Based on the most common gasket-including constructions, 7 standardised variations ensure that the shaft is completely watertight. The use of one or another version depends on the characteristics of the fluid to be pumped.

The seven standardised versions are:

1 - Gasket with casing and an orifice for external fluid. When the pump is operating in suction mode, the external fluid must be grease or another similar liquid compatible with that being pumped. For clean water, the connection can be made from the impeller. Loaded waters require the external injection of clean water.

2 - Gasket with casing, a base ring and an orifice for external fluid. For abrasive or highly loaded water, replace the first gasket ring with a base ring. The exterior clean liquid prevents the pumping from affecting the gasket.

3 - Gasket with casing and two orifices for exterior circulation. This device is used when the sealed fluid has not to come into contact with that being pumped. It has an inlet and an outlet to facilitate the circulation of the exterior liquid.

4 - Simple mechanical lock in keeping with DIN 24960 without external liquid, with subsequent washing. Plan API-11. It makes no difference whether the operation is functioning in suction or in load mode. This system is used for relatively clean liquids. Subsequent washing (quenching), if required, is available as an option with the corresponding connection on the locking cap.

5 - Simple mechanical lock in keeping with DIN 24960, with external liquid and subsequent washing. Plan API-32. This system avails of continuous circulation with clean external liquid. It is used for dirty liquids. Subsequent washing (quenching), if required, is available as an option with the corresponding connection on the locking cap.

6 - Double mechanical "back-to-back" lock. Plan API-54. A lock for abrasive, dangerous liquids etc. It is the external liquid that creates a barrier. It must be injected at a pressure higher than that existing behind the impeller and must be compatible with the liquid being pumped.

7 - Double mechanical "tandem" lock. Plan API-1 with posterior barrier fluid. A lock for abrasive, dangerous and especially toxic liquids. It is the external liquid that creates a barrier. This liquid has to be injected at low pressure, but does not have to be compatible with the liquid being pumped. An alarm system can be fitted to the barrier circuit so that, should the first lock leak, causing a rise in pressure within the circuit, the alarm would go off and in turn  the pump will stop.