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Safety regulations for use of liquid nitrogen tank

Time: 2020-09-22 10:41 Source: unknown Author: Bander liquid nitrogen tank Click: second
1. Purpose

This procedure is mainly used to guide operators how to use liquid nitrogen safely and correctly.

2. Overview of liquid nitrogen: liquid nitrogen tank

2.1 legal name

Chemical name: liquid nitrogen

2.2 risk overview

Health hazards: This product is non combustible and asphyxiating. It can cause frostbite if skin contact with liquid nitrogen. If excessive nitrogen is produced by vaporization at room temperature, the partial pressure of oxygen in the air will be decreased, resulting in anoxic asphyxia.

2.3 first aid measures

Skin contact: in case of frostbite, seek medical treatment. Inhalation: leave the site quickly and keep breathing unobstructed. If you have difficulty breathing, give oxygen. If breathing stops, give artificial respiration immediately and seek medical advice.

2.4 fire fighting measures

Risk: in case of heat, the internal pressure of the container will increase, and there will be the risk of cracking and explosion.

Fire extinguishing method: the product is non combustible, and the container in the fire site is kept cool with mist water. Liquid nitrogen evaporation can be accelerated by spray of mist water, and liquid nitrogen can not be shot by water gun.

2.5 emergency treatment of leakage

Emergency treatment: quickly evacuate the personnel from the contaminated area to the windward place, isolate and restrict the access. Emergency personnel should wear self-contained positive pressure breathing apparatus and cold proof clothing. Do not come into direct contact with the leakage. Cut off the source of the leak as much as possible. Prevent the gas from gathering in the low concave and exploding when meeting the point heat source. Use exhaust fan to send the leakage gas to the open place. Leaking containers should be properly treated, repaired and inspected before use.

2.6 handling and storage

Operation precautions: close operation, provide good natural ventilation conditions. Operators must be trained and strictly abide by the operation rules. It is recommended that operators wear cold proof gloves. Prevent gas leakage into the workplace air. Handle with care to prevent damage to cylinder and accessories. Equipped with leakage emergency equipment.

Storage precautions: store in a cool and airy place, and the temperature should not exceed 50 ℃

2.7 personal protection

Respiratory system protection: generally no special protection is required. However, when the oxygen concentration in the workplace is lower than 19%, air respirator, oxygen respirator and long tube mask must be worn. Eye protection: wear safety mask. Hand protection: wear cold proof gloves. Other protection: avoid high concentration inhalation, prevent frostbite.

2.8 physical and chemical properties

99.99% high purity nitrogen.

Appearance and character: compressed liquid, no smell. Melting point: - 209.8 ℃. Boiling point: - 195.6 ℃

Relative density (water = 1): 0.81 (- 195.6 ℃). Relative vapor density (air = 1): 0.97

Saturated vapor pressure (kPa): 1026.4 (- 173 ℃). Near temperature: - 147 ℃, near pressure: 3.40mpa

Solubility: slightly soluble in water and ethanol.

2.9 regulatory information liquid nitrogen tank

Regulation information: Regulations on the safety management of hazardous chemicals (promulgated by the State Council on February 17, 1987), detailed rules for the implementation of safety management of hazardous chemicals (HLF [1992] No. 67), regulations on the safe use of chemicals in workplaces (LBF No. 423 in 1996) have made corresponding regulations on the safe use, production, storage, transportation and handling of hazardous chemicals Conclusion: the classification and labeling of commonly used hazardous chemicals (GB 13690-92) classifies the substance as category 2.2 non combustible goods.

3. Operation procedures

3.1 storage operation

3.1.1 check that the pressurization inlet valve (hcv-3), liquid level gauge stop valve (hcv-8, hcv-10), pressurization stop valve (hvc-11) and throttle line stop valve (hcv-14) should be opened, and other valves should be closed for automatic pressure supplement.

3.1.2 patrol inspection once every hour liquid nitrogen tank Check the pressure gauge (P1-1), control the pressure at 0.35 ~ 0.6MPa and record it. When the pressure exceeds 0.6MPa, open the exhaust valve (hcv-12) to relieve the pressure to 0.45MPa.

3.1.3 check and record the liquid level gauge of liquid nitrogen tank every hour. When the liquid level is lower than 100 cm water column, it is necessary to contact to add liquid nitrogen.

3.2 normal operation

3.2.1 after being informed of the use of liquid nitrogen, check that the relief valve of the feed pipe should be closed, and open product use valve 1 (hcv-13) and product use valve 2

3.2.2 however, pay close attention to control the pressure gauge between 0.35 and 0.6MPa during its use.

3.2.3 when the post stops using, first close the service valve 1 and open the relief valve of the feed pipe to drain the liquid nitrogen in the feed pipe, and then close the service valve 2 and close the pressure relief valve.

4. Precautions

4.1 in case of a large amount of gas mist or liquid nitrogen splashing and flowing on the operation site, evacuate the site immediately and close the valve in the leakage area to cut off the leakage source. Pay attention to safety protection.

4.2 if liquid nitrogen operation is involved, it is necessary to wear safety protective mask to protect face and eyes, cold proof and penetration proof gloves to protect hands. Tooling must be fully worn and suitable without exposed parts.

4.3 when the liquid nitrogen valve is opened and closed, it must stand at a relatively open position in the upwind direction of the possible leakage point or leakage direction side.

4.4 before, during and after the use of liquid nitrogen, keep in touch with the post using liquid nitrogen downstream in the whole process, so as to deal with accidents in time.

5. Troubleshooting procedures

5.1 if the pressure is too high, open the exhaust valve (hcv-12) to depressurize.

5.2 when the safety valve of the storage tank jumps due to too high pressure, first open the vent valve, relieve the pressure to 0.45MPa, reduce the pressure of the tank, and then switch the three-way valve to the standby safety valve, pay close attention to the pressure change in the storage tank. Do not switch the three-way valve to the standby safety valve when the safety valve jumps but there is no pressure relief, otherwise the standby safety valve will jump.

5.3 in case of leakage, measures must be taken to cut off the upstream valve and inform the relevant departments if the protection is appropriate.

6. Operation parameters

6.1 the liquid nitrogen delivery pressure is not less than 0.35Mpa and not higher than 0.6MPa.

6.2 the liquid volume shall not be less than 25% of the reserve, and the supplier shall be informed in time on duty. When the contact is difficult, the relevant department shall be informed to send liquid nitrogen.

7. Maintenance

7.1 inspectors are not allowed to move valves and pressure relief devices at will, and inform equipment management department in time when problems are found.

7.2 the equipment design and manufacturing department is responsible for the maintenance work.

8. Patrol inspection

8.1 inspection personnel must inspect the liquid nitrogen station once an hour and make records.

8.2 when filling liquid nitrogen, it must be monitored on site, and the charging pressure shall not affect the production.

8.3 do a good job in statistics and record the amount of liquid added.

8.4 after the liquid nitrogen storage liquid is full, the pressure change in the storage tank should be kept close within 24 hours. If the pressure fluctuates greatly, it should be discharged timely to keep the pressure normal.

Pay close attention to the liquid storage tank when reaching the lower limit of 8.

8.6 when the evaporator frosts, defrost in time. liquid nitrogen tank

9. Safety measures

9.1 operators must wear anti freezing equipment when opening valve pipe accessories.

9.2 for the unfreezing of equipment, pipelines and valves, only water can be used for flushing. Knocking, fire baking and electric heating are strictly prohibited.

9.3 if the liquid nitrogen storage tank leaks, please be careful of suffocation. (keep as far away as possible when emptying)

9.4 non staff members are not allowed to enter the liquid nitrogen area.

10. Environmental protection

Prevent leakage and save energy. liquid nitrogen tank

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