Repository - Scientific Journals of the Maritime University of Szczecin - Conditions of safe ship operation...

Zeszyty Naukowe 36(108) z. 1 55

Scientific Journals

Zeszyty Naukowe

Maritime University of Szczecin

Akademia Morska w Szczecinie

2013, 36(108) z. 1 pp. 55–58 2013, 36(108) z. 1 s. 55–58

ISSN 1733-8670

Conditions of safe ship operation in sea waterway systems

Stanisław Gucma

Maritime University of Szczecin, Marine Traffic Engineering Centre

70-500 Szczecin, ul. Wały Chrobrego 1–2, e-mail: s.gucma@am.szczecin.pl

Key words: marine traffic engineering, sea waterway systems, traffic control, safe ship operation, algorithm Abstract

The article presents an algorithm developed for determining conditions of safe ship operation in a system of sea waterways consisting of three components, or subsystems: waterways, navigation and traffic control. A model of the optimization of sea waterway system parameters is described.

Introduction

For an analysis of sea waterway systems in view of safe ship operation, the following assumptions are made:

1. A system of sea waterways is composed of a number of distinct sections [1]. A waterway is divided into sections by using the following comparative criteria:

– a manoeuvre being performed; – technical parameters of the waterway;

– technical parameters of navigational systems used;

– technical parameters of vessel traffic control system;

– prevailing hydrometeorological conditions; – harbour regulations.

2. Each waterway section consists of three basic subsystems of:

– waterway;

– vessel position determination (navigational subsystem);

– vessel traffic control.

1st section n-th section Administration hydro-meteo conditions other ships in the system tug assistance waterway waterway navigational subsystem navigational subsystem ingoing vessel planned manoeuvre traffic control subsystem traffic control subsystem

Outgoing vessel performed manoeuvre Outgoing vessel performed

manoeuvre

Fig. 1. A general model of waterway system with n sections administration

Stanisław Gucma

56 Scientific Journals 36(108) z. 1

These elements interact with each other and significantly affect the properties of the system.

The function of a waterway system is to provide a ship with conditions for performing a planned manoeuvre by a ship of specific parameters. There-fore, the input quantity is a planned manoeuvre of a ship with specific parameters, the output quantity is a manoeuvre performed by that ship. A general model of waterway system is presented in figure 1.

The construction or change of waterway com-ponent parameters requires that conditions of safe ship operation in the system of sea waterways. Accurately developed conditions for safe ship oper-ation allow to optimize parameters of particular elements of a given system of sea waterways.

Conditions of safe ship operation in a sea waterway system

Operational conditions of sea waterway systems are identified as conditions of safe ship operation on the waterway.

The construction and operation of sea waterway systems generates two basic research problems: 1. Determination of conditions of safe ship

opera-tion on the existing sea waterway.

2. Specification of sea waterway system parame-ters for assumed safe conditions of ship opera-tion.

A system of sea waterways is defined by param-eters of its elements (subsystems). Three elements of sea waterway system in each of the system sec-tions are a function of condisec-tions of safe ship opera-tion. Therefore, the system of i-th section of sea waterway can be written in a matrix form as fol-lows:



i



i i i H I N A , , , , , i i c BT V C L f           

Conditions of safe ship operation on a waterway are these:

Lc − length of a “characteristic ship”;

B − breadth of a “characteristic ship”; T − draft of a “maximum ship”;

Vi − allowable speed of a “maximum ship” in an i-th waterway section;

Ci − tug assistance in an i-th waterway section;

Hi − vector of hydrometeorological conditions

acceptable for a “maximum ship” in an i-th waterway section.



i



f i f i p i w i w i_{V KR V h KR} n d/ , , , , , , H_i   where:

d/n − allowable time of day or night (daylight or

no restrictions);

i _{− minimum underkeel clearance in an i-th} section;

i w

V − maximum wind speed in an i-th section;

i w

KR − wind direction restrictions (if any);

i p

V − maximum current speed in an i-th section;

i f

h − maximum wave height in an i-th section;

i f

KR − wave angle restrictions (if any).

The following matrix forms were adopted in de-scribing the system components for i-th waterway section: Waterway subsystem:            i i i h D l i A where:

li − length of an i-th waterway section;

Di − width of a navigable area of an i-th water-way section;

hi − minimum depth of an i-th waterway

sec-tion. Navigational subsystem:            n i e n i o i n n d d i N where: i n

d − accuracy of an n-th navigational system in an i-th waterway section (standard devia-tion);

n i o

d − availability of an n-th navigational system in an i-th waterway section (dependent on time of day and visibility);

n i e

n

− reliability of an n-th navigational system in an i-th waterway section (technical reliabil-ity).

Systems of position determination are designed for three types of visibility conditions:

– daytime (good visibility); – night time (good visibility); – poor visibility.

Operational guidelines of a waterway under consideration may restrict the number of design conditions for specified ship sizes, for instance: – navigation of ships belonging to a specific size

Conditions of safe ship operation in sea waterway systems

Zeszyty Naukowe 36(108) z. 1 57

– navigation of ships on a given waterway is con-ducted only in good visibility.

Position determination systems for specific visi-bility conditions must be doubled, otherwise a fail-ure of one position determination system creates a threat of navigational disaster (a series of acci-dents at the same time). For each of the three visi-bility conditions two navigational systems have to be designed:

– main system; – additional system.

Vessel traffic control subsystem:

         _i m s i n s o r i I where i n s

r − type of an n-th traffic control system in an i-th waterway section,

i m s

o − type of an m-th hydrometeorological assis-tance system in an i-th waterway section. There are four options in reference to traffic control systems:

1) lack of traffic control system;

2) waterway entry / exit control, information on waterway traffic;

3) control of entry/exit and of ship speed in each waterway section, information on vessel traffic on the waterway;

4) full waterway traffic control;

and the following types of hydrometeorological assistance:

1) information on hydrometeorological conditions prevailing on a waterway;

2) information on hydrometeorological conditions prevailing in each waterway section and opera-tional system of dynamic underkeel clearance determination.

Determination and optimization of sea waterway parameters

Sea waterways are usually built for one-way or two-way traffic, the two cases featuring different conditions of safe ship operation. Safe ship operat-ing conditions that determine parameters of sea waterway elements are specified separately for one-way and two-one-way traffic. Bearing this in mind, it can write:

– for one-way traffic:



i



1 i i i H I N A , , , , , _{1 1 1 1} 1 1 1 1 1 i i c B T V C L f           

– for two-way traffic:



i



i i i H I N A 2 2 2 2 2 2 2 2 2 , , , , , 2 i i c B T V C L f           

When designing a sea waterway operated by one-way and two-way traffic, we choose a set of parameters that will satisfy conditions of safe ship operation for both types of traffic.

Parameters of waterway components for both, one-way and two-way traffic are determined by means of the optimization method where the objec-tive function is the cost of construction and opera-tion of sea waterway system, written down as fol-lows [2]:



1 2 1 2 1 2



min

 A A N N I I S

Z

with one of two constraints:

1)

d

ijk (1 –



)



D

(t)

h

xy

(t)



T

xy

(t)+



xy

(t)

2)

R

l

≤ R

akc

where:

D(t) – navigable area (condition of safe depth at

instant t is satisfied);

dijk(1 – ) – safe manoeuvring area of i-th ship

performing j-th manoeuvre in k-th naviga-tional conditions, determined at a confi-dence level 1 – ;

Z – cost of construction and operation of sea waterway system;

A1 – cost of construction (reconstruction) of a

waterway;

A2 – cost of waterway operation;

N1 – cost of construction of ship position

deter-mination subsystem (navigational systems);

N2 – operating costs of navigational systems; I1 – cost of construction of traffic control

sub-system;

I2 – operating costs of traffic control subsystem; S – ship operating costs related to waterway

passage (pilotage, tug assistance, etc.);

Rl – navigational risk of passing l-th waterway section;

Rakc – acceptable navigational risk;

hxy – depth of area at point x, y;

Txy – ship draft at point x, y;

xy – underkeel clearance at point x, y.

Given that particular costs of construction and operation of the subsystems are a function of pa-rameters of these subsystems, the objective function can have this form:



, ,



min  i k i k i k N I A i Z p(x, y)D(t)

Stanisław Gucma

58 Scientific Journals 36(108) z. 1

with constraints as above, where:

i k

A

– matrix of costs of the construction and

oper-ation of waterway subsystem;

i k

N

– matrix of costs of the construction and

oper-ation of navigoper-ational subsystem;

i k

I

– matrix of costs of the construction and

oper-ation of traffic control subsystem.

The conditions of safe ship operation on an examined waterway for one- and two-way traffic are established following this algorithm:

1. Identify ports and terminals to which the exam-ined waterway is leading.

2. Determine “maximum ships” characteristic of specific ports and terminals.

3. Classify characteristic “maximum ships” by type:

• bulk carriers, tankers; • gas tankers;

• container ships, refrigerated ships, general cargo vessels;

• ferries, ro-ro ships;

• cruise ships, passenger vessels; • other ships.

4. Taking into consideration traffic intensity for each group of vessels, we then define the rele-vant parameters of:

• “maximum ship” in one-way traffic; • “maximum ship” in two-way traffic.

5. Based on marine traffic engineering methods, the following parameters are determined:

• allowable speeds of “maximum ships” in each waterway section (Vi); ships proceed along waterways at varying allowable speeds that depend on the type of area and type of ship. On the one hand, these speeds are af-fected by operating factors, mainly time lim-its imposed on ships such as container carri-ers, Ro-Ro vessels, or gas tankers. On the other hand, there are restrictions resulting from the safety of navigation. Generally ships sail at “service speed in restricted are-as” in remote roadsteads and anchorage ap-proaches or a “reduced speed” developed on fairways. A service speed for restricted areas is not a maximum speed a ship can develop, it is a speed attained with the engines set for “full manoeuvring speed”. A reduced speed, in turn, is used in approach channels and is developed by the engine set for “half ahead” [3];

• allowable hydrometeorological conditions in each waterway section (Hi); an example clearance for a minimum water level is

speci-fied for each ship type, minimum water level, probability of its occurrence and the period of designed waterway operation, for two groups of ships:

– ships that cannot wait for a higher water level (ferries, gas tankers, etc.);

– ships that can wait for a higher water level.

A minimum water level assumed for the former group of vessels is the one occurring within a 20-year period of waterway opera-tion (lifecycle period of this kind of project – construction of a waterway). For the latter group other values can be assumed (e.g. min-imum water level occurring in a 5-year peri-od). For the latter group of vessels in particu-lar we should use the dynamic method of underkeel clearance determination.

Conclusions

The article presents a sea waterway system con-sisting of three elements (subsystems):

– waterway subsystem; – navigational subsystem; – traffic control subsystem.

A sea waterway system is defined with the use of conditions of safe ship operation on that water-way.

An algorithm has been developed for deter-mining conditions of safe ship operation on the examined waterway. Besides, a model for the opti-mization of sea waterway system parameters is described.

The research results have been utilized in the design of approach channels leading to the outer port in Świnoujście, where an LNG terminal is located [4].

References

1. GUCMA S.,ŚLĄCZKA W.,ZALEWSKI P.: Parametry torów

wodnych i systemów nawigacyjnych wyznaczane przy wy-korzystaniu kryteriów bezpieczeństwa nawigacji. Wydaw-nictwo Naukowe Akademii Morskiej w Szczecinie, Szcze-cin 2013.

2. GUCMA S.: Optymalizacja parametrów systemu morskich dróg wodnych w ujęciu inżynierii ruchu morskiego. Mate-riały na Międzynarodową Konferencję Naukową „Trans-port XXI wieku”. Ryn 16–19.09.2013.

3. GUCMA S.,ŚLĄCZKA W.: Target development of the outer

port in Świnoujście – optymalization of parameters and de-termination of operating conditions. 19th International Con-ference on Hydrodynamics in Ship Design – HYDRONAV 2012, Iława.

4. Projekt systemów zapewniających bezpieczną nawigację i obsługę statków LNG na podejściu i w porcie zewnętrz-nym w Świnoujściu. Praca naukowo-badawcza, Akademia Morska w Szczecinie, Szczecin 2012.