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

1. Lockout/Tagout Procedures

Lockout/Tagout Procedures

When servicing or moving a vehicle, it may have unknown but serious safety defects or conditions that prevent its operation. No oil in the crankcase or an engine undergoing an in-frame rebuild are common reasons to lockout and prevent an engine from starting Figure 9. To protect equipment, vehicles, and people from consequential damage from inadvertently starting, moving, or operating, lockout/tagout (LOTO) procedures are used. These two interchangeable terms describe an administrative safety procedure to prevent the use of tools, equipment, or materials that are determined to be unsafe or potentially unsafe or to prevent vehicles from starting during service. Lockout involves physically removing broken, unsafe, or out-of-service tools and storing them in a designated place to prevent access Figure 10. Typically, the item is also tagged with a warning label describing the fault, the name of the person who identified the fault, and the date that the fault was found. The tag or label also warns not to use the equipment. Keys are removed from the ignition and stored in another area, such as a supervisor’s or security office.

FIGURE 06-9: This control panel contains a switch that allows a technician to disconnect the driver’s ignition switch to prevent the engine from inadvertently starting when service work is taking place in the engine compartment.

FIGURE 06-10: LOTO procedures can apply to shop tools and equipment to warn others that they should not be used.

1.1. Video: Filling out a Defective Equipment Report

1.2. Video: Tagging Defective Equipment and Vehicles

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.

1.4. SKILL DRILL 6-1  Discharging a Capacitor

Capacitors are electrical energy storage devices used in places ranging from large, soda-can–shaped storage devices to smooth voltage fluctuations in audio systems, power supplementary restraint systems (airbags), direct current to direct current (DC to DC) voltage converters, or small ones to smooth alternator voltage output. To prevent potentially dangerous shock hazards, capacitors should be discharged before servicing a vehicle. Discharge techniques include the following: STEP 1 While using PPE, locate and remove the capacitor from a vehicle, and using a 12 V test light as a load, bridge the positive and negative terminals on the capacitor together. When the light goes out, the capacitor is discharged. Do not simply use a jumper wire to discharge the capacitor because high current discharge may damage the capacitor. The result of an electrical arc could also create an explosion hazard, produce a burn, and may even cause eye damage. STEP 2 Remove the fuse or disconnect the lead wire from the battery to any capacitor. Switch on the device supported by the capacitor to completely discharge the capacitor. When the device no longer operates, the capacitor is drained.     STEP 3 Disconnect the ground or negative terminal of the vehicle’s batteries and switch on the device supported by the capacitor (this may be as simple as turning the ignition switch to the RUN position). Once a device (such as the dome light) goes out, the capacitor is likely to be discharged. STEP 4 To determine if the capacitor is discharged, measure the voltage across the terminals of the capacitor or disconnected battery terminals. If the voltmeter shows near zero voltage, the capacitors connected to the ignition circuit are likely to have been safely discharged.