False Connection Hazard Alert

Summary

The false connection between two components of a Fall Arrest Systems (FAS) and particularly between the back D-ring on a harness and the snap hook on a shock absorbing lanyard (or on a Self-Retracting Lifeline [SRL]), may come apart during fall arrest. This false connection occurs because of the dimensional incompatibility of the two connecting pieces which stay together only due to a friction fit. Such friction fit connections come apart during fall arrest, and subsequently the fall is not arrested at all. Note that both, the harness and the shock absorbing lanyard (or a Self-Retracting Lifeline [SRL]), might have been in full compliance with their respective standards.

The Hazard

What is it? Fall Arrest Systems are usually assembled by their users who connect several pieces of equipment (Fall Arrest System [FAS] components) using the connecting hardware. This hardware may either be integrally attached to this equipment (e.g.: snap hooks and D-rings) or it may be an independent component (e.g.: karabiners, anchorage connectors, etc.). When the inside diameter of a D-ring is dimensionally very close to the width of the head of the snap hook (or to the minor axis of a karabiner), the Fall Arrest System (FAS) user may end up with the false connection as illustrated in Figure 1. The Fall Arrest System (FAS) user who dons a harness and subsequently attempts to connect a lanyard (or an Self-Retracting Lifeline [SRL]) to the back D-ring, is unable to see how the snap hook connects with the back D-ring. Therefore, the resulting connection may only be a friction fit between the outer surface of the snap hook and the inside of the D-ring. Such connection may create an impression of a proper one because sometimes it takes more than hundred pounds [0.45 kN] to disconnect it. A force of such magnitude exceeds the force which the Fall Arrest System (FAS) user exerts when he/she checks the connection by pulling on the lanyard. However the force which keeps the false connection together is much lower than the Maximum Arrest Force (MAF), or the shock load which is generated on arrest of the fall. At that moment this false connection fails and the accident victim continues his/her fall and ends up hitting the level (or an object) below with all the potential consequences of such event.

Why does it exist? There are several reasons why two independently certified components can be falsely connected to each other:

1. Lack of the dimensional design requirements in standards for the connecting components for Fall Arrest Systems (FASs).
2. Users’ tendency to purchase Fall Arrest System (FAS) components from several suppliers, combined with users’ lack of knowledge about the False Connection Hazard. This is equivalent to some of the users becoming designers of Fall Arrest Systems (FASs) which they assemble from a large variety of available equipment. Each component when tested individually usually complies with its respective standard. However, a Fall Arrest System (FAS) is a system, and with thousands of available models and makes of equipment, there is practically an infinite number of Fall Arrest Systems (FASs) combinations and it is quite obvious that they all cannot possibly be tested.

Where can you experience it? This hazard exists in these Fall Arrest Systems (FASs) in which equipment from various manufacturers was assembled by a user (or by his/her supervisor or a safety officer) who is unfamiliar with this Hazard.

Who is affected by it and when? All users of Fall Arrest Systems (FASs) “designed” by unqualified personnel are at risk. Without the knowledge of this Hazard, the Fall Arrest System (FAS) designer may not be capable of developing proper purchasing specifications for the fall protection equipment.

It is quite common to see a company purchasing policy which requires buying from the lowest bidder. This policy may turn into a disaster when equipment thus purchased turns out to be incompatible with each other when it has to be assembled into a Fall Arrest System (FAS).

When purchasing specifications for fall protection equipment are not detailed to the extent which would prevent this incompatibility - the False Connection Hazard is just around the corner.

How to Eliminate It Or Minimize Its Consequences?

1. Re-evaluate all types, makes and models of hardware employed with your fall protection equipment for the False Connection Hazard. Out of a pair which demonstrates this Hazard, remove from use the one which is less expensive to replace.
2. Train all Fall Arrest System (FAS) users in checking their equipment for this Hazard.
3. Establish an equipment purchasing policy which will prevent acquiring incompatible Fall Arrest System (FAS) components.
4. Attempt, if feasible, to purchase all fall protection equipment from the same manufacturer.
5. Provide proper training in fall protection to all users of Fall Arrest Systems (FASs).
6. Always follow manufacturers’ User’s Instructions.

Additional Information and Comments

The False Connection Hazard was brought to the attention of the Canadian Standards Association’s Technical Committee on Fall Protection in August of 1993 by Mr. Norman Desjardins of Norguard Industries in Sudbury, Ontario [1]. Mr. Desjardins described an incident observed by one of the supervisors at a local nickel mine who noticed that one of the workers had his lanyard falsely connected to the D-ring on his harness. A continent wide alert was subsequently issued by the CSA Committee. Several organizations reportedly performed evaluation of Fall Arrest System (FAS) connectors which resulted in removing some of the equipment from use.

It will remain unanswered how many of the accidents which were previously attributed to the roll-out phenomenon, were actually caused by the false connection.

References

1. Desjardins, N.L., “Possible Hazard” Memorandum to the CSA TC on Fall Protection, August 12, 1993.
2. Sulowski, A.C., “Fall Arrest Systems - Practical Essentials”, Published by CSA International, January 2000, Toronto, Ontario, Canada.
3. Sulowski, A.C., McQuarrie R.H., “Evaluation of Connecting Hardware” Research Report, OHT, Toronto, 1994. Classified information.
4. ANSI Z359.1-1992 (R1999) American National Standard safety requirements for personal fall arrest systems, subsystems and components. American National Standards Institute Inc., New York, NY, and American Society of Safety Engineers, Des Plaines, IL.
5. “Qualified Inspector of Fall Protection Equipment” Seminar Manual, Sulowski Fall Protection Inc., Toronto, ON, 1997.
6. “The Fundamentals of Fall Protection” Seminar, CSA International, Toronto, ON, 1999.

Figures

Figure 1 - False Connection Hazard:

(a) present (friction fit), (b) absent