LO 6-2 Explain the purpose of lockout/tagout procedures and regulations associated with the release of hazardous energy

1.3. Occupational Health and Safety Administration LOTO Requirements

Occupational Health and Safety Administration LOTO Requirements

LOTO procedures are commonly used to disable machinery or equipment to prevent them from starting or to prevent the release of hazardous energy while employees perform service and maintenance activities. In the U.S., the Occupational Health and Safety Administration (OSHA) Standard 29 CFR 1910.147 covers LOTO protocols and is called the Control of Hazardous Energy . This standard requires safety-specific work procedures for LOTO to control the release of hazardous energy during the service and maintenance of machinery and equipment. Pressurized air, hydraulic or other gas pressure, electricity (stored in capacitors or available from batteries), and even objects such as a raised dump box acted upon by gravity are common examples of sources of stored energy Figure 11.

FIGURE 06-11: If the aftertreatment system is serviced on a dump truck when the box is raised, the box must be supported to prevent crushing a person or their arms and fingers.

FIGURE 06-12: A manual shutoff switch on the high-voltage (HV) energy storage system storage box has a feature to allow the switch to be locked off with a padlock.

A more relevant example where LOTO procedures apply prevents the energy storage system (ESS) in electric vehicles or starting system batteries from accidental release of current during maintenance. Commonly, a master switch that disconnects the ESS has a feature that allows a physical padlock or tie wrap to hold the switch in the OFF position and prevent normally open relays in the storage system from becoming energized and closing Figure 12. Remote keyless entry systems with frequency operated buttons (FOBS) should be stored and locked down far away from a vehicle to prevent unintended operation that could start the vehicle or energize the ESS.

The OSHA standard allows each employer some flexibility to develop an energy control program suited to the needs of their particular workplace and according to the types of machines and equipment being maintained or serviced. Tagout clearly labels the power source of the system undergoing maintenance. In addition to the example of electric vehicles, LOTO can be applied when the hydraulic or pneumatic position of a particular piece of equipment could change Figure 13. Even the effects of gravity must be considered by shop procedures Figure 14. Employees must be instructed to ensure that they know, understand, and follow the shop’s hazardous energy control procedures. Common procedures to deplete stored energy hazards include:

• Disconnecting the vehicle or machine batteries and discharging any capacitors before starting to work on a vehicle Skill Drill 6-1
• Draining air reservoirs for air brake and auxiliary air systems
• Shutting off all hydraulic or pneumatic pumps and compressors, lockout or tagout the valve supplying energy to the piece of equipment being serviced
• Draining/bleeding stored pressure in hydraulic/pneumatic lines if the release of stored energy could cause injury to employees
• Verifying that hydraulic and mechanical controls are in their safest position
• Using purpose-made safety mechanical supports for dump boxes, hoods, and hydraulic cylinders
• Evacuating air-conditioning refrigerant
• Depressurizing common rail fuel systems Figure 15

FIGURE 06-13: This shunt truck with a tilt cab elevated by a hydraulic cylinder ram represent examples of gravity-stored energy that can potentially release and injure a worker performing engine work.

FIGURE 06-14: To access the engine compartment of this loader, the bucket is raised and the hydraulic cylinders are supported by brackets locked in place.

FIGURE 06-15: High-pressure common rail systems can transmit pressurized fuel with lethal force.