Combustion and explosion of oxygen pipelines happens frequently, resulting in great losses and many lessons learned. Two more typical explosions of oxygen pipelines occurred in 2008, which is worthy of vigilance.
 
At 9 am on February 22, 2008, an oxygen regulating valve of converter oxygen surge chambers, upstream oxygen filters and pipelines burned and exploded in a large-scale steel company's new steelmaking plant 2#300t. There was a flame, which belonged to a chemical explosion. The regulating valve was burn, leading to a hole. The filter was damaged, and the equipment was seriously damaged. Fortunately, no one was injured. A lot of rust, welding slags and welding rod heads were found after checking the oxygen filter of another converter. These were the remnants of construction, which were not removed before production and completely blocked in front of the oxygen filter. These foreign bodies rubbed and collided with the steel pipe in the high-purity, high-pressure, and high-speed oxygen flows, and became the source of explosion. The oxygen filter was not cleaned regularly, and a lot of foreign matter blocked and rubbed with the filter, which were also the causes of the explosion. It can be seen that the untreated oxygen filter became a safety hazard. When the accident happened, the oxygen pipelines, valves, and pipe fittings were ignited first. The temperature rose sharply. The wall thickness was thinned caused by burning, and the strength dropped rapidly. The oxygen pipeline could not withstand the oxygen's pressure and exploded.
 
At around 10 pm on March 27, 2008, an oxygen valve (a ball valve with DN 300 mm) and pipeline exploded in an oxygen plant of a steel company after the oxygen pipeline was upgraded with the main plant when the valve was opened. Two valve operators died on the spot. The cause of the accident was that the oxygen ball valve was opened too fast under a great pressure difference. The pressure before the valve was 1.9MPa, and the pressure after the valve was 0MPa. The oxygen pipeline should be opened slowly under the pressure difference of 0.3MPa according to the regulations. Moreover, there were many foreign objects such as rust and welding slags due to the staggered new and old pipelines, short construction periods, and lack of purging. At the same time, there was no proper oxygen delivery plan. When the valve was opened, the high-pressure pure oxygen flow entrained rust and welding slags to hit the oxygen valve and pipeline at high speeds or rubbed against them. The oxygen valve and pipeline were ignited, causing an explosion.
 
Explosion mechanism of oxygen pipelines
Analyzing the mechanism of the three elements of combustion and explosion, the material of the oxygen pipeline is generally carbon steel or stainless steel. It contains carbon, which is a combustible material. When ferrite burns, it emits a lot of heat and heats up quickly. The high-purity, high-pressure oxygen transported in the oxygen pipeline is an extremely good oxidant. The higher the purity is, the higher the pressure becomes; the better the oxidation is, the more dangerous it becomes. There are many excitation energy sources that cause the combustion and explosion of the oxygen pipeline, which are as follows:
1. When the valve is suddenly opened between the high and low pressure sections, the oxygen in the low pressure section is compressed sharply. Because of the fast speed, there is no time to dissipate heat, forming the so-called adiabatic compression, where the partial temperature rises sharply and becomes an ignition source.
2. When the valve is opened or closed, the impact and squeeze between the valve disc and valve seat and the friction between the valve parts happen.
3. High-speed moving material particles such as rust, dust, welding slags and impurities rub against the pipe wall, impact on each other, and collide with valves, elbows, reducers and weld beading.
4. External high temperatures such as heating surfaces, flames, radiant heat, etc.
5. Electrostatic induction
6. Ignition caused by grease 
7. The catalytic effect of rust and iron powder
 
Transporting high-purity and high-pressure oxygen in oxygen pipelines made from carbon steel or stainless steel is a practical need for industrial production. In order to eliminate or reduce accidents of oxygen pipelines, necessary measures should be taken in all aspects such as design, manufacturing, installation, use, and management to prevent the formation of excitation energy, which is the key to the safety of oxygen pipelines.