Sealless pumps belong to a special class of pumps that do not require a sealing element (mechanical seal) to prevent the pumped liquid from leaking into the atmosphere because its internal rotor, assembled with the impeller, do not extend outside of the pressure containment casing. The casing-shaft joint, which can be a potential source of leakage, is effectively eliminated.
Sealless pumps can be grouped into two types:
magnetic pumps - the internal rotor contains a permanent magnet assembly
Canned motor pumps - the internal rotor contains a laminated iron induction motor core
Sealless pumps, in spite of their special feature of being leak-proof, have certain design constraints that severely limit their application, among which are:
the material selection, and material thickness, of the pressure containment casing is limited making them unsuitable for high pressure application.
the methods of hydraulically balancing the pump is limited, making them unsuitable for high thrust load service.
Sealless pumps are generally more expensive than comparative ANSI or ISO pumps.