While transferring a load from ship to pier side, the hand chain on a chainfall dragged across a compressed gas cylinder bottle rack and caught a regulator valve on a bottle. When the chain released from the valve the bottle fell back to the rack. The hand chain had been left hanging and was not properly secured.
• A 1,000 lb (900 kg) chain hoist was being used to lower a part into a tank when the load and chain fell into the tank. The load chain was not being properly lubricated and rags were being used inside the chain container to prevent contaminants on the chain from entering the dip tank. This led to improper piling of the load chain in the chain container resulting in a cross-linked load chain jamming into the hoist housing, ultimately breaking the load chain.
• A seal housing was dropped when a 3 US ton (2.7t) chain hoist failed. The load chain had become twisted as a result of the lower load hook block flipping through the two-part chain fall loop while not in use. The twisted chain did not engage properly with the load sprocket, allowing the load chain to slip over the sprocket.
• While positioning a load, the chain on a one-ton lever hoist continued to pay out after the rigger stopped pulling the lever. The load chain had become twisted and cross-linked when entering the load sprocket causing the chain to jam into and ultimately break the hoist frame.
• When a 3 US ton chain hoist hook was raised to its upper limit for storage, its chain fell out of the chain container and hit the ground. The chain did not pile correctly due its size and stiffness.
• While attempting to lift a load with a chain block, the hand chain on the chain fall snagged on an obstruction and broke. The hand chain had been left hanging loose and was not properly secured.
• The hook on a 3 US ton chain hoist would not lower. When a mechanic investigated, he noticed that the load chain was jammed between the load sprocket and hoist housing. It was determined that the most probable cause of the chain jamming was from a twisted load chain.
Operators, riggers, and maintenance personnel need to pay particularly close attention to the condition of chain hoists at pre-use inspections, during use, and at maintenance inspections, the US Navy says. Slack load chain that is not freely suspended from the hoist, such as during transport or inside chain containers, is more susceptible to twisting and cross-linking. After transporting chain hoists, load chain should be freely suspended and carefully checked to ensure that the load block has not flipped through the chain falls and twisted the chain. During use, special precautions are required to ensure that slack load chain does not become twisted or cross-linked. Make sure the load chain is not twisted as it travels into the hoist.
Hand chains and empty hooks should be properly secured, stowed, and monitored to ensure that they do not become fouled on other components, the Navy says. During maintenance inspections, load chain should be lubricated as recommended by the original equipment manufacturer and chain containers should be sized and installed as directed by the OEM. Chain containers should be periodically checked for presence of foreign material and proper piling of the load chain. The load chain needs to be carefully inspected and load chain stretch and wear measurements taken to ensure the chain is within acceptable limits. This ensures proper operation over load sprockets and chain sheaves.
