--``,`,,,`,`,``,``,```,,```````,-`-`,,`,,`,`,,`---INDUSTRIAL-PROCESS CONTROL – SAFETY OF ANALYSER HOUSES 1 Scope This International Standard describes the physical requirements for the
General
When determining the location of the AH, the following factors should be considered.
Response time
To ensure acceptable dead times, sample deterioration, and flow rates, it is essential to estimate the line lengths from sample points to the analyzers and calculate the necessary flow rates.
Utilities
Connection lengths to all utilities such as air, steam, electricity, sample return, signals, etc shall be estimated.
Safety
Location
The AH should preferably be located away from external sources of toxic or flammable release, and in a place where accumulation of these substances is not likely to occur.
Escape
Escape routes shall be determined and remain unobstructed and where possible be oriented away from hazardous areas.
Area classification
Area classification for the AH interior and for the ventilation air source shall be determined by the process plant safety authority or user.
Peripheral hazards
Consideration shall be given to the possibility of analysers or their sample lines creating a hazard in the AH or any adjacent room.
Access
Access for maintenance personnel and supplies is essential, with air handling units (AHs) ideally situated at ground level or equipped with elevator access It is important to account for the needs of heavy supplies, such as gas cylinders, and to ensure the safe removal and installation of analyzers.
When designing maintenance access for process equipment like heat exchangers, it is crucial to ensure accessibility to isolation valves for auxiliary supplies, as well as to sampling points and streams outside the air handling unit (AH) This facilitates rapid safety measures for the AH Additionally, access to an external isolation switch for electrical power is essential to enable a complete shutdown of the AH when necessary.
5 Design, construction and layout of AHs
General
Analysers and their sampling systems need different levels of protection based on the sample type, analyser specifications, application significance, and operational environment When construction and maintenance standards do not meet the demands of the working environment, supplementary protection, such as air handling systems (AHs), should be implemented This extra protection is essential for ensuring optimal instrument performance and simplifying maintenance tasks.
The selection of the housing depends on a number of factors such as
When selecting a location for the analyser and sample system, it is crucial to classify the area and consider the range of ambient conditions Factors such as temperature, rainfall, humidity, snowfall, wind, dust, sand, direct sunlight, and corrosive atmospheres must be evaluated to ensure optimal performance and longevity of the equipment.
– environment specified by the analyser vendor for reliable, accurate, and safe operation; – protection required for equipment and personnel during maintenance;
– maintenance and accessibility requirements of the system components;
– process conditions/environment of the area in which the AH is to be located (for example, loading, unloading or transferring of chemicals or equipment, noise, vibration, chemical releases, etc.)
Clause 5 outlines the requirements for air handling (AH) systems situated in hazardous environments where flammable or toxic samples are present In contrast, AH systems located in unclassified areas, which do not handle flammable or toxic materials, are only required to ensure conditions that support accurate and reliable operation.
General requirements
This clause addresses the general requirements for safe operation of an AH regardless of leakage or flammable material (see Clause 6) or material hazardous to health (see Clause 7).
Dimensions and layout
The size of the analyzer housing (AH) is determined by the number, size, and access needs of the analyzers and auxiliary equipment, with considerations for ventilation, drainage, spare parts storage, electrical distribution, and local recording The recommended minimum dimensions are 2.4 m in length and width, with a headroom of at least 2.3 m, while the absolute minimum unobstructed headroom should be 2.0 m To accommodate future equipment additions, a spare space of 30% is advised, and it is important to avoid suspended ceilings, cable trenches, and other dead air spaces.
Structural requirements
Construction materials
Local requirements such as for anti-static properties, corrosion, fire and weather resistance shall be determined and appropriate material selected
Walls
When supporting equipment from walls, it is essential to ensure proper reinforcement Additionally, wall penetrations should be minimized and sealed with materials that comply with relevant structural and safety standards, such as being watertight, fire-retardant, flame-resistant, and possessing adequate mechanical strength.
Floors and foundation
Floors must be non-porous, non-slip, and resistant to potential spills, with considerations for cleaning requirements like a slight slope and drainage If a floor drain is installed, it should effectively drain outside the area for proper liquid disposal Additionally, measures should be implemented to prevent the entry of unwanted liquids, such as elevating the floor above exterior grade level, installing a step or ramp at the entrance, or sealing the base of the house appropriately.
Doors
Doors must open outward and be equipped with self-closing mechanisms or alarm controls They should include a "panic bar" for emergency escape, allowing access from the inside even when locked Additionally, doors must have windows made of shatter-resistant safety glass Depending on the floor area of the assembly hall (AH), a second emergency exit, separate from the first, should be evaluated if the main door's access could be obstructed Furthermore, doors that separate explosive (Ex) zones must adhere to specific requirements outlined in IEC 60079-10-1:2008, Clause A.2, while other safety considerations may take precedence if the AH is part of a larger building.
Windows
Windows must be constructed from shatter-resistant safety glass and securely fixed In areas where explosive hazards may occur, windows should be gas-tight Additionally, the area housing the equipment (AH) should feature observation windows that provide an unobstructed view into the room, with preference given to observation windows in the doors.
Roof
The roof shall be designed for appropriate loads (for example, snow, wind, equipment, people, etc.).
Equipment
Lighting
Lighting or emergency lights shall be operational at all times Light level shall be that required for all works or the level specified by authorities having jurisdiction.
Communications
In situations where safety alarms from the surrounding plant are not audible within the air handling (AH) area, it is essential to replicate these alarms inside the AH Additionally, a reliable communication device must be provided to ensure constant contact with a permanently manned location.
Piping, tubing and valves
Containment systems within the AH must be designed to prevent the escape of hazardous materials during normal operations All piping, tubing, and valves should be clearly labeled, with isolation valves located externally Hazardous waste streams must be managed according to their risk, either by being collected in closed systems or transported to external facilities Lines that could potentially deliver excessive amounts of hazardous materials into the AH during fault conditions must be equipped with flow restrictors or excess flow preventers prior to entry Additionally, the feasibility of installing automatic shut-off valves should be considered.
Utilities
The quantity of hazardous auxiliary substances should be restricted to the minimum necessary to operate the analyser systems
Any fire, explosion or health hazard should be clearly identified
5.5.4.3 Asphyxiants (for example nitrogen, carbon dioxide)
Any asphyxiant line connected to the air handling unit (AH) must include a flow restrictor or excess flow preventer outside the AH This is essential to limit the flow and ensure compliance with the ventilation system requirements.
In situations where a potential low oxygen hazard is present, such as when instrument air is supplemented with nitrogen or when significant amounts of asphyxiant substances may enter the air handling unit (AH) during normal operations, it is essential to monitor the air quality within the AH Low oxygen detectors must be installed, equipped with fail-safe alarms that are accessible both locally and at a remote, permanently manned location.
5.5.4.4.1 Hazardous auxiliary supplies shall be stored outside the AH if possible
When storing auxiliary or calibration gases in pressurized cylinders within the AH, it is essential to protect them from pressure increases due to fire This can be achieved by using insulated and continuously ventilated cabinets or by installing rupture disks and relief valves directly on the cylinders before the pressure-reducing stations Any gas released from the rupture disks must be safely vented outside the AH Exceptions to these safety measures may be permitted with the approval of local authorities.
Fire extinguishers
An appropriate fire extinguisher shall be located near the door(s).
Ventilation
Ventilation may be installed for climate control, corrosion protection, protection from asphyxiation, explosion protection (see Clause 6) and/or personnel safety (see Clause 7)
For optimal safety, the ventilation air source should ideally be located in a non-hazardous area If this is not feasible, zone 2 air can be utilized, provided that the equipment in the air handling unit (AHU) is rated for zone 2 or lower Additionally, it is essential to monitor the ventilation air at the intake with gas detectors that will halt airflow if the lower explosive limit (LEL) exceeds 20% Furthermore, dust filtration must be incorporated into the ventilation inlet to ensure air quality.
To prevent the creation of an explosive atmosphere, a minimum of five air changes per hour must be ensured, unless calculations in IEC 60079-10-1:2008 Annex B indicate a higher flow is necessary Additionally, specific requirements for flammable liquids are outlined in section 6.3.4.
The prevention of the formation of a toxic or asphyxiate gas atmosphere requires a risk assessment to define the rate of ventilation and additional measures where required.
Temperature
For safe performance of the monitoring instruments and alarm systems, temperature shall be kept in their recommended operating range.
Labelling/instructions/documentation
Entrance
A clear and permanent hazard sign may be necessary at the entrance of the Authorized Hazard (AH) area, as mandated by local regulations, indicating that access is restricted to authorized personnel only The sign can also provide essential information about the organization responsible for the AH, including details such as the name, department, and contact number.
Alarms
A comprehensive risk assessment is essential for identifying and displaying critical AH safety-related alarms and indicators These include alerts for ventilation failures, shelter pressure failures, flammable gas concentrations exceeding 20% LEL, toxic gas levels surpassing permissible limits, oxygen deficiency below statutory requirements, fire or smoke detection, automatic extinguisher activation, and faults in gas or fire detection instruments.
The placement and quantity of flammable or toxic gas detectors are influenced by the relative densities of hazardous substances, the size of the area, and the airflow It is essential to position detectors for lighter gases near the ceiling and for heavier gases and vapors closer to the floor.
Alarms shall be reported at the following locations:
1) inside the AH a common audible alarm or a highly noticeable visual light (for example, strobe lamp);
2) at a continuously manned process location, if possible;
3) discrete alarm lamps shall be provided outside near the entrance of the AH for toxic, asphyxiant, and LEL and should be considered for other alarms
A positive indication of a non-hazardous condition is recommended.
Safety procedures
The safety procedures for the AH must be documented and stored in an easily accessible area within the AH It is essential that all personnel working in the AH receive proper training specific to this environment.
Additional data
The following items, as appropriate, should be included in the documentation:
– design data for the ventilation system of the AH (for example, the set point for the ventilation failure alarm);
– design data for the gas detection system (for example, measuring range, measured component, alarm set point and corrective action);
– wiring and logic diagrams for all alarm and shut-down systems;
– design of the toxic process disposal system and information for handling contaminated disposal streams and the exhaust air under upset conditions;
– precise written instructions in clear understandable language about procedures for the personnel that regularly work with toxic material (for example, instructions on filling the supply containers with auxiliary material)
General
Clause 6 outlines the safety requirements for analytical equipment, emphasizing the importance of internal ventilation and protective systems to mitigate internal and external explosion risks It also discusses natural ventilation methods for enhancing safety While additional protective measures for the safe operation of analytical equipment are essential, they are not covered in this standard.
Additional protective measures can be used at the user’s discretion
This standard does not cover hazards from flammable mixtures entering the air handling (AH) system or those discharged back into the plant To mitigate risks, flame arresters may be installed at sampling points, regardless of whether the analyzer is located in the AH.
General requirements
6.2.1 If a risk assessment does not state otherwise, all equipment installed in the AH shall meet the classification for the interior of the AH
In hazardous conditions such as ventilation failure or gas detection, all non-explosion-protected equipment must be disconnected, ideally through an automatic system or manually via an external switch located in a continuously staffed area Restarting this equipment requires proper authorization.
6.2.3 An external isolation switch should also be provided to shut the entire AH down in the event of an emergency Restarting shall not be possible without appropriate authorization.
Protection of AHs against explosion hazards by means of artificial ventilation
Classification
IEC 60079-10-1 gives additional guidance on the classification of hazardous areas
Explosion hazards can originate as follows a) External explosion hazards (see 6.3.2)
An external hazard is deemed absent for an adjacent area of the plant when all openings lead to non-hazardous zones Additionally, internal explosion hazards can arise from flammable gases or vapors, as well as from flammable liquids This includes any combination of these hazards.
Requirements for AHs where the explosion hazard originates externally
Any entrance connecting the AH with zone 1 must have appropriate air lock devices, or all internal equipment must be certified for zone 1 To prevent hazardous atmospheres within an AH, technical implementations of openings, such as doors and supply inlet openings, are essential as outlined in IEC 60079-10-1:2008, A.2.2 Doors should automatically close or be monitored for proper closure Additionally, supplying fresh air as per section 5.5.6 enhances air quality and helps prevent hazardous atmospheres When air intake is from zone 2, ventilation is halted using a gas detector in the suction line when it detects 20% of the LEL, and the system is sealed with an airtight lid In such cases, a ventilating fan rated EPL Gc or higher must be used.
6.3.3 Requirements for AHs where the explosion hazard originates from internal gases or vapours
Inside an AH into which flammable gases or vapours are introduced, there is no danger of explosion
– if the introduced gas flows are restricted, and
To ensure safety, the air handling (AH) system must be designed to prevent flammable gases or vapors from exceeding 50% of the Lower Explosive Limit (LEL) in areas with potential ignition sources during leaks or system failures Enhancing ventilation through the installation of an effective air system can significantly improve local dilution and mitigate risks.
6.3.3.1.1 The AH shall be supplied with fresh air according to 5.5.6 in such a way, that sufficient purging of the room is maintained The function of ventilation shall be monitored
Ventilation openings must be strategically placed based on the density of flammable gases or vapors, with lighter gases venting from the top and heavier gases from the bottom To ensure effective purging, at least half of both upper and lower exits should remain functional in all wind conditions, potentially using weighted louvers Additionally, these openings should be safeguarded with screens to prevent the entry of insects and vermin, as well as measures to avoid debris accumulation like leaves, sand, or snow Relying solely on either upper or lower vents necessitates meticulous ventilation design to guarantee proper purging throughout the area.
To ensure safety in the event of flammable material leakage, the airflow rate must be controlled to prevent exceeding the national acceptable maximum design limit of 50% LEL Implementing permanently installed flow restrictors, high-flow shut-off valves on sample inlet lines, and check valves on return lines can effectively reduce the risk of leakage due to equipment failure, as outlined in IEC 60079-10-1:2008, Clause B.8.
In the event of ventilation failure, it is crucial to ensure that all ignition sources are made safe, including flames, hot surfaces, and non-explosion protected electrical and non-electrical equipment It is important to note that hot surfaces require time to cool below their ignition temperature Devices classified with at least the EPL Gc standard are considered safe for use.
Explosion-proof coupler sockets do not inhibit the connection of non-explosion-protected electrical devices Consequently, it is essential for these sockets to automatically isolate in the event of ventilation failure or a gas detection alarm, especially when non-explosion-protected portable test equipment is connected.
Properly installed gas detectors can enable a temporary delay in shutting down non-explosion-protected equipment However, if the detectors register a predetermined threshold, usually set at 20% LEL, the equipment must be turned off immediately.
Ventilation failure and suitable gas detector alarms shall be signalled as described in 5.6.2 Suitable measures shall be introduced
All pipes which introduce flammable gases or vapours into the AH shall have clearly labelled and readily accessible externally located shut-off valves operated manually and/or automatically
Devices designed to reduce pressure and flow, including excess flow valves, flow restrictors, and orifices, must be positioned outside the air handling unit (AH) when the gas source is external.
Requirements for AHs where the explosion hazard originates from
6.3.4.1 The flashpoints of all incoming liquids shall be documented
This standard is applicable exclusively to liquids with a flashpoint of up to 60 °C Liquids with a flashpoint exceeding 60 °C should only be considered if they can be heated beyond their flashpoint, such as when in contact with a hot device Additionally, it is important to note that sprays may become ignitable even at temperatures below the liquid's flashpoint.
6.3.4.2 Hazards of flammable liquids in the AH should be reduced to a minimum, for example by the following measures:
– collecting of liquid leakages and detecting by suitable sensors followed by an automatic shutdown of the inflow;
– accumulated liquids will be manually or automatically discharged to the AH exterior in such a way that no explosion hazard develops inside or outside the AH
To ensure effective drainage in the area, a floor drain can be installed at the lowest point of the room Additionally, arranging trays at potential leakage points, equipped with leak detection systems and lockable drains, allows for safe disposal of any leaks.
Consideration shall be given to prevent migration of vapours from the vent (for example, by a water seal)
6.3.4.3 The AH shall be supplied with fresh air to maintain purging of the room even if the
LEL can be exceeded A potential exceeding of the LEL depends on the vapour pressure, the surface area of the spill, the latent heat of vaporization and the release rate
6.3.4.4 Fresh air is provided to delay the formation and speed up the safe removal of flammable mixtures It also facilitates detection by transporting the vapours to strategically located gas detectors However, air re-circulation is not recommended because it increases the vaporization rate and increases the risk of exceeding the LEL See calculations in IEC 60079-10-1:2008, Clause B.8
6.3.4.5 Ventilation air exhausts shall be located like those for heavy vapours The air exhaust shall be located such as to collect the vapours above the drain, and a gas detector shall be installed close to the exhaust point
6.3.4.6 In the case of ventilation failure or in the case of detection of leakages, all sources of ignition shall be rendered safe Such sources include flames, surfaces above the ignition temperature, and the non-explosion-protected electrical equipment It has to be considered that hot surfaces need time to cool down below the ignition temperature Devices that meet at least the equipment protection level EPL Gc are classified as safe See IEC 60079-0:2011, 3.26.5
Non-explosion-protected equipment must be turned off immediately when gas detectors signal a predetermined value, usually at 20% of the Lower Explosive Limit (LEL) Additionally, any ventilation failures and gas detector alarms should be reported as outlined in section 5.6.2, and appropriate measures must be implemented.
6.3.4.7 In order to reduce the explosion hazard due to leakage from components and equipment contained in the AH, only the minimum amounts of flammable liquids necessary for measurement shall be introduced into the AH Bypass flows necessary for better time characteristics should be brought only to the outside of the AH All lines which carry flammable substances into the AH shall have easily accessible shut-off devices located externally to the AH If automatic devices are used, they shall be manually lockable and reset
6.3.4.8 To avoid a possible accident and to minimize risks arising from accidental leakages, that portion of the sampling system inside an AH should be as simple as possible with the smallest contained volume and lowest number of joints practicable
Cabinets housing sampling equipment should ideally be located outside the air handling (AH) area and equipped with drain holes Additionally, cabinets that store high-pressure fluids which vaporize at atmospheric pressure must include a rupture disk, with all drain holes and rupture disk exits positioned outside the AH A separate risk assessment and a clear definition of the explosion protection zone are necessary for these cabinets, in accordance with IEC 60079-10-1.
Requirements for AHs where the explosion hazard originates from any
Requirements from the appropriate clauses are added together so that the resultant AH conforms to each individual relevant clause.
Protection of AHs against explosion hazards by means of natural ventilation
General
Natural ventilation is the process of air movement driven by external wind forces and thermal gradients between the atmosphere and the outside environment, without the use of artificial systems When implementing natural ventilation to safeguard against explosion hazards in hazardous areas (AHs), it is essential to consider external factors such as wind conditions, weather patterns, and the explosion zone of the installation site, in accordance with IEC 60079-10-1 standards.
Ventilation requirements
The ventilation rates shall be designed to dilute and dissipate any dangerous release within the AH
Natural ventilation inherently lacks precise control over ventilation rates, necessitating statistical data on wind speeds, directions, and frequencies specific to the proposed location of the air handling unit (AHU) By analyzing this data alongside the heat generated by equipment within the AHU (excluding environmental heaters), it becomes possible to calculate the required ventilation areas.
For optimal area requirements, it is essential to utilize the mode of ventilation that is either wind-induced or thermally induced Wind calculations should be based on the minimum average wind speed that is exceeded for 90% of the year Additionally, calculations for wind or thermal induction should consider a minimum of 10 air exchanges per hour or the amount necessary to achieve effective ventilation.
To ensure safety, it is crucial to dilute escaping vapors from the rupture or failure of hazardous samples or service lines to below the nationally accepted maximum design percentage of Lower Explosive Limit (LEL) near any ignition source, with special attention given to liquids that vaporize at ambient temperatures.
To ensure optimal indoor comfort, it is essential to calculate wind-induced ventilation rates based on maximum average wind speeds, applying a gusting ratio of 1.6 If these ventilation rates surpass 50 exchanges per hour, the comfort level may decline significantly.
Heating requirements
The design procedures ensure that the temperature in the air handling unit (AHU) closely aligns with the ambient temperature To enhance temperature regulation, thermostatically controlled heating can be integrated Additionally, incorporating fan assistance will facilitate the effective distribution of warm air.
Gas detectors
Gas detectors are required to report hazards
In the event of gas leakages identified by detectors, it is crucial to ensure that all ignition sources are made safe This includes eliminating open flames, surfaces that exceed ignition temperatures, and non-explosion-protected electrical equipment It's important to note that hot surfaces require time to cool below ignition temperatures Devices classified with at least EPL Gc are considered safe for use.
Non-explosion-protected equipment must be turned off immediately when gas detectors signal a predetermined value, usually at 20% of the Lower Explosive Limit (LEL) Alarms from gas detectors should be communicated as outlined in section 5.6.2, and appropriate safety measures must be implemented.
7 Measures to prevent health hazards to personnel in AHs
General
Clause 7 serves as a guideline for AH regarding the potential release of toxic substances into the atmosphere, which may occur due to both detected and undetected leaks, as well as during necessary maintenance, calibration, or repair operations It is important to note that this clause does not apply to facilities that manage dust, sprays, aerosols, powders, or non-volatile materials.
Guidelines
Clause 7 provides a framework for standardizing technical regulations and organizational guidelines aimed at safeguarding personnel from health risks while they operate and maintain equipment in an AH.
Clause 7 does not address the creation of any hazard to adjoining rooms or process areas due to leakage from the AH.
General requirements
An AH meeting the requirements of Clause 5 is equipped and operated in such a way that, under normal operating conditions, no toxic or asphyxiant material would spill into the room
There will be no health hazards for individuals temporarily active within the AH, even during abnormal situations and unusual activities The aim is to ensure that the frequency and extent of such activities remain safe.
To ensure a safe working environment in the AH, it is essential to limit potential leakages and maintain controlled risks Adequate ventilation is crucial, and the extent of additional measures required will depend on specific circumstances.
– the identity and quantity of material present in the AH;
– the probability and extent of leakage from the process analyser equipment (see Annex A); – the effect on personnel of toxic material that might be released
The assessment of these measures must be conducted by individuals knowledgeable about the properties of hazardous materials and the analysis equipment, in collaboration with qualified safety personnel.
The decisions arranged hereby determine which of the measures in 7.4 to 7.7 shall be realized.
Safety measures
7.4.1 Toxic materials should not be stored inside an AH If storage of such toxic auxiliary material inside the AH cannot be avoided, the procedure outlined below shall be followed
– A minimum amount of materials shall be stored
To ensure safety, liquid containers must be safeguarded against physical shocks, excessive heat, and any factors that could lead to the release of hazardous substances When using breakable materials, it is essential to implement a suitable secondary containment system to prevent any potential spills within the area or into the environment.
Lines transporting toxic materials to or from the AH must be equipped with manual shut-off devices and features, including double-walled piping, restrictors, and capillaries, ideally positioned outside the AH to reduce the risk of contamination To further minimize the introduction of toxic substances, pre-dilution techniques should be employed, and the sample inject valve of a chromatograph should be placed outside the AH, while the rest of the chromatograph remains inside.
Purge and clean-out connections in sample lines must be strategically installed to enable the connection of devices for safe flushing of fluids This setup ensures that all affected equipment can be properly flushed prior to maintenance, enhancing safety and efficiency.
7.4.4 The AH shall have observation windows that assure an unobstructed view into the room Observation windows in the door(s) are appropriate
Components that regularly manage toxic substances must be designed to minimize leakage risk, adhering to the construction principles outlined in Annex A If this is not achievable, the procedures specified in section 7.4.6 must be followed.
Components that regularly handle toxic substances in an air handling (AH) system, which have an inherent risk of leakage, must be housed within tight, continuously purged enclosures or operated under monitored vacuum conditions The exhaust from these systems should be directed outside the AH and monitored with a flow meter when necessary for safe disposal Additionally, it is advisable to monitor the exhaust to detect any potential leaks in the enclosed modules.
The AH must have a reliable stationary gas detection system capable of quickly and sensitively identifying toxic materials in the air This system should include features such as failure alarms and redundancy, ensuring it can effectively report any instances where concentrations exceed the established limits.
The AH must have emergency communication tools, including a telephone, emergency call station, or panic button, to connect with staff-supervised locations Additionally, if the process unit has a common warning system, such as flashing lights or loudspeakers, the AH should be integrated with this system to alert personnel of potential dangers.
7.4.9 When a system is designed, the toxicity of the substances should be considered
The air may become unsafe to breathe long before the LEL value is attained
Analysers handling toxic substances may need to be separately housed and clearly identified
It is crucial to purge analysers and sampling systems containing toxic or hazardous substances before disassembly Caution is essential when handling analysers that may contain toxic materials, such as reagents in wet chemical analysers and specific construction materials Each installation requires a comprehensive risk assessment due to the unique toxicity of different materials.
Toxic calibration samples shall preferably be stored and piped from outside the AH
A warning sign indicating the potential presence of toxic substances must be displayed on, above, or next to the doors of the AH or cabinet, in accordance with the risk assessment guidelines.
7.4.11 The AH may be equipped with a looped exhaust system that is kept under vacuum
The system must maintain negative pressure continuously or as required, featuring frequent stubs for local hose connections to effectively exhaust toxic substances during upset conditions Alternatively, equipment can be integrated into exhaust hoods It is essential to ensure the orderly detoxification of the exhaust system, which can be achieved by connecting it to the process unit vacuum system.
External hazards
To prevent the accumulation of toxic substances indoors and to block their entry from outside, the AH must be supplied with fresh air as specified in section 5.5.6 A suitable solution is to install a fan in the inlet air ducts, designed to achieve a pressurization of 25 Pa to 50 Pa while ensuring a minimum of five air exchanges per hour Additionally, it is essential to monitor the air exchange process.
7.5.2 Gas detector alarms shall be signalled as described in 5.6.2.
Additional measures for abnormal working conditions
To ensure safety during the operation of process analysers in the AH, it is essential to implement measures for handling the system during abnormal situations, such as cleaning and repairing components This involves opening sample lines, sampling devices, and enclosures that are continuously ventilated for device safety A thorough risk analysis must be performed, and suitable protective measures established Additionally, it is crucial to prevent the reverse flow of toxic gases in purge lines through effective technical and organizational strategies.
Where it could be possible for toxic gases to flow back into purge lines, non-return valves shall be fitted in the purge lines.
Labelling/instructions/documentation
Operational instructions shall be prepared on the basis of risk assessment
– operation manual for all components of the analyser system;
The labelling/instructions/documentation items listed in 5.6 are mandatory for all AHs that may present a health hazard to personnel
Mandatory instruction leaflets must be prominently displayed, including an attendance record for personnel working in the AH at a continuously manned location Additionally, written instructions for special safety procedures should be provided for unusual circumstances, such as loss of ventilation as outlined in section 6.3.3.3, along with necessary substitute arrangements like auxiliary breathing apparatus.
– loss of stationary gas monitor according to 7.4.7 and establishing the necessary substitute arrangements (for example, use of portable gas monitor, providing of safety back-up personnel);
– activation of the stationary gas alarm according to 7.4.7 and establishing the proper breathing device (for example, filtering device, pressure breathing apparatus) and/or activating external shut-off valves
Documentation relative to training courses and the establishment of auxiliary measures as required under abnormal working conditions (see 7.6) may include the following:
1) descriptions of the rinse procedure and the rinsing medium;
3) proper type of breathing device (filtering device, pressure breathing device), providing safety back-up personnel;
4) proper equipment for the safety back-up personnel (for example, breathing device, two- way radios)
Leakage risk of modules in the AH
General
Utilizing construction principles in combination can greatly minimize potential hazards When handling toxic materials, components with limited leakage risk can be incorporated into an AH, provided that the additional measures outlined in column 3 of Table A.1 are implemented.
Non-metallic hoses paired with metal armor and appropriate fittings can serve a function similar to that of metal lines However, applying this principle effectively necessitates a thorough evaluation of each specific situation.
Modules with negligible leakage risk
Modules designed with minimal leakage risk exhibit a low likelihood of releasing toxic or flammable substances in hazardous amounts within the area This assessment relies on the use of suitable materials for their designated functions While there are no established criteria for evaluating intended duties and leakage thresholds, it is feasible to choose modules and construction methods that minimize leakage.
– tightly anchored pipes of proper material;
– flanged connections with appropriate sealing;
– compression fittings with front and back ferrules;
– elastic seals of tongue and groove construction;
– flow meters with all metal housings or of thermal dissipation measuring principles;
– bellow seals (limited life has to be taken into account).
Modules with limited leakage risk
General
Devices that do not meet the rigid requirements of Clause A.2 shall be considered as having limited leakage risk
To assess devices with potential limited leakage risk, utilize the checklist below, which is relevant for flexible hoses made of non-ferrous materials connected with quick connectors or fittings sealed on machine surfaces with O-ring seal chambers Additionally, evaluate sliding gates, membrane pumps, and flow measuring devices featuring open glass cones Critical examination is necessary for devices with optical windows and containers made from fragile materials Each case should be individually assessed based on its specific application, and implementing periodic leakage tests can help mitigate leakage risks.
Guidance for evaluating modules
The following list of questions can provide guidance for evaluating modules (see Table A.1):
– which devices in the process analyser measuring instrument can be expected to have:
– which devices may have leakage rates reduced with construction principles from column 2, by means of additional precautions or through a combination of different design principles (column 3)
The final judgment can be made only with the consideration of conditions such as the requirements of the specific application and proper material selection
Module with no or negligible leakage risk Module with limited leakage risk Additional measures to reduce leakage risk
Rigid metallic Flexible, non-metallic (hose) Double pipe, metal armour
Welded couplings Flanged couplings Check of correct assembly
Compression fittings with front and back ferrules
Flanged couplings with appropriate sealing
Tongue and groove 0-rings Plus bellows seal (see note)
Bellows seals (see note) Packing glands Plus bellows seal (see note)
All metal Glass cone/plastic
Eductor Mechanical seal pumps Bellows seals (see note)
Magnetically or hydraulically coupled pumps Peristaltic pumps Enclosure
Glandless valves Soft seat ball valves Soft seat ball valves with optional bellows seals (see note)
Fibre optics Optical windows Encapsulation
NOTE The bellows seals have limited life
IEC 61115:1992, Expression of performance of sample handling systems for process analysers
IEC TR 61831:2011, On-line analyser systems – Guide to design and installation
EEMUA Publication 138, Design and installation of on-line analyser systems: a guide to technical enquiry and bid evaluation
API RP 550, Manual on installation of refinery instruments and control systems – Part II: Process stream analyzers
API RP 500, Recommended practices for classification of locations for electrical installations at petroleum facilities
NFPA 496, Standard for purged and pressurized enclosures for electrical equipment – Chapter 9: Purged analyzer rooms or buildings
ISA S12.13 Part I, Performance requirements: Combustible gas detectors – Part II: Installation, operation, and maintenance of combustible gas detection instruments
American Conference of Governmental Industrial Hygienist, 1992-1993, “Threshold limit values for chemical substances and physical agents and biological exposure indices” (ISBN 0- 936712-99-6)
4 Emplacement des bâtiments pour analyseurs (AH) et raccordement dans les zones d’installation du processus 37 4.1 Généralités 37 4.2 Temps de réponse 37 4.3 Utilitaires 37 4.4 Sécurité 38 4.4.1 Emplacement 38 4.4.2 Évacuation 38 4.4.3 Classement des emplacements 38 4.4.4 Dangers périphériques 38 4.5 Accès 38
The design and construction of buildings for analyzers require careful consideration of general requirements, dimensions, and layout Structural requirements include the selection of appropriate construction materials, wall specifications, flooring and foundation standards, as well as door and window placements, and roofing considerations Essential materials such as lighting, communication systems, plumbing, utilities, fire extinguishers, and ventilation must be integrated effectively Additionally, maintaining optimal temperature conditions is crucial Proper labeling, instructions, and documentation are necessary, covering entry protocols, alarm systems, safety procedures, and supplementary data to ensure a safe and efficient environment for analyzer operations.
6 Protection des bâtiments pour analyseurs contre l’explosion 43 6.1 Généralités 43 6.2 Exigences générales 43 6.3 Protection des bâtiments pour analyseurs contre les dangers d’explosion au moyen d’une ventilation artificielle 446.3.1 Classement 44
6.3.2 Exigences relatives aux bâtiments pour analyseurs présentant un danger d’explosion d’origine externe 44 6.3.3 Exigences relatives aux bâtiments pour analyseurs présentant un danger d’explosion dû aux gaz ou aux vapeurs internes 44 6.3.4 Exigences relatives aux bâtiments pour analyseurs présentant un danger d’explosion dû aux liquides internes 46 6.3.5 Exigences relatives aux bâtiments pour analyseurs présentant un danger d’explosion dû à toute combinaison des éléments susmentionnés 47 6.4 Protection des bâtiments pour analyseurs contre les dangers d’explosion au moyen d’une ventilation naturelle 47 6.4.1 Généralités 47 6.4.2 Exigences relatives à la ventilation 47 6.4.3 Exigences relatives au chauffage 48 6.4.4 Détecteurs de gaz 48
To ensure the health and safety of personnel in analyzer buildings, it is crucial to implement seven key measures These include general guidelines, specific requirements, and safety measures to mitigate external hazards Additionally, it is important to establish extra precautions for abnormal operating conditions and to provide clear labeling, instructions, and documentation The normative annex addresses the risk of module leaks within analyzer buildings, categorizing modules based on their leakage risk and providing guidelines for their assessment For further reference, a bibliography and an evaluation table for the modules are included.
COMMANDE DES PROCESSUS INDUSTRIELS – SÉCURITÉ DES BÂTIMENTS POUR ANALYSEURS
1) La Commission Electrotechnique Internationale (IEC) est une organisation mondiale de normalisation composée de l'ensemble des comités électrotechniques nationaux (Comités nationaux de l’IEC) L’IEC a pour objet de favoriser la coopération internationale pour toutes les questions de normalisation dans les domaines de l'électricité et de l'électronique A cet effet, l’IEC – entre autres activités – publie des Normes internationales, des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au public (PAS) et des Guides (ci-après dénommés "Publication(s) de l’IEC") Leur élaboration est confiée à des comités d'études, aux travaux desquels tout Comité national intéressé par le sujet traité peut participer Les organisations internationales, gouvernementales et non gouvernementales, en liaison avec l’IEC, participent également aux travaux L’IEC collabore étroitement avec l'Organisation Internationale de Normalisation (ISO), selon des conditions fixées par accord entre les deux organisations
2) Les décisions ou accords officiels de l’IEC concernant les questions techniques représentent, dans la mesure du possible, un accord international sur les sujets étudiés, étant donné que les Comités nationaux de l’IEC intéressés sont représentés dans chaque comité d’études
3) Les Publications de l’IEC se présentent sous la forme de recommandations internationales et sont agréées comme telles par les Comités nationaux de l’IEC Tous les efforts raisonnables sont entrepris afin que l’IEC s'assure de l'exactitude du contenu technique de ses publications; l’IEC ne peut pas être tenue responsable de l'éventuelle mauvaise utilisation ou interprétation qui en est faite par un quelconque utilisateur final
4) Dans le but d'encourager l'uniformité internationale, les Comités nationaux de l’IEC s'engagent, dans toute la mesure possible, à appliquer de faỗon transparente les Publications de l’IEC dans leurs publications nationales et régionales Toutes divergences entre toutes Publications de l’IEC et toutes publications nationales ou régionales correspondantes doivent être indiquées en termes clairs dans ces dernières
5) L’IEC elle-même ne fournit aucune attestation de conformité Des organismes de certification indépendants fournissent des services d'évaluation de conformité et, dans certains secteurs, accèdent aux marques de conformité de l’IEC L’IEC n'est responsable d'aucun des services effectués par les organismes de certification indépendants
6) Tous les utilisateurs doivent s'assurer qu'ils sont en possession de la dernière édition de cette publication
7) Aucune responsabilité ne doit être imputée à l’IEC, à ses administrateurs, employés, auxiliaires ou mandataires, y compris ses experts particuliers et les membres de ses comités d'études et des Comités nationaux de l’IEC, pour tout préjudice causé en cas de dommages corporels et matériels, ou de tout autre dommage de quelque nature que ce soit, directe ou indirecte, ou pour supporter les cỏts (y compris les frais de justice) et les dépenses découlant de la publication ou de l'utilisation de cette Publication de l’IEC ou de toute autre Publication de l’IEC, ou au crédit qui lui est accordé
8) L'attention est attirée sur les références normatives citées dans cette publication L'utilisation de publications référencées est obligatoire pour une application correcte de la présente publication
9) L’attention est attirée sur le fait que certains des éléments de la présente Publication de l’IEC peuvent faire l’objet de droits de brevet L’IEC ne saurait être tenue pour responsable de ne pas avoir identifié de tels droits de brevets et de ne pas avoir signalé leur existence
The international standard IEC 61285 was established by Subcommittee 65B, which focuses on measurement and control equipment, under Study Committee 65 of the IEC, dedicated to measurement, control, and automation in industrial processes.
Cette troisième édition annule et remplace la deuxième édition parue en 2004 Cette édition constitue une révision technique
Les principales modifications par rapport à la précédente édition sont énumérées ci-dessous: a) incorporation du corrigendum paru précédemment; b) mises à jour mineures de plusieurs sections et références
Le texte de cette norme est issu des documents suivants:
Le rapport de vote indiqué dans le tableau ci-dessus donne toute information sur le vote ayant abouti à l’approbation de cette norme
Cette publication a été rédigée selon les Directives ISO/IEC, Partie 2
The committee has determined that the content of this publication will remain unchanged until the stability date specified on the IEC website at "http://webstore.iec.ch" in the data related to the publication in question On that date, the publication will be updated.
• remplacée par une édition révisée, ou
Process analyzers continuously and automatically measure the properties of a process stream The process sample is introduced automatically, and the system is designed to operate autonomously with minimal maintenance.
L’installation de dispositifs d’analyse de processus dans les bâtiments pour analyseurs présente des avantages en termes techniques et économiques afin de:
– faciliter les conditions d’environnement appropriées;
– simplifier les opérations d’entretien et de maintenance;
– permettre l’utilisation d’une infrastructure commune (voir 3.5)
This document outlines the minimum safety requirements for buildings housing type analyzers (AH) It is important to note that these requirements may be superseded by national, local, or corporate regulations that could be more stringent.
COMMANDE DES PROCESSUS INDUSTRIELS – SÉCURITÉ DES BÂTIMENTS POUR ANALYSEURS
This international standard outlines the physical requirements necessary for the safe operation of measurement systems, specifically process analyzers installed in analyzer buildings (AH) It aims to ensure protection against fire, explosion, and health hazards The standard is applicable to analyzer buildings in potentially explosive indoor and/or outdoor atmospheres and addresses risks associated with toxic substances or asphyxiating gases (Refer to relevant national guidelines regarding toxic hazards.)
La présente norme ne traite pas des installations pour lesquelles les solides (poussière, matière pulvérulente, fibres) représentent le danger
La présente norme ne vise pas à aborder l'ensemble des questions de sécurité fonctionnelle liées aux bâtiments pour analyseurs
L’Article 4 traite de l’emplacement du bâtiment pour analyseur et du raccordement dans les zones d’installation du processus