Framework for Static Electricity Risk Reduction

What is Static Electricity

Physical objects are made of Protons, Electrons and Neutrons. Protons are positively charged; electrons are negatively charged, and neutrons do not have any charge (they are neutral). Typically, the positive and negative charges are balanced, and therefore, the object is neutral.

Static electricity caused by the imbalance between positive and negative charges in an object or specifically an excess (or deficit) of electrons. The charge builds up until the electrons find a way to discharge. Materials that lose or gain electrons are referenced as Triboelectric materials.

Most common examples are experiencing a “zap” when touching a doorknob particularly in the winter months when the humidity is low. This is because during winter, the air is dry, and dry air is not a good conductor of electricity; however, during summer the moisture content in air is higher and this provides a natural path for electrons to dissipate.

In industry, static electricity can cause a lot of damage such as loss of life, serious bodily injury and destruction of infrastructure, and its propensity for causing damage is often overlooked.

This article discusses the likely causes of static electricity and ways to mitigate the same.

Conditions for an Accident due to Static Electricity

In order for a fire or an explosion to occur due to static electricity, the following are necessary:

1. Charge Buildup: This is typically caused due to interactions between triboelectric materials. Some examples are filling up products in containers or bags, liquids flowing in a pipe etc. In this process, one material loses electrons and the other gains the same resulting in charge buildup.
2. Environmental Conditions: Low humidity promotes static charge build up as dry air is a better insulator. When humidity increases the moisture content in the air also increases; moisture being a good conductor, helps dissipate the charge that builds up.
3. Combustible/ Explosive Material: Materials such as hydrocarbon vapors, grain, or wood dust, flammable flyings or fibers typically found in an industrial or manufacturing facility.
4. Air (Oxygen): Oxygen in air is essential for sustaining the fire or explosion.
5. Discharge Path: In the absence of a controlled path such as a bonding conductor, the accumulated charge could discharge in an uncontrolled manner such as being attracted to a positively charged surface.
6. Minimum Ignition Energy (MIE). The energy, usually expressed in millijoules, stored in a capacitor that, upon discharge, is just sufficient to effect ignition of the most ignitable mixture of a given fuel mixture under specified test conditions. [NFPA 77-2019-3.3.24.1]

Given the number of variables, it is possible that an accident may not occur for several years, and due to this the risk is often overlooked.

A search on OSHA’s Fatality and Catastrophe Investigation Summaries webpage using Key word “static” identified a total of 103 accidents between May 1985 and November 2018. Several of these incidents caused fatalities. There are several such incidents documented by other government agencies such as the Chemical Safety Board.

Based on a study Static Electricity Incident Review, August 2021 conducted by Fire Protection Research Association (An affiliate of NFPA) following were identified as the reason for an accident:

1. Limited understanding of NFPA 77
2. Negligence
3. Accident
4. Poor Maintenance
5. Inappropriate handling of materials (solids, liquids, and gases)
6. Inappropriate storage method for storing flammable liquids.
7. Inappropriate method of transportation
8. Inappropriate method of disposing waste liquids
9. Cost cutting/ reducing expenses

Risk Mitigation Methods

The risk posed by static electricity can be mitigated by ensuring the following:

1. Reduce/Limit/Prevent charge buildup.
2. Provide a safe path for to dissipate electrical charge.
3. Controlling ignition hazards:
   1. Proper storage and handling of flammable materials
   2. Adequate ventilation to avoid buildup of flammable vapors
   3. Regular cleaning to clear dust and debris
4. Good work practices.

Best Practices

Some of the best practices recommended by Fauske and Associates to mitigate accidents caused by Static Electricity are as noted below:

1. Proper implementation of NFPA 77 and other applicable standards and regulations.
2. Appropriate grounding and bonding.
3. Ensure electrical continuity to ground of non-current carrying parts.
4. Use of FBIC of appropriate type where applicable.
5. Improve air circulation.
6. Use ionized compressed air where applicable.
7. Provide anti-static treatment for floors and other surfaces as applicable.
8. Use electrostatically safe tools.
9. Use anti-static floor mats in work areas.
10. Use anti-static tubing.
11. Include anti-static wrist and heel straps.
12. Use static detection equipment and identify “Static hot spots”.
13. Install electrical ionizers.
14. Pay special attention to non-metallic enclosures, equipment, piping, tubing etc.

Conclusion

Static Electricity can cause significant damage and with appropriate mitigation plans, its risk can be minimized.

Fauske and Associates has the expertise, experience, and capabilities necessary to perform studies to mitigate the risks caused by static electricity. Please contact info@fauske.com

Reference Documents

NATIONAL FIRE PROTECTION ASSOCIATION (NFPA)

NFPA 77                         Recommended Practice on Static Electricity

NFPA 70                         National Electric Code

FIRE PROTECTION RESEARCH FOUNDATION (An affiliate of NFPA)

Static Electricity Incident Review, August 2021

INTERNATIONAL ELECTROTECHNICAL COMMISSION (IEC)

IEC 60079-32-1           Explosive atmospheres – Part 32-1: Electrostatic hazards, guidance