The HY wagon was introduced in 1948 as a general service wagon identical in design to the _GY_. As such the vehicle was not suitable for the carriage of bulk grain. The wagons of this type were introduced to service as _IY_ / _IO_ wagons. These classifications caused some confusion and the wagon class was changed to HY.
The number group started at 15870, which was a continuation of the _I__ wagon number block; initial wagons being IO.
This group caused problems in traffic as they were mistaken for GY wagons and loaded with bulk grain. To avoid mistaken identity, the _GY_, _GZ_ and _G__ bulk grain wagons were painted with yellow stripes in the corners.
Wagon construction continued through to 1958 with the number block being 15870 - 17030. This number block was converted to bulk traffic GY wagons from 1961, retaining the HY number.
Older _IZ_ type wagons were being rebuilt with these style bodies from 1959. These wagons were recoded to HY from 1961. The rebuilds continued until 1965, the wagons issued as HY. These HY wagons were in the low number group, below the block starting at 15870.
From 1966 to 1968, the railways modified most of this group to GY. The code and number changed, the wagons being renumbered into the GY block 911 - 1160. Other wagons were placed into the _RY_ group.
The HY numbers were:
1, 6 - 12, 14, 16, 21 - 23, 25, 27
28, 30, 32, 33, 37, 39, 41, 42, 44
45, 55 - 58, 60, 65, 66, 68, 74, 77
79 - 81, 83, 88, 93, 94, 104, 105, 107
111, 113, 118, 121, 125, 127, 130, 132, 135
136, 138, 139, 141, 155, 156, 162 - 164, 168
179, 180, 185, 192, 194, 197, 202, 204, 205
210, 213, 216, 228, 231, 240, 251, 252, 254
255, 257, 259, 261, 262, 265, 275, 280, 286
292, 295, 301, 307, 309, 312, 324, 326, 332
333, 337, 340, 341, 343, 355, 358, 367, 368
379, 388, 389, 393, 398, 399, 403, 406, 410
415, 417, 422, 427, 431, 432, 434, 435, 438
442, 445, 447, 450, 453, 467, 470, 474 - 476
480, 481, 490, 493, 495, 498, 499, 505, 516
524, 527, 529 - 532, 538, 544, 547, 548, 562
563, 567, 568, 580, 581, 585, 593, 594, 604
641, 692, 714, 743, 749, 752, 762, 766, 771
775, 778, 779, 783, 788, 790, 793, 799 - 801
804 - 806, 832, 878, 945, 975, 998, 1007, 1027
1033, 1041, 1064, 1113, 1119, 1122, 1126, 1145, 1172
1182, 1193, 1194, 1196, 1219, 1236, 1239, 1242, 1248
1256, 1257, 1262, 1280, 1302, 1306, 1316, 1325, 1349
1365, 1380, 1387, 1421, 1423 - 1425, 1451, 1464, 1481
1505, 1516, 1558, 1564, 1578, 1603, 1630, 1655, 1719
1799, 1806, 1846, 1848, 1849, 1873, 1923, 1936,
15870 - 17030