Discussion on gas detectors
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This post was last edited by The night is cool_OHDH on 2021-5-31 11:12. I. According to the provisions of GB50493, combustible gases refer to those combustible gases or vapors formed by the vaporization of Class A combustible liquids, or Class A and Class B A combustible liquids. Therefore, for Class B flammable gases, a gas alarm system is not necessary under normal circumstances. Paragraph 3.0.2 of the GB50160-2018 Fire Protection Design Code for Petrochemical Enterprises states that: 1. Class B liquids with an operating temperature above their flash point shall be regarded as Class AB liquids. 2. Class A C liquids with an operating temperature above their flash point shall be considered as Class A B liquids. 3. Class B C liquids with an operating temperature above their flash point shall be considered as Class B B liquids. Suppose we have a material called octanol Propanol A, with a flash point of 81°C. Under normal conditions, there is no need for a combustible gas alarm system. However, the operating temperature in this process is 110°C, which is higher than its flash point. According to GB50493, since octanol Propanol A falls into Category A, no such alarm is required; but according to GB50160, a gas alarm system is necessary. I asked an expert once; the alarm system specifications do not state that it is necessary to follow the settings after an upgrade – it should rather remain based on the original classification settings. I’m not sure if this statement is accurate Should it be set up or not? II. Detection range of combustible gases: In cases where the emission sources of production units are located in outdoor areas or within equipment areas in open-type factories, the horizontal distance between a combustible gas detector and any emission source within its detection range should not exceed 10 M. If this range is considered as a circle, what is the diameter of this circle – 10 M or 20 M? ? ? ? III. How should the detector probe be selected when there are multiple flammable gases in the detection range? Assuming there is methanol, tetraisopropyl titanate, or other flammable gases, how should the probe detection be selected? Or should two types of detection probes be installed for media that cannot be detected by the same type of probe? IV. Installation height: According to the latest standards, when detecting flammable gases that are slightly lighter than air, the detector should be installed at a height of 0.5 to 1 meter above the source of emission. How should the installation height for different devices within the same detection area be determined? For example: if there is a height difference of 1.5 M between a pump and a reactor, how should this height be determined when using one detector?
I. Of course, it should be classified according to the operating temperature. II. Diameter: 20m. III. Different components should be set separately. Also, you need to check whether it is flammable as well as toxic; if it is toxic, it should be handled as a toxic gas.
1. Let. 2. Diameter: 20 meters. 3. Set separately. 4. Above the high-level leak source.
Gas detectors are generally of the broadband type, with different repetition settings; however, it would be appropriate to calibrate them using gases with a lower LEL, right?
View GB/T 50493-2019 with diagrams
Therefore, for Class B flammable gases, a gas alarm system is not necessary under normal circumstances. Is this because of you, or is it due to the standards? Writing them together can easily lead to confusion; please edit it again
1. Suppose, in a situation like yours, you already belong to Category B A； 2. With a radius of 10 meters, the diameter is 20 meters ； 3. It can be set separately or as a broad-spectrum setting, with the range determined based on the lower explosion limit of the mixture. 4. It depends on the location of the leak source; if one detector is not sufficient, then install separate ones. The purpose of the detector is to detect leaks as quickly as possible
I agree with the expert’s view in point 1; there is no need for an upgrade. The regulations related to petrochemicals are aimed at assessing fire hazards, and this point isn’t mentioned in 50493 either!
The first question: as I understand it, when a gas leaks, due to the lower temperature of the surrounding environment, the temperature of the gas drops, and either it gets diluted by the surrounding air or it condenses into liquid droplets. It has become difficult to create a flammable gas environment in the gas phase portion.
Thank you to the original poster; it’s practical and great information.