The Types ZA and ZB tenders were both introduced in 1892 as tenders to the original Cape Government Railways 7th Class Mastodon type locomotive, which was built in two batches. Six engines were built by Dübs and Company in 1892, and 32 by Neilson and Company in 1892 and 1893. Since a Neilson works picture shows one of the Neilson-built batch of locomotives with a three-axle tender, it is likely that the larger-capacity Type ZB three-axle tenders were delivered with the second batch of 32 7th Class locomotives, built by Neilson. The locomotive and tender were designed at the Salt River works in Cape Town in 1892, under the supervision of H.M. Beatty, the CGR Western System's Locomotive Superintendent. The Type ZB entered service as tenders to these locomotives, all of which were initially placed in service on the Midland System of the CGR, but were later distributed between the Midland and Eastern Systems. These engines would be designated Class 7 on the South African Railways in 1912.
Characteristics
The tender had a coal capacity of and a water capacity of, with an average maximum axle load of.
Locomotive
In the SAR years, tenders were numbered for the engines they were delivered with. In most cases, an oval number plate, bearing the engine number and often also the locomotive class or tender type, would be attached to the rear end of the tender. During the classification and renumbering of locomotives onto the SAR roster in 1912, no separate classification and renumbering list was published for tenders, which should have been renumbered according to the locomotive renumbering list. Only Class 7 locomotives were delivered new with Type ZB tenders. The 32 Neilson-built tenders should have been numbered in the SAR number ranges from 954 to 967 and 975 to 977 in respect of the seventeen ex-Midland System engines, and 970 to 974 and 978 to 987 in respect of the fifteen ex-Eastern System engines. Having already been in service for twenty years by then and given the interchangeability of tenders between engines, it is possible, but not confirmed, that tenders were numbered for the engines they were attached to at the time.
Classification letters
Since many tender types are interchangeable between different locomotive classes and types, a tender classification system was adopted by the SAR. The first letter of the tender type indicates the classes of engines to which it could be coupled. The "Z_" tenders could be used with the following locomotive classes:
