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232(65) 2013 Guidelines for determing minimum propulsion power to maintain the manoeuvrability of ships in adverse conditions
Geldigheid:17-05-2013 t/m Status: Geldig vandaag

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2013 Interim guidelines for determing minimum propulsion power to maintain the manoeuvrability of ships in adverse conditions

  dd-mm-yyyy = Entry into force
DocumentMEPC/Res.232(65)17-05-2013
RevokesMSC-MEPC.2/Circ.1116-05-2013 Expired

Ingangsdatum: 17-05-2013

2013 Interim guidelines for determing minimum propulsion power to maintain the manoeuvrability of ships in adverse conditions

  dd-mm-yyyy = Entry into force
DocumentMEPC/Res.232(65)17-05-2013
RevokesMSC-MEPC.2/Circ.1116-05-2013 Expired

Annex

Ingangsdatum: 17-05-2013

0 - PurposePurpose Purpose

The purpose of these interim guidelines is to assist Administrations and recognized organizations in verifying that ships, complying with EEDI requirements set out in regulations on Energy Efficiency for Ships, have sufficient installed propulsion power to maintain the manoeuvrability in adverse conditions, as specified in regulation 21.5 in chapter 4 of MARPOL Annex VI.

1 - DefinitionDefinition Definition DefinitionDefinitionDefinition

1.1 "Adverse conditions" mean sea conditions with the following parameters:

Significant wave height hs, m
Peak wave period TP, s
Mean wind speed Vw, m/s

5.5

 

7.0 to 15.0

19.0


JONSWAP sea spectrum with the peak parameter of 3.3 is to be considered for coastal waters.

1.2 The following adverse condition should be applied to ships defined as the following threshold value of ship size.

Ship length, m

Significant wave
height hs, m

Peak wave period
TP, s

Mean wind speed
Vw, m/s

Less than 200

 

4.0

7.0 to 15.0

15.7

200 <Lpp< 250

 

Parameters linearly interpolated depending on ship's length

More than Lpp = 250

 

Refer to paragraph 1.1


2 - Applicability1

2.1 These guidelines should be applied in the case of all new ships of types as listed in table 1 of appendix required to comply with regulations on Energy Efficiency for Ships according to regulation 21 of MARPOL Annex VI.

2.2 Notwithstanding the above, these guidelines should not be applied to the ships with un-conventional propulsion system such as pod propulsion.

2.3 These guidelines are intended for ships in unrestricted navigation; for other cases, the Administration should determine appropriate guidelines, taking the operational area and relevant restrictions into account.


 

3 Assessment procedure

3.1 The assessment can be carried out at two different levels as listed below:

  1. Minimum power lines assessment; and

  2. Simplified assessment.

3.2 The ship should be considered to have sufficient power to maintain the manoeuvrability in adverse conditions if it fulfils one of these assessment levels.

 

4 - Assessment level 1 - minimum power lines assessment

4.1 If the ship under consideration has installed power not less than the power defined by the minimum power line for the specific ship type, the ship should be considered to have sufficient power to maintain the manoeuvrability in adverse conditions.

4.2 The minimum power lines for the different types of ships are provided in the appendix.

 

5 - Assessment level 2 - simplified assessment

5.1 The methodology for the simplified assessment is provided in the appendix.

5.2 If the ship under consideration fulfils the requirements as defined in the simplified assessment, the ship should be considered to have sufficient power to maintain the manoeuvrability in adverse conditions.

 

6 - Documentation

6.1 Test documentation should include at least, but not be limited to, a:

  1. description of the ship's main particulars;

  2. description of the ship's relevant manoeuvring and propulsion systems;

  3. description of the assessment level used and results; and

  4. description of the test method(s) used with references, if applicable.


1These Interim Guidelines are applied to ships required to comply with regulations on Energy Efficiency for Ships according to regulation 21 of MARPOL Annex VI during Phase 0 (i.e. for those ship types as in table 1 of appendix with the size of equal or more than 20,000 DWT).

Appendix

Ingangsdatum: 17-05-2013

Appendix procedures to maintain the manoeuvrability under adverse conditions, applicable during phase 0 of the EEDI implementation

1 Scope

1.1 The procedures as described below are applicable during Phase 0 of the EEDI implementation as defined in regulation 21 of MARPOL Annex VI (see also paragraph 0 –Purpose of these interim guidelines).

 

2 - Minimum power lines

2.1 The minimum power line values of total installed MCR, in kW, for different types of ships should be calculated as follows:

Minimum Power Line Value = a x (DWT) + b

Where:

DWT is the deadweight of the ship in metric tons; and a and b are the parameters given in table 1 for tankers, bulk carriers and combination carriers.

Table 1: Parameters a and b for determination of the
minimum power line values for the different ship types

Ship Type

a

b

Bulk Carriers

0.0687

2924.4

Tankers

0.0689

3253.0

Combination Carriers

see tankers above

The total installed MCR of all main propulsion engines should not be less than the minimum power line value, where MCR is the value specified on the EIAPP Certificate.

 

3 - Simplified assessment

3.1 The simplified assessment procedure is based on the principle that, if the ship has sufficient installed power to move with a certain advance speed in head waves and wind, the ship will also be able to keep course in waves and wind from any other direction. The minimum ship speed of advance in head waves and wind is thus selected depending on ship design, in such a way that the fulfilment of the ship speed of advance requirements means fulfilment of course-keeping requirements. For example, ships with larger rudder areas will be able to keep course even if the engine is less powerful; similarly, ships with a larger lateral windage area will require more power to keep course than ships with a smaller windage area.

3.2 The simplification in this procedure is that only the equation of steady motion in longitudinal direction is considered; the requirements of course-keeping in wind and waves are taken into account indirectly, by adjusting the required ship speed of advance in head wind and waves.

3.3 The assessment procedure consists of two steps:

  1. definition of the required advance speed in head wind and waves, ensuring course-keeping in all wave and wind directions; and

  2. assessment whether the installed power is sufficient to achieve the required advance speed in head wind and waves.

 

Definition of required ship speed of advance

3.4 The required ship advance speed through the water in head wind and waves, Vs, is set to the larger of:

  1. minimum navigational speed, Vnav; or

  2. minimum course-keeping speed, Vck.

3.5 The minimum navigational speed, Vnav, facilitates leaving coastal area within a sufficient time before the storm escalates, to reduce navigational risk and risk of excessive motions in waves due to unfavourable heading with respect to wind and waves. The minimum navigational speed is set to 4.0 knots.

3.6 The minimum course-keeping speed in the simplified assessment, Vck, is selected to facilitate course-keeping of the ships in waves and wind from all directions. This speed is defined on the basis of the reference course-keeping speed Vck, ref, related to ships with the rudder area AR equal to 0.9 per cent of the submerged lateral area corrected for breadth effect, and an adjustment factor taking into account the actual rudder area:

Vck = Vck, ref - 10.0 x (AR% - 0.9)

(1)


where Vck in knots, is the minimum course-keeping speed, Vck, refin knots, is the reference course-keeping speed, and AR% is the actual rudder area, AR, as percentage of the submerged lateral area of the ship corrected for breadth effect, ALS, cor, calculated as AR% = AR/ALS, cor ·100%. The submerged lateral area corrected for breadth effect is calculated as ALS, cor = LppTm(1.0+25.0(Bwl/Lpp)2), where Lpp is the length between perpendiculars in m, Bwl is the water line breadth in m and Tm is the draft a midship in m. In case of high-lift rudders or other alternative steering devices, the equivalent rudder area to the conventional rudder area is to be used.

3.7 The reference course-keeping speed Vck, ref  for bulk carriers, tankers and combination carriers is defined, depending on the ratio AFW/ALW  of the frontal windage area, AFW, to the lateral windage area, ALW, as follows:

  1. 9.0 knots for AFW/ALW = 0.1 and below and 4.0 knots for AFW/ALW = 0.40 and above; and

  2. linearly interpolated between 0.1 and 0.4 for intermediate values of AFW/ALW.

Procedure of assessment of installed power

3.8 The assessment is to be performed in maximum draught conditions at the required ship speed of advance, Vs, defined above. The principle of the assessment is that the required propeller thrust, T in N, defined from the sum of bare hull resistance in calm water Rcw, resistance due to appendages Rapp, aerodynamic resistance Rair, and added resistance in waves Raw, can be provided by the ship's propulsion system, taking into account the thrust deduction factor t:

T = (Rcw + Rair + Raw + Rapp ) /(1 - t )

(2)

 

3.9 The calm-water resistance for bulk carriers, tankers and combination carriers can be calculated neglecting the wave-making resistance as , where k is the form factor, , is the frictional resistance coefficient, Re = VsLpp / is the Reynolds number,  is water density in kg/m3, S is the wetted area of the bare hull in m2, Vs is the ship advance speed in m/s, and  is the kinematic viscosity of water in m2/s.

3.10 The form factor k should be obtained from model tests. Where model tests are not available the empirical formula below may be used:

(3)

where CB is the block coefficient based on Lpp.

 

3.11 Aerodynamic resistance can be calculated as   where Cair is the aerodynamic resistance coefficient, is the density of air in kg/m3AF is the frontal windage area of the hull and superstructure in m2, and Vw rel is the relative wind speed in m/s, defined by the adverse conditions in paragraph 1.1 of the interim guidelines, Vw, added to the ship advance speed, Vs. The coefficient Cair can be obtained from model tests or empirical data. If none of the above is available, the value 1.0 is to be assumed.

 

3.12 The added resistance in waves, Raw , defined by the adverse conditions and wave spectrum in paragraph 1 of the interim guidelines, is calculated as:

(4)


where  is the quadratic transfer function of the added resistance, depending on the advance speed Vs in m/s, wave frequency in rad/s, the wave amplitude,  in m and the wave spectrum, in m2s. The quadratic transfer function of the added resistance can be obtained from the added resistance test in regular waves at the required ship advance speed Vs as per ITTC procedures 7.5-02 07-02.1 and 7.5-02 07-02.2, or from equivalent method verified by the Administration.

 

3.13 The thrust deduction factor t can be obtained either from model tests or empirical formula. Default conservative estimate is t=0.7w, where w is the wake fraction. Wake fraction w can be obtained from model tests or empirical formula; default conservative estimates are given in table 2.

Table 2: Recommended values for wake fraction w

Block
coefficient

One
propeller

Two
propellers

0.5

0.14

0.15

0.6

0.23

0.17

0.7

0.29

0.19

0.8 and
above

0.35

0.23



3.14 The required advance coefficient of the propeller is found from the equation:

(5)


where DP is the propeller diameter, KT (J) is the open water propeller thrust coefficient, J = uaInp. and ua = Vs (1-w). J can be found from the curve of (J)/J2.

 

3.15 The required rotation rate of the propeller, n, in revolutions per second, is found from the relation:

(6)

 

3.16 The required delivered power to the propeller at this rotation n, PD in watts, is then defined from the relation:

(7)

where KQ(J) is the open water propeller torque coefficient curve. Relative rotative efficiency is assumed to be close to 1.0.

 

3.17 For diesel engines, the available power is limited because of the torque-speed limitation of the engine, Q < Qmax (n) , where Qmax (n) is the maximum torque that the engine can deliver at the given propeller rotation rate n. Therefore, the required minimum installed MCR is calculated taking into account:

  1. torque-speed limitation curve of the engine which is specified by the engine manufacturer; and

  2. transmission efficiency which is to be assumed 0.98 for aft engine and 0.97 for midship engine, unless exact measurements are available.
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