Ittc Snames_sea Trial

ITTC – Recommended 7.5-04 -01-01.1

Procedures and Guidelines of 10

Full Scale Measurements Speed and Power Trials

Preparation and Conduct of Speed/Power Trials

Effective Date 2005

Revision03

Updated / Edited by Approved

Specialist Committee on Powering Perform-ance of 24th ITTC

24th ITTC 2005

Date 2005 Date 2005

Table of Contents

1. PURPOSE ..............................................2

2. DEFINITIONS.......................................2

3. RESPONSIBILITIES............................3

3.1 Shipbuilders Responsibilities............3

3.2 The Trial Team ..................................4

4. PROCEDURES......................................4

4.1 Trial Preparation...............................4 4.1.1 Shipbuilder’s Support Requirement:4 4.1.2 Space Requirements ........................4

4.2 Ship Inspection...................................5 4.2.1 Preparation for the trials ..................5 4.2.2 Ship Inspection ................................5 4.2.3 Reporting of Results and

Distribution of Information .............5

4.3 Hull- and Propulsor Survey..............5

4.4 Instrumentation Installation and Calibration .........................................5

4.4.1 Instrumentation Installation.............5 4.4.2 Instrumentation Calibration Check .6

4.5 Trial Conditions.................................6 4.5.1 Wind: ...............................................8 4.5.2 Sea State: .........................................8 4.5.3 Current:............................................8

4.6 Trial Conduct: ...................................8

5. REFERENCES ....................................10





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1. PURPOSE

The general purpose of this procedure is to define basic requirements for the preparation and conduct of speed trials.

The primary purpose of speed trials is to determine ship performance in terms of speed, power and propeller revolutions under pre-scribed ship conditions, and thereby verify the satisfactory attainment of the contractually stipulated ship speed.

The applicability of this procedure is lim-ited to commercial ships of the displacement type.

The procedure is

• to provide guidelines to document the trial preparation prior to the conduct of a full scale Speed/Power trial,

• to define the responsibility sharing among the parties who take part in the sea trial for the smooth preparation and execution of the speed trial

• to establish a guideline for conducting inspections for the purpose of installing instrumentation prior to the conduct of a full scale Speed/Power trial,

• to establish a baseline of the ship hull and propulsor condition prior to the conduct of a full-scale Speed/Power trial;(hull and propulsor surveys are

recommended to allow an evaluation of the trial results for scientific purposes),

• to install and calibrate trial instrumenta-tion for full scale Speed/Power trials,

• to define acceptable limits for trial con-ditions needed to validate hydrody-namic design and/or satisfy contractual requirements,

for acceptable conduct of each speed trial.

2. DEFINITIONS

• Ship Speed is that realized under the con-tractually stipulated conditions. Ideal condi-tions to which the speed would be corrected would be

• no wind (or maximum wind speed ac-cording to Beaufort 2)

• no waves (or waves with maximum wave heights and wave periods accord-ing to Beaufort 1)

• no current

• deep water

• smooth hull and propeller surfaces

• Docking Report: Report that documents the condition of the ship hull and propul-sors (available from the most recent dry - docking).

• Trial Agenda: Document outlining the scope of a particular Speed/Power trial. This document contains the procedures on





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how to conduct the trial and table(s) por-traying the runs to be conducted.

• Trial Log: For each run, the log contains the run number, type of maneuver, ap-proach speed by log, approach shaft speed, times when the maneuvers start and stop, and any comments about the run.

• Propeller Pitch: the design pitch also for controllable pitch propellers.

• Running Pitch: the operating pitch of a CPP

• Brake Power: Power delivered by the out-put coupling of the propulsion machinery before passing through any speed reducing and transmission devices and with all con-tinuously operating engine auxiliaries in use.

• Shaft Power: Net power supplied by the propulsion machinery to the propulsion shafting after passing through all speed-reducing and other transmission devices and after power for all attached auxiliaries has been taken off.

3. RESPONSIBILITIES

3.1 Shipbuilders Responsibilities

• The Shipbuilder has the responsibility for planning, conducting and evaluating the tri-als.

• Speed – Power - Trials may be conducted by institutions acknowledged as competent to perform those trials, as agreed between the Shipbuilder and the Ship owner

• The Shipbuilder has to provide all permits and certificates needed to go to sea.

• The Shipbuilder is responsible to ensure that all qualified personnel, needed for op-erating the ship and all engines, systems and equipment during the trials have been ordered.

• The Shipbuilder is responsible to ensure that all regulatory bodies, Classification Society, Ship Owner, ship agents, suppliers, subcontractors, harbor facilities, delivering departments of provisions, fuel, water, tow-ing, etc., needed for conducting the sea tri-als, have been informed and are available and on board, if required.

• It is the Shipbuilder’s responsibility that all safety measures have been checked and all fixed, portable and individual material (for crew, trial personnel and guests) is on board and operative.

• It is the Shipbuilder’s responsibility that dock trials of all systems have been exe-cuted as well as all alarms, warning and safety systems.

• It is the Shipbuilder’s responsibility that an inclining test has been performed and/or at least a preliminary stability booklet has been approved, covering the sea trial condi-tion, in accordance with the 1974 SOLAS Convention.

• The Shipbuilder is responsible for the over-all trial coordination between the ship's crew, trial personnel, and the owner repre-sentative. A pre-trial meeting between the trial team, owner and the ship’s crew will be held to discuss the various trial events and to resolve any outstanding issues.





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• The Shipbuilder has, if necessary, to ar-range for divers to inspect the ship’s hull and propellers.

• The Trial Leader is the duly authorized (shipbuilder’s representative) person re-sponsible for the execution of all phases of the Speed/Power trials including the pre-trial preparation.

3.2 The Trial Team

The trial team is responsible for correct measurements and analysis of the measured data according to the state of the art.

The trial team is responsible for the follow-ing:

a. Conduct ship inspection, if possible or necessary.

b. Provide, install and operate all required trial instrumentation and temporary ca-bling.

c. If previously arranged, provide the ship master and owner’s representative with a preliminary data package before de-barking. The contents of the data pack-age will be determined in consultation with the owner’s representative at the initial pre-trial briefing.

d. Provide a final report after completion of the trials in accordance with any agreement between the shipbuilder and the ship owner.

4. PROCEDURES

4.1 Trial Preparation

4.1.1 Shipbuilder’s Support Requirement:

Prior to the trials the required instrumenta-tion has to be installed. The assistance of the ship’s or shipbuilder’s crew will be required when making electrical connections to the ship's systems and circuits such as heading, wind speed, wind direction, and rudder angle synchronous repeaters. The following support is requested from the Shipbuilder to properly prepare for the trials:

a. Provide access to the ship for trial in-strumentation.

b. Assistance is required for the following electrical connections: • Gyrocompass • Wind meter • Rudder angle indicator • Log Speed • Propeller Pitch

c. Vary the output level of each of the above measurement sources to ensure the proper operation and alignment of the test instrumentation

4.1.2 Space Requirements

Spaces and an electric supply adequate for the trial equipment will be required for the trial instrumentation and computers.





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4.2 Ship Inspection

There are three stages of a ship inspection: in-house preparation, the actual inspection, and the reporting of results and distribution of in-formation to the various parties involved in the trial.

4.2.1 Preparation for the trials

• Review shafting dimensions, propulsion plant specifications, etc.

• Review trials agenda, if available.

4.2.2 Ship Inspection

• Inspect hull- and propeller surface con-dition, if possible.

• Inspect ship’s instrumentation for ac-cessibility.

• Determine routes for cable runs/data transfer conduits between trial room and bridge or control area.

• Contact the Engineer on duty to discuss trial instrumentation requirements. In-spect machinery spaces as applicable.

4.2.3 Reporting of Results and Distribution of Information

Document all pertinent information related to the ship inspection

a) Last date of cleaning.

b) Means of cleaning.

c) Propeller roughness measurement, if available, which should include aver-age, standard deviation, distribution

along the blades, and existing physical damage.

d) For a clean hull; documentation indi-cating manufacturer and kind of paint used, paint layer thickness and, if avail-able, roughness measurements (average, standard deviation, and distribution along the hull) should be provided. The majority of this information may be contained in the docking report.

e) For a dirty hull, documentation indi-cating visual observations of any foul-ing and date of last dry-docking should be provided.

4.3 Hull- and Propulsor Survey

A roughness survey is recommended to document the conditions of the ship hull, ap-pendages, and propulsor(s) prior to the start of the full-scale speed/ power trial. Cleaning may be required if fouling is found to be such that it would bias the trial data.

Ideally, roughness surveys should be con-ducted prior to the trials. The average hull roughness should not exceed 250 µm (µ = 1x10-6 m) (6.35 mils) and the average propul-sor roughness level should not be greater than 150 µm (3.81 mils).

4.4 Instrumentation Installation and Cali-bration

4.4.1 Instrumentation Installation

The installation of instrumentation should be scheduled at a time of minimal conflict with ship operations.





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The bias limits of the instrumentation used for the measurements should be known and as-sessed.

The instrumentation used for the on-board-measurements must be calibrated before appli-cation on board. If this is not possible, for some reason, the consequences of this should be highlighted in the final trial report. Electrical calibration is recommended for the torque measurement device and, in case of use during the sea trials, for the thrust measurement device. Further a calibration should be done for the pick ups and the respective amplifiers used for the measurement of the rate of revolutions. A “calibration” of a (differential) GPS-System is not possible without excessive measures, but at least the function of the device should be checked before use on board.

If portable radar tracking or (differential) GPS is utilized, a Receiver/Transmitter (R/T) unit or GPS antenna is to be installed. In case the soft ware program used for the evaluation of the data received does not allow for varying positions on the uppermost deck of the ship the antenna should be placed in a location along the ship’s centerline as close to the ship’s CG as possible. This location will ideally be lo-cated on a mast or site that is clear of obstruc-tions, such as the ship’s superstructure.

4.4.2 Instrumentation Calibration Check

All shipboard signals to be recorded during the trials must be adjusted to zero or should have their zero value checked (e.g. for a (D) GPS-device) after the instrumentation installa-tion is completed and prior to the trials. The zero values of the torsiometers, the thrust measurement devices and the devices for the

measurement of the rates of revolutions must be checked before the trial runs start and after they have been finished.

As part of the pre-trial calibration, the tor-sion meters zero torque readings must be de-termined since there is a residual torque in the shaft, which is resting on the line shaft bearings. This might be done in different ways; one pos-sible way is to use the jacking motors. The shaft is jacked both ahead and astern and the average of the readings noted. The zeroes are set at the midpoint of the torque required to jack each shaft ahead and the torque required to jack each shaft astern. An allowance is nor-mally made for frictional losses in the stern tube bearings.

As part of the pre-trial calibration for a ship equipped with controllable pitch propellers, maximum ahead pitch, the design pitch and the maximum astern pitch should be determined and then the ship indicators should be adjusted to reflect the measurement.

4.5 Trial Conditions

Speed/Power trials require accurate position data. The use of (D) GPS provides great lati-tude in choosing a trial site. Regardless of the instrumentation utilized for obtaining posi-tional data, the operational area should be free from substantial small boat traffic.

The tracking range should be agreed be-tween the Trial Director and the ship’s master.

Draft, trim and displacement of the ship on trials should be obtained by averaging the ship draft mark readings. The ship should be brought into a condition that is as close as pos-sible to the contract condition and/or the condi-





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tion on which model tests have been carried out. This will allow for the correction of the dis-placement and trim with respect to the trials that were conducted and will be applicable to the suggestions outlined in the ITTC Procedure for the Analysis of Speed/Power Trial Data.

Draft, trim and displacement should be ob-tained at the beginning and at the end of the trial. This may be accomplished using a load-ing computer or by taking a second draft read-ing. The accuracy of the draft readings and the method used to establish draft and displace-ment underway will be compared in port by di-rect draft readings both port and starboard in conjunction with a liquid load calculation.

Displacement should be derived from the hydrostatic curves by utilizing the draft data and the density of the water.

Environmental factors may significantly in-fluence the data obtained during sea trials; con-sequently, these factors should be monitored and documented to the greatest extent possible:

• High wind and sea states can force the use of excessive rudder to maintain heading, and thus cause excessive fluc-tuations in shaft torque, shaft speed and ship speed.

• Sea states of 3 or less and a true wind speed below Beaufort 6 (20 Kn) are the desired conditions for sea trials. When working under the time constraints of a contract, corrections to the trials data can be made in accordance with the rec-ommendations provided in the ITTC Procedure for the Analysis of Speed/Power Trial Data for sea states less than or equal to 5. For sea states

greater than 5, corrections to the trials data can be applied but are not consid-ered reliable from a scientific stand-point.

• The local seawater temperature and spe-cific gravity at the trial site are recorded to enable the calculation of ship's dis-placement.

• An acceptable minimum water depth for the trials where the data do not need to be corrected for shallow water can be calculated using: h > 6.0(Am)0.5 and h > 0.5 V2 (1) with Am= midship section area, [m2] V= ship speed, [m/s] The larger of the 2 values obtained from the two equations should be used.

• Current speed and direction should be determined in the test area by prognos-tic analysis. When current speed and di-rection is unknown, the ship’s global drift (also including wind effect) in some cases might be determined by a 360° turning test conducted at low ahead speed to magnify any environ-mental effect.

• The runs should be conducted into and against the waves; i.e., head and follow-ing seas, respectively. To ensure that tests are performed in comparable con-ditions, the data between reciprocal runs should be reviewed for consistency and/or anomalies. Individual speed runs conducted in the same conditions should be averaged with their reciprocal runs to take into account global drift.





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In accordance with ISO 15016 the follow-ing, general recommendations can be given:

4.5.1 Wind:

Wind speed and direction shall be measured as relative wind; continuous recording of rela-tive wind during each run is recommended. Care has to be taken whether the data derived from the wind indicator are reliable; checks, such as parallel measurements with a portable instrument, comparison of the data received from the wind indicator with wind speeds and directions received from local weather stations sufficiently close to the actual position of the ship or, if possible, calibration of the wind in-dicator (taking into consideration the effects of boundary layers of the superstructure on the measured values) in a wind tunnel are recom-mended.

It is suggested that wind force during the trial runs under no conditions should be higher than

• Beaufort 6 for ships with lengths equal or exceeding 100m and

• Beaufort 5 for ships shorter than 100m.

4.5.2 Sea State:

If possible, instruments such as buoys or in-struments onboard ships (e.g. seaway analysis radar) should be used to determine the wave height, wave period and direction of seas and swell. Considering usual practice the wave heights may be determined from observations by multiple, experienced observers, including the nautical staff on board.

During the trial runs the total wave height (double amplitude), which allows for the wave heights of seas and swell (see ISO 15016), should not exceed

• 3m for ships of 100m length and more and

• 1,5m for ships with lengths smaller than 100m

4.5.3 Current:

Current speed and direction shall be ob-tained either as part of the evaluation of run and counter-run of each double run, by direct measurement with a current gauge buoy or by use of nautical charts of the respective trial area. It is recommended to compare measured data with those included on the nautical charts.

4.6 Trial Conduct:

All speed trials shall be carried out using double runs, i.e. each run is followed by a re-turn run in the opposite direction, performed with the same engine settings.

The number of such double runs should not be less than three. This three runs should be at different engine settings.

The time necessary for a speed run depends on the ship’s speed, size and power. Steady state conditions should be achieved before the speed runs start. It is recommended that the time of one run should be as long as possible but should at least be 10 min.

The ideal path of a ship in a typical speed/power maneuver is shown in Figure 1:





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Steady ApproachMin 10 min

Steady Approach

Min. 10 min

Figure 1

Prior to the trial, the data specified below shall be recorded, based on measurements where relevant:

• Date • Trial area • Weather conditions • Air temperature • Mean water depth in the trial area • Water temperature and density • Draughts • Corresponding displacement • Propeller pitch in the case of a CPP

It is recommended to retain a record of the following factors, which should prove useful for verifying the condition of the ship at the time of the speed trial:

• Time elapsed since last hull and propel-ler cleaning

• Surface condition of hull and propeller.

The following data should be monitored and recorded on each run:

Clock time at commencement • Time elapsed over the measured dis-

tance • Ship heading • Ship’s speed over ground • Propeller rate of revolutions • Propeller shaft torque and/or brake

power • Water depth • Relative wind velocity and direction • Air temperature • Observed wave height (or: wave height

corresponding to observed and/or agreed wind conditions)

• Rudder angle • Ship position and track





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Data such as ship’s speed, rate of revolu-tions of the propeller, torque, rudder angle and drift angle to be used for the analyses shall be the average values derived on the measured distance.

5. REFERENCES

(1) ISO 15016, Ships and marine technology – Guidelines for the assessment of speed and power performance by analysis of speed trial data

(2) ITTC Procedure for the Analysis of Speed/Power Trial Data

(3) ISO 19019

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