Oxygen Valve Safety Operation Guide

Oxygen is widely used in various industrial processes, such as metal cutting, welding, and medical equipment. However, the safe operation of oxygen valves has always been an important issue in industrial safety. Once an oxygen valve catches fire or explodes, it can not only cause huge economic losses but also endanger the lives of personnel. Therefore, it is crucial to understand the causes of oxygen valve combustion accidents and the preventive measures.

Causes of Oxygen Valve Combustion Accidents

Oxygen valves are extremely common in industrial applications, and their safety is directly related to the stability of the production process and the safety of personnel. However, combustion accidents of oxygen valves occur from time to time in actual operations, causing great losses to enterprises and personnel. So, what causes combustion accidents of oxygen valves?

1. Presence of Low Ignition Point Combustible Materials

The presence of low ignition point combustible materials in oxygen pipelines is a prerequisite for combustion accidents of oxygen valves. These materials mainly include iron (Fe) and iron oxide (FeO) powders. Under normal circumstances, the ignition points of these materials are between 300 and 400 degrees Celsius. When they burn rapidly in oxygen, they release a large amount of heat quickly, raising the local temperature to 800–900 degrees Celsius, which can then cause the oxygen valve to burn.

2. Presence of Ignition Sources

The presence of an ignition source is a necessary condition for combustion accidents of oxygen valves. Without an ignition source, even if there are low ignition point combustible materials in the pipeline, the oxygen valve will not burn. Ignition sources may come from the following aspects:

Friction and Impact: When the valve is operated too quickly, the oxygen flow rate in the pipeline can cause solid particles to collide and rub against each other. The higher the flow rate, the more heat is generated by friction. When the heat reaches the ignition point of low ignition point materials, combustion will be triggered.

Adiabatic Compression Temperature Rise: When a valve is opened quickly, adiabatic compression temperature rise can occur. Theoretical calculations show that this temperature rise can reach 300–500 degrees Celsius. At this time, low ignition point materials such as rust and welding slag can be easily ignited.

Static Electricity Discharge: When a valve is opened quickly, the oxygen flow rate at the valve outlet may reach the speed of sound, generating static electricity of 6000–7000 volts. When the potential difference reaches more than 2000 volts, spark discharge will occur, which can then ignite low ignition point materials.

Human Operational Errors: Human errors can lead to leaks, fires, and other situations. For example, operators may accidentally bring a fire source into the operating area or operate the valve incorrectly, causing oxygen to leak and come into contact with a fire source.

Selection and Installation of Oxygen Valves

Use Specialized Oxygen Valves: Valves for oxygen pipelines should be specialized oxygen valves. These valves are specially designed and treated to effectively reduce the risk of combustion and explosion.

Avoid Using Gate Valves: Valves with a working pressure greater than 0.1MPa must not use gate valves. The gate slide slot is prone to accumulating rust, which can lead to poor closure. When operating the valve, squeezing the rust in the slide slot can easily create an ignition source, causing a combustion or explosion accident.

Choose Suitable Valve Types: For manual oxygen valves with a nominal pressure greater than or equal to 1.0MPa and a nominal diameter greater than or equal to 150mm, it is advisable to select valves with a bypass. For frequently operated oxygen valves, it is recommended to use pneumatic remote control valves to reduce the risk of human operational errors.

Design and Maintenance of Oxygen Pipelines

Install Flame Arrestor Copper Sections: At key locations in the oxygen pipeline, such as after the boundary valve of the oxygen plant (station, workshop), after the valve of the main oxygen pipeline supplying a system, after the workshop inlet valve, before and after the pressure regulating valve group, flame arrestor copper sections should be installed. These sections can effectively prevent the spread of flames and reduce the risk of combustion accidents.

Use Suitable Pipeline Materials: When the oxygen pressure regulating valve group is set in an independent valve room or protective wall, the valve stem of the manual valve should extend outside the protective wall for operation. If no separate valve room or protective wall is set, within a range of 8 times the nominal diameter of the pressure regulating valve before and after the oxygen pressure regulating valve, copper alloy (excluding aluminum-containing copper alloy) or nickel-based alloy piping should be used. These materials have high resistance to combustion and corrosion, which can effectively enhance the safety of the pipeline.

Ensure Straight Pipe Section Length: For the outlet side of the pipeline of pressure regulating valve groups, main pipeline valves, branch pipeline valves supplying a system, and workshop inlet valves, it is advisable to have a straight pipe section with a length of no less than 5 times the pipe outer diameter and no less than 1.5 meters. This design can reduce sudden changes in oxygen flow rate and lower the risk of accidents caused by excessive flow rate.

Operation Standards and Safety Measures for Oxygen Valves

Regular Maintenance and Inspection: Pipelines (containers) that have been out of service for more than three months must be blown and tested with a target to be qualified before oxygen can be supplied. Pipelines (containers) that have been out of service for more than one year must also undergo pressure testing as required for new pressure pipelines (pressure vessels) before oxygen can be supplied. Regular maintenance and inspection can promptly identify and eliminate potential safety hazards.

Prohibit the Use of Non-Regulating Valves for Regulation: The design and structure of non-regulating valves are not suitable for flow regulation. If non-regulating valves are mistakenly used for flow regulation, it may lead to valve damage or operational errors, which can cause accidents.

Establish Pipeline Records: An oxygen pipeline record should be established and managed by oxygen professionals familiar with the pipeline process. Detailed records can help operators better understand the condition of the pipeline and promptly identify and address issues.

Qualifications and Training of Operators: Oxygen pipeline operators should be certified and regularly receive safety training. Only operators with professional knowledge and skills can correctly operate oxygen valves and avoid accidents caused by operational errors.

Precautions During Oxygen Valve Operation

Cut Off the Gas Source: When an oxygen pipeline or valve catches fire, the gas source should be immediately cut off. This is a key measure to control the spread of the fire.

Use Suitable Tools: When operating oxygen valves, copper "F" wrenches should be used, and it is strictly forbidden to strike oxygen valves with iron tools. Copper tools can effectively prevent sparks from collisions between tools and valves.

Correct Operating Posture: Personnel operating oxygen valves must stand to the side of the valve and are strictly forbidden to stand on the oxygen pipeline. Non-operators are not allowed to watch. The correct operating posture can reduce the risk of operators being injured.

Wear Protective Equipment: Oxygen valve operators must wear protective gear and eliminate body static electricity before operating. Tools, work clothes, gloves, and other items used must not be contaminated with oil, and it is not advisable to wear synthetic fiber clothing. These measures can effectively reduce the risk of fires caused by static electricity and oil.

Handling Leaking Valves: When operating a leaking oxygen valve, personnel must wear fire-resistant suits and masks, and are not allowed to wear synthetic fiber clothing or shoes with nails. The environment must be ventilated and tested before operation. If the oxygen content in the operating area still exceeds 23%, personnel are strictly forbidden to operate. The gas source must be cut off first.

Maintenance and Emergency Handling: When repairing a faulty oxygen pressure regulating valve, the gas source must be cut off before maintenance operations. Emergency handling can only involve closing the valve, and it is strictly forbidden to increase the valve opening to avoid the generation of high-speed airflow.

Pressure Relief Operation: When relieving pressure from a pipeline (container), it is necessary to confirm that the inlet valve is closed before gradually opening the vent valve and paying attention to the frosting condition of the vent pipe. The pressure inside the pipeline (container) should be slowly reduced (pressure drop rate of 0.3–0.4MPa/h) to prevent combustion accidents and the formation of cracks.

Discharge Operation: When operating all oxygen discharge valves, it is strictly forbidden to aim them at personnel, fire sources, etc., and they must not be discharged into low-lying areas or poorly ventilated places. If an oxygen discharge valve is open for a long time, personnel should be assigned to guard the area, and the oxygen content in the surrounding environment should be tested and recorded every half hour.

Gas Supply Operation: When supplying oxygen to the oxygen pipeline network (storage tanks, pressure regulating stations, etc.), first, try to maximize the volume of the receiving unit and strictly follow the order of valve opening to prevent adiabatic compression temperature rise combustion and explosion accidents. Second, close the end exhaust valve to prevent accidents caused by excessive charging flow rate. If the entire pipeline network is shut down, it is advisable to use an oxygen compressor to synchronize the pressure increase with the pipeline network for startup. Pipeline (container) replacement should be carried out when the pressure reaches 0.1–0.3MPa. It is not advisable to open the exhaust valve for replacement at high pressure, and it is strictly forbidden to open the exhaust valve while charging to prevent excessive flow rate.

Conclusion

The safe operation of oxygen valves is an important aspect that cannot be ignored in industrial production. By understanding the causes of oxygen valve combustion accidents, taking scientific and reasonable preventive measures, and strictly adhering to operating standards, the probability of combustion and explosion accidents can be effectively reduced. It is hoped that the introduction in this article will help relevant operators better master the knowledge of safe oxygen valve operation and ensure the safety and smooth progress of the production process.