Average vs. Maximum Arresting Force

During a webinar on fall protection equipment earlier this month, someone asked a great question at the very end of the session.  We’re posting it here to make sure that everyone interested has an opportunity to get the full answer.

Question: What is the difference between the average arresting force and maximum arresting force related to energy-absorbing lanyards?

Answer: Starting with the ANSI Z359.13 standard, several changes were made to how energy absorbers are tested.  Two of the significant changes include increasing the test weight from 220 pounds to 282 pounds and using an average arresting force instead of the maximum arresting force.  Regarding the second point, when a manufacturer tests an energy absorber, they capture data on how much load is applied to the anchorage.  This is then plotted on the vertical axis of a graph with time being shown on the horizontal axis.  For past standards, manufacturers were required to make sure all the data points fell under 900 pounds, hence the phrase, maximum arresting force. 

Starting with the ANSI Z359.13 standard, manufacturers now average all the data points from this test that are in excess of 500 pounds. Also, an individual data point cannot exceed 1,800 pounds, which is the maximum load that can be applied to a user in a full body harness per OSHA.  This change was made to account for the increased test weight since manufacturers needed ways to absorb or dissipate more energy.

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