Nowadays, vacuum truck service providers and their clients can specify truck mounted earthing systems that will verify a connection to true earth; monitor the connection constantly, provide a visual indication of a verified ground to the driver and automatically shut down the operation if the ground connection is lost during the transfer. Due to the risk profile of this type of operation a solution like the Earth-Rite® MGV can provide the maximum layers of protection by ensuring:
- The earthing point the truck is connected to IS connected to the general mass of the earth.
- The driver has a visual indication of a good static ground connection so he can carry on with the job at hand.
- The ground path between the truck and the verified earthing point is continuously monitored to 10 ohms.
- A pair of output contacts can shut down the transfer operation if the ground connection is lost especially when the driver does not have a consistent view of the ground status indicators.
Fig. 5: A truck mounted static ground verification system with interlock control of the vacuuming operation reduces the electrostatic ignition risk profile of vacuum truck operations by a significant margin
To select the solution that provides the best-fit, source solutions that can combine the features outlined in the columns of Fig. 6. Starting at the most basic level, you should avoid using devices like welding clamps and alligator clips as these devices are not designed with static earthing in mind, especially for the kinds of processes that require the penetration of an insulating layer like a paint coating or rust. Static earthing clamps should be subjected to FM testing to ensure they are suitable to use in hazardous areas. Following on from this, the earthing solution specified should combine the features outlined in Fig. 6.
Fig. 6: Earthing solutions can be selected based the layers of protection you require from the risk of an electrostatic ignition.
Selecting Hazardous Area Certified equipment:
Try to source earthing equipment that has been approved to standards that reflect the latest state of the art in respect of hazardous area “equipment protection techniques” in accordance with IECEx and EN standards. It’s worth noting that all of the standards (the IEC 60079 family of standards for explosive atmospheres) that are utilised in terms of assessing equipment for ATEX are produced by the International Electrotechnical Commission on behalf of CENELEC. There are many ATEX certified devices, not just earthing devices, on the market today that have been approved to standards that have gone through several revisions, or are no longer in existence, since the devices were first approved. For example, the current standard for intrinsic safety, EN 60079-11 (2012), has been through two revisions since 2002, both of the superseding revisions being released in 2007 and in 2012 respectively. If earthing systems approved prior to 2007 were assessed by a Notified Body today, it is very probable that the device would need to be redesigned to match the requirements of EN 60079-11 today.
This guide will hopefully have provided you with enough information to get you started on the right path to buying static earthing solutions that best fits your company’s operations and their risk profile. The foundations of your buying specification should be built on:
- Sourcing static earthing equipment that can demonstrate compliance with the latest state of art in static control, namely, IEC 60079-32-1, CLC/TR: 60079-32-1, NFPA 77 and API RP 2003.
- Determining the layers of protection you think will control the risk of an electrostatic ignition – this will help you identify a earthing solution that will provide the “best-fit” for your operations and your operators.
A company that truly specialise in static earthing protection should be contacted to help guide you through this process. Newson Gale has offices in the U.S., Europe and South East Asia with teams that are on hand to help you navigate your way to the right static earthing solution. Contact one of our offices today to get you started on the right path.
Examples of how different operations can result in discharges of static electricity:
It’s worth noting that the common denominator in these incidents was that the operator(s) did not have a visual reference point for a verified ground connection.
Mike O’Brien, Managing Director for Newson Gale
If you have any questions relating to the topics discussed in this article,
please contact Newson Gale.