Metering Pump. Read the previous article “Planning for your Application.”
A metering pump is used to inject chemicals precisely into a process to achieve a certain desired result. That result could range from a certain amount by volume or mass of fertilizer to a definite amount of acid into water to achieve a certain pH balance. Or it could even be a certain amount of disinfectant into water to achieve a predetermined amount of PPM (parts per million).
The actual injection rate or the rate at which the chemical needs to be added depends upon the application, desired result and also the concentration of the chemical. For example, in case of the amount of chlorine the formula for calculation of the chemical injection rate is:
IR = 0.006xQxC / S
Where Q – System flow rate in GPM, C – Desired PPM for the chemical and S – Concentration of the chlorine bleach in %
There are many methods to arrive at the desired chemical injection rate and usually engineers will specify the exact rate using such methods based upon the application. Once you know the rate of chemical injection which is usually given in Gallons Per Hour (GPH), you need to then start the process of sizing the pump.
The second most important piece of information is the pressure that the pump needs to overcome to inject the chemical. If you are injecting into a pipe then the chemical pump needs to be able to overcome the pressure in the pipe as well as the pressure drop in the chemical lines from the chemical pump to the injection point. A pump injecting into a pipe […]