LNG cryogenic tank operation process specification

The cryogenic storage tank is filled with vacuum-filled pearl sand as a cold-preserving material to ensure the micro-positive pressure of the interlayer, and the insulating material is isolated from the atmosphere, avoiding the influence of atmospheric pressure or temperature change, and the humid air entering the inner and outer tank cold-keeping layers, and adding the cold-preserving material. The service life guarantees and improves the use of cold insulation materials.

LNG cryogenic tank operation procedures

1.1 Field station pressure regulation process introduction

Attach a partial process flow chart of the pressure regulation area, and number the equipment to be operated in the process flow chart.

1.2 Work preparation before pressure regulation

1.2.1 Preparation of tools

Two sets of explosion-proof adjustable wrenches and gloves and two sets of protective equipment.

1.2.2 Preparation for work

(1) Wear protective equipment, including anti-static clothing, static shoes, helmets, etc.;

(2) Check whether mobile phones, computers, etc. are likely to cause static equipment to be placed in a safe area, check whether the environment around the operation is safe, and whether the operating conditions are met;

(3) Both hands touch the electrostatic touch release facility before entering the station to release static electricity;

(4) Check whether the pressure regulating tools such as explosion-proof wrenches are fully loaded;

(5) Check that the pressure gauge, level gauge, thermometer, flammable gas detector and safety valve of the tank are in normal working condition.

(6) Check if the pipeline valve, pressure gauge and safety valve are in normal working condition.

(7) Prepare the explosion-proof tools used

1.2.3 LNG storage tank gas supply process:

1. Confirm that all valves of the tank to be supplied with air are closed except for the tank root valve and the emergency shut-off valve.

2. Open the lower inlet valve and the pressurized liquid phase and gas phase valve of the low temperature storage tank, and check that the valves before and after the pressurized gasifier are open.

3. Open the front low temperature shut-off valve of the gasifier to be supplied with gas, all the valves that need to be opened after the gasifier and the normal temperature flange ball valve and pressure regulating system.

4.A. When the gas supply amount is <1000-2000Nm3/h, the supply of one tank can be used to meet the gas supply requirements;

5. Liquid:

5.1 When the tank pressure rises above the outlet pressure by 0.15MPa, slowly open the outlet valve to complete the gas supply.

5.2 Record the fluid tank number and start the gas supply time.

5.3 Pay attention to the liquid level, pressure change and the change of outflow flow and pressure in the tank.

1.2.4 Self-pressurization operation procedure for LNG storage tanks

1. When operating manually, open the valve: pressurized liquid phase valve, pressurized gas phase bypass valve, gasifier inlet valve, so that LNG directly enters the self-pressurized gasifier, passes through gasification and enters the LNG storage tank. At this point, the pressure should be closely observed and the pressurized liquid phase valve valve is closed when the LNG tank pressure reaches the desired value.

2, note:

(1) When the LNG cryogenic storage tank is operated, it must ensure that the liquid level high limit is ≤90% and the low limit liquid level is ≥15%.

(2) When manually operating from the booster system, it is strictly forbidden to leave the scene.

(3) The decompression system should be in the closed state when the booster system is put into operation.

3, note:

(1) When operating LNG storage tanks, the liquid level must be ≥15%.

(2) When operating manually, it is strictly forbidden to leave the scene.

1.2.5 Risk Analysis and Countermeasures

1) When loading and unloading LNG tank trucks, operators should wear masks, anti-static overalls and antifreeze gloves.

2) When the LNG tanker unloads the vehicle, it is strictly forbidden to move the vehicle to avoid breaking the loading and unloading hose and causing a large amount of LNG leakage.

3) When there is LNG in the pipeline, the valves at both ends cannot be closed at the same time.

4) It is strictly forbidden to touch and step on the low temperature pipelines and facilities.

6) Under no circumstances should moisture, oil, mechanical impurities, etc. enter the pipeline to avoid clogging the pipeline.

7) It is strictly forbidden to beat, bake with fire and spray frozen parts with water.

8) In order to ensure the safety of the working environment, the operator should wear the labor insurance products. Before entering the station, the static electricity of the human body should be eliminated. The open fire is strictly prohibited in the working area of the station. Non-explosion-proof tools and electronic equipment are strictly prohibited.

9) Strictly implement the operating ticket system and follow the steps of the operation ticket. The on-site operator requires at least 2 people, one person to operate, one person to guard, to ensure safe operation.

10) Conduct safety education before operation, implement on-site safety precautions, know how to escape and how to control dangers in case of danger.

1.2.6 LNG cryogenic storage tank maintenance procedures

1. LNG station operation technicians must be familiar with the structure and principle of the tank, and carry out liquefied natural gas related operations in strict accordance with the operating procedures.

2. LNG operation technicians must be familiar with the performance and principle of tank accessories (pressure gauges, level gauges, thermometers, vacuum test valves).

3. The outer cylinder of the liquefied natural gas storage tank is an external pressure vacuum vessel, and welding operations under negative pressure are strictly prohibited.

4. Regularly inspect the outer cylinder of the tank to observe the phenomenon of ice formation and frost formation. When it is found that there is icing and frosting, it is necessary to report the squad leader and the stationmaster in time. The squad leader or the stationmaster immediately contacted the manufacturer to find out the reason for immediate treatment. Pay close attention to the changes of icing and frosting during the treatment process. If the accident has an expanding trend, the tank should be refilled or stopped immediately, and the relevant inlet and outlet emergency shut-off valves should be closed.

5. Regularly check the connecting pipes and valves of the storage tanks, observe the frosting phenomenon, and report the problems to the duty monitor in time. When the shift monitor arranges the personnel according to the situation.

6. Regularly check the pressure gauge, level gauge and thermometer of the tank to see if the displayed value is normal.

7. Regularly check the sealing performance and switching action of the connected valve to ensure normal operation.

8. Regularly check the safety valve, pressure gauge, liquid level gauge and thermometer according to the regulations to ensure normal operation and update the contents of the equipment account in a timely manner.

9. Regularly carry out anti-corrosion on the outer cylinder of the storage tank and clean and maintain the pressure gauge, liquid level gauge and thermometer of the storage tank.

10. Regularly carry out rust removal and corrosion prevention on the rust parts such as the pressure of the storage tank and the control of the liquid level control instrument.

11. Check the vacuum degree of the tank every year or according to the operation conditions, and master the working condition of the tank.