Pedestal crane safety

Fellow readers with knowledge of pedestal cranes, comments please

Outlined in paragraph 2 is an actual safety incident on a brand new pedestal crane manufactured by a well known European company that occurred in the 90s. I would like to ask fellow readers with knowledge of pedestal cranes to read it and then comment on the questions 1 to 7 below.

An engineer was standing on a wharf in El Ferrol, NW Spain. He was waiting to enter a metal cabin being lowered for subsequent hoisting on to a brand new floating drilling rig. There was a very loud bang. The engineer looked around and realised that the hook block on the whip hoist had detached, hit the metal cabin being lowered on the main hoist, bounced it around and had then ricochetted into a portable diesel generator a few feet away. Ever since the engineer has thought about the sequence of events that caused the hook block to detach and nearly kill him and asked if it could happen again to others or damage facilities. The crane operator had gone against instructions not to operate the whip hoist. The limit switch preventing contact between the hook block and the boom end was under maintenance. The failure to comply with this instruction meant that the hoisting cable snapped, released the block which then hit the wharf via the cabin. Could a hook block detach to-day offshore?
 
1. Are we still entirely dependent on electro-mechanical limit switch devices to limit hook block vertical movement? Are such devices reliable enough for such critical service?
2. How many limit switches should be installed per hoist? One? 100% back-up too?
3. Is it considered the crane owner's and manufacturer's norm for limit switches to be installed on both the main and whip hoists?
4. I believe there is a design of offshore pedestal crane that actually permits a hook block to contact the boom end before hoist cut-out. True or false? Should such a design be considered safe?
5. Is there other and reliable instrumentation in use to control excessive vertical movement of the hook block?
6. Are crane operators permitted to simultaneously operate the main and whip hoists?
7. Do crane inspection and testing procedures include inspection and testing of limit switches and any other similar devices?
 
David Clayton, Caterham, Surrey

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