4200 cubic meter lng bunkering vessel concept design · 2021. 1. 5. · dr. james a. lisnyk student...
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DR. JAMES A. LISNYK
STUDENT SHIP DESIGN COMPETITION 2020
4200 CUBIC METER LNG BUNKERING VESSEL
CONCEPT DESIGN
ALEXANDER BIDWELL, OSCAR COMO, LUKE HERBERMANN, & BENJAMIN HUNT
WEBB INSTITUTE CLASS OF 2021
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TABLE OF CONTENTS
LIST OF TABLES ........................................................................................................................ III
LIST OF FIGURES ...................................................................................................................... IV
STUDENT CERTIFICATION ...................................................................................................... V
ACKNOWLEDGEMENTS .......................................................................................................... VI
DESIGN REQUIREMENTS .......................................................................................................... 1
REPORT SUMMARY & TABLE OF PRINCIPAL CHARACTERISTICS ................................ 2
CONCEPT SELECTION AND INITIAL DEFINITION............................................................... 3
HULL FORM DEVELOPMENT ................................................................................................... 9
SECTIONAL AREA CURVE ........................................................................................................ 9
LINES PLAN ................................................................................................................................ 10
CURVES OF FORM .................................................................................................................... 10
SPEED AND POWER ESTIMATE ............................................................................................. 10
GENERAL ARRANGEMENT .................................................................................................... 11
AREA VOLUME REPORT ......................................................................................................... 15
CAPACITY PLAN ....................................................................................................................... 15
STRUCTURAL DESIGN ............................................................................................................. 15
PROPULSION PLANT TRADE-OFF STUDY ........................................................................... 22
MACHINERY ARRANGEMENT ............................................................................................... 28
H, M, AND E SYSTEMS AND EQUIPMENT ........................................................................... 29
CARGO TRANSFER SYSTEM .................................................................................................. 33
ELECTRICAL SYSTEM ............................................................................................................. 48
ENDURANCE CALCULATION ................................................................................................ 51
WEIGHT ESTIMATE .................................................................................................................. 53
STABILITY .................................................................................................................................. 57
SEAKEEPING ANALYSIS ......................................................................................................... 59
MANNING ESTIMATE .............................................................................................................. 60
COST ANALYSIS........................................................................................................................ 61
DESIGN COMPLIANCE MATRIX ............................................................................................ 63
RISK ASSESSMENT AND SUGGESTIONS FOR FUTURE WORK ...................................... 63
REFERENCES ............................................................................................................................. 65
: FINAL DESIGN REQUIREMENTS .............................................................. A-1
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: ROUTE ANALYSIS ........................................................................................ B-1
: LINES PLAN ................................................................................................... C-1
: CURVES OF FORM........................................................................................ D-1
: GENERAL ARRANGEMENT ......................................................................... E-1
: AREA AND VOLUME REPORT .................................................................... F-1
: CAPACITY PLAN .......................................................................................... G-1
: STRUCTURAL MIDSHIP SECTION ............................................................ H-1
: STRUCTURAL CALCULATIONS ................................................................... I-1
: MACHINERY ARRANGEMENT .................................................................... J-1
: CARGO TRANSFER SYSTEM DRAWINGS ............................................... K-1
: FLOW CALCULATIONS ................................................................................ L-1
: ABS PIPE WALL THICKNESS CALCULATIONS .................................... M-1
: ELECTRICAL SYSTEM CALCULATIONS ................................................. N-1
: ENDURANCE CALCULATIONS ................................................................. O-1
: WEIGHT ESTIMATE ....................................................................................... P-1
: STABILTIY CALCULATIONS ..................................................................... Q-1
: FLOODABLE LENGTH CURVES ................................................................ R-1
: SEAKEEPING CALCULATIONS ................................................................... S-1
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LIST OF TABLES
Table 1. Principal Particulars .......................................................................................................... 3 Table 2. Excel Model Example ....................................................................................................... 6 Table 3. Initial Parametric Analysis Results ................................................................................... 9 Table 4. Designed and Required Section Modulus and Moment of Inertia .................................. 22
Table 5. Fuel Type Pros and Cons ................................................................................................ 24 Table 6. Drive Type Pros and Cons .............................................................................................. 25 Table 7. Propulsor Type Pros and Cons........................................................................................ 27 Table 8. Wärtsilä Generator Configuration .................................................................................. 28 Table 9. Mission Specific Equipment ........................................................................................... 33
Table 10. Summary of Flowrates and Heads of Governing Cases ............................................... 38 Table 11. Pipe Characteristics....................................................................................................... 42
Table 12. EPLA Results ................................................................................................................ 48 Table 13. Wärtsilä 6L20DF Specific Fuel Consumption.............................................................. 51 Table 14. Wärtsilä 8L34DF Specific Fuel Consumption.............................................................. 51 Table 15. Design Transit Fuel Consumption ................................................................................ 52
Table 16. Daily Fuel Consumption ............................................................................................... 52 Table 17. Voyage Fuel Consumption ........................................................................................... 53
Table 18. Weights and Centers Estimate Summary...................................................................... 53 Table 19. General Operability Limiting Criteria for Ships (NORDFORSK, 1987) ..................... 59 Table 20. Manning Estimate ......................................................................................................... 61
Table 21. Cost Estimate ................................................................................................................ 62 Table 22. Design Compliance Matrix ........................................................................................... 63
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LIST OF FIGURES
Figure 1. Route Analysis Solution .................................................................................................. 4 Figure 2. Generated Plot Example .................................................................................................. 7 Figure 3. Calculations Sheet Example ............................................................................................ 8 Figure 4. Sectional Area Curve ..................................................................................................... 10
Figure 5. Orca3D Holtrop Analysis Results ................................................................................. 11 Figure 6 KHOBRA Transfer System ............................................................................................ 13 Figure 7. KLAW LNG Transfer System....................................................................................... 13 Figure 8. Fender Davit .................................................................................................................. 14 Figure 9: Longitudinal Weight Curve ........................................................................................... 18
Figure 10. Buoyancy Curve .......................................................................................................... 18 Figure 11: Longitudinal Net Load Curve...................................................................................... 19
Figure 12: Shear Force and Bending Moment Diagram ............................................................... 20 Figure 13. ABS Hogging and Sagging Moment calculation ........................................................ 20 Figure 14. ABS Wave Induced Bending Moment Distribution Factor ........................................ 21 Figure 15. System Head Curve for Cargo Pumps ......................................................................... 39
Figure 16. System Head Curve for LD Compressors ................................................................... 40 Figure 17. System Head Curve for HD Compressors ................................................................... 40
Figure 18. System Head Curve for Stripping Pump ..................................................................... 41 Figure 19. System Head Curve for Fuel Supply Pump ................................................................. 41 Figure 20. Bunker Operation Sensitivity ...................................................................................... 44
Figure 21. Loading Operation Sensitivity ..................................................................................... 45 Figure 22. Fuel Supply Sensitivity................................................................................................ 45
Figure 23. Spray Down Sensitivity ............................................................................................... 46
Figure 24. Location of Down flooding Points .............................................................................. 58
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STUDENT CERTIFICATION
This is to certify that the following members were part of the design team and by this statement, I
certify that the work done for this design competition was completed by the student team members.
Student Name Signature
Alexander Bidwell
Oscar Como
Luke Herbermann
Benjamin Hunt
Professor Bradley Golden
Faculty Advisor
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ACKNOWLEDGEMENTS
We would like to thank the following individuals for their invaluable support and guidance on this
project.
- Professor Bradley Golden – Webb Institute
- Ethan Wiseman – NYC EDC
- Tom Sullivan – Northstar Midstream
- Raymond Gagliardi – Excelerate Energy
- Peter Wallace – Sea One Caribbean
- Professor Ben Scott – Webb Institute
- Professor Michael Martin – Webb Institute
- Professor Adrian Onas – Webb Institute
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DESIGN REQUIREMENTS
INTRODUCTION
This section outlines the design requirements specified by the client in full detail. The
requirements were given to the team on February 24th, 2020 and have been revised 3 times. We
will summarize the major changes in the following section. The final design requirements can be
found in Appendix A.
DESIGN REQUIREMENT CHANGES
Increasing Maximum LOA
The maximum LOA for our vessel was extended from 90.0m to 95.0m. We conducted an
analysis of the cargo capacity needed to supply gas for our dual-fuel engine and bunker LNG to
the cruise ships. Our vessel did not have enough capacity to complete both missions at 90.0m, so
we asked for an extension to our maximum LOA. This allowed our vessel to employ duel-fueled
engine, which lead to cost savings and decreased emissions.
Lower Maximum Speed Requirements
The maximum speed requirement was lowered from 18 knots to 16 knots. This reduction
in speed decreased the installed power on our vessel by over half, allowing for a more optimal
powering arrangement. We conducted a route analysis to prove that the new maximum speed still
had a sufficient time margin to handle weather delays with delaying bunkering of the cruise ships.
Specifically, we increased the distance between ports by 50% to simulate a reroute or delay for
weather. This calculation can be found in Appendix B.
Modify Pump Requirements
The individual flowrate requirement for the cargo pumps was lowered from 600 cuM/hr to
500 cuM/hr and the maximum discharge pressure be raised from 4.5 bar to 7 bar. This was driven
by an in-depth design of the cargo transfer system we carried out. These changes allowed us to
optimize the cost of our systems well still meeting the goals of our client. The raise in the maximum
discharge pressure allowed to select the optimal pipe diameter to reduce the overall cost of the
system. The lowering of the individual cargo pump capacity allowed us to select a pump that will
be at maximum efficiency at our design flowrate of 500 cuM/hr. We provide redundancy in our
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system by selecting removable pumps, that can be quickly exchanged should one break, instead of
oversizing the individual pump capacity.
REPORT SUMMARY & TABLE OF PRINCIPAL CHARACTERISTICS
The concept design for the LNG Bunkering Vessel was completed on May 30th, 2020. This
concept design represents one “loop” through the design spiral. Several aspects of the design
should be further refined in order to have a comprehensive design package that is ready for
manufacture.
At the beginning of the design process the team analyzed the design requirements and
potential routes of the vessel. This was followed by a parametric analysis of the world fleet of
LNG bunkering vessels. Using this data, we came up with the principal particulars. The next step
was to create a hull form and a preliminary general arrangement. A weight estimate had also been
started at this stage to contribute to the stability and hydrostatic calculations. After this point in the
design, we made a conceptual midship section to prove our ship’s structural integrity. Then, the
design the team selected propulsion method the propulsion plant and associated machinery. This
was followed by a stability analysis on the final concept design. Finally, a basic cost estimate was
procured on the design and construction of the vessel. A broad idea of the vessel is conveyed in
the following table of principal characteristics. Some the final concept characteristics do not
comply with the initial design requirements. This likely means that somewhere in the design
process the requirement was found to be infeasible. All infeasible requirements were discussed
with the client and changed to better suit the vessel limitations.
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Table 1. Principal Particulars
CONCEPT SELECTION AND INITIAL DEFINITION
The design process for the LNG bunkering vessel began with a route analysis to better
define how the ship would service the cruise ships in Miami and San Juan. The following
paragraphs elaborate on the route analysis.
ROUTE ANALYSIS
We carried out a simple analysis to determine what routes would allow two ships to fulfill
the bunkering schedule specified by the owner. The owner’s bunker requirements are to bunker
1,500 cuM of LNG every seven days to two separate cruise ships. One cruise ship is to be bunkered
in Miami, FL and the other cruise ship is to be bunkered in San Juan, PR. The bunker vessel will
load LNG at a shoreside terminal located in Jacksonville, FL.
We established an accurate estimate of the bunker and loadings operation timelines using
information from our mentor, Tom Sullivan, as well as a mix of research and our group’s
knowledge of Ship-To-Ship (STS) LNG transfer operations. We determined our vessel would
require 7 hours to complete the 1500 cuM bunkering operation utilizing a transfer rate of 1000
cuM/hr. The loading operation at the Jacksonville LNG Terminal is estimated to take 13 hours
utilizing the terminal’s design transfer rate of 2400 gpm. Route analysis calculations include
estimated connection and disconnection time as well as time for liquid-freeing and purging
operations.
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At first glance it was clear that one vessel would not satisfy the mission because the route
was far too long to complete in one week at a service speed of 14 knots. We considered utilizing
a fleet of two vessels, each dedicated to serving a single port. This was determined to be infeasible
because the route from Jacksonville to San Juan was too far long to service every week with one
vessel. Next, we considered using two vessels operating in a loop between Jacksonville, San Juan
and Miami. It was determined that the bunkering schedule could be met if the two vessels operate
on staggered schedules. The calculation tables for this analysis can be found in Appendix B.
Figure 1. Route Analysis Solution
PARAMETRIC ANALYSIS
After the route analysis, the design team started gathering characteristic data of the world
fleet of LNG bunkering vessels. The key characteristics we gathered were:
• Length overall
• Beam
• Draft
• Depth
• Cargo capacity
• Speed
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Prediction Path
The driving factor of the parametric analysis was cargo capacity as it is integral to the
vessel’s mission. The vessel must have a cargo capacity of around 4000cuM to sufficiently supply
the two cruise ships. This estimated cargo capacity was the used as a starting point for our
parametric analysis
We found tank capacities for every LNG bunkering vessel we researched, providing a good
basis for our parametric analysis. With this data, we interpolated at 4000cuM to find the length
overall of our ship. Using this length, we interpolated for other parameters such as beam, depth,
design draft, main engine MCR, and gross tonnage.
We increased the overall size of the vessel based on advice from our advisors and our
technical knowledge. This eases the process of making a general arrangement and prevents having
to increase the size of a ship later in the design process. Increasing the size later in the design
process can cause the vessel to have to comply with new regulations for its larger size. Having to
adjust a pre-existing design to meet new requirements is tougher than to deal with them in the
beginning design stages.
Analytic Approach
We conducted a parametric analysis to select a starting point for our LNG bunkering
vessel’s principal particulars. These particulars include the length, beam, depth, and draft of the
vessel. Essentially, the parametric analysis creates a visual representation of the numerical
similarities and differences between currently operational vessels that share similar mission
statements.
For our case, we gathered values for various parameters from several LNG vessels with
relatively similar cargo capacities. Due to the infant nature of the LNG bunkering industry, there
is a lack of available public information on these vessels. Much of the detailed information on
current LNG bunkering vessels remains non-public due to proprietary nature of the designs. With
a database populated with sufficient values for most of the parameters, we were able to begin
analyzing all our data entries.
For the analysis, we developed a Microsoft Excel model. The model is made up of three
different sheets. The “Combined” sheet is the combined data from all the ships researched by each
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individual group member. The “Interface” sheet contains the input and output of the model, and
the “Calculations” sheet shows the derivations and steps to arrive at the output displayed on the
interface sheet. We developed and used this model to reduce the total amount of work done by
hand in Microsoft Excel.
There are four inputs required to generate a plot. The inputs are drop down boxes describing
which parameter the user would like to predict (Y axis) and the parameter the user would like to
base that prediction off of (X axis). The user can choose a linear, logarithmic, or natural
logarithmic scale for each parameter selected. With these four inputs entered, a plot is generated
on the same sheet to the right of the model table. For the Prediction Calculator portion of the
model, the user inputs a desired value of the independent variable that matches the X parameter in
the same row under the Plot Generator Inputs table. The output column calculates and displays the
predicted dependent variable value using the selected regression equation based on the scaling
factor chosen under the Plot Generator Inputs table. Adjacent to the output value is the calculated
r2 value for the corresponding plot generated. The r2 value, or coefficient of determination, is the
proportion of the data explained by the generated linear regression model, and it gives us a
numerical evaluation of our predicted value. A higher r2 value (values range from 0 to 1) indicates
a better fit. An example is shown below in Table 2. Figure 2 shows the corresponding plot
generated.
Table 2. Excel Model Example
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Figure 2. Generated Plot Example
Contained within the Calculations sheet are the groups of individual entry calculations and
generated plots. These groups are broken up into bordered off sections that are clearly identified
and labeled. An example of one calculation section can be seen below in Figure 3.
The left side of Figure 3 depicts each vessel’s respective parameter values extracted from
the combined data sheet. With these values, we created a scatter plot. We also used the slope,
intercept, and r2 Excel functions to create a linear regression equation. With this information as
well as the desired scaling of each parameter of interest, we were able to predict a Y value for a
given X value. The top right portion of Figure 3 shows the adjustment calculation for scaling when
using a logarithmic or natural logarithmic scale. The example shown uses linear scaling on both
axes, so there is no adjustment made.
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Figure 3. Calculations Sheet Example
The only nuances we noticed with this model were the problems that came from the
incompleteness of the data sheet. For each pair of entries per vessel, if there is a vessel with one
or no values, the user must manually clear the entries within the calculations sheet in order for the
data to be plotted correctly. Additionally, for each plot created over an existing user entry in the
model table, the user needs to manually drag and autofill the top row of the extracted values from
the data sheet. This populates the formally deleted rows with their newly extracted values taken
from the combined data sheet.
Analysis Result
Tabulated below in Table 3 are the results of our parametric analysis. We purposely
increased all of the predicted values in choosing the vessel’s principle particulars. We did this
because it is significantly easier to decrease these values versus increasing them further along in
the design process. Information regarding the order and methodology in which these values were
decided on has already been covered under the section titled, “Prediction Path”.
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Table 3. Initial Parametric Analysis Results
After these estimates were made, the actual designing of the ship caused some of these
parameters to diverge from the initial parametric analysis. For example, in the next section about
the hull form development, the initial hydrostatics report proved that our design draft would be
rather difficult to meet. In actuality, the design draft would fall around 3.75 m instead of 5.1 m.
We also increased our cargo capacity and length overall all to accommodate duel fuel engines.
HULL FORM DEVELOPMENT
We used the Orca 3D Hull Assistant to create a hull form for our LNG bunkering vessel.
We picked the “ship assistant” design from the library of hull designs. Using the results from our
parametric analysis, we created a hull form with our particulars of 90 m LOA, 20 m beam, and 10
m depth. The hull form was heavily inspired by the existing designs such as GTT’s 90m bunker
vessel concept design. In our final design, there is an extra 2.9 meters added to the LOA because
of our forecastle deck. In one of the following sections we discuss making the general arrangement.
While we were making the general arrangement, the cargo tanks were designed to comply with
the International Gas Carrier code (IGC code). Since this turned out to be a challenge, the design
team spoke with the client and discussed increasing the length overall. This did not impact our hull
form; however, it allowed us to add a forecastle deck without worrying about our ship having
trouble complying with the IGC code while meeting our needed cargo capacity.
SECTIONAL AREA CURVE
Orca 3D hydrostatic report to generate the section areas for the sectional area curve at the
design draft of 3.75 m. The data was then plotted in Excel to produce sectional area curve shown
below in Figure 4.
Parameter Model Results Finalized Parameter
Length (m) 93.9 90
Cargo Tank Capacity (m^3) N/A 4000
Beam (m) 17.1 20
Design Draft (m) 5.1 5.5
Depth (m) 7.8 10
Main Engine MCR (kW) 2376.1 3500
ITC Gross Tonnage 4958.7 5000
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Figure 4. Sectional Area Curve
LINES PLAN
The lines plan was created using an export of intersecting planes with the hull form in
Rhino. Because the propeller shaft gondolas were instituted rather late in the design, they do not
appear on the lines plan. The buttock lines and waterlines are taken every two meters along the
respective direction and the stations are spaced every 9.0 m. For the lines plan drawing, see
Appendix C.
CURVES OF FORM
The curves of form for a vessel represent its hydrostatics at the indicated loading conditions
and draft lines. These curves of forms can be found in Appendix D.
SPEED AND POWER ESTIMATE
The bare hull resistance and propulsion powering requirement was determined by
performing a Holtrop analysis in Orca3D. Propulsive efficiencies for the B-series of propellers
were utilized in the analysis to determine the required propulsion plant power. At 16kts, the total
bare hull resistance was determined to be 497 kN and the required power was determined to be
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8000 kW. For the design transit speed of 14kts, the bare hull resistance is 277 kN and the required
propulsive power is 3900 kW. The results of the Holtrop analysis are shown below in Figure 5.
Figure 5. Orca3D Holtrop Analysis Results
GENERAL ARRANGEMENT
The general arrangement for our vessel is laid out in Appendix E. This arrangement
contains the outboard profile, inboard profile, weather deck plan view, main deck plan view,
machinery arrangements, accommodation space arrangements, and a midship section view. The
layout of the spaces and arrangement of the machinery allows the vessel to efficiently fulfill the
Owner’s Requirements while complying with applicable regulatory codes.
Cargo Containment
Two spherical ended Type C independent tanks are utilized for cargo containment. This
containment system offers several distinct advantages over membrane containment systems. Type
C tanks have a higher durability and are less expensive than their counterparts. These tanks can
withstand pressure stemming from excess boil-off gas, providing an added level of resiliency in
the realm of cargo management. The placement of the cargo tanks is fundamental aspect of the
design and influences the arrangement of the cargo transfer and cargo management systems. The
arrangement of the tanks relative to the hull structure was ultimately dictated by IGC code 2.5.1,
which defines the minimum distance between the cargo containment system and the hull. This
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placement heavily influenced the arrangement of the cargo systems and deck machinery as well as
the physical layout of the piping on deck.
Weather Deck
The vessel features two cargo manifolds, port and starboard, located at midships. The
decision to place the manifolds at midships was influenced by the manifold orientation on similar
LNG bunkering vessels. The height and transverse position of the manifolds was set to allow for
compatibility with the transfer arms of the shoreside terminal. Each manifold consists of a single
liquid line and two vapor lines, as specified in the Owner’s Requirements. Each manifold features
a deluge system to comply with both the Owner’s Requirements and regulatory standards. During
cargo operations, this system blankets the surrounding ship structure with a protective layer of
water. This system maintains the integrity of the surrounding structure in the case of a loss of
containment.
Two knuckle boom hose handling cranes are located forward of each cargo manifold.
These cranes allow for efficient deployment of hoses and transfer equipment during ship-to-ship
(STS) operations. We identified two potential LNG STS transfer systems suitable for use onboard
this vessel. The KHOBRA system, produced by Houlder LNG Technology and Solutions,
integrates the liquid hose, vapor hose, and the emergency release coupling (ERC) into a single,
compact package. The streamlined nature of this design would simplify bunkering operations and
decrease bunkering time. Another potential candidate is transfer system offered by KLAW LNG.
This saddle and hose system is proven and has been utilized in countless LNG STS operations
around the globe. Depictions of the two systems are shown in Figure 6 and Figure 7 respectively.
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Figure 6 KHOBRA Transfer System
Source: houlderlng.com
Figure 7. KLAW LNG Transfer System
Source: klawlng.com
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The compressor room is located on the aft portion of the weather deck due to the integral
role of the compressors in cargo management and cargo transfer operations. This location
simplifies the piping arrangement and is compliant with the standards outlined in the IGC code,
which states that cargo transfer lines must not pass though or underneath accommodation spaces.
Mooring
The vessel features two forward double wildcat anchor windlasses and two aft winches
for mooring operations. Four davit-mounted pneumatic fenders are located on the weather deck
for mooring use during bunkering operations. These fenders are sized to allow for sufficient
stand-off distance between the bunkering vessel and the cruise ship. The davits allow for quick
deployment of the fenders, reducing the required time for mooring. Figure 8 depicts a typical
davit-mounted fender arrangement.
Figure 8. Fender Davit
Source: ttsgroup.com
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Accommodations
The superstructure arrangement is laid out as most accommodation spaces are laid out.
The one major difference is that on 01 Deck there is the cargo control room and deck conference
room. This is to allow direct access to the top Weather Deck, where most of the cargo operations
would take place. Just below 01 Deck is Main Deck. Main Deck has some engine room
machinery arranged on it to help give ample room to all the important machinery. As of now our
vessel has staterooms for 18 crew members.
AREA VOLUME REPORT
The footprint and volume of each machinery and accommodation space was calculated to
verify the sizing of spaces. Shipboard experience was utilized to correctly size the spaces. See
Appendix F for tabularized area and volume data for each space.
CAPACITY PLAN
A capacity plan outlining the location and capacity of the various cargo and auxiliary tanks
onboard the vessel. The capacity plan is contained in Appendix G.
STRUCTURAL DESIGN
CONCEPTUAL MIDSHIP SECTION AND SECTION MODULUS
The design of the midship section for the vessel is based on the midship section design of
a 165K Membrane type LNG Carrier. This design served as a basis for an arrangement of the
structural elements. This design also aided in the selection of stiffeners for the design. A
longitudinal framing arrangement was used due to the operational profile of the vessel. The major
loads considered for the longitudinal strength of the vessel were buoyancy, wave induced loads
and weight at the full load condition. The structural arrangement produced for the vessel meets the
minimum section modulus requirement as well as the various plate thickness requirements
specified by ABS. Our structural midship section can be found in Appendix H.
RULES AND REGULATIONS
We based our structural design on the ABS Under 90 Steel Vessel Rules. We decided this
set of rules was the most applicable set of ABS structural rules for our design. The design
requirement is that we comply with ABS Marine Vessel Rules; however, the ABS Under 90 Steel
Vessel Rules are more conservative so we chose to follow those.
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There are several rules relating to structural configuration in the ABS U90 SVR (U90 is
the short for under 90 m) that need to be met for our vessel to be classed. Even though our LOA
is 92.9 m, our scantling length is defined as 84.1 m which means our vessel’s applicable rules are
from the guide for vessels under 90 m. For our minimum section modulus requirement, ABS states
in ABS U90 SVR 3-2-1/3 that the hull girder section modulus is to be the maximum section
modulus either of equation 3-2-1/3.1. or equation 3-2-1/3.3.4 Equation 3-2-1/3.3.4 is given as: SM
= Mt / fp cm2-m. Mt is the total bending moment which is equivalent to the maximum algebraic
sum of the still water bending moment and the wave induced bending moment. The written
sections below explain in more depth the still water bending moment and wave induced bending
moment calculations. fp is the nominal permissible bending stress given by ABS as 1.784 tf/cm2.
Equation 3-2-1/3.1 is given as: SM = C1C2L2B(Cb + 0.7) cm
2-m. In this equation, C1 and C2 are
constants given by ABS, L is the scantling of the vessel, B is the breadth of the vessel, and Cb is
the block coefficient (all variables are specifically defined by ABS).
The ABS U90 SVR rules also outlined specific dimensional requirements for the
components that make up the ship structure. Detailed calculations for the minimum dimensions of
the components are contained in Appendix I. The method for determining the minimum bottom
shell plating thickness is outlined in ABS U90 SVR 3-2-2/3.3. The minimum bottom shell plating
thickness is a function of the frame spacing, depth, scantling draft, and the length between
perpendiculars of the vessel. The side shell plating thickness is described by ABS U90 SVR 3-2-
2/5 and is a function of the frame spacing, depth, draft, and length between perpendiculars for the
vessel. ABS U90 SVR 3-2-2/16 outlines the procedure for calculating the minimum bilge plating
thickness. The thickness of this component is a function of the girth spacing of the bilge
longitudinal, depth, draft, and length between perpendiculars of the vessel. The minimum required
deck plating thickness is outlined by ABS U90 SVR 3-2-3/3.3 and is a function of the longitudinal
frame spacing. The method for calculating the dimensions of the center girder at midships is
outlined in ABS U90 SVR 3-2-4/1.3. The minimum thickness of the girder is a function of the
length between perpendiculars of the vessel. The depth of the girder is a function of the breadth
and draft of the vessel. ABS U90 SVR 3-2-4/1.5 outlines the procedure for calculating the required
thickness of the side girders of the vessel. The thickness of the side girder is a function of the
length between perpendiculars of the vessel. The required inner bottom plating thickness is
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dictated in ABS U90 SVR 3-2-4/1.13 and is a function of the length between perpendiculars of the
vessel and the longitudinal frame spacing.
LONGITUDINAL WEIGHT CURVE
We developed a longitudinal weight curve for our vessel in the full load condition. We
used the weights determined in the initial weights and centers estimate to create the full load
longitudinal weight curve. The weights and centers section later in the report details how we came
up with the values for each weighted section.
We distributed the hull structural weight over the full length of the according. The weight
distribution was scaled by the beam of the vessel at main deck to get an accurate distribution of
structural weight in the bow and stern region. The deckhouse and forecastle structural weight was
evenly distributed overs its longitudinal extents. The poopdeck’s structural weight was distributed
according to the beam at the main deck.
The portion of the outfit weight located at amidships was evenly distributed over the entire
length of the vessel. The portion of the outfit weight located in deckhouse was evenly distributed
over the footprint of the deckhouse. The portion of the outfit weight located in the machinery space
was evenly distributed over the length of the machinery space.
The weight of the propulsion plan and freshwater were evenly distributed over the length
of the machinery space. The weight of the diesel oil and lube oil were evenly distributed over the
footprint of their respective tanks. The weight of the crew and effects, and provision was evenly
distributed over the footprint of the house.
The cargo weight was distributed according to the cross-sectional area of tanks at the given
frame. The weight of water ballast for each set of tanks was distributed evenly over the length of
each set of tanks. The complete longitudinal weight curve is depicted below in Figure 9.
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18 Dr. James A. Lisnyk Student Ship Design Competition
Figure 9: Longitudinal Weight Curve
BUOYANCY CURVE
We used Orca3D’s hydrostatics report to find the immersed area at each frame in the full
load condition of our vessel. Linear buoyancy was found multiplying the immersed area by the
specific weight of seawater. See the following figure for the buoyancy curve.
Figure 10. Buoyancy Curve
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STILL WATER BENDING MOMENT CURVE
After finding the longitudinal weight distribution curve and the buoyancy curve, it is
possible to calculate the still water bending moment curve. To do this we first calculate the shear
force at every station. The shear force is the integral of the net load curve. The net load is the
difference between the weight and buoyancy force (depicted in Figure 11: Longitudinal Net Load
Curve). We carried out this integral with the trapezoidal method. After the shear forces are
calculated, the bending moment is calculated by using the same trapezoidal method to integrate
the shear force curve.
Figure 11: Longitudinal Net Load Curve
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20 Dr. James A. Lisnyk Student Ship Design Competition
Figure 12: Shear Force and Bending Moment Diagram
WAVE INDUCED BENDING MOMENT CURVE
The wave induced bending moment curve is needed to find the minimum required section
modulus. ABS U90 SVR 3-2-1/3.3 outlines the procedure for finding the wave induced bending
moment curve. First, we are given ABS U90 SVR equation 3-2-1/3.3.3(a) which relates the
sagging moment and hogging moment amidships to the ABS defined constants k and C1 as well
as the previously mentioned L (scantling length), B (maximum breadth), and Cb (block coefficient)
as seen below.
Figure 13. ABS Hogging and Sagging Moment calculation
In addition to using these equations, the wave induced bending moment calculation
requires a distribution factor M described in ABS U90 SVR 3-2-1/3.3 Figure 14. ABS Wave
Induced Bending Moment Distribution Factor.
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Figure 14. ABS Wave Induced Bending Moment Distribution Factor
This distribution factor is multiplied by the Mws and Mwh values from above to get the wave
bending moment. The total bending moment Mt is equal to the algebraic sum of the still water
bending moment and the wave induced bending moment.
MINIMUM REQUIRED SECTION MODULUS
Perhaps the most important calculation to designing our structure is determining the
minimum required section modulus. ABS U90 SVR 3-2-1/3.3.4 states that the required section
modulus is to be obtained by dividing the total bending moment (Mt) by the nominal permissible
bending stress fp. The total bending moment is calculated in the above section on wave induced
bending moment and the nominal permissible bending stress is defined by ABS as 1.784 tf/cm2.
VERIFICATION OF COMPLIANCE WITH ABS RULES
We verified our design complied with ABS rules by calculating the moment of inertia and
section modulus of our design structural midships section. The limiting section modulus for our
design was the section modulus to the top of the trunk deck stiffeners as the trunk deck stiffeners
are the farthest structural element from the neutral axis. The results of this calculation are
summarized below in Table 4 and can be found in Appendix H. The required section modulus is
the limiting variable for our design. This is because of the large distance between the neutral axis
and the top of the trunk deck stiffeners. Our design produces greater values for its section modulus
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and moment of inertia than the minimum required values. We decided to not reduce the section
modulus of the design further due to the use of small stiffeners in the design. We did not reduce
the number of stiffeners because it would have increased the minimum plate thickness and may
have caused problems with local loads later in the design process.
Table 4. Designed and Required Section Modulus and Moment of Inertia
PROPULSION PLANT TRADE-OFF STUDY
DEFINITION OF CRITERIA
The following section outlines the selection of the propulsion plant for the vessel. The
selection of the appropriate powering and propulsion system was heavily influenced by several
factors specified in the owner’s requirements, as well as other criteria critical to the integration of
the plant into the design. The following factors were considered:
• EPA Tier IV and IMO Tier III Compliance
• Use of Electrical Component for Power generating and Propulsion systems
• High Degree of Maneuverability
• Powering Flexibility
• Spatial Efficiency
• Reliability/Redundancy
• Maintenance Cost
• Capital Cost
The primary criteria driving the propulsion plant selection were specified by the owner in
the Machinery, Propulsion, and Steering Systems Requirements. It was specifically requested that
the designers utilize green technologies to the greatest extent possible and integrate a major electric
component in the design of the propulsion system. The owner’s requirements further expand on
the environmentally conscientious, stating that the vessel must comply with EPA Tier 4 Emission
Standards. Compliance with this regulation is not only critical to the specifications requested by
Total Moment of Inertia (cm^2*m^2) 2.29E+05
SM Trunk Deck (cm^2*m) 2.28E+04
Required Total Moment of Inertia
(cm^2*m^2) 4.00E+04
Required SM Trunk Deck (cm^2*m) 1.58E+04
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23 Dr. James A. Lisnyk Student Ship Design Competition
the owner, but it is integral to the operational region of the vessel. Additionally, the owner specified
that the propulsion system must provide the vessel with a high degree of maneuverability. It is
essential for the vessel to have the ability to come alongside the cruise vessels in a safe and efficient
manner. This will help minimize the need for supporting tugs and reduce the possibility of delays
to the demanding schedule of cruise vessels.
Powering flexibility, spatial efficiency, reliability, redundancy, maintenance cost, and
capital cost were additional criteria considered in the propulsion plant trade-off study. Powering
flexibility is defined as the ability of the power plant to match the powering requirements of various
loading conditions. Most propulsion plants are designed to perform optimally within a specific
loading range. Extended periods of operation outside this region can cause excessive wear on the
engine, increasing maintenance costs and decreasing the useful life of the asset. It is essential for
the selected power plant to provide the powering flexibility to meet the various loads seen across
transit, maneuvering, bunkering, and terminal loading operations. As outlined in the owner’s
requirements, the vessel must have a design transit speed of 14kts and top speed of 16kts. As seen
in the powering estimate section, there is a significant difference in the required propulsive power
for the 14kt transit and 16kt transit condition. It is critical for the propulsion plant to have the
ability to efficiently meet these two loading scenarios. Additionally, the power plant must have the
ability to match the loads required for maneuvering, bunkering and terminal loading operations.
While the loading for these three cases is much lower than for the described transit conditions, it
is still substantial due to the duration of these operations.
Spatial Efficiency is another critical design factor due to the special restrictions imposed
by the machinery spaces. The selected power plant must fit within the spatial limitations of the
machinery spaces and the propulsors must not extend below the baseline of the vessel.
Additionally, it is essential that the propulsion plant provide a high degree of reliability and
redundancy, allowing the vessel to fulfill its mission in the event of damage to the plant. In addition
to what was already mentioned, the maintenance cost and capital cost were also considered.
APPROACH
The selection of the main power plant and propulsion method utilized a progressive three
tier method to weigh the benefits and drawbacks of the considered systems. Systems were initially
sorted by fuel type due to the dependence of emission regulatory compliance on fuel type.
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Categories consist of diesel, natural gas and duel fuel (diesel and natural gas). Propulsion plants in
each of these categories were further divided into sub-categories based on drive type consisting of
mechanical drive and diesel-electric drive. Systems were further categorized by propulsor type
into one of three groups: twin screw, z drive, and azi-pod.
TRADE-OFF STUDY
Fuel Selection
The fuel selection process began by listing out the potential benefits and drawbacks of
each proposed fuel. The results were then outlined in a “pros and cons list” alongside one another
as seen in Table 5.
Table 5. Fuel Type Pros and Cons
A dual fuel system was determined to be the optimal system for the bunkering vessel.
While dual fuel engines have a higher associated acquisition cost and require a specialized fuel
gas system, the system complies with the EPA Tier 4 emission standards. Dual fuel systems also
Pros Cons
-Fuel flexibility adds redundancy
-Proven and reliable system
Diesel
Natural Gas
-Eliminates use of propulsion
plant for BOG management
-Diesel fuel is more expensive
than LNG
-More complex than a
conventional diesel plant
-Meets EPA Tier 4 and IMO
Tier 3 Emissions Standards
-Larger cargo tanks required
for sufficient endurance
-More complex than a
conventional diesel plant
-Fuel readily availible
-Simple and proven -Requires additional
equipment for environmental
compliance
-System is expensive
-Fuel can only be bunkered at
the JAX LNG Terminal
-Additional method of BOG
management
-Meets EPA Tier 4 and IMO
Tier 3 Emissions Standards
Dual Fuel
-LNG is less expensive than
diesel fuel
-System is expensive
-LNG is less expensive than
diesel fuel
-Additional method of BOG
management
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25 Dr. James A. Lisnyk Student Ship Design Competition
offer significant savings in operating expense, as natural gas is less expensive than ultra-low sulfur
diesel. Additionally, dual fuel provides additional endurance flexibility compared to a pure natural
gas system. If voyage is significantly prolonged and there is not sufficient LNG fuel onboard, the
vessel can operate the propulsion plant off a reserve diesel tank. In the event that the fuel gas
system fails, the diesel mode serves as a backup fuel supply system, adding a layer of resilience to
the vessel. Dual fuel systems also provide an additional method for managing boil-off gas.
Drive Type
The drive type for the vessel was determined using the same method utilized for the fuel
selection. The two drive systems considered for use were a diesel electric system and a
conventional mechanical drive system. A diesel electric system consists of a series of generators
which power electric propulsion motors. A traditional mechanical drive system consists of one or
more engines connected directly to the propulsors via a mechanical linkage. A power take-off
system is typically included in a mechanical drive system, allowing the vessel to utilize excess
power from the main engines to satisfy various electrical loads. The benefits and drawbacks of
each of these systems are outlined below in Table 6.
Table 6. Drive Type Pros and Cons
A diesel electric system was selected due to numerous advantages it presents in this
unique application. Unlike a mechanical drive system, the diesel electric system contains a
Pros Cons
-Only compatible with
mechanical propulsors
-Performs optimally at a
narrow range of powers
-Requires power-take off
system or generators for
additional electrical loads
-Meets significant electrical
component specified in Owner's
Requirements
-Simple and proven
-Inexpensive
-System is more expensive
than a conventional diesel
Multiple generators provide
additional redundancy
-Flexibility to match electrical
loads
-Requires additional electrical
components
-Larger spatial requirement
-More complex than a
conventional diesel plant
-Range of compatible propulsor
types
Diesel
Electric
System
Conventional
Mechanical
Drive
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significant electrical component that complies with the owner’s request that propulsion system
contain a significant electrical component. Diesel electric systems also provide greater powering
flexibility in comparison to mechanical drive systems. There are significant differences in
powering requirements for the top speed condition, design transit condition, maneuvering, and
various cargo operation conditions. The diesel electric system allows generators to provide the
required power by operating the generators in various configurations, where each generator is run
at an optimal loading condition. This can help reduce wear and prolong the useful life of the
generators. This is a clear advantage compared to the mechanical drive system, which would spend
most of its life operating well below its designed operating region. Another benefit of the diesel
electric system is the redundancy offered by multiple generators. The generators can be selected
in manner that allows the vessel to meet its design transit speed with any single generator offline.
It is important to note that there are a few potential drawbacks of the diesel electric system such as
higher cost, increased complexity, and potential issues regarding spatial efficiency. While these
factors are clearly outweighed by the benefits of the system, it is important to recognize these
drawbacks.
Propulsor Type
The three propulsor types considered for use were z-drive thrusters, azimuth thrusters,
and twin screw propulsors. The benefits and drawbacks of each were outlined as shown in Table
7. Each system was compared against the other candidates to determine the optimal choice for the
vessel.
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Table 7. Propulsor Type Pros and Cons
The twin screw propulsion system best fit the needs of the vessel and presented several
distinct advantages compared to the other systems. While the z-drive and azimuth thrusters provide
better maneuverability than twin screw propulsors, these two systems have significant spatial
limitations imposed by the draft of this specific vessel. After researching the requirements for these
thruster configurations, it was determined that there is no available podded propulsion system on
the market that provides the required thrust without protruding below the baseline of the vessel.
Significant modification would need to be made to the hull form to use either of these propulsion
systems. With the addition of a bow thruster, the performance characteristics of the twin screw
electric propulsion system are sufficient to meet the high degree of maneuverability specified in
the owner’s requirements. Techniques, such as prop splitting, can be used in conjunction with the
bow thruster to precisely position the vessel alongside cruise vessels. A key advantage of twin
Pros Cons
-Requires sufficient space for
mounting along the underside
of the vessel
-Fairly high degree of
maneuverability when used with
a bow thruster
-Requires bow thruster
-Lower degree of
manueverability compared to
other systems
-Expensive
-Complex
-Requires sufficient space for
mounting along the underside
of the vessel
-Very high degree of
maneuverability
-Fewer mechanical linkages
make the system robust
-Complex
-Expensive
Twin Screw
-Greater mounting flexibility
compared to other propulsor
types
-Inexpensive
-Simple and robust
-Mechanical linkages create
additional points of failure
Azimuth
Thrusters
-Very high degree of
maneuverability
Z-Drive
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screw propulsors is the simplicity of the design which reduces failure points and adds a degree of
resilience to the propulsion system.
POWER PLANT SELECTION
The dual fuel diesel electric twin screw propulsion system was further defined by
selecting specific generators and propulsors. To aid in the selection of the optimum generator
configuration, the propulsive power requirements from the Holtrop analysis were used to estimate
the range of loading conditions seen by the system.
Dual fuel generator sets produced by MAN B&W and Wärtsilä were identified as the
best potential candidates for use in the vessel due to the wide use of dual fuel products from these
two manufacturers across the marine industry. After researching various models from each
manufacturer, it was determined that generator sets from Wärtsilä would be better suited for this
design due to the abundance of technical data on Wärtsilä’s product line. While MAN B&W’s
high-pressure dual fuel system has potential advantages, such as reduced methane slip, it was
difficult to find the necessary technical data to perform a proper analysis on these generator sets.
It is critical to have data, such as specific fuel consumption, to properly select an optimal generator
for this application.
The optimal generator configuration for the vessel consists of two Wärtsilä 8L34DF
gensets and two Wärtsilä 6L20DF gensets. This configuration offers optimal performance across
a range of expected loading conditions. Table 7 displays the rated power provided by this
configuration.
Table 8. Wärtsilä Generator Configuration
MACHINERY ARRANGEMENT
The machinery space on our vessel has three levels. The engine control room is located on
the main deck level. The machine shop is located on this level to give the engineers easy access to
it from the engine control room. Most of the quiet equipment is located on this level to minimize
the noise that enters the accommodations block from the machinery space. The gas combustion
Genset Rated Power (kW) Number Sub Total Wartsila 8L34DF: Specific Fuel Consumption Data
8L34DF 3490 2 6980
6L20DF 1065 2 2130
Total 9110
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unit is located on this level and is separated from the rest of the machinery space by a double
walled bulkhead, as required by the IGC Code.
The 1st platform houses our vessels generators. This deck has plenty of head room to allow
the diesel engines to be maintained. The compressors skid is also located on 1st platform. The
steering gear is located on this level and is separated from the main machinery space by a
watertight bulkhead.
The electric propulsion motors are located on 2nd platform. The fuel and oil tanks are also
located in this level to help lower the VCG of our vessel. The pumps skid is located on this level
to increase the net positive suction head available (NPSHa) for the various pumps. The machinery
arrangement for our vessel can be found in Appendix J.
H, M, AND E SYSTEMS AND EQUIPMENT
We based our machinery list of our sea term experience aboard commercial vessels and
general knowledge of the function of shipboard systems. Lists of machinery to be included in each
system are listed below.
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30 Dr. James A. Lisnyk Student Ship Design Competition
Equipment Quantity Equipment Quantity
Purifier 2 Air Receiver 1
Feed Pump 2 High Pressure Compressor 2
Piping TBD Emergency Air Receiver 1
Valves TBD Emergency Air Compressor 1
Piping TBD
Valves TBD
Equipment Quantity Equipment Quantity
MGO Transfer Pump 1 Emergency Diesel Generator 1
MGO Storage Tank 2 Diesel Tank 1
MGO Overflow Tank 1 Bus Tie Connector 1
Piping TBD Control Panel 1
Valves TBD Piping TBD
Valves TBD
Equipment Quantity Equipment Quantity
MGO Supply Pump 1 Potable Water tanks 2
MGO Service Tank 1 Potable Water Pump 2
Piping TBD Sterilization Unit 1
Valves TBD Calorifier 1
Piping TBD
Valves TBD
Equipment Quantity Equipment Quantity
Tanks 2 MSD 1
Black Water Pump 1 Tanks 2
Piping TBD Black Water Pump 1
Valves TBD Piping TBD
Valves TBD
Fuel Oil Purifying Start Air
Emergency Diesel GeneratorFuel Oil Transfer
Grey Water
Fuel Oil Supply
Black Water
Potable Water
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31 Dr. James A. Lisnyk Student Ship Design Competition
Equipment Quantity Equipment Quantity
Purifier 2 Air Receiver 1
Feed Pump 2 Compressor 1
Lube Oil Heaters 2 Air Drier 1
Piping TBD Piping TBD
Valves TBD Valves TBD
Equipment Quantity Equipment Quantity
Lube Transfer Pump 1 Inert Gas Generator 1
Lube Oil Storage Tank 1 Piping TBD
Piping TBD Valves TBD
Valves TBD
Equipment Quantity Equipment Quantity
Bilge Tanks TBD Main Fire Pump 1
Bilge Pumps 2 Pipes TBD
Oily water seperator 1 Valves TBD
Piping TBD Emergency Fire Pump 1
Valves TBD Pipes TBD
Valves TBD
Equipment Quantity Equipment Quantity
Hydraulic Oil Tank 1 Composite Boiler 1
Hydraulic Oil Pump 1 Condenser 1
Hydraulic Power Unit 1 Feed Pump 1
Piping TBD Piping TBD
Valves TBD Valves TBD
Service/Control Air
Inert Gas Generator
Lube Oil Purifying
Lube Oil Transfer
Hydraulic System
Fire System
Service Steam System
Bilge System
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32 Dr. James A. Lisnyk Student Ship Design Competition
Equipment Quantity Equipment Quantity
HEX with LT Cooling 1 Sea Chest 2
Circulating Pump 2 Circulating Pump 2
Expansion Tank 1 HEX with LT Cooling 1
HT Cooling Pumps 1 MGPS 1
Piping TBD Pipes TBD
Valves TBD Valves TBD
Equipment Quantity Equipment Quantity
Circulating Pump 1 Incinerator 1
Expansion Tank 1 Sludge Pump 1
Pipes TBD Pipes TBD
Valves TBD Valves TBD
Equipment Quantity Equipment Quantity
Compressor 1 Freshwater pump 1
Ventilation ducts TBD Evaporator 1
Air Handler Unit 1 Freshwater Tank 1
Pipes TBD Piping TBD
Valves TBD Valves TBD
Equipment Quantity Equipment Quantity
Compressor 1 Ballast Water Pumps 2
Evaporator 3 Ballast Treatment System 1
Piping TBD Ballast Tanks 15
Valves TBD Piping TBD
Valves TBD
High Temperature Cooling
Low Temperature Cooling
Sea Water Cooling
Incinerator
FreshwaterHVAC
Refrigeration System Ballast System
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33 Dr. James A. Lisnyk Student Ship Design Competition
CARGO TRANSFER SYSTEM
OVERVIEW
The cargo containment and cargo transfer system are designed to allow the vessel to
seamlessly meet the specified flow rates and rigorous transfer schedule required for bunkering and
terminal loading operations. The vessel utilizes two Type C independent tanks for cargo
containment. Two 5-ton hose cranes are included to allow for the transfer of cargo hoses during
bunkering operations. The system is required to bunker cargo to the cruise ships at a transfer rate
of 1000 cuM/hr and receive cargo from the terminal at a transfer rate of 2400gpm. To achieve this,
the cargo transfer system utilizes two main cargo pumps, each with a capacity of 500cuM/hr.
Additionally, two 16 cuM/hr stripping pumps are utilized for cooling the system down prior to
transfer operations and two 2.6cuM/hr fuel supply pumps are used to supply LNG to the fuel
system. Two high duty compressors, two low duty compressors, and a forcing vaporizer are
included to manage vapor during bunkering, loading and fuel supply operations. In addition to the
use of dual fuel engines to manage boil off gas (BOG), a gas combustion unit is included BOG
management redundancy. Table 9 summarizes the mission specific equipment onboard the vessel.
Table 9. Mission Specific Equipment
DISCUSSION OF OPTIONS CONSIDERED
System Boundaries
Our LNG cargo transfer system starts at the suction the two cargo pumps and ends at the
two manifold connections on main deck or before the dual fuel engines located in the engine room.
An additional boundary was placed at each manifold because the shore side terminal is responsible
for the design of the terminal transfer arms. The system boundry for the fuel supply to the dual
fuel engines is located before the fuel gas heater. We did this because we considered beyond the
gas fuel heater to be the responsibility of the designer in charge of the fuel gas system.
Cargo Equipment
2x 5 Ton Hose Crane
2x 500 cuM/hr Cargo Pumps
2x 16 cuM/hr Stripping Pumps
2x 2.6 cuM/hr Fuel Pumps
2x 2930 cuM/hr HD Compressor
2x LD 1765 cuM/hr LD Compressor
1x Gas Combustion Unit
2x Type-C Independent Tank
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34 Dr. James A. Lisnyk Student Ship Design Competition
Design Considerations
Several considerations were made in the decision-making process of arranging our
preliminary schematic. The selection of dual fuel engines heavily influenced the design of the
cargo transfer system. The driving factor of this decision came from our Ship Design I design
statement. It stated, “As a minimum, EPA tier 4 emissions requirements or equivalent are to be
met”. Using dual fuel engines meets these emissions requirements. Using a dual fuel engine in
tandem with a diesel-electric power plant would also allow for us to have a very flexible engine
room arrangement. The choice of dual fuel engines required the addition of a boil-off gas (BOG)
management system. This was another requirement in our design statement which stated under
mission systems/special requirements, “A handling system for boil-off gas (BOG), by means of
liquefaction, thermal oxidation, or fuel sharing, is to be fitted”. We also decided to include a gas
combustion unit (GCU) to provide additional redundancy in BOG management. This unit can be
operated in parallel with the duel fuel system to provide additional vapor management or act as a
standalone management solution. By choosing the fuel sharing option for our dual fuel engines
and utilizing a gas combustion unit, we ruled out the need for a reliquification plant onboard. Since
our bunkering vessel is transporting relatively low amounts of LNG on a short term, repetitive
schedule, we further cemented our decision of excluding a reliquification plant from the design.
We relied heavily on several publications produced by Society of International Gas Tanker
and Terminal Operators (SIGTTO) during the design of our additional schematic. These
publications include Liquified Gas Handling Principals 3rd Edition, The Selection and Testing of
Valves for LNG Applications, and LNG Marine Loading Arms and Manifold Draining, Purging
and Disconnection Procedure. We received additional advice on operational procedures from our
advisors as well as other industry professionals. The piping arrangement for our system was
determined by identifying each operational scenario and determining the resulting load placed on
the respective components. We determined our initial piping arrangement by tracing out the
required flow paths for each case. Valves were then added to the model according to operational
conditions and the reliability required at the point in question. Globe valves are reliable even under
cryogenic conditions and are optimal for isolating individual components locally. Butterfly valves
were placed at junctions between main cargo lines and smaller system branches. Butterfly valves
were chosen for this application due to their weight, simplicity, and their compatibility with larger
pipe sizes. Additionally, Emergency Shut Down (ESD) valves were places at each manifold and
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35 Dr. James A. Lisnyk Student Ship Design Competition
at the liquid and vapor headers of each tank. The placement of these valves at these specific
locations is required by the IGC Code and allows the cargo system to automatically shut down in
the event of an emergency. Throughout the design process, we continuously adjusted the initial
schematic to reflect design choices.
DESCRIPTION OF GOVERNING OPERATING CASES
For our cargo transfer system, we looked at the governing cases that the various
compressors and pumps would be used in during the operation of our system. We determined the
governing operating cases to be loading LNG cargo, bunkering LNG cargo, providing fuel gas to
the engines, and spraying down the tanks.
Loading LNG Cargo
Our mentor, Tom Sullivan, provided us with the maximum cargo transfer rate from the
Jacksonville, FL based terminal our bunker vessel will load from. The maximum cargo transfer
rate is 2400gpm (545cuM/hr). Loading LNG cargo occurs once every 14 days and takes
approximately 13 hours to complete. For this operating case, the LNG enters the system through
the manifold, travels through the main cargo lines, ends up at the cargo header, and finally is
discharged into the cargo tanks. As LNG enters the tank, the boil-off gas (BOG) generation rate
increases resulting in additional vapor generation. While some of this vapor is displaced naturally,
high-duty compressors are needed to move the fluid through the vapor lines up to the vapor
manifold and back to the terminal. A portion of this BOG is diverted to the low-duty compressor
to be sent to the engine room for use as fuel. The BOG generation rate is critical to determining
the proper vapor flow rates. We estimated the generation rate of boil-off gas using the BOG
generation rate of a similar cargo operation described in “Dynamic Optimization of Boil-Off Gas
Generation for Different Time Limits in Liquid Natural Gas Bunkering” by Yude Shao,
Yoonhyeok Lee, and Hokeun Kang. We estimated the maximum BOG generation rate by
interpolating off data from the model contained in the paper. We then doubled this interpolated
value to account for the high degree of variability in BOG generation during STS operations and
our higher cargo transfer rate.
Bunkering LNG Cargo
The flowrate for bunker operation is required to be 1,000 cuM/hr per our vessel’s design
requirements. Bunkering LNG cargo occurs twice every 14 days and takes approximately 7 hours
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36 Dr. James A. Lisnyk Student Ship Design Competition
to complete. For this operating case, the LNG is pumped out of both cargo tanks simultaneously,
directed through the main cargo lines, and flows out of the manifold to the receiving cruise ship
tank. This makes the maximum flow 500cuM/hr using the two main cargo pumps for each tank.
To determine the vapor flow rates for this application, it was assumed that the BOG generation
rate was the same as the rate during cargo loading.
Supplying Fuel Gas to the Engine Room
Our bunker vessel will be using LNG as its main fuel source for its two sets of dual fuel
diesel electric gensets. In general, this operating case is occurring continuously, but vapor is
consumed at a faster rate while the vessel is underway. To obtain an accurate fuel consumption
estimate, we first estimated various power requirements for transit, maneuvering, bunkering and
loading operations referencing: “A Case Study on Boil-Off-Gas Minimization for LNG Bunkering
Vessel Using Energy Storage System” authored by (Kyunghwa Kim, 2019). Following the same
fuel consumption calculation methodology outlined in the paper, we estimated fuel consumption
rates for various dual fuel generators using data obtained from Wärtsilä. We utilized both a generic
LNG heating value as well as a calculated heating value for the composition for the LNG from the
Jacksonville terminal. To determine the highest possible flow rate for the fuel gas supply system,
we specifically modeled the system during operation at maximum service speed. The maximum
fuel flow rate is 1,765cuM/hr of vaporized LNG. Although this seems like a high number, it is
important to keep in mind that liquified natural gas is 1/600th the volume of natural gas vapor.
Spraying Down Tanks
The main cargo tanks must be cooled down prior to loading cargo from the shore side
terminal. The cargo system features a spray system which cools the cargo tanks using a
phenomenon known as evaporative cooling. In each tank, stripping pumps pump heel from the
bottom of the tank through stripping lines to a set of nozzles running along the top of the tank. The
LNG droplets evaporate as they exit the nozzles, cooling the tank. Tanks are typically sprayed
down in the hours prior to arriving at the terminal. The maximum flow rate for spraying down the
tanks was determined by researching stripping pump capacities on LNG carriers and LNG
bunkering vessels. We determined the maximum possible flow rate to be 16cuM/hr. The maximum
flowrate for this operation is 16cuM/hr.
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37 Dr. James A. Lisnyk Student Ship Design Competition
SYSTEM LAYOUT ON GENERAL ARRANGEMENT
Our LNG cargo transfer system on the general arrangement of our LNG bunkering vessel
is available in Appendix K. Various components and piping of the system are depicted and labeled
accordingly. The arrangement of our system was created so that it complied with the rules,
regulations, and requirements outlined in the design requirements & considerations document.
SYSTEM FLOW CALCULATION
We built a model of our cargo transfer system in PIPE-FLO Advantage 17 to determine
the hydraulic characteristics of our system. The modelling of natural gas vapor in PipeFlo
presented some difficulty. PipeFlo conducts an incompressible analysis of the system which
produced unrealistic results as the compressibility effects of vapor are significant to the system.
PipeFlo recommends using different fluid zones to account for the change in pressure’s effect on
compressible fluid properties. We used different fluid zones to evaluate fluid properties at the
closest quarter bar of pressure. This allows an incompressible analysis to produce reasonable
values for a compressible fluid system.
We modeled the LNG fuel tank in the cruise ship at the correct relative height to our system
and used an estimated hose length of 25m. This was easier and more accurate than trying to model
the back pressure at the manifold from the cruise ship. We followed Wärtsilä's product guide for
our vessel’s selected generators to estimate the back pressure from the engine room in the vapor
piping to the engine room. The vapor to the engine passes through a gas valve unit (GVU), which
accounts for most of the pressure drop in the system. Wärtsilä estimates a 1.2 bar pressure drop
over a typical GVU. We added 0.1 bar of pressure drop to account for other head losses and a back
pressure from the engine, which added to a total estimated back pressure of 1.3 bar. We modeled
the tank surface pressure as 0.0 bar gauge. We estimated the back pressure at the vapor manifold
to be 0.1 bar gauge to account for the head-loss in the onshore vapor handling system.
The system flow calculations for all the governing cases are attached in Appendix B. A
summary of the design flowrates and heads for the governing cases are summarized in Table 10
below.
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38 Dr. James A. Lisnyk Student Ship Design Competition
Table 10. Summary of Flowrates and Heads of Governing Cases
PUMP SELECTION
Cargo Pumps
We selected the SMR 250 single stage pump made by Shinko-Nishishiba. The SMR 250
is a removable in-tank pump used for the discharge of LNG, LPG, or DME. It is typically used as
an emergency cargo pump on larger LNG carriers. The pump’s ball bearings are lubricated using
the liquid being pumped. The pump is fitted with an inducer to reduce the NPSH required. The
pump is hydrodynamically balanced using a balance sleeve to reduce the loading on thrust bearing.
The induction motor has insulation to allow it to operate at cryogenic temperatures. The pump can
be removed from the tank for maintenance by lifting the pump up its installed column in the cargo
tank.
Stripping Pumps
We selected the Svanehoj EFP 24-3 for our vessel’s stripping pump. The EFP 24-3 has no
tank connections below the liquid level and no electrical components inside the tank. This
minimizes the generator of boil-off gas from the heat of the electrical components. The pump can
be retracted with liquid still in the tank. This allows for maintenance to occur well the ship is in
service. The pump is fitted with an inducer to lower the NPSH required of the pump (only 2m at
the design point).
Fuel Supply Pump
We selected the Artika 120 3S by Vanzetti Engineering for our vessel’s fuel supply pump.
The Artika 120 is designed for low pressure marine engine fuel gas systems, such as the one fitted
on our vessel. The pump is already certified by ABS for this application and follows IGC
guidelines. The pump features an integrated motor connected with cryogenic power cables. The
pump is lubricated continuously with LNG, reducing maintenance costs. The pump is fitted with
a helical inducer to minimize NPSH required. The pump is designed to be installed within the LNG
tank in a sump.
Flow Rate
(cuM/hr) Head (m)
Flow Rate
(cuM/hr) Head (m)
Flow Rate
(cuM/hr) Head (m)
Flow Rate
(cuM/hr)
Adiabatic
Head (m)
Flow Rate
(cuM/hr)
Adiabatic
Head (m)
Bunkering Operations 500 143 0 0 2.6 133.3 0 0 1765 5858
Cargo Loading 0 0 0 0 2.6 133.3 2930 2345 1765 6031
Supplying Main Engine 0 0 0 0 2.6 133.3 0 0 1765 5804
Spraying Down Tanks 0 0 16 49 2.6 133.3 0 0 1765 5804
Cargo Pumps Stripping Pumps HD Compressor LD CompressorFuel Supply Pumps
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39 Dr. James A. Lisnyk Student Ship Design Competition
SYSTEM HEAD CURVES
System head curves were generated for the governing case for each of the pumps or
compressors. The pump curves of the selected pumps have been overlaid on their respective
governing case. These curves were cargo discharge for the main cargo pumps, supplying the main
engine fuel gas for the low duty compressors (LD compressor), cargo loading for the high duty
compressors, supplying the generators with fuel for the fuel supply pump, and spraying down the
tank for the stripping pumps. The system head and pump curves can be found below. The system
curve for the low duty compressor looks different because of the high back pressure from the
engine room. We did not have data on how the pressure drop across the gas value unit varies with
flowrates. It was treated as a constant, leading to the high static head shown on the system head
curve.
Figure 15. System Head Curve for Cargo Pumps
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40 Dr. James A. Lisnyk Student Ship Design Competition
Figure 16. System Head Curve for LD Compressors
Figure 17. System Head Curve for HD Compressors
0
1000
2000
3000
4000
5000
6000
7000
0 500 1000 1500 2000 2500
Ad
iab
atic
Hea
d (
m)
Flowrate (cuM/hr)
System Head Curve for the LD Compressors
System Head Curve Operating Point
0
500
1000
1500
2000
2500
3000
3500
0 500 1000 1500 2000 2500 3000 3500 4000
Ad
iab
atic
Hea
d (
m)
Flowrate (cuM/hr)
System Head Curve for HD Compressors
System Head Curve Operating Point
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41 Dr. James A. Lisnyk Student Ship Design Competition
Figure 18. System Head Curve for Stripping Pump
Figure 19. System Head Curve for Fuel Supply Pump
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42 Dr. James A. Lisnyk Student Ship Design Competition
OPTIMIZATION
The cargo transfer system was optimized using the annualized cost optimization method.
In this analysis, the capital expenditure (CAPEX) of the system was defined as the acquisition and
installation cost of the piping material, the pipe fittings, the pumps, and the compressors. Due to
the nature of available pricing data, a pricing model was developed to determine pipe cost per
meter as a function of inner diameter. The model consisted of a power-regression model fitted to
standard carbon steel pricing data. A cost correction factor was then applied to the regression
coefficient to account for the cost ratio between the price of carbon steel pipe and the stainless-
steel pipe used in the system. The cost of major components, minor components, and bends were
defined as a function of the cost of pipe at a specified equivalent length. CAPEX was calculated
by discounting the capital cost over the expected lifetime of the system of 20 years at an interest
rate of seven percent. A function was derived expressing the optimal inner diameter of pipe as a
function of the annualized cost of piping material, piping components, maximum flow rate, energy
input, cargo fluid properties, and maintenance.
Using data from the PipeFlo model, the system was divided into 14 piping sections based
on state of the operating fluid, maximum flow rate, primary usage, and inner diameter.
Approximate yearly operating timeframes were calculated for each of these groups based on the
operation profile of the system defines these categories. The characteristics are summarized in
Table 11 below.
Table 11. Pipe Characteristics
For each piping section, the optimum inner diameter was calculated using the associated
characteristics. The calculated optimum diameters were utilized in conjunction with educated
discretion to select pipe sizes for each group. Using the selected standard diameters, the annualized
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43 Dr. James A. Lisnyk Student Ship Design Competition
acquisition, construction, and maintenance cost of the system was calculated. The operational cost
of the system was computed using the fuel pricing per unit energy, fuel to energy efficiency,
required power, and yearly operating time for each pump and compressor. The annualized capital
cost and operating cost were then summed to determine the total annualized cost of the system.
The optimization required several iterations to yield the lowest possible lifecycle cost. At
the end of each iteration, the chosen diameters were input into Pipe Flo to determine the required
pump and compressor power. These new power values were used in conjunction with the selected
diameters