How Shock Absorbers Work on Fall Protection Lanyards

When working at height, one of the most important pieces of personal protective equipment (PPE) is a fall arrest system. A critical component of this system is the shock absorber, also known as an energy absorber. Its role is simple yet vital: to reduce the force exerted on a worker’s body during a fall. Without this component, even a properly anchored lanyard could result in severe injury or death due to the extreme forces generated in a sudden stop.

This article explores how shock absorbers work, their construction, deployment mechanism, and why regular inspection is essential for safety.

What Happens in a Fall?

To understand the importance of a shock absorber, you first need to understand what happens during a fall.

When a person falls from height, gravity causes rapid acceleration. If the fall is arrested suddenly (for example, by a static lanyard attached to an anchor), the body experiences a rapid deceleration. This results in a high arresting force on the worker’s body, which can be equivalent to several thousand newtons (or hundreds of kilograms of force).

Even though the fall is stopped, this sudden jolt can cause:

• Internal injuries

• Broken bones

• Damage to the spine or organs

• Harness-related trauma (especially around the legs and chest)

That’s where the shock absorber comes in—to slow the deceleration and reduce the force to survivable levels.

Purpose of a Shock Absorber

A shock absorber’s job is to limit the fall arrest force to a level that the human body can safely withstand. The standard maximum allowable arrest force, according to many safety standards (e.g., ANSI Z359.13 and AS/NZS 1891), is 6 kilonewtons (kN) or about 1,350 pounds-force.

Shock absorbers reduce the force by increasing the stopping distance—a fundamental principle of physics. The longer the time or distance over which the fall is stopped, the lower the force experienced by the body.

Construction of a Shock Absorber

There are different types of shock absorbers, but the most common in fall arrest lanyards is the tear-away webbing type.

Key Components:

• Outer Cover or Pouch: Usually made of durable fabric to protect the internal components from dirt, UV light, and damage.

• Tear-Away Webbing: Inside the pouch is a folded or stitched piece of webbing. This webbing is sewn together with special stitching designed to tear at a specific force.

• Attachment Ends: One end connects to the full body harness, and the other to the anchorage or lanyard.

How It Works: Step-by-Step

1. Normal Use: Under normal conditions, the shock absorber is compact and unused. The webbing remains folded and the stitching intact.

2. Fall Initiation: When a fall occurs and the lanyard becomes taut, the load on the system increases rapidly.

3. Activation: Once the load exceeds a threshold (Typically around 1.8 to 2.7 kilonewtons (kN) of force), the special stitching on the webbing begins to rip open in a controlled manner.

4. Energy Dissipation: As the webbing tears, it absorbs the kinetic energy of the fall. This increases the distance over which the fall is stopped and significantly reduces the arresting force.

5. Full Deployment: Depending on the model, a deployed shock absorber may extend by up to 1.2 to 1.75 meters. The force is reduced to below 6 kN, preventing the full brunt of the fall from impacting the user’s body.

6. Post-Fall Condition: Once deployed, the shock absorber cannot be reused. It remains extended with torn webbing visible, and must be removed from service.

Fall Clearance Considerations

One consequence of using a shock absorber is the added fall clearance distance required. Employers and workers must account for:

• Length of the lanyard

• Maximum extension of the deployed shock absorber

• Height of the worker

• Safety margin (often around 1 meter)

For example, if using a 2-meter lanyard and a shock absorber that extends 1.75 meters, the total fall clearance could easily exceed 6 meters. Failure to account for this can result in a worker striking the ground or a lower level even if the system functions correctly.

Inspection and Maintenance

Shock absorbers are life-critical devices and must be inspected regularly to ensure they are fit for use.

Pre-Use Inspection Checklist:

• Labels and Serial Numbers: Check that they are present and legible.

• Stitching: Look for loose, frayed, or broken stitches on the webbing or pouch.

• Outer Pouch: Check for tears, cuts, burns, chemical damage, or contamination.

• Deployment Indicators: Many models show a red label or exposed webbing if deployed.

• Hardware: Inspect any snap hooks or connectors for rust, cracks, or deformation.

Periodic Inspection:

• A competent person should perform a formal inspection at intervals specified by the manufacturer (commonly every 6–12 months).

If any defects are found or if there is any doubt, the shock absorber should be removed from service immediately.

Storage and Environmental Factors

Shock absorbers must be stored in dry, clean environments. Exposure to:

• Sunlight (UV radiation)

• Moisture

• Extreme heat or cold

• Chemicals or oils

can degrade the webbing and stitching, potentially compromising performance in a fall.

Common Myths and Mistakes

1. “It’s never been used, so it’s fine.” Even unused gear can degrade with time, heat, UV, or poor storage. Always inspect before use.

2. “I can use it again after a fall if it looks okay.” No. Shock absorbers are single-use only. Once deployed, they must be replaced.

3. “All lanyards come with shock absorbers.” Not always. Some restraint or positioning lanyards are not rated for fall arrest and lack shock absorbers entirely.

4. “Visual inspection is enough.” While pre-use visual checks are critical, periodic formal inspections by a trained person are also required.

Conclusion

A shock absorber on a fall protection lanyard is a small but powerful piece of safety equipment. It works by tearing in a controlled way to absorb energy, reducing the otherwise deadly forces of a fall. By extending the time and distance over which a fall is stopped, it protects the worker from injury or death.

But like all safety equipment, it’s only effective if it's well maintained, correctly used, and regularly inspected. Employers must ensure workers are trained in its function and limitations, and that systems are checked before every use.

When working at height, a shock absorber isn’t just a component—it’s a life-saving mechanism.