The old coupling cannot be removed, the shaft extension is buried in the equipment, the caliper cannot be measured, the inner diameter cannot be measured, what should I do with the outer diameter and length? If you choose the wrong one and fail to install it, you will waste time and money!
Method 1: No need to disassemble the coupling (the motor + nameplate can be determined as long as it is a standard coupling)
Motor parameters
Motor power (kW), speed (r/min), motor model (copy the nameplate)
The motor model can directly check the motor shaft diameter and shaft extension length.
Slave end equipment
Reducer/pump/fan model, copy the nameplate, and check the diameter of the driven shaft.
Original coupling type
Look at the appearance: plum blossom / diaphragm / star / elastic pin / roller chain / drum tooth, etc., and see what kind of coupling it is.
Working conditions
Positive and reverse? Shock load? Continuous operation? Whether there is displacement (whether the alignment deviation is large or not), the provision of these working conditions is conducive to accurate selection.
Method 2: What should I do if I really can’t get the shaft diameter?
Method 1: Measure the exposed part of the motor shaft head
If the shaft head is exposed: Use a rope to wrap a circle around the shaft to measure the circumference, ÷3.14≈shaft diameter.
Example: circumference 62.8mm, shaft diameter≈20mm. Note: What is measured is the shaft body, not the keyway protrusion.
Look at the keyway: roughly judge the key width (8/10/12/14mm, common shafts have standard keys), and take a photo
Method 2: Take photos of old couplings + count appearance characteristics
Take photos of the complete side and end faces;
Count the number of elastomer flaps: Plum coupling 4 flap / 6 flap / 8 flap;
Check the approximate outer diameter: find a reference object for comparison;
Look at the gap between the two half couplings. It can only be used as a reference and cannot be 100% guaranteed.
Method 3: Torque calculation (the most important thing is not to just look at the shaft diameter)
The first thing to consider when selecting a coupling is the torque, followed by the shaft hole. Select coupling nominal torque > calculated torque. Many people choose a small torque when the shaft diameter is aligned, and it will break after a short time of use.
In addition, there are two points that are easily overlooked when choosing a coupling: shaft extension length and keyway. If these two points are not suitable, they cannot be installed.
Tips for purchasing couplings of unknown size: You can reserve a margin and buy them for on-site boring/reaming, which is suitable for non-standard shafts of old equipment. The cost is a little more processing fee, but it will not be scrapped directly (wouldn’t the loss be greater if it is scrapped directly?)
(Source: Defeng Transmission)