Abstract: Structural steel profiles such as channels, having a material thickness greater than 2 mm, are roll-formed to a preform profile with corners partial bent, in-line galvanized, and then further roll-formed to final shape. The preform profile has upwardly facing convex surfaces allowing rapid shedding of excess galvanising material. By preforming corners before galvanising, surface elongation in the galvanising layer is minimized and cracking eliminated. This is enhances by constant length bending of corners over preform and final roll-forming operations.

Abstract: A high pressure bag for pre-stressing a support pack in an underground mine has a fluid impervious liner and three tubular envelopes. The liner is located in the first envelope with end portions of the first envelope and edge strips of the liner folded over underneath the first envelope. The first envelope with the liner therein are in the second envelope, with end portions of the second envelope folded over on top of the second envelope. The second envelope is located within the third envelope which has opposed edges stitched closed. The liner has a nozzle which extends through openings in the envelopes.