Pneumatic Double Diaphragm Pumps are used in transfer applications due to their straightforward design, which makes them easy to operate and maintain. To get optimal performance, end users must properly install and operate these pumps. Common concerns may be resolved in minutes with the proper information.
Here are six short actions to assist you in resolving typical issues of Pneumatic Double Diaphragm Pumps:
1. Check the inlet air line's size and pressure.
The most typical mistake that consumers make when installing an AODD pump is using an air connection that is too small. Using an air connection that is too small can deprive the pump of the fuel—compressed air that it requires to function properly. Upgrading to a bigger air line is a simple remedy that just takes minutes.
Pneumatic Double Diaphragm Pumps exist in a variety of forms and sizes, depending on the application and fluid specifications. To function at maximum capacity, bigger AODD pumps (1-inch or greater) require more compressed air and larger air lines than smaller pumps.
The manufacturer's installation and operating handbook specifies the proper air line size for a pump. To determine the appropriate AODD intake air line size, match the hose size to the air valve's inlet port size.
Inlet air pressure is also important in maximizing the performance of a pump. Diaphragm pumps work on a one-to-one ratio, which means that the pressure of the input air supplying the pump is directly proportional to the fluid pressure at the exit. For example, if the intended output pressure of a 1-inch, 50-gallon-per-minute (gpm) pump is 100 pounds per square inch (psi), the inlet air pressure entering the pump's air valve must be at least 100 psi.
System backpressure and fluid viscosity will influence output fluid pressure. Too little backpressure may cause the pump to operate inefficiently since the ball checks may not be completed as quickly. If the fluid pressure exceeds the air pressure, the pump may stall.
To adjust an AODD pump's performance (flow and pressure), install an air regulator assembly to regulate the incoming air pressure. The most common Pneumatic Double Diaphragm Pump installation difficulty may be solved by installing the right air line size and an air regulator.
2. Check for muffler icing and limitations.
Pneumatic Double Diaphragm Pumps may create significant decibel levels at full speed, which is why mufflers are advised during installation. The AODD air motor requires compressed air to function. Rapid temperature variations occur as compressed air enters the air valve and travels through the pump center portion before exiting via the muffler. The air temperature at the muffler exhaust is below freezing, which can lead to ice concerns that are typical in humid conditions.
Erratic pump operation, excessive moisture levels in the input air, and visible frost on the exterior of the muffler are all signs of an icing problem that is reducing pump performance. Here are proposed strategies to resolve these issues:
Reduce the air pressure at the pump.
Increase the pump size to allow for lower speeds (i.e., lower air pressure).
An exhaust port tube transports exhaust air to a faraway site.
To collect condensation, install an air line filter that includes a water catcher and a drain.
Install an air line heater to bring the exhaust air temperature above freezing.
Use an air compressor dryer to adjust the pressure and dew point temperatures.
3. Inspect sealing surfaces for leaks.
Leakage is a prevalent concern across all pump types. A few easy fixes can ensure that fluid remains in a Pneumatic Double Diaphragm Pump. First, pumps, particularly plastic pumps, should be torqued to the manufacturer's suggested rating. Materials relax with time—a process known as cold flow—which can cause sealing surfaces to loosen and generate leak routes. Refer to the pump handbook for torque levels, and adhere to the bolting patterns to avoid the risk of leaking.
The reuse of polytetrafluoroethylene (PTFE) O-rings is another source of leakage at sealing surfaces. One disadvantage of PTFE is its resilience. Once squeezed, a PTFE O-ring cannot regenerate its former shape. When maintaining a Pneumatic Double Diaphragm Pump, replace all of the pump's PTFE O-rings.
After correctly torqueing the pump according to manufacturer guidelines and replacing all sealing O-rings after service, the AODD pump should be leak-free. Save time on subsequent rebuilds by replacing the PTFE O-rings when the pump is rebuilt.
4. Ensure that the tubing and pipes are the right size.
Pump input and exit fluid port widths vary according to the flow rate required. The inlet and output hose diameters must correspond to the pump's size. One major problem is the potential of cavitation, which can raise repair and maintenance expenses. It is quite easy to change the size of the tube and pipe after installation. Knowing the right size at installation saves time and effort when making later modifications.
For example, if a 1-inch pump is coupled to a half-inch intake line, it will be unable to run at full capacity due to the possibility of cavitation. This danger grows considerably as the required fluid viscosity increases. To avoid cavitation, the 1-inch pump should be equipped with 1-inch input and output hoses.
It is also suggested that a Pneumatic Double Diaphragm Pump be fitted with a flexible inlet/outlet connection rather than a hard piped connection. As pump speed increases, so does vibration, increasing the danger of loosening a hard plumbed connection and causing leakage.
5. Reduce the pump speed to prime.
AODD pumps are often used when self-priming is necessary. The AODD pump pulls fluid by creating a low-pressure zone inside the fluid bowls that is less than atmospheric pressure (14.7 psi). If the air pressure provided to the pump is too high, the pump will turn over too rapidly, leaving insufficient time for the fluid to be sucked into the pump.
To resolve this priming issue in a matter of seconds, slow down the pump by lowering the air pressure entering the air valve. After the pump speed has been decreased and the fluid has had enough time to enter the pump, raise the air pressure and run the pump faster.
Conclusion
Though Pneumatic Double Diaphragm Pumps are noted for their "set it and forget it" functionality, they must be properly maintained. AODD pump components, like any other piece of equipment, can fail prematurely if not used properly. To minimize unforeseen downtime, choose a pump manufacturer that provides excellent technical support.
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