Issues regarding the annual inspection of safety valves on LNG carriers

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As the title suggests, it seems that there is no mandatory requirement for annual inspection of safety valves abroad; mainly, this requirement exists in China. I’m not very familiar with safety valves, and I have a few questions. 1. The safety valves on LNG ships mainly include those on the storage tanks and the liquid-phase pipelines. The safety valves of LNG storage tanks discharge BOG vapor when overpressure occurs, while when the liquid-phase pipelines expand due to heat and overpressure is generated, what is discharged is mainly BOG vapor or LNG liquid, or both. 2. How should the safety valves used on LNG carriers be inspected annually? Given the nature of the maritime industry, is online calibration generally the preferred method? 3. Generally, the inspection cycle is set at one year; after inspection, the safety valve is sealed with lead. If the safety valve is not used for a year after inspection, does it still need to be inspected before being used again, or should it be inspected again after one year has passed since the seal was removed? 4. How should safety valves be replaced during inspection to ensure no shutdown? As I understand it, usually there is one safety valve in use and one as a backup; during inspection, the valve in use is replaced. According to the requirements for annual inspections, these two safety valves need to be sent for inspection at different times, in order to prevent both from reaching their inspection deadline at the same time 5. The safety valve can be equipped with a lifting device; will using this device to manually discharge fluid affect the accuracy of the spring, that is, the set pressure of the safety valve? Thank you all, brothers; I’d like to express my gratitude here first!!!!!