You must accept marketing cookies to view this content.

Watch the video at the service provider. (youtube)

Pulleys with an integrated rope clamp are certified to EN 12278 and EN 567 and developed to haul loads and for rescues. Both standards solely require static tests. Despite this, pulleys with an integrated rope clamp, such as the EDELRID SPOC, are increasingly being used for belaying or as a backstop on a fixed point when using a sliding rope. Such uses involve a risk of a fall damaging or, in the worst-case scenario, severing the rope. Whether or not the risk is acceptable depends on the users’ level of risk acceptance and their ability to consistently implement risk-mitigating measures.

If the rope is constantly pulled taut while belaying, the self-locking pulley is essentially subjected to a static load if the climber falls. If, however, the belayer does not consistently pull in the rope or if the climber moves too quickly, slack rope forms in front of the pulley, which is then subjected to a dynamic load in the event of a fall. The same scenario applies in the case of a sliding rope where a self-locking pulley is attached to a fixed point as a backstop. If the second climbs slightly quicker, slack rope forms in front of the pulley, which is subjected to a dynamic load in the event of a fall.

When used as a rope clamp, the relevant legal standard establishes that when subjected to a static load of 4 kN, the self-locking pulley must neither be deformed to an extent that restricts its functionality nor sever the rope. How should the risk of damage to the rope in the event of a fall on the pulley be assessed?

 

What is acceptable?

Self-locking pulleys are developed for static loads. However, dynamic loads that can damage ropes occur during belaying use or when attached to a fixed point as a backstop. As a result, the instructions for use do not allow such usage. Products should always be used in line with the manufacturer’s specifications in the user manual. When assessing the use for belaying or as a backstop on a fixed point, the rope condition that the user is willing to tolerate following a fall is a key consideration. If belaying is regarded as an emergency system intended to prevent a complete fall, a ripped sheath may be tolerable. If falling is part of the sport and the gear is intended for long-term use, sheath damage is no longer acceptable. The following test results should make it easier to assess the different uses.

 

Test method

Two test scenarios were used:

  1. A fall height of 1 m with a variable distance between the rope and the fixed point
    A 100 kg sandbag falls on the SPOC self-locking pulley from a height of 1 m and at an ever greater distance from the fixed point.
  2. Different fall heights with a fall factor of 1
    A 100 kg sandbag falls on a SPOC self-locking pulley that is clipped to a fixed point from different fall heights but with a consistent fall factor of 1.

The condition of the rope following the fall was assessed and the results were categorized based on the following descriptions:

Results

Fig. 1: Variation of the rope length with a fall height of 1 m when using an EN-892-certified CANARY PRO DRY 8.6 mm and a fall mass of 100 kg

Fig. 2: Different fall heights with a fall factor of 1 when using an EN-892-certified CANARY PRO DRY 8.6 mm and a fall mass of 100 kg

 

Slack rope is most precarious if the climber is near the belay station when belaying or if the second climber approaches the fixed point while the rope is sliding. Further away from the belay station, the problem is mitigated by the elongation of the rope.

With an EN-892-certified CANARY PRO DRY 8.6 mm and a fall mass of 100 kg, a fall from a height of 1 m with a rope length of less than 5 m will cause slight sheath damage. From a rope length of less than 3 m, the sheath will be damaged to an extent that the core is visible and from a length of under 2 m, the sheath and the core strands will be severed. The problem is slightly alleviated with a fall mass of 80 kg but not resolved. When assessing the area right by the belay station with a fall factor of 1, the rope can be damaged to an extent where the core is visible even with slack rope lengths of as little as 0.25 m. Core strands can be severed from 0.5 m and the rope can sever completely when 2 m in length, even with an 80 kg fall mass.

 

Discussion

Depending on the rope and the weight of the climber, things get precarious at a distance of about 3 m from the belay station if the rope between the self-locking pulley and the climber is not consistently pulled taut. The factors that influence whether and how a rope in a pulley is damaged include the type and weight of the fall mass, the amount of rope and slack rope, and the rope properties. The results here relate to a 100 kg sandbag. A lighter climber who swings and absorbs energy by tilting will exert less strain on the rope. If a climber falls from an upright position with a tense body, this can exert a similar amount of strain on the rope as the sandbag. How the relation between the rope length and the slack rope length affects the level of strain placed on the rope can be seen in detail in the results. These are based on a CANARY PRO DRY 8.6 mm certified to EN 892. Auxiliary lines with low elongation significantly exacerbate the problem (although these are not actually suitable for such uses anyway).