In the daily operation of hospitals, liquid oxygen (LOX) tanks play a crucial role. They provide a stable supply of oxygen for various medical equipment, ensuring patients' treatment needs are met. However, the installation and use of LOX tanks involve numerous safety requirements and operational standards, and any negligence at any stage may trigger serious safety incidents. Therefore, understanding and strictly following the installation and usage requirements of LOX tanks is essential for hospital safety management.
As an important oxygen supply device in hospitals, the installation of a LOX tank is the foundation for ensuring safe and stable subsequent use. Only by strictly following the specification requirements during installation can potential safety hazards be prevented from the source, ensuring normal hospital operations and patient safety. Next, we will take a detailed look at the installation requirements for LOX tanks.
The installation site for a LOX tank must have good ventilation conditions. Generally, LOX tanks should be installed outdoors, which can effectively prevent oxygen accumulation indoors in the event of a leak, avoiding danger. At the same time, fences should be set around the tank to provide isolation and protection. Within a 5-meter radius of the tank, open flames, flammable or explosive materials, and low-lying areas are strictly prohibited. Low-lying areas easily accumulate water, which, when in contact with liquid oxygen, may trigger violent reactions and cause dangerous situations.
LOX tanks must be equipped with static-dissipating grounding devices and lightning protection. This is because liquid oxygen can easily generate static electricity during storage and transport, and the accumulation of static can cause sparks, igniting surrounding combustible materials. The anti-static grounding resistance should not exceed 10Ω to ensure that static electricity can be dissipated in time. At the same time, the maximum impact resistance of the lightning protection device is 30Ω, and it must be tested at least once a year to ensure its effectiveness. During thunderstorms, the lightning protection device can effectively prevent lightning from striking the tank directly, avoiding fire or other accidents caused by lightning.
The filling rate of the LOX tank must not exceed 95%, and overfilling is strictly prohibited. This is because liquid oxygen expands in volume during storage due to temperature changes, and overfilling may cause excessive internal pressure in the tank, leading to explosions or other hazards. In addition, the pressure gauge on the tank must be oil-free and regularly calibrated to ensure accuracy. The safety valve is an important safety device of the tank and must be made of stainless steel or copper, regularly calibrated, and strictly degreased. When valves, instruments, or pipelines freeze, open flames must not be used for thawing; instead, 70–80°C nitrogen, air, or hot water should be used.
After ensuring that the LOX tank is properly installed, we next examine the usage requirements. Installation is only the first step; proper use and standardized operation procedures are key to ensuring the long-term safe operation of the LOX tank.
Personnel operating LOX tanks must receive professional training and pass examinations before taking the position. This is because operating LOX tanks involves numerous specialized knowledge and safety protocols, and only professionally trained personnel can master them proficiently, ensuring operational safety. During operation, personnel must not wear oil-contaminated or static-prone synthetic clothing, nor shoes with nails. This is because oil and static may generate sparks, creating danger. Valves must be opened and closed slowly, and when not in use, pressure-increasing valves must be tightly closed.
When liquid oxygen is stored in the tank in a sealed manner, pressure must be monitored, and overpressure must be avoided. This is because liquid oxygen expands during storage due to temperature changes, which may increase pressure. Excessive pressure may lead to explosions or other hazards. Liquid oxygen must not come into contact with unprotected skin to prevent severe frostbite. When the tank has been emptied and cannot be immediately heated, all valves must be closed. This is because the tank is extremely cold, and moist air entering through connected pipelines can cause ice blockages in the pipes.
Before installation, LOX tank safety valves should be regularly calibrated by professionals according to working conditions, at least once a year. The set pressure of the safety valve is generally 1.05–1.10 times the maximum working pressure of the vessel and must not exceed the design pressure. Safety valves should be installed vertically and positioned in the gas phase above the liquid level of the pressure vessel, or connected to pipelines linked to the gas phase of the LOX tank. The internal cross-sectional area of connecting pipes and fittings between the pressure vessel and the safety valve must not be smaller than the inlet area of the safety valve. Intermediate shut-off valves between the LOX tank and the safety valve are generally not recommended. For pressure vessels containing flammable, extremely, highly, or moderately toxic, or viscous media, shut-off valves may be installed between the LOX tank and safety valve to facilitate replacement or cleaning of the safety valve, but the structure and diameter of the shut-off valve must not interfere with the normal release of the safety valve. During normal operation, shut-off valves must remain fully open and be sealed with lead.
After understanding the installation and usage requirements, we now focus on the filling process. Filling is a critical stage in the use of LOX tanks, and whether it is done correctly directly affects storage safety and supply stability.
Before filling, ensure that the pressure gauge and liquid level indicator of the LOX tank are functioning normally. Also, ensure that tank valves and pipe joints are intact and leak-free. These checks can effectively prevent liquid oxygen leaks and other hazards during filling. Once everything is confirmed normal, connect the hose, open the tanker discharge valve and the tank's pressure-increasing valve, and start filling through the top inlet pipe. The top inlet should be opened slowly to pre-cool the pipeline and inner cylinder. Once pressure stabilizes, the top inlet valve can be fully opened.
When the liquid in the tank reaches a certain level, close the top inlet valve and pressure-increasing valve. Open the bottom inlet valve to continue filling through the bottom inlet pipe. Note that top and bottom filling must never occur simultaneously. When the liquid level indicator is near the full mark, open the full-indicator valve. When liquid overflows from the full-indicator valve, immediately close the tanker discharge valve, the bottom inlet valve, and the full-indicator valve. At this point, the LOX tank is fully filled. Note that filling is based on the full-indicator valve; the liquid level indicator is highly sensitive and may not be accurate, serving only as a reference.
After filling, open the residual liquid exhaust valve to vent, close the tanker discharge valve, disconnect the filling hose, seal the filling port, and open the pressure-increasing valve to ensure the tank pressure is above 0.5 MPa. Check the liquid level indicator to confirm the liquid level. During the entire filling process, operators must strictly follow operating procedures to ensure safety.
Understanding and constantly remembering the following safety precautions is indispensable for ensuring the safe operation of hospital LOX tanks, protecting personnel, and avoiding property damage.
Liquid oxygen is nonflammable but strongly supports combustion, with a fire hazard rating of Class B. Contact with fuels usually does not cause spontaneous ignition, but if two liquids meet, liquid oxygen will cool and solidify the fuel. Mixtures of solidified fuel and liquid oxygen are impact-sensitive and may explode under pressure. Therefore, flammable and explosive materials are strictly prohibited near LOX tanks, and contact between LOX and fuel must be avoided.
After passing safety inspection, tank trucks should follow the designated route and enter the filling station at low speed. Engines must be turned off, handbrakes applied, and anti-slip blocks added if there is a risk of sliding. Before filling, surrounding roads should be closed and warning signs posted, prohibiting any vehicle traffic to prevent explosion hazards. No flammable or explosive materials should be present at the filling site or in the tanker. When connecting tail gas recovery devices, residual gas in the tank should be recovered; if not recoverable, high-altitude venting must be used to avoid oxygen toxicity.
During LOX tank operation, emergencies such as leaks or fires may occur. Hospitals must develop complete emergency response plans and conduct regular drills. In the event of an emergency, operators must be able to respond quickly and effectively to minimize losses.
The installation and use of LOX tanks is a complex and critical task, involving numerous safety requirements and operational standards. Hospitals must strictly follow the relevant requirements to ensure operational safety. By selecting appropriate installation sites, equipping grounding and lightning protection devices, strictly controlling filling levels, standardizing operation procedures, and conducting regular maintenance and inspections, hospitals can effectively ensure the safe operation of LOX tanks and provide a stable oxygen supply for medical work. In addition, hospitals should strengthen training and management of operators to improve safety awareness and operational skills, ensuring the safe use of LOX tanks.
