This article is compiled from the interpretation of the revised content of GB50493 in the "Petrochemical Industry Combustible and Toxic Gas Detection and Alarm Design Standard" by Professor Pei Bing'an of Sinopec Luoyang/Guangzhou Engineering Co., Ltd., the main drafter of the GBT 50493-2019 standard.
GBT 50493-2019 "Design Standard for Detection and Alarm of Combustible and Toxic Gases in Petrochemical Industry" will be implemented on January 1, 2020. The original national standard "Design Standard for Detection and Alarm of Combustible and Toxic Gas in Petrochemical Industry" (GB50493-2009) will be abolished at the same time. .
The main contents of the revision of GBT 50493-2019:
1. The name of the standard is changed from "Design Specification" to "Design Standard";
2. The scope of toxic gases is expanded from the poisonous gases listed in the "Catalogue of Highly Toxic Substances" to common highly toxic gases;
3. Added design compatibility, independence and reliability requirements for flammable gas and toxic gas detection and alarm systems (GDS);
4. Added the requirement that the flammable gas and toxic gas detection and alarm system (GDS) should be set up separately from the fire and fire monitoring system;
5. Added open circuit (laser, infrared) detectors, noise detectors, etc. to further improve
6. Added 5 normative standard appendices such as common gas detector selection guide and GDS configuration diagram; 7.
Modified and improved some chapters and clauses of the standard, and canceled the mandatory sexual provisions.
1. Original: Name GB50493-2009 "Design Specification for Detection and Alarm of Combustible and Toxic Gases in Petrochemical Industry"
Current name: GBT 50493-2019 "Design Standard for Detection and Alarm of Combustible and Toxic Gases in Petrochemical Industry"
Description of provisions: According to the national *** standard, as a normative document, all provisions must be mandatory. As a recommended standard, there is no mandatory provision. Provisional.
2. Original: GB50493-2009 3.0.6: Combustible gas physical examination (detection) detectors should adopt products with measuring instrument manufacturing certification, explosion-proof performance certification and fire protection certification of the national designated agency or its authorized inspection unit.
Now: GBT 50493-2019 3.0.5 The combustible gas detector must obtain the measuring instrument type approval certificate, explosion-proof certificate and fire protection product type test report from the national designated agency or its authorized inspection unit; the alarm control unit participating in fire linkage should obtain Special combustible gas alarm controllers with type test reports from the National Fire Electronic Products Quality Supervision and Inspection Center; toxic gas detectors required by national regulations must obtain a measuring instrument type approval certificate from the national designated agency or its authorized inspection unit. Toxic gas detectors installed in explosion-risk locations should also obtain explosion-proof certificates from nationally designated agencies or their authorized inspection units.
Explanation of the provisions: On December 26, 2017, the National People's Congress approved the new Measurement Law to be implemented on December 28, 2017. The main contents of the modification are: canceling the administrative license for manufacturing and repairing metrology (i.e. canceling metrological manufacturing certification), and strictly implementing the type approval license for measuring instruments. Combustible gas detectors currently no longer need to obtain CCCF certification, but when selling, they should obtain a fire product type test report (mandatory) and a fire product certification certificate (the company voluntarily obtains the certificate).
3. Original: GB50493-2009 3.0.9: Combustible gas and toxic gas detection and alarm systems should be set up independently.
Current: GBT 50493-2019 3.0.8: Combustible gas and toxic gas detection and alarm systems should be set up independently from other systems.
Explanation of the article: The combustible gas and toxic gas detection and alarm systems cannot be combined with the production process control system. This is to ensure that the combustible gas and toxic gas detection and alarm systems can still work normally when the production process control system of the process device fails or is out of service. In 2014, the State Administration of Work Safety Supervision General Manager III [2014] No. 116 also clearly required that flammable gas and toxic gas detection and alarm systems should be set up independently. Therefore, when this standard was revised, the GDS setting requirements were re-revised with reference to the relevant requirements of GB50116 and Work Safety Supervision Bureau III [2014] No. 116.
4. Original: GB50493-2009 3.0.11: The combustible gas and toxic gas detection and alarm systems fixedly installed on-site in process equipment and storage and transportation facilities should use uninterruptible units (UPS) for power supply. The flammable gas and toxic gas detection and alarm systems of gas stations, gas filling stations, dispersed or independent operating facilities for toxic, flammable and explosive goods can be powered by ordinary power supplies.
Current: GBT 50493-2019 3.0.9 The power supply load of gas detectors, alarm control units, on-site sirens, etc. of combustible gas and toxic gas detection and alarm systems should be considered as particularly important loads among the primary electrical loads, and should be adopted UPS power supply unit supplies power.
Explanation of the provisions: Decentralized or independent facilities for toxic, flammable and explosive goods, such as gas stations, gas filling stations, etc., are generally panel-mounted or wall-mounted, and the power supply power is small. Therefore, it is stipulated that the detection and alarm system can also be powered by ordinary power supply. .
5. Original: GB50493-2009 3.0.4: The alarm signal should be sent to the on-site alarm and the indicating alarm equipment in the manned control room or on-site operation room, and sound and light alarms should be made.
Now: GBT 50493-2019 3.0.3: Combustible gas and toxic gas detection alarm signals should be sent to the on-site control room, central control room, etc. with on-duty personnel for display and alarm; combustible gas secondary alarm signals, combustible gas and toxic gas detection alarms The fault signal of the system alarm control unit should be sent to the fire control room.
Explanation of the provisions: The fire control room also needs to monitor the fault signals of the combustible gas secondary alarm signal and the alarm control unit of the combustible gas and toxic gas detection alarm system.
6. Original: GB50493-2009 3.0.8: Detectors (detectors) in combustible gas or toxic gas places should be fixed.
Current: GBT 50493-2019 3.0.6 Where combustible gas and toxic gas detectors need to be installed, fixed detectors should be used; where flammable gas and toxic gases need to be temporarily detected, mobile gas detectors should be equipped.
Explanation of the provisions: For some places where fixed combustible gas or toxic gas detectors are not available, mobile combustible gas or toxic gas detectors can usually be installed to ensure the safety needs of production and maintenance. For example: the ambient humidity is too high; the ambient temperature is too low; or it is considered a non-explosive or non-toxic area under normal circumstances. It may be an explosive or toxic hazardous area during production and maintenance. Due to the performance limitations of the tested products, it can usually be installed and moved Type flammable gas or toxic gas detector to ensure the safety needs of production and maintenance.
7. Original: GB50493-2009 2.0.2: Toxic gases: refers to gases that can cause acute or chronic health hazards to workers through their body contact during occupational activities. The scope of toxic gases in this specification is the toxic vapors or toxic gases listed in the "Catalogue of Highly Toxic Substances" (Weifajianfa [2003] No. 142). Common ones include: nitrogen dioxide, hydrogen sulfide, benzene, hydrogen cyanide, ammonia, chlorine, carbon monoxide, acrylonitrile, vinyl chloride, phosgene (phosgene), etc.
Current: GBT 50493-2019 2.0.2: Toxic gases refer to toxic gases or toxic vapors that can cause death or fatal injury through skin contact or breathing by workers during occupational activities.
Explanation: Any gas that can cause death or serious injury through skin contact or breathing is called toxic gas. All need to follow this specification.
8. Original: GB50493-2009 3.0.5: The layout of on-site alarms in the installation area should be comprehensively determined based on the area of the installation area, the layout of equipment and buildings, the physical and chemical properties of the release source, and the on-site air flow characteristics. The on-site alarm can be a sounder or an alarm light.
Current: GBT 50493-2019 3.0.4: The control room operating area should be equipped with sound and light alarms for flammable gases and toxic gases; on-site area alarms should be based on the area occupied by the device, the layout of the equipment and buildings, and the physical and chemical properties of the release source. Set according to the air flow characteristics of the site, and the on-site area alarm should have sound and light alarm functions.
Explanation of the provisions: When the number of flammable and/or toxic gas detectors on site is less than 10, the environmental noise on site is less than 85dBA, and the detectors are equipped with integrated sound and light alarms, the on-site alarm effect will not be affected without affecting the on-site alarm effect. , there is no need to set up an on-site area alarm. When the on-site environmental noise exceeds 85dBA and the integrated sound and light alarm of the detector is difficult to achieve the alarm effect, in order to warn on-site workers, on-site area alarms need to be set up at the main entrances and exits of the production site and high-noise areas.
9. Original: GB50493-2009 3.0.10: The equipment of portable flammable gas and/or toxic gas detectors should be based on the site conditions of the production device, the flammable and explosive characteristics and toxicity of the industrial medium, and the number of operators. Sure.
Current: GBT 50493-2019 3.0.7 On-site workers who enter explosive gas environments and/or toxic gas environments should be equipped with portable flammable gas and/or toxic gas detectors. When the entering environment contains both explosive gases and toxic gases, portable combustible gas and toxic gas detectors can use multi-sensor types.
10. Original: GB50493-2009 A gas with a density greater than 0.97kg/m³ (under standard conditions) is considered heavier than air; a gas with a density less than 0.97kg/m³ (under standard conditions) is considered lighter than air.
Current: GBT 50493-2019 4.1.2 To determine whether the leaked gas medium is heavier than air, the ratio of the molecular weight of the leaked gas medium to the molecular weight of the ambient air should be used as the benchmark.
Ratio ≥1.2, the leakage medium is heavier than air;
1.0 ≤ ratio <1.2, the leakage medium is slightly heavier than air;
0.8﹤ratio﹤1.0, the leakage medium is slightly lighter than air;
Ratio ≤ 0.8, the leakage medium is lighter than air.
Explanation of the article: Since temperature and altitude have a great influence on the density of gas, in order to facilitate the judgment of whether the leaked gas medium is heavier than air when the leaked medium leaks into the atmosphere, this standard uses the relative molecular weight of the gas molecular weight of the leaked medium and the molecular weight of the local air. The ratio serves as a criterion.
11. Original: GB50493-2009 4.4.2 The online analysis instrument room located within Zone 2 of the explosion hazard area should be equipped with combustible gas (detection) detectors.
Current: GBT 50493-2019 4.4.2 The online analysis instrument room located within Zone 2 of the explosion hazard area should be equipped with flammable gas and/or toxic gas detectors, as well as oxygen detectors.
12. Original: GB50493-2009 6.1.1 If the relative gas density is greater than 0.97kg/m³ (under standard conditions), it is considered to be heavier than air; if the relative air density is less than (under standard conditions), it is considered to be lighter than air. When detecting flammable gases and/or toxic gases that are heavier than air, the recommended installation height of the detector should be 0.3m~0.6m higher than the floor (or floor surface). If it is too low, it will easily cause damage to the detector due to rain and splashing; if it is too high, it will exceed the height where air-heavy gases can easily accumulate.
Current: GBT 50493-2019 6.1.2 When detecting flammable gases or toxic gases that are heavier than air, the detector should be installed at a height of 0.3m to 0.6m from the floor (or floor); when detecting flammable gases or toxic gases that are lighter than air When using gas, the detector should be installed within 2m above the release source. When detecting flammable gases or toxic gases that are slightly heavier than air, the detector should be installed 0.5 m to 1m below the release source; when detecting flammable gases or toxic gases that are slightly lighter than air, the detector should be installed at a height higher than the release source. Source 0.5 m～1m (newly added).
Explanation of the provisions: When detecting flammable gases or toxic gases that are lighter than air, the detector should be installed within 2m above the release source. The 09 version specification is: 0.5 to 2m higher than the release source. 6.1.3 The installation height of the ambient oxygen detector should be 1.5 m to 2.0 m from the floor or floor. (New) 6.1.4 Linear combustible gas detectors should be installed in large open environments, and the length of the detection area should not be greater than 100m (New).
13. Original: GB50493-2009 3.0.5 When a limited number of flammable or toxic gas (detection) detectors need to be deployed on site, the on-site alarm can be used to detect flammable and toxic gases without affecting the on-site alarm effect. Probe fitting settings. When a large number of flammable or toxic gas (detection) detectors need to be deployed on site, the on-site alarm should be set up separately from the flammable and toxic gas (detection) detectors, and sound and light warning requirements should be put forward according to the site conditions, and the settings should be partitioned. .
In order to alert on-site workers, on-site alarms are often upgraded to 105dBA speakers. In high-noise areas [noise exceeding 85dBA] and at the main entrances and exits of the production site, polarizing alarm lights are usually set up.
Now: GBT 50493-2019 5.3.2 The sound level of the alarm signal of the regional siren should be higher than 110dBA (the 09 version standard is 105dBA), but the total sound pressure value 1m away from the siren shall not be higher than 120 dBA.
Explanation of the provisions: The selection of on-site alarms has been revised from the original 105dBA speaker to 110dBA.
14. Original: GB50493-2009 3.0.2 The first-level alarm for flammable gas and toxic gas detection is a conventional gas leakage warning alarm, which prompts the operator to go to the site for inspection. When the concentration of flammable gas and toxic gas reaches the secondary alarm value, the operator is prompted to take emergency measures. When linkage protection is required, the output contact signal of the secondary alarm can be used. When flammable gas and toxic gas leakage accidents occur on site, in order to protect the health of on-site workers and facilitate timely handling by operators, the detection alarm signals of toxic gas and flammable gas sent out at the same time should be handled according to the principle that the second-level alarm takes precedence over the first-level alarm. level alarm; when the alarm level is the same, the alarm level of toxic gas takes priority.
Now: 3.0.2 The detection alarm of flammable gas and toxic gas should adopt a two-level alarm. When toxic gases and combustible gases of the same level alarm at the same time, the alarm level of toxic gases should take priority.
Explanation of the provisions: ① The first-level alarm is a gas leak warning, prompting the operator to go to the site for inspection and treatment in time; ② The second-level alarm is an emergency gas leak alarm, prompting the operator to take emergency measures; ③ When a gas leak requires linkage protection, it should The second-level alarm contact signal is used as the linkage protection condition; ④ The on-site detector's own alarm accepts the first- and second-level alarm signals output by the detector, and the on-site regional alarm accepts the second-level alarm signal output by the GDS system.
15. Present: GBT 50493-2019 3.0.1 In the areas of production facilities and storage and transportation facilities that produce or use flammable gases and toxic gases, when the concentration of combustible gases in the leaked gas may reach the alarm setting value, combustible gas detectors should be installed; the concentration of toxic gases in the leaked gas may reach the alarm setting value. When setting the value, a toxic gas detector should be set; Combustible gas is a single-component gas medium of toxic gases, and only toxic gas detectors are provided; multi-component mixed gases where flammable gases and toxic gases exist at the same time, the concentration of combustible gas and the concentration of toxic gases may reach the alarm setting at the same time when leaking value, combustible gas and toxic gas detectors should be set separately.
Explanation of the article: For mixed gases containing multiple toxic gas components, or when the composition of leaked gases under different working conditions is greatly different, when the gas concentration of each toxic gas component may reach the toxic gas concentration alarm of each component When setting the value, in order to ensure production safety, toxic gas detectors need to be set separately.
16. Original: GB50493-2009 4.1.2 The following main release sources that may leak flammable gases and toxic gases should be equipped with detection points: 1. Seals of gas compressors and liquid pumps; 2. Liquid sampling ports and gas sampling ports; 3. Liquid drain (water) port and vent port; 4. Flanges and valve sets of equipment and pipelines;
now: GBT 50493-2019 4.1.3 Detection points should be arranged around the release source of flammable gas and/or toxic gas: 1. Dynamic seals of gas compressors and liquid pumps; 2. Liquid sampling ports and gas sampling ports; 3. Liquid/gas drain (water) ports and Vent; 4. Frequently disassembled flanges and frequently operated valve groups.
Explanation of the provisions: According to the "Code for Design of Electrical Equipment in Explosive Hazardous Environments" GB50058, release sources should be divided into continuous release sources, first-level release sources and second-level release sources according to the frequency and duration of release of substances. Level 1 release source: released periodically or accidentally during normal operation; Level 2 release source: not released under normal circumstances, and even if released, it is only released occasionally for a short period of time. The main objects detected by flammable gas and toxic gas detectors are equipment or places that are secondary release sources.
17. Current: GBT 50493-2019 4.3.1 Detectors should be installed in the fire dikes of liquid storage tanks that generate flammable gases such as liquefied hydrocarbons, Class A B, B, and A liquids. The horizontal distance between a combustible gas detector and any release source within its coverage should not be greater than 10m, and the horizontal distance between a toxic gas detector and any release source within its coverage should not be greater than 4m. Note: AQ3036-2010 "Regulations on the Setting of On-site Safety Monitoring
Equipment in Tank Areas with Major Hazardous Sources of Hazardous Chemicals " requires 7.2.1.1: For flammable gas or flammable liquid storage tank locations, a flammable gas alarm should be installed every 20 to 30m in the fire dike. The distance between the monitoring and alarm device and the drainage outlet, connection, valve and other easily released materials of the storage tank should not be greater than 15m.
18. Current: GBT 50493-2019 3.0.10 When determining the occupational exposure limit of toxic gases, the maximum allowable concentration, time-weighted average allowable concentration, and short-term exposure allowable concentration should be selected in the order of priority.
Explanation of the article: The three occupational exposure limits (OEL) values of toxic gases from low to high are: *** allowable concentration MAC, time-weighted average allowable concentration PC-TWA (8 hours a day, 5 days a week), short-term allowable concentration Time exposure to allowable concentration PC-STEL (15 minutes). According to the current manufacturing level of toxic gas detectors at home and abroad, if there is no detector option on the MAC market, and on the premise of ensuring the health and safety of operators, there are toxic gases with multiple occupational exposure limits at the same time, and the MAC and PC should be used. -TWA and PC-STEL are selected in priority order; toxic gases that do not provide an OEL value can be selected according to the direct lethal concentration IDLH.
19. Current: GBT 50493-2019 5.4.3 When combustible gas detectors participate in fire protection linkage, the detector signal should first be sent to a special combustible gas alarm controller that has obtained the type inspection report of the National Fire Electronic Products Quality Supervision and Inspection Center, and the alarm signal The special combustible gas alarm controller should be output to the fire alarm controller in the fire control room. There should be a clear distinction between combustible gas alarm signals and fire alarm signals in the fire alarm control system.
20. According to the relevant regulations and requirements of GB50493, GB50116 and the Work Safety Supervision Administration No. 3 [2014] No. 116, the flammable gas and toxic gas detection and alarm system (GDS) should be designed according to the following principles:
1. The GDS system should consist of combustible gas or toxic gas detectors, on-site area alarms and indoor alarm control units. On-site toxic gas detectors should be equipped with integrated sound and light alarms, and combustible gas detectors can be equipped with integrated sound and light alarms. 2. The alarm control unit should adopt independently configured microprocessor-based electronic products (including independently configured PLC, special gas alarm controller, DCS controller, etc.). 3. When the alarm control unit sends out a secondary alarm signal, the regional alarm installed in the corresponding alarm zone on site should be triggered. 4. The combustible gas secondary alarm signal and the fault signal of the alarm control unit should be sent to the fire control room for graphic display and alarm. A separate monitor can be set up. 5. When the combustible gas detector participates in fire linkage, the detector signal should first be sent to a special combustible gas alarm controller that has obtained the type inspection report of the National Fire Electronic Products Quality Supervision and Inspection Center. The fire linkage signal is output by the alarm controller to the fire control room. The fire alarm controller implements the fire linkage function. The combustible gas detector signal cannot be directly connected to the input circuit of the fire alarm controller. 6. When the combustible gas or toxic gas detection signal is used as the input of the safety instrumented system (SIS), the detector should be set independently. The detector configuration should be determined based on the SIL loop rating results and meet the "Petrochemical Safety Instrumented System Design Specification" GB /T 50770 relevant provisions.
Note: When the detector signal is used for warning and alarm, the GDS alarm control unit can use an independent microprocessor-based electronic product. It does not need to obtain SIL certification or fire product type inspection report; the detector When the signal is used for fire linkage, the GDS alarm control unit should use a special combustible gas alarm controller that has obtained the type inspection report of the National Fire Electronic Products Quality Supervision and Inspection Center; when the detector signal is used for safety interlocking, according to the "Petrochemical Safety Instrument System" Design Specification》GB/T 50770 relevant regulations state that interlocking signals with safety levels of SIL1 and below can be connected to GDS, and interlocking signals with safety levels of SIL2 and above should be connected to SIS.