LNG Jetty Description
Detailed description of the LNG Jetty structure, fixtures and limitations.
The berth of the LNG jetty is orientated 225° North to minimize the anticipated downtime as a result of the combination of wind, waves and swell.
The LNG jetty consists of:
- Four breasting and five mooring dolphins fitted with fenders and quick release hooks and accessible by catwalks. Fenders frontal pads are designed for hull pressures upto 200kpa and all mooring hooks are of 125 ts each. Parallel Body 110 to 165 meters.
- An unloading platform with a concrete deck providing support for piping and equipment. Fitted with 3 unloading arms (2liquid and 1 vapour) 16” LVL ANSI 150. Spacing between arms 4m. Liquid arms flow rate 5500 cubic meters per hour for each arm.
- A trestle to shore accommodating piping, cables and a roadway for personnel access and small vehicles.
- The LNG jetty is equipped with a mooring load monitoring system, a berthing aid system and an environmental monitoring system. Make Marimatec range 0 to 200 meters.
- ESD (Emergency Shut Down) are Fiber optic make Marimatec six way plug connector reel located near the gangway and also an Electric system make Marimatec 37 way Pyle national connector.
- Jetty is provide with a shore gangway located 16m aft of after Loading arm. Fore and aft slew 3.98 meters. Height limit above datum Min – 8.0 meters and Max – 28 meters.
- Limiting arrival and departure conditions are as follows Maximum current at the start of the approach channel is 2 knots Maximum current at one ship’s length outside the breakwater is 1.5 knots. Current strength must be diminishing towards the port entrance to allow for a positive direction of turning into the port. Cross- currents in opposite directions are not acceptable. Such situations exist one-hour after HW and LW. Minimum UKC = 2.5 meters. The concluded limiting wave height is Hs = 1.75 m in combination with a wind speed of U = 10 m/s [30 s gust speed].
- During LNG discharge – If wind >30 knots stop unloading and second tug on standby. If wind > 35 knots remove gangway, tugs alongside and disconnect loading arms. If wind > 40 knots consider unberthing.
- In case of electrical storms - Stop discharge, close all ship tank valves and vents until storm has cleared the terminal and poses no further threat.
- In case of rolling or list at the berth - Stop discharge if vessel rolls 2 degree. i.e. 1 degree either side of the upright position. Discuss weather forecast and decide on further action.
- The actual decision to berth or unberth the vessel depends on many factors, which can only be assessed by the Pilot or the Master. The above parameters may not therefore be strictly observed by the Pilot in consultation with the Master.
- If it becomes necessary for a ship to vacate the berth before completion of discharge as a result of unexpected adverse weather conditions, then re-berthing of the ship will only be undertaken after the weather conditions have again returned to within the above criteria.
The unloading platform provides support for the main and auxiliary equipment. Two fire monitors are installed at the corner of the Platform. This fire monitor is able to cover the complete loading arm area of the platform.
Fire proofing/cold splash protection
All members above main deck level supporting the main piping are fireproofed. Additional cover is provided as cold splash protection to concrete and steel structures, which are in the immediate exposure to spills and critical for the stability of the jetty. Cracking of the concrete cover in the event of a cold splash and subsequent need for repair can be accepted. However, the structure is protected from failure of the concrete deck under a LNG spill.
Berthing Aid System
Once the ship is positioned in front of the jetty head, two laser transceivers will monitor its movement. They inform in real time the pilot about speed and direction of the stern and the bow of the ship by means of a large display screen located on MD 3.
Two sets of three lamps (one stern and one bow are installed on display frame for speed indication as follows:
|Green||Safe speed cm/s||0 to 10|
|Amber||Cautionary speed cm/s||10 to 15|
|Red||Dangerous speed cm/s||Above 15|
The pilot display unit information shall be clearly visible, in day as well as night-time, to the naked eye at a distance of 200 m under "normal" weather condition, i.e. no rain, fog.
Mooring load Monitoring System
This system consists of a number of strain gauges, installed in the mooring hooks, which convert the tension forces in the mooring lines to electric signal. The aim of this system is to provide continuous monitoring of mooring line loads. The ship is moored on five mooring dolphins and the four breasting dolphins. On each mooring hook, sensors are positioned to measure the strain exerted by the ship on each mooring line.
Max. Working Load of Mooring Hooks :: 125 Ts
Load Monitoring System High Load Alarm setting :: 30 Ts