SAFETY IN THE PLANT
Road Tanker / Tank Truck Safety from Static Electricity
Carrying out a product transfer with an ungrounded road tanker/ tank truck is a static electricity hazard capable of causing extreme damage to plant and personnel.
The design and manufacture of a road tanker/tank truck must ensure that all metal items are bonded together. International Standards and Recommended Practices state that this bonding/ continuity must be <1 Ohm and others < 10 Ohms between metal items. Designated earth point/s must also be welded onto the vessel/body of the truck and be clearly marked and manufactured from corrosion resistance material.
mounted. A dedicated earthing system would:
• Provide the driver with a visual indication of a GOOD or BAD ground connection (GREEN flashing LEDs).
• Detect if the earthing system is attached to a road tanker/tank truck by its capacitance and at the same time check that the resistance of the verified true earth connection is capable of dissipating static electricity.
• Utilise an intrinsically safe (ia) monitored circuit that can automatically shut down the product transfer if the ground connection is lost.
• Provide an earthing method that fully complies with the relevant International Standards and Recommended Practices i.e. monitoring between the teeth of the clamp on the designated earth point of the truck back to the verified true earth point close to the gantry is less than 10 Ohms.
Drivers must be educated to attach the grounding clamp and system to the designated earth point on the truck as soon as they leave the cab and before they start any other operation or product transfer. It is critical that the clamp is connected to the designated earth pin on the vehicle prior to any other equipment, bonded or associated with the tanker, (e.g. transfer hose, landing legs) comes into contact with the ground.
The dedicated earthing system needs to confirm a good ground connection before the product transfer can begin. After the product transfer and all other activities have been completed the driver can then remove the earthing clamp and store it away on the earthing system stowage point before driving off.
To protect against the static electricity hazard some operators of road tankers/tank trucks fit a simple hand wind or retractable single core cable reel and clamp assembly to protect their trucks. Unfortunately, the single core cable reel and clamp assembly is a very unsatisfactory way of protecting the trucks because it cannot alert the driver to any of the following dangers:
• Cannot provide a visual indication of a GOOD or BAD ground connection.
• Does not provide true earth verification e.g. is the system connected to an earth that is capable of dissipating static electricity.
• Because it is not a monitored circuit it cannot automatically shut down the product transfer if the ground connection is lost.
• Does not comply with the relevant International Standards and Recommended Practices.
Therefore the recommended and safest way to protect a product transfer is to use a dedicated truck earthing system that is gantry
SEPTEMBER/OCTOBER 2020 www.reviewonline.uk.co
PD/CLC/TR 60079-32-1:2018 • Explosive atmospheres • Part 32-1 Electrostatic hazards, guidance • 18.104.22.168.3 Precautions for road tankers
NFPA77, 2019 • Recommended Practice on Static Electricity • Section 12.2 Loading of Tank Vehicles
API Recommended Practice 2003 8th Edition, 2015
• Protection against Ignitions Arising Out of Static, Lightning, and Stray Currents
• 4.2 Tank Truck Loading • 4.2.2 Bonding and Grounding
ADR – Volume II: 2019
• Concerning the International Carriage of Dangerous Goods by Road
• Chapter 4.3 Use of Fixed Tanks (Tank Vehicles), Demountable Tanks, Tank Containers, etc
Energy Institute - Petroleum Road Tanker Design and Construction
• Fourth Edition October 2019
Always check for the latest version/s of the standard/s and recommended practices.
Enquiry No. 27
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