Anchorage Systems guidelines specify a two rope system consisting of a main and backup rope should have an MBS of what, or two times the maximum arrest force of the backup system, whichever is greater?

Anchorage Systems guidelines specify a two rope system consisting of a main and backup rope should have an MBS of what, or two times the maximum arrest force of the backup system, whichever is greater?

• A. Two rope system consisting of a main and backup, should have a MBS of 12kN or 2700lbf or two times the maximum arrest force of the backup system, whichever is greater
• B. A single rope with MBS of 6kN
• C. Three rope system with MBS of 8kN
• D. A chain anchor with MBS of 12kN

Answer: (A)

When selecting an anchor system for a two-rope setup (main and backup), the strength rating must cover the actual forces you could see during arrest, plus provide redundancy. The guideline says the system’s minimum breaking strength should be at least either 12 kN (about 2700 lbf) or two times the maximum arrest force of the backup system, whichever is greater. This ensures the rope pair can handle a standard rating, while also scaling to the real loads that could occur in a fall. If the maximum arrest force of the backup is higher than 12 kN, you use twice that arrest force to determine the required MBS; this keeps the system strong enough even in harsher-than-average falls and preserves the backup’s ability to arrest. The two-rope arrangement isn’t about a single rope or a three-rope configuration, and a chain anchor isn’t the scenario described here—the emphasis is on ensuring the two-rope system has an MBS sufficient for both the standard rating and the actual arrest loads.

When selecting an anchor system for a two-rope setup (main and backup), the strength rating must cover the actual forces you could see during arrest, plus provide redundancy. The guideline says the system’s minimum breaking strength should be at least either 12 kN (about 2700 lbf) or two times the maximum arrest force of the backup system, whichever is greater. This ensures the rope pair can handle a standard rating, while also scaling to the real loads that could occur in a fall. If the maximum arrest force of the backup is higher than 12 kN, you use twice that arrest force to determine the required MBS; this keeps the system strong enough even in harsher-than-average falls and preserves the backup’s ability to arrest. The two-rope arrangement isn’t about a single rope or a three-rope configuration, and a chain anchor isn’t the scenario described here—the emphasis is on ensuring the two-rope system has an MBS sufficient for both the standard rating and the actual arrest loads.