337

1 INTRODUCTION

Oil platform operations demands a constant supply of

water, fuel, provisions and deck cargo. Freight

transport between port and platform in the oil

industry is provided by Offshore Supply Vessels

(OSV). Supply vessels approach platforms and hold

the position at short distances using a dynamic

positioning system.

These operations contribute to high-risk tasks since

incidents associated with the loss of a ship's position

can lead to damage to the ship and platform, fire,

significant environmental pollution or multiple

casualties.

For example, in 2005 the collision of a supply

vessel with the Mumbai High North platform resulted

in a fire and the death of 22 people. Fire losses were

estimated at $200 million. Another illustrative

accident is the collision between the supply vessel

Sjoborg and the oil platform Statfjord A [12], which

occurred during cargo operations on June 7, 2019. A

technical malfunction on the vessel led to the

activation of the load reduction mode, as a result of

which the power of all the thrusters decreased to 10-

15%. At approximately 01:50, power was lost on two

of the three bow thrusters. As a consequence, the

vessel lost the position and collided with the platform,

sustaining serious damage to the mast and equipment

above the bridge and a dent on the starboard side at

the stern. Due to collision oil platform boat station

was also damaged and the supply vessel struck the oil

platform drilling shaft.

2 DP SYSTEM OVERVIEW

As per IMO MSC Circular 1580 [8]: “Dynamically

positioned vessel (DP vessel) means a unit or a vessel

Monitoring and Identification of DP Operators

Behavioural Traits and Common Errors During

Simulator Training

Y. Bogachenko

& O. Pipchenko

Lerus Training Center, Odessa, Ukraine

National University "Odessa Maritime Academy", Odessa, Ukraine

ABSTRACT: The article presents factors influencing decision making by Dynamic Positioning Operator (DPO)

and statistics of the DPOs behaviour in an emergency situation. Considering that supply operation is performed

by a DP vessel at a distance comparable to its width of the hull to the installation, unit, or another vessel, the

thruster failure may lead to a rapidly developing incident such as collision, pollution, or human injuries. Based

on the IMO guidelines on formal safety assessment authors suggested a risk model of platform supply

operation in dynamic positioning mode. It is shown that different approaches shall be applied for rule-making

and active decision support applications. While rulemaking can be mainly based on retrospective incident-

based data, decision support shall be developed on the basis of the dynamic state of the system. Therefore, it is

necessary to understand the nature of the human element in the specific operation to build up proper

technological and organizational barriers to prevent the forthcoming critical error.

http://www.transnav.eu

the International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 15

Number 2

June 2021

DOI: 10.12716/1001.15.02.09

338

which automatically maintains its position and/or

heading (fixed location, relative location or

predetermined track) by means of thruster force”.

Dynamic Positioning System is a joint work of

seven components (Thrusters, Power, DP Controller,

Human Machinery Interface, Sensors, Position

Reference Systems and DP Operator) with the

purpose to maintain vessel's position and heading.

The simplified process of positioning can be described

as follows (figure 1):

− DP Operator must assure of proper operational

conditions of other components;

− provide DP Controller with necessary data from

Sensors and Position Reference Systems;

− provide control of thrusters to DP controller;

− designate tasks through Human Machinery

Interface (HMI), observe the adequate operation of

all the DP System and satisfactory performance of

the task.

Figure 1. Simplified diagram of a position control process

When the vessel maintains a position and heading

by means of the DP System, the role of the DP

Operator is to observe proper action of all its

components on the screen of the DP Console. On DP

Class 1 vessels a single failure, like improper

operation of a thruster or malfunction of a diesel

generator, may lead to loss of position. That’s why for

critical operations which may lead to loss of human

life, pollution or significant damage of asset the

design of the DP System implies the redundancy

concept.

DP Class 2 and DP Class 3 vessels have

redundancy to ensure positioning capabilities if single

case failure occurs, i.e. loss of thruster or generator or

switchboard with connected generators and thrusts.

Redundant components and systems should be

immediately available without needing manual

intervention from the operators according to IMO

guidelines [8].

3 INCIDENTS STATISTICS

Researches conducted over the years, including J.

Herdzik [10], K. I. Øvergård et al. [13], K. S. Hauff [9],

conclude ‘thruster failure' as the main cause of drive-

off situation. Rules and guidelines on levels of

operator intervention in response to a failure in a DP

Class 2 or DP Class 3 vessel have changed over the

years and different classification societies have chosen

to place different levels of emphasis and different

interpretations on these rules (MTS DP Operations

Guidance [2]).

Statistics made by the International Maritime

Contractor Association (IMCA) on the basis of DP

Station Keeping Reports [3–8] also confirms that

'Thruster/propulsion' failure has the highest

percentage (more than 30%) of main failure causes,

which lead to DP incident, DP undesired event or DP

observation, for last 5 years (figure 2).

Figure 2. Thrusters and propulsion failures in relation to DP

station keeping reports by IMCA

Top positions of secondary causes of failures are

taken by ‘Electrical’ and ‘Human factors’ categories.

'Human Factors' is broad in nature. However, all

30 causes reported in 2020 could be categorized as

'unintentional behaviour' for which there are four

categories: 'sensory error'; 'memory error'; 'decision

error'; and 'action error'. 'Decision' and 'action' errors

led to proportionately more events and the loss of DP

control than any others. 'Decision' errors are defined

as errors where a clear decision was made to operate

in a particular way and 'Action' errors − where a

function or control was selected incorrectly.

The redundancy concept is to make the vessel fault

tolerant without the intervention of the DP Operator,

but there is a number of examples when the proper

action of the DP Operator in an emergency situation

will mitigate the worst consequences of the incident

and stabilize the situation. On the other hand, the DP

operator can make a wrong decision and take an

action that will degrade the vessel capabilities, such as

the push of the 'Emergency stop' button of one of the

properly working thrusters. International

requirements for DP equipment classes 2 and 3

recognize a single inadvertent act of any person,

including DP Operator as a single fault, if such an act

is reasonably probable [11].

The partial risk model of the collision event

between a supply vessel and platform based on IMO

Guidelines on Formal Safety Analysis [11] is

represented in figure 3. The risk model is focused on

the DP operator’s actions that may lead to a drive off

situation. The risk model shows that the incident may

be influenced either by a technical failure in the DP

system and thruster or by human error.

339

Figure 3. Partial risk model of the OSV – platform contact

incident

4 MONITORING AND IDENTIFICATION OF DP

OPERATORS’ ERRORS

Statistics cannot always comprehensively reflect the

number of incidents that could be avoided by proper

action of DP staff (operator and technical), as reports

are formed in different circumstances (operators, ship

types, specifics of the operation, etc.). In order to learn

the behaviour of a DP Operator on the bridge under

the same condition and operation, the case of faulty

thruster was simulated on the full mission bridge

simulator during the DP Simulator, DP Sea time

reduction, DP Revalidation courses and DP

Assessments.

Apparently, when the thruster commences

developing its maximum force, it causes the DP

Operator sudden stress, as it is usually unexpected,

when no changes in DP operation settings were done

by the officer, accompanied with a considerable

amount of noise, and may happen at nighttime. If the

person never encountered this specific situation

before, mentioned factors could considerably affect

the decision making. It is important to note that in this

situation correct and timely actions are crucial.

So, it turns out that improper action of a DP

Operator may create an uncertain situation till the

incident the same as the inaction of a DP Operator

during an emergency scenario will lead to undesired

consequences. And it is possible to conclude that

positive escalation of a near-miss scenario depends on

the competence of the DP operator to properly

analyse dynamic risks and the timeframe necessary

for taking decision and action.

The goal of the research is to identify DP Operators

behavioural traits during an emergency by means of

simulator training, while they maintain vessel

position and heading utilising the DP System, and

encounter the thruster failure.

The research is based on the analysis of 148

practical exercises of 37 different groups on the full

mission bridge simulator. Each group consisted of 2

or 3 candidates. All candidates passed the DP

Induction course at different training centres and

gained some DP seagoing experience. Candidates

performed 4 exercises (figures 3 & 4) to test and train

their ability to avoid incident in case of thruster

failure.

4.1 Exercise 1

After familiarization with the bridge simulator

candidates were given the task: to approach closely

the oil platform utilising the DP System to perform

cargo operations.

The necessary time was spent on the DP set-up and

then on the approach from the 500 m zone towards

the oil platform. The vessel approached closely to the

100 m zone of the oil platform, stopped and stabilised,

and then continued the approach at speed of less than

0.5 knots. At a distance of about 30 m from the oil

platform, the instructor simulates improper

functioning of thruster: the demand and feedback of

thruster have a difference of 10%.

100% of participants did not notice that.

The difference of demand and feedback is

increased so that the DP system gives an alarm

regarding this malfunction. The reaction of DPO in

100% of cases was to call ECR (Engine Control Room)

to ask if everything was alright with the thruster. But

the proper action is to disable the improperly working

thruster from the DP system.

The instructor aggravates the situation further and

simulates failure as full load of thruster's running.

The proper action of the DP Operator is to stop the

faulty thruster by pushing the 'Emergency stop'

button. The same is discussed during the DP

Induction course as a part of the learning process.

And all participants knew this.

Figure 4. Exercise 1 flowchart

In 92% of cases, the action on the bridge was to call

Engine Control Room (ECR) followed by disabling the

340

thruster from DP System, which does not solve the

problem. The debriefing of the exercise was carried

out and proper actions were discussed.

4.2 Exercise 2

On the next day, a similar exercise (figure 5) was

performed. And upon approach close to 30 m from

the installation, the instructor simulated another

thruster as ‘uncontrolled load to 100%’.

98% of participants took correct action and push

the 'Emergency stop' button. But 12% of participants

were confused during an emergency situation and

stopped properly the working thruster, leaving the

faulty thruster to create a load.

Debriefing was carried out with an explanation of

what had happened and what would have been the

proper actions.

Figure 5. Exercises 2,3,4 flowcharts

4.3 Exercise 3

During the next practical exercise upon approach

close to another vessel for ship-to-ship cargo

operation, the instructor simulates the jump of

reference systems, causing a shift in position data. In

this situation, the DP system finds the position offset,

in this specific case 8 metres. The reaction of the DP

system is to bring the vessel to set position (which is

currently 8 metres away) as soon as possible, which

means using all available thrust. Considering that

participants are awaiting thruster failure and when

they see that some thruster runs full load, in 72% of

cases the 'Emergency stop' button was pushed. But

thruster was working properly and followed

commands of DP system.

Figure 6. DPO main behavioural traits in case of thruster

failure

4.4 Exercise 4

To improve the operators’ performance, it was

decided to take the approach described in [1, 14, 15],

where, based on the previous operators' errors and

behaviour, action flowcharts were built and brought

up to candidates as fault recognition and action

algorithm. Before the final exercise, the thruster

monitoring algorithm (figure 7) was provided. The

final exercise included all failures described above.

This allowed achieving a 95% exercise success rate.

Figure 7. Thruster monitoring algorithm

341

All participants were aware that the 'Emergency

stop' button must be activated when the thruster fails

to 100% load, but most of them had never

encountered such situation. Therefore, at first most of

the participants couldn’t grasp the situation. The

important finding is that once the operator is aware of

the situation when 100% load on the thruster is

observed (in case when thruster follows the correct

DP System order), the wrong action is taken in vast

majority of the cases (stop the properly working

thruster).

Only after proper risk analysis before the task and

demonstration of all possible cases of thruster failures,

the participants could recognize an emergency

situation and take the correct action.

5 CONCLUSIONS

The conventional approach to the DPO behaviour in

case of thruster failure concludes either DPO took

proper action or not. It would seem like the

probability for favourable coincidence is 50%. It is

assumed that the probability of correct action being

taken can be increased by explaining the necessity to

push the 'Emergency stop' button.

The authors suggest dividing the situation with

thruster under full load in two scenarios: when the

thruster works properly and follows orders from DP

System and when the thruster has failed to full load.

In both scenarios, there is a probability of taking

proper and incorrect actions. Therefore, there may be

a 60% probability of negative consequences. Practical

exercises show that theory alone and the fact that DP

Operator knows of the actions to be taken, don't lead

to expected action. On the other hand, the expression

'experience beats theory' does not work either. When a

DP Operator faces an emergency, where the

'Emergency stop' button must be pushed, in practice,

it becomes a behavioural habit. In this case, DP

Operator stops thruster(s) even when it is not

required.

Therefore, continuing professional development of

DP Operators under the supervision of experienced

DP practitioner is strongly recommended.

REFERENCES

1. Bogachenko, Y.: DP Concept: Principles of Dynamic

Positioning. Seredniak T. K., Dnipro (2020).

2. DP Operations Guidance: Marine Technology Society

(2012).

3. Dynamic Positioning Station Keeping Review: Incidents

and events reported for 2016 (DPSI 27). (2017).

4. Dynamic Positioning Station Keeping Review: Incidents

and events reported for 2017 (DPSI 28). (2018).

5. Dynamic Positioning Station Keeping Review: Incidents

and events reported for 2018 (DPSI 29). (2019).

6. Dynamic Positioning Station Keeping Review: Incidents

and events reported for 2019 (DPSI 29). (2020).

7. Dynamic Positioning Station Keeping Review: Incidents

and events reported for 2020 (DPSI 30). (2021).

8. Guidelines for vessels and units with dynamic

positioning (DP) systems: (2017).

9. Hauff, K.S.: Analysis of Loss of Position Incidents for

Dynamically Operated Vessels. Department of Marine

Technology, NTNU (2014).

10. Herdzik, J.: Dynamic Positioning Systems during

emergency or unexpected situations. Journal of KONES

Powertrain and Transport. 20, 3, 153–159 (2013).

11. International Maritime Organisation: IMO MSC-

MEPC.2/Circ.12/Rev.2 Revised Guidelines for Formal

Safety Assessment (FSA) for Use in IMO Rule-Making

Process. (2018).

12. Investigation of collision between Sjoborg supply ship

and Statfjord A on 7 June 2019: Petroleum Safety

Authority, Stavanger (2019).

13. Øvergård, K.I., Sorensen, L.J., Nazir, S., Martinsen, T.J.:

Critical incidents during dynamic positioning:

operators’ situation awareness and decision-making in

maritime operations. null. 16, 4, 366–387 (2015).

https://doi.org/10.1080/1463922X.2014.1001007.

14. Pipchenko, O.: Monitoring and identification of errors

during training on navigation simulators. Collection of

Scientific Papers of Admiral Makarov National

University of Shipbuilding. 3–11 (2020).

https://doi.org/10.15589/znp2020.2(480).1.

15. Pipchenko, O., Tsymbal, M., Shevchenko, V.:

Recommendations for Training of Crews Working on

Diesel-Electric Vessels Equipped with Azimuth

Thrusters. TransNav, the International Journal on

Marine Navigation and Safety of Sea Transportation. 12,

3, 567–571 (2018). https://doi.org/10.12716/1001.12.03.17.