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 gasifying.
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 referred to the concentration value (V%) of combustible gas at lower explosion limit.
2.0.11 Upper explosion limit (UEL)
It is referred to the concentration value (V%) of combustible gas at upper explosion limit.
2.0.12 Maximum Allowable Concentration (MAC)
It is referred to the concentration of toxic chemicals which shall be exceeded at working site at any time within a working day.
2.0.13 Permissible Concentration - Short Term Exposure Limit (PC-STEL)
It is referred to the Permissible Concentration-Time Weighted Average (time weighting) that the single contact time shall not exceed 15min in a working day.
2.0.14 Permissible Concentration - Time Weighted Average (PC-TWA)
It is referred to the Average Permissible contact Concentration specified by time as weight number within 8h.
2.0.15 Immediately Dangerous to Life or concentration (IDLH)
It is referred to the air pollutant concentration in environments which reaches certain danger level, like deadliness, permanent health damage, or makes person loss the escape ability.
