Diaphragm Type Metering Pumps

When purchasing a chemical metering pump most are concerned with the features of the pump, like, the flow rate, pressure rating, available materials, life expectancy, and so on. Not so many people consciously stop to think about all of the little, unobvious things that can cause a chemical injection pump to underperform. And you probably shouldn’t, but that’s why Madden Pump has put together this article. We focus on quality, durability, and responsive customer service when it comes to our diaphragm metering pumps, we hope this article is just one more thing that helps Madden stand out when it comes to keeping your chemical addition processes running 24/7/365.

Per the experience of the workers at Madden Pump: The Top 10 “not so obvious” things to keep in mind for the best chemical metering pump experience…

  1. Carefully connecting Plastic wetted ends with rigid metal piping (even with plastic piping).
    • Often times, a plastic wetted end (PVC, Polypropylene, Teflon, etc.) is the most suitable material from the chemical you are pumping. However, not every time, for one reason or another, do you have the same material available for piping. If you are connecting any kind of rigid metal piping to the discharge and suction ends of a chemical metering pump’s plastic wetted end, keep this in mind: First, do not overtighten, snug until there is no leaking; and second, make sure the piping is not pulling or pushing on the wetted end, consider using some synthetic rubber tubing somewhere in the line to make sure there is no pressure on the plastic wetted end.
  2. If your pump is motor driven, check for motor and coupling alignment when it arrives on site.
    • Every once in a blue moon, a delivery person will drop a pump, we’re all human. Sometimes the damage can go otherwise unnoticed. So, when your pump is first put into operation, listen and look for significant vibration. If it is clearly not running smoothly, remove the coupling guard to make sure the motor and pump and coupling are aligned properly.
  3. If you need a consistent and accurate output, make sure there’s back pressure!
    • If your chemical metering pump arrives and it is dosing chemicals at a much higher rate than you need and/or even more than the manufacturer says it’s designed for, it may be because your application calls for dosing into an open stream/container/etc. Metering pumps need back pressure to function properly. Consider a back pressure valve.
  4. If you are utilizing a flow meter, make sure it is designed to read a pulsating flow.
    • Chemical metering pumps are positive displacement by design, and one of the most common types is a diaphragm metering pump. Diaphragm metering pumps are advantageous because the diaphragm feature allows for many different materials to handle any and all chemical addition needs. But they come with a pulsing flow. If you have a flow meter that cannot accurately read a pulsating flow, consider purchasing a pulsation dampener, which smooths out the spikes in flow rate and pressure.
  5. Set the pump up to have the suction end flooded, otherwise if you have a suction lift which is a condition where the pump is installed above the liquid tank, look into a foot valve.
    • Foot valves are a check valve that go at the end of the suction line. These are usually check ball valves that allow the liquid chemical to pass through into the line, but not back out of the line. This helps ensure your pump will dose accurately and consistently.
  6. Protect the pump from the environment.
    • Freezing weather, rain and snow, chemicals and chemical fumes, and heat and flames all can damage a pump or change the rate of pumping. Putting the pump in a cover or shelter will prevent environmental conditions from having a negative impact on performance.
  7. Make sure the electric motor is properly wired and protected with fuses or breakers.
    • Low voltage and/or voltage spikes can create problems for the motor and therefore the pump performance.
  8. If your chemical injection pump is going into an area of excessive vibration, consider mounting it on springs.
    • Vibration from the plant or equipment installed nearby can cause the pump’s stroke length adjustment to shift unexpectedly. Installing the pump base with shock or vibration absorbing material will insure consistent pumping.
  9. Hot and cold temperatures can make liquids easier or harder to pump.
    • Temperature plays a role in the viscosity of the liquid you are pumping. To have consistent pumping output, make sure the liquid’s temperature is kept constant.
  10. Dirty or abbrasive liquids can cause a pump to underperform, install a filter!
    • We suggest installing a filter on the suction side piping to keep solid particles out of the pump. Those particles can keep the valves from closing properly and that will reduce the pumping rate.


If you are in the market for a chemical metering pump, keep these in the back of your mind. And if peace of mind that your pump will be installed and require little to no maintenance thereafter, consider one of Madden Pump’s metering pumps.

One Reply to “Not so obvious things to keep in mind to help your Chemical Metering Pump application run smoothly 24/7/365”

  1. […] Not so obvious things to keep in mind to help your Chemical Metering Pump application run smoothly 2… 11/04/2016… Catch the problems before they happen. Madden Pump’s article gives you tips on not so common things to keep an eye on in your chemical metering applications. […]

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