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The Versamatic AODD Pump Troubleshooting Guide
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      Welcome to Your Comprehensive Guide to Troubleshooting Versamatic AODD Pumps   

      If you’re looking for troubleshooting tips for Versamatic air-operated double-diaphragm (AODD) pumps, you’re in the right place. You probably already know that AODD pumps are some of the most versatile, durable pumps around. Plus, they’re typically easy to fix when you know what to look for. 

      We’re pleased to present the following information and resources to help you fix any AODD pump issues you may be experiencing, prevent problems from happening in the future, and optimize your system for peak performance. 

      Read on for our Comprehensive Guide to Troubleshooting Versamatic AODD Pumps. We recommend you bookmark this page for future reference. 

      This guide covers: 

      Pump & Material Selection Tips

      Tips for Preventive Maintenance & Optimizing AODD Pump Performance

      Easy AODD Pump Troubleshooting Tips

      AODD Pump Components:

      First, let’s start with a review of basic AODD pump components:

      Diagram_of_Optimized_AODD_Pump (1)

      AODD pump diagram key:

      A, B: diaphragms

      C: Connecting rod. 

      1–4: ball valves and I and O the inlet and outlet ports

      How it works: An AODD pump uses compressed air to power the repeated back-and-forth motion of the diaphragms, which are mounted on a connecting rod. The continuous motion forces liquid out of one chamber for discharge while the other chamber fills with liquid.

      Pump & Material Selection Tips

      Material Considerations

      One of the most important factors is to ensure you have the right pump materials for your application. Also keep in mind whether your pump needs to meet any industry certifications, such as 3-A sanitary standards or ATEX compliance. 

      1. Analyze the following fluid characteristics:
        • Temperature. AODD pumps can handle cold and hot materials; still, the temperature of the fluid being pumped should be something you consider.
        • Specific gravity. Likewise, product weight plays a role in your decision.
        • Flammability. When pumping flammable liquids, or if fumes are present, you need a groundable AODD pump.
        • Abrasiveness. Abrasive fluid will require harder casting and seat materials.
        • Viscosity. The viscosity of the fluid being pumped should be part of your consideration. Thicker products require heavy valve balls, for example.
        • Chemical compatibility. Refer to the Versamatic chemical compatibility guide and use it to drive your selections for both the fluid end and air end of the pump.

      2. Consider pump material physical attributes:
        • Does your pump need to be portable? If so, you may need to choose a lightweight option, such as plastic or aluminum, or a smaller pump (a 1 1/2" or 2" unit rather than a 3" pump).
        • Will your pump be located indoors or outdoors? As mentioned above, it’s best to choose a metal pump rather than a plastic pump if the unit will be exposed to direct sunlight.
        • Are there any surface finish requirements? Depending on how the pump will be cleaned or sanitized, you may have surface finish requirements. For example, some 3-A sanitary units require a 32µ-in (Ra 0.8 µ-m) surface finish or better.
        • Which diaphragm, valve ball, seat/seat seal materials will work best for you? Whether you choose an elastomer or thermoplastic will depend on the chemical resistance, temperature, flex-life, and cost that works for you. Review the materials selection guide, below.
        Materials Selection Guide

        • Which wetting casting materials (fluid chambers, manifolds, seats, diaphragm plates) will work best for you? Consider the following: 

          Metal Casting
          Alloy C: Extremely chemically resistant; expensive
          Aluminum: Strong and lighter weight; average chemical resistance; popular in paint, oil, gas, and mining
          Cast Iron: Very strong; abrasion-resistant; heavy for mobile applications
          Stainless Steel: Excellent chemical resistance; commonly used for food processing applications

          Plastic Coating
          Conductive Acetal: Can be used to prevent static discharge for pumping flammable liquids
          Polypropylene: Strong chemical resistance for acids and caustics; lightweight; affordable,
          depending on the pump size

          PVDF: More chemically resistant than polypropylene; can handle most acids and caustics, even at
          higher concentrations; very strong; handles abrasion better than polypropylene

      Remember to always consult the pump manufacturer with any questions about material selection.

      Key AODD Pump Performance Specifications

      As you troubleshoot your AODD pump, performance specifications are another important thing to keep in mind. Consider flow rate, which helps determine pump size.

      Flow rate, expressed in gallons per minute (gpm) or liters per minute (lpm), is the amount of fluid you can move within a given time. Knowing this will help you determine if your AODD pump isn’t working efficiently or if you need a different pump for your system. 

      AODD pump flow rates range from 0 to 280 gpm (1,060 lpm). To control the flow rate, simply adjust the air pressure or discharge head. If you need a higher flow rate, you’ll have to get a larger pump.

      How to calculate the flow rate of an AODD pump: 

      1. Determine how many strokes the pump is making per minute. You can use an app to track the count or count how many strokes happen in 10 seconds. Then multiply that number by six. (A stroke is one shift of the diaphragm assembly moving fluid out of one chamber. A cycle is two strokes.)
      2. Reference the pump datasheet for the displacement per stroke.
      3. Multiply the number of strokes by the displacement per stroke to get the flow rate of your pump.

      Once you know the flow rate, it will help you determine the AODD pump size you need. Whenever possible, go up one size pump. Doing so will prevent your pump from running near maximum capacity, which leads to wear and tear on the pump and reduces efficiency. Going up one size allows you to run the pump at fewer strokes per minute, which will reduce air consumption and extend the life of the pump.

      Need help selecting a pump?

      The AODD pump experts at Versamatic are here to help you specify a pump for your application.


      Tips for Preventive Maintenance & Optimizing AODD Pump Performance

      AODD Pump Installation Tips

      Set up your operation for success by installing AODD pumps properly with these suggestions.

      1. Choose the right pump position within the system. There are three options.
        • As suction lift, AODD pumps are self-priming and have a high vacuum capability. AODD pumps can pull a suction lift up to 32’ (9.8m). The pump is placed above the fluid, ideally with the shortest suction pipe possible.
        • As submerged units, AODD pumps are capable of full submersion in the fluid being pumped, after you’ve confirmed that all pump materials are compatible with the fluid. Additionally, the pump’s air exhaust must be above the fluid level. If solids are present, use a suction screen.
        • As flooded suction, fluid pressure enters the AODD pump, which is below the fluid being pumped. It’s the most common use of AODD pumps and the preferred option for viscous material. Place the pump as close to the fluid tank as possible and use the shortest suction line possible. It’s also important to control the fluid pressure entering the suction side of the pump — ideally keeping it less than 10' of pressure.
      2. Properly size pump fittings.
        • Match the pump’s connection size to the fluid inlet and outlet piping/fitting. For example, use 2" or larger piping with a 2" pump.
      3. Consider compressed air quality.
        • Dirty, wet, unregulated air can damage or shorten the lifespan of your AODD pumps. Always use filtered, regulated compressed air. Air filters and regulators remove solid and liquid contaminants from the air while controlling the air volume and pressure. Remember to keep the filter clean and replace it as needed so there’s no airflow restriction. Also, keep the air exhaust muffler clean.

      Advice for Optimizing AODD Pump Performance

      1. Consider the external environment and remember to always consult with the pump manufacturer if you have questions.
        • Does the environment contain fumes? If so, the entire pump, including the air side, must be compatible.
        • Will the pump be exposed to UV light from the sun? If “yes,” you most likely need to choose a metal pump.
        • Are you pumping abrasive material? In this case, choose harder casting and seat materials.
      2. To save energy and increase the longevity of your pump, choose your pump size wisely. Experts often recommend going up one pump size. Why? The pump will cycle less, meaning you’ll consume less energy and extend the life of the pump with the same output.
      3. To prevent settled solids from damaging pump components, remember to start the pump slowly if you’re pumping fluid containing solids and slurries.
      4. To eliminate pulsation from pumping, install a diaphragm pump surge suppressor. It will ensure steadier pressure with less noise and less system vibration, which can damage the discharge system.
      5. Use liquid level controllers to prevent dry running the pump. The controllers, which essentially turn pumps off and on, are air-driven and ATEX-approved.
      6. Choose replacement parts from your pump’s manufacturer. Using parts from another source will invalidate your warranty and could cause further damage and downtime.
      7. Get to know your pump to predict when it may fail and when you should do preventive maintenance. Research pumps in similar applications to learn when you may need air side or wet side repairs, and track your pump over time to establish a maintenance and repair schedule.
      8. Consider other accessories to improve your pump’s performance. Those may include:
        • Flexible fluid connections, which can reduce pipe stress that causes leaking or damage, fluid pulsation, and protect downstream equipment.
        • Liquid-filled pressure gauges on the fluid inlet and discharge, which can inform you about pump performance and help you troubleshoot pressure fluctuations, blockages, or air restrictions.
        • Inlet stabilizers on the suction side, which can reduce pressure spikes or waves that can reduce the lifespan of the diaphragms.
      9. Keep a spare pump on hand. If an AODD pump is critical to your plant’s production, consider keeping an extra pump around in case of an emergency. It’s much quicker to swap in a spare pump than to have a pump out of service and waiting to be repaired.

      Parts & Accessories

      Genuine Versamatic service kits include all the parts you need to service your pump once you’ve taken it apart, reducing future downtime.


      Easy AODD Pump Troubleshooting Tips


      An AODD pump leak indicates you have a problem and you need to troubleshoot it quickly before you have further damage, a major maintenance issue, or a safety concern on your hands. Luckily, many AODD pump leaks are easy to fix once you identify the problem. 

      Why do AODD pumps leak in the first place? Leaks usually happen at a pump’s weakest point, so they’re typically due to one of the following issues:

      • Loose hardware. Remember to always re-torque your AODD pump hardware to the manufacturer’s specifications before installation or after rebuild.
      • Flooded suction. Too much downward pressure coming into the pump causes a flooded suction, which can create leaks at the bolt holes. Consider moving the pump up so the centerline is closer to the fluid level.
      • A weakened diaphragm. Dry running a pump for an extended period can cause this problem and create a leak. Avoid running the pump dry with a pneumatic liquid level controller.

      Identifying the leak location can help diagnose the problem in some cases. 

      • Exhaust leaks may mean you have a diaphragm failure or the bolt holes are deformed.
      • A leak at the manifold/chamber connection may mean you’ve over-torqued or under-torqued the hardware. 

      Observing the diaphragm is often the best way to understand and fix leaks. 

      Diaphragm Observation Potential Issue What to Do About It
      Discoloration or cracking Excessive heat or chemical attack Check chemical compatibility of elastomers and/or temperature of product.
      Bubbling around the edge Excessive heat or chemical attack Ensure chemical compatibility of elastomers and/or temperature of product.
      Wear marks on one side Excessive suction-side pressure or imploded air side Observe gauge on suction side for increased pressure. Try to keep below 10 psi (0.7 bar) of NPSH.
      Star pattern cracking Dry running Shut pump down when not in use. Potential application for liquid level controller.
      Outer diaphragm plate imprint Over-torquing Follow manufacturer torque specifications.

      Remember: If you have to replace a diaphragm or another pump part, whether it’s due to a leak or any other reason, replace all the components at the same time. It makes sense to replace everything while your pump is out of service to prevent future downtime. That’s why our service kits include all the parts you need to do a complete replacement.

      Suction Malfunctions

      Suction malfunctions are another problem that can damage an AODD pump if you don’t identify and fix them quickly. There are a few ways to avoid suction malfunctions in the first place:

      • Verify you're using the right pump for the right application. Read this entire guide for advice on how to properly size and select a pump. Your local distributor or a Versamatic applications specialist can also help you.
      • Run your pump in the optimal operating pressure range (60 to 80 psi or 4.0 to 5.5 bar) rather than running it at full throttle all of the time.
      • Check your line size, head pressure, and fluid levels. Pump size and line size should match; Net Positive Suction Head (NPSH) should be within the manufacturer's recommendations; and your pump should be installed in the correct location related to the tank.
      • Ensure you’ve set up the valving properly on the suction and discharge sides of the pump. Also, check your elastomers and castings to make sure they’re compatible with your application.

      If you're amid a suction malfunction, those preventive measures won’t help you. First, you need to identify your problem and understand what's causing it, and then fix it. The three most common AODD pump suction problems — and their fixes — are: 

        1. Clogged suction line. It’s caused by dirt and debris build-up. You can remedy it by routinely inspecting the pump for build-up. You can also install an inline filter to stop debris from being introduced to the pump’s suction side in the first place.
        2. Flooded suction. This problem occurs when excess pressure holds open the check valves. It causes wear and tear on the components and distorts the shape of the valve balls. The result is valve balls that don’t seat properly. The fix? Make sure you have the correct level of fluid (NPSH) above the pump.
      • Stretched/ballooned diaphragm. We see premature diaphragm failures when there’s an imbalance of air and fluid (high NPSH). You can fix this problem by moving the pump closer to the tank or by installing a back pressure device on the pump’s exhaust. 

      Erratic Operation

      If an AODD pump is operating erratically — making hissing sounds or only cycling once — you need to troubleshoot the situation ASAP. You don’t want it to lead to pump damage or downtime. 

      First, let’s talk about prevention. It’s always important to make sure your air inlet line size and air pressure are right for your application. Also, ensure the suction line isn’t clogged and that it’s not positioned at the bottom of the tank. 

      If you’ve covered those measures and you’re still dealing with erratic operation, consider the following potential problems and solutions. 

      If you are experiencing a clogged suction, discharge lines, or manifolds, first be sure to clear debris from the pump. Next, install a filter on the pump’s suction side to keep debris from building up again. This step will extend the lifespan of the diaphragms. 

      Another potential problem is lack of air or too much air supply. Make sure you’re running your AODD pumps at their ideal pressure point (between 60 and 80 psi). They can handle 125 psi, but that’s not ideal on an ongoing basis. 

      A third common erratic operation issue is an iced-over exhaust. If you’re in this situation, you can fix it by installing a dryer before the pump air inlet. You can also extend the pump’s exhaust to move the compressed air away from the center section.

      Common Air End and Wet End Problems

      If your AODD pump stops unexpectedly, you have a problem. Before you fix it, first determine if your problem is on the air end or wet end of your pump. 

      Air end problems

      If your problem is on the air end, you’ll be focusing on the pilot valve or main air valve. 

      The most common source of problems on the air end is dirty air. Upon disassembly, if you see pipe sealant, weld berries, or dirt, you likely need an inline filter. If you don’t see any dirt or debris but you see process fluid, you may have a diaphragm failure or a loose diaphragm plate assembly.

      Clean, inspect, and replace the components. Then you can reinstall the main air valve and pilot valve. To save time and rule out wet-end components, we recommend keeping spare air valves and pilot valves on the shelf for testing purposes. Wear components on the main air valve include O-rings and Glyd Rings or U-cup seals. You can replace these as individual components or buy them as a complete kit. 

      Wear components on the pilot valve include self-sealing floating pneumatic O-rings, which you can evaluate and replace if needed. Also, verify all air passages are debris-free before reinstallation.

      Wet end problems

      If your problem is on the wet end, you may be experiencing diaphragm failure. If fluid is exiting the pump through the exhaust, that’s an obvious sign.

      To fix it, you first need to shut down the pump, isolate it, and remove it from the system for repair. Next, look closely at the diaphragms. The following are common observations and what they could mean. 


      A sharp item may have entered the pump and created a cut or hole. After removing debris, install a screen filter on the suction line to prevent future punctures. 

      Scratch marks

      High fluid inlet pressures can create scratch marks on the air side of the diaphragm where contact is being made with the inner chamber. This occurs most often in flooded suction applications. Fix it by raising the pump so the centerline is closer to the fluid or by installing a back pressure device on the exhaust.

      Stretched center hole

      If you observe a stretched center hole, your outer diaphragm plate may be torqued incorrectly. You also may have high fluid inlet pressures causing the diaphragm to overstretch. Verify torque specifications in the pump’s service and operating manual. 

      Bubbling or deterioration

      Bubbling and deterioration are signs of a chemical problem. Refer to the manufacturer’s chemical compatibility guide to verify you have the correct materials for your application.

      Still need assistance troubleshooting your AODD pump? Please contact us today or check out some of our additional resources below:

      Easy AODD Pump Troubleshooting Tips

      Tips for Preventive Maintenance & Optimizing AODD Pump Performance

      Pump & Material Selection Tips


      Find a distributor

      As a reliable global air-diaphragm pump manufacturer, Versamatic has the AODD pumps that are the first choice for customers around the world who value reliability, quick delivery and convenience. Our dedicated team of distributors is always available to provide excellent service and advice.

      Find one now
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