Engineering Methods of Hazard Reduction & Mitigation

Many safety leaders have stated that they do not allow qualified employees to work on or near exposed live (energized) circuits.  They have created a policy that all energized circuit shall be de-energized and locked and tagged (LOTO) per specific control of hazardous energy policies.  This is a great policy, but it is not always feasible.

There are some systems that cannot be easily de-energized.  OSHA's requirement for working on energized equipment is “Live parts to which an employee may be exposed shall be deenergized before the employee works on or near them, unless the employer can demonstrate that deenergizing introduces additional or increased hazards or is infeasible due to equipment design or operational limitations” [OSHA 29 CFR 1910.333(a)(1)]. 

Electrical systems that are identified as emergency systems (NFPA 70, Chapter 700), legally required systems (NFPA 70, Chapter 701), and critical operating power systems (NFPA 70, Chapter 708) cannot be de-energized unless permission is obtained from the appropriate governmental authority have jurisdiction (AHJ).  Emergency power systems are critical for life safety and include many healthcare facilities.  Emergency power systems are also located in every public building and include emergency lighting for egress and fire suppression, alarm, and communication circuits.  Legally required power systems include those systems that if de-energized, can create a greater hazard to the community.  Legally required power systems include those systems that control pollution abatement systems, chemical containment systems, and the like.  Critical operating power systems include those systems that critical to functionality of the US.  This includes water, transportation, energy, transportation, and specific monetary functions.

Another type of power system is the optional power systems (NFPA 70, Chapter 702).  Optional (nonessential) power systems are those systems and loads that are related to business continuity.  These power systems can be de-energized without creating safety hazards, although they may impact the business.  

In addition to systems that cannot be de-energized easily because of legal requirements, specific activities such as troubleshooting, testing and measuring of voltage, current, power or related parameters must be conducted when electrical equipment is energized on all types of power systems [NFPA 70E-2015, Chapter 130].  There are other activities that may also require qualified personnel to interact with exposed live (energized) circuits.  This includes the adjustment and programming of equipment.  These activities can be conducted on all types of electrical systems and in locations such as manufacturing environments, R&D laboratories, production testing environments, and many more.

Last month’s blog focused on the Administrative Methods of hazard reduction and mitigation of electrical hazards.  While administrative methods can be effective, they also present an opportunity for injuries to occur.  Hazard reduction and mitigation techniques are more reliable and effective when Engineering Methods are implemented.

The Engineering Methods of hazard reduction and mitigation of electrical hazards include:

• ·         Elimination
• ·         Substitution
• ·         Guarding
• ·         Safety Control Systems

Guarding of electrical hazards are what is accomplished by equipment enclosures.  Enclosures protect all people who are in close proximity to the equipment from interacting with the equipment.  However, when qualified employees need to conduct troubleshooting or testing, they need to have access to the exposed live (energized) circuits.

Safety control systems are typically devoted to keep employees out of a hazardous area and can be very loosely similar to guarding principles.  Common equipment associated with safety control systems include using light-curtains, pressure mats, interlocks, or other components tied into a safety rated programmable logic controller (PLC).

The substitution principle can be used by changing the operating voltage that the qualified employee is required to interact with.  This includes changing control voltages from 120V or 240V to 24V.  The 24V control circuit can be located in a separate cabinet that is isolated from any circuit that is 50V or greater.  Qualified employees working on system voltages of 24V are generally not exposed to shock or arc flash hazards.

To eliminate electrical hazards, designers and engineers can remove the need for people to interact with exposed live (energized) circuits.  This includes designing equipment such that user interface equipment is located on the front panel of the equipment.  Examples include using HMI’s, remote panels for SCRs or other industrial control components, remote communication interface ports, etc.  Eliminating qualified personnel from interacting with exposed live (energized) circuits can be achieved on new equipment that is in the design phase, but is not very practical for equipment that is already installed.

As the term Engineering Methods suggests, engineering activities are required to assess the risks of the activities, and to reduce or mitigate the hazards.  For qualified employees working on exposed live (energized) circuits, the implementation of engineering methods to reduce or mitigate arc flash hazards will result in a safer workplace.

Administrative Methods to Mitigating Electrical Hazards

The rules surrounding electrical safety continue to change.  There are three main components that are affecting change: scientific data, safety professionals, technology.  Researchers continue to develop and communicate new understanding of shock, arc flash, and other electrical hazards.  Safety professionals are working hard to set a safe working culture within the workplace.  Technology is being created to mitigate electrical hazards. 

There are multiple methods to reduce hazards.  Risk reduction techniques are commonly divided into engineering and administrative controls.  Reducing hazards through engineering methods (elimination, substitution, guarding, and safety controls) is preferred over administrative methods (operating procedures, training, and personal protective equipment).

However, most of the efforts to reduce employees to electrical hazards have been focused on administrative methods.  The use of administrative methods (operating procedures, training, PPE, signage) is not the same as eliminating the hazard, guarding the hazard, or using safety controls to eliminate access to the hazard.

Companies are implementing safe work practices, electrical safety training programs and procuring shock and arc flash personal protective equipment (PPE).  The Standard for Electrical Safety in the Workplace, NFPA 70E, provides guidance for standard operating procedure, training, and personal protective equipment (PPE) for qualified people working on or near exposed live (energized) circuits. 

Safe work practices associated with electrical safety include the control of hazardous energy (Lockout Tagout) procedures, procedures for working on exposed live (energized) circuits, and electrical hot work permits.  OSHA requires that each company is responsible for developing, implementing, auditing the safe work practices to ensure that their employees have safe work conditions.

Companies are ensuring that employees who are working on or near exposed live (energized) circuits complete electrical safety training programs.  The consensus is that comprehensive electrical safety training is to be conducted at least every 3 years, and annual competency of refresher training be conducted every year between the comprehensive electrical safety training.  Electrical safety training is required for everyone who works on or near exposed live (energized) circuits where the voltage is 50 V or greater, or if the energy available can expose employees to shock or arcing hazards.  The elements of an electrical safety training include definition of hazards, safe work practices, use of PPE, use of tools, and understanding arc flash labels.  Testing is required to ensure that employees understand the concepts taught.  Testing should include a written test and practical examination.

PPE is used to protect employees from shock and arcing hazards.  Shock hazard PPE include voltage rated gloves, blankets, and mats.  Arcing hazard PPE include hard hat, leather gloves, leather shoes, arc rated clothing, arc rated face shield or arc rated hood, and safety glasses.  The rating of the PPE is determined through the calculation of the voltage (shock) and incident energy (arcing) energies.  Shock hazard PPE is identified by Class.  Arcing hazard PPE is identified by Category or Incident Energy Rating.  Employees working on or near exposed live (energized) circuits are required to wear BOTH shock and arcing hazard PPE.

Companies have used administrative methods as these are well known and can be easily identified in the company budget.  When implementing any component of the administrative methods to reduce shock and arcing hazards, it is important to have experienced and knowledgeable professionals involved.  The writers of the safe work practices can only produce effective procedures is done by competent technical writers with knowledge of the process and how to write effectively.  Training employees can only be effective when the trainer is a trained professional experienced in the craft of teaching and electrical safety.  The PPE used must be certified, regularly tested, and verified it is serviceable prior to each use.

The use of operating procedures, training, and PPE can reduce accidents associated with electrical hazards.  However, administrative methods are not as effective at reducing accidents as engineering mitigation techniques.

NFPA Electrical Safety Standards Update

It is amazing how quickly time passes.  I had intended to put together a series of electrical safety topics that focused on the basics of electrical safety and then some mitigation techniques, but time got the best of me7.  So, before we get too far, I want to step back and briefly discuss the trilogy of electrical safety standards with updated information.

As you know from reading past blogs, there are three standards from the standards from the National Fire Protection Association (NFPA) that contribute to an organization’s electrical safety program: National Electric Code (NFPA 70), Recommended Practice for Electrical Equipment Maintenance (NFPA 70B), and The Standard for Electrical Safety in the Workplace (NFPA 70E).  Equipment that is not properly installed or properly maintained can create safety hazards.

The foundational standard of electrical safety is equipment design and installation.  The 2017 version of the National Electric Code (NEC) provides the minimum design and installation requirements for electrical equipment.  The 2017 version is available as a PDF download; hard copies will be available in October.  The NEC describes how to apply equipment, conductors, grounding, overcurrent protective devices, and other devices.  When equipment and components are designed and installed in accordance with the NEC, there are minimal potential for shock and arc flash hazards. 

Article 110.16 of the NEC requires that all equipment, other than those installed in swellings, that are likely to require examination, adjustment, servicing, or maintenance while energized to be marked to warn qualified persons of the potential arc flash hazards.  This includes switchboards, panelboards, motor control centers (MCCs) and industrial control panels.  This can also include transformers, UPSs, transfer switch equipment, and junction boxes where power distribution blocks are used to splice conductors.  Arc flash labels should meet American National Standards Institute (ANSI) standard Product Safety Signs and Labels, ANSI Z535.4-2011.

The second standard of electrical safety is maintenance.  The latest edition of the Recommended Practice for Electrical Equipment Maintenance (NFPA 70B), which was published in 2016, and provides details on the development of an electrical preventative maintenance program (EPM) and basic maintenance requirements for common electrical equipment.  NFPA 70B can be used when specific maintenance procedures from the equipment manufacturer are not available.

The third and final standard of electrical safety is The Standard for Electrical Safety in the Workplace(NFPA70E), which was last published in 2015.  NFPA 70E provides the basic requirements for working on or near energized equipment when the guards (enclosure doors or panels) are removed and electrical energy is present.  Shock and arcing hazards are present whenever qualified employees are working on or near equipment when enclosure doors or panels are removed, and electrical energy is present.  If the equipment is properly installed and properly maintained, then any work or troubleshooting that could be required while the equipment is energized should follow the guidelines of NFPA 70E. 

Standards are developed to provide people and organizations with basic knowledge and guidance.  Ensuring that equipment is properly designed and installed (NFPA 70), properly maintained (NFPA 70B) and people working on or near exposed live (energized) circuits are trained, have procedures, and protective equipment (NFPA 70E) will limit personnel to shock and arc flash hazards.