Contingency Plan is used to provide an operation procedure for operator to deal with an emergency condition to reduce the impact of accident to life, environment and property. As previous introduction , the drive-off of ST could collide with FPSO with critical high potential and serious result. Every single second is critical to successful recovery. But there is not specific contingency plan for DPO to follow. In addition, there are five thrusters and one rudder. During or before the process of recovery, the thrusters and rudder are perhaps in different degradation or failure conditions, a plan to manipulate the remaining variable equipments smartly and swiftly to achieve a better recovery performance should be prepared in advance. The function of ORDSS is required to give control order to all thrusters and rudder to avoid collision. Furthermore, there are a Senior DPO and a DPO working at bridge during offloading operation, and they shift the duty of DP operation every hour. It is time-saving to attribute the responsibility and set the leading role by the contingency procedure in advance. So a contingency plan is necessary.
The design logic of contingency plan is to follow the importance order, “Life, Ship, Environment and Save offloading Time Loss”. This sequence decides the sequence of
actions. There is no question that life should be on the top priority. The oil tanker and FPSO both contain tens of thousands of barrels of oil and easy-ignited gas. If the integrity of the vessel cannot be guaranteed, the environment is polluted definitely. The procedure explanation of plan is as table 8 and below,
Table 6 Operation Steps and Responsibility Distribution
Senior DPO DPO
Step 1 The Duty DPO detects the vessel drive-off and informs the other DPO and they confirm whether the vessel can stop before ESD 2 or not
Step 2
Maneuver the vessel to turn the vessel off the collision course according predefined procedure
1. Inform the sailors working in bow offloading room, FPSO control room to withdraw the people working at the stern area
2. Active ESD 2
3. Inform engineer in engine control room to pay attention to the health condition of engines and switchboard, arrange one person to the
Steering-gear Room for emergency manual operation of rudder, and no one is allowed take any operation in engine room without order from bridge.
4. Inform all vessels in the safety zone to pay attention to leave the emergency maneuvering course of ST
Step 3 Observe
Step 4
Give order to DPO to maneuver the vessel to keep same speed at bow and stern and away from
FPSO further, ship alongside face to environment load
Execute Sr. DPO order
Step 5 Observe. If the collision is unavoidable, DPO should inform all crew to prepare fire fighting and prevent oil pollution.
Step 1: The Duty DPO detects the vessel drive-off and informs the other DPO and confirms whether the vessel can stop before ESD 2 or not
The bridge team management is to transfer the latest information about a new situation to each other.
Since the DP drive-off alarm is based on a pre-set speed and ST is under surging movement, it is impossible to stop vessel in such a short distance, when a vessel has already gained a speed. It takes certain time to build up the speed due to the vessel
inertia. With ORDSS install onboard, DPO can detect drive-off before or at the critical point of start. An astern propulsion or emergency shutdown to stop the vessel movement is possible. It could save offloading time loss.
Step 2: DPO inform the relevant persons and active ESD 2. Senior DP takes action to maneuver the vessel to turn the vessel off the collision course
In case there is only one DPO at bridge at the moment of drive-off, the DPO should inform the relevant person at bow offloading room, FPSO astern to escape according to the policy of Life, Vessel and Environment, maneuver the vessel, and active ESD 2. The heading changing of ST is based on the chapter 4.2. The details of thrusters and rudder refer to the Appendix VII.
Step 3: Sr. DPO observes condition after maneuvering action execution. DPO wait for DPO further maneuvering order
Step 4: Sr. DPO order the second vessel maneuvering order to keep the ST away from FPSO
When heading of ST is off the collision course with FPSO, the ST should keep away from the FPSO, especially the stern. The stern of ST is still speed up to the FPSO, due to heading change. A second order should make stern go to the opposite direction by changing the propulsion of Aft Thruster, Azimuth Thruster or even rudder to provide opposite force, and prevent heading from going back at same time by Bow Thruster or Fwd Azimuth Thruster. As strong wind and rough sea is quite normal at North Sea, using environment force to assist heading is also considered here. The detail operation procedure is as the Appendix VI
Step 5: Sr. DPO observe. If the collision is unavoidable, DPO should inform all crew to prepare fire fighting and prevent oil pollution.