LNG cryogenic tank blasting and purging
Thread Content
In the MRC five-refrigerant mixed-refrigeration cryogenic box, there is a high pressure difference between the high-pressure gas inlet and the main return line during operation; this is likely due to blockages, and blasting cleaning is required. I would like to know how to carry out such blasting cleaning in a safe and effective manner What should be noted during the purging process? How are the purge process parameters controlled?
The blasting and purging of LNG cryogenic tanks is a task that requires utmost attention to safety. Below are the steps and precautions for performing cold box blasting purging: 1. **Preparatory work**: - Ensure that all operators are familiar with the procedure and safety measures. - Prepare the necessary safety equipment, such as safety glasses, gloves, ear protection, etc. 2. **Shut down the system and reduce pressure**: - Close the inlet and outlet valves of the cryogenic tank, disconnect the power supply, and ensure that the system is completely stopped. - Release the pressure in the system slowly to avoid dangers caused by sudden release. 3. **Connect the purging equipment**: - Connect the dedicated purging equipment to the inlet and outlet ends of the cryogenic box. - Ensure that all connections are tightly sealed to prevent air leakage during purging. 4. **Perform purging**: - Use an appropriate purging gas as recommended by the equipment manufacturer; nitrogen or dry air are commonly used. - Control the purge pressure and flow rate. Generally, the pressure should not be too high to avoid damaging the internal structure of the cryogenic box. - Check the system pressure multiple times during the purging process to ensure it remains within safe limits. 5. **Detection and restart**: - After the purging is complete, turn off the purging equipment and disconnect all connections. - Perform a leak test on the cold box and its connecting pipelines. - If the test is successful, the system can be restarted and gradually adjusted to normal operation. **Precautions**: – Throughout the entire process, pressure and temperature should be monitored continuously to prevent any abnormalities from occurring. - Ensure good ventilation at the site to avoid dangers caused by gas leaks. - Operators must wear appropriate personal protective equipment to ensure safety. Ensuring compliance with the above steps and precautions can make the blowdown process of LNG cryogenic tanks safe and effective. .
There is no need for blasting and purging in the initial stage; first, it is necessary to determine which gas flow path is blocked and which heat exchanger is affected； What is the cause of the blockage? ； Is the blockage caused by dust, or by water or carbon dioxide? ； If it is dust, the cold box does not need to be reheated, and purging can be carried out ； If it is the latter, rewarming is required. The blasting purge pressure should not be set too high; it must not exceed the operating pressure of the equipment. Care should be taken to prevent communication between the low-pressure side and the high-pressure side. It is recommended to use the pressure on the low-pressure side for blasting purging. Blockages in cold boxes are generally easy to purge.
First, it is necessary to determine the cause of the blockage based on the operating conditions. There should be a filter for the refrigerant as it enters the cold box; therefore, a blockage in the refrigerant is likely. Blasting and purging are not very effective in such cases. Instead, it is advisable to use warmed dry gas for backwashing, carry out drainage at the lowest points, check the process operation parameters and ensure that the refrigerant meets the required standards, in order to identify the most likely source of the blockage.
Blasting doesn’t seem very effective; it’s mainly cleaning by blowing that works