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Couplings
- a device used to connect two shafts together at their ends for the purpose of transmitting power
- primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both
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Considerations when choosing a coupling
- 1. temperature
- 2. torque and power rating
- 3. RPM4. S.F.; type of load (shock, fluctuating, etc.)
- 5. misalignment issues
- 6. purchase, installation and maintenance costs
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TYPES of MISALIGNMENT
- 1. Angular misalignment
- 2. Offset misalignment
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8 types of couplings
- Clamp or sleeve coupling
- Modified clamp coupling
- Spider or jaw and slider coupling
- Chain coupling
- Grid-flex coupling
- Gear coupling
- Para-flex or elastomeric coupling
- Fluid coupling
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sleeve coupling
- basic type of coupling
- consists of a pipe whose bore is finished to the required tolerance based on the shaft size
- a keyway in made in the bore in order to transmit the torque by means of the key
- Two threaded holes are provided in order to lock the coupling in position
- ADV: Rigid coupling for transmitting high torques at high speeds
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clamp coupling
- sleeve used in this type is split from one side
- shafts are entered and keyed to this sleeve and then split sides are screwed together
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Spider or jaw and slider coupling
- Both half of the couplings have three shaped lugs
- When the coupling halves are fitted together the lugs on one half fit inside the spaces
- between the lugs on the other side
- When the coupling halves are fitted together the lugs on one half fit inside the spaces
- between the lugs on the other side
- The drive is by the lugs transmitting the torque
- through the rubber spider spacer
- DISADV: only used for low power drives
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Chain coupling
- Chain Couplings transmit torque through two hubs with hardened sprocket teeth and a double width roller chain
- ADV: High torque capacity and least expensive coupling in the medium torque range
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Grid-flex coupling or Grid Lign
- use two slotted hubs with a steel grid running between them to transmit torque
- The coupling flexes by allowing the grid to slide along the slots in the hubs
- ADV: Torsionally flexible and resilient - vibration reduction up to 30%
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Gear coupling
- gear coupling is a mechanical device for transmitting torque between two shafts that are not collinear
- consists of a flexible joint fixed to each shaft
- two joints are connected by a third shaft, called the spindle
- ADV: coupling is capable of high speeds and high power capacity = high torque
- DISADV: it requires lubrication
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Para-flex or elastomeric coupling
- employ a molded, non-lubricated elastomeric
- flexing member loaded in shear
- ADV: Finished Bore Flanges offer extra bore capacity that allows smaller coupling selections
- ADV: designed to accomodate concurrent angular, parallel, and axial misalignment and ensure fast, easy installation
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Fluid coupling
- When the motor is rotated, the fluid is picked up in the vanes of the impeller and thrown outwards, across the gap, towards the vanes of the runner. As a result of the fluid kinetic energy, the runner begins to rotate and drive the driven machine
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