[Q&A Question 337] 2017.12.21

①There are combustible materials in the system, including combustible gases, vapors, dust, etc. ②When combustibles mix with air to reach the explosive limit, an explosive gas mixture is formed. ③There must be a ignition source with sufficient energy.

(1) The hydrogen compressor was not purged with nitrogen or hydrogen, so there is air inside the cylinder or in the inlet pipelines; (2) The oxygen content in the nitrogen used for purification was above the specified limit

Oxygen present in the hydrogen medium, pipeline leaks, excessive leakage from the stuffing box, and welding operations taking place in the vicinity

1. Severe leakage of flammable gases: (1) Malfunctioning intake and exhaust valves, as well as poor sealing, lead to leaks that can cause fires and explosions. (2) Severe leakage at the shaft seal caused a fire. (3) Leaks at the valve flanges connected to the high-pressure synthesis system, along with short circuits at the lighting connections, caused a fire and explosion. There was a leak at the base of the pressure gauge on the outlet main pipe of the circulator; high-pressure gas escaped, causing an electrostatic fire and explosion. The cylinder feet of the nitrogen-hydrogen compressor broke, the inlet pipeline leaked, and an explosion occurred upon contact with an open flame. 2. Emission of flammable gases due to corrosion or fatigue fracture: (1) Fatigue fracture of the vent pipe at the outlet of the circulation machine led to ammonia leakage, causing a fire and explosion. (2) Fatigue fracture at the root of the threads of the connecting bolts between multiple cylinders, as well as between the cylinders and the fuselage, caused a large amount of high-pressure gas to be released, leading to ignition and explosion. (3) Damage to the engine body and high-pressure cylinders can lead to a fire in the oil system; poor quality of the cylinder liner materials, along with severe shrinkage defects in the cylinder block, can cause fatigue fractures, resulting in high-pressure gas escaping and triggering an explosion in the space. (4) Fatigue fracture at the root of the piston lock nut threads and at the threads connecting the piston rod to the piston; the impact of the piston rod caused a fire that led to an explosion. 3. Excessive temperature and pressure lead to spontaneous combustion of carbon deposits and burning of combustible materials. (1) Improper selection of cylinder lubricants, incorrect lubricant grades, too much or too little lubricant applied, as well as poor quality of the lubricant, can cause a sharp rise in gas temperature, resulting in the formation of carbon deposits. (2) Poor quality of circulating cooling water, inadequate intercooling effect, and unexpected interruption of the cooling water lead to an increase in gas temperature. Inadequate or incomplete drainage of oil and water from the intercooler, oil-water separator, and air storage tank leads to an increase in dirt and resistance, thereby raising the gas temperature. (3) Leaks are detected using air pressure testing; carbon buildup occurs at high temperatures, leading to intense oxidation and explosions. During the mechanical manufacturing process, impurities such as rust are not removed thoroughly, which results in heat generation. If the filters are heavily contaminated, the inhaled air will contain a high amount of dust, facilitating carbon buildup. (4) Lack of safety measures and modern management tools. 4. Misoperations and violations of safety procedures leading to combustion and explosions: (1) When maintaining nitrogen and hydrogen compressors, aluminum plates were used as blind flanges, which caused high-pressure gases to escape and result in an explosion in the surrounding area; when starting the chiller, the bypass valve and outlet valve were not opened, causing the pressure to rise above the material’s strength limit and leading to an explosion; during the operation of the blower, abnormal noises were detected but the machine was not stopped for inspection in time, resulting in the breakage of the blower’s shaft and a fire and explosion in the oil tank. (2) During the load testing of the compressor used in chemical processing, low-pressure nitrogen was not used for purging or the purging was incomplete, resulting in a combustion explosion. (3) Inadequate oil-free treatment caused the packing to catch fire due to oil, leading to an explosion of the oil collection tank. (4) Mistaking that there was no liquid ammonia at the outlet of the chiller section; failing to take action to remove the liquid ammonia upon hearing the liquid slugging sound, and using a bypass valve, which led to an explosion due to the high temperature causing the liquid ammonia to vaporize. 5. Explosion accidents caused by manufacturing defects or poor management: (1) Damage to the outlet valve of the oxygen compressor leads to overpressure, triggering the safety valve to activate and resulting in fire and explosion; explosions occur in the oil-water separator due to manufacturing defects; buffers explode as a result of water present in the system during operation. (2) Excessively high pressure during operation damages the water seal, causing a large amount of high-pressure gas to be released, which is then ignited by an electric spark. (3) Due to a power outage, the depressurized gas from the propylene gas compressor leaked out; when the machine was restarted, sparks were generated by the relay, causing an explosion in the space. (4) Fire is caused by the aging of the motor insulation, damaging the compressor.

There is air inside the machine, incomplete replacement, and other hazardous gases enter during replacement

(1) The hydrogen compressor was not purged with nitrogen or hydrogen, leaving air inside the cylinder or in the inlet pipelines; (2) The oxygen content in the nitrogen used for purification exceeded the standard levels; (3) The purge air connected to the hydrogen line was not properly sealed.

(1) The hydrogen compressor was not purged with nitrogen or hydrogen, leaving air inside the cylinder or in the inlet pipelines; (2) The oxygen content in the nitrogen used for purification exceeded the standard levels; (3) The purge air connected to the hydrogen line was not properly sealed.

The body is not thoroughly replaced; oxygen, when mixed with hydrogen, forms explosive gases.

(1) The hydrogen compressor was not purged with nitrogen or hydrogen, leaving air inside the cylinder or in the inlet pipelines; (2) The oxygen content in the nitrogen used for purification exceeded the standard levels; (3) The purge air connected to the hydrogen line was not properly sealed.