Mechanical Equipment Rules for Qualified Workers

Workers performing tasks involving mechanical equipment near energized power lines and equipment have exposure to hazardous step and touch potentials. In the preamble to OSHA 29 CFR 1910.269 and 1926 Subpart V, the agency describes 19 fatalities that involved derrick trucks, aerial lifts and other machines. These fatalities occurred when contact was made between live parts and mechanical equipment. 

OSHA’s mechanical equipment standard was developed specifically to apply to operations performed by qualified workers when tasks are performed near energized power lines and equipment. Rules that apply to unqualified workers can be found within 1926 subparts N, O and CC, as well as within 1926.600(a)(6) and applicable 1910 General Industry standards. 

Standard Requirements

Four major requirements can be found in 1910.269(p) and 1926.959, both titled “Mechanical equipment.” They address the following: 

  1. General requirements relating to the operation of mechanical equipment.
  2. Use and operation of outriggers.
  3. Applied loads relating to maximum load ratings.
  4. Operation near energized lines or equipment relating to protecting workers from hazardous step and touch potentials. 

General Requirements

The standard requires a thorough visual inspection of the critical safety components of mechanical equipment before use on each shift. Critical safety components are defined as any part for which failure would result in freefall or free rotation of the boom. Employers must determine the best methods to ensure each inspection is thorough as failure of these parts would immediately pose serious hazards to workers. 

The general requirements also prohibit a line-truck operator from leaving the controls while a load is suspended. OSHA does allow an exemption when the employer can demonstrate that no worker, including the operator, would be endangered if the operator left the position. Operators must be able to maintain focus and be available at the controls should an emergency occur that requires the suspended load to be moved. Examples include wind or unstable soil creating conditions that could cause the equipment to tip over. Having an operator at the controls provides for immediate action to be taken to prevent a tip-over incident. 


Outriggers are required to be used when equipment is equipped with them. OSHA has cited several incidents involving equipment that overturned because outriggers were not appropriately utilized. Note: This rule does offer an exception when the work area or terrain may preclude the use of outriggers. If the exception is utilized, the equipment may be operated only within its maximum equipment load as specified by the equipment manufacturer. 

Additionally, outriggers must not be extended or retracted outside the clear view of the operator unless all workers are outside the range of possible motion. This is an extremely important rule that will prevent serious foot- and other body-crushing incidents that can occur when outriggers are extended. 

Applied Loads

Mechanical equipment must be used within its maximum load rating and design limitations for the conditions under which it is being utilized. It is important for workers to know manufacturer requirements as equipment has various applications in various environments. Understanding the design limitations and how to apply safe work practices can prevent serious lifting equipment failures that can cause harm to workers. 

Operation Near Energized Lines or Equipment

This standard includes requirements for maintaining minimum approach distances, rules for designating observers to provide timely warnings, and extra precautions to prevent exposure to hazardous differences of electrical potential when operating mechanical equipment.

Minimum Approach Distances

Operators must maintain MADs when operating mechanical equipment near exposed energized lines and equipment, with an exception that allows for the insulated portion of the aerial lift to work within the MAD. OSHA considers the insulated portion of an aerial lift to be the portion that is on the end of the insulated boom section farthest from the vehicle supporting the aerial lift. It should be noted that the insulating portion of a boom can be bridged by improper positioning of the boom or by conductive objects suspended from the aerial lift platform. For example, the insulating portion of the boom will be bridged when it is resting against a pole or when a worker in an aerial lift is holding on to a grounding jumper. Booms that are bridged are considered an uninsulated portion. 

MAD is required to be maintained between the uninsulated portion of an aerial lift and exposed objects. It is important to consult the equipment manufacturer to determine what should be considered insulated and uninsulated portions.

Designated Observers

The standard requires a designated observer, other than the mechanical equipment operator, to observe MAD requirements and provide timely warnings before MAD is reached. An employer does have the option to utilize the operator if they can successfully demonstrate that the operator can accurately determine MAD is being maintained. OSHA states that it may be difficult to determine distances between objects that are relatively far away from an equipment operator. Visual perspectives can lead to different estimates of distance, and lack of a suitable reference point can lead to errors. 

Extra Precautions

This portion of the standard is designed to ensure protection from hazardous step and touch potentials. OSHA refers readers to Appendix C of 1910.269 and 1926 Subpart V, “Protection from Hazardous Differences in Electric Potential,” to better understand these hazards. 

It is important to use the standard as you would the hierarchy of controls. OSHA’s intent is that each employer protects workers from hazards that could arise from mechanical equipment contacting energized lines and equipment. 

So, which workers must be protected? These include workers performing tasks on the ground and when a worker is climbing on or crossing over equipment, such as a pole trailer, during the time of energization. 

Let’s review the extra precaution requirements. First, if the mechanical equipment could become energized, the energized lines must be covered with insulating protective material or the equipment must be insulated for the voltage involved. Using appropriate insulation greatly reduces the possibility of equipment becoming energized. 

Second, employers must be able to demonstrate that all methods used will protect each worker from electrical hazards that could occur if the equipment contacts the line. If employers cannot eliminate or greatly reduce step and touch potential hazards, all of the following techniques must be used. 

  • Equipment grounding: Use the best available ground to minimize the amount of time the lines remain energized. Equipment grounding is used to quickly operate protective devices to take the electric system out of service. It provides little to no protection for ground workers as they could easily be at a difference of potential when standing on the ground and touching the equipment when it is energized. OSHA uses equipment grounding as a protective measure against electric shock when it is combined with the other techniques listed here. 
  • Bonding: Equipment must be bonded together to minimize potential differences. Take into consideration trailers, equipment work platforms, winch reels and multiple pieces of mechanical equipment in the workspace. 
  • Ground mats: Provide ground mats to extend areas of equipotential. Take into consideration whether a worker operates the equipment or performs work from the ground, which would put the worker at a difference of potential if the equipment were energized. 
  • Insulating protective equipment or barricades: Provide insulating protective equipment or barricades to guard against any remaining hazardous potential differences. PPE is always considered the last line of defense, so rubber insulating gloves, dielectric footwear and so forth should be used to provide protection in case all else fails. It is important to remember that barricades used within this standard are to protect workers and should be utilized to prevent workers from entering areas with potential step and touch hazards.


Electric power organizations have a responsibility to provide effective hazard control processes. Among other things, these processes must be able to be used to identify and control hazardous differences of electrical potential created when mechanical equipment becomes energized. 

About the Authors: Pam Tompkins, CUSP, CSP, is president and CEO of SET Solutions LLC. She is a 40-year veteran of the electric utility industry, a founding member of the Utility Safety & Ops Leadership Network and past chair of the USOLN executive board. Tompkins worked in the utility industry for over 20 years and has provided electric power safety consulting for the last 20-plus years. An OSHA-authorized instructor, she has supported utilities, contractors and other organizations operating electric power systems in designing and maintaining safety improvement methods and strategies for organizational excellence. 

Matt Edmonds, CUSP, CIT, CHST, is vice president of SET Solutions LLC. A published author with over 15 years of safety management experience, he also is an OSHA-authorized instructor for general industry and construction standards. Edmonds provides specialty safety management services for electric power organizations throughout the U.S. He has been instrumental in the development of training courses designed for electric power organizations, including OSHA 10- and 30-hour courses and SET Solutions’ popular OSHA Electric Power Standards Simplified series. 

About OSHA Electric Power Standards – Simplified: Topics in this series are derived from SET Solutions’ popular OSHA electric power course offered through the Incident Prevention Institute (https://ip-institute.com). The course is designed to help learners identify standard requirements and to offer practical ways to apply the standards.

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