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Seveso sites

The Seveso III Directive (2012/18/EU), aimed at controlling major-accident hazards involving dangerous substances, establishes comprehensive regulations to prevent and mitigate risks associated with industrial accidents. The focus is on safeguarding human health and the environment at over 12000 Seveso sites across the EU, encompassing chemical plants.

A paramount aspect of this safety framework involves continuous seismic monitoring, where automatic seismic monitoring devices are mandated. These devices play a crucial role during earthquakes, facilitating the following safety measures:

  • Swiftly halting processes and valves to automatically transition the system into a secure state.
  • Recording seismic data for subsequent post-event evaluation.

To ensure robust reliability, typically three instruments per site are deployed in a 2oo3 (2 out of 3) configuration. This means that the relays activate only if at least two instruments exceed predefined thresholds, enhancing the system’s reliability.

At major sites, compliance to Safety Integrity Level (SIL) 2 or SIL 3 certification, as per IEC 61508 standards, becomes imperative.

The primary monitoring requirements for a Seveso site encompass:

  • Acceleration monitoring using a triaxial accelerometer with a full range of ±4 g.
  • A recorder featuring three channels and three relays (dry contact) output. This recorder must support event-based time-history recording for dynamic signal analysis. The accelerometer can either be internal or external to the recorder, with an internal battery serving as a backup in case of power outages, ensuring uninterrupted safety measures.

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