"Work at Height Series: Article 2 :"Total Fall Distance (TFD) calculation for Fall Arrest Protection"!"

Total Fall Distance (TFD) calculation

When determining the requirements for fall arrest systems and Total Fall Distance (TFD) calculation, several factors need to be considered including the person's height, lanyard length, and the length of the deceleration device (shock absorber). To calculate the total distance required for fall arrest protection, we use the formula:

Total distance = Employee height + Lanyard length + Deceleration device length + Safety factor [usually 3 feet (considering 1 feet of harness stretch as well)]

For example, imagine an employee with a height of 6 feet working at a height where the anchor point is 20 feet from the ground level and the employee is wearing a body harness equipped with a 6-foot lanyard and a 3.5-foot shock-absorbing device.
We need to assess if this setup provides adequate fall arrest protection.
In the given example, the calculation would be:
Total distance = 6 feet + 6 feet + 3.5 feet + 3 feet = 18.5 feet

This means that the total distance required to prevent the employee from hitting the ground in the event of a fall is 18.5 feet. It's important to note that this calculation includes a safety factor of 3 feet to ensure a margin of safety.

Hence in this case, the employee working above 20 feet can safely use this fall arrest system which protects from hitting the ground due to a fall.

In summary, fall arrest systems play a crucial role in safeguarding workers at heights. Properly calculating the required distances based on factors like employee height, lanyard length, and deceleration device length ensures that the system effectively prevents the person from hitting lower levels during a fall.