A “Slack Anchor System” with Independent Primary, Independent Secondary (often abbreviated as “Independent P, Independent S”) refers to a rope rescue anchor setup designed for maximum redundancy and safety. In this system:
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Primary Anchor(s): The main anchor(s) bear the load of the rescue system.
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Secondary Anchor(s): A completely separate, independent anchor system is set up as a backup, but it remains unloaded (slack) unless the primary system fails.
This approach is widely used in technical rope rescue and rope access scenarios where full redundancy is required, but you do not want both anchor systems to be under tension at the same time.
Key Features
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Full Redundancy: Both the primary and secondary anchors are independent, meaning they do not share any components or anchor points. This ensures that if one system fails (due to anchor failure or rope damage), the other can take over without compromise.
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Slack Secondary: The secondary (backup) anchor is left slack—unloaded—so it does not share the load with the primary. It only becomes active if the primary system fails.
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Simplified Rigging: By keeping the systems independent, rigging is often simpler and inspection is more straightforward, as each system can be checked separately for integrity.
Comparison to Other Anchor Systems
| System Type | Load Sharing | Redundancy | Typical Use Case |
|---|---|---|---|
| Shared Anchor (e.g., self-equalizing) | Yes | Partial | When anchor points are marginal |
| Independent Primary, Independent Secondary | No | Full | High-risk, critical operations |
| Independent Primary, Shared Secondary | Partial | Full | Balance between simplicity and redundancy1 |
Practical Application
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Setup: Two separate anchor systems are built, often using different anchor points and hardware. The primary anchor is tensioned and bears the load; the secondary is rigged but left with slack in the system3.
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Inspection: Both systems should be independently strong enough to hold the anticipated load.
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Activation: If the primary anchor fails, the load transfers to the secondary anchor, preventing catastrophic failure.
Advantages
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Maximum Safety: Full redundancy protects against anchor or system failure.
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Clear Load Paths: Only one system is loaded at a time, reducing complexity in load calculations and inspections.
When to Use
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In environments where anchor failure would have severe consequences (e.g., rope rescue over edges, high-angle rescue, or when anchor reliability is uncertain).
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When regulations or best practices demand independent backup systems.
Summary
A Slack Anchor System with Independent Primary and Independent Secondary is a best-practice anchor configuration in rescue and rope access, prioritizing redundancy and safety by ensuring that a completely independent, slack backup system is in place to take over if the primary anchor fails
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