4 Tips to Prevent Diaphragm Failure on AODD Pumps

Author: Sara Peters | May 21, 2019 | Category: Equipment Maintenance, Pumps


Recently, a Crane sales engineer and I toured a manufacturing facility in southern Wisconsin. As we walked through their shop filled with air operated diaphragm pumps waiting for repair, I noticed they were covered in product. Failure after failure caused unplanned downtime, and to add insult to injury, a huge mess to clean up.


After we left, I asked the sales engineer what impact the spills had on the business and how they could improve the reliability of their pumps. He said the impact on the business was pretty big, and he shared four tips that would extend the life of their pumps.

Why Ruptured AODD Diaphragms Are a Big Problem

Spills from AODD pumps concern manufacturers, from both environmental and profit perspectives. A spill isn’t easy to clean up. Oftentimes, workers will throw a substance like oil-dry or kitty litter on the spill to absorb the liquid. Then someone has dispose of the liquid by shoveling it into a waste container.

It gets trickier when the fluid spilled is hazardous waste. The manufacturer then must pay to have the waste trucked off and treated before disposal. It’s extra cost to what has already cost the manufacturer in lost time and lost product.

Spillage of some fluids means additional disposal fees or even fines. Fluids such as:

  • Paints, inks, and coatings
  • Adhesives and resins
  • Chemicals and petrochemicals
  • Oils and hydrocarbons
  • Acids, caustics, corrosives
  • Resins and polymers
  • Contaminated water and wastewater
  • Pesticides and herbicides
  • Fertilizers
  • Preservatives
  • Mercury
  • Phthalates

Some fluids are extremely expensive. Losing them is very costly to the manufacturer:

  • Drugs and pharmaceuticals
  • Foods
  • Cyanotic based paints
  • Precious metal passed fluids
  • Cosmetics
  • Perfumes
  • Printer inks
  • Beer and alcohol
  • Blood
  • Creams and lotions

Why AODD Diaphragms Rupture

Running the pump dry, or deadheading the pump are common ways that diaphragms will fail. It sounds pretty obvious, but these are very common.

Another way diaphragms rupture is by operating the pump higher than maximum pressure ratings. Sometimes operators crank up the air pressure to get the pump to work faster. Doing this leads to leakage, bent inner plates and shaft, and of course, bulging and ripped diaphragms. 

When the diaphragm tears, fluid fills the air chamber, then it sprays out the muffler. Worse yet, if there's chemical compatibility issues, the air end of the pump is destroyed.

How To Prevent Ruptured AODD Diaphragms

Understanding that AODD pump spills are costly and preventable, I asked Crane’s sales engineer to give me some insight on what actions end users could take to prevent diaphragm failures. He had 4 tips to share.

Use A Regulator

cashco-back-pressure-regulator-b2.jpgRegulators are the #1 solution added to diaphragm pumps, but they rarely are. A regulator is to an AODD pump what a VFD is to motorized pumps. Regulators control the amount of airflow into the pump, regulating the stroke speed and extending the life of the diaphragm. Overpressurizing the diaphragm causes it to bubble out and fail faster than operation under normal conditions.

Air compressors are very expensive to purchase and operate over time. No one wants to add more compressors. The addition of small regulators for air operated diaphragm pumps could mean big savings on energy costs as well as the purchase price of a new compressor.

Deadheading/Running Dry

This was touched on earlier, but it bears repeating. Deadheading or running AODD pumps dry quickly destroys diaphragms. Enough said.

Use A One Piece Diaphragm

Synthesis-Thumb.jpgA one-piece diaphragm is a diaphragm that can stand up to more pressure than a standard diaphragm. It has dimples that allow the diaphragm to roll with excessive pressure and provide longer service.

Proper Pump Selection

As with any pump, a standard AODD pump does not suit all applications. Understand the fluid properties, the process, and the limitations of the pump doing the work.

For example, pumping thick fluid with a standard duty pump can lead to failure. Thick fluids tend to build up on diaphragms and will eventually cause failure. In this situation, consider heavy duty ball valve pumps or flap valve pumps.

Containment duty pumps are also suitable for processes where spills are unacceptable. Containment duty pumps don’t prevent against ruptured diaphragms, but they do protect against loss of fluid.

Containment duty pumps have an extra chamber filled with fluid between the “wet side” and the “air side” of the pump. When the diaphragm fails, fluid enters the containment chamber and the indicator on the outside of the pump changes color, alerting the user of the failure. The system continues to operate until maintenance is scheduled, and the best part – the fluid does not leak out, eliminating a major clean up.

Containment duty pumps cost more than standard or heavy duty air operated diaphragm pumps, but may be worth it depending on product and cleaning cost.

An ounce of prevention is worth a pound of cure, and in the case of AODD pump spills, this old adage couldn’t be more true. Proper pump selection, the use of regulators, and training operators to prevent overpressurizing can go a long way to preventing a diaphragm failure of epic (and very costly) proportions.

Having chronic AODD diaphragm issues? Ask us about it! We gladly provide technical assistance to businesses and municipalities in Wisconsin and upper Michigan.

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Sara Peters

Sara Peters

Sara leads Crane Engineering's blogging team, coming up with fresh stories and insights for our readers to apply to their every day work.

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