Introduction
This post will cover the Rope Category Number, it's purpose, and how to determine it's value.
What is the Rope Category Number?
The RCN or Rope Category Number is ISO 4309's attempt to categorise wire rope by the number of load bearing wires in the outer strands. The RCN is used to determine the maximum permissible number of random broken wires during an inspection.
What is the purpose of the Rope Category Number?
The maximum number of broken wires before a rope becomes dangerous is dependent on the construction. As new wire rope constructions reach the market all the time, if the construction was used in ISO 4309 to determine the safe number of broken wires, it would be necessary to publish a new version of the standard several times a year to keep up!
As the safe number of broken wires depends on the number of load-bearing wires, categorising ropes by load-bearing wires is logical, and future-proofs ISO 4309.
How can you determine the value of the Rope Category Number (RCN)?
There are several ways of finding the Rope Category Number.
- Many wire rope suppliers/manufacturers list the RCN in their product specifications.
- Users of Rope IQ can input the construction to determine the RCN automatically. Rope IQ also has a growing database containing ISO 4309 data (including the RCN) for around 18,000 products.
- Using the look-up tables below as detailed in tables 3 and 4 of ISO 4309 - Refer to ISO 4309 to determine how to apply the tables to your mechanism.
Look-up table for determining the RCN of Single-Layer and Parallel-Closed Ropes. (Seale constructions with 19 wires or less e.g. 6x19 Seale are placed 2 rows above where they would normally be placed. Where a wire rope has Filler wires, these are not regarded as load bearing wires)
Look-up table for determining the RCN of Rotation-Resistant Ropes. (Seale constructions with 19 wires or less e.g. 6x19 Seale are placed 2 rows above where they would normally be placed. Where a wire rope has Filler wires, these are not regarded as load bearing wires)
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Conclusion
Thanks for reading our article! We hope you found it useful!
The Rope Category Number is a useful classification for wire rope inspectors and is an essential component of ISO 4309. Without the RCN, determining the maximum number of permissible broken would be an arduous process.
Thanks for reading,
The Rope IQ team.
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