If there’s one thing a plant maintenance manager can’t tolerate, it’s downtime.
Production stoppages mean lost revenue. To avoid downtime, plant personnel must keep the plant’s systems and machinery running smoothly and handle all planned maintenance, upgrades and emergency repairs as quickly as possible.
Fortunately, one of the common pieces of equipment in plants—Air-operated double-diaphragm (AODD) pumps—is designed to make maintenance simple and cost-effective. Still, an experienced plant maintenance manager will look for ways to optimize AODD pump performance to keep downtime to a minimum and maximize efficiency.
Before steps to increase reliability can be taken, it’s best to know the basic components of an AODD pump:
In this AODD pump diagram, A and B are the diaphragms, 1–4 are the ball valves and I and O the inlet and outlet ports. An AODD pump uses compressed air to power the repeated back-and-forth motion of the diaphragms, which are mounted on C, a connecting rod. This continuous motion forces liquid out of one chamber for discharge while the other chamber fills with liquid.
Tips for Maximizing AODD Pump Efficiency
1. Choose the Right Pump Position Within the System
A pump's location within the system is critical to its performance and longevity. This is because AODD pumps can be used in three main ways:
- As suction lift: AODD pumps are self-priming and can pull a suction lift up to 32’ (9.8m), so the pump must be placed above the fluid, which is then pulled into the unit. Ideally, the length of the suction pipe is as short as possible. This will help with priming and reduce stress on the pump’s diaphragms.
- As submerged suction: AODD pumps can be submerged in the fluid that is being pumped. Before submersion, however, you need to ensure that all pump materials are compatible with the fluid and that the pump's air exhaust is above the fluid level. You also want to make sure that a suction screen is used if solids are present in the fluid. This ensures that solids larger than the pump can handle (pass) don't enter the unit.
- As flooded suction: In this scenario, there is fluid pressure coming into the AODD pump and the pump is below the fluid being pumped. It's important to place the pump as close to the fluid vessel as possible and reduce the length of the suction line. This will reduce diaphragm stress and valve ball chatter. Controlling the fluid pressure coming into the suction side of the pump is also important; ideally, it should be less than 10’ of pressure. If the inlet pressure is greater than 10’ (3.04 m), you should consult the pump manufacturer.
2. Select the Right Pump Construction Materials
AODD pump material selection will increase the reliability, performance and life of a pump, decreasing downtime and increasing profitability. However, these fluid characteristics must be considered before choosing a pump's material:
- Specific gravity (product weight)
- Overall chemical compatibility
Understanding the pump's external environment is also critical to an AODD pump's longevity. For example, if its environment contains fumes, the entire pump, including the air side, must be compatible. If the pump will be exposed to UV light from the sun, plastic pumps may not be ideal. And, if you're pumping abrasive material, you may want to choose harder casting and seat materials. In every case, you should consult the pump's manufacturer for details.
3. Size Up for Longevity and Efficiency
According to the Hydraulic Institute, pumping systems account for over 40% of industrial energy use. Energy saved equals dollars saved when it comes to powering pumps.
AODD pump up-sizing is one strategy to reduce AODD pump energy consumption. When you increase the size of the pump for the same desired flow, it increases the pump's efficiency—ensuring the maximum volume of liquid is pumped per amount of compressed air consumed.
In other words, if a pump is running to the far right hand of the curve (i.e., the pump is running flat out) to produce the desired flow rate, going up one pump size can allow you to shift the performance point to the left on the curve. This means the pump will cycle less and you'll reduce energy consumption and extend pump longevity while getting the same desired output.
Displacement per stroke (or cycle) is also important to note, as there's a direct correlation in pump longevity and efficiency. In many cases, choosing a pump with greater displacement per stroke will reduce wear on the unit.
Using a larger unit can also reduce wear when pumping abrasive liquids, such as ceramic slip. By upsizing the AODD pump and running it slower, you reduce fluid velocity, which, in turn, reduces abrasive wear.
4. Consider the Compressed Air Supply
Air filters/regulators play a crucial role in the performance of AODD pumps by preventing wet and contaminated air from entering the pump. When outside air is drawn into the compressor, it naturally contains moisture that can freeze when it expands inside the pump. The resulting ice can cause the pump to stall. Air filters/regulators protect the air valve of the pump by removing solids and liquid contaminants from the air lines while providing additional precise pump control.
The air filter/regulator can also help you start the pump in a gradual "soft" manner, which creates less stress on the pump's components.
5. Start the Pump Slowly When Pumping Fluids With Settling Solids
AODD pumps are designed to handle solids and slurries. When handling fluids containing settling solids, it's important to start the pump up slowly to allow the settled-out solids to evacuate prior to the pump being operated at full flow and pressure. If this doesn't happen, the settled solids can cause damage to pump components.
6. Control Pulsation From Pumping
Installing diaphragm pump surge suppressors virtually eliminates undesirable pulsation from pumping. It also provides virtually pulse-free discharge flow for steadier pressure with less system vibration (vibration can cause damage to the discharge system and loosen connections) and noise.
7. Install Liquid Level Controllers
Completely air-driven (i.e., pneumatic) and ATEX-approved for simple, safe pump control, liquid level controllers protect AODD pumps from inefficient dry running conditions. They essentially turn pumps on and off for intermittent applications.
Common applications for liquid level controllers are:
- Fluid Transfer
- Tank Filling
8. Choose Replacement Parts Wisely
When in need of replacement parts, order directly from the pump's manufacturer. This reduces downtime and multiple maintenance sessions, as manufacturers make parts specifically to fit their own pumps. Using replacement parts from a different source also will invalidate your pump’s warranty.
One-Stop Shopping—From Sales to Maintenance
AODD pumps are an investment that will pay off with proper installation and maintenance.
For almost 40 years, Versamatic has been one of the largest and trusted manufacturers of world-class, AODD pumps and replacement parts for a broad, global customer base.
Count on the consistency, reliability and trouble-free operation of Versamatic’s bolted metal, bolted plastic and clamped metal AODD pumps offered in a wide range of sizes and flow rates.
A full line of specialty products and support from a team of design and engineering experts with decades of pumping experience keeps your process running smoothly and efficiently. Reach out to find the closest Versamatic AODD pump distributor today.