One of the most important things you must consider when you use a pump is not to dry run the pump (running without enough fluid). It will cause a lot of damage; thus, it is crucial to run pumps correctly and prevent them from dry running. But sometimes, we have no choice but dry run the pump; then we should find a pump able to dry run, so can rotary lobe pumps run dry?
Yes, if the seals are lubricated, rotary lobe pumps can run dry intermittently. Thanks to the design of the lobes, it does not touch each other and the housing, the temperature won’t rise much in a short time. The dry running time is up to 30 minutes, enough to self-prim liquids.
But other pumps with different structures, like centrifugal pumps and gear pumps, won’t allow dry runs. So in the next, we will share with you more information about this question.
What causes a pump to run dry?
Improper use:
1. Not filling liquid into the pump housing.
2. Unopened the suction valve.
3. The suction pipe is blocked.
We must avoid dry-run pumps by mistake; even if the pump can dry-run, it will waste energy.
Special task:
The pump needs to be drained because of the cold weather. (When liquid freezes, it expands and brake the pump.)
Empty a liquid tanker or hose pipe; a tanker truck pump usually does this.
What happens if water pumps run dry?
Most water pumps are not allowed to run dry; it will cause cavitation and overheat, damaging the pump parts, such as the casing, impeller, seals & bearings.
The mechanical seal is the first to be damaged; it will wear quickly and leak with continuous dry grinding. Then the casing and impeller will melt at a high temperature, especially the plastic pump. With the temperature rising constantly, other parts will badly damage too.
After the dry run, we have to repair or replace the pump; we don’t want that to happen at any time, so how do we protect our pump?
How do I protect my pump from dry runs?
Mechanical seals are the most easily damaged, so we’d better avoid lubricating them with the transfer liquid but design a cooling chamber for lubricating and cooling, like rotary lobe pumps.
Also, we recommend installing dry-running protection on the pump set; you can click here to learn more about this on Grundfos.
FAQs
Q: Can centrifugal pumps dry run?
A: No, it can’t, but generally, centrifugal pumps can be dry run without damage within 1 minute.
Q: Which pumps can be dry run continuous?
A: Diaphragm pumps and peristaltic pumps.
Q: What do I do after my pump runs dry?
A: Fill the liquid into the pump, then restart and check whether it works as usual.
Conclusion
We can dry run rotary lobe pumps intermittently, but we should never forget to add oils to cool and lubricate the seals. Unfortunately, most water pumps do not allow dry runs; they will get much damage even scrapped. So if your application requests dry-run pumps, please choose a pump able to dry run or install a dry-running protection device.
