Swivel carabiner vs pulley system differences

While swivel carabiners and pulley systems may appear similar at a glance, they serve fundamentally different purposes in vertical disciplines. Misunderstanding these differences can lead to inefficient systems or catastrophic failures. Here’s how to distinguish them and apply each correctly.

Core Functions: Rotation vs. Mechanical Advantage

Technical Breakdown

1. Design & Physics:

• Swivel Carabiner:Contains bearings/bushings allowing the inner sleeve to spin freely.No moving parts cross-loaded by rope force – rotation is passive.Max load = Carabiner strength (≥23 kN).
• Pulley:Features a sheave (wheel) reducing rope friction via rolling motion.Force multiplication calculated by: Output = Input × Number of Strands.Efficiency loss: 10–20% due to axle friction (e.g., 90% efficiency = 10% force loss).

2. Weight & Portability:

• Swivels: 50–90g (e.g., Petzl Am’D: 62g)
• Pulleys: 150–300g+ (e.g., Petzl Pro Traxion: 225g)

3. Cost Comparison:

• Swivels: $20–$35
• Pulleys: $60–$150+

When to Use Each Tool

Critical Safety Distinctions

1. Certification Matters:Swivels require UIAA 121 (strength under static load).Pulleys require UIAA 155 (efficiency + strength under dynamic loads).
2. Failure Risks:Swivel in Pulley Role:Seized rotation under load → friction spikes by 300%+.No mechanical advantage → hauling becomes dangerously inefficient.Pulley as Swivel:Sheaves don’t rotate freely sideways → increases rope twist.Weight penalty (e.g., 250g vs. 60g on a quickdraw).

Real-World Applications

Case 1: Big Wall Hauling

• Wrong: Swivel carabiner for hauling → 0% mechanical gain; 100% effort for 100% output.
• Right: Pulley system (e.g., Petzl Pro Traxion) → 3:1 advantage; 33% effort for 100% output.

Case 2: Traversing Sport Climb

• Wrong: Pulley on quickdraw → heavy, snags rock, worsens rope drag.
• Right: Swivel carabiner (e.g., DMM Shadow) → reduces rope twist by 70%+.

Pro Tips for Selection

1. Ask: "Do I need to move weight or manage twist?"Force multiplication = Pulley (rescue/hauling).Rope rotation = Swivel (lead climbing/rappelling).
2. Hybrid Solutions:Some pulleys integrate swivels (e.g., SMC PMP Swivel Pulley) for twist reduction in haul systems.
3. Inspection Focus:Swivels: Check for grit in bearings and smooth rotation.Pulleys: Test sheave spin and axle wear.

The Verdict

Swivel carabiners specialize in managing rotational forces to prevent rope drag and tangles. Pulleys excel at redirecting force with minimal loss for mechanical advantage. Confusing them risks system failure:

• ✅ Use swivels for: Quickdraws on wandering routes, rappel anchors, lowering systems.
• ✅ Use pulleys for: Hauling bags, rescue lifts, Tyrolean traverses.

Never compromise on certification (UIAA 121 for swivels, UIAA 155 for pulleys), and remember: swivels don’t reduce effort, and pulleys don’t reduce twist. Choose wisely—your safety depends on using the right tool for the physics at play.