AS NZS 60079.29.3:2016 pdf free

AS NZS 60079.29.3:2016 pdf free.Explosive atmospheres Part 29.3: Gas detectors – Guidance on functional safety of fixed gas detection systems
Gas sensors may incorporate a passive filter element to protect the sensor gas membrane from airborne dust, dirt or moisture, or may incorporate a metal sintered disk for explosion protection. AlI types of passive filter elements have a dangerous undetected failure mode (e.g. blockage), therefore require scheduled inspection and proof testing.The stated safety function per sensing point should consider the intrinsic use of such passive filters, therefore should include within the stated safety function an acceptable response time when a proof test is initiated.
Gas sensors may incorporate an active filter element to condition or change the sensed gas or vapour. These active filters should be specified by the manufacturer and will have a defined life time. All filters of this kind have dangerous undetected failure modes (e.g.blockage, saturation and deactivation) and therefore require scheduled inspection and proof testing.
Gas sensors may incorporate a catalyst filter. Such filters da not have a defined life time,however they will suffer the same effects as passive filters. These filters should be treated as passive filters, unless environmental conditions affect the catalyst material. All filters of this kind have a dangerous undetected failure mode, therefore they require scheduled inspection and proof testing.Gases and vapours generate numerous hazards. They may be flammable, toxic or both.
Oxygen levels can be excessive or deficient. Any hazard and risk analysis should consider all hazards associated with gases and vapours, which include short term and long term effects. Gas dispersion should include modelling with consideration to specific gas/vapour densities. The environmental conditions, including the presence of other gases, should be considered.
Some gas detection functions are preventative,while others only mitigate release consequences. Gas detection functions that mitigate release consequences may not be entirely effective even if they activate.Determining the effectiveness of the mitigation function is outside the scope of this International standard but is more a function of plant specific operation and personnel.AS NZS 60079.29.3 pdf free download.