Location of rack rooms in the Oil & Gas refinery plant - Hazardous area

Hi all,

Can anyone explain about the location of DCS/SIS Control panels in rack room comes under which hazardous area in the Oil & Gas Refineries?

The location of Distributed Control Systems (DCS) and Safety Instrumented Systems (SIS) control panels in rack rooms and their corresponding hazardous area classification is an important aspect of the design in Oil & Gas Refineries.

Distributed Control Systems (DCS)

DCS is responsible for the process control within refineries, and their design and location are governed by the specific regulations and standards for hazardous areas.

Hazardous Area Classification for DCS:

  1. General Area (Non-Hazardous): Typically, DCS panels are located in a safe control room environment. They are kept away from any areas where flammable gases or vapors might be present, usually in a General Purpose or Non-Hazardous location.
  2. Control Room Design: The control room is often designed with fire suppression systems, HVAC systems for climate control, and segregated air supplies to prevent any hazardous gases from entering the area.
  3. Physical Barriers: Sometimes, physical barriers such as blast walls are used to protect the DCS panels and personnel from potential explosions.

Safety Instrumented Systems (SIS)

SIS is designed to bring a process to a safe state when pre-defined conditions are met. These are critical for emergency shutdown systems.

Hazardous Area Classification for SIS:

  1. Hazardous Areas (e.g., Zone 2): SIS panels may be located closer to the process areas and might fall within a hazardous area classification, such as Zone 2. This is a region where a flammable atmosphere is not likely to occur in normal operation but might occur for short periods.
  2. Intrinsically Safe Design: If SIS panels are located in hazardous areas, they must be designed to be intrinsically safe. This means that they will not create sparks or heat that could ignite a flammable atmosphere.
  3. Separation from DCS: To ensure independence and redundancy, SIS should be physically separated from DCS.


  • DCS Control Panels: Generally located in non-hazardous areas (General Purpose Areas) with proper safety measures.
  • SIS Control Panels: Might be located in hazardous areas like Zone 2, requiring specific design considerations to ensure safety.

Compliance with Standards

It is crucial to follow regional and international standards like IEC 60079, NFPA 70, and local regulations that govern the classification and installation of equipment in hazardous areas. This ensures that the location of DCS and SIS panels is compliant with the required safety protocols.

Designing and classifying the areas where control systems are located requires a detailed understanding of the processes, the chemicals used, and the potential risks. A thorough risk assessment and collaboration with safety experts and regulators is essential in defining these areas accurately.

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Thanks Mike for your valuable answer. Really appreciate it.