LNG storage tank valves, instruments, and non-destructive testing are not affected by factors

（1） To prevent overpressure accidents in LNG storage tanks and protect the pressure relief of the inner tank, the 20000m ³ low-temperature storage tank is equipped with two pressure relief valves. Pilot operated valves should be used instead of gravity valves for low-temperature storage tanks to avoid leakage when the valve is closed, which can cause valve seat icing and prevent the valve from opening. The valve inlet pipeline is deep below the inner tank ceiling to prevent a large amount of low-temperature gas from entering between the outer tank dome and the inner tank ceiling during pressure release, causing a sharp drop in temperature and resulting in brittle fracture of the outer tank dome. 2. To prevent negative pressure accidents in liquefied natural growth gas storage tanks, the tanks are equipped with a two-stage protection system consisting of a nitrogen filling system and two vacuum valves. When the storage tank experiences low pressure, the protective system valve opens and dry nitrogen gas is replenished into the tank; If the pressure of the storage tank continues to decrease, the vacuum valve will open and supplementary air will enter the storage tank. Supplementing nitrogen can protect the storage tank and prevent the problem of moisture condensation and endangering the tank after humid air enters the tank. The connection of the vacuum valve should be set between the outer tank dome and the inner tank ceiling to prevent the input pipeline from being too long and limiting the flow of gas through the vacuum valve. 3. Due to the low temperature characteristics of LNG storage tanks, a certain number of temperature measurement points are set up on the tank wall, bottom, inner tank, and interlayer between the inner and outer tanks. The temperature measuring points of the inner tank and interlayer are mainly used to measure the temperature between the liquid and the dome of the outer tank and the ceiling of the inner tank, in order to prevent the stratification of low-temperature liquids, which can cause the phenomenon of "rolling" and result in a large amount of gas vaporization, leading to overpressure accidents. The main function of the temperature measuring points on the tank wall and bottom is to use the temperature of the measuring points as a basis during the pre cooling process of the storage tank, to protect the temperature of the inner tank from uniformly decreasing, and to ensure that the temperature difference between the two temperature measuring points does not exceed the design value. 4. To prevent excessive filling of the inner tank, the low-temperature storage tank is equipped with two radar level gauges and one high level switch. When the LNG level exceeds the design level, the inlet pipeline valve of the storage tank will automatically cut off to protect the tank. The 20000m ³ low-temperature storage tank is currently the largest capacity low-temperature liquid storage tank independently designed in China. Its successful equipment marks a new level in the design and manufacturing of large-scale low-temperature liquid storage tanks in China. At the same time, it has accumulated valuable experience for the future design and manufacturing of large capacity low-temperature liquid storage tanks and the localization of large-scale low-temperature liquid storage tanks. （2） Non destructive testing of LNG storage tanks is an important measure to protect the operation of LNG storage tanks. It has high risks and special technical requirements, so some non factors are often hidden. Based on actual conditions, it can be roughly summarized as follows: 1. Non destructive testing personnel have insufficient qualifications for liquefied natural growth gas storage tank testing. Personnel who have corresponding professional qualifications and master LNG storage tank testing technology should understand LNG storage tank equipment technical regulations, relevant product standards, as well as relevant technical documents and drawing regulations. However, in actual practice, some testing personnel have not undergone specialized training and assessment, do not have the corresponding inspection qualifications, lack technical expertise, have weak awareness and work responsibility, and some testing personnel lack a rigorous work attitude and cannot handle this job with caution. 2. When non-destructive testing is not carried out, there are also many factors that affect the environment. LNG storage tanks are generally placed in poorly lit, poorly lit, poorly ventilated, and tightly sealed spaces. The buildings that hold the containers are not sturdy, have poor hygiene conditions, and have not been ventilated, which can greatly affect the patience and vision of postgraduate testing personnel and seriously affect their work attitude. If the container containing stable performance materials is not thoroughly cleaned and replaced, and the residual concentration is not measured, it may also cause harm to personnel entering the container for testing. 3. Violation of regulations and failure to take corresponding measures to enter LNG storage tanks for non-destructive testing, if the prohibition ratio or warning signs are ignored, will bring serious consequences to the testing work. For example, not cutting off the power supply of rotating components, not replacing or conducting qualified tests in areas with radiation sources, and leaving no one outside to supervise. Poor protective measures and ineffective protection against radiation sources are often due to inspection personnel violating regulations and failing to take corresponding measures as required. 4. The incomplete non-destructive testing system and quality protection system are half the battle for success. When the testing system and quality protection system are not sound, inspectors cannot receive systematic education, and may even lead to immature or improper selection of testing personnel, failure to develop corresponding measures before testing, non-standard testing organization, unclear responsibilities of each person, improper work of on-site command and dispatch personnel, and unauthorized departure of supervisors from their posts. These are all factors that cause personal injury.