Common AODD problems running crude.

Over the years we have noticed one recurring theme when crude is run through an AODD pump. Premature failure of diaphragms. These problems are always attributed to three situations: poor maintenance, improper use, and running too cold.

 

After each use, your pump must be rinsed with a solvent to remove any sticky residue from the diaphragm. This is a simple process, yet countless labs fail to do this. When the diaphragms sit with crude residue, eventually the solvent evaporates, and a strong bond is created between the chassis and the diaphragm. When the pump is used again, it is possible to either rupture a diaphragm or even to bend a shaft or damage the pneumatic exchanger because the diaphragm is glued to the pump case.

 

Another problem that reduces diaphragm life is running the diaphragm dry. Though these are meant to operate dry and create a vacuum, I find many users rev up the pump to create a strong vacuum. This prematurely ruptures the diaphragms and results in a short life. Slow down the pump when there is no liquid in the case. Once fluid is flowing, proceed as required.

 

Finally, exceeding manufacturer-recommended operating temperatures will surely result in premature failure. To avoid this, ensure your pump model will tolerate the temperature you require, and the diaphragms you choose are compatible both to the temperature and chemicals you are pumping. For cold ethanol, we recommend you use Santoprene diaphragms.

 

Another problem we see is either damage to the pneumatic exchanger or loss of performance of the pump due to the pneumatic exchanger. The symptoms will be either a slow or slowing pump where your pump runs fast and then slows, or your pump briefly runs and then stops. The cause is the supply of compressed air.

 

A Water Vapor Filter, Particulate Filter, and Regulator must be used somewhere between the compressed air tank and the pump itself. If you have long thick pipes in your lab, we recommend the filter be close to the pump; if you are running hoses then the filter can be closer to your compressor. Rarely have I seen a decent Filter that comes supplied with a compressor, so don’t rely on one. Also, a vapor filter is rarely included with compressors so you must purchase one.

 

A particulate filter is necessary, as small particles may clog or damage a pneumatic exchanger. Scale, rust and other particles may accumulate over time in your compressor tank and your pipes. For this reason, it is important to ensure there is no debris in your air.

 

There is lots of water vapor in the air, and as it is compressed will tend to condense. Water itself is not an issue for the pumps, but the conditions of operation create the problems. Many customers run crude at below-freezing temperatures. As the exchanger freezes, all that water that came out of the air will freeze inside your pump and create havoc. The solution is a high-quality compressed air dryer.