Magnetic Couplings
Magnetic couplings are the heart of mag drive pumps, delivering sealless, leak-free torque transfer for hazardous or high-purity liquids. Learn benefits and selection.
Magnetic Couplings for Mag Drive Pumps
Leak-free power transmission for hazardous, valuable, or ultra-pure fluids.
Magnetic couplings are the core technology behind magnetically driven (sealless) pumps. They transfer torque from the motor to the pump impeller without a mechanical shaft seal, using a pair of magnetic rotor assemblies separated by a sealed containment shell. This design removes the primary leakage point found in conventional pumps, making mag drive systems ideal for applications where safety, environmental protection, product purity, and uptime are critical.
How a Magnetic Coupling Works
A mag drive coupling consists of three main elements:
- Outer magnet assembly (drive rotor)
Mounted to the motor shaft, it rotates with the motor. - Inner magnet assembly (driven rotor)
Connected to the impeller shaft inside the pump. - Containment shell (barrier can)
A hermetically sealed, non-magnetic barrier that separates the pump fluid from the atmosphere.
As the motor turns the outer magnets, the magnetic field passes through the containment shell and synchronously spins the inner magnets, driving the impeller. Because there’s no dynamic seal, the pump remains completely sealed to atmosphere.
Why Magnetic Couplings Matter
True sealless integrity
Eliminates mechanical seal failures and the risk of fugitive emissions — essential for toxic, flammable, corrosive, or odorous liquids.
Improved safety & compliance
Supports safer plants and helps meet environmental and regulatory requirements (e.g., zero-leakage mandates, ATEX zones where applicable).
Reduced maintenance
No seal flush systems, seal replacements, or associated downtime. This lowers total cost of ownership in continuous or hard-to-access services.
Product purity
Ideal for ultra-pure process fluids because there is no seal wear contamination and no need for external barrier fluids.
Key Design Considerations
Torque capacity
Magnetic couplings must be sized for the required torque at duty point, plus safety margin for process upsets. If torque demand exceeds coupling limit, the magnets can decouple (slip) to protect the pump.
Containment shell material
The shell must be:
- chemically compatible with the fluid
- mechanically strong at pressure/temperature
- low-loss for magnetic transmission
Common options include stainless steels, Hastelloy, titanium, or engineered thermoplastics depending on duty.
Eddy current losses
Metal containment shells can generate heat from eddy currents as the magnetic field rotates. Modern designs minimise this with optimized materials, thin-wall shells, and hydraulic balancing. Managing shell temperature is vital for high-temperature or low-lubricity fluids.
Internal bearing and lubrication
Because mag drive pumps are sealed, the internal bearings are lubricated by the pumped fluid. Correct selection must consider:
- viscosity
- lubricity
- solids content
- vapor pressure
For poor-lubricity fluids, designs may use sleeve bearings, silicon carbide, carbon graphite, or specialty composites.
Typical Applications
Magnetic couplings in mag drive pumps are widely used in:
- Chemical processing (acids, alkalis, solvents, chlorinated compounds)
- Pharmaceutical and biotech (ultra-pure and sterile transfer)
- Petrochemical and refining (toxic and high-value hydrocarbons)
- Battery materials and specialty chemicals
- Water treatment with aggressive dosing chemicals
- Food & beverage additives where purity is critical
Anywhere a seal leak could cause safety risk, product loss, or environmental harm, mag drive couplings provide a proven solution.
Common Features & Options
Depending on application, mag drive coupling systems may include:
- Rare-earth magnet assemblies for high torque density
- Dry-run protection and temperature sensors
- Containment shell cooling paths
- Fail-safe decoupling capability under overload
- ATEX-rated configurations where hazardous area compliance is required
- Corrosion-resistant wet ends in PP, PVDF, ETFE, or high-alloy metals
Magnetic Coupling vs Mechanical Seal (Quick Comparison)
| Feature | Mag Drive Magnetic Coupling | Mechanical Seal Pump |
|---|---|---|
| Leakage risk | Near-zero (sealless) | Always a potential failure point |
| Maintenance | Low | Moderate to high |
| Safety/environment | Excellent | Depends on seal system |
| Best for | Hazardous, corrosive, ultra-pure fluids | General duties, wide fluid range |
| Dry-run tolerance | Limited (needs protection) | Usually better (depending on seal) |
Get the Right Magnetic Coupling for Your Duty
The performance of a mag drive pump depends heavily on correct coupling and bearing selection. Our specialists can help you:
- confirm suitability for your fluid
- size torque capacity correctly
- select containment shell materials
- ensure temperature and dry-run protection
- optimise for long, reliable service life
Contact AxFlow for expert mag drive pump and magnetic coupling support.
