ALERT

• Follow OSHA regulations.
• Identify and label all sources of hazardous energy.
• Before beginning work, do the following:
  
  
  1. De-energize all sources of hazardous energy:
     —Disconnect or shut down engines or motors.
     —De-energize electrical circuits.
     —Block fluid (gas or liquid) flow in hydraulic or pneumatic systems.
     —Block machine parts against motion.
     
     
     1. Block or dissipate stored energy:
        —Discharge capacitors.
        —Release or block springs that are under compression or tension.
        —Vent fluids from pressure vessels, tanks, or accumulators—but never
        —Vent toxic, flammable, or explosive substances directly into the atmosphere.

     2. Lockout and tagout all forms of hazardous energy including electrical breaker panels, control valves, etc.

     3. Make sure that only one key exists for each of your assigned locks and that only you hold that key.

     4. Verify by test and/or observation that all energy sources are de-energized.

     5. Inspect repair work before removing your lock and activating the equipment.
        
        
     6. Make sure that only you remove your assigned lock.

     7. Make sure that you and your co- workers are clear of danger points before re-energizing the system.

  2. Participate in all training programs offered by your employers.

Only the worker who installs a lock and
tag should remove them after work is
complete and inspected.

Preventing Worker Deaths from
Uncontrolled Release of Electrical,
Mechanical, and Other Types of Hazardous Energy

This Alert describes five fatal incidents in which workers contacted uncontrolled hazardous energy during installation, maintenance, service, or repair work. To prevent such deaths, the recommendations in this Alert should be followed by every employer, manager, supervisor, and worker who installs, maintains, services, or repairs machines, equipment, processes, or systems. NIOSH requests that trade journal editors, safety and health officials, and others responsible for worker safety and health bring this Alert to the attention of employers and workers who are at risk.

Only the worker who installs a lock and
tag should remove them after work is
complete and inspected.

Number of Workers Killed

No detailed national data are available on the number of workers killed each year by contact with uncontrolled hazardous energy. However, during the period 1982-1997, NIOSH investigated 1,281 fatal incidents as part of their FACE Program. Of these, 152 involved installation, maintenance, service, or repair tasks on or near machines, equipment, processes, or systems. Because the FACE program was active in only 20 States between 1982 and 1997, these fatalities represent only a portion of the U.S. workers who were killed by contact with uncontrolled hazardous energy.

Contributing Factors

Review of these 152 incidents suggests that three related factors contributed to these fatalities:

• Failure to lockout and tagout energy control devices and isolation points after de-energization (11% of the incidents, or 17 of 152)

• Failure to verify that the energy source was de-energized before beginning work (7% of the incidents, or 11 of 152)

In a study conducted by the United Auto Workers (UAW), 20% of the fatalities (83of 414) that occurred among their members between 1973 and 1995 were attributed to inadequate hazardous energy control procedures specifically, lockout/tagout procedures. The energy sources involved in these fatalities included kinetic, potential, electrical, and thermal energy [UAW 1997].

Current Occupational Safety and Health Administration (OSHA) standards for general industry are established to prevent injuries and fatalities from contact with hazardous energy [29 CFR* 1910.147]. This standard requires employers to "establish a program consisting of energy control procedures, employee training and periodic inspections to ensure that before any employee performs any servicing or maintenance on a machine or equipment where the unexpected energizing, start up or release of stored energy could occur and cause injury, the machine or equipment shall be isolated from the energy source, and rendered inoperative."

Other OSHA standards for general industry cite the need for de-energizing electrical energy and locking and tagging electrical circuits and equipment before performing maintenance and servicing tasks. The following OSHA standards contain lockout/tagout-related requirements:

OSHA standards for construction also contain requirements for protecting workers from electrical hazards [29 CFR 1926.416 and 29 CFR 1926.417]. These standards require that workers exposed to any part of an electrical power circuit be protected through de-energizing and grounding of the circuit or through appropriate guarding. These standards also require that all de-energized circuits be rendered inoperable and tagged out.

Workers may be exposed to hazardous energy in several forms and combinations during installation, maintenance, service, or repair work. A comprehensive hazardous energy control program should address all forms of hazardous energy [NIOSH 1983]:

• Potential energy stored in pressure vessels, gas tanks, hydraulic or pneumatic systems, and springs (potential energy can be released as hazardous kinetic energy)

• Electrical energy from generated electrical power, static sources, or electrical storage devices (such as batteries or capacitors)

• Thermal energy (high or low temperature) resulting from mechanical work, radiation, chemical reaction, or electrical resistance

As part of the FACE Program from 1982 through 1997, NIOSH investigated 152 fatal incidents in which workers contacted uncontrolled hazardous energy. The following case reports summarize five of these investigations.

Case No. 1-Uncontrolled Kinetic Energy

A 25-year-old male worker at a concrete pipe manufacturing facility died from injuries he received while cleaning a ribbon-type concrete mixer. The victim's daily tasks included cleaning out the concrete mixer at the end of the shift. The clean-out procedure was to shut off the power at the breaker panel (approximately 35 feet from the mixer), push the toggle switch by the mixer to make sure that the power was off, and then enter the mixer to clean it.

No one witnessed the event, but investigators concluded that the mixer operator had shut off the main breaker and then made a telephone call instead of following the normal procedure for checking the mixer before anyone entered it. The victim did not know that the operator had de-energized the mixer at the breaker. Thinking he was turning the mixer off, he activated the breaker switch and energized the mixer. The victim then entered the mixer and began cleaning without first pushing the toggle switch to make sure that the equipment was de-energized. The mixer operator returned from making his telephone call and pushed the toggle switch to check that the mixer was de-energized. The mixer started, and the operator heard the victim scream. He went immediately to the main breaker panel and shut off the mixer.

Within 30 minutes, the emergency medical service (EMS) transported the victim to a local hospital and then to a local trauma center. He died approximately 4 hours later [NIOSH 1995].

Case No. 2-Uncontrolled Electrical Energy

A 53-year-old journeyman wireman was electrocuted when he contacted two energized, 6.9 -kilovolt buss terminals. The victim and two coworkers (all contract employees) were installing electrical components of a sulfur dioxide emission control system in a 14-compartment switch house.

The circuit breaker protecting the internal buss^† within the switch house had been tripped out and marked with a tag—but it had not been secured by locking. This procedure was consistent with the hazardous energy control procedures of the power plant.

The victim and his coworkers were wiping down the individual compartments before a prestartup inspection by power plant personnel. Without the knowledge of the victim and his coworkers, power plant personnel had energized the internal buss in the switch house. When the victim began to wipe down one of the compartments at the south end of the switch house, he contacted the A-phase buss terminal with his right hand and the C-phase buss terminal with his left hand. This act completed a path between phases, and the victim was electrocuted.

A coworker walking past the victim during the incident was blown backward by the arcing and received first-degree flash burns on his face and neck. A second coworker at the north end of the switch house heard the explosion and came to help. He notified the contractor's safety coordinator by radio and requested EMS. The EMS responded in about 15 minutes and transported the victim to a local hospital emergency room where he was pronounced dead [NIOSH 1994].

Case No. 3-Uncontrolled Kinetic Energy

A 38-year-old worker at a county sanitary landfill died after falling into a large trash compactor used to bale cardboard for recycling. The cardboard was lifted 20feet by a belt conveyor and fed through a 20- by 44-inch opening into a hopper. The hopper had automatic controls that activated the baler when enough material collected in the baling chamber. When the baler was activated, material in the chamber was compressed by a ram that entered the chamber from the side. Excess material above the chamber was trimmed by a shearer.

On the day of the incident, cardboard jammed at the conveyor discharge opening. Without stopping, de-energizing, or locking out the equipment, the victim rode the conveyor up to the discharge opening to clear the jam. He fell into the hopper and the baling cycle was automatically activated, amputating his legs. The victim bled to death before he could be removed from the machine [Colorado Department of Public Health and Environment 1994].

Case No. 4-Uncontrolled Potential Energy

The 32-year-old owner of a heavy equipment maintenance business died after a wheel and tire assembly exploded during repair work. The victim was removing the assembly from a test roller when it exploded and struck him with the flying split rim of the wheel.

The test roller was a large, two-wheeled cart that carried about 60,000 pounds of concrete weights. The roller was used in highway construction to test road surfaces for proper compaction.

The victim had been working as a subcontractor to repair the wheel and tire assembly, which had been smoking earlier in the day and was believed to be rubbing against the concrete weights. The assembly consisted of a two-piece outside rim and an inside ring retainer that was held together and mounted on the axle by 20 wheel bolts and nuts. Normal air pressure for the mounted tire was 70 psi.

The victim raised and blocked the roller. Without discharging the air from the tire and using no personal protective equipment, he began to remove the wheel nuts using a pneumatic impact wrench. He had no training or experience with this type of work or in the servicing of this type of wheel. He did not realize that only some of the bolts held the wheel tire assembly to the axle. The remainder held the outer half of the rim to the inside half, securing the tire to the wheel. As the victim removed the nineteenth wheel nut, the pressurized air in the tire discharged explosively, causing the split rim to fly off the wheel and strike him. He died from cerebral contusions and lacerations [Minnesota Department of Health 1992].

Case No. 5-Uncontrolled Kinetic and Thermal Energy

A 33-year-old janitorial worker died after he was trapped inside a linen dryer at a hospital laundry while cleaning plastic debris from the inside of the dryer drum. The cleaning task (which usually took 15 minutes to an hour) involved propping open the door to the dryer with a piece of wood and entering the 4- by 8-foot dryer drum. The melted debris was removed by scraping and chiseling it with screwdrivers and chisels. The dryer was part of an automated system that delivered wet laundry from the washer through an overhead conveyor to the dryer, where it was dried during a 6-minute cycle with air temperatures of 217^° to 230^°F. The system control panel was equipped with an error light that was activated if the dryer door was open, indicating that the dryer was out of service.

On the night of the incident, the victim propped the door open and entered the dryer drum without de-energizing or locking out the dryer. He began to clean the inside of the drum. Although the error light had been activated when the door was propped open, the signal was misinterpreted by a coworker, who restarted the system. When the system was restarted, the overhead conveyor delivered a 200-pound load of wet laundry to the dryer—knocking out the wooden door prop, trapping the victim inside, and automatically starting the drying cycle. The victim remained trapped inside until the cycle was completed and was discovered when the load was discharged from the dryer. He died thirty minutes later of severe burns and blunt head trauma [Massachusetts Department of Public Health 1992].

Review of the NIOSH FACE data indicates that three related factors contribute to injuries and deaths that occur when workers perform installation, maintenance, service, or repair work near hazardous energy sources:

• Failure to lockout and tagout energy control devices and isolation points after the hazardous energy source has been de-energized
  
• Failure to verify that the hazardous energy source was de-energized before beginning work

These fatalities could have been prevented if comprehensive hazardous energy control procedures had been implemented and followed.

NIOSH recommends that employers implement the following steps to prevent injuries and deaths of workers who must work with hazardous energy in their jobs: