IMCA M 103 Flashcards
What is a fully operational DP system?
It is a system able to reliably keep a vessel in position and/or heading when working up to the rated environment
What does “a safe situation” mean?
means one where the work has or could immediately cease with no
serious consequences from the inability to maintain position and/or heading
What are the Dynamic Positioning systems as per IMO circ 1580?
1) Power system;
2) Thruster system; and
3) DP control system.
What is the definition of DP equipment class 1 as per IMO MSC.1580 ?
For equipment class 1, loss of position and/or heading may occur in the event of a single fault.
What is the definitioof DP equipment class 2 as per IMO MSC.1580 ?
For equipment class 2, a loss of position and/or heading will not occur in the event of a single fault in any active component or system. Common static components may be accepted in systems which will not immediately affect position keeping capabilities upon failure
Mention examples of active components or systems
generators, thrusters, switchboards, communications networks, remote controlled valves, etc
Mention examples of static components
cables, pipes, manual valves, etc
What is the definitioof DP equipment class 3 as per IMO MSC.1580 ?
For equipment class 3, a loss of position and/or heading will not occur in the event of a single fault in any active component or system. A single failure includes:
items listed above for class 2, and any normally static component assumed to fail
all components in any one watertight compartment, from fire or flooding
all components in any one fire sub-division, from fire or flooding.
How the station keeping reliability is achieved?
by the use of fault-tolerant DP systems based on the principles of redundancy
What is redundancy?
It is the ability of a component or system to maintain or restore its function when a single failure has occurred.
How can redundancy be achieved?
by installation of multiple components, systems, or alternative means of performing a function.
Why do class societies use FMEA for DP vessels?
To demonstrate the fault tolerance of DP systems, as appropriate to the equipment class of DP, during their design approval process.
Report 3 elements that contribute to DP system Reliability
- Planned amintenance
- condition monitoring
- Annual DP trials
What is the most effective way to ensure the good reliability of DP system? Provide examples.
Through design.
Exampls: specifying high reliability components, carriage of critical spare parts and reducing the number of fault paths that lead to a loss of redundancy
Whot are the Key Elements of Fault-Tolerant Design?
Performance;
Protection;
Detection.
Explain Performance?
Equipment intended to provide redundancy should be capable of its rated capacity or that which is assumed to be available in the event of a failure
Explain Protection
Protection can be a combination of automatic systems, operator competency assurance and procedural barriers designed to prevent faults transferring between sub- systems of the DP system, with the result that there is a vulnerability to common cause failures.
Explain detection
Detection methods should indicate when an essential system is no longer available or no longer has the capacity to carry out its function effectively
How can we mitigate the vulnerabilities of common power closed bus tie systems ?
It can be mitigated by using advanced generator protection (AGP) systems which identify and isolate a range of generator faults not covered by standard protection arrangements
What are thesupplemental studies that should be considered onf FMEA for vessels operating with closed bus ties?
- Harmonic distortion in the intact case and after the worst-case failure (WCF) of harmonic cancellation features;
- Transient voltage studies;
- Extended protection co-ordination studies covering all protective functions in the DP system, not only those in the electrical protection system including earth fault, voltage dip (caused by short circuit), and active & reactive load failures.
What are the key process in testing the redundancy concept?
- Predict
- Prove
- Protect
What does “predict” mean for the redundancy processe concept?
– the FMEA needs to be able to predict the failure modes
What does “Prove” mean for the redundancy processe concept?
the DP FMEA proving trials needs to demonstrate that the FMEA correctly
What does “Protect” mean for the redundancy processe concept?
the redundant systems within the DP system have the performance, protective functions, and detection features to defend the redundancy concept against failure modes
Regarding DP testing, how does the performance is tested?
Performances should be demonstrated in both the intact and various failed conditions
In DP class 3 vessesl, how are the redundant groups to be separated?
The redundant groups are to be separated by A60 fire subdivisions; watertight separation is required where there is a credible risk of flooding. Separation requirements for the DP control system include the provision of a separate DP control room containing at least one backup DP control system that mirrors the main DP control system and which can be engaged manually.
Besides DP control, propulsion, power generation, power distribution, what other systems have to maintain the DP systems level of fault tolerance and redundancy required for the DP equipment class
Auxiliary systems including, but not limited to, fuel oil, lubricating oil, hydraulic oil, sea water cooling, fresh water cooling, HVAC and compressed air are subject to classification society rules and applicable statutory requirements
What is the governor responsible for?
active power sharing (kW) and bus frequency control
What is the AVR responsible for?
regulate control bus voltage and reactive power sharing (kVAr). Failure of AVRs has been the cause of a significant number of blackouts.
How does the generators synchronise?
Each generator should be provided with an independent method of automatic synchronising which has an independent check sync facility.
How does The synchronises work?
The synchronises should be capable of connecting a generator during the voltage and frequency variations that follow the loss of a generator to mitigate the risk that surviving generators might not being capable of their rated capacity.
What are the types of protections
Selective protection
Non-selective protection
What is a Selective protection ?
It identifies the source of a fault and isolates it from the power system
What is a non-Selective protection ?
It cannot positively identify the source of the fault and simply disconnects circuits to remove exposure to the fault condition
What does the selective protection include?
Short circuit;
Earth fault.
What does the non-selective protection include?
Over and under-voltage;
Over and under-frequency;
Overload (where the entire plant is overloaded);
Over-speed;
Over and under-excitation;
Reverse power;
Current and voltage unbalance.
What is the power system concepts for most of DP Vessels?
Radial designs
What is the most commom power distribution system?
DC
How does the DC systems work?
the output of AC generators is rectified to DC and fed to a DC distribution system
What are the advantages of DC power?
Reduced fuel consumption and emissions
Fault currents can be controlled electronically
Mention one of the causes of malfunction on power systemss
Harmonic distortion
What are the main functions of PMS?
GENERATOR MANAGEMENT AND BLACKOUT RECOVERY
What is the most effevtive form of load shedding ?
by variable speed drive (VSD or VFD)
Mention the items which the blackout detection should be based on?
independent sources such as :
-voltage transducers,
-blackout relays
- generator circuit breaker status.