Visual inspections of wire ropes on hoist cranes can be a timely and inexact process. The human eye can only catch the external defects that appear on the wire rope, but internal defects like corrosion and wire fatigue can go unnoticed until the wire snaps. The snapping of the wire rope on a crane can lead to catastrophic consequences for the machinery, surrounding area, and workers. Performing an electromagnetic inspection allows you to see inside the rope to more accurately determine when the rope has to be replaced. Here is how the electromagnetic process works and how you can replace the rope.
The Electromagnetic Inspection System
An electromagnetic inspection system sends electronic signals through the strand of wires making up the rope to measure any magnetic changes. As a metal rope deteriorates, the magnetic charge it gives off changes. This allows you to deduce when it's time to discard the rope for safety reasons. The process is particularly effective at identifying the loss of the metallic area below the surface of large diameter hoist ropes - which was traditionally done by estimating when the wire rope should be replaced.
Performing the Inspection
You will place a Loss of Metallic Area Sensor onto the rope. The sensor has primary and secondary coils placed on opposite sides of the rope. A low frequency AC current is sent from the primary coil through the wire rope that magnetizes the rope. The secondary coil measures any changes in the magnetic field as the rope passes through the sensor. As the rope goes through the sensor, your personal computer will monitor any changes in the magnetic field. You will run the entire rope though the sensor to make sure there aren't any weak spots.
Changing the Hoist Rope
You want to make sure that the replacement wire rope meets the manufacturer's specification for the crane you are using. You can replace the wire rope by following these directions.
- Lower the hoist block so you can easily work on it
- Disconnect one end of the wire rope from the cable drum
- Detach the fixed-end of the wire rope from the crane
- Remove the wire rope by separating the two sides of the hoist block
- Make sure the new wire rope doesn't have any twists in it
- Place the new rope in the hoist block and reattach sides
- Reconnect the fixed-end to the crane
- Reconnect to the cable drum
Deteriorating wire ropes can pose a danger to everyone. You should inspect the wire rope to detect any defects and replace the rope immediately if any problems are found. If you need more information about replacing the wire ropes, contact a company like American Equipment Inc.