Shock ProtectionBy Lee Marchessault - Published on November 7, 2016 12:49 am
Shock protection is an integral component of electrical safety. During the job briefing hazard assessment, the nominal voltage is identified. This will provide information needed to determine appropriate shock prevention measures.
First, try to completely de-energize the enclosure before opening doors or removing covers. If this is not feasible, then some level of PPE will be required before removing covers depending on the voltage. Most common voltages in the US are 120/240 volts single phase and 120/208 and 277/480 volts 3 phase, and in Canada 575 volts is the most common 3-phase power system. It’s important to know that ANY VOLTAGE CAN KILL. There have been fatalities on 48-volt controls. To protect against shock hazards, some basic equipment should be available and used. Remember that the goal is to increase the resistance in the body where a contact could cause electricity to flow. Air is a great insulator, so distance and non-conductive barriers are best to avoid contact and in some cases eliminate the need for electrical PPE.
If PPE is required, head-to-toe protective equipment includes electrical related hardhat Class E or G, rubber insulated gloves and EH-rated boots. For 480 and 575 volt work, the minimum approach distance is 12 inches from non-insulated body parts so rubber gloves must be worn before opening a door or removing a cover to exposed parts. This is required even if de-energized because it must be tested to be sure it is de-energized.
Class 0, 14” rubber gloves with leather protectors are the best option because class 00 are rated for 500 volts and often 480 volt systems exceed this level. The length is important because 12” rubber gloves have a rolled cuff so the lower arm will be within the minimum approach boundary when testing using a meter Rubber gloves are required to be air tested before each days use and lab tested at least every 6 months. To make the testing easier, assign one person to all rubber glove testing. Ask your lab to stock second pairs of gloves, then test and ship them every 5 months so that employees only need to change them when received and ship them back. It may also help to have 2 sets of different color gloves. For example, the yellow are used in summer and the red are used in winter. This will help to ensure that the test is completed within the defined time frame.
Thin cotton liners will soak up sweat and are more sanitary if gloves are shared. (i.e. Test or assembly areas with shift workers). Leather protectors should be used with rubber gloves (Shall be for Classes 1-4). Medium voltage requires higher rated gloves in addition to the use of hot sticks and grounding equipment. Other tools that every electrical worker should have include insulated hand tools and fuse pullers, portable GFCI cord, or pigtail for cord and plug tools, rubber barrier material, and UL listed CAT III and/or CAT IV test meter. Observing these recommendations will keep employees safe from shock hazards.Tags: Electrical Safety, personal protective equipment, PPE, Shock Protection, Voltage