Length: 30 Min.
Drums, Blocks, Sheaves, and Wire Rope Terminations -
Installation, Usage and Inspection
Cranes and their associated rigging require periodic inspections including pre-use, monthly, quarterly, and annual intervals. These inspections will include the wire rope, drum, blocks, sheaves, rollers and other rigging hardware that may come into contact with the wire rope and subject it to wear.
All of these critical care points must be maintained in top operating condition. This program will provide you with an introduction to the equipment and procedures necessary for the safe reeving, installation and maintenance of cranes and hoists.
Wire Rope Installation
Let’s begin with the installation of wire rope. To avoid introduction of twist into the rope while reeving, remove the rope from the same side of the reel as it will be operated on the drum, top to top or bottom to bottom.
This will avoid a reverse bend in the rope as it is being installed. A reverse bend causes the rope to become “twisty”, difficult to handle and difficult to spool smoothly on the drum. This is especially true for larger diameter wire ropes.
A braking action should be applied to the reel at all times. Use a block or timber against the reel flange in order to get a good smooth wrap on the drum. Spool rope under tension to properly seat the rope on the drum. Particular care shall be taken in spooling the first layer.
Double check to see that the boom, main and auxiliary hoist systems are reeved for the specific crane configurations in use.
When reeving through the sheave system, avoid kinks or looping which could damage the rope.
Do not allow the rope to become slack and loose on the drum. When the boom is at rest with no load on the hook, maintain a slight tension in the boom hoist system.
When hoisting or lowering an empty hook block or overhaul ball, reduce the drum speed if possible, before the brake is applied to prevent loosening of the rope on the drum.
When a rope is found to be loose on the drum, re-spool the rope under tension as soon as practical while performing a visual inspection. At all inspections, other than the Pre-use inspection, re-spool the drum under tension where required and practical.
The hoisting and moving of heavy objects weighing more than the safe working load of the rope being used requires increased pulling force or a change in pulling direction. Blocks are the rigging tools that can make this possible.
There are four basic types of Blocks-
Hook Block Wire Rope Block Block & Tackle Snatch Block
To select a block to fit your requirements consider the following points.
* Are there regulations which could affect your choice of blocks such as federal, state, ANSI, OSHA, API, MMS, ABS or other maritime or insurance requirements?
* What is the weight of the load, including any dynamic loading considerations? You must be aware of these factors to determine the minimum required Working Load Limit value of the block.• How many parts of line are required? This can be determined given the weight of the load to be lifted and the line pull you have available.
* What is the size of line to be used? Multiply the available line pull by the desired safety factor for wire rope to determine the minimum catalog wire rope breaking strength?
* What is the speed of the line? This will help you determine the type of sheave bearings necessary.
* What type of fitting is required for your application? This may be influenced by whether the block will be traveling or fixed. Options include single or multiple hooks with or without throat latches and shackles. Fittings either fixed, swivel, or swivel with lock and the type of bearings needed?
* What type of bearing is needed based on the speed of the line. Slow line speeds, frequent use and significant loads call for bronze bushings with pressure lubrication. Faster line speeds, very frequent use and greater loads require anti-friction bearings.
* How will the block be reeved and does it require a dead end becket?
* If the block is to be a traveling block, what weight is required to overhaul the line?
* What is the fleet angle of the wire rope? Line entrance and exit angles should be no more than 1 ½ to 2 degrees.
* And how will the block be maintained? Do conditions in your application require special maintenance considerations?