IEC 61285-2004 pdf – Industrial-process control – Safety of analyser houses.
1 Scope This International Standard describes the physical requirements for the safe operation of the process analyser measuring system installed in an AH in order to ensure its protection against fire, explosion and health hazards. This standard extends beyond IEC 60079-16 to include houses with Zone 2 interiors and to apply to toxic hazards. (Appropriate national guidelines on toxic hazards are to be followed.) This standard does not address facilities where dust is the hazard. Clause 4 addresses the location of the AH and connection within the process plant areas. Clause 5 addresses the design, construction and layout of the AH. It does not address parts of the analyser measuring system installed in other locations such as sample conditioning rooms (SCR) or switchgear rooms. Clause 6 addresses measures for reducing the danger of explosion for AHs while permitting maintenance of equipment with the power on and the case open. NOTE For most fluids, the major constraint is that the concentration of vapours, which are hazardous for personnel, is lower than the lower explosive (flammable) limit (LEL) (see Clause 7).
Using n-Pentane as an example, the LEL is 1,4 % or 14 000 × 10 –6 . The level immediately dangerous to life or health (which is the maximum level from which a worker could escape within 30 min without any escape-impairing symptoms or any irreversible health effects) is only 0,5 % or 5 000 × 10 – 6 . Classification of a house interior as Zone 1 may imply that no technician can enter without protective equipment such as breathing gear. Placing an AH in a Zone 1 area would usually imply that no technician could approach the house without wearing protective equipment. Clause 7 addresses those measures for protecting personnel from materials in the atmosphere of AHs that are hazardous to health. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60079-16:1990, Electrical apparatus for explosive gas atmospheres – Part 16: Artificial ventilation for the protection of analyser(s) houses 3 Terms and definitions For the purposes of this document, the following terms and definitions apply.
5.3 Dimensions and layout The size of the AH depends on the number, size and access requirements of the analysers and auxiliary equipment. Allowance shall be made for any ventilation, drainage, spare parts storage, electrical distribution, local recording, etc. Recommended minimum dimensions are 2,5 m length and width and 2,3 m headroom. The absolute minimum unobstructed headroom should be 2,0 m. Spare space of 30 % is recommended to facilitate later equipment addition. Suspended ceilings, cable trenches and other dead air spaces should be avoided. 5.4 Structural requirements 5.4.1 Construction materials Construction materials should be fire-retardant and resistant to attack from substances with which they could come into contact. 5.4.2 Walls Local requirements such as for anti-static properties, corrosion, fire and weather resistance shall be determined and appropriate material selected. Where equipment is supported from the walls, appropriate reinforcement may be required. Wall penetrations should be minimized and sealed where appropriate with materials meeting the relevant structural and safety requirements (for example, watertight, fire-retardant, flame-resistant, mechanical strength, etc.).3.1 analyser cabinet small housing in which analysers are installed individually or grouped together. Maintenance is performed from outside the cabinet with the door(s) open 3.2 analyser shelter structure with one or more sides open and free from obstruction to the natural passage of air, in which one or more analysers are installed. The maintenance of the analysers is normally performed in the protection of the shelter 3.3 analyser house (AH) enclosed building or part of a building containing process analysers and associated equipment where streams for analysis are brought in and which is regularly entered by authorized personnel NOTE Within the scope of this standard, the term AH is used regardless of the structure configuration as either a room, cabinet or building and whether or not it is an integral part of, or attached to, another structure. 3.4 sample conditioning room SCR room that is separated from the AH and has modules for sample conditioning, auxiliary material, or sample disposal equipment. 3.5 toxic material material that is a health hazard by inhalation from the surrounding atmosphere. Atmospheric routes such as skin absorption or ingestion are not addressed