According to GB 16912-1997 Oxygen and Related Gases Safety Technical Regulations on valve materials:
When the pressure is greater than 0.1MPa, the use of gate valve is strictly prohibited.
When the pressure is 0.1MPa<P≤0.6MPa, the valve flap is made of stainless steel.
0.6MPa<P≤10MPa, all stainless steel or all copper-based alloy valves.
When P>10MPa, all copper-based alloy.
In recent years, with the increase of oxygen consumption, large oxygen users are using oxygen pipeline transport. Due to the long pipeline, wide distribution, coupled with the rapid opening or quick closing of the valve, resulting in oxygen pipeline and valve combustion and explosion accidents occur from time to time, so a comprehensive analysis of the oxygen pipeline and the existence of the hidden dangers, dangers, and to take appropriate measures is essential.
- several common oxygen pipeline, valve combustion and explosion cause analysis
1. Rust, dust, welding slag in the pipeline and the pipeline wall or valve mouth friction produces high temperature combustion.
This situation is related to the type of impurities, particle size and air velocity, iron powder is easy to burn with oxygen, and the finer the particle size, the lower the ignition point; the faster the gas speed, the more likely to burn.
2. The existence of pipeline or valve grease, rubber and other low-flammability substances, in the local high temperature ignition.
The ignition points of several combustibles in oxygen (at atmospheric pressure):
Name of the combustible ignition point (℃)
Lubricating oil 273～305
Steel paper pad 304
Rubber 130～170
Fluorine rubber 474
Trichloroethylene 392
Polytetrafluoroethylene 507
3. Adiabatic compression produces high temperature combustible material combustion
For example, before the valve for 15MPa, the temperature of 20 ℃, after the valve for the normal pressure of 0.1MPa, if the valve is opened quickly, the valve after the oxygen temperature according to the adiabatic compression formula up to 553 ℃, which has reached or exceeded the ignition point of some substances.
4. The ignition point of combustible materials in high pressure oxygen is the cause of oxygen pipeline valve combustion.
Oxygen pipeline and valve in high pressure oxygen, the danger is very big, test proved that the detonation of fire can be inversely proportional to the square of the pressure, these oxygen pipeline and valve constitutes a great threat.
- preventive measures
1. Design should be in line with relevant regulations and standards
Design should be in line with the Ministry of Metallurgy issued in 1981, "a number of provisions of the iron and steel enterprises of the oxygen pipeline network," as well as "oxygen and related gases safety technical regulations" (GB16912-1997), "Oxygen Station Design Specification" (GB50030-91) and other regulations and standards.
(1) The maximum flow rate of oxygen in carbon steel pipe shall be in accordance with the following table.
Maximum flow rate of oxygen in carbon steel pipe:
Working pressure (MPa) ≤ 0.1 0.1 ~ 0.6 0.6 ~ 1.6 1.6 ~ 3.0
Flow rate (m/s) 20 13 10 8
(2) In order to prevent fire, after the oxygen valve, should be connected to a length of not less than 5 times the diameter of the pipe, and not less than 1.5m of copper-based alloy or stainless steel piping.
(3) Oxygen pipeline should be as little as possible to set up elbows and bifurcation head, working pressure higher than 0.1MPa oxygen pipeline elbow, should be taken to stamping into the valve type flange production. The airflow direction of the bifurcation head should be at an angle of 45° to 60° to the airflow direction of the main pipe.
(4) In butt-welding concave-convex flanges, the use of purple copper wire for O-ring sealing is a reliable sealing form of flanges for oxygen with flame resistance.
(5) Oxygen piping should have a good device for conductivity, grounding resistance should be less than 10Ω, and the resistance between flanges should be less than 0.03Ω.
(6) The end of the main oxygen pipeline in the workshop should be equipped with a discharge pipe to facilitate the blowing and replacement of oxygen pipeline, in the longer oxygen pipeline into the workshop before the regulating valve, there should be a filter.
2.Installation precautions
(1) All parts in contact with oxygen should be strictly degreased and blown clean with oil-free dry air or nitrogen after degreasing.
(2) Welding should be argon arc welding or arc welding.
3. Operation precautions
(1) Switching the oxygen valve should be carried out slowly, the operator should stand on the side of the valve, open once in place.
(2) It is forbidden to use oxygen to blow the pipeline or use oxygen to test leakage and pressure.
(3) The operation ticket system should be implemented, and the purpose, method and conditions of operation should be explained and stipulated in detail in advance.
(4) Manual oxygen valves with a diameter of more than 70mm are allowed to be operated only when the pressure difference between the front and rear of the valve is reduced to less than 0.3MPa.
4.Maintenance precautions
(1) Oxygen pipeline should be frequently checked and maintained, rust removal and painting, every 3 to 5 years.
(2) The safety valve and pressure gauge on the pipeline should be calibrated regularly, once a year.
(3) Improve the grounding device.
(4) before the fire operation, should be replaced, blowing, blowing out the oxygen content of the gas in 18% to 23% is qualified.
(5) Valves, flanges, gaskets and pipes, fittings selection should be in line with the "oxygen and related gases safety technical regulations" (GB16912-1997) of the relevant provisions.
(6) The establishment of technical files, training operations, maintenance, maintenance personnel.
5.Other safety measures
(1) Improve the construction, overhaul and operation personnel's attention to safety.
(2) Improve the vigilance of management personnel.
(3) Improve the level of science and technology.
(4) Continuously improve the oxygen delivery programme.