My employers have recently completed the construction of a new tank farm which contains 8 tanks, each holding 17,000 litres of VOC Solvents. The structure is a mixture of ferrous steel with stainless steel tanks, each tank is fully earthed. We are currently in legal limbo with the designer due to inherent flaws and omissions in the design. This currently has no lightning protection and I am looking to establish the requirements of such a system. EN 62305 would suggest (If I understand it properly) that a protection system should be in place. However I question this, as I also understand the 'Faraday Effect' would mean that the structure would be ok. Does anyone have any information that they could share?

The safety of the installation in the event of a direct strike would depend on the conductivity of the path to true earth. You say the install is earthed, however, it would be the impedance of this earth that would be important with respect to protection, plus the current carrying capacity of the pathways to this true earth. The reason for a dedicated LPS is to “guide” and control the flow of the current to a “defined path” through the structure. The rise time, & amplitude of the currents and voltages could cause arcing across high impedance joints in the structure where the current flows, this could also cause localised heating. Furthermore it will introduce potential gradients through the structure which could cause circulating earth currents which could cause problems with PC&I systems. IMHO, you REALLY need to seriously consider the requirement for a dedicated LPS. Are you a COMAH site? Oh and Furse are a reputable company when it comes to LPS.