Emergency release couplings (breakaway couplings)
Emergency release couplings – general information
Emergency release couplings (breakaway couplings) protect against the consequences of accidental, excessive pulling force applied to a flexible loading/unloading hose assembly connected to the piping on the system, when a tanker truck, which is being unloaded, drives away and the hose is still attached. This can cause the hose to burst and the conveyed substance to spill. In this situation, the emergency release coupling installed on the loading/unloading hose assembly disconnects, and the valves in both halves of the coupling close, preventing discharge of the product.
The principle of operation of a coupling with breaking bolts is that before the tension of the hose reaches a value that can tear it apart or pull the fittings off, the bolts connecting the coupling halves are broken and the coupling is disconnected. At the same time, the spring valves in both halves of the coupling shut, preventing the loaded/unloaded medium from flowing out. The coupling has three breaking bolts. Once the emergency situation is under control, the coupling can be reassembled with a new set of breaking bolts and after proper inspection further used.
A coupling with a safety cable can be attached directly to a system (a cable attached to a mobile anchor point on a tank truck) or (more commonly) – attached to the system through a short, additional section of a hose (a cable attached to a fixed anchor point on loading facilities). The cable is shorter than the flexible hose in the corresponding section. When the hose connected to the tank truck begins to move, the safety cable connecting the coupling to the anchor point is stretched, actuating the mechanism that disconnects the coupling. The coupling is disconnected. At the same time, the spring valves in both halves of the coupling shut, preventing the loaded/unloaded medium from flowing out. The coupling comes with three latches connecting the two halves of the coupling, which are released when the safety cable is stretched with sufficient force. The maximum lateral deviation of the pull direction is 90° from the coupling axis. Once the emergency situation is under control, the coupling can be reassembled and reused after careful inspection.
