A term used to describe the design of a mechanical seal. Unlike the cartridge design, only the static components of the mechanical seal are combined in a single component in a semi-cartridge design. The rotating components are assembled separately. A semi-cartridge design offers cost advantages over the pure cartridge variant. With HYGHSPIN twin-screw pumps, there are also advantages in terms of assembly, which is why only semi-cartridge mechanical seals are used here.