There are two possibilities to analyze the causes of gas boiler room accidents: boiler body explosion, boiler room explosion and gas explosion concentration explosion.
The boiler is a blast furnace body. Due to the existence of explosive or flue gas mixture, when the fire or explosion limit is reached, the heat of the boiler itself is ignited, causing an accident. This is consistent with the relevant provisions of the national building fire protection code. In fact, the current boiler products have considered the safety production measures to avoid it. The qualified gas boiler has its own explosion-proof process design. For example, if the burner stops automatically under abnormal conditions, the automatic control device also stops outputting fuel. The combustion system of the gas boiler has a higher degree of automation, including alarm protection for high and low gas pressure. When the control logic step does not meet the set conditions, the corresponding interlock protection is started.
The possibility of boiler explosion is avoided, but there is another possibility on the ontology. Can it be avoided? How to avoid it?
Three measures
In fact, in the design, according to the standards such as Code for Boiler Design and Code for Design of Automatic Fire Alarm System (GB 50 16- 1998), we have taken the following measures:
Natural gas pipeline valves, instruments, places where gas leakage may occur, and product areas where gas storage may occur in the boiler room [relative density is 0.8, generally in the roof areas of these areas] are all equipped with combustible gas concentration measurement alarm devices, which send out audible and visual alarm signals according to the combustible gas concentration and start the exhaust fan. When the concentration of leakage accident reaches 50% of the lower explosion limit [this value is for reference only], the general intake solenoid valve of the natural intake pipe should be closed immediately.
In the boiler room and the room with natural gas pipeline in and out, it is also interlocked (started) with the combustible gas alarm of the smoke exhaust fan when the incident occurs.
Electrical and instrument cables shall be copper core, and the minimum cross section shall not be less than1.5mm2..
At or near the top of the gas diffusion pipe, the lightning rod should be installed at the top of the pipe jacking tip at least 3m, and its protection range should be at least 1-m above the top of the pipe.
The gas pipeline should have electrostatic grounding device. When the pipeline is made of metal material and connected with lightning protection or electrical engineering protection grounding wire, the measured resistance R is greater than 4Ω. At the pipe joints, such as elbows, flanges, valves and pipes, metal contact is not allowed, and both ends are also bridged with metal flexible wires.
Pressurization measures shall be taken at the doors and windows of boiler rooms and rooms with natural gas pipelines.
According to Article 2.2.2 of Code for Design of Electrical Installations in Explosive and Fire Dangerous Environments, it may be an explosion dangerous area if one of the following conditions is met: Item 3 in devin, near the use of fire-fighting equipment in the production process, combined with these measures, it can be clear that electrical equipment is selected as an explosion dangerous area.
At the same time, according to Article 2.2.2 of Code for Design of Electrical Installations in Explosive and Fire Danger Environments, if one of the following conditions is met, when the explosion danger area is devin: the first two items, and the highest possible flammable and explosive concentration does not exceed the lower limit of 10%, the natural total intake solenoid valve of the air inlet pipe is closed, and the concentration exceeds the lower explosion limit of 10%, and the boiler room is close to the roof.
4 conclusion
In the electrical design of gas-fired boiler room, explosion-proof lamps are used for lighting and explosion-proof lamps are used for other parts.
refer to
[1] boiler design standard. GB5004 1- 1992。
[2] Design standards for electrical devices in explosive and fire hazardous environments. GB50058- 1992。
[3] Code for Fire Protection Design of Buildings. GB500 16-2006。
[4] Design standard of automatic fire alarm system. GB50 1 16- 1998。