Monday, July 23, 2012

Blocks (Campbell USA)

Block systems must be properly designed, used and maintained. A continual inspection program should be undertaken to discover gouges, distortion, cracks, elongation (or stretching), spread in the throat openings of hooks, severe wear or other damage. Any abuse, misuse or alteration may lessen the load a block system will sustain. Some examples of changes are as follows:
• Twisting or side loading
• Disfigurement
• Corrosion
• Shock loading
• Use for a purpose other than that for which a particular block was intended
•Use to carry a load in excess of the Working Load Limit

Blocks consist of one or more sheaves fitted in a wood or metal shell. Blocks are supported by a fitting attached to the strap of the block. These blocks are intended to be used in conjunction with other components in a load-sustaining system to gain mechanical advantage. Care should be taken to select components of compatible type, size and Working Load Limit. Work Load Limits shown in Apex Tool Group literature are applicable to new blocks, or blocks in “as new” condition.

Selection of Blocks

To select a block to fit your requirements, the following must be considered:
1. Are there regulations that could affect the choice of blocks, such as federal, OSHA, state, maritime, etc.
2. What loads (weight) will be lifted? This must be known to select a block with an appropriate work load limit.
3. How many parts of line are required?
4. What is the size, type and working load limit of rope to be used? Consult a rope catalog to determine working load, rope strength and fatigue factors.
5. What is the speed of the line? This will help determine what type of bearing should be used.
6. Insure that the proper type of fitting is utilized. A block used above or aloft should be attached with shackles.
7. How will the block be reeved, and does it require a dead end becket?
8. What is the fleet angle of the wire line? Line entrance and exit angles should be no more than 90°. Use the bight angle factor to determine resultant load to properly determine Working Load Limit of your block.

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