Nord 2.451 to 2.631 were 0-4-2 locomotives for mixed traffic of the Chemins de Fer du Nord.
The machines were retired from service from 1909 to 1923.[1]
The main difference to these older types was the arrangement of the rear axle, which was supported from the outside in order to leave as much space as possible for the firebox between the wheels.[2]
The rest of the frame remained inside the driving wheels.
The Stephenson valve gear and the cylinders were on the inside of the locomotive frame.
The firebox was of the Crampton type, the boiler barrel consisted of three shells, with the middle one carrying the dome.[2]
A Crampton regulator sat behind the chimney, with the steam pipes running down on the outside to the steam chest.
The boiler pressure was 8.5 kg/cm2 (0.834 MPa; 121 psi) on the first and 10 and 11 kg/cm2 (0.981 and 1.08 MPa; 142 and 156 psi) on the later machines, with the earlier series later also receiving boilers for 10 kg/cm2 (0.981 MPa; 142 psi).[1]
The locomotives were coupled with 2 axle tenders, holding 7–8 m3 (247–283 cu ft) of water and 3 t (6,610 lb) of coal, and weighing 20–22 t (44,100–48,500 lb).[1]