Passive or Active Grounding? That is the question
16 June 2023
For years now simple passive grounding has been used throughout industry as a low-cost safety measure and protection against fires and explosions caused by static electricity but is it as safe as you think?
In many branches of industry, hazardous atmospheres exist due to the presence of flammable liquid vapours, gases, dust and fibres. No matter how the explosive atmosphere is classified, all potential electrostatic ignition sources should be eliminated before a process commences.
Electrostatic charges can accumulate on tank trucks, vacuum trucks, interconnection plant assemblies, metal containers such as drums and hazardous area suitable Ex IBCs. Once the handling operations begin, these metal containers can quickly generate enough voltage for an electrostatic discharge to occur resulting in potential ignitions of Ex atmospheres.
Understand the major differences between passive and active grounding to improve safety in your application processes.
Passive grounding clamps and cables are only suitable if the metallic object to be grounded has a bright clean surface. This allows even a poorly designed passive grounding clamp to make a low resistance connection to the metal object.
However, not every industrial environment can use a bright clean metal surface, as mild steel usually needs painting to prevent rust and corrosion. This is clearly a physical barrier between the metal surface and the passive grounding clamp.
Paint is the number one enemy of successful and reliable passive grounding. The other main enemy is the product itself causing a barrier between the metal and the clamp with passive grounding, even bright clean stainless steel can be affected by product coatings.
So, what is the alternative to passive grounding clamps and cables? Well, it is active grounding clamps and cables. When you use passive grounding clamps how do you know that you have made a good low resistance connection to the metal object and the local site ground point? You do not, you just cross your fingers!
Active grounding clamps contain intrinsically safe circuits that monitor the resistance from between its teeth and the local site ground point to be 10 ohms or less. This 10 ohms or less metal-to-metal resistance level is enshrined in International guidance documents IEC TS 60079-32-1 and NFPA 77 and Recommended Practices API RP 2003.
This 10 ohms or less connection with an active grounding clamp is confirmed to the user by a high intensity flashing green LED. So, use of active grounding clamps and cables, takes the guess work out of safety, allowing you to uncross your fingers and most importantly be safe.
So, what are the differences between passive and active grounding clamps and cables?
- A metallic earthing clamp designed to provide a resistance of 10 ohms or less.
- If there is a ‘break’ in the connection or the resistance to earth rises above 10 ohms, there is no way of knowing during the operation.
- Unable to confirm a good earth connection before the process begins.
- Provides a resistance of 10 ohms or less as indicated via a high intensity flashing green LED within the system enclosure or on the Bond-Rite Clamp.
- The Green (GO) indication aids the SOP, e.g., do not proceed until the LED has gone green.
- Operators and plant personnel are accountable and secure about their working environment. Provides confidence that the process is reliably earthed before the operation commences.
- Performance is continuously monitored throughout the duration of the operation.
For over 40 years, Newson Gale has been leading the way in hazardous area static grounding control, serving many industries globally where processes generating static electricity have the potential to ignite flammable or combustible atmospheres. To help control these risks, Newson Gale offers a wide range of static grounding and bonding equipment designed to provide optimum safety in explosive atmospheres.
Create a safer working environment and download the full Grounding & Bounding Applications Handbook to learn more.
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