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Plate Clamp Inspection and Use
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What should you inspect the body of a clamp? - Follow the clamp manufacturers' maintenance recommendations.
- Inspect internal and external surfaces for forging or weld fractures, wear and distortion.
- Check all pin holes for wear.
- Inspect the throat (clamp opening) width. At zero grip, the cam should be in full contact with the pad.
- Measure the width of the throat. If the measurement at the base, where the pad is located is greater than at the top, the body has been overloaded. Replace the clamp; tag the defective clamp and remove it from service.
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| How should you inspect the internal parts of the clamp? - Soak overnight in a degreasing solvent to remove all dirt and grease that prevent proper inspection of components. Degreasing solvents should be used in appropriately well ventilated areas. Handle the wet clamp parts while wearing gloves made of material that is chemically resistant to the solvent.
- Remove the body pins or bolts and slide out the complete internal mechanism.
- Check each body pin or bolt for wear or bending due to overloading.
- Check each spacer, rivet, bolt or internal part for play or wear.
What should you know about the spring, cam, lock and pads? - The cam spring should be strong enough to hold the cam against the pad.
- The locking spring should give initial pressure at near zero grip without material in the clamp.
- There should be "definite tension" in the locked position.
- The spring should not be bent or distorted.
- The lock assembly should rotate freely without binding and must rest fully on the stop pin.
- Cams and pads are vital parts of a clamp and are exposed to wear. Use on one size plate thickness will cause wear only in one area of the cam working surface. Replacement is required sooner than when a cam is used to handle different plate thicknesses.
- Examine the cam surface. If the teeth are flattened by 50% or more, replace the cam and pad.
- Teeth must be sharp and free of foreign material.
How should you use plate clamps safely? - Refer to the manufacturers' operating instructions.
- Inspect clamps visually before each lift.
- Use the correct clamp for a job.
- Use two or more clamps to balance a long or flexible load.
- When using a vertical type of plate clamp, use a locking device to prevent accidental loosening.
- Use horizontal types of plate clamps in pairs.
- Use clamps within their rated capacity and flange width.
- Lock a clamp closed before lifting a load.
- Use a sling between the clamp and the crane or hoist hook.
What should you avoid when using plate clamps? - Do not lift over workers.
- Do not stand near a load. Position yourself away from and fully clear of the load.
- Do not lift from the side with a vertical clamp.
- Do not lift more than one plate at a time with a vertical clamp.
- Do not lift plate from the bottom of a plate stack.
- Do not grind, weld or modify a clamp.
- Do not use a clamp having a minimum jaw opening larger than the thickness of the load.
- Do not leave suspended loads unattended.
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Document last updated on March 13, 2003
Copyright ©1997-2008 Canadian Centre for Occupational Health & Safety
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