When installing a pump, it’s crucial to ensure the pump rotation is correct. Incorrect rotation can lead to irregular use or even damage to the pump. However, some pumps, like the rotary lobe pump, can operate in reverse, reducing potential issues. So, are rotary lobe pumps reversible? The answer is yes.
The Reversibility of Rotary Lobe Pumps
Yes, rotary lobe pumps can be reversed continuously. They possess a symmetric and valveless structure, allowing for quick reversal by simply changing the direction of the engine’s rotation. However, it’s important to ensure the piping system is suitable for reverse operation.
Why Reverse a Pump?
The most common reason for reversing a pump is a power failure, which can cause the engine to rotate in reverse. It’s essential to run the engine in the correct direction for your system. If you’re unsure, consult the machine’s manual or contact the manufacturer.
Another reason for pump reversal is a malfunctioning or uninstalled check valve. When a pump stops, the liquid may backflow, causing the pump to reverse. A check valve is necessary to protect the pump from backflow and to prevent dry run. For more details on dry run, please read this article about dry run pumps.
Lastly, operational needs may require pumps to run in both directions, such as when loading and unloading tanks. In these cases, a reversible pump is necessary.
Which Pumps Can Reverse?
Most positive displacement pumps (PD pumps) can operate in reverse. However, there are exceptions, such as gear pumps with built-in relief valves, which cannot reverse without modifying the valve. Most centrifugal pumps, due to their built-in valves, cannot run in reverse. Some centrifugal pumps will still work in reverse, but their efficiency will be significantly reduced.
What Happens When a Centrifugal Pump Rotates in Reverse?
In some centrifugal pumps, the impellers are threaded, so they will unthread and be damaged when run in reverse. For other centrifugal pumps, running in reverse won’t cause damage, but the efficiency will be significantly reduced.
Q: How do I check pump rotation?
A: Rotation is indicated on the head of the pump; you’ll see an arrow going counter-clockwise.
Q: Can a motor be reversed? And how to reverse it?
A: Yes, motors can run in both directions by switching the wire connections.
Rotary lobe pumps can run in reverse without harm and without impacting performance. They are an excellent option for systems that require a pump to run in both flow directions. Other pumps might be damaged or perform poorly when reversed. It’s necessary to confirm whether your pump can reverse with the manufacturer before installing it.