Solution Summary: Using Cover-Up Equipment
Cover-up equipment is a work practice that can protect workers from contacting energized conductors and is recommended for use on all high-voltage line maintenance and underground tasks. Using cover-up equipment provides maximum protection from electrocution for workers by creating a barrier against the flow of electrical current. A wide variety of cover-up equipment is available to help line workers perform live-line work safely and productively. Cover-up equipment should be used in conjunction with PPE as well as hot sticks when applicable.
Insulating covers are categorized into four types: Cutout Cover, Deadend Cover, Conductor and Insulator Cover, and Pole Covers. All types are constructed, tested, and maintained based on ASTM standards and OSHA regulations.
A cutout cover is used to protect line workers near open-type cutouts that are rated less than 25 kV. Cutout covers comply with current ASTM D 1049 and ASTM F712 specifications. The flexible type of cutout covers can be used for both overhead cutouts and underground pad-mounted equipment.
Figure 1. Cutout Covers: (a) 25 kV Phase-to-Phase; (b) Flexible rubber cover (www.hubbellpowersystems.com)
A deadend cover fits over conductors and insulators. This cover can join to conductor covers and rubber line hoses, thereby extending the protected area. This cover can be installed either using clamp sticks or by hand, using rubber gloves and sleeves. However, use of a combination of both methods is recommended. Acceptable use of this cover is up to 25 kV.
Figure 2. Deadend Cover: (a) 25 kV Phase-to-Phase; (b) Using deadend covers in conjunction with rubber blanket and conductor cover (www.hubbellpowersystems.com)
Conductor and Insulator Cover
Conductor and insulator covers can cover up energized power lines and provide maximum protection from electrocution for line workers. These covers can be coupled with deadend covers on one end and line hoses on the other to extend protected areas. The ASTMF712 is used to test specifications for these covers.
Figure 3. Conductor and Insulator Cover: (a) 25 kV Phase-to-Phase and different types of insulator covers; (b) Applying covers on horizontal post and crossarm construction (www.hubbellpowersystems.com)
Pole covers are used to protect a line worker when s/he is raising or lowering a pole between lines that are energized. These covers are ribbed to reduce contact points with any energized piece of equipment in order to increase the life span of the cover.
Figure 4. (a) Pole Cover: 36.6 kV Phase-to-Phase; (b) Removing pole cover from a new power pole (hubbellpowersystems.com;http://medinagazette.northcoastnow.com)
Since the cover-up equipment does not completely eliminate the risk of electrical incidents, the listed standard OSHA guidelines must be followed even when using cover-up equipment. According to OSHA 1910.269(l)(2)(i), at least two employees must be present while any employees perform the following types of work on power lines:
- "Installation, removal, or repair of lines energized at more than 600 volts [OSHA 1910.269(l)(2)(i)(B)]
- Installation, removal, or repair of de-energized lines if an employee is exposed to contact with other parts energized at more than 600 volts [OSHA 1910.269(l)(2)(i)(C)]
- Installation, removal, or repair of equipment, such as transformers, capacitors, and regulators, if an employee is exposed to contact with parts energized at more than 600 volts [OSHA 1910.269(l)(2)(i)(D)]
- Work involving the use of mechanical equipment, other than insulated aerial lifts, near parts energized at more than 600 volts. [OSHA 1910.269(l)(2)(i)(E)]"
Qualified line workers must install cover-up equipment. It serves as temporary insulation between workers and energized lines. Cover-up equipment with phase-to-phase voltage ratings (ASTM Class 00-600V to Class 6-72.5kV) is available for multiple applications. The voltage of two covers cannot be added to achieve higher voltage ratings.
Electrical hazards are among the main construction industry hazards that cause serious injuries and death. Contact with electric current is a major cause of injury and death among construction workers (Janicak 2008). In 2012, the Census of Fatal Occupational Injuries (CFOI) data produced by the Bureau of Labor Statistics (BLS) indicated that contact with electric current was the fourth leading cause of work related deaths—after falls, transportation incidents, and contact with objects and equipment (BLS 2012). Electricity can cause electric burns, electrocution, shock, arc flash/blast, fires, and explosions. Overhead power lines are particularly hazardous since they carry high-voltage electricity. One of the major causes of an electrocution hazard is contact with overhead power lines and energized sources. Although electrocution is considered the main risk, other important hazards of working near or on high-voltage lines include electrical shock, burns, and falls to lower levels. These types of hazards happen when the body becomes part of the electric circuit, whether by direct contact with an energized source or by contact with a conductive material that has become energized. The severity of the electrical hazard depends on several factors, including the length of exposure time, energy deposited into the body, the pathway through the body, wetness or dryness of the surface and the amount of current. The best and preferred method of control is to keep a safe distance from power lines. Table 1 shows the minimum safe distance for various line voltages.
Table1. minimum powerline clearance distances (Source: 29 CFR 1926.1408(h))
Properly used covers can prevent worker injury and death from electrocution, electric shock, burns and falls by providing protection from accidental contacts with live parts. Although these insulators properly cover the live parts, workers must also use proper personal protective equipment (PPE). Cover-up equipment used in conjunction with a line hose covers insulators and conductors, thus increasing a worker’s protection against accidental contact with high-voltage lines.
How Risks are Reduced:
As workers ascend to their working positions, they should place insulator covers on all conductors that may present electrical hazards. Insulating covers cover wire conductors and prevent them from coming in contact with each other, tools or people. Using covers creates a barrier against the flow of electrical current. Guarding the energized lines with properly maintained covers is a safe practice to prevent line workers from accidentally coming into contact with live parts, significantly decreasing the risk of electrical accidents.
Effects on Productivity:
By using cover-up equipment, line workers can work on live lines, eliminating the risk of accidental contact with live parts. Moreover, there is no need to spend time and money to contact utility companies to de-energize lines and to then follow all grounding processes to ensure they are de-energized. Therefore, using cover-up equipment can improve productivity. Generally, when workers feel safe working on live lines, they will be more productive.
- Two trained and qualified line workers equipped with appropriate PPE must be present for installing or removing the rated covers. A second qualified worker will be required as a safety watch for the worker installing the covers, even with the use of rated cover-ups. All line workers are responsible for checking whether the insulator is appropriate to the extent deployed.
- Insulating covers must be secured if they can move and expose the live parts.
- Cover-up equipment is intended for protection from accidental brush contact only. To prevent accidental contact with the cover and to ensure safety, site supervisors should require and encourage workers to use PPE and keep safe distance, even when working with proper cover-up equipment (OSHA 1910.269(l)(2)).
- The energized part should be covered first, then the nearest conductive parts that are not currently energized but can become energized (e.g., guy wires, cross arms, poles, etc.). The removal process must be done in reverse order.
Maintenance and testing:
- Inspection, maintenance, and testing are integral parts of cover-up applications. The industry has set the standards for in-service care and technical testing of cover-up equipment (ASTM D 1049-88, ASTM F478)
- Covers must be handled carefully to reduce breakage and scratching.
- Cover-up equipment must be inspected daily before each use to ensure there are no holes, tears, ozone cutting, or deep scratches, and to ensure that all standard specifications are met. There is no approved method for repairing cover-up equipment. If they are damaged, they must be replaced.
- It is critical that covers be kept clean, so rainy or humid weather that causes dirty surfaces can significantly reduce their effectiveness. Moreover, these covers must be wiped cleaned with a cloth or washed with soap and water.
- These covers are for temporary use, since they are designed from light materials that cannot stay under electrical stress for extended periods. Thus, they must not remain installed for long without frequent checking based on standard specifications. Covers must be removed by end of the work day, if possible.
To obtain information, visit http://www.cantega.com or contact 1-877-448-9701
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Hastings Hot Line Tools and Equipment
To obtain information, visit http://www.hfgp.com or contact 1-269-945-9541
http://www.cooperindustries.com or contact 1-800-386-1911
Preformed Line Products
To obtain information, visit http://preformed.com or contact 1-440-461-5200
Salisbury by Honeywell
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Hubbell Power Systems
To obtain information, visit http://www.hubbell.com or contact 1-475-882-4000