Bpf101

Insulating link

An insulating link is a device used on the hook of crane to protect the crane operatives from the danger of electrocution should the crane come into contact with a power line.

Insulating links rely on the properties of insulators to prevent the flow of electricity from bare, suspended wires through cranes and into personnel working near the crane.

History

The dangers of working near overhead power lines, which have no insulation covering their wires, first became apparent with the electrification of Western countries in the first half of the twentieth century. As early as there was a patent for an insulator that could be affixed to a crane’s wire rope or chain in order to prevent electrocution. Such early designs, however, proved impractical because of their reliance on insulators such as glass, which could not tolerate the tension that was placed on the link. These problems meant that insulating links were not widely used until new designs were developed in the that relied on epoxy resin as their insulator.

By mandated the use of insulating links on cranes in the United States. However, this requirement was lifted in the 1980s after an investigation found that lethal levels of electrical current could pass through the insulating links in use at that time if they were wet or otherwise contaminated.

New developments in insulating link technology, that take account of the likelihood of insulating links being used in the typically dirty and wet construction industry environment, meant that the US Government introduced a new law (CFR29 part 1926 Cranes and Derricks in Construction) in 2010 that mandates the use insulating links in certain situations.

Purpose

Insulating links are typically needed on cranes and guide ropes that are used close to overhead power lines to protect against electrical current passing from the power line through the wire rope of the crane and into the personnel working on or near the crane. Incidents like this are common because of the difficulty the driver of the crane has in distinguishing the thin cable of the power line against the background of the sky. Accidents involving contact between a power line and a crane are invariably extremely seriously, often resulting in the serious injury or death of crane operative(s). In fact, on average 200 electrocutions occur each year in the US because of contact between a crane and a power line, while 20% of all fatalities in the US construction industry are due to cranes touching power lines. Electrocution because of power line contact is sufficient to cause ventricular fibrillation of the heart, often fatal, while the wound caused by the electrical current leaving the body will often remove legs or feet.

Grounding a crane is not effective, since enough current can still pass through crane operatives to be fatal. The only effective method of protecting people working on or near cranes is to use an insulating link that meets the UL standard ELRK and the ANSI standard UL2737.