Wkcoo
Mechanical
- Dec 10, 2020
- 36
Hi all, would like to learn if the radial load that arises from keyed coupling hub on pump shaft is significant enough to be accounted into pump bearing sizing.
My understanding is coupling hub on a general centrifugal pump shaft usually has around half mil clearance fit, so I assume the torque will be transmitted from coupling hub to the pump shaft through the single key which is sitting at shaft radius, and negligible torque transmitted through friction due to the clearance fit. Say torque is T, shaft radius is R, then radial force = T / R, which will affect the bearing reaction force.
I did a fictitious example calculation which seems to show too high of a force at coupling hub location.
Take a 200 HP pump running at 3000 RPM with 2 inch shaft diameter, it will experience torque of 4200 lb-in and radial force of 4200 lb.
Reading through references found from bearing catalog etc usually just account for radial force and axial thrust that arise from the impeller itself.
is there something wrong in my assumption or this needs to be accounted for?
My understanding is coupling hub on a general centrifugal pump shaft usually has around half mil clearance fit, so I assume the torque will be transmitted from coupling hub to the pump shaft through the single key which is sitting at shaft radius, and negligible torque transmitted through friction due to the clearance fit. Say torque is T, shaft radius is R, then radial force = T / R, which will affect the bearing reaction force.
I did a fictitious example calculation which seems to show too high of a force at coupling hub location.
Take a 200 HP pump running at 3000 RPM with 2 inch shaft diameter, it will experience torque of 4200 lb-in and radial force of 4200 lb.
Reading through references found from bearing catalog etc usually just account for radial force and axial thrust that arise from the impeller itself.
is there something wrong in my assumption or this needs to be accounted for?
