Truck And Tanker Earthing – Not A Bad Idea Really!
Not a bad idea? That really is an understatement.
As an example, take a vigorous walk along a non-conductive floor covering; the charge can be as high as 20,000 volts. Then touch something. The total energy discharge will be in the region of 10 mJ. That is more than enough energy to ignite most flammable gases. (Read More)
So for a road tanker carrying flammable powders or liquids it isn’t difficult to imagine how the energy discharge can easily exceed 100 mJ.
The correct grounding of a road tanker is absolutely vital but what are the guidelines regarding the correct grounding?
Needless to say, there are guidelines and standards available which can be downloaded – at a price - from the internet but here they are anyway. The available standards, particularly IEC/TS 60079-32-1 (Electrostatic hazards, guidance), describe the processes where static charges can be raised as in the handling of trucks and railway wagons, the loading and unloading of mobile containers and vessels and the mixing and transport of materials. Further relevant standards: NFPA 77 (Recommended Practice for Static Electricity) and the API RP 2003 (Protection Against Ignitions Arising out of Static, Lightning, and Stray Currents) describe, amongst other things, the specific loading of trucks, railway wagons, storage tanks and general work with petroleum products.
According to the standards, ‘Effective grounding is the primary preventative means to avoid dangerous electrostatic discharge and is the most simple, safe and cost-effective way to ensure that static hazards are properly controlled.’ For a truck grounding unit, there is IEC/TS 60079-32-1. This implies that a simple grounding cable, in theory, will suffice. This is quite risky really because how can the tanker driver be absolutely sure that the object that he /she has attached his grounding cable to will provide a good earth?
The most effective way to ensure that a road tanker is correctly earthed is to install an earth monitor. StuvEx manufactures Safe-Ground. This competitively priced and easily installed earthing monitor can be attached to an interlock so if there isn’t a good earth, the truck can’t be discharged. But to make the system still simpler, the unit has a green and red light; if the green light shows, the operator knows that the vehicle is correctly earthed. However, with a red light showing the vehicle isn’t earthed the interlock can be automatically engaged thereby stopping the driver from unloading until the vehicle is correctly earthed.
The possible consequences of not having proper earthing facilities in place are greater than most companies are prepared to contemplate and a good example of this can be found at the Port of Antwerp – Europe’s second largest port - where a new tank park has just been opened. StuvEx won the order to deliver sixty TES01/Ex earthing systems; one for each of the huge storage silos. The silos are used for storing oil additives, intermediates and chemicals. The park receives daily deliveries from bulk tankers and is designated a gas explosion zoned area.
Static electricity is a problem so in addition to the capacitive system that StuvEx has for road tankers, a resistive system is available for use with barrels and other metal objects and a conductive version is available for use with type C FIBC’s.
StuvEx Safety Systems Ltd
+44 1932 571303
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www.stuvex.eu
