AODD Pumps: A Solution to Centrifugal Pump Problems
Centrifugal pump problems making you frustrated?
troubleshooting your centrifugal pump?
An ARO air-operated diaphragm pump may be your best solution.
Air-operated double diaphragm (AODD) pumps can be a more reliable choice than centrifugal pumps in many situations. A centrifugal pump design is simple, with easy to understand pumping principles. But they are one of the most difficult industrial pumps to choose for an application.
There are many inter-related design and set up variables that must be correctly determined for a specific application in order for a centrifugal to work as designed.
If the pump and process are set up properly, the pump works very well. However, even small changes to process conditions — flow, pressure, fluid viscosity, NPSHa, or particle level — can dramatically reduce the efficiency and reliability of the centrifugal pump. Rarely, if ever, are these pumps rechecked for viability after any process changes.
Centrifugal pumps are often a source of chronic maintenance and reliability problems. They are designed to operate near a single operating point or Best Efficiency Point (BEP). Moving process conditions even 10% from this point can cut the reliability in half and dramatically lower the efficiency.
How often do process engineers revisit the pump configuration when they make a change to process? Answer: Very rarely, if ever.
An AODD pump is easier to specify for an application and can run reliably across the entire rated operating range, not just a single point.
Air Operated Diaphragm Pumps can run dry, stall, and significantly reduce the possibility of cavitation during operation.
ARO® AODD pumps have a broad operating window allowing customer flexibility to make changes in their process without changing the pump.
AODD Pump Advantages
AODD pumps have a wide variety of advantages that can solve many common centrifugal pump problems, including:
- Deadheading without damage or energy use
- Wide reliable pressure and flow operating range
- Greater flow control
- More broad chemical compatibility and/or viscosity range
- Smaller footprint, size and weight
- Lower capital investment
- Process Ready standard on EXP Series
Centrifugal Pump Problems & AODD Solutions
If any of the applications or conditions outlined below are part of your process, an AODD pump probably should be considered.
These are five common issues or applications where an AODD pump could be a better solution.
- Shear Sensitive Liquids – Pumps tend to shear liquids more as speed is increased, and centrifugal pumps are high speed pumps. This makes an AODD pump a better choice to handle shear sensitive liquids. Diaphragm pumps operate at lower speeds, are gentler on products, and are usually preferred in these types of applications.
- Suction Lift Applications – AODD pumps are capable of creating a suction lift. Standard ANSI centrifugal pumps do not create a vacuum and cannot create a suction lift. Diaphragm pumps are the logical choice when a suction lift is required.
- Variations in Flow – Centrifugal pumps do not operate well when being run too far off the middle of the curve. If a lower or higher flow is needed, efficiency is reduced or can result in cavitation damage, shaft deflection, and premature pump failure. An AODD pump is well suited for varying flow.
- Variations in Pressure or Viscosity – AODD pumps have stall capability. If pumping pressure increases in an application, an AODD pump will easily dead head, or stop pumping. Meanwhile a centrifugal pump will continue to build pressure until something fails, the pump is severely damaged, or both. Some liquids can vary in viscosity due to temperature or chemical reaction. A rise in viscosity alter the flow rate, efficiency, and increase pressure. AODD pumps are the right choice for applications with viscosity fluctuations.
- Metering – AODD pumps are an ideal choice for metering applications. They deliver constant flow, allowing them to easily meet process requirements.
Additional centrifugal pump issues that may be better addressed with an AODD pump:
- Unable to stall or deadhead without damage
- Narrow efficient operating point
- Shaft seal failure (leaking along rotating shaft)
- Rapid impeller wear due to abrasives, corrosives, or cavitationInternal corrosion due to fluid incompatibility
- Overheating due to low flow (critical with magnetic drive)
- Not self-priming (must have a flooded inlet or filled with fluid)
- Surge, or random air pockets generated in the line