Protecting workers and company assets from ignitions caused by static electricity can’t be left to chance. In facilities where flammable and combustible products are processed, there’s a very high probability that static electricity is generated by the movement of gases, liquids and solids. The risks of a fire or explosion caused by a discharge of static electricity in an EX/HAZLOC area are just too significant to ignore. To emphasise its significance static electricity is identified in North American and European legislation as a potential source of ignition in potentially flammable and combustible atmospheres.
Although static electricity is regarded as “witchcraft” by many people working in the hazardous process industries, static grounding and bonding protection methods are anything but complex. Industry guidelines like NFPA 77* and IEC 60079-32-1** identify specific processes susceptible to discharges of static electricity coupled with practices that can eliminate the threat of ignition.
The most effective and practical means of eliminating the threat of a fire or explosion caused by static electricity is to ensure static charges are not permitted to accumulate on equipment, vehicles and people. Grounding and bonding presents the most effective and reliable way of removing static electricity from an EX/HAZLOC atmosphere.
*NFPA 77: Recommended Practice on Static Electricity” (2014).
** IEC 60079-32, Part 1: “Explosive atmospheres – Part 32-1: Electrostatic hazards – Guidance” (2013).
NOTE: Cenelec CLC/TR 50404 “Electrostatics. Code of practice for the avoidance of hazards due to static electricity” (2003) has been superseded by CLC/TR: 60079-32-1″Explosive atmospheres – Part 32-1: Electrostatic hazards – Guidance” (2015).
Industry approved guidance on controlling static ignition hazards.
To ensure we are protected from ignitions caused by static electricity we need to follow some basic rules of engagement provided in publications like NFPA 77 and IEC 60079-32-1. The most important benchmark is to ensure we can achieve an electrical resistance of 10 ohms or less between electrically conductive plant equipment, including mobile plant, people and vehicles, and a “ground source” that is verified as a true earth grounding point. This point will have a low resistance connection to the general mass of the earth and will transmit electrostatic charge from equipment to the earth, regardless of how much static electricity is generated by the process. This, in turn, removes the static ignition risk from the processing location.
In order to achieve a safe level of protection from electrostatic ignitions we must provide an effective means of grounding the equipment. Historically, the grounding of portable objects like drums, vessels, and vehicles like trucks and railcars was achieved with basic clamps that were assumed to make a direct connection to the equipment.
Figure 1; Traditional plier type basic clamp
However, issues like product build-up and protective coatings that can impede the integrity of grounding clamp connections, combined with rusted and degraded cable connections, prompted the industry to develop ground status indicator systems, particularly for the larger hazards which are typically reflected in railcar, truck and IBC bulk handling operations. Ground status indicators (commonly referred to as static grounding systems) monitor the connection to the equipment at risk of charge accumulation and provide a visual reference to workers to indicate if they have a secure ground connection, which, if green, will indicate that they can proceed with the process. In addition to providing a monitored grounding circuit many of these systems contain output contacts that can be interlocked with the process. Normally the grounding system’s output contact will be interlocked with the equipment controlling the flow or processing of the product, thus ensuring the equipment is grounded before the process that generates static electricity can begin.
Figure 2: Traditional wall mounted ground status indicator system with internal output contacts. Note the green for ‘SAFE TO GO’ indication method.
Sourcing and specifying grounding solutions with the flexibility to meet your specific zoning, installation and operating requirements.
For somebody tasked with controlling static ignitions hazards, solutions tend to fall between basic clamps and cables and static grounding systems. Static grounding systems offer the most layers of control and protection over static ignitions risks, particularly as they can monitor the integrity of the connection to the process equipment, provide a visual indication to operators of a positive ground connection and shut down the process if the grounding connection is ever compromised.
Although the majority of solution specifiers would like to have multiple layers of protection over electrostatic ignition risks it can be difficult to source the budget for processes where many items require static grounding protection. In addition, the processes responsible for generating static electricity may be operated manually with no means of automating safe controls over the process. One example of this is facilities that carry out manual filling operations of large quantities of drums and smaller containers with flammable liquids.
Bond-Rites provide 2/3 the level of protection of static grounding system at half the cost.
The Bond-Rite® family of products enable product specifiers apply additional controls over electrostatic ignition hazards above and beyond basic clamps and cables, without the burden of justifying purchases associated with grounding systems with interlock capability. For 15 years Bond-Rites have enabled solution specifiers to move up the safety curve from basic clamps and cables to achieve enhanced levels of safety by providing workers with a visual means of verifying a solid electrical connection to equipment for the duration of the process.
Employing the well-recognised safety principles of GREEN for “SAFE TO GO”, Bond-Rites utilise a pulsing green LED to indicate when the equipment (e.g. drum) has a resistance of 10 ohms or less to the site’s verified ground network. All Bond-Rites continuously monitor the connection to the equipment until the clamp is removed. The green for “SAFE TO GO” concept is extremely easy for workers to engage with enabling them to take responsibility for their own safety and that of their colleagues.