LPG tank truck loading and unloading operations

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Operation of loading and unloading LPG tank trucks I. Preparation work 1. Guide the tank truck to stop at the loading/unloading platform; once the driver has applied the handbrake and turned off the engine, place anti-slip pads under the driver’s feet. 2. Check the liquefied petroleum gas inspection form, as well as the liquid level, pressure, and temperature of the tank truck and the receiving storage tanks; also check for any leaks at the loading/unloading valves and flange connections. 3. Connect the static electricity grounding wire, remove the quick-connect fitting cover, and after firmly attaching the high-pressure gas and liquid hoses of the loading/unloading platform to the corresponding gas and liquid pipes of the tank truck, open the release valve to expel the air from the high-pressure hoses using the liquefied petroleum gas available at the gas station, then close the release valve. 4. Use a manual hydraulic pump to open the emergency shut-off valve of the tank truck; once an opening sound is heard, slowly open the ball valve. II. Normal loading and unloading procedures 1. Loading and unloading operations for liquefied petroleum gas compressors ① Gas phase system: Open the valve connecting the gas phase outlet of the receiving tank to the compressor inlet pipeline ； Open the vapor line valve of the tank truck with compressor export controls. ②Liquid phase system: Open the liquid phase pipe of the transfer tank truck to the inlet valve of the receiving storage tank. 　③Notify the operator to start the compressor. ④Once the gas phase pressure in the tank truck is 0.2Mpa to 0.3Mpa higher than that in the receiving tank, the liquid flows from the tank truck to the receiving tank. When the liquid level in the tank truck approaches zero, the compressor operator should promptly shut down the compressor, close the valve connecting the liquid phase pipe of the tank truck to the inlet pipe of the receiving tank, close the valve connecting the gas phase outlet pipe of the receiving tank to the compressor inlet pipe, and close the valve connecting the compressor outlet pipe to the gas phase pipe of the tank truck. ⑤Open the valve connecting the gas outlet pipe of the tank truck to the compressor inlet pipeline, and open the valve connecting the compressor outlet to the gas inlet pipe of the receiving storage tank. Inform the operator to start the compressor to recover the gas from the tank truck; stop the operation when the pressure in the tank truck reaches 0.2 Mpa, and then close the aforementioned valves. ⑥Close the tank truck’s emergency shut-off valve. After releasing pressure, remove the high-pressure hose and static grounding wire, cover the quick connector, and take out the anti-slip fastener. The tank truck has been driven away; the unloading operation is complete. ⑦Fill out the operation record form as required. 2. LPG compressor loading operation ①Gas phase system: Open the valve connecting the gas phase pipeline of the tank truck to the compressor inlet pipeline; open the valve connecting the compressor outlet pipeline to the gas phase inlet pipeline of the liquid storage tank. ②Liquid phase system: Open the valve of the liquid phase pipeline from the tank truck to the outlet pipeline of the storage tank. ③Notify the operator to start the compressor. ④Once the gas phase pressure in the liquid discharge storage tank is 0.2Mpa to 0.3Mpa higher than that in the tank truck, the liquid flows from the storage tank to the tank truck. When the liquid level in the tank truck reaches the maximum allowable filling level, the compressor operator should be instructed to stop operating immediately, and the liquid phase valve of the tank truck as well as the outlet valve of the liquid storage tank should be closed. ⑤Close the valve from the gas phase of the tank truck to the compressor inlet pipe, and close the valve from the compressor outlet pipe to the gas phase inlet line of the liquid storage tank. Close the tank truck’s emergency shut-off valve. After releasing pressure, remove the high-pressure hose and static grounding wire, cover the quick connector, and take out the anti-slip fastener. The tank truck has been driven away; the loading operation is complete. ⑥Fill out the operation record form as required. 3. LPG hydrocarbon pump unloading operation ① Gas phase system: Open the valve from the gas phase valve of the tank truck to the gas phase pipeline of the receiving storage tank. ②Liquid phase system: Open the valve on the tank truck’s liquid phase line leading to the hydrocarbon pump inlet pipeline ； Open the valve connecting the hydrocarbon pump outlet to the inlet pipeline of the receiving tank. ③Notify the operator to start the hydrocarbon pump. ④The liquid level flows out of the tank truck, is pressurized by the hydrocarbon pump, and then moves toward the receiving tank. When the liquid level in the tank truck is close to zero, the operator is instructed to stop the hydrocarbon pump, close the vapor valve of the tank truck as well as the valve in the vapor line leading to the receiving tank, close the liquid valve of the tank truck at the inlet of the hydrocarbon pump, and close the inlet valve that connects the outlet of the hydrocarbon pump to the receiving tank. Close the tank truck’s emergency shut-off valve, relieve pressure, then remove the high-pressure hose and static grounding wire, cover the quick-connect fitting, and take out the anti-slip block. The tank truck has been driven away; the unloading operation is complete. ⑤Fill out the operation record form as required. 4. LPG hydrocarbon pump loading operation: ① Gas phase system: Open the valve connecting the gas phase pipeline of the tank truck to the compressor inlet pipeline; open the valve connecting the compressor outlet pipeline to the gas phase inlet pipeline of the liquid storage tank. ②Liquid phase system: Open the valve of the liquid phase pipeline from the tank truck to the outlet pipeline of the storage tank. ③Notify the operator to start the compressor. ④Once the gas phase pressure in the liquid discharge storage tank is 0.2Mpa to 0.3Mpa higher than that in the tank truck, the liquid flows from the storage tank to the tank truck. When the liquid level in the tank truck reaches the maximum allowable filling level, the compressor operator should be instructed to stop operating immediately, and the liquid phase valve of the tank truck as well as the outlet valve of the liquid storage tank should be closed. ⑤Close the valve from the gas phase of the tank truck to the compressor inlet pipe, and close the valve from the compressor outlet pipe to the gas phase inlet line of the liquid storage tank. Close the tank truck’s emergency shut-off valve. After releasing pressure, remove the high-pressure hose and static grounding wire, cover the quick connector, and take out the anti-slip fastener. The tank truck has been driven away; the loading operation is complete. ⑥Fill out the operation record form as required. 3. LPG hydrocarbon pump unloading operation ① Gas phase system: Open the valve from the gas phase valve of the tank truck to the gas phase pipeline of the liquid storage tank. ②Liquid phase system: Open the valve connecting the liquid phase outlet of the liquid discharge tank to the inlet pipeline of the hydrocarbon pump ； Open the valve for the liquid-phase pipeline from the hydrocarbon pump outlet to the receiving tank truck. ③Notify the operator to start the hydrocarbon pump. ④The liquid level rises as the liquid flows out of the storage tank, is pressurized by the hydrocarbon pump, and then moves toward the tank truck. When the liquid level in the tank truck reaches the maximum allowable filling level, the operator is instructed to stop the hydrocarbon pump, close the valve connecting the gas phase of the tank truck to the gas phase pipeline of the storage tank, close the valve at the liquid phase outlet of the storage tank that leads to the inlet pipe of the hydrocarbon pump, and close the valve at the outlet of the hydrocarbon pump that leads to the inlet pipe of the tank truck. Close the tank truck’s emergency shut-off valve, relieve pressure, then remove the high-pressure hose and static grounding wire, cover the quick-connect fitting, and take out the anti-slip block. The tank truck has been driven away; the unloading operation is complete. ⑤Fill out the operation record form as required. III. Patrol inspections: 1. Check whether the flow direction of the liquid during unloading and loading operations is correct. 2. Check whether there are any abnormalities in the pressure, liquid level, and temperature of the tank truck and storage tanks. 3. Check the compressor’s gas-liquid separator; there should be no liquid present, or the liquid level should be below the safe level. V. Precautions 1. Check the liquid level in the gas-liquid separator it is connected to; if there is liquid present, it should be drained promptly. 2. During the loading and unloading process of tank trucks, the operators must be present to carry out these tasks, while also paying attention to the stability of the pumps and checking for any abnormalities such as leaks in the pipelines. 3. It is not allowed to start the vehicle or sound the horn while working on it or when releasing pressure from the high-pressure hose. 4. Operators must wear gloves while working. When installing or removing high-pressure hoses, it is necessary to close the valves and release pressure, and the hose ends must not be directed at people to prevent frostbite from liquefied petroleum gas. 5. In case of thunderstorms, the presence of open flames or fires in the vicinity, abnormal unloading pressure, a large pressure difference with no liquid flow or a decrease in the liquid level, failures in the equipment or high-pressure hoses, or malfunctions of safety accessories, unloading operations must be stopped immediately. 6. The residual pressure after unloading from the tank truck should be below 0.1 Mpa, and the amount of liquid remaining in the tank should be at least 5% of the maximum filling capacity. 7. Before returning the key to the driver so that he can drive away from the loading/unloading platform, it is necessary to ensure that the valves in the tank truck’s loading/unloading control panel are closed, and that all connections to the tank truck have been completely disconnected. VI. Emergency shutdown procedure for abnormal situations 1. Upon detecting an abnormal situation, loading and unloading operations must be stopped immediately. 2. The emergency cut-off valves for the gas and liquid phases of the tank truck, as well as the relevant valves at the gas station, must be shut off immediately, and the power supply must be disconnected. 3. In the event of a large-scale leak of liquefied petroleum gas, immediately call the police or dial 119, and cut off all sources of fire and heat. 4. In the event of a fire caused by a leak of liquefied petroleum gas, and while ensuring the safety of personnel, efforts should be made to cut off the supply of liquefied petroleum gas. Fire extinguishers should be used to put out the fire, and water from fire trucks should be used to cool down the tank trucks or storage tanks, in order to prevent the accident from spreading further.