What aspects should be given special attention to ensure safe and stable operation of the LNG tank internal pump during its first start-up?

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I. Checks before trial operation: 1. The pump and pipes must be completely dry, with a dew point below -40 degrees Celsius. 2. The pump and pipes must be thoroughly cooled; the pump inside the tank should remain at its operating temperature for at least 3 hours to achieve thermal equilibrium in all its components. 3. Check that the liquid level in the tank meets the startup conditions. 4. The settings of the instruments and relays are correct. 5. Check that the motor’s insulation is proper. II. Trial Operation 1. Use the JOGGING function to start the motor intermittently (the pump will stop when it reaches the rated speed or after 3 seconds); listen for any abnormal noises or vibrations. 2. Before restarting, the pump needs to be cooled; follow the equipment instructions. 3. Start the pump under operating conditions, and monitor data such as pump pressure/vibration/current.

Important steps for operating a cryopump: 1. Before starting up, please check: A. That the liquid level is sufficient – it should be at least 3 meters in the tank – and that the inlet pressure meets the requirements specified on the pump’s nameplate. B. Before installing the pump body into the vacuum tank, connect the motor to the frequency converter; insulate each of the three wires and apply sealant to them. Use the jog frequency converter to determine the rotation direction of the pump impeller. Ensure that the impeller rotates in the same direction as the volute outlet; if it is rotating in the opposite direction, adjust it on the frequency converter and lock the rotation direction. C. Set the parameters of the frequency converter. Refer to the motor parameters listed on the pump’s nameplate, and correctly set and save values such as motor power, rated current, frequency range, and voltage range in the frequency converter’s menu. Make sure that the V/F curve is set to linear. D. Pipeline accessories such as inlet/outlet pressure gauges, inlet/outlet valves, inlet/outlet bellows, inlet filters, check valves, and return valves are properly installed and degreased. E. Replace the pump body and piping system to ensure that there is no water vapor or other contaminants in the system. 2. Pre-cooling cryopump: 2.1 Ensure that the displacement is complete, then slowly open the inlet valve and the return gas valve. Pre-cool for about 15 minutes, monitor the temperature at the return air measurement point to confirm that the pump has been properly pre-cooled. Open the check valve partially, gradually opening the outlet valve to 1/3 of its capacity (for outlet pipe diameters of DN65 or larger, one full turn is sufficient due to the large diameter of the outlet pipe). 3. Start the pump. Check that the starting conditions are met, then start the pump; if any abnormal noises are heard, stop it and conduct an inspection. Then adjust the outlet valve and the frequency of the inverter to bring the pump into normal operating condition. Be careful at this time to prevent the safety valve from activating. 4. Stop the pump: After stopping the pump, close the inlet and outlet valves, and open the return valve.