1 General provisions
1.0.1 This standard is formulated with a view to ensuring the personal safety and production safety of petrochemical enterprises, monitoring combustible gases or toxic gases leaked during the production process and in storage and transportation facilities and timely alarming to prevent personal injury and fire and explosion accidents.
1.0.2 This standard is applicable to the design of combustible gas and toxic gas detection and alarm system for construction and extension engineerings of petrochemical industry.
1.0.3 In addition to the requirements of this standard, the design of combustible gas and toxic gas detection and alarm system for petrochemical industry shall also comply with those stipulated in the current relevant standards of the nation.
2 Terms
2.0.1 combustible gas
combustible gas or vapour formed after gasification of Class A gas or Classes A and BA combustible liquids, which is also known as flammable gas
2.0.2 toxic gas
toxic gas or vapor that may cause death or permanent health injury of workers through skin contact or breathing during professional activities
2.0.3 source of release
location or place where explosive gas atmosphere and toxic gas atmosphere may be released and formed
2.0.4 detector
an electronic device that converts the concentration of combustible gas, toxic gas or oxygen into electrical signals
2.0.5 open-path gas detector
an open type gas detector for detecting combustible gas or toxic gas clouds in a straight path. Commonly used open-path gas detectors include: infrared gas detectors, laser gas detectors, etc.
2.0.6 field alarming unit/audible and visual alarm unit
an electronic device installed on the site to alert personnel on or near the site by sound, light, or optical rotation. Common ones include: the integrated audible and visual alarm unit on the detector, and the field alarming unit set by zone
2.0.7 alarm control unit
an electronic device that receives the output signal of the detector, displays and records the concentration of the detected gas, emits audible and visual alarm signals, and can send gas concentration alarm signal and alarm control unit fault information to equipment such as graphic display device in the fire control room. When the combustible gas alarm signal is involved in the fire control linkage, the alarm control unit usually adopts a special combustible gas alarm controller that is manufactured according to the product standard for the special combustible gas alarm controller and has been provided with the detection report
2.0.8 sensible range
the concentration range of the detected gas that the detector can detect, which is also called measurement range
2.0.9 alarm set point
the preset alarm concentration value, which is divided into primary alarm set point and secondary alarm set point
2.0.10 response time
the time from the detector contacting the detected gas to reaching stable indication under test conditions. Usually, the response time is the time required for reaching 90% of the stable indication, and the recovery time is the time required for returning to 10% of the stable indication
2.0.11 vertical height
vertical distance from the suction inlet of the detector sensor to the specified reference
2.0.12 lower explosion limit (LEL)
the lower concentration (V%) limit of a combustible gas when it explodes
2.0.13 upper explosion limit (UEL)
the upper concentration (V%) limit of a combustible gas when it explodes
2.0.14 occupational exposure limit (OEL)
the allowable exposure level of a worker that will not cause harmful health effects on the majority of contacts during his/her long-term repeated exposure in the occupational activities. The occupational exposure limits of chemical factors can be divided into three types: maximum allowable concentration, permissible concentration-short term exposure limit and permissible concentration-time weighted average
1 General provisions
2 Terms
3 Basic requirements
4 Location of detection points
4.1 General requirements
4.2 Process units
4.3 Storage and transportation facilities
4.4 Other places where combustible gases, toxic gases diffuse and accumulate
5 Design of combustible gas and toxic gas detection and alarm system
5.1 General requirements
5.2 Selection of detector
5.3 Selection of field alarming units
5.4 Selection of alarm control unit
5.5 Measurement range and setting of alarm value
6 Installation of combustible gas and toxic gas detection and alarm system
6.1 Installation of detector
6.2 Installation of alarm control unit and field alarming unit
Annex A Properties of common combustible gases and vapors
Annex B Properties of common toxic gases and vapors
Annex C Arrangement plan of combustible gas and toxic gas detection and alarm system
Annex D Technical performance table of common gas detectors
Annex E Guide for selection of common gas detectors
Explanation of wording in this standard
List of quoted standards
1 General provisions
1.0.1 This standard is formulated with a view to ensuring the personal safety and production safety of petrochemical enterprises, monitoring combustible gases or toxic gases leaked during the production process and in storage and transportation facilities and timely alarming to prevent personal injury and fire and explosion accidents.
1.0.2 This standard is applicable to the design of combustible gas and toxic gas detection and alarm system for construction and extension engineerings of petrochemical industry.
1.0.3 In addition to the requirements of this standard, the design of combustible gas and toxic gas detection and alarm system for petrochemical industry shall also comply with those stipulated in the current relevant standards of the nation.
2 Terms
2.0.1 combustible gas
combustible gas or vapour formed after gasification of Class A gas or Classes A and BA combustible liquids, which is also known as flammable gas
2.0.2 toxic gas
toxic gas or vapor that may cause death or permanent health injury of workers through skin contact or breathing during professional activities
2.0.3 source of release
location or place where explosive gas atmosphere and toxic gas atmosphere may be released and formed
2.0.4 detector
an electronic device that converts the concentration of combustible gas, toxic gas or oxygen into electrical signals
2.0.5 open-path gas detector
an open type gas detector for detecting combustible gas or toxic gas clouds in a straight path. Commonly used open-path gas detectors include: infrared gas detectors, laser gas detectors, etc.
2.0.6 field alarming unit/audible and visual alarm unit
an electronic device installed on the site to alert personnel on or near the site by sound, light, or optical rotation. Common ones include: the integrated audible and visual alarm unit on the detector, and the field alarming unit set by zone
2.0.7 alarm control unit
an electronic device that receives the output signal of the detector, displays and records the concentration of the detected gas, emits audible and visual alarm signals, and can send gas concentration alarm signal and alarm control unit fault information to equipment such as graphic display device in the fire control room. When the combustible gas alarm signal is involved in the fire control linkage, the alarm control unit usually adopts a special combustible gas alarm controller that is manufactured according to the product standard for the special combustible gas alarm controller and has been provided with the detection report
2.0.8 sensible range
the concentration range of the detected gas that the detector can detect, which is also called measurement range
2.0.9 alarm set point
the preset alarm concentration value, which is divided into primary alarm set point and secondary alarm set point
2.0.10 response time
the time from the detector contacting the detected gas to reaching stable indication under test conditions. Usually, the response time is the time required for reaching 90% of the stable indication, and the recovery time is the time required for returning to 10% of the stable indication
2.0.11 vertical height
vertical distance from the suction inlet of the detector sensor to the specified reference
2.0.12 lower explosion limit (LEL)
the lower concentration (V%) limit of a combustible gas when it explodes
2.0.13 upper explosion limit (UEL)
the upper concentration (V%) limit of a combustible gas when it explodes
2.0.14 occupational exposure limit (OEL)
the allowable exposure level of a worker that will not cause harmful health effects on the majority of contacts during his/her long-term repeated exposure in the occupational activities. The occupational exposure limits of chemical factors can be divided into three types: maximum allowable concentration, permissible concentration-short term exposure limit and permissible concentration-time weighted average
Contents of GB/T 50493-2019
1 General provisions
2 Terms
3 Basic requirements
4 Location of detection points
4.1 General requirements
4.2 Process units
4.3 Storage and transportation facilities
4.4 Other places where combustible gases, toxic gases diffuse and accumulate
5 Design of combustible gas and toxic gas detection and alarm system
5.1 General requirements
5.2 Selection of detector
5.3 Selection of field alarming units
5.4 Selection of alarm control unit
5.5 Measurement range and setting of alarm value
6 Installation of combustible gas and toxic gas detection and alarm system
6.1 Installation of detector
6.2 Installation of alarm control unit and field alarming unit
Annex A Properties of common combustible gases and vapors
Annex B Properties of common toxic gases and vapors
Annex C Arrangement plan of combustible gas and toxic gas detection and alarm system
Annex D Technical performance table of common gas detectors
Annex E Guide for selection of common gas detectors
Explanation of wording in this standard
List of quoted standards
