Sealless Technology

If pumps are used to handle dangerous products, it is essential to avoid even the smallest leakages into the environment in order to ensure the protection of both people and the atmosphere. The ideal solution for such a case is pumps with magnet drive. The first of its kind was introduced by Klaus Union in 1955.

Technical Description
The figure shows a cross sectional view of a pump with magnet drive The drive shaft – to transfer the mechanical energy from the drive to the pump hydraulics – is not a single shaft with a mechanical seal, gland packing or mechanical seal on it. Instead, the mechanical energy transferred from the drive to the pump shaft is transferred to an outer ring (outer magnet carrier) fitted with permanent magnets. The impeller of the centrifugal pump is firmly connected via the impeller shaft to an inner ring (inner magnet carrier) also fitted with permanent magnets. Due to the rotation of the outer magnet carrier, the inner magnet carrier is rotated synchronously via magnetic forces; the mechanical drive energy is transmitted via the magnetic field.

A containment shell is installed to separate the pumped fluid from its environment. The impeller shaft is supported by fluid-lubricated slide bearings within the pump’s hydraulic system. There are no dynamic seals between the pumped fluid and the environment from which leaks can escape to the environment. Only two static seals (designed as flat seals or O-rings) are used between pump casing and casing cover and between casing cover and containment shell in the magnetically driven pump. The static seals are maintenance free and therefore the pump is hermetically sealed.

Advantages vs. Mechanically Sealed Pumps

  • Nearly maintenance free
  • Less investment costs and less maintenance costs
  • No instrumentation or special monitoring devices required in standard
  • No utilities required, such as nitrogen or cooling water
  • No leakage to the atmosphere
  • No loss of sealant liquid
  • No wear of the seals at all
  • Low mechanical loads on shaft and bearings
  • High stiffness of the pump shaft

Advantages vs. Canned Motor Pumps

  • Standard IEC and NEMA motors can be used
  • Lower investment and repair costs
  • Separate flushing of journal bearing
  • Higher efficiency
  • Use of non- metallic containment shell possible
  • No heat generation of the rotor by electric losses
  • Higher viscosities possible
  • Higher temperatures without cooling possible
  • No special monitoring devices necessary