Protecting electrical workers from getting shocked
Putting workers in insulated rubber gloves is not the answer to shock protection. Sounds a bit strange I know, but the answer to shock protection is to turn the circuits off, not work them energized with a mechanical device that can fail. The sad reality is at times we have no choice. Even in the isolation process exposing workers to energized parts is inevitable. The chosen meter must first be verified on a known live circuit in the LockOut/TagOut process. Until the circuit parts are verified de-energized with a phase to phase and phase to ground check the circuit is still considered energized anyway. So what’s the answer to providing workers with necessary protection from electrical shock.
First and foremost your electrical safety program MUST include a “live work policy”. Even though this is counter to the idea of always de-energizing before work is performed it must still be included. What is the acceptable time, place, condition and procedure that should be followed must all be clearly spelled out in the policy. Anything less opens the door for your electrical workers to proceed into the danger zone and you really aren’t sure what they will do this time around. When anomalies arise in the equipment or process, workers will make some of the darndest decisions. Followed by the comments “I thought it was OK to push this wire out of my way” or “It’s always worked this way before” must surely be the subject of nightmares for those tasked with ensuring safe work. Once the decision is made to work ‘some conditions’ in an energized state, procedures are written about how and when it is to be done, workers trained to understand the plan and monitored to ensure compliance to it. The last thing is to chose the appropriate protection to be worn. Rubber insulating gloves and leather over protectors are still not consistently utilized nor widely accepted, especially in the area workers call “low voltage”. It must be enforced that OSHA rules and practical science accepts that any voltage above 50 vac can do physical harm to a worker up to and including death. So even at those common 120 vac control circuits where a worker acknowledges “I work 120 volt live at home, why not here at work” workers must be given the expectation to be protected and prepared.
Worker comfort and manual manipulation of parts is a major issue when gaining acceptance of an insulated glove policy. We should attack that opposition quickly and clearly. Get over it! Yes, working in gloves is a challenge, which is why the electrical safety policy MUST limit when exposures to energized parts will occur and the need for the gloves decreased in the process. But the need for insulated gloves with leather protectors will never be completely eliminated from the workplace. Skills proficiency with their use must be demonstrated in the qualification process. Ensure workers can demonstrate proficiency and confidence doing tasks such as checking for absence of voltage in the isolation process on de-energized equipment BEFORE they are allowed to do the same on circuits and equipment not yet proven to be in an electrically safe condition.
Glove selection is as crucial a decision as is proficiency in their use. Class 00 gloves, the thinnest, lightest and most flexible, are good to a system nominal voltage of 500 volts. In the US those are our 480 volt systems. The note under OSHA rule 1910.137 Table I-4 (multi-phase or phase to ground) means the maximum voltage is either phase to phase (480 volts nominal in US systems) or phase to ground (277 volts in US on the 480 volt systems) where there is no second phase (just one hot and a neutral conductor present) or the other phase that is present is insulated/isolated so as no contact can be made between the phases. This can be dangerously misunderstood and be more of an excuse than an exception because when two or more phases are present workers will inevitably find a way to make inadvertent contact. Also some of those 480 volt systems can float up to 505 or 510 volts depending on the transformer taps and system characteristics and loading. Even thought the system is said to be a 480 volt nominal system, the 'rule' says this is not OK since the nominal voltage at certain times and conditions is no longer 480 of the system and in practice it can be very dangerous. Some safety equipment is tested for 25% over their rating and can be used at slightly above their rated value with confidence. This is NOT the case with electrical PPE. The stated rating is the MAXIMUM and not OK to use at "just a little over" the value. Class 00 gloves are not as durable (thick) as Class 0 gloves yet the leather over glove is the same on both Classes. So the dexterity argument from the workers when the leather gloves are worn over the rubber gloves is a moot point. Class 00 can be used without leather protectors for voltages up to 250 volts nominal but CANNOT be used again at their rated voltage until they are sent out to be electrically tested. That includes the 277 volt, single phase lighting circuits of a 480/277 Y system. All other classes are downgraded one class for use without leather over gloves with the same reuse testing requirement. One past client allowed their instrumentation guys to use Class 00 without leather protectors due to needing high finger dexterity and when they were sent out at the 6 month required testing interval over 50% failed! This cycle was repeated over a two year period. That tells me two things. First the workers were NOT doing adequate daily inspection and testing resulting in using gloves that were damaged and secondly, the employer needed to consider where high dexterity is needed and this type of damage is being done to the only protection available then work procedures and even equipment design changes should be considered to provide the needed worker protection. In my consulting I recommend no Class 00 gloves. Too many variables that require additional employer oversight in today's electrical environment. Are 480 volt VFD controllers in use where the DC voltage in the controller can be at or over the DC maximum value? Are there 480 volt ungrounded systems where the voltages can reach 900 volts or more in a ground fault situation? I would recommend if you restrict the Class 00 use to systems of 250 volts or less (120/208 or 120/240 systems) then that would be the only place they are appropriate. Any higher voltages encountered put them in Class 0, train them to do daily checks and know system variables and audit them to be sure they are being compliant with your electrical safety program. And if workers are more into construction than maintenance, make sure those nice soft leather over gloves protecting the rubber gloves are not being used for everyday use. Nice gloves but restricted use. Been there. Done that! Class 0 gloves with the appropriate leather over protectors is generally the best choice for workers performing tasks on systems less than 1000 volts. The same warning previously discussed with Class 00 needs to be understood here as well. Newer technologies and systems are being developed that is pushing the 600 volt US based systems to 1000 volts and above. When working in what could be called the ‘marginal zone’ it is always best to consider the next higher rated protection when de-energizing is not possible.
In the scheme of protecting workers, PPE is a critical but last step in the overall process. Consider adding new technologies and equipment available from companies such as Grace Engineered Products and others that separate the workers from the highest voltage exposure while doing important diagnostic and data collection tasks. Re-engineering or upgrading a piece of equipment is always a better path than rehabilitating an injured worker. Develop clearly written procedures workers must follow when “live work” is a necessity, and audit their compliance to those procedures. Too often workers think when wearing PPE they are invincible to any injury. Unfortunately all too often that premise is proven wrong.