Housing compression-proof for PN 2,5/PN 6. Cylinder with noise reducing chamber on the discharge side, housing with connections for injection- and water flushing, as well as for lubrication - and purge oil supply systems. Conveying chamber by single-acting oil-purged mechanical seals in combination with labyrinth seals sealed on the shaft. Direction of flow horizontal/vertical (depending on size). Drive directly via coupling or flexible spur gear (depending on size).