Magnetic Couplings

It transmits torque between two shafts by means of a magnetic field, through a hermetically sealed barrier, with no physical contact. It is common in pumps and mixers where leakage must be prevented and wear eliminated, and in chemical, medical and vacuum applications.

The mechanical solution to sealing

In a conventional pump or mixer the shaft exits by passing through the housing, and at this point there is a gland packing or mechanical seal. This element is the weakest link of the system: it wears, it leaks and it needs periodic maintenance. The magnetic coupling removes this problem — the shaft never passes through the housing.

The magnet assembly on the drive side turns the magnet assembly on the other side of the hermetic barrier between them by means of the magnetic field. The two sides never make physical contact with each other. Because there is no point that can leak, the risk of leakage drops to zero.

A critical additional benefit: overload protection

A little-discussed advantage of the magnetic coupling is that above a certain torque it starts to slip. If the system jams, the connection does not break; the magnets slip past each other and the drive runs free. Behaving like a mechanical fuse, this protects the motor and the shaft.

Where it is used

Chemical transfer pumps, sterile mixers in pharmaceutical and food production, vacuum systems and any line carrying toxic or valuable liquids. What they have in common is that not even a single drop of leakage is acceptable.

When choosing

The decisive parameters are the torque to be transmitted, the operating temperature and the barrier material. The temperature determines the magnet type; at high temperature SmCo is needed. If the barrier is a conductive metal, the eddy currents that form cause an efficiency loss; for this reason a non-conductive material is preferred in most applications.