# The Evolution and Development Trends of LNG Loading and Unloading Arms
## 2 Development of Marine LNG Loading and Unloading Arms
### Overall Structure of the Marine Loading Arm
#### 2.1.2 Emergency Disconnection System  
The emergency disconnection system (ERS) in the LNG loading arm mainly consists of an emergency release coupler (ERC), an electrical control system, and a hydraulic control system. When a disaster occurs at the loading site or the LNG ship moves out of the specified envelope range, the system will automatically close the valves of the emergency release coupler and safely separate the loading arm from the LNG ship. In addition, the valves on both sides of the emergency release coupler can be closed and separated by manually operating the electrical control system. In the 1980s, foreign loading arm manufacturers were committed to the research and development of emergency disconnection devices for loading and unloading arms and successfully applied them to loading and unloading arms for petroleum, liquefied natural gas, etc., avoiding major accidents many times. In 1982, the Italian company MIB successfully designed the first emergency disconnection device for LNG loading and unloading arms. The device consists of an emergency disconnection joint and two ball valves. The ball valves are driven to close by an interlocking hydraulic system and can operate stably under ultra-low temperature conditions. The emergency disconnection devices of SVT and FMC both adopt a double-ball-valve interlocking emergency cut-off structure, which are controlled by a single hydraulic cylinder. The valves are closed and the joints are disengaged through a mechanical or hydraulic interlocking system [25]. The emergency disconnection device of the British company KLAW adopts its unique Flip-Flap flap valve technology. Compared with the commonly used spring-lifted valve technology, it has a lighter structure. Even if the device suffers partial fracture, the valve can still be closed smoothly. At present, the emergency disconnection devices of loading and unloading arms in China's domestic LNG receiving stations mostly use equipment from companies such as SVT and FMC. Meanwhile, the research on emergency disconnection devices is also in a stage of rapid development. [PERSON] and others proposed a cryogenic emergency disconnection device with superior sealing performance. By setting the upper valve body spool and the lower valve body spool of the self-sealing valve in an opposite-top manner and fixing them with a clamp assembly, the sealing performance of the device after disconnection is effectively ensured. The emergency disconnection device developed by CNOOC Gas and Power Group adopts a mechanical interlock structure, which can complete rapid disconnection and self-locking within five seconds. [PERSON] and others proposed using a worm-gear drive mechanism to drive the opening and closing of the valve. The worm-gear mechanism and the locking device are driven by a hydraulic system to achieve step-by-step control of the valve and the locking mechanism. In view of the problem that the hydraulic cylinder and the four-bar mechanism are easily pulled and damaged when the left and right valve bodies of the emergency disconnection device are separated, [PERSON] and others designed a hydraulic cylinder with an emergency disconnection function, which can simultaneously close the valve of the emergency disconnection device and separate the hydraulic cylinder and the four-bar mechanism. In 2023, Lianyungang Ocean Fluid Loading and Unloading Equipment Co., Ltd. (SOSCO), successfully achieved the complete localization of the cryogenic emergency disconnection device, being able to close the cut-off valve within 5-10 s and complete the separation of the loading arm from the tank ship within 2 s, reaching the international first-class level. Emergency disconnection devices generally have supporting hydraulic or pneumatic systems to drive their normal operation. Currently, there is a common problem in hydraulic systems, that is, due to leakage, the pressure-holding pressure of the hydraulic system is insufficient, and the hydraulic oil pump is in operation for a long time.