The impeller attaches to the shaft and imparts energy to the fluid being pumped.
Impellers are available in open, semi- open and closed designs:
Pump efficiency is maintained by setting a close clearance between the impeller vanes and the volute or back plate.
Since there is no shroud to strengthen the vanes, their use is often limited to small inexpensive pumps
Some of these semi-open impellers have pump out vanes on the back of the shroud that reduce the pressure on the back of the shroud and prevent foreign matter from lodging in back of the impeller, interfering with its operation.
Closed impellers are sensitive to clogging with solids so their use is limited to the pumping of reasonably clear liquids.
Oil refineries use closed impellers because of the problem of maintaining a close tolerance between a semi-open impeller and the pump volute. Explosive products would ignite if the impeller came into contact with the volute, but in the closed impeller version soft wear rings would make the contact.
See also :
- On February 16, 2018