Seek advice on the installation height for acetylene combustible gas detectors
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Recently, while working on the design of an acetylene station, I encountered a highly controversial issue: should the installation height of acetylene gas detectors be determined based on the fact that acetylene is lighter than air, or based on the fact that it is heavier than air? Basically, experienced designers always tell me that acetylene, being a flammable gas, should be designed with the assumption that it is lighter than air; therefore, in all acetylene stations, the sensors are installed above the source of release. However, some people believe it should be installed at the bottom. The basis for this view is the interpretation of Article 3.3.1 of the \"Code for Design of Electrical Installations in Explosive Atmospheres\" GB50058-2014, which states that gases or vapors with a relative density between 0.8 and 1.2, such as carbon monoxide, ethylene, methanol, acetylene, etc., are considered to be substances with a relative density greater than that of air in engineering design; acetylene is explicitly stated to be a substance with a relative density greater than that of air. According to the explanatory notes in clause 6.1.1 of the \"Design Code for Detection and Alarm of Flammable and Toxic Gases in Petrochemical Industries\" GB50493-2009, gases with a relative gas density greater than 0.97 kg/m3 (under standard conditions) are considered heavier than air. As can be found in Appendix A above, the density of acetylene vapor is 1.16 kg/m3, so it should also be considered heavier than air. I’m really confused about this; I don’t know which path to take. I’ve been puzzled for a long time, and I hope everyone can help me figure it out. I’d be extremely grateful!
The installation height, being lighter than air, is 0.5m–2m； The installation height for materials heavier than air is: 0.3m–0.6m ； If you can’t determine whether it is heavier or lighter than air, then take their intersection point, which is 0.5m–0.6m.
Well, first of all thank you for your answer. It’s indeed difficult to determine whether to set it based on being lighter or heavier than air, as the specifications are a bit unclear regarding this matter; I’m not sure if it’s the relative density of 0.8 that determines whether something is lighter or heavier than air. There’s also the intersection you mentioned: for substances that are lighter than air, this range is 0.5m to 2m above the source of release, while for those that are heavier than air, it’s 0.3m to 0.6m above the floor. It seems like there’s no intersection between these two ranges
Is there any problem with being more meticulous in design work according to the specifications? Do you stick all your broken watches to your nose with tape?
Acetylene is considered to be heavier than air, so it should be installed at a height of 0.3 to 0.6 meters above the ground or floor. This is clearly stated in the relevant regulatory provisions. Additionally, according to available literature, gases with a density similar to that of air tend to form clouds that move downward toward the floor level after being released from their source