2. Pump classification

The general principle of a positive-displacement pump is based on a hermetically sealed volume (the pump body) inside which moves a tightly-fitted moving part, whose movement generates either the vacuum required for suction (suction-powered pump), or the impulse required for discharge, or both, enabling the transfer from suction to discharge of a given volume of homogeneous liquid, or of a more or less pasty consistency, of a more or less abrasive nature, or of a gas. For the same type of pump, the various models differ from one manufacturer to another through an appropriate choice of materials, particularly with regard to contact between fixed and moving parts (in rotation or translation), the forces involved and the fluid conveyed. Paradoxically, the majority of positive-displacement pumps cannot operate with water, due to the fluid's low viscosity or poor lubricity. The adaptation of...