Massachusetts Public Utility Lineman Dies of Thermal Burns When Aerial Lift Hydraulic Hoses Ruptured and Ignited

MA-92-01
DATE: July 13, 1993

SUMMARY

A 53 year-old electrical lineman died from burns suffered while repairing a damaged utility pole. The victim was in a cherry picker bucket of an articulating line truck (ALT) at the time of the incident. Hydraulic fluid, which flowed through hoses, raised and lowered the bucket. Company and OSHA officials speculated that a massive short-circuit burned through the hoses and ignited hydraulic fluid, engulfing the victim and the bucket in flames.

The MA FACE Investigator concluded that to prevent similar occurrences in the future, employers and/or equipment, vehicle and hose manufacturers should:

• ensure that all power lines are de-energized, when practical, prior to working in their vicinity.
• continue research into the development of non-flammable, non-conductive hydraulic fluids.
• research the use of hydraulic hoses constructed of materials that will not fail when exposed to high voltage hazards.
• research the development of a lift system that shuts off the flow of hydraulic fluid in the event of a line rupture.

INTRODUCTION

On Wednesday November 13, 1991, the Massachusetts Department of Labor and Industries informed the MA FACE Field Investigator of the death of a public utility lineman who was critically injured on the previous day. After conferring with the National Institute for Occupational Safety and Health (NIOSH) about a death due to similar circumstances in another state, the MA FACE Investigator initiated an investigation.

On December 11th, the MA FACE Investigator reviewed the incident site and met with public utility representatives, a Massachusetts Department of Labor and Industries Inspector and a police department representative. The MA FACE Investigator also obtained incident-site photographs, the OSHA incident narrative, police records, and the death certificate during the course of the investigation. The public utility did not authorize free access to damaged equipment or company records.

The employer was a public electric utility employing 2,000 workers. Two hundred and fifty workers were employed in the victim's geographic region. One hundred of these workers were employed in his division. The victim was 53 years old and had worked for the utility company for 31 years.

The company maintained a written, comprehensive safety and health program and employed designated safety personnel. The company communicated safety and health provisions to employees, routinely enforced these provisions, and provided related training accordingly. Company linemen also received first aid training and CPR courses bi-annually. The utility company also maintained a safety manual, hazard communication program, MSDS's (Material Safety Data Sheets), tie wrap wire process information, and a log of company related accidents/illnesses.

INVESTIGATION

Late at night on November 11 1991, a hit and run driver badly damaged a public utility pole. The utility company dispatched a troubleshooter who assessed the damage and reported back to his supervisor. The company determined that the situation did not warrant the de-energizing of the lines and dispatched three linesmen at 12:15 a.m. on November 12 to perform necessary repairs. The public utility described the incident system as being three phase, 13.8 kV line to line, with 7,967 volts line to ground. The massive short circuits netted total collapse of all three phases.

The linemen determined that a new replacement pole needed to be installed and positioned their equipment accordingly. Their equipment included one leased articulating line truck (ALT) with a bucket, and one leased ALT with a bucket and a pole lifting device. The workers put on personal protective equipment, including hard hats, safety eye wear, protective gloves and safety belts, and then set up appropriate area night lighting.

Following the preparation of a hole for the new pole, lineman 1 used the ALT without a pole lifting device to go up one side of the broken pole. He installed line hoses and a new ridge/top pin. Lineman 2 remained on the ground assembling a cross arm for the new pole. Lineman 3 (victim) used the ALT with the pole lifting device to go up the east side of the broken pole. He installed line hoses on the outer two phases.

During the repair, a tie wrap wire became stuck. Lineman 1 maintained tension on the wire, while the victim (lineman 3) freed the wire. As the victim slid the tie wrap toward him, there was a blast (fault). The blast ruptured the victim's ALT lift system hoses and ignited the hydraulic fluid engulfing the victim and his ALT bucket in flames. Lineman 1 reached over and attempted to put out the fire, but a second fault required lineman 1 to seek cover within his own bucket. Despite the explosions, the lift system on the victim's ALT continued to pump hydraulic fluid, further engulfing the victim and ALT bucket in flames.

Lineman 2, the ground lineman, attempted to lower the victim to the ground, but the hydraulic system eventually failed with the bucket nine feet from the ground. At this point, the victim either fell or jumped out of the bucket. The victim was severely burned from the waste up, with his clothing and hair burned away. He remained conscious and aware of what was happening around him. Neighbors came from their homes offering assistance. Police personnel who responded instructed neighbors to stay clear of the downed wires. The fire department and an ambulance also came to the scene and transported the victim to the regional hospital. He died approximately 22 hours later.

The direct cause of the short circuit could not be determined. It is most probable that live wires, broken or loosened during the car crash, were involved. It also seems likely that molten metal from this short circuit burned through the hose of the ALT hydraulic lift system which ignited flammable hydraulic fluid that set the victim afire.

CAUSE OF DEATH

The Medical Examiner listed the cause of death as thermal burns and complications.

RECOMMENDATIONS/DISCUSSION

Recommendation #1: Employers should ensure that all power lines are de-energized, when practical, prior to working in their vicinity.

Discussion: At the time of the incident the circuitry on the damaged pole remained fully operational. Based on the assessment of the dispatched trouble shooter, the decision was made that the crew would perform repairs on live lines despite the fact they could have been de-energized. It is recommended that, as the primary safety measure, all lines and conductors in the work area be de-energized before working on or near them. Given the ever present hazards associated with work on live electrical systems, such systems should be shut down, when practical, so that necessary repairs can be safely carried out.

Recommendation #2: Employers and/or equipment, vehicle, and hose manufacturers should continue research into the development of non-flammable, non-conductive hydraulic fluids.

Discussion: There are currently two types of fire resistant hydraulic fluids: synthetic-based mixtures, and water-based mixtures. Unfortunately, neither are both non-flammable AND non-conductive. Given the availability and widespread use of non-flammable fluids in hydraulic tools nationwide, research must continue to develop non-flammable, non-conductive hydraulic fluids for vehicles used in electrical utility work.

Recommendation #3: Employers and/or equipment, vehicle, and hose manufacturers should research the use of hydraulic hoses constructed of materials that will not fail when exposed to high-voltage hazards.

Discussion: The destruction of the ALT hose(s), which carried the flammable hydraulic fluid, contributed to the fatal fire. Manufacturers and employers using ALT's, should research and/or develop hose technology that is designed to withstand exposure to high-voltage and other possible hazards. It is conceivable, that the actual short circuit could have been associated with the hydraulic hose itself, if for example the rubber became abraded away and a stainless braid became exposed. The use of non-conductive (electrical insulating) braid and/or additional abrasion protection for hose and metal fittings would minimize the potential for a short circuit, and therefore the fire. This is the same approach that is used in ALT construction whereby the bucket, beams, tools, etc. are constructed using non-conductive materials.

Recommendation #4: Employers and/or equipment, vehicle, and hose manufacturers should conduct research into the development of a lift system that shuts off the flow of hydraulic fluid in the event of a line rupture.

Discussion: A system designed to automatically stop or restrict the flow of hydraulic fluid once the line has malfunctioned or been compromised would create a means of minimizing the effects of the malfunction. If indeed a line rupture were to occur, only the fluid escaping at the site of rupture, while immediate present pressure is relieved, would be of significance. In the event of an incident, the control valve would allow the bucket worker and/or the ground person to immediately shut off the supply of hydraulic fluid fueling the fire.

REFERENCES

1. Office of Federal Register: Code of Federal Regulations, Labor 29 Part 1926.302 (d) (1) 1990
2. Hydraulics for Off-Road Equipment, Second Edition, Chapter Seven, "Hydraulic Fluids," p. 168. Theodore Audel & Co., div. of GK Hall & Co., Boston, Massachusetts. Copyright 1985.

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