LPG Trailer Unloading: Key Points for Safe Operation

1. Pre - unloading Preparations

Park the LPG trailer on a flat surface. Engage the parking brake and use wheel chocks to secure the wheels to prevent it from sliding. Ensure that the area around the trailer is at least 50 meters away from any sources of fire, static electricity, and open flames.

The operator should wear protective clothing, gloves, and goggles. Then, check the tank's pressure gauge, safety valve, and pipeline connections to ensure they are in good condition. Confirm that the design pressure of the receiving storage tank matches that of the trailer's tank to prevent over - pressure. It is essential to connect the static - conductive device to eliminate the risk of static electricity accumulation during the unloading process.

2. Unloading Methods and Operating Procedures

(1) Unloading by Pressure Difference (Self - pressure Unloading)

This method is applicable when the pressure inside the tank is above 0.7 - 1.2 MPa. First, connect the liquid outlet of the trailer to the liquid inlet of the receiving storage tank using a metal hose. If it is necessary to balance the gas - phase pressure, an additional gas - phase pipe should be connected (from the gas - phase port of the receiving tank to the gas - phase port of the trailer).

Open the gas - phase valve of the trailer to balance the pressure between the receiving tank and the trailer. Then, slowly open the liquid outlet valve to use the tank's own pressure to pump the LPG into the receiving tank. During the unloading process, closely monitor the pressure gauge and the liquid level gauge. Control the valve opening to adjust the flow rate and prevent pipeline vibration or leakage. When the liquid level is nearly empty, close the liquid outlet valve first and then the gas - phase valve.

(2) Unloading by Pump (Powered Unloading)

If the pressure inside the tank is insufficient, a centrifugal pump or a submerged pump can be used. Install an explosion - proof pump on the liquid outlet pipeline and ensure that the inlet and outlet directions of the pump are correct.

Before starting the pump, exhaust the air to fill the pump with liquid. After starting the pump, slowly open the valve to transport the LPG to the receiving tank. Adjust the flow rate through the valve and the pump frequency to avoid cavitation or over - pressure.

(3) Unloading by Compressor (Gas - phase Recovery)

This method is used when the pressure inside the tank is low and gas - phase recovery is required. Connect the inlet of the compressor to the gas - phase port of the receiving tank and the outlet to the gas - phase port of the trailer. Start the compressor to pump the gaseous LPG from the receiving tank into the trailer's tank to increase the trailer's pressure. Once the pressure is sufficient, follow the pressure - difference unloading method and repeat the cycle until the unloading is completed.

3. Post - unloading Operations

Close all valves and slowly release the residual LPG in the hose through the pressure - relief valve. Then, remove the hose and cover the connection ports with dust caps. Use a leak detector or soapy water to check if there are any leaks at the valves and connections. Finally, record the unloading volume, time, operator, and equipment status.

4. Safety Precautions and Problem Handling

No smoking or open flames are allowed within the operation area. Continuously monitor the pressure to prevent it from exceeding the tank's design pressure. The site should be equipped with dry - powder fire extinguishers, emergency cut - off valves, and an evacuation plan. Only licensed personnel are allowed to operate according to local regulations and the manufacturer's manual.

If the pressure is insufficient, switch to pump - assisted or compressor - assisted unloading. If the pipeline freezes due to the endothermic vaporization of LPG, use warm water to melt the ice blockage; open flames are prohibited. In case of a leak, immediately close the valves, evacuate the personnel, and initiate the emergency response.

Safety is always the top priority in the unloading operation. For more detailed information, refer to the vehicle's operation manual or consult a professional technician.