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PART 18  IVATT BOILER CLASSIFICATIONS
Boiler Types were introduced around 1900. The columns below show two early Ivatt types, later Gresley GNR Diagram number (where known), LNER Diagram number (where appropriate). This list is sorted in order of Column 2. The information in the first two columns is based on notes made by Roy Burton, senior draughtsman in Doncaster Locomotive Drawing Office until 1959.
Early Ivatt type 
Later Ivatt type 
Gresley Dgm. 
LNER Dgm. 
Ivatt Engine Classes 
A3 
A1 


A1 
A1 
A2 


A2 
A2 
A3 


A3 
B1 
B1 


B1 
B2 
B2 


B2 
B3 
B3 


B3, B4 
B4 
B4 


A4, A5 
C5 
C5 


B6 
D1 
D1 
4 
11 
B7, C2, D2, E1, E4, F3, G4, J5, J8, J16 
C6 
D3 


B5, E2, E3 
D3 
D4 


F2 
D4 
D6 


J6 
D5 
D7 


J7 
D6 
D8 
4a 

G3 
D8 
D9 
4a 

J17 
D9 
D10 


J9 
D10 
D11 


J10 
E1 
E1 
6 
7 
D1 
F1 
F1 
2 
4 
C1, K1 
F2 
F2 
2 
4 
C1 No. 271 
J1 
H1 


F1 
L1 
J1 


F6 
K1 
J2 


F4 
O1 
J3 


G2 
M1 
K1 


F5 
P1 
K2 


J1, J2, J3 
N1 
L1 


F7,G5 
Q1 
M1 


J4 
R1 
N1 


J11, J12 * 
S1 
O1 
10 
9 
J13 
T1 
P1 


J14 
U1 
Q1 


J15 
V1 
Q2 


J18 
W1 
R1 


J19, J20 
X1 
S1 


H1 
* "GREAT NORTHERN LOCOMOTIVE HISTORY" (Norman Groves) notes that in the January 1902 Boiler Classifications, Classes J11 and J12 were in Boiler S1. There were thus more changes in the classification than suggested in the table above.
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