The emergency shutdown (ESD) system is a requirement of the IMO code for the carriage of liquified gases in bulk and is a recommendation of SIGTTO. It is fitted to protect the ship and terminal in the event of cryogenic or fire risk, on the ship or at the terminal.
The system will stop the flow of LNG liquid and vapour by shutting down the pumps and gas compressors as well as manifold .
This is achieved by the Ship-Shore Link/ESD system. Ship’s and terminal’s emergency systems are linked via a ship-shore cable which carries ESD, telecommunications and data signals when the ship is berthed at the jetty.
There are two separate systems installed which are in use in the various terminals with which the vessel will berth:
- Electric (Pyle National)
The fibre-optic system utilises a 6-way ST ferrule Furukawa compatible shipside connector into which the shore plug a flexible fibreoptic connector.
The Electric system uses a 37-way explosion proof connector with umbilical cable provided by shore or in some cases the ship’s own equipment. The electric system enables ship-ship transfer with ESD and hotline telephone connection.
The electric system circuits are protected with zener barriers as secondary protection in case the ship breaks away while circuits are still energised. Most shore systems are similarly protected.
The ship’s ESD system is active at all times, whether at sea or in port. When at sea all manifold and tank filling valves are held in the shut position and the cargo and spray pumps are held in the off position. The cargo compressors may be operated as normal, but will stop if an ESD is initiated. The shore ESD input is blocked at Sea.
The control and processing circuitry are installed in the safetylink cabinet in the cargo control room. ESD signals from and to the Distributed Control System and Cargo Control ESD system are fed to the safety link cabinet as are telephone signals.
The manual push butons, which will initiate ESD1 both on the ship and ashore, are usually distributed at the following locations:
- Central control room
- Fire control station
- On Each tank dome
- Port manifold
- Starboard manifold
- Compressor house
- Focsle entrance
The ESD will activate the following on the ship:
- Stop the high and low duty compressors
- Stop the main cargo pumps in each tank
- Stop the spray pumps in each tank
- Close all the manifold valves
- Close all the spray nozzle valves and tank filling valves
- Shut down the inert gas generator system
- Signal to the terminal to stop operations
- Activate the ESD alarm.