Operation Procedure for Low-Temperature Natural Gas Storage Vessel

1.1 Station Pressure Regulation Process Introduction

Attached is a partial process flow diagram of the pressure regulating area, with the equipment requiring operation numbered in the process flow diagram.

1.2 Pre-Pressure Regulation Preparation

1.2.1 Tool Preparation

Explosion-proof adjustable wrench, two pairs of gloves, and two sets of protective equipment.

1.2.2 Preparatory Work

Wear personal protective equipment, including anti-static suits, static-free shoes, safety helmets, etc.

(2) Ensure that devices prone to static electricity, such as smartphones and computers, are placed in a safe area. Check if the surrounding environment is secure and meets the operational requirements.

(3) Before entering, touch the static discharge equipment with both hands to release static electricity.

(4) Verify that all pressure-regulating tools, such as explosion-proof wrenches, are carried.

(5) Inspect that the tank's pressure gauge, level gauge, thermometer, flammable gas detector, and safety valve are all operating normally.

(6) Inspect the pipeline valves, pressure gauges, and safety valves to ensure they are in normal working condition.

(7) Prepare all explosion-proof tools

1.2.3 LNG Storage Tank Gas Supply Process:

All valves of the tanks to be pressurized are closed, except for the root valve and the emergency shutdown valve.

2. Open the low-temperature tank's bottom inlet valve and the liquid and gas phase boost valves, check that both valves on the front and rear of the boost gasifier are open.

3. Open the low-temperature cutoff valve for the gasifier, the normal temperature flanged ball valve after the gasifier, and all valves required to be opened in the pressure regulating system.

4.A. A single storage tank is sufficient to meet the gas supply requirements when the gas supply rate is less than 1000-2000 Nm3/h.

5. Liquid Output:

5.1 When the tank pressure rises above 0.15 MPa higher than the outlet pressure, slowly open the liquid outlet valve to commence the gas supply operation.

5.2 Record the liquid storage tank number and the start of gas supply.

5.3 Pay close attention to the liquid level, pressure changes, and the variations in flow and pressure at the exit of the storage tank during gas supply.

1.2.4 LNG Storage Vessel Self-Pressurization Operating Procedure

1. When manually operating, open the valves: the boost liquid phase valve, the boost gas phase bypass valve, and the vaporizer inlet valve to allow LNG to directly enter the self-boosting vaporizer. After vaporization, it enters the LNG storage tank. At this point, closely monitor the pressure, and close the boost liquid phase valve when the pressure in the LNG storage tank reaches the desired level.

2. Cautionary Notes:

(1) During operation, the LNG low-temperature storage tank must ensure the liquid level does not exceed 90% and does not fall below 15%.

(2) When manually operating the self-pressurizing system, unauthorized personnel must not leave the scene.

(3) When the self-pressurizing system is in operation, the pressure-reducing system should be in the off state.

3. Important Notes:

(1) During operation, the LNG tank must maintain a liquid level of ≥15%.

(2) When manually operating, the site must be strictly supervised at all times.

1.2.5 Risk Analysis and Countermeasures

During the loading and unloading of LNG tank trucks, operators should wear masks, anti-static work clothes, and frost-proof gloves, etc.

2) Absolutely no movement of the LNG tank truck is permitted during unloading to prevent breaking the loading/unloading hoses, which could lead to significant LNG leakage.

3) When LNG is present in the pipeline, the valves at both ends cannot be closed simultaneously.

4) No touching or stepping on low-temperature pipelines and facilities.

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

7) Absolutely no hammering, fire roasting, or water spraying on the frozen areas.

8) To ensure the safety of the working environment, operators must wear protective gear. Static electricity from the human body must be neutralized before entering the station. Open flames are strictly prohibited within the station's operational area, as well as the use of non-explosion-proof tools and electronic devices.

9) Strictly adhere to the operation ticket system, following the steps outlined in the operation ticket. The on-site operation requires at least two personnel: one to operate and one to supervise, ensuring operational safety.

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