to a Class 19D locomotive. The locomotive selected for the experiment was Krupp-built no. 2644, a particularly poor-steaming member of the Class at the time. A gas producer combustion system (GPCS) and dual Lempor exhaust were installed, along with some other small improvements. The Lempor had a four-jet blastpipe with extended petticoats to provide truer ejector proportions. To accommodate the arrangement, the smokebox was extended by . Steam flow in the cylinders was improved by streamlining the edges of the piston valves which were each equipped with an additional valve ring to reduce leakage. The firebox was modified to the GPCS system wherein principal combustion is effected using secondary air introduced above the firebed through ducts in the firebox sides, while primary air was restricted through dampers and a redesigned grate. Firebox turbulence was created by steam jets and clinkering was inhibited by introducing exhaust steam under the grate. Sanding was improved and de-sanding jets were installed to clean the rails after the locomotive had passed. The modifications improved the locomotive's steaming rate and enabled it to achieve significantly higher power and significantly lower fuel consumption than other unmodified Class 19D locomotives, the coal savings and increased output being in the order of 20% to 25%. The success of this experiment convinced the SAR management at the time of the viability of the project which culminated in the Class 26 Red Devil. Preservation Of the Class 19D, several survived into preservation. By 2018 Works numbers and renumbering The table shows the Class 19D builders, works numbers, years built and engine numbers. Batch code symbols for the weight specifications as defined in the infobox are included in the "Notes" column. References External links Borsig locomotives Cape gauge railway locomotives Henschel locomotives Krupp locomotives NBL locomotives Railway locomotives introduced in 1937 Robert Stephenson and Hawthorns locomotives Škoda locomotives Steam locomotives of South Africa Steam locomotives of Zimbabwe 2020 2020 2D1 locomotives 4-8-2 locomotives