What are the issues with installing cut-off valves and check valves on the liquid-phase pipelines in LNG refueling stations?
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According to clause 9.2.1 of the new regulation 50156, a shut-off valve and a check valve should be installed on the liquid discharge pipeline connecting to the tank truck. 1. Does the liquid discharge pipeline include the liquid phase pipeline from the tank truck to the unloading booster? Does a check valve need to be installed on the liquid-phase pipeline that connects the tank truck to the pressure-enhancing vaporizer? During actual operation, this check valve can have some impact on liquid discharge. 2. Should it be a cut-off valve, a manual stop valve, or a pneumatic cut-off valve? Either one is fine.
A check valve is not required for the pipeline from the tank truck to the booster, as the booster’s pipeline is equipped with pneumatic and manual shut-off valves that allow for automatic isolation in emergency situations； The purpose of installing a check valve in the liquid discharge pipeline is to prevent the BOG or liquid inside the storage tank from flowing back into the tank truck in case the pressure in the storage tank is lower than that in the tank truck, as the check valve allows flow in only one direction. Typically, stop valves are equipped with both manual and pneumatic controls, so that they can be closed manually in the event of a pneumatic failure
The old standards required the installation of emergency shut-off valves; I don’t have the new standards available at the moment, but I personally think it’s better to follow the stricter requirements.