12.2 Horizontal split-casing pumps
Horizontal split-casing pumps Double-entry horizontal split-casing type pumps (Fig 4.47) have been installed on CEGB stations to cover a wide range of duties up to 18 mVs and 24 m generated head. This design of pump has the major advantage that the top section of casing and the rotating element can be removed without breaking either the pipe joints or disturbing the alignment.
While this feature gives good accessibility for both overhaul and maintenance work, the horizontal design has a number of disadvantages apart from the large floor area required. In particular, the preference for installing the unit with the impeller eye below minimum water level, to eliminate the need for complicated priming equipment, results in expensive civil excavations. The physical size of the large metal casings has also brought about both manufacturing difficulties and flexing problems with the complicated assembly.