Tackle Block Warning, Use & Maintenance Information.
Use & Maintenance Information continued
Fittings, including hooks, shackles, links,
etc., may become worn and disfigured with use, resulting in
nicks, gouges and sharp corners which produce additional stress
conditions. Regular inspection is recommended to monitor product
condition.
Grinding is the recommended procedure to restore smooth surfaces.
A reduction of the products original dimension of 10 percent from
wear and repair is allowable in the load bearing areas. Any
greater reduction may necessitate a reduced Working Load Limit.
Any crack or deformation in a fitting is sufficient cause to
withdraw the product from service.
Some of the blocks shown in Crosby Group
literature are named for their intended use and selection is
routine. A few examples include the "Double Rig Trawl
Block" used in the fishing industry, the "Well Loggers
Block" used in the oil drilling industry, and the
"Cargo Hoisting Block" used in the freighter boat
industry. Others are more generally classified and have a variety
of uses. They include snatch blocks, regular wood blocks,
standard steel blocks, etc. For example, snatch blocks allow the
line to be attached by opening up the block instead of threading
the line through the block. This feature eliminates the use of
rope guards and allows various line entrance and exit angles to
change direction of the load. These angles determine the load on
the block and/or the block fitting. (See "Loads on Blocks.") Snatch blocks are intended for infrequent and
intermittent use with low line speeds.
A tackle block is one element of a system used to lift or drag a
load. There are other elements in the system including the prime
mover (hoist, winch, hand), supporting structure, power
available, etc. All of these elements can influence the type of
tackle block required. When selecting a block for the system in
your specific application, you should consider the other elements
as well as the features of the blocks shown in Crosby Group
literature.
To select a tackle block to fit your requirements, consider the
following points:
Common (Plain) Bore for very low line speeds and very infrequent use (high bearing friction).
Self Lubricating Bronze Bushings for slow line speeds and infrequent use (moderate bearing friction).
Bronze Bushing with pressure lubrication for slow line speeds and more frequent use at greater loads (moderate bearing friction).
Anti-friction Bearings for faster line speeds and more frequent use at greater loads (minimum bearing friction).