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Caterpillar
Inc., Lafayette, IN, manufactures large diesel engines in sizes from 800 to 6000 hp for
marine, locomotive and power generation / cogeneration applications. Caterpillar also
makes engines driven by LP, natural gas and special fuels, such as methane, on request.
The engine blocks can be up to 12' 7" long and weigh several thousand pounds.
Handling these large blocks safely and efficiently during machining operations is very
important to management. Also, production needed rotating capability to reposition the
blocks between operations. |
Solution
Engineering checked the criteria for the operations and decided to try a powered sling
material handling system. It consists of a pair of knurled rotator drums driven by
electric gear motors for independent action. The knurled surface of the rotator drum
provides traction for the continuous sling - one sling is used on each drum.
The two continuous slings are passed over the rotating drums and around the object to be
handled, producing contact on at least three sides of the object. After it is lifted by
the two continuous slings, electric motors with chain and sprocket reduction rotate the
object. Rotation can be stopped at any point in the cycle.
The powered sling material handling device can be hung from a bridge crane or trolley
hoist. It can also be lifted by a forklift truck or incorporated into a gantry crane. The
device is custom designed in sizes ranging from compact and lightweight units with a
1500-lb capacity to systems capable of turning 30-ton railroad can.
Web slings are available in both polyester and nylon with metal disconnect links or
endless configuration. Both types are strong, lightweight and flexible.
Metal mesh slings are used in metalworking operations where loads are hot and/or abrasive.
Stainless steel slings are also available for corrosive environments. Disconnect pins are
used with metal mesh slings.
All gear motors are equipped with static torque brakes as a standard feature for stopping
and holding in any position. Air motors are available as an alternative to expensive
explosion proof electric motors.
Caterpillar is using three 30,000-lb web-sling material handling devices permanently
attached and electrically connected to underhung cranes. They are used to transport,
rotate and reposition blocks between machining operations. Two have pendant controls (a
single unit controls both the crane and rotator) and one is radio-operated.
Caterpillar purchased the first two powered sling material handlers in 1984 and the third
was purchased a short time later.
Results
One operator can now safely and efficiently transport the heavy, bulky engine blocks to
and between machining operations and simultaneously rotate the blocks enroute.
The turning operation is performed quickly; actual elapsed time for one complete
revolution of an object is about 60 seconds. |
