UDC NATIONAL STANDARD OF THE PEOPLE s REPUBLIC OF CHINA 中华人民共和国国家标准 p GH 50493-2009 Specification for Design of Combustible Gas and Toxic Gas Detection and Alarm for Petrochemical Industry 石油化工可燃气体和有毒气体检测报警设计规范 GB/T 50493-2009 -- How to BUY & immediately GET a full-copy of this standard? 1. www.chinesestandard.net; 2. Search --> Add to Cart --> Checkout (3-steps); 3. No action is required - Full-copy of this standard will be automatically & immediately delivered to your EMAIL address in 0~60 minutes. 4. Support: Sales@ChineseStandard.net. Wayne, Sales manager Issued on: March 19, 2009 Implemented on: October I, 2009.Jointly Issued by Ministry of Housing and Urban-Rural Construction of the People s Republic of China General Administration of Quality Supervision, lns1 ection and Quarantine of the People s Republic of China
Contents General Provisions....... 1 2 Terms................................. 2 3 General Requirements....... 4 4 Determination of Detection Points...... 6 4.1 General Rules....................................... 6 4.2 Process Unit................. 6 4.3 Storage and Transportation Fa 巳 iliti 巳 s.............. 7 4.4 Other Combustible Gas or Toxic Gas Diffusion and Accumulation Site... 8 5 Combustible Gas And Toxic Gas Detection Alarm System................. 9 5.1 Technical Performanc 巳........................ 9 5.2 Selection of Detector............................. 9 5.3 Selection oflndication Alarm Device............... 10 6 Detectors and Indication Apparatus Installation...................................... 12 6.1 Detector Installation................................ 12 6.2 Indication Appara 饥 is and Onsite Alarm Installation................. 12 Appendix A Properties of General Combustible Gas and Vapor........................ 吃........ 13 Appendix B Properties of General Toxic Gas and Vapor......... 17 Appendix C Technical Performance Table of Detector for General Gasses........... 18 Explanation of Wording in This Code................... 19
1 General Provisions 1.0.1 This standard is formulated with a view to preventing personal injury, and fire and explosion accidents, and ensuring the safety of petrochemical enterprises. 1.0.2 This standard is applicable to the combustible gas and toxic gas detection and alarm design of new, expended or rebuilt works for petrochemical enterprises. 1.0.3 Besides the provisions of this standard, the combustible gas and toxic gas detection and alarm design for petrochemical industry shall meet the requirements of the current related national standards.
2 Terms 2.0.1 Combustible gas It is referred to Class A combustible gas or the combustible gas generated after Class A and B flammable liquid gasi 马 r ing. 2.0.2 Toxic gas It is referred to the Gasses which cause acute or chronic health harms on workers by body contact in the employment activities. The scope of toxic gas in this standard is toxic vapour toxic gas listed in acute toxic substances" (Wei Fa Jian Fa [2003] No.142). The general toxic vapours or toxic gases are as: nitrogen dioxide, hydrogen sulfide, benzene, hydrogen cyanide, ammonia, chlorine gas, carbon monoxide, acrylonitrile, vinyl chloride and phosgene. 2.0.3 Source of release It is referred to the Position or site which releases explosive gas mixture or toxic gas. 2.0.4 Detector It is referred to the electronic unit which can convert the concentration of combustible gas and toxic gas into electrical signal, and it is composed of sensor and transducer. 2.0.5 Indication apparatus It is referred to the electronic devices which receive the output signal of detector and send Indication, alarm and control signals. 2.0.6 Sensible range It is referred to the range of the detected gas that can be detected by detector under the test condition. 2.0. 7 Alarm set value It is referred to the pre-set alarm concentration value of warning device. 2.0.8 Response time It is referred to the time from detector contacting gas to stably indicating value under test condition. 90% of the time to reach the stable indicated value is adopted as response time; 10% of the time to restore to stable indicated value is adopted as recovery time. 2.0.9 Vertical height It is referred to the vertical distance from the detection opening of detector to the appointed reference object 2.0.10 Lower explosion limit (LEL) It is re 也 rred to the concentration value (V %) of combustible gas at lower explosion limit 2
3 General Requirements 3.0.1 When possible combustible gas and toxic gas leak is detected in the area for process unit producing or using combustible gas and toxic gas, and for storage and transportation facilities, combustible gas and toxic gas detector shall be arranged according to the following prov1s1ons: 1 Combustible gas or combustible gas with toxic gas is leaked, and the concentration of combustible gas may reach 25% of the lower explosion limit nut the toxic gas cannot reach maximum allowable Concentration. At this time, combustible gas detector shall be equipped; 2 Combustible gas or combustible gas with toxic gas is leaked, and the concentration of combustible gas may reach the lower explosion limit nut the toxic gas cannot reach 25% of maximum allowable Concentration. At this time, toxic gas detector shall be equipped; 3 In the place where combustible gas and toxic gas are stored together, the concentration of combustible gas may reach 25% of lower explosion limit, and the concentration of toxic gas may also reach maximum allowable Concentration. At this point, combustible gas and toxic gas detectors shall be all equipped; 4 When a gas is both combustible gas and toxic gas, only toxic gas detector shall be equipped. 3.0.2 Two-level alarm shall be adopted for the detection system of combustible gas and toxic gas. When the toxic gas and combustible gas detectors simultaneously alarm in same detection area, the following principles shall be complied with: 1 In same level alarm, toxic gas alarm shall be preferential; 2 Level 2 alarm has priority over level 1 alarm. 3.0.3 If the process has special requirements, or runs normally, staffs must not ent 巳 r hazardous area, continual detection, Indication and alarm should be taken for the release source of combustible gas and toxic gas, and alarm should be recorded and printed. 3.0.4 Alarm Signal shall be sent to site warning device and indication apparatus at attended control room or site operation room, and audible and visual alarm shall be available. 3.0.S The arrangement of the site warning devices in equipment zone shall be determined according to the following factors: area of equipment zone, arrangement of equipment and structure, physico-chemical properties of release source and site air flow character. Site warning device may be sounder or alarm lamp. 3.0.6 Combustible gas detector shall be the products which the measuring instrument production certification, explosion protection performance certification and fire control certification are approved by the institution designated by the country. 3.0. 7 Toxic gas detector specified by the laws of the country shall be the products which the measuring instrument production certification is approved by the institution designated or 4
4 Determination of Detection Points 4.1 General Rules 4.1.1 The detection points of combustible gas and toxic gas detectors shall be arranged on the positions where gas is easy to accumulate and sampling or detection is convenient, according to the following conditions: gas physicochemical property, characteristic of release source, production yard layout, geographic conditions, environmental climate and operating and patrol examining route. 4.1.2 Detection points shall be arranged for the following release sources with possible combustible gas or toxic gas leak: 1 Sealing of gas compressor and liquor pump; 2 Liquid and gas sampling ports; 3 Liquor drainage opening or vent; 4 Flange and valving for equipment and pipes. 4.2 Process Unit 4.2.1 When release sources are located on the equipment sections of open-air or open-type facility Layout, the distance from detection point and release source shall meet the following requirements: 1 When the detection point is located on windward Side of the all-the-year least frequency wind direction, the distance from combustible gas detection point to release source should not be larger than 1 Sm, and the distance from toxic gas detection point to release source should not be larger than 2 m; 2 When the detection point is located on leeside of the all-the-year least 仕 equency wind direction, the distance from combustible gas detection point to release source should not be larger than Sm, and the distance from toxic gas detection point to release source should not be larger than 2 m; 4.2.2 When combustible gas release source is located on semi-open workshop building of closing or imperfect local ventilation, a detector may be ranged per I Sm, and the distance from the detector to any release source within this coverage should not be larger than 7.Sm. The distance from Toxic gas detector to the release source should not be larger than lm. 4.2.3 When lighter-than-air combustible gas or Toxic gas release source is located on semiopen workshop building of closing or imperfect local ventilation, detector shall be arranged over the release source, beside combustible gas or toxic gas detector shall be arranged on the highest position where gas is easy to accumulate in the workshop building. 6
4.3 Storage and Transportation Facilities 4.3.1 Detectors shall be arranged in fire dike of the stock tanks for Liquids (like liquefied hydrocarbon, Class A2 and Bl Liquids) that generate combustible g 邸, and th 巳 y shall meet the following requirements: 1 When the detection point is located on windward Side of the all-the-year least frequency wind direction, the distance from combustible gas detection point to release source should not be larger than 15m, and the distance 企 om toxic gas detection point to release source should not be larger than 2m; 2 When the detection point is located on leeside of the all-the-year least frequency wind direction, the distance from combustible gas detection point to release source should not be larger than 5m, and the distance from toxic gas detection point to release source should not be larger than 2m; 4.3.2 The arrangement of loading and unloading facilities for liquefied hydrocarbon Class A2 and Bl liquids shall be in accordance with the following requirements: 1 As for railway loading and unloading trestle work with small crane, a detector should be arranged every other berth on the ground, and the horizon distance from the detector to the loader opening shall not be larger than 15m; 2 A detector should be arranged for railway loading and unloading trestle work with large crane; 3 The horizon distance from detector to lorry loader crane on lorry loading depot shall not be larger than 15m. When buffer tank is equipped on lorry loading depot, the arrangement of detector shall meet the requirements of Article 4.2.1. 4.3.3 The detectors for pump or compressor on loading and unloading facilities shall meet the requirements of Section 4.2. 4.3.4 The arrangement of the detectors for liquefied hydrocarbon tank filling station shall be in accordance with the following requirements: 1 Between sealed or semi-open tanks, the distance from filling tank open to detector should be 5m~ 7.Sm; 2 The storehouse for sealed or semi-open tanks shall meet the requirements of Article 4.2.2; a detector shall be arranged on per l Sm~ 30m along the circle on open tank storehouse. When the total side of the circle is less than l Sm, a detector shall be equipped; 3 The distance from buffer tank drainage outlet or valve box to detector should be 5m~ 7.5m. 4.3.5 Between sealed or semi-open hydrogen gas tank, detectors shall be arranged on the indoor highest position (over the opening of the tank) where gas is easy to accumulate. 4.3.6 At discharging quay with potential combustible gas transpiration, a detector shall be arranged within 1 Sm on the horizontal plane of loading arm. 7
5 Combustible Gas And Toxic Gas Detection Alarm System 5.1 Technical Performance 5.1.1 The output signal of detector should be digital signal, contact signal, milli-ampere signal or Millivolt signal. 5.1.2 The warning system shall have historical event recording function. 5.1.3 The technical performance of the system shall meet the requirements of the current national standard Gas Monitors and Alarms for Workplace Atmosphere General Technical Requirements" GB 12358, and Combustible Gas Alarm Control Units" GB 16808; the explosion protection Performance of the system shall meet the requirements of the current national standard Electrical Appara 阳 s Used in Explosive Atmosphere" GB 3836. 5.2 Selection of Detector 5.2.1 The selection of combustible gas and toxic gas detector shall be determined according to the technical performance of detector, physicochemical property of detected gas and production environment feature. 5.2.2 The selection of detector for general gas shall meet the following provisions: 1 Catalytic combustion or infrared gas detector may be adopted for hydrocarbon combustible gas. When air in the usage space contains the media that can poison catalytic combustion detecting element (such as sulphur, Phosphorus, silicon, lead and halogen compound), catalytic combustion detector with toxin Immunity shall be adopted; 2 Infrared gas detector should be adopted at the place of oxygen deficit or higher corros1vity; 3 Catalytic combustion Type, electrochemistry Type, heat conduction Type or semiconductor Type detector may be adopted for detecting hydrogen gas; 4 Heat conduction Type detector should be adopted to detect single-component combustible gas; 5 Chemical type or semiconductor Type detector may be adopted for detecting hydrogen sulfide, chlorine, alkaline air and acrylonitrile gas; 6 Semiconductor Type or photoionization Type detector may be adopted for detecting vinyl chloride gas; 7 Electrochemistry type detector should be adopted for detecting hydrogen cyanide gas; 8 Semiconductor Type or photoionization Type detector may be adopted for detecting benzene gas; 9 Chemical type or in 企 ared gas detector may be adopted for detecting phosgene. 9