Be positive and lead a happy life

 

RULE NO. 1

Be a positive, optimistic and kind person. Whether you are a happy or unhappy person depends largely on yourself. Negative and pessimistic people are generally unhappy people. Be kind to others. Kindness begets kindness. Try to do a good deed every day. You will find that by brightening the lives of others, you will brighten your own life.

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RULE NO. 2

Maintain a healthy and happy family. If your parents are elderly and living by themselves, try to visit them at least once a week and share a weekly meal with them. One of the problems encountered by our older folks is loneliness.

Be on excellent terms with your spouse. Be faithful to your wife, treat her as if they were still courting and give her all your money.... however, if in case where your wife is a spender and not a saver, then you decide or not to give all.

As for how to behave towards one's children, the advice given by Kahlil Gibran: "And though they are with you yet they belong not to you. You may give them your love but not your thoughts. For they have their own thoughts."

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RULE NO. 3

Find a job you enjoy doing. One of the reasons so many Singaporeans are unhappy is probably that they do not like their jobs or complained about their salary and expenses. Since we spend so much of our lives and time at work, maybe it is better to have a worklife balance to find a job which is not a chore to endure but a pleasure to do. In recent years, it has been noticed a trend of many locals and Singaporeans leaving their jobs for other jobs which pay them less and lesser bonuses but give them greater satisfaction. This could be a good thing and demand lesser stress on individual who value their personal life more.

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RULE NO. 4

Treasure your true friends. In your life journey, you will make many friends - at school, at university, in sports or other activities and at work. Try to develop a small circle of very good friends, friends who will stand by you in good times and bad times. In work place, do not involve in office politics. You will not gain any better if you are poor in handling office politics.

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RULE NO. 5

Exercise regularly. Exercise not only makes you healthier, it also makes you feel better. Therefore, make regular exercise a part of your lifestyle. You can't be a happy person if you are not in good health. Work stress may hit you with extra sickness if you are weak and it may be too late if you are not able to cope with stress.  So get out the stress by some workout.  Any form of workout with colleagues may also help, eg. bowling, jogging, etc.

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RULE NO. 6

Enjoy eating but eat healthily and avoid the sin of gluttony. Singapore is a culinary paradise. Food is abundant, diverse and affordable. If you reach your 50s' like me, eat moderate and watch your diet.

You can eat well on any budget. Let us enjoy our food but let us also exercise some discipline when choosing what to eat. I have always tried to follow the ancient Asian wisdom of stopping when I feel 80 per cent full and not over indulged.

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RULE NO. 7

Be a volunteer and support philanthropy. Mrs Barbara Bush, the wife of the 41st President of the United States said there was a period in her life when she suffered from depression. Instead of seeing a psychiatrist or taking medication to overcome her depression, she decided to be a volunteer. She found that by helping others less fortunate than herself, her depression gradually disappeared.

Whether we are rich or poor, we should contribute to a cause or causes close to our hearts. In spite of our favourable tax regime and the presence of many wealthy people in our society, it was very disappointed to see how lowly Singapore ranked in the table of countries for philanthropy. A saying  that no man could be truly happy if he lives only for himself.

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RULE NO. 8

Read books and listen to music. Reading is an excellent habit. Books keep youcompany when you are alone.  Reading is an endless source of happiness. So is music. With the web around these days, you may also start to do your own blog. Some of the personal blogs which you could see nowadays are very well done and you do not need to pay a single cent but the practicing of blogging improves your knowledge and networking with the outside world.  

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RULE NO. 9

Take pleasure in the little things in life. Try regular walks in the Botanic Gardens. Try to find joy in meeting old friends, attending a concert at the Esplanade and visiting a wonderful exhibition at one of our museums.  Outing on weekends with your family members is definitely one of the good workout.

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RULE NO. 10

Don't envy others. Dr Wee Kim Wee, our sixth President once said that one of the reasons which caused people to be unhappy was that they were envious of others. Dr Wee said he never envied his friends who had a better education or earned more money or lived in bigger houses or owned more expensive cars. His rule was to be contented with what he had. This is a good rule. Philosophically, it would be even better if you could feel vicariously happy when you see your friends and former students doing well in life.  Contentment is natural wealth, luxury is artificial poverty.

 

“Be thankful for what you have; you'll end up having more. If you concentrate on what you don't have, you will never, ever have enough”
― Oprah Winfrey

 

“Be content with what you have;  rejoice in the way things are. When you realize there is nothing lacking,  the whole world belongs to you.”
― Lao Tzu

 

“A quiet secluded life in the country, with the possibility of being useful to people to whom it is easy to do good, and who are not accustomed to have it done to them; then work which one hopes may be of some use; then rest, nature, books, music, love for one's neighbor — such is my idea of happiness.”
― Leo Tolstoy

 

“Do not spoil what you have by desiring what you have not.”
― Ann Brashares

 

“You say, 'If I had a little more, I should be very satisfied.' You make a mistake. If you are not content with what you have, you would not be satisfied if it were doubled.”
― Charles H. Spurgeon

Newbuild offshore drilling rig tilts at Singapore Shipyard

Extracts from Straits Times 4th Dec2012

About 90 workers were injured when a jackup rig at Singapore Shipyard tilted to one side on Monday.

Among them, 22 were quite seriously injured and one was in a critical condition. The rest suffered minor injuries.

The accident happened at one of Singapore shipyard worksite at Tanjong Kling Road.

Preliminary findings showed that the three-legged jackup rig tilted to one side after the jack-up mechanism of one of the legs failed to work.

Officers from MOM's Occupational Safety and Health Inspectorate responded immediately and were investigating the accident on-site .

Thousands of workers were said to be working on the rig at the time of the accident, according to Chinese Shin Min Daily. Some workers said they heard loud bangs and some cables snapped.

According to the Chinese paper, some tried to escape by jumping off the rig into the sea. A worker who spoke to the evening daily said he decided to swim to safety because the gangway bridge linking the rig to the shore were crowded with workers.

Preliminary findings showed that the three-legged jackup rig tilted to one side after the jack-up mechanism of one of the legs failed to work.

 

 

A failed braking system might had caused the oil rig to tilt to one side. Providing an update on the incident to the media, the shipyard initial investigations showed the braking system on one of the movable legs of the rig had failed, causing the platform to slide down the leg on that side. Load tests run on the rig just a day before the accident had shown the three legs of the rig could bear a load of some 9000 tonnes each. The yard is now trying to stabilize the rig so that it can investigate the cause of the brake failure.

 

 

How Rig Tilted

Above Courtesy of Straits Times

 
Earlier, Singapore Minister for Manpower praised evacuation efforts at the yard, saying he was encouraged that all the workers on the rig had been evacuated within 20 minutes.

The new JU3000N design is the result of the combined development efforts of Jurong Shipyard, Noble and Friede and Goldman in creating an enlarged hull that will offer more operational benefits, including ergonomic and efficient accommodation layout, increased deck space and placement of equipment that will allow the crew to efficiently and safely carry out maintenance duties. On completion, the new rigs are capable of operating in waters of 400 feet and drilling depths of 30,000 feet.

The rigs are suitable for operations in many challenging environments, including high temperature areas such as the Middle East and in the North Sea.


General information about a typical offshore drilling jackup :-

The conventional jack-up design has three vertical legs, each leg normally being constructed of a triangular or square framework.

Jack-up basic design involves numerous choices and variables. Typically the most important variables may be listed as stated below.

Support Footing -

The legs of a jack-up are connected to structure necessary to transfer the loadings from the leg to the seafloor. This structure normally has the intended purpose to provide vertical support and moment restraint at the base of the legs. The structural arrangement of such footing may take the following listed forms;

-gravity based (steel or concrete),

-piled

-continuous foundation support, e.g. mat foundations

-individual leg footings, e.g. spudcans (with or without skirts).

Legs -

The legs of a jack-up unit are normally vertical, however, slant leg designs also exist. Design variables for jack-up legs may involve the following listed considerations ;

-number of legs

-global orientation and positioning of the legs

-frame structure or plate structure

-cross section shape and properties

-number of chords per leg

-configuration of bracings

-cross-sectional shape of chords

-unopposed, or opposed pinion racks

-type of nodes (e.g. welded or non-welded (e.g. forged) nodes)

-choice of grade of material, i.e. utilisation of extra high strength steel

Method of transferring loading from (and to) the deckbox to the legs

The method of transferring the loadings from (and to) the deckbox to the legs is critical to design of the jack-up. Typical design are ;

-utilisation and design of guides (e.g. with respect to ; number, positioning, flexibility, supporting length and plane(s), gaps, etc.)

-utilisation of braking system in gearing units

-support of braking units (e.g. fixed or floating systems)

-utilisation of chocking systems

-utilisation of holding and jacking pins and the support afforded by such.

Deckbox -

The deckbox is normally designed from stiffened panel elements. The shape of the deck structure may vary considerably from being triangular in basic format to rectangular and even octagonal. The corners of the deckbox may be square or they may be rounded. Units intended for drilling are normally provided with a cantilever at the aft end of the deckbox, however, even this solution is not without exception and units with drilling derricks positioned in the middle of the deckbox structure are not unknown.

Below are some news from the web as of 13th Dec 2012, that Dalian Shipbuilding Industry Corporation Offshore and Shanghai Waigaoqiao Shipbuilding have received notifications from F&G to stop work on the jacking systems of eight JU2000E units, according to news sources.  Work has been put on hold on six jack-ups being built at Dalian under contracts awarded by Norwegian rig giant Seadrill and Houston-based drilling start-up Prospector Offshore Drilling.  

CIMC Raffles is building two F&G JU2000E jack-ups, including one for new drilling start-up Varada HVR, but it has not received any correspondence from F&G to halt work on the units.

The jacks for the JU2000E are believed to be from South Korea manufacturer where the JU3000N are sourced from a Chinese supplier. All jacks ordered by Chinese yards are believed to be fabricated under the joint efforts of the South Korean manufacturer and Chinese yard operator ZPMC, which bought F&G for $125 million in 2010.

Below video downloaded with courtesy of youtube which shows typically the sequence of jacking the rig up and down to test the smooth functioning of jacking system.

 

Refer below links in my previous posts for more of drilling jack-up relevant information  :-

http://kimwhye.blogspot.sg/2011/05/jackup-terminologies-and-types.html

http://kimwhye.blogspot.sg/2010/10/insights-of-jack-up-drilling-rig.html

http://kimwhye.blogspot.sg/2011/09/more-on-drilling-jack-up-and-some-of.html

Construction of a cantilevered bow turret for FPSO

Courtesy of MODEC

FPSO Whakaaropai

Location: Maui B Field, New Zealand

Client Name: Shell Todd Oil Services Ltd.

Installation Date: August 1996

Water Depth: 110m (361ft)

Tanker Size: 135,510 dwt

Vessel Type: MODEC Converted FPSO

Storage Capacity: 750,000 bbls

Fabrication: External Cantilevered Bow - Singapore

Vessel - Singapore

External Turret Mooring Systems provide an excellent solution for a wide range of FSO/FPSO applications.

These proven single-point mooring systems permit the vessel to freely "weathervane" 360 degrees, allowing normal operations in moderate to extreme sea conditions. External turret systems are less expensive than internal turret designs and can be delivered in a shorter period of time, making them an excellent choice for many applications. External Turret Mooring Systems can be mounted at either the bow or stern of converted tankers or new-built vessels. External turret systems are designed and built for a few risers, in shallow water, for moderate environmental conditions but pending on some customer and market requirements, turrets could be designed and extended in technology for use in harsh environments and to support a large number of risers and flow throughput. The FPSO Whakaaropai (Maui-B), offshore New Zealand, was developed to withstand 10.6m significant seas and support two large risers in 110 meters of water. The turret mooring required the design and development of a high load capacity and fatigue resistant turret and turret support system.

Design Environmental Criteria (100-year storm) :-
Significant Wave Height: 10.7m (35.1f)
Wind Velocit: 40.2m/s (74.5 knots)
Current: 1.1m/s (2.2 knots)

Mooring System :-
10-leg Chain-wire-chain asymmetric catenary:
6-in. ORQ chain, 4.375-in. ORQ +20% top chain
5.5-in. 6-Strand wire rope, 24mt and 32mt High holding power drag embedment anchors

Fluid Swivel Assembly :-
Crude Oil: 1 x 12-in. piggable toroids
(680 psi design/1,025 psi test)

Produced Gas: 1x 6-in. piggable in-line (2,550 psi design/3,850 psi test)

Riser System :- 1 x 10.5-in. Flexible riser, 1 x 4.5-in. Flexible riser

When designing turret mooring systems for ship-shaped vessels, one of the most important vessel design factors affecting the mooring line tensions is the location of the turret. The farther forward the turret is located away from the mid-ship, the easier it becomes for the vessel to weathervane into an equilibrium heading under non-collinear environments.

However, the farther away the turret is placed, the more the vertical motions at the fairleads due to the vessel pitch will increase, which could have an adverse effect on the mooring line tensions in the line dynamic mooring analysis.  When considering the total impact of the turret on the hull, the bow turret has proven more cost effective in both benign and harsh environments.

The bow turret can be configured in two ways: Integral bow turret (built within tanker bow)  or the Cantilevered bow turret as in the Whakaaropai FPSO.

 

A fully weathervaning vessel has operation expense advantages over a controlled heading limited rotation vessel, but the inherent requirements of a swivel joint for each flow path imposes practical limitations on the number of flow paths that can be provided for a fully weathervaning vessel.

Whilst all turret systems are disconnectable, the term is only used for turrets having the facility for quick connection and quick disconnection (QCQDC). Most of the turret systems that have been designed for fairly benign weather and shallow water are disconnected when typhoon is expected.

 

In 1995, one of my first project in the shipyard's subsidiary is the construction of the 750ton gross weight turret which involves alot of thick welding ( on the chain table where steel thickness ranges from 4 to 6 inches ) and there is need to understand where to use temporary bracing ( using 6-8inch diameter heavy schedule pipes) to hold the chain table reinforcement structures to prevent weld shrinkage and unexpected weld cracks. This crack could be heard with loud "explosion" sound when it happened. The chain table is main core structure that seats the big 6 metre diameter roller bearing ( costing turret designer few mils to order ) and this roller bearing allows the turret to freely weathervane so that the tanker can take up the position of the least resistance to the prevailing weather, at all times. I recalled that the stud bolts for holding this big bearing is sized approximately 2.5inch diameter by 3feet length. One person would have hard time trying to carry this heavy stud.  Bolt tensioning by hydraulic system was done on these 100plus pieces of studbolts.This stretching/elongation is maintained by the head of the bolt and the nut on the joint thereby maintaining the joint at the desired tension (Bolt tensioning).To produce clamp load, the bolt must be placed in tension. If the bolt is not stretched then there is no clamping load. The bolt start to stretch elastically (not reaching the yield), proportional to the amount of nut advancement. As the nut is further turned by the "tommy bar" the threads of the bolt and nut are forced together under enormous pressure generating friction between the mating threads and also causing tensional twisting to the body of the bolt between the clamped surfaces. The bolt is experiencing two forces simultaneously, tension and torsion.
In a bolted connection, the bolt must be stretched sufficiently to produce static preload upon the connection that is greater than the expected external load rather than the joint assembly acting upon the bolt themselves. These external loads must be known so that the proper grade, size, diameter, thread pitch and number of fasteners can be chosen to create a safe joint or fastening.


As a rule, the joint will have been designed with sufficient fastener to apply the required clamp load at 65% of the fastener proof load stress figure i.e. well below the fastener’s yield point. There is also an auto-greasing system connected by stainless steel tubing with over hundred grease outlet points around the perimeter of the roller bearing and the timing of autogrease is done through the small auto programming pack.

 

Courtesy of Bolt tight

The chain-table forms the connection point for the anchor lines of the turret mooring system to the FPSO vessel. Mooring loads are transferred from the chainhawse connection points through the chain-table structure to the turret and the main weathervaning bearing into the ship’s bow structure. The chain-table also provides the entry points for the product risers and houses the foundations for the bend restrictors (as required). The chain table after fabrication weighs about 250tons and would required to be post-weld heat treated due to the welding sizes of exceeding more than 2 inches.  A temporary shed was moved into the workshop where the chain table was completed and prepared for gas fired to heat the 250ton steel to 650degree centigrade and holding at this temperature for two hours and then letting it cool down to ambient temperature.  About 200bottle of LPG gas with 3 to 4 gas burners were mobilised to do this PWHT treatment. Spent about $70k internal insulating the shed enclosure to keep the temperature inside and preventing much heat loss to the outside. After this heat treatment process, weld stresses relieved, an Australian machining company Furmanite was called in to carry out the laser level chain table bearing surface machining.

 

The Chainstoppers and Chainhawses :-

Ten chain hawse supports, each consisting of two cast steel pieces having a hook shape, are welded to the chain-table deck. The chain hawse assemblies complete with chainstoppers are fitted into the hooks via a self lubricated bearing which allows the chain hawse to rotate and align with the chains. A tubular guide trumpet ensures proper alignment of the chain during tensioning and helps the articulation of the chainhawses.

The turret also consist of a patented design Swivel Stack Assembly. The swivel stack assembly consists of an inner non-rotating ring and an outer rotating ring that encloses a toroidal shaped chamber. The individual swivel rings are stacked atop of each other to provide multiple independent flow paths. The inner and outer ring concentricity is maintained by triple race roller bearings. Seals around the periphery of the interface between the inner and the outer rings prevent leakage of the working fluid.

The swivel design is based upon the following guiding principles:

-Swivel redundancy

-Flow re-routing as back mode of operation

-Ease of maintenance with minimum intervention
-Maximum use of field proven designs

Some design the driving arrangement of the swivel stack as integral part of the overhead frame-work structure. An individual driving ring is supported at two opposite sides by a fork arrangement. Each swivel unit is therefore driven on both sides of the outer ring simultaneously resulting in a pure driving torque with no net shear being applied on the piping flanges.  The swivel sealing system incorporates double seal sets in each module. A leak detection system and recuperation system is built-in between the seals which collects any product fluid and returns it to the production flow.  

After completion of post weld heat treatment and special laser level machining done by Furmanite, the 250ton chain table is being moved out for the main hull assembly and installation of the main 6metre diameter slew roller bearing.

Installing the main turret hull to the chain table ( left hand side )

  

                         

                                                   Above is sample setup - not actual one as I could not find from my archives machining video of chain table

Furmanite Australia was engaged to carry out machining of the approx. 6m diameter chain table. At that time, the mobilisation and machining cost for the job was almost more than quarter mil. They supply and use a range of specialized self-levelling rotary milling machine fixed to a rotating beam arm. These are ideal for use in machining very large circular or irregular shaped surfaces. Circular faces up to 45m (150 feet) or rectangular faces up to 11.5m by 11.5m (38ft x 38ft) are able to be machined in a single set up. The machines follow a reference plane electronically, utilising the strength of the item being machined for support. This allows the use of lightweight machines. The machines are highly adaptable, allowing for machining of all faces                                                       from vertical to inverted.

The machine uses a laser controlled actuating system to raise and lower the cutting head which in turn maintains the flatness and “best fit” for the service.

Capacities and range of Machining could work up to :

• CLLM : 2.5m – 24m (8’ – 80’) diameter
• Low profile CLLM : 1.8m – 4.1m (6’ – 13.5’) diameter

Leonard T. Roe - An experience driller and toolpusher

In August 2004, I was on my way to Stavangar to attend the Offshore exhibition ( similar to that of OTC yearly held in Houston, though I had been to Houston many times but never been to OTC ever ) and I had made a purpose stopover trip to London Heathrow Terminal 3 for the first time to meet up Leonard Roe ( Len, in short after we known each other ) for an interview to be our drilling engineer. I got to know Len through his "Workover" drilling website and found him likely suitable candidate to fill our company's vacant post after speaking to some other candidates of similiar triats and experience.  A fit British army in old days, Len was a toolpusher in the early 70s' and had worked for Maersk back then. I landed at Heathrow airport, it was usual over crowded and packed and but somehow it was not that difficult to find Leonard at one of the counters where you book for a cab. At first sight, Len gave me the impression of the "roughneck" type with strong and big physique. We had some food in the hotel cafe and then we move on for an "informal" interview.  Len showed me his past credentials and his working experiences and his current work as drilling well control instructor and presenter. He had given me some of powerpoint presentations and he showed me very keenly and proudly his work, how he did his animations in powerpoint. I had the whole night assessing and understanding his working experience and his knowledge in well control and offshore drilling. Flew back to office after the purposed trip and discussed about Len's work to our management. After some track record checks and reviews, we finally hired Len in November that year. Len left us 2010 and had to return UK to further his treatment on his throat and I have no idea of his present condition whether he is improving or not. He has a son in the twenties and wife is in home care due to old age. Hope Len is still around and busy with his stuff on his website, www.drillfloor.com

Part of my in-between flight schedules while on way to ONS2004 exhibition:

Wed, Aug 25: SCANDINAVIAN AIRLINES, SK 0505

From: COPENHAGEN, DENMARK (CPH) map Departs: 2:55pm
Departure Terminal: TERMINAL 3 Gate: Check for latest information
To: LONDON HEATHROW, UNITED KINGDOM (LHR) map Arrives: 3:50pm
Aircraft: MCDONNELL DOUGLAS MD-90 JET Mileage: 594
Flight Time: 1 hours and 55 minutes

Thu, Aug 26: SCANDINAVIAN AIRLINES, SK 2520
From: LONDON HEATHROW, UNITED KINGDOM (LHR) map Departs: 10:45am
Departure Terminal: TERMINAL 3 Gate: Check for latest information
To: STAVANGER, NORWAY (SVG) map Arrives: 1:30pm
Aircraft: BOEING 737 JET Mileage: 554
Flight Time: 1 hours and 45 minutes

Leonard T. Roe

Rig manager and Drilling Superintendent

 

From November 2004 until November 2010 (6 one year contracts) held in the position of consulting Principal Engineer Drilling in Singapore to assist in setting up a drilling team.  This position involve the over view of the planning and designing of the rig floor and associated drilling components, and the systems associated with the Rig Technology of the many new builds, much of the onsite involvements carried out included, rig inspections during the construction phase, function testing installed equipment, and commissioning.

Offsite involvement included, sitting in on meeting with customers, checking and suggesting the rearrangement of drawings and layouts, writing seminars and lectures for both management and engineers as and when needed. Such seminars were run in Singapore, Abu-Dubai, and India. And would often include both yard personal and many of their customers.

Leonard was a freelance training instructor and consultant compiling and instructing/teaching aids for distant learning classes on rig design and functions while recovering from cancer, many of the subject can be seen below.

Some of his Lessons written in the past include:

Casing and Cementing

Fishing tools and their functions

Stripping and Snubbing

Bops' Atmospheric d-gasser and the Accumulator, kill and choke manifolds

Drill string Design

The circulating system

Drilling Hydraulic

Oil well completions and Workover

Introduction to casing while drilling

Rig Safety

Workover operations

Ton miles and wire line safety

Bulk Storage Systems

Mud Mixing system

Solid control systems Mud Cleaning and shaker area including D-gassers

Top Drive

Rotating Mouse Holes

Fox Holes

Pipe Deck Machines

Power Slips, PS30, PS21, PS16

Iron Roughneck TS80, AD4500, AD3200, Jim

Hydraulic Cat Heads

Hydraulic Power Units

Hydraulic stabbing boards

High Pressure Piping Systems this includes Valves, All manufactures

Conductor Tensioning Units (CTU)

Diverters Vetcogray and Cameron

Rig Pumps (fluid end and power end)

The crown and crown block assembles

The Stand Pipe Manifold

The choke Manifold

The trip Tank design an function

I have uploaded here some of Len's work below which he has given personally to me for sharing,
( P/s  the correctness of the information here below are not being counter-checked and to be used with discretion )  :

Rigfloor equipment2


Rig Controls at Drill Floor



Bulk Mud System


Optimizing Solids Control


Iron Roughneck


Slush Pumps


Top drive


What is an Accumulator1



Underbalanced Drilling


Surface Cement

RC Bits


Casing 2


Gas Cut Mud

Liners



Deepwater BOP Riser


Diverter Systems


Well Head

Propeller and hull wake resistance

In ship vibration, the propeller is normally the trouble source which can cause an excessive ship vibration problem. The consequences of excessive vibration in the ship's stern area can be very detrimental to the crews' comfort. Deterioration of the structural members can be accelerated as a result of fatigue caused by long term cyclic vibration. Excessive vibration can damage or adversely impact the performance of the ship’s mechanical and electrical equipment. Prolonged exposure to vibration can contribute to crew discomfort and increasing the opportunities for human error.

Increased flexibility of the hull girder of larger, and particularly longer, ships with a fine, underwater form can significantly increase susceptibility to vibration. Moreover, as the weight and distribution of steel within ship structures are optimized as shipbuilders attempt to control production and material costs, the probability for vibration-related troubles, particularly in the stern section of the vessel, increases. As the demand for higher service speeds for many of these vessels also increases, attendant increases in the propulsive power are required. This translates into higher loads on propellers, which in turn lead to greater propeller excitation and an increase in the risk of vibration and vibration-induced failures. These create an intense, fluctuating pressure impact on the ship’s hull.

There is now the availability of modern propeller design, moderate amount of sheet cavitation is often unavoidable in order to maintain the required propulsion efficiency. Reconciling the challenges posed by these conflicting technical and operational demands is essential if further improvements in the speed-power-size ratio are to be realized, particularly for large vessels.

To study and predict propeller-induced hull vibration is not simple. It is a synthetical analysis involving methodologies of many topics such as Computational Fluid Dynamics (CFD), Finite Element Method (FEM), and fluid cavitation dynamics. In propeller induced hull vibration assessment, the prediction of stern flow is central to the problem of unsteady propeller loads, cavitation, and propeller-induced hull pressure. The solution to these problems requires detailed knowledge of the turbulent stern flow (including thick and perhaps separated boundary layers), bilge vorticity, and propeller/hull interaction. Common in ship design, the technology for these predictions was mainly based on regression and empirical formulae. At best, the use of ship flow codes was restricted to potential flow calculation augmented by boundary layer predictions to approximate viscous effects. Propeller calculations were performed using empirically generated effective wakes, and the propeller’s interaction with the hull was approximated with a thrust deduction coefficient.

The use of CFD in ship hydrodynamics has increased in the marine field. This is due to continuous advances in computational methods together with the increase in performance and affordability of computers. Also, due to the emergence of many unconventional propulsor designs such as tractor PODs, tip plate propellers, and propellers with wake equalizing ducts/spoilers, empirical methods based on the historical databases developed for conventional propeller designs become questionable in the innovative designs. More sophisticated analyses based on direct simulation using CFD and FEA methods are required to associate with the model tests for propeller-induced vibration studies.

Nowadays, with advances in CFD techniques, more comprehensive analyses can be performed for propeller/hull interaction flow problems. It has been demonstrated that CFD simulation, particularly using RANS-based methods, can provide more flow details in understanding the complex propeller/hull interaction process. This paper provides an overview of the methodologies and the state-of-the-art computational analysis tools that ABS has developed in order to more accurately estimate propeller-induced hull vibration.

The sequence of comprehensive analyses in the integrated simulation system is summarized as follows:

1. Bare hull wake field (nominal wake) simulation

2. Simulation of wake field under propeller-ship hull interaction (effective wake)

3. Propeller performance analysis (thrust and torque coefficients, K T and K Q )

4. Propeller cavitation analysis (cavity patterns on propeller blades)

5. Hydrodynamic loading assessment (pressure on blades, propeller induced hull pressure and bearing forces/moments)

6. FEM analysis for vibration and stress on ship hull, shaft and propeller blades

Resistance and propulsion summary - With courtesy from Newcastle UponTyne University
Resistance Propulsion


Global vibration on container vessel - courtesy of Delta Marine Engineering

GlobalVibration Container Vessel


Lloyds Register Ship vibration - Courtesy of Llyods Register
LR ShipVibrationNotes




Vibration Analysis and Noise Rev1



Vibration Analysis