HAZOP Requires Improved Overfill Protection

HAZOP ATEX Overfill protection

Our customer recently commissioned Denca to design an improved overfill protection system for their safety-critical HAZOP liquid storage area. The area was already classified as an ATEX zoned area. This comes with certain incumbent risks. Fortunately, our in-house team includes over a dozen, ATEX-rated, engineers capable of working within these safety confines. 

The design process started with a thorough survey of the site. This covered the factory layout, the current control system and installed instrumentation. Operating in a HAZOP area, the new system had to be certified as compliant with the following international standards: – 

  • IEC 61508 (2010) Functional Safety of electrical/electronic/programmable electronic safety-related systems 
  • IEC 61511 (2016) Safety Instrumented System for the process industry sector  
  • IEC 60079-10-1 Classification of areas – explosive gas atmospheres 
  • IEC 60079-14 Electrical installations design, selection and erection  
  • IEC 60079-17 Electrical installations inspection and maintenance 

Our team selected a PLC-based solution, utilising a Siemens S7 controller for non-safety I/O networked with an ISP safety PLC for all SIL or functional safety-rated I/O. Additionally, a Siemens touchscreen interface allows direct operator management. The system deals with 35 process tanks, the associated process control devices, and inlet and outlet routing valves. 

The installation was completed with minimum disturbance to factory production. After completing the requisite ATEX and safety checks, we quickly completed a phased shutdown and changeover, to minimise disruption. 

The completed solution is backed up with comprehensive compliance documentation, design calculations and a fully detailed drawing set. We are confident we have a satisfied customer with a flexible and expandable system that will benefit their manufacturing processes for many years ahead. 

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