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M A R I N P.O. Box 28

6700 AA Wageningen The Netherlands

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E [email protected] I www.marin.nl

BOLLARD PULL JIP

Development of an Industry Standard for Bollard Pull Trials

Joint Industry Project Proposal February 2015

Proposal No. 26756 Bollard Pull JIP Proposal 1

BOLLARD PULL JIP

Development of an Industry Standard for Bollard Pull Trials

Joint Industry Project Proposal


CONTENTS Page

1 BACKGROUND ........................................................................................................ 3

2 OBJECTIVES ........................................................................................................... 6

3 SCOPE OF WORK ................................................................................................... 7 3.1 Review of current bollard pull practice ................................................................. 7 3.2 CFD-Analysis ....................................................................................................... 7 3.3 Model tests ........................................................................................................... 8 3.4 Correction methods .............................................................................................. 9 3.5 Validation by Bollard Pulls ................................................................................... 9 3.6 Guidelines for conduct & measurements ........................................................... 10 3.7 Guidelines for Analysis and Reporting ............................................................... 10 3.8 Software for trial analysis and pull-speed performance ..................................... 11 3.9 JIP Management ................................................................................................ 11

4 DELIVERABLES ..................................................................................................... 12

5 FINANCE ................................................................................................................ 13 5.1 Costs .................................................................................................................. 13 5.2 Contributions ...................................................................................................... 13

6 TIME SCHEDULE .................................................................................................. 14

7 ORGANISATION .................................................................................................... 14

8 CONTACT .............................................................................................................. 14


1 BACKGROUND

Tugs, anchor handlers, suppliers but also other offshore vessels are designed to deliver

a large pulling force at low speed. This key performance is tested by means of a Bollard

Pull where the tow line is connected to a fixed bollard or pile. At maximum developed

power the pulling force is then measured by means of a load cell. This value is

documented on the Bollard Pull Certificate which plays an important role in the sale and

delivery of the tug as well in commercial deployment and contracts.

Although tugs have been around for a long time, a proper standard for conduct,

measurement and analysis of a bollard pull is not available. Bollard Pulls are conducted

in various ways, measurements of developed shaft power and line load are not always

accurate and an analysis procedure of the measured data is lacking.

As a consequence the issued bollard pull certificate, which are the basis for contracting

the tug, is not always reliable. Although class societies issue such bollard pull

certificates, their classification process and notifications are mainly aiming at the safety

of the equipment and not on the tow performance of the tug. There are few bollard pull

procedures available in open literature; In 1961 the BSRA issued their “Code of

procedures for bollard trials of tugs”. In 2002 Steerprop proposed a bollard pull code at

the International Tug & Salvage convention aimed for further unification of procedures

for conduct and analysis of bollard pull trials. The code was published by ITS in

May/June 2002 and is often used as ‘de facto’ standard.

Figure 1: Bollard pull trial under real conditions (wikipedia.org)

The ITS2002 code proposes correction methods for water depth and line length. The

source of these corrections are however unknown and their validation is lacking. In

2013/2014 MARIN conducted scale 1:14 model tests with an ASD tug. Several bollard

situations were evaluated, such as quay side, open pile and systematic variations of the

tow line length, water depth and distance to the quay. The measured bollard pull

showed large discrepancies with the corrections proposed by ITS2002 code for the

effects of line length and water depth. The time traces of the bollard pull also

demonstrated the effect of restricted water in the harbour basin; after a few minutes the

pull decreased due to the water circulation built up in the basin (Figure 1).


Figure 2: time series of tugboat bollard pull performance during tests in restricted waters

The results of the systematic model tests have been discussed with tug operators and

relevant designers, yards and propulsion manufacturers. Based on the practical

experiences over the last decade and the results of the systematic model tests

compared with the ITS 2002 publication, it has been concluded that there is an industry

wide need for transparent and reliable Guidelines for Bollard Pull Trials which will serve

as an industry standard in future.

Another important aspect is the prediction of the bollard pull in the design stage of the

tug and the propellers as the designers/suppliers have to guarantee the bollard pull at

that moment. For this purpose nowadays the open water performance of the propeller

arrangement is predicted by means of Computational Fluid Dynamics. The interaction

with the hull, however is estimated by a thrust deduction factor which is based on model

tests or empirical data. Systematic information on this thrust deduction factor in the

bollard pull condition for various water depths is missing.

Comparisons of full scale bollard pull results with those obtained from open water CFD

and model tests indicate that there are significant scale effects in bollard pull model

tests. A systematic investigation of this scale effect and the development of a dedicated

extrapolation method for ducted propellers and azimuthing thrusters would contribute to

a more reliable prediction of the bollard pull in the design stage.

A further desire of the towing industry is to have an accurate prediction of the pulling

force over the complete speed range of the tug. For actual service the tug normally

operates in the speed range of 4 to 7 knots and it is important to know the performance

of the tug at those speeds.

To resolve the above issues the joint industry project “Bollard Pull JIP” is proposed. In

this way the input, knowledge and experience of all involved parties will be used and a

comprehensive investigation involving CFD, model test and full scale bollard pulls can

be conducted. With the support and co-operation of oil companies, terminal operators,

ports authorities, ship owners, tug operators, tug designers, propulsion manufacturers

and class societies results can be implemented and a worldwide level playing field for

the towing industry can be achieved .

Fx Cardan

Thrust/NOZZ

Trim A

Trim F t=0

s t=40s

t=6min40s

t=9min


Figure 3: Model of ASD tug prior to bollard pull tests in the basin

MARIN has a wide experience in the field CFD, model testing and trials. At the same

time the independent institute has a long track record in joint industry projects related to

tug performance such as Safe Tug, the TRUST-JIP and the Wageningen CD Propeller

Series JIP. In the STA-JIP MARIN has developed a worldwide industry standard for

speed-power trials which has later been adopted by ITTC, ISO and IMO/MEPC and is

now used for both contract delivery and EEDI trials (see www.staimo.org).

http://www.staimo.org/


2 OBJECTIVES

The Bollard Pull Joint Industry Project is aiming at the following:

1. Understanding of the main parameters that affect the bollard pull performance;

2. Systematic data on thrust deduction for various configurations (tugs/propulsors,

push/pull and water depths)

3. Quantification of the scale effects on ducted propellers and the development of an

extrapolation method for this purpose.

4. Develop methods to correct for non-ideal bollard pull conditions such as restricted

waters, quay geometry, line length and angles, wind, current & waves;

5. Guidelines for conduct, measurements, analysis and reporting of bollard pull trials

which will serve as an worldwide industry standard.

6. Develop a software package to analyse the bollard pull performance and to predict

the pull performance over the complete speed range.

Figure 4: wireless load cell on tow line


3 SCOPE OF WORK

3.1 Review of current bollard pull practice

A review of the current available codes and practices for the conduct, measurements

and analysis of bollard pull trials. Including an inventory of available worldwide locations

for bollard pull (above 50 tonf) and the local waterway or port geometry. Collection of

operational experience from the stakeholders. Review of available literature and test

results both at model scale and full scale.

3.2 CFD-Analysis

Nowadays open water performance thrusters and ducted propellers can be computed

with viscous flow numerical models (CFD) ; the so-called RANS codes. In this JIP

extensive Refresco analysis will be conducted to investigate the following:

Bollard pull performance in open water;

Effect of water depth;

Effect of horizontal restrictions of the port basin;

Scale effects.

Bollard pull trials are ‘de facto’ conducted in water ways, ports or near the coast as a

steady state bollard is required for the test. Restrictions of the water in horizontal and

vertical direction affect the achieved bollard pull. The flow into the propulsor can be

blocked in case of a small under keel clearance, and circulation of the water in the port

basin will affect propeller performance.

Based on model tests executed in 2013/2014 and viscous CFD analysis the effects of

various geometrical basins will be evaluated. This information will result in a set of

minimum requirements for the trial location and will be used for the development of

correction methods.

The RANS analysis can be conducted on model scale and full scale and can thus assist

in the investigation of the scale effects experienced in model tests and in the

development of a dedicated extrapolation procedure for bollard pulls.

More over unsteady RANS can be used to model the complete tug including the rotating

propellers. For this purpose use is made of the sliding grid solutions which are available

in the MARIN Refresco code. Results can be used to compare with the model tests to

evaluate the accuracy of RANS and to collect systematic thrust deduction coefficients.

Participants in the JIP will also be offered to use Refresco themselves.


Figure 5: Bollard pull at model scale

3.3 Model tests

Systematic model tests for different tug and propulsor configurations both for the push

and pull modes will be conducted in this JIP to evaluate:

1. Thrust deduction related to water depth

2. Effect of towline length and angles

3. Effect of trim and heading

4. Effect of wind, waves

5. Scale effects

The model tests will be conducted for systematic variations of water depth and towline

length. Also variations in towline angles, tug heading and trim will be investigated.

Several port basin (straight and corner quay side, open water) will be tested for a

selected set up.

The data collected from these systematic tests will provide insight in the importance of

the various parameters and will thus assist in drawing up the guidelines for the conduct

of the bollard pull trials. At the same time this extensive data set will be used to develop

methods for the correction of non-ideal situations encountered during the actual bollard

pulls to arrive at the bollard pull in ideal conditions (calm deep water). These correction

methods will be described in the Guidelines. The correction methods will not be valid

over the complete range of values and therefore this R&D work will also result in limiting

requirements for the above parameters in which bollard pulls can be conducted reliably.

The model test results will also be used to quantify the thrust deduction for the various

tug designs/propulsors as function of water depth. This is important input data for

designers and propulsion suppliers to improve their bollard pull prediction in the design

stage.

Dedicated tests will be conducted to investigate the scale effects in model testing;

results will be compared against the results of the CFD analysis for the same vessel and

conditions. A dedicated extrapolation method for model tests will be developed and

delivered.

As the parameters under investigation are large in number, an adequate model test

program will be drawn up in close co-operation with the participants in this JIP. At this


moment the budget estimate for model tests ensures a realistic program for 2 tug

designs.

Figure 6: test setup for bollard pull tank tests

3.4 Correction methods

Based on the results of the previous tasks with CFD an model tests, practical methods

for the correction of non-ideal situations encountered during the actual bollard pulls to

arrive at the bollard pull in ideal conditions (unrestricted water, no wind, no waves no

current) will be developed. The methods are for implementation in the Guidelines (3.6)

and in the analysis software (3.8) such that they can be applied during the trials with a

minimum input (e.g. main dimensions of tug and propulsors, water depth, line length,

wind speed/ direction and significant wave height and period). The correction methods

will be validated by means of model tests and full scale (3.5) results.

3.5 Validation by Bollard Pulls

As model tests can suffer from scale effects and CFD-modelling for the present

application is rather new, with the assistance of the participating companies several full

scale bollard pulls with existing or new tugs featuring different propulsion arrangements

will be conducted as part of this JIP. The results will be compared with the results of

model tests, CFD and the developed correction methods. The present budget is based

on extensive bollard pulls for some 4 tugs which will be subjected to variations in trim

heading, weather, line length and possible water depth and quay sides.


Figure 7: Full scale bollard pull trials

3.6 Guidelines for conduct & measurements

Based on the results of the previous tasks as well as on the experience with trials, a

document will be developed to provide practical, clear and reliable “Best Practice” for the

preparation, conduct and measurements of bollard pulls.

This document will clearly state which information should be supplied prior to the trials,

the requirements with respect to the location and the limiting weather conditions.

Furthermore minimum water depth, tow line connection length and other essential

parameters will be specified.

The instrumentation, sensors, calibration and data acquisition will be defined.

Finally guidelines for the executing of the bollard pull, power settings, boat control and

duration will be drawn up.

3.7 Guidelines for Analysis and Reporting

Following the results of the forgoing tasks, a document on the guidelines for analysis of

the measured data including the correction methods for non-ideal conditions during the

trials, will be developed.

It is proposed that the Guidelines will be made public; in order to set this as an

worldwide standard.

If supported by the participants, MARIN will initiate and follow-up the procedure to

implement the new Guidelines in an ISO standard.


3.8 Software for trial analysis and pull-speed performance

Similar to the STAIMO software for speed/power trials (see www.staimo.org), the new

guidelines, analysis procedures and correction methods will be implemented in a

practical software package that can be used on board during bollard pull trials and that

result in a concise bollard pull trial report which forms the basis for a bollard pull

certificate to be issued by Class.

Once the bollard pull and the maximum free sailing speed are determined on the basis

of trials, the software will be able to produce the pull force-speed relation over the

complete speed range. This information is practical for the selection and operation of

tugs in the normal speed range of 4 to 7 knots.

The software will be developed and delivered to the participating companies only.

MARIN will maintain and support the software and updates will be delivered free of

charge during the confidentiality period of the JIP (3 years after completion).

3.9 JIP Management

The above scope will be conducted as Joint Industry Project which is open to all

stakeholders. Participants are expected to share their experience and insight in JIP

meetings which will be held every 6 months. Participants may also be selected to

conduct one or more tasks paid by the JIP.

MARIN will act as main contractor and JIP manager and will be responsible for

organising and administrating the project.

JIP Participant Meetings will be held every 6 months in conjunction with the Vessel

Operator Forum (www.vesseloperatorforum.com).

http://www.staimo.org/


4 DELIVERABLES

1. Report Task 1: Review current practice;

2. Report Task 2: CFD results for open water conditions, effects boundary conditions

and scale effects;

3. Report Task 3: Systematic model test results on effect main parameters, thrust

deduction and scale effects for different vessels/propulsor arrangements and

push/pull;

4. Report Task 4: Correction methods for non-ideal conditions;

5. Report Task 5: Results of Bollard Pulls, Correlation & Scale effects;

6. Report Task 6: Guidelines on Conduct of Bollard Pulls;

7. Report Task 7: Guidelines on Analysis of Bollard Pulls;

8. Task 8: Software for Bollard Pull Analysis & Pull-Speed Performance;

9. Summary Report / Publication.


5 FINANCE

5.1 Costs

The budget estimate for the scope of work described, is as follows:

Task Bollard Pull JIP Euro

1 Review of current practice 25,000.-

2 CFD analysis 93,000.-

3 Model testing 190,000.-

4 Development of correction methods for non-ideal conditions 65,000.-

5 Validation by Full Scale Bollard Pulls & scale effects 152,000.-

6 Guidelines for preparation, conduct & measurements 20,000.-

7 Guidelines for analysis and reporting 35,000.-

8 Software for Bollard Pull & Pull-Speed prediction 60,000.-

9 JIP Management 45,000.-

Total in Euro’s 685,000.-

5.2 Contributions

The costs of the JIP will be shared between the participating companies.

Based on the costs and the expected number of participants, the following fees have

been set:

Tug operators, Shipping companies, Yards, Class, Suppliers: 9,000.-/year

SME’s & institutes & authorities: 4,500.-/year

The contributions of the industry will be matched by 23% subsidy provided by the TKI

Water program of the Government of The Netherlands. In addition MARIN will support

this development with a 25% contribution from its research budget.

The expected contributions are thus as follows:

Bollard Pull JIP Contributions Euro

14 Participants @ 9 k x 3 yr 378,000.-

6 SME’s @ 4.5 k x 3yr 81,000.-

TKI subsidy 23 % over above contributions 105,000.-

MARIN contribution 121,000.-

Total in Euro’s 685,000.-


6 TIME SCHEDULE

The following time schedule is proposed:

2015 February: Circulation of draft JIP proposal

April: Open Meeting with interested parties

May: Final JIP Proposal & Participation Agreement

June/July: Sign in of participants

September: Kick-off

2017 December; Delivery of final results; Completion of JIP

2015 2016 2017

Task Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

1

2

3

4

5

6

7

8

7 ORGANISATION This JIP is aiming a the participation of all stakeholders i.e. oil companies, terminal

operators, port authorities, ship owners, tug operators, tug designers, propulsion

manufacturers and class societies. These organisations confirm their participation by

signing the Bollard Pull JIP Participation Agreement with MARIN. This agreement

ensures that all results are kept confidential during the confidentiality period that ends 3

years after completion of the project. It is envisaged that the Guidelines will be published

earlier with the consent of the participants. In case the Guidelines will be published as

an ISO standard this will also be a requirement.

The work will be conducted by MARIN in close co-operation with participating

companies. Tasks in the project may be assigned to participating companies or sub

contractors with the agreed payment by the JIP.

8 CONTACT

For further information on the Bollard Pull JIP please contact MARIN Trials & Monitoring:

Thijs Hasselaar; email [email protected]; tel +31 317 493224

Henk van den Boom; email [email protected]; tel +31 317 493353

mailto:[email protected]

mailto:[email protected]

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