When it comes to transferring flammable or combustible liquids, the threat of a spark isn’t just theoretical; it’s real, and it’s dangerous. One of the most overlooked risks in these environments is static electricity. A seemingly invisible hazard, static buildup can lead to fires, explosions, and catastrophic damage, particularly in high-volume loading and unloading operations.
That’s where static grounding – also known as earthing – comes in. Ensuring that trucks, tanks, hoses, and terminal systems are properly bonded and grounded is a critical safeguard in preventing electrostatic discharge (ESD). But understanding why, when, and how to implement static grounding effectively requires a closer look at the standards, scenarios, and systems involved.
This guide breaks down everything about static grounding for hazardous liquid transfer—starting with the basics and working through practical implementation and outcomes.
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- What is Static Grounding?
- What Rules and Regulations Are Associated with Static Grounding?
- Why is Implementing Static Grounding Important?
- When is Static Grounding Necessary?
- Where is Static Grounding Used?
- How is Static Grounding Implemented?
- What are the Outcomes of Static Grounding?
Static grounding isn’t just a regulatory checkbox, it’s a frontline defense in hazardous environments. From understanding the physics of static buildup to selecting the right verification systems, each component plays a role in protecting operations, people, and the environment.
Whether you’re responsible for safety compliance, managing terminal operations, or simply want a deeper understanding of best practices, this guide will help navigate the critical considerations of static grounding. Because in this business, the difference between safe and unsafe often comes down to what can’t be seen and what’s been done to control it.
Let’s dive in.
In the US, over 75,000 tank trucks move oil, gas, solvents, and other liquids from one destination to another, according to TIPNet and TIP new registrations reports. That’s not including the thousands of railcars, vessels, and barges that move similar liquids as well.
To secure the transit, product must be loaded at the origin and unloaded at the destination. While this process may seem straightforward, static electricity may be one of the most overlooked hazards when it comes to loading and unloading tank trucks.
Static electricity occurs when an imbalance of electric charges develops on the surface of an object. This charge accumulation happens due to friction, separation, or contact between materials. If not properly dissipated, the static charge can discharge suddenly, creating sparks that may ignite flammable substances and lead to catastrophic incidents.
Static electricity in tank trucks builds up primarily due to friction of flow of materials, particularly during loading and unloading. This is magnified when loading at 600 gallons per minute and splashing from the pipes into a tank or compartment generates bubbles and product vapor which are fuel for a potential spark. When liquids or dry bulk materials flow through pipes or tanks, they can interact with the walls and create a separation of charges, resulting in a static charge. This charge can accumulate on the truck’s surface, especially if the truck is not properly grounded.
Static grounding, also known as electrostatic grounding, is the process of safely dissipating static electricity to prevent hazardous electrostatic discharge (ESD). It is a critical safety measure in industries where flammable materials, combustible dust, or sensitive electronic equipment are present.
Scully’s lineup of static ground proving products are trusted globally by terminals and trucks.
What Rules and Regulations Are Associated with Static Grounding?
Various industry regulations and standards ensure proper static grounding measures are in place. Some of the key standards include:
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- NFPA 77 – Recommended practices for static electricity control.
- OSHA 29 CFR 1910.307 – Regulations for hazardous locations and static electricity control.
- ANSI/ESD S20.20 – Standards for controlling electrostatic discharge in electronic manufacturing environments.
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The National Fire Protection Association (NFPA) recently conducted research on incidents related to static electricity, and as a result of their findings updated their guide, NFPA 77 Recommended Practice on Static Electricity in 2023.
By following best industry practices and adhering to regulations, businesses can significantly reduce ESD hazards and improve operational safety.
Why is Implementing Static Grounding Important?
Industries such as oil and gas, chemicals, pharmaceuticals, paints and coating, and food and beverage face significant safety risks, as the product they are transporting can generate a hazardous condition when loading and unloading.
Tank trucks that are loading flammable liquids can gather enough static electricity to emit hundreds – sometimes even thousands – of millijoules (mJ). Considering it only takes around 25 mJ to create a spark between two surfaces, this level of energy, if not discharged properly, can be an ignition source. To prevent dangerous explosions and fires from erupting, it is required that all elements involved in the loading process are bonded or grounded to the same potential. This includes the tank truck, product nozzles, loading arms, hoses, tanks, and terminal equipment. Not addressing grounding can be fatal and holds significant business liability.
When is Static Grounding Necessary?
Static grounding is necessary in various situations to prevent hazardous electrostatic discharge. Some key scenarios include:
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- Handling Flammable Liquids and Gases – When transferring or storing flammable substances, grounding is essential – often required – to prevent static sparks that could ignite fires or explosions.
- Working in Explosive Atmospheres –Chemical plants, refineries, loading liquid terminals, and gas stations are environments with high potential for explosive fuels and vapors, therefore require static grounding to eliminate ignition sources.
- Operating Industrial Machinery – Large rotating equipment can generate static electricity through friction, requiring proper grounding to avoid ignition sources.
- Handling Bulk Solids and Powders – Pneumatic conveying systems and dust collection processes can accumulate static charges that need to be dissipated.
- Fueling Operations – Grounding is essential during fueling of aircraft, vehicles, and storage tanks to prevent static-induced fires.
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Since an operator cannot see a static charge buildup, having a static grounding verification system is crucial. These systems alert the operator when a proper bond is established between system elements, indicating that it is safe to operate. Even when a grounding cable is visibly connected between two points, there is no guarantee of a reliable electrical bond capable of equalizing the potential between surfaces. This may be due to issues like corrosion, which are not always visible. Static grounding verification systems eliminate this uncertainty, helping to ensure a safe operating environment.
Another element to consider when assessing a verification system is choosing one that is difficult to cheat or bypass without authorization. In some cases, operators may find short cuts to “simplify their task” not knowing the potential danger to them and their surroundings. It’s crucial to identify this feature when assessing available systems.
Where is Static Grounding Used?
Static grounding is used across various industries and applications to mitigate the risks associated with electrostatic discharge. In fixed installations, permanent grounding cabling is implemented, reducing the risk of bad grounding. Whereas in mobile installations – where the tank is transported to a different location – the grounding connection is an additional step in the process, therefore needs to be verified to avoid major risks to the operator and their surroundings. Typical mobile vessels are integrated into trucks, trailers, rail cars, barges, airplanes, drums, and intermediate bulk containers (IBCs).
Key areas where static grounding is commonly applied include:
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- Oil and Gas Industry – Used in fuel storage facilities, pipelines, and refineries to prevent sparks that could ignite flammable vapors.
- Chemical and Pharmaceutical Plants – Ensures safe handling of volatile chemicals and powders that can generate static charges during production and shipment.
- Automotive and Aerospace Fueling – Essential in aircraft refueling and vehicle fueling stations to prevent static-induced fires.
- Agriculture and Grain Handling – Used in silos, grain elevators, and dust collection systems to prevent ignition of combustible dust.
- Paint and Coating – Applied in processes involving the transfer of paint and coating liquids into drums for transportation.
- Industrial Machinery and Processing Equipment – Prevents charge accumulation in rotating equipment and conveyor systems supporting operations.
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How is Static Grounding Implemented?
The most effective way to ensure there is no buildup of static charge is to establish a solid bond—meaning proper contact—between the truck and terminal loading equipment. This equalizes the electrical potential across all surfaces, ensuring effective static grounding. The terminal loading rack itself is grounded to earth potential, which is typically considered zero volts, and serves as the universal reference point for electrical and grounding systems.
The benefit of a static grounding verification system is that the operator has an indication that there is a proper grounding connection between the truck and the loading terminal. In some applications this is part of the loading permit automation—without good ground the product does not get a permit to load.
Proper grounding techniques ensure fueling operations are safe and comply with industry regulations.
Static grounding verification systems use different methods to assess a “good” or “bad” ground.
One method is to measure the resistance between two surfaces. If the resistance value is below a defined threshold, the device will identify the result as ”good bond,” typically with a visible LED indicator or an audible notification.
Another method, which is more difficult to “cheat”, is to use a diode circuit that detects the voltage drop and implies a “good bond”.
What are the Outcomes of Static Grounding?
When implemented properly, static grounding systems are highly effective in preventing hazardous static electricity build-up, significantly reducing the risk of ignition incidents when transferring flammable liquids.
The positive outcomes of implementing a comprehensive static grounding system include:
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- Safer Work Environment – Static grounding verification protects workers and the environment from unnecessary accidents. Grounding systems proactively address the potential for static electricity buildup, which is a major ignition source in hazardous environments like fuel tank truck unloading operations.
- Regulatory Compliance – Many industries that handle flammable liquids have strict regulations requiring the use of static grounding systems on tank trucks.
- Improved Operational Efficiency – Grounding verification reduces the risk and potential for downtime and equipment failures caused by static-related incidents.
- Enhanced Monitoring Capabilities – Modern grounding systems often include monitoring features to verify a proper connection. Some require measurement of good ground to permit the loading operation, further enhancing safety.
- Intuitive, User-friendly Design – Grounding verification systems are designed to be simple and intuitive, so the user can easily identify when a good bond has been established, facilitating quick and accurate connection to tank trucks.
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It is important to consider the following when implementing a static grounding system:
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- Improper Installation or Usage – Failure to correctly connect the grounding cable or using a faulty system can negate its effectiveness. In some cases, a connection itself does not guarantee a “good bond” due to unseen equipment degradation.
- Environmental Conditions – Extreme weather conditions like heavy rain or snow may impact the grounding connection.
- Maintenance – Regular inspection and maintenance are crucial to ensure the grounding system remains functional.
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Static grounding is a fundamental safety practice that protects personnel, equipment, and facilities from the dangers of electrostatic discharge. Implementing proper grounding techniques minimizes the risk of fires and explosions, ensuring a safe and efficient working environment.
Check out Scully’s static ground proving systems and accessories, or our ground proving plugs, cables, and clamps.