Air-operated double-diaphragm (AODD) pumps are employed in an extensive number of industrial applications and across industries including petrochemical, pharmaceutical, water management, semiconductor, oil and gas, painting and coating and beyond. AODD pumps are typically used in transfer applications and can handle a variety of materials, including sludges, slurries and abrasive and shear-sensitive fluids. Their one-of-a-kind shape makes them excellent for transporting highly abrasive or viscous materials. While they are rugged, dependable and simple to maintain, they may be loud and prone to icing, and they are best suited for low-pressure applications.
How Does an AODD Pump Work?
An AODD pump is a positive displacement pump powered by compressed air. The compressed air is transferred between chambers through a connected shaft that enables the chambers to move in unison. This back-and-forth action pulls liquid out of one chamber and into the discharge pipe while simultaneously filling the other chamber with liquid. AODD pumps can achieve flow rates of up to 280 gallons per minute (gpm) (1,060 liters per minute [lpm]). The flow rate can be obtained by simply increasing the air pressure or the discharge head.
What Are the Qualities of an AODD Pump?
Due to the absence of internal seals and moving components that require lubrication and cooling, an AODD pump can operate dry indefinitely without causing damage. A clean compressed air supply is required for operation, and pumps typically pump fluids at pressures equal to or lower than that of the available air supply. Because they are powered by compressed air rather than electricity, the simple design of AODD pumps makes them easy to operate and cost-effective to repair. Although AODD pumps are often regarded as the workhorses of the pump world, there are several factors that can impede the efficiency and operational life of an AODD pump.
5 Common Mistakes Related to the Installation, Operation & Maintenance of AODD Pumps
1. Using components that are not abrasion resistant
When selecting an AODD pump for a certain application, some pump components can make a significant difference in overall performance and the mean time between failure (MTBF). When pumping abrasive fluids, it is important to consider using components that are designed using material resistant to abrasion. Manufacturers often replace traditional rubber valve seats with ones made with more abrasion-resistant, high-performance polymers in order to lessen the wear associated with abrasive applications.
2. Pumping a substance that is not chemically compatible with the pump’s components
Before selecting an AODD pump, it is important to have a solid grasp of the chemical properties. Be certain the fluids being transferred are chemically compatible with the materials used to manufacture the pump. This comprises elastomers, castings and potentially hardware in the event the pump is going to be submerged. Because safety is a main concern with many different chemicals, it is crucial to select a pump made from materials that are compatible with the chemical being moved through the system.
3. Not considering operating temperature
Another important factor that is often overlooked is the operating temperature. Even though AODD pumps can handle fluids as hot as 220 F (104 C), elevated temperature can have adverse effects on the performance of pump materials. Some materials can degrade, crack, swell or disintegrate at higher temperatures, reducing corrosion resistance and causing early failure. Lower temperatures reduce diaphragm flexibility. Each diaphragm material has a specific temperature range for operation. Maximum flex life (the diaphragm’s predicted life span before replacement) cannot be expected if the pump is used at severe temperatures. Internal pump components may be qualified for low or high temperatures, but it does not mean the pump body material is or vice versa. When configuring an AODD pump, check all components’ temperature ratings. AODD pump manufacturers openly publish the temperature limits of their materials.
4. Lack of consideration for compressed air supply
The quality and pressure of the air may affect the life of an AODD pump more than anything else. After all, compressed air is how these pumps get their power. Just like dirty air can affect how well a pump works, air pressure can make the difference between a pump that works at full capacity and one that does not work at all or does not work well. How fast an AODD pump works and how much flow it makes are both controlled by the air pressure. If the pump is getting more pressure than it needs, it will cycle quickly, which leads to inefficient operation, more wear on the pump and premature failure. Air filters and air regulators help ensure the air is clean and maintained at the right pressure.
The fluid must have sufficient time to enter and exit each fluid chamber, and the valve check balls must seat properly to achieve a seal. Ensuring proper air pressure will keep fluid flowing at the optimal rate to ensure each stroke is completed without backflow, hence enhancing the performance of the pump.
5. Pump fittings that are not sized correctly
Matching flow and pressure ratings to the flow and pressure requirements of a process is an important part of pump sizing. Ensure the fluid inlet and output piping/fittings are at least as large as the pump’s connection size before fluid begins to flow through the pump. Doing so during installation will optimize the efficiency of the pump. In simple terms, this means for a 2-inch pump installation, connecting it to 2-inch or larger plumbing is the best option. If the pipe is smaller than the pump, fluid suction will be restricted, affecting pump flow, efficiency and diaphragm life negatively. Proper sizing is critical for pump longevity and optimal performance.
With these five factors under consideration, AODD pump users may achieve the highest overall pump output efficiency. In order to produce successful output, it is necessary to ensure smooth operations and a regular schedule while minimizing downtime to maximize productivity.