Air-operated double-diaphragm (AODD) pumps are a simple, reliable tool for plants of all types, but they do occasionally require troubleshooting. One potential issue is a suction malfunction, which can damage the pump and take your equipment offline if not remedied quickly. Fortunately, you can easily prevent, identify, and fix most AODD suction issues if you know the basic components of an AODD pump and you know what you’re looking for.
If you’re blowing through diaphragms prematurely or your check balls are wearing unevenly, this article is for you.
HOW TO PREVENT AODD PUMP SUCTION MALFUNCTIONS
The best way to avoid suction problems is to ensure you’re using the correct pump for the correct application. Before making an AODD pump purchase, work with the manufacturer’s applications team to make the right pump choice in the first place. Pump size is an important consideration. The optimal AODD pump operating pressure is 60 to 80 psi (4.0 to 5.5 bar). While you can, you don’t want to run it at maximum pressure all the time. For that reason, many customers choose a pump one size up to ensure they’re not constantly running it at full throttle.
That said, sometimes users adjust their applications over time. If that’s the case, verify the following specs are correct for your application to avoid suction issues:
- Line size – matching pump size to line size is critical
- Head pressure – ensuring Net Positive Suction Head (NPSH) falls in line with manufacturer's specifications
- Fluid level – understanding where the pump is installed in correlation to the tank
COMMON AODD PUMP SUCTION ISSUES
The following are a few common AODD pump suction problems and how you can remedy them.
Problem: Clogged suction line
|What causes it: Dirt and debris that builds up over time.
|How to remedy it: Routinely check the pump for debris, or install an inline filter to prevent solids from entering the suction side of the pump.
Problem: Flooded suction
|What causes it: Too much pressure holds the check valves open creating unwanted wear, ultimately distorting the shape of the valve balls so they no longer seat correctly.
|How to remedy it: Ensure correct fluid level above the pump, also known as NPSH.
Problem: Stretched or ballooned diaphragm
|What causes it: High NPSH, an imbalance of air and fluid can result in premature diaphragm failure.
|How to remedy it: There are a number of ways to combat this issue. The easiest is to move the pump closer to the liquid level of the tank you are pulling from. If this isn’t possible, a back pressure device fitted to the pump’s exhaust can help alleviate this concern.
In addition to the steps above, make sure the valving is set up correctly on the suction and discharge sides of the pump, and ensure you are using the correct materials, including elastomers and castings, for the application. For instance, if you’re pumping a thick substance, you should choose heavier valve balls that won’t float. Doing so will ensure the pump fills its chamber completely on its suction stroke, which means it will be operating as efficiently as possible.
When in doubt, contact the Versamatic team for assistance with pump suction malfunctions or to purchase parts and accessories.
To learn more AODD pump troubleshooting tips, refer to part 1 of our troubleshooting series about leaks or stay tuned for part 3 on erratic operation. For more information about the easiest-to-troubleshoot AODD pumps on the market, contact Versamatic or check out additional resources, which offers easy access to videos, service manuals, and more.