Document 8VKBQvwG49O8nO3YmgEDnbykK

25--Hoisting Apparatus and Conveyors that the rod will pull out of the piston, thus letting the load drop It is recommended that the locknut be secured to the piston rod by a castellated nut and cotter pin When ever an air hoist is overhauled, a check should be made to see that the piston is well secured to the rod If an ordinary hook is used to hang the hoist from its support, the cylinder may come unhooked if the piston rod comes m contact with an obstruction when lowering A clevis or other device should be used to prevent the hook from being detached from the hoist support To prevent the hoist from rising or lowering too rapidly, a choke, such as a washer with the correct opening, can be placed m the air line coupling It is recommended that a rotary air hoist be provided with a closed loadline guide Hand-operated chain hoists Cham hoists may be portable, but should be either permanently hooked onto a monorail trolley, or built into the trolley as an integral part They are suitable for many operations on which a block and tackle, fitted with fiber rope, is used and are stronger, more depend able, and more durable than fiber-rope tackle There are three general types of chain hoists spur-geared, differential, and screwgeared (or worm drive) The spur-geared type is the most efficient as it will pick up a load with the least effort on the part of a man The differential type is the least efficient Screw-geared and differential hoists are self-locking and will automatically hold a load m position Since the spur-geared type is free running, it tends to allow the load to run itself down Therefore, an automatic load brake, similar to that on a crane, is provided to hold the load It is recommended that the use of common gray iron be avoided for mam load bearing parts The use of ductile materials, such as steel, malleable iron, nodular iron, or alumi num alloy, is suggested as they will withstand sudden shock better Chains should be made of the best quality of welded steel with a load safety factor of 5 Chain hoists should be of larger capacity than the regular work requires Supports for the hoists must be strong enough to carry the load imposed on them Chain inspection is described m Chapter 26, "Ropes, Chains, and Shngs " When a man hangs up a chain hoist prior to using it, he must exercise care not to strain or otherwise injure himself Cranes--design and construction OSHA requires that all new overhead and gantry cranes, constructed and installed on or after August 31, 1971, meet the design speci fications of the American National Standard B30 2 0, Safety Code for Overhead and Gantry Cranes Overhead and gantry cranes con structed before August 31, 1971 should be modified to conform to those design specifica tions by February 15, 1972, unless it can be shown that the crane cannot feasibly or eco nomically be altered and that the crane sub stantially complies with OSHA requirements All parts of every crane (Fig 25-3), es pecially those subject to impact, wear, and rough usage, should be of adequate strength for maximum service Journals and shafts should be of sufficient strength and size to bring the bearing pressure within safe limits Open hooks should not be used to support human loads, loads that pass over workmen, or loads where there is danger of relieving the tension on the hook due to the load or hook catching or fouling Outdoor storage bridges should be provided with automatic rail clamps A wind-indicat ing device should be provided which will give a visible or audible alarm to the bridge opera tor at a predetermined wind velocity If the clamps act on the railhead, any beads or weld flash on the railheads should be ground off Structural members of cranes should never be made of cast iron or other frangible metal In the fabrication and assembly of structural work, such as girders, end frames, operators' cages, booms, and brackets, hot-driven nvets or welding should be used instead of bolts Where bolts must be used, they should be of the "through" type, with locknuts or conven tional nuts and lockwashers Each independent hoisting unit of a crane should have brakes complying with the re quirements of American National Standard B30 Series, "Safety Code for Cranes, Der ricks, Hoists, Jacks, and Slings " The rated load of the crane should be plainly marked on each side of the crane If 668