Couplings connect the pump shaft to the motor/engine, transmitting torque while accommodating misalignment, vibration, and thermal expansion. The right coupling improves efficiency and reduces wear.
Design: Solid connection with no flexibility.
Applications: Precision-aligned systems (rare in pumps due to misalignment risks).
Pros:
Simple, low-cost.
Zero backlash (good for synchronous drives).
Cons:
Requires perfect alignment (prone to shaft damage).
No vibration damping.
Design: Uses rubber/spider elements to absorb shock.
Types:
Jaw Coupling (Lovejoy type) – Common in small pumps.
Tire Coupling – High misalignment capacity.
Pin & Bush Coupling – Durable, moderate flexibility.
Pros:
Low maintenance, dampens vibration.
Handles minor misalignment.
Cons:
Elastomer wears over time.
Limited torque capacity.
Design: Meshed gears with lubrication for high torque.
Applications: Heavy-duty pumps (API 610, refinery).
Pros:
High torque capacity.
Tolerates slight angular/parallel misalignment.
Cons:
Requires lubrication.
More expensive.
Design: Steel grid between two hubs (flexible but strong).
Applications: Medium-to-heavy-duty pumps.
Pros:
Good vibration damping.
No lubrication needed.
Cons:
Slightly heavier than elastomeric types.
Design: Thin metal discs flex to accommodate misalignment.
Applications: High-speed, precision pumps (API 610).
Pros:
No backlash, high precision.
Maintenance-free (no lubrication).
Cons:
Expensive.
Sensitive to misalignment limits.
Design: Roller chain connects two sprockets.
Applications: Low-cost industrial pumps.
Pros:
Easy to install/replace.
Handles moderate misalignment.
Cons:
Requires lubrication.
Noisy.
Design: Uses oil to transmit torque (slip at startup).
Applications: Large pumps needing soft starts (mining, power plants).
Pros:
Smooth torque transmission.
Protects against overload.
Cons:
Efficiency losses (slippage).
Higher maintenance.
| Factor | Recommended Coupling Type |
|---|---|
| High Torque | Gear, Grid |
| Precision Alignment Needed | Disc/Diaphragm |
| Misalignment Expected | Elastomeric, Grid |
| Vibration Damping | Elastomeric, Fluid |
| Maintenance-Free | Disc, Elastomeric |
| API 610 Compliance | Disc, Gear |
| Low Cost | Jaw, Chain |
Check for:
Wear (elastomer cracks, gear tooth damage).
Lubrication (gear/chain couplings).
Misalignment (vibration, overheating).
Looseness (bolt tightness).
Common Failures:
Elastomer degradation (hardening/cracking).
Coupling slippage (improper torque).
Shaft fretting (misalignment).
For small pumps: Jaw/elastomeric couplings (cost-effective).
For API/high-speed pumps: Disc or gear couplings (precision).
For heavy-duty applications: Grid or fluid couplings.
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