Using insulating line hose is a work practice that provides a protective barrier to prevent unintentional contact with high-voltage lines. Although these insulators cover the live parts, workers must also use proper personal protective equipment (PPE).

Insulating line hoses are portable and available in various configurations, styles and voltage ratings for using in live-line operations. The flexible hose’s overlapping sides and lengthwise slit make it easy for a qualified line worker to place it on the conductor. There are four types of insulating line hoses: Straight Conventional, Extended Lip Straight Conventional, Connector End, and Extended Lip Connector End. All types are constructed, tested and maintained according to ASTM standards and OSHA regulations. ASTM D1050-05 (2011) governs manufacturing and technical requirements, and the F478-09 standard covers in-service care. Insulating line hoses also must be in accordance with the ANSI J6.1 1950 (R1971) standard. According to OSHA standards, insulating line hoses must conform to the voltage amounts shown in Table 1 for each class of equipment.

Table 1. Voltage requirements for insulating line hose (adapted from www.osha.gov)

(Photo courtesy of OSHA)

1- Straight Conventional

Straight conventional line hoses consist of a hollow tube with ribs on the inside for maximum protection. A straight conventional line hose is installed either by hand, utilizing proper PPE, or using various live-line tools. To install this type of hose, the worker must wrap the hose around the power line and secure it with various types of fasteners.

2- Extended Lip Straight

Extended lip straight line hoses are similar to the straight conventional, except they feature an added lip for easier installation and increased protection. The extended lip straight hose is very versatile and can be installed by hand or with hot sticks or other appropriate live-line tools. This type of line hose is the only flexible cover-up available for use on voltages through 34.5kV. 

3- Connector End Conventional

Connector end conventional line hoses have a body similar to that of the straight conventional line hose, but a flared-out end creates a compatible hose for use near a dead end on a line, when the gauge of wire changes, or when any other alteration occurs in the integrity and makeup of the wire. The connector end is used to attach two hose pieces together, but only one end of the hose can be used as a connector; the other end is identical to a straight conventional line hose. The process of installing a connector end conventional line hose is the same as the straight conventional line hose installation. While it can be installed by hand using PPE, installation using live-line tools along with PPE is recommended. 

4- Extended Lip Connector End

The extended lip connector end hose provides the same advantages as the extended lip conventional hose, but has the connector end feature of a straight conventional hose. In most cases, it is acceptable to install the extended lip connector end hose by hand, and using proper PPE. Notice that according to OSHA regulations two workers must be present for installing line hoses.

By using insulating line hose to cover live lines, the risk of accidental contact with live parts is eliminated. Moreover, there is no need to spend time and money to contact utility companies to de-energize lines and then follow all grounding processes to ensure de-energizing (it should be noted that de-energizing is the safest route for working around electrical equipment/lines). Therefore, using insulating line hoses can improve productivity. Generally, when workers feel safe working on live lines, they will be more productive.

Administrative guidelines:

• OSHA 1910.269(l)(2) states that since the insulating line hose does not eliminate exposure even if a rated line hose covers live parts, two qualified workers equipped with PPE must be present when work needs to be done within the minimum approach distance. Two trained and qualified line workers must be present when working on live lines to ensure quality and safety.
• All line workers are responsible for checking whether the insulator is appropriate to the purpose for which it is deployed.
• The energized part should be covered first, followed by 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.
• Insulating line hoses must be secured if they can move and expose the live parts. Moreover, if the line hose is to be installed vertically, it must be fastened so it will not slip.

Maintenance and testing:

• Inspection, maintenance, and testing are integral parts of line hose application. The industry has set the standards for in-service care and technical testing of line hoses (ASTM D1050, ASTM F479)
• Insulating line hoses must be stored in a relaxed position without any unnecessary stretching, folding or stress. They should not be placed on top of each other.
• Adhesive materials should be avoided in all installation processes because they can alter the effectiveness of line hoses.
• Line hoses must be inspected daily before each use to ensure there are no cracks, holes, tears, ozone cutting or deep scratches. Any mechanical damage greater than ¼ of the total length of hose indicates an immediate need to remove the hose from service. Hoses must be removed from service if they show any chemical deterioration.
• An approved cleaning material must be used to remove dirt and contamination on line hoses.

Sogand Hasanzadeh - University of Nebraska- Lincoln

Pouya Gholizadeh - University of Nebraska- Lincoln

Erik Bruening - University of Nebraska- Lincoln

Brett Farquhar - University of Nebraska- Lincoln

Behzad Esmaeili, Ph.D. - University of Nebraska- Lincoln