High Pressure Multi-Stage Centrifugal Pump is a pump with an axially split casing and a number of impellers carried by a drive shaft has inter-stage bushings and rings for sealing each side of each impeller. Each bushing or ring is conventionally prevented from rotating by a radial pin protruding from the lower half of the casing into an axial slot in the periphery of the bushing or ring. The pin is necessarily small and is liable to shear, difficult to engage in the slot and in cases where the bushing or ring is diametrically split, does not allow rotation of the lower half for its removal without lifting the shaft. To avoid all these disadvantages, without introducing any risk of leakage, a tangential pin is fitted in a blind hole in the casing so that its exposed end is flush with the joint face of the casing and abuts against a shoulder formed by a recess in the periphery of the bushing or ring. This tangential pin can be larger than the known radial pin and is subjected to compression, not shear. These pumps are applied in water supply system, fire-extinguishing systems and for pressure-boosting systems.