Virtual reality system for marine loading arms operator training · 2015. 11. 27. · M. Castillo et al. Virtual reality system for marine loading arms operator training 3 additional

Virtual reality system for marine loading arms operator training

Miguel Castillo*, Leonel Atencio

Castillomax Oil & Gas Research and Development Direction, El Recreo, Caracas, Venezuela.

Abstract

Oil tanker cargo transfer is a hazardous operation. Marine loading arms are used to connect vessels with the

loading platform in a secure way. We present a virtual reality system intended for training of marine loading

arms operators. The virtual reality system was created using game-based development software and modern

head mounted display technology in combination with a commercial infrared tracking device. We offer a

description of the inclusion of several control options for the loading arm, including a virtual static control, a

virtual tool tracked control and a custom made replica of a real radio control. We also describe the inclusion

of loading arms’ working envelopes into the simulator.

Keywords: virtual reality; training simulator; marine loading arms

1. Introduction

Oil tanker loading/unloading operations are a key component of the bulk fluids transport processes

associated with oil production and trading. Tanker cargo transfer can occur with the vessel moored besides a

jetty or with the vessel moored at an offshore floating buoy. Marine loading facilities nowadays use either

hoses or metal loading arms as cargo transfer system for oil tankers [1]. Marine loading arms are basically

articulated arrays of pipes that are able to revolve in a wide range, therefore they can follow the movements of

a moored ship and still hold a secure connection for a safe liquid cargo transfer. There is an inherent risk

associated with loading a tanker vessel moored at a jetty [2]. The outstanding inertia of the vessel together

with the fire/explosion risks associated with the liquid being transferred represent a threatening combination.

This threat has inspired studies aiming at identifying and minimizing risks associated with tanker

loading/discharge operations [3], which recommend proper operator training as a key ingredient in order to

minimize risk.

Loading arms operator training is a time consuming task, demanding to halt productivity of a given arm in

order to allow practice hours. The training process involves theoretical lessons followed by practice sessions.

The inclusion of an intermediate phase of simulator training between theoretical lessons and actual practice

with a real loading arm, can reduce learning time, thus reducing the time loading arms are kept from

productive tasks. Virtual reality environments have proven to have great potential for training spatial and

* Corresponding author. Tel.: +58-212-7629408

E-mail address: [email protected]

2 M. Castillo et al. Virtual reality system for marine loading arms operator training

visual-spatial tasks [4,5] and provide exceptional training enhancement, allowing the trainee to envision

diverse situations that may occur during the real task performance [6–8] .

Fig. 1. Aerial view of the virtual marine environment used in our simulator, displaying the typical berthing configuration for oil tankers.

Marine loading arms are located at the loading platform on the berth, so as to be connected to the ship’s manifold connections at port

side.

There are multiple reported examples of virtual reality systems for industrial applications, for example a

simulator for excavators and construction machines [9]; a simulator for the maintenance of a refinery’s

centrifugal pump system [10]; a virtual reality instructional tool for a hydroelectric unit of energy [11] and

for electrical power stations [12]; a virtual environment for training of overhead crane operators [13] and truck

crane operators [14]; a virtual training system for computer numerical control milling operations [15]; a

welding simulator [16] and many others [8]. With respect to marine related simulators, part of the literature is

dedicated to military applications, for example virtual training for the officer of the deck on a submarine [17],

for helicopter operations [18], deck operations at aircraft carriers [19], firefighter training [20,21] and game-

based virtual training [22]. Besides military applications, there are simulators for ship navigation [23] and

ship cranes [24]. Of special interest in our case, there has been a lot of effort developing simulators for several

marine port machinery [25], cranes [26,27] as well as container trucks and straddle carriers [28]. However,

and despite the fact they are a common cargo transfer equipment, we haven’t found simulators for marine

loading arms.

2. General description of the process being simulated

The main task of a marine loading arm operator is to safely connect the loading arm with the manifold of

the tanker. This pipe manifold is located on the ship’s deck at both starboard side and port side, and it is

connected by pipes with the different tanks located inside the ship’s inner hull. Prior to the operation of the

loading arms, the tanker is positioned and secured along the jetty (see figure 1).

During a cargo transfer operation one or several loading arms are used. For unloading operations the crude

is pumped using the ship’s pumps. For loading operations, ship’s pumps are not used, and the cargo is gravity

fed to the tanks. While the liquid is filling the tanks, the gases inside them are displaced. Sometimes an

M. Castillo et al. Virtual reality system for marine loading arms operator training 3

additional loading arm is used as vapour emission control system in order to collect these gases and send them

to treatment facilities on shore. The operator has to position and connect each loading arm involved in the

transfer operation in a sequential way.

While the cargo transfer process takes several hours (during which loading arms move with the ship),

positioning and connecting/disconnecting a loading arm takes place in a short time. Trained operators

typically perform the task in a matter 1 minute or less for each arm. Loading arm operators can move between

the loading platform and the vessel, to gain a better view of the process. Control of the arms is performed as

discussed in section 3.2. During the process, the operator can be visually aided by other personnel, and he is

in communication with a supervisor located in a control room on the platform.

The actual connection between the outboard swivel assembly of a loading arm and the corresponding pipe

flange at the manifold depends on the model of the loading arm. The final arm connection can be a simple

flange, requiring manual connection by an operator or can be a quick connect/disconnect coupler (QC/DC)

that can be hydraulic or manually driven. Hydraulic QC/DC usually have a set of clamps that work

simultaneously to ensure a rapid coupling. Our particular application uses a hydraulically driven QC/DC. In

addition, an emergency release coupling (ERC) is located just after the QC/DC (inboard direction) in order to

halt the liquid flow and mechanically disengage the loading arm in case of an emergency. The ERC can be

triggered by the operator from the different control devices or by an automated control system.

3. Simulator development

Our simulator has been developed using the Unity3D game development engine in combination with

the Oculus Rift head mounted display (HMD) and the Leap MotionTM controller. Although Unity3D is

intended for game development, it provides a state of the art environment for developing virtual reality

systems. A recent study evidences how the combination of an effective game based software like Unity3D

with modern HDM visualization and an intuitive control interface can assure a high level of fidelity, just as

Fig. 2. Training simulator UML state diagram for a configuration including one trainee, a single observer and three loading arms.


it is expected from a virtual training environment [29]. The state diagram of the simulator is depicted in

figure 2.

Our system uses the Oculus Rift head mounted display. Two or more headsets are used, one for the trainee

and one or more for the instructor and additional instructors/trainees. The HMD worn by the trainee has a

Leap MotionTM tracking device fixed on front. The Leap MotionTM controller has three infrared light emitters

and two infrared cameras, and was designed to work as gesture and position tracking device. Due to the size

of model objects and hand displacements involved in the process of controlling the arm (from a couple of

centimeters to one meter), the accuracy of the Leap MotionTM, proven to be of the order of 0.2 mm for static

objects and 1.2 mm for dynamic setups [30], is more than enough to ensure proper hand and finger

manipulation of virtual objects in our case.

3.1. Marine Terminal virtual environment

The virtual marine port terminal used by our simulator is inspired in the TAECJ, spanish acronym for

Terminal de Almacenamiento y Embarque de Crudo Jose (also known as Jose petroterminal) illustrated in

figure 3. TAECJ is an offshore platform operated by PDVSA, located north–northeast of the Jose Oil &

Petrochemical Industrial Complex, in Barcelona Bay, Venezuela. The terminal is 6.3 km from the coastline,

and it is connected to shore installations via underwater pipelines. It can serve oil tankers of up to 250.000

dwt and it is able to handle crude oil at a load/unload rate of up to 80.000 oil barrels per hour.

The first part of the development is the generation of geometric models for the loading arms, jetty and

vessel on CAD software. Geometric models of loading arms are obtained from commercial designs and

generated in 3D Studio Max. Loading arms located at the TAECJ are single counterweight hydraulically

operated marine loading arms manufactured by Kanon Loading Equipment. See figure 3 (right bottom) and

Fig. 3. Top left: TAECJ terminal geographical location at Venezuelan central coastline, indicated by a white bull’s eye on the map. Top right:

Oil tanker during a cargo transfer operation at one of TAEJC’ three berths. Bottom left: A closer look at the loading platform, showing the

control tower at the right side and three deployed loading arms. Bottom right: Two deployed loading arms seen from below, near the location

of an enclosed control panel.


figure 4 (left) to appreciate real and virtual arms. Special care was taken to model every detail possible of the

arm’s outermost swivel assembly, with its hydraulic QC/DC and ERC, since a proper connection of this

assembly to a ship’s flange is the ultimate goal of the training. The virtual QC/DC is illustrated in figure 4

(right).

The oil tanker model corresponds to a very large crude carrier (VLCC), the largest tanker class allowed by

the TAECJ. A large pier section is included in the environment, but the trainee is restricted to move within the

section corresponding to the loading platform, where the loading arms and their control panels are located.

Special care was taken to choose proper rendering for each geometrical object (without compromising overall

performance), since as it has been recently tested, enhancing realism in virtual environments helps improve

spatial cognition [31].

3.2. Loading arms control

Several options are available in the real world to control loading arms. For hazardous operations, there is

usually an explosion protected control panel, sometimes combined with local terminals and pendant controls.

When simultaneous control of several arms is required, like in our case of interest, the most versatile option is

a radio control, communicating with a receiver built inside the protective enclosure where the hydraulic

systems resides [32].

Our simulator includes three control options illustrated in figure 5. Two of them, namely an enclosed

control panel and a pendant control, are implemented in the virtual scenario and can be manipulated thanks to

the Leap MotionTM hand and tool tracking capabilities. In order to use the enclosed control panel the trainee

has to navigate towards its front (or switch through the preconfigured views) and use his fingers to press the

buttons on the panel (figure 5 top left). To use the pendant control, the trainee has to hold a small plastic

target to be detected by the Leap MotionTM. After detection the stick becomes a virtual tool that can be

tracked, the pendant appears on the display and the trainee can use his finger to press the different buttons on

Fig. 4. Left: A view of the platform from an observer located at the catwalk over the tanker’s deck manifold, showing four loading arms, three

of them connected during operation and one of them resting on its standby position. The withe flag points at the trainee’s avatar (appreciable

only by virtual observers). Right top: Trainee’s appreciation when the manifold side preconfigured view is selected, giving him a better look

for the final connection. At this time, the QC/DC has its clamps opened prior to connection. Right bottom: After the trainee’s pushes the

QC/DC button, clamps are closed securing the connection.


the control (figure 5 top right). The third control option is a physical wired replica of an actual wireless

control, included in order to incorporate an additional factor of realism. Since both the Oculus Rift and the

Leap MotionTM are wired, the fact that our custom control is wired does not affect the mobility of the trainee.

Our custom control is based on a standard microprocessor, using 10 digital input channels and 3 analog

channels with 8 bit resolution, powered through an USB port. The microprocessor is embedded within a 3D

printed plastic housing mimicking a real control, including the top protective fence. Top controls include two

analog joysticks to move the trainee or the arm (depending on the key switch located on the right side), a

selector switch to choose between available loading arms and an emergency stop push button. On the right

side there is a switch key to change between arm/trainee’s motion control for the joysticks on the topside and

two push buttons intended to navigate through different preconfigured views (1st person, besides manifold,

besides loading arm for example). Different views are intended to allow the virtual operator to gain a better

look of the arm’s final connection position (just recall that, as commented in section 2.1, real operators can

move around freely). On the left side there are four push buttons, one of them activates the QC/DC, another

one triggers the emergency release coupler, the other two are free and can be programmed at will to cope with

different training scenarios.

Fig. 5. Illustration of different loading arm control options implemented in our simulator. Top left: Using the virtual enclosed control panel.

A virtual display showing the view of a camera on the arm’s tripe swivel assembly was added to avoid trainee’s need to turn his head. Top

right: Using the virtual pendant control. With his right hand, the trainee holds a plastic target (orange stick) and with its left hand he operates

the pendant control. Bottom left: Direct manipulation of arm’s locking device. Bottom right: Using the radio control replica to maneuver the

arm or to move around the virtual environment.


When the trainee is using the virtual control panel or the virtual pendant control he has to “look at his

hand”. Expert operators may rely on their knowledge about the position of the different buttons and therefore

be capable of operating the loading arm without having to see their control. While this is the case for expert

operators, novel operators do have to look at their controls.

It is known that distance perception in virtual reality is diminished with respect to real world up to 50%

specially for depth determinations, both between the observer and an object and between different objects

[33,34]. Some studies have shown how frontal distances are far better perceived in virtual reality than depth

extents [35]. This reduced depth perception may affect the positioning of the arm in front of the ship’s

connection in the simulator, however the use of different views helps. Besides, the increased depth perception

will make the trainee feel that positioning of a real loading arm is even easier than in the simulation. Users of

both our simulator and real loading arms confirm the above observation.

3.3. Loading arm envelope and emergency disconnection

Marine loading arms have what is called an envelope, i.e. a surface in three dimensional space representing

the boundary for a safe motion. Positioning tracking systems monitor the arm’s position. Pre-alarms both

visible an audible are triggered to indicate the operator when ship movement has to be corrected by tightening

the mooring lines. When the arm is near the envelope a first alarm is issued and liquid flow is halted. If the

arm reaches the envelope a second alarm is triggered and the ERC is activated, thus disconnecting the arm

from the ship. The envelope and its corresponding alarm boundaries depend on the design and on the safe

operating conditions accepted as reference by the designer [36].

A moored tanker moves horizontally due to long period (of the order of 1 minute) wave motion and

vertically due to low period (of the order of 10 seconds) wave motion [36]. Our simulation incorporates tidal

motion more intended for pedagogical purposes than to simulate the connection of the loading arms, since no

cargo transfer operation is started without secure conditions. However, with accelerated time the effect of

wave motion can be easily demonstrated thanks to the visual environment during training.

Fig. 6. Illustration of the custom made control and its functions.


Virtual reality systems offer the ability to incorporate elements that are not visible in reality. We take

advantage of this by incorporating the three alarm surfaces of loading arms’ operating envelope into the

simulator. Based on the designer’s information, three dimensional curves were parametrized and included as

solid objects with their corresponding collision rule. Parametrization was simplified using a reduced

mechanical model of the arm with three degrees of freedom depicted in figure 7. Equations (1) to (3) give the

position of the outermost part of the model arm (corresponding to point C in figure 7) with respect to the

reference frame indicated in the figure:

)sin()sin()sin( 32 LLxc (1)

)cos()cos( 321 LLLyc (2)

)cos()sin()sin( 32 LLzc (3)

These coordinates are then translated to the overall reference frame used in our virtual environment,

knowing that the origin coincides with the arm’s base. Figure 8 illustrates the inclusion of the envelope.

4. Concluding remarks

We have presented a virtual training simulator for marine loading operators, comprising a technological

integration of game-based software technology with new generation head display and motion tracking

detectors used to offer hand and tool detection.

It is important to recall that virtual training does not only include the mechanical operation of loading

arms. Security guidelines often include rigorous protocols to be followed before and after the actual

connection/disconnection operation takes place [3]. Things like pre-transfer conferences, flange preparation,

alignment check for connection and line draining, proper flange disconnection and O-ring inspection for

disconnection have to be performed. Reviewing of these protocols may turn out to be bothersome during a

classroom class. Performing protocol practice while submerged in a virtual environment improves trainee’s

engagement.

Besides its role as a simulator, the virtual reality environment proved to be an excellent multimedia support

for the theoretical part of the training. Such is the case of the enhanced illustration of the role of the

operational envelope of the loading arms. This also sets the table for several training scenarios like evaluating

trainee’s reaction to a sudden an unexpected mechanical failure of the loading arm, sudden malfunctioning of

one of the controls, or any kind of extraordinary hazardous situation (it is important to recall that although

loading arm failure seldom occurs, it is a commonly considered event in risk assessments [37,38]). In

Fig. 7. Simplified model of the loading arm used to obtain parametric expressions for the envelope.


addition, our work provides a platform to simulate maintenance tasks and study best practices, or to essay

new/updated procedures, an important factor identified by a recent study in order to improve marine loading

arms operation reliability [39].

Although our particular application was developed for oil loading/unloading operations, there are multiple

application of liquid cargo transfer that are as well addressed by our simulator, from liquid natural gas to

cryogenic liquids as well petrochemical liquid cargo, all of which encompass important hazards, therefore

sustaining the use of virtual reality operator training.

Future efforts will be directed to increase the realm, including real sounds, adding other vessel sizes and

incorporating a virtual reality treadmill like the recently released Virtuix Omni, allowing the trainee to walk

his way through the virtual environment. Additionally, the inclusion of invisible hazards virtual illustration,

like for example the spreading of flammable gases during rapidly controlled spills, or toxic fumes

dissemination due to leaks is being developed.

Acknowledgements

Authors wish to acknowledge the research and development team at Castillomax Oil and Gas, Sammy

Bechara and Angel Rivas for computational support, Kelly Reyes for electronics support, Gilver Fernández

for design support and Omar Freites and Eduardo Hernández for mechanical support. We also acknowledge

Jesus Viloria, former member of our R&D team, for computational support in the early stage of the project

and Dr. Iván Sánchez for scientific advice.

Fig. 7. Left: Illustration of the envelope for the deployed loading arm. Green, yellow and red surfaces indicate the pre-alarm, 1st and 2nd alarm

locations (to ease the visualization of the surfaces, the rendering of the ship’s deck was simplified and the sea is not shown). Right: When the

2nd alarm is triggered due to an extreme ship motion, the emergency release coupling is activated, leaving the outermost part of the triple swivel

assembly connected to the ship’s manifold.


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Virtual reality system for marine loading arms operator training · 2015. 11. 27. · M. Castillo et al. Virtual reality system for marine loading arms operator training 3 additional

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