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Course 726 - Introduction to Machine Guarding

Safety guides and audits to make your job as a safety professional easier

Machinery Maintenance and Repair


Good maintenance and repair procedures contribute significantly to the safety of the maintenance crew as well as that of machine operators. The variety and complexity of machines to be serviced, the hazards associated with their power sources, the special dangers that may be present during machine breakdown, and the severe time constraints often placed on maintenance personnel all make safe maintenance and repair work difficult.

Hazard Identification and Reporting

You will learn where potential trouble is if you listen to the machine operators.
You will learn where potential trouble is if you listen to the machine operators.

Training and aptitude of people assigned to these jobs should make them alert for the intermittent electrical failure, the worn part, the inappropriate noise, the cracks or other signs that warn of impending breakage or that a safeguard has been damaged, altered, or removed.

By observing machine operators at their tasks and listening to their comments, maintenance personnel may learn where potential trouble spots are and give them early attention before they develop into sources of accidents and injury.

Sometimes all that is needed to keep things running smoothly and safely is machine lubrication or adjustment. Any damage observed or suspected should be reported to the supervisor; if the condition impairs safe operation, the machine should be out of service for repair. Safeguards that are missing, altered, or damaged also should be reported so appropriate action can be taken to insure against worker injury.

1. What should workers do first if they discover or suspect any damage to machinery?

a. Bypass reporting and immediately fix the problem
b. Report it immediately to the supervisor
c. Immediately place the machinery out of service
d. If it's not in your department, just ignore it

Next Section

Maintenance and repair crews must never fail to replace the guards before the job is considered finished and the machine released from lockout.
Replace the guards and make sure the machine is released from lockout.

Machine Guard Design Considerations

If possible, machine design should permit routine lubrication and adjustment without removal of safeguards. But when safeguards must be removed, and the machine serviced, the lockout procedure of 29 CFR 1910.147 must be adhered to.

The maintenance and repair crew must never fail to replace the guards before the job is considered finished and the machine released from lockout.

If it is necessary to oil machine parts while a machine is running, special safeguarding equipment may be needed to protect the oiler from exposure to hazardous moving parts.

Maintenance workers must know which machines can be serviced while running and which cannot. "If in doubt, lock it out." Obviously, the danger of accident or injury is reduced by shutting off and locking out all sources of energy.

2. What is required if safeguards must be removed when a machine is serviced?

a. Lockout/Tagout (LOTO) procedures
b. Maintenance inspection of all parts
c. Through lubrication and cleaning
d. Job Hazard Analysis (JHA)

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Sources of Hazardous Energy During Maintenance and Repair

Maintenance and repair crews must never fail to replace the guards before the job is considered finished and the machine released from lockout.
All power sources must be shut off and locked out before maintenance work begins if workers are exposed to electrical elements or hazardous moving machine parts

In situations where the maintenance or repair worker would necessarily be exposed to electrical elements or hazardous moving machine parts in the performance of the job, there is no question that all power sources must be shut off and locked out before work begins. Warning signs or tags are inadequate insurance against the untimely energizing of mechanical equipment

Thus, one of the first procedures for the maintenance person is to disconnect and lock out the machine from all of its power sources, whether the source is electrical, mechanical, pneumatic, hydraulic, or a combination of these. Energy accumulation devices must be "bled down."

Electrical Energy Hazards

Unexpected energizing of any electrical equipment that can be started by automatic or manual remote control may cause electric shock or other serious injuries to the machine operator, the maintenance worker, or others operating adjacent machines controlled by the same circuit.

For this reason, when maintenance personnel must repair electrically powered equipment, they should open the circuit at the switch box and padlock the switch (lock it out) in the "off" position.

This switch should be tagged with a description of the work being done, the name of the maintenance person, and the department involved. When more than one worker is to be engaged in the servicing/maintenance function a lockout hasp may be used to which each may affix a personal lock.

3. What must occur if a maintenance worker could be exposed to electricity or hazardous moving machine parts?

a. All power sources must be shut off and locked out before work begins
b. An information tag must be placed at the point of operation
c. Each worker must inform others of the hazards
d. Moving parts must be noted and tagged

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Mechanical Energy Hazards

Figure 1 shows a safety block being used as an additional safeguard on a mechanical power press, even though the machine has been locked out. The safety block prevents the ram from coming down under its own weight.

Pneumatic and Hydraulic Energy Hazards

Figure 2 shows a lockout valve. The lever-operated valve used during repair or shutdown to keep a machine or its components from operating can be locked open or shut. Before the valve can be opened, everyone working on the machine must use his or her own key to release the lockout.

A sliding-sleeve valve exhausts line pressure at the same time it cuts off the air supply. Valves used to lock out pneumatic or hydraulic-powered machines should be designed to accept locks or lockout adapters and should be capable of "bleeding off" pressure residues that could cause any part of the machine to move.

Lock Out Valve
Figure 2: Lock Out Valve
Safety Blocks
Figure 1: Safety Blocks

4. Which of the following is used as an additional safeguard to protect against a mechanical energy (gravity) hazard even though the machine has been locked out?

a. A chain
b. A block
c. A lock
d. A tag

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Performing Lockout/Tagout Procedures

In order to prevent the hazards we have discussed, each machine or piece of equipment should be safeguarded during the conduct of servicing or maintenance by:

  1. notifying all affected employees (usually machine or equipment operators or users) that the machine or equipment must be shut down to perform some maintenance or servicing;
  2. stopping the machine;
  3. isolating the machine or piece of equipment from its energy source;
  4. locking out or tagging out the energy source;
  5. relieving any stored or residual energy; and
  6. verifying that the machine or equipment is isolated from the energy source.

Although this is the general rule, exceptions can be made when the servicing or maintenance is not hazardous for an employee, is minor in nature, is done as an integral part of production and the employer utilizes alternative safeguards which provide effective protection as is required by OSHA standards.

5. When machinery is about to be worked on, maintenance workers should notify _____.

a. all supervisory and management staff
b. only those employees exposed to hazards
c. affected employees operating or using the machinery
d. all employees working within the department

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Release from Lockout/Tagout Procedures


When the servicing or maintenance is completed, there are specific steps which must be taken to return the machine or piece of equipment to service. Use these steps:

  1. Inspect the machine or equipment to ensure all guards and other safety devices are in place and functional;
  2. Check the area to ensure reenergizing and starting-up the machine or equipment will not endanger employees;
  3. Remove the lockout devices;
  4. Reenergize of the machine or equipment; and
  5. Notify affected employees that the machine or equipment may be returned to service.

The steps to lockout described above are only a part of the total Energy Control Program (ECP) which must exist in the workplace. In addition, the employer should:

  • Develop procedures for all machines and equipment
  • Train employees in their duties and responsibilities under the ECP, and
  • Periodically inspect performance to maintain the effectiveness of the program

6. The first step for release from lockout/tagout is to _____.

a. remove the lockout devices
b. make sure all guards and devices are in place and functional
c. make sure reenergization does not endanger employees
d. notify affected employees about equipment return to service

Check your Work

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