A,B,C,D In Ship Terminology

A

Access Holes – Holes cut in the ship’s structure to permit entering or leaving various compartments.
After perpendicular – A vertical straight line at or near the after edge of the rudder post
Amidships – At the midship section of the ship
Accommodation ladder – a portable ladder on a ship’s side for people boarding from small boats or from a pier.
Aft – Near or towards the stern of the shipShip’s terms
Aftermost – The furthest aft.
Aft Peak Bulkhead – The first main transverse watertight bulkhead forward of the stern.
Anchor – A heavy object of steel attached to a vessel by a cable and/or chain and cast overboard
to keep the vessel in place.
Athwart ship – Perpendicular to the fore and aft centerline of the ship

B

Ballast – Any substance other then cargo, which is usually placed/loaded in the inner compartment of a ship to produce a desired trim or improve stability.Ship’s terms
Bay – It is an area between adjacent transverse frames or transverse bulkheads
Beam – The width of the ship at its widest point
Bilge – Internally, the lowest part of the ship.
Bilge Keel – Piece of plate set perpendicular to the ship’s shell along her bilge for reducing the rolling.
Bilge strake – It is the strake at the turn of the bilge extending outward to a point where the side rises
vertically.
Bow – The forward end of the ship.Ship’s terms
Boss – The curved swelling portion of the ship’s hull around the propeller shaft.
Breakwater – A guard plate preventing solids or liquid from sweeping into the deck.
Breast hook – A triangular plate bracket joining the port and starboard structural members at the stem.
Bridle – A V-shaped chain, wire or rope attached to a vessel being towed, to which the towline is
attached .Ship’s terms
Body plan – A drawing which shows the frame lines in elevation.
Boat deck – a deck on which the lifeboats are kept.
Bollards – A round tie posts to which the mooring lines are made fast.
Booby hatch – A watertight covering over a deck opening which is used for a stairway or ladder.
Bridge – An elevated structure extending across or over the weather deck containing the stations for the control of the ship and communications.
Bridge deck – A deck of superstructure midship Bulkhead – A vertical partition separating the
compartments in a ship.
Bulkhead deck – It is the uppermost deck to which the transverse watertight bulkheads and
shell are carried.
Bulkhead Structure – Is a transverse or longitudinal bulkhead plating with stiffeners and girders.
Bulwark – It is the vertical plating immediately above the upper edge of the main deck at side.
Butt – The joint formed when two plates are placed edge to edge

C

Cabin – An enclosed compartment of a ship used as living quarter.
Camber – The athwart ship rise of a deck.Ship’s terms

Cargo hatch – a large opening in the deck which permits loading of the cargo inside Ship.
Cargo port – an opening in the ship’s side used for loading and unloading cargo Cargo area – that part of the ship which carries cargo.
Cargo hold bulkhead – boundary bulkhead separating the cargo holds.
Carlings – supports, usually in a fore and aft direction, of flat plate/bar, welded between transverse deck beams.
Casing – covering or bulkhead around or about any space for protection.
Ceiling wood –sheathing on tank top to protect the cargo and ship structure.
Center line – middle line of the ship extending from stem to stern
Chain locker – compartment in the forward part of the ship for storing the anchor chain.
Chain pipe – A pipe for passage of chain from deck to chain locker
Classification - the certification process administered by a an agency whereby the ship is constructed and maintained to the agency’s requirements.
Cofferdams – any space between two bulkheads or decks primarily designed as a safeguard against oil leakage from one compartment to another.
Collar – a welded plate used to close a beam or frame penetration through plating.
Collision bulkhead - the foremost main transverse watertight bulkhead
Companionway - a covered stairway leading down from the open deck
Compartment - a sub-division of space or room in a ship
Confined space - a space identified by one of the following characteristics, limited opening for entry or exit, unfavorable natural ventilation or not designed for continuous worker occupancy.Ship’s terms

D

Dead rise - a rise or upward slope of the bottom of the ship from the keel to the bilge.
Deadweight – cargo carrying capacity of the ship.
Deck house - A structure on the freeboard or superstructure deck not extending from side to side.
Derrick - a device for hoisting heavy weights or cargo
Displacement - Total weight of the ship, when afloat, including every thing on board.
Discharges - any piping leading through the ship’s sides for conveying bilge water, drains, etc.
Dog - a small bent metal fitting used in closing doors,hatches etc.
Double Bottom - is the structure of the ship bounded by the bottom shell and the inner bottom plating
Doublers plate - a plate fitted over another plate for extra strength
Duct keel - is a keel built of plates in box form, extendingthe length of the cargo hold.Ship’s terms

E

Enclosed superstructure - is the superstructure with bulkheads forward and fitted with weather tight doors and closing appliances.
Erecting - the process of hoisting and joining the various parts of the ship’s hull. These parts could be in various sizes and called micro panels, panels, blocks, mega blocks.

F

Fabricate - to make assemblies from raw steel materials
Face plate - narrow stiffening plate along the edge of any frame, stiffeners or other structural members, either welded or integral part of the member.
Fairing - reforming distorted plating to its original shape

Fender - any device used to absorb the shock and prevent damage to ship’s hull when coming against a
jetty or against any other object.

Forecastle - short superstructure situated at the bow.
Foremast - the forward most mast on a vessel
Forepeak - is the area of the ship forward of the collision bulkhead.
Forepeak Bulkhead - Same as collision bulkhead

Frame spacing - the fore and aft distance between adjacent frames.
Freeboard - vertical distance from the upper watertight deck to the waterline when the ship is fully loaded.
Freeboard marks - making done amidships on both sides of the ship, to mark the position up to which the ship can load
Freeboard deck - normally the uppermost complete deck exposed to weather and sea, which has permanent means of closing all openings.
Freeing port - is an opening in the bulwarks to allow the water shipped on deck to run freely overboard.

Funnel - a smoke stack of a vessel

G

Gangway - is a raised walkway between superstructure such as between the bridge and forecastle or between bridge and poop.
Galley - kitchen of a ship
Garboard strake - the longitudinal plating next to the keel
Girder - is a collective term for primary member supporting structural members.
Girth - any specified length
Grating - light platform or walkway made up of metal bars, used for access to the machinery
Gross tonnage - overall volume of the ship.
Gunwale - is the upper edge of the ship’s side

H

Hatch – An opening in the deck for passage of cargo
Hatch Coaming - is the vertical plating built around the hatchways, to prevent the water from entering the hold.
Hatch Covers - Steel covers fitted over the hatchways to prevent the ingress on water in the holds, and also as supporting structure for the deck cargo.
Hawse pipe - a pipe passage from the deck at bow to the ship side for the passage of the anchor chain
Hawser - a large rope used for towing or mooring
Heel - inclination of the ship to one side with respect to the center line.
Hull - the body of the ship, including the shell plating,decks, bulkheads, and framing Inboard - inside the ship, toward the center line

I

Inner bottom - plating forming the upper surface of the double bottom

K

Keel - main structural member or the backbone of a ship running longitudinal along the center line of the ship.
Knot - speed unit of one nautical mile (6080 feet)
Kort nozzle - a steel ring surrounding the propeller

L

Ladder - inclined steps used on ships
Launching – process of putting the vessel in water by allowing it to slide down on greased skids.
Length between perpendiculars - length measured between the forward and aft perpendiculars.
Length overall - length of the ship measured from the extreme forward to the aftermost point of the ship.
Lightening hole - a hole cut tin a plate of a structural member to reduce the weight

List - to lean over to one side
Load waterline - line of surface of a ship when loaded to its waterline
Longitudinal - a shell, deck or a stiffener running in a fore and aft direction

M

Main Deck – usually the uppermost continuous deck
Mast – a pole or similar structure on which the lights, and signals can be placed or displayed.
Manhole – a opening in a deck or any other member, which provides access for a man
Midship – at or near the middle point of a ship
Midship section – a cross section through the middle of a ship.
Mooring – securing a after deducting the total volume for certain ship by several lines or cables

N

Net tonnage – the figure spaces which can not be used for cargo

O

Outboard – away from the center line of the ship
Overboard – outside, over the side of the ship into water

P

Peak – a narrow compartment at either end of the ship
Pillar – a vertical member which provides support to a deck girder
Pintle – a pin on which the rudder hinges
Poop – a space below an enclosed superstructure at extreme aft end of the ship
Poop deck – first deck above main deck at aft end.
Port – The left hand side of the ship when looking towards forward side
Porthole – a circular opening in ship’s side for ventilation and natural lighting.
Profile – a side elevation of the ship
Propeller – a rotating device which drives the ship through the water

R

Rigging – ropes, masts, wire ropes, lashings etc.
Roll – motion of the ship from side to side
Rudder – a flat piece of steel attached upright to the stern post at the stern by pintles, gudgeons or hinges, so that it can be turned, causing the vessel to turn.
Rudder Post – after post of the stern frame to which the rudder is attached.Ship’s terms
Rudder Stock – shank of the rudder which extends from the rudder to the steering gear

S

Sagging – straining of the ship which makes the middle portion of the ship lower than the aft and the forward end

Scupper – a deck drain
Scuttle – a small opening in deck or shell usually fitted with a cover, for access to a compartment
Sea chest – a compartment through which the sea water is admitted or discharged
Shedder Pates – slanted plates fitted in dry cargo holds to prevent undesired pockets of cargo.
Sheer strake – top strake of a ship’s side
Shell Expansion – a plan showing all the shell plates.
Skeg – a framed steel plate structure which acts as a fixed rudder under the stern
Sheer – an upward curvature of a ship’s deck in the fore and aft direction
Shell plates – plates forming the outer skin of the ship
Skylight – an opening in the deck to give to give air and light to the compartment below
Starboard – the right hand side of a ship when looking forward.
Stem – a piece of bar or plating on which the ship’s outside plating terminates
Stern – aftermost part of the ship.
Stern frame – a heavy strength member in single screw ship combining the rudder post
Stern tube – a long bushing or bearing through the stern to support the end of the propeller shaft
Stiffener – a collective term for the secondary supporting structural members
Stool – a structure supporting the cargo hold and tank bulkheads
Strake – a row of shell, deck, bulkhead or other plating
Strength deck – normally the uppermost continuous deck
Stringer – a fore and aft member used to give longitudinal strength
Stringer plate – deck plating which contacts the shellShip’s terms
Superstructure – decked structure on the freeboard deck extending for at least 96 % of the breadth of the ship

T

Tank top – plating over the double bottom
Tail shaft – a short portion of the propeller shaft passing through the stern tube and carrying the propeller
Tween decks – abbreviation for between decks, placed between the upper deck and the tank top
Trunk – a small casing passing through the deck, used for ladders or ventilation

V

Void Space – an empty space in a ship

W

Weather deck – a deck exposed to the weather
Web frame – a frame with a deep web
Windlass - a machine used to hoist the anchors.

# Various books, study material and other online sources has been refereed prior to writing this article but no major part is copied or produced  from any of the source but explained same thing in better detailed way.

Main reference source: Ship Terms by " Society of naval architecture students, Cochin" By Arjun k bharath.

(If you have any problem / Complain regarding the post please do contact us !)

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Author Amit                                                                            

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D.P Vessel | What it mean,Do and how it work?

D.P Vessel stands for dynamic positioning vessel which maintains its position (fixed location or predetermined track) by means of active thrusters. These vessels does not need anchors to dock and can stay fixed to any position on the sea based on satellite g.p.s signals with a precession of 99.9% making it more safer and reliable. The advantages fully operated by DP ships include the ability to operate with a positioning with the precision and flexibility to define the position and enable rapid positioning without the need for anchorage. This made d.p vessels quite useful, maybe the only reliable source for research/Exploration/Drilling(Sea bed).

What is D.P(Dynamic Positioning ) Vessel used for?

D.p vessels are used worldwide mostly by Deep sea explorers, Scientists and deep sea oil diggers in the form of semi submersible oil rig, offshore support vessel, and Research ship. They are used over others types of ship in these work as for digging for oil one need to be very steady to avoid any uneven stress being generated during digging sea bed, It is so in the case of deep sea diving where for the divers safety the ship must not move much from its original position as it may break life line connected to the divers during exploration. It is also required to stay steady during bringing something off-sea from the sea bed with the help of crane to avoid unwanted drag and forces to be eliminated.

"Typical DP ships include survey ships, drilling vessels, work boats, Drilling platforms, diving support vessels, cable layers, and supply vessels."

How does D.P(Dynamic Positioning ) vessel work?

The first DP vessel was used in the early 1960s and work on conventional PID controllers in cascade with low-pass notch filters to suppress the first-order wave-induced motion components. But from the mid-1970s, more advanced and sophisticated control techniques were proposed based on linear optimal control and Kalman filter theory.

A computer control system automatically keeps the position and direction of a ship's with the help of its own propellers and engines. Positional reference sensors, combined with wind sensors, motion sensors and gyroscopes provide information to the DP computer  about the position of the ship and the magnitude and direction of the environmental forces (wind and waves) that can influence their position.

The computer program contains a mathematical model of the ship containing information about the air resistance and the ship's current location and propellant. This knowledge, combined with sensor information, allows the computer to calculate the steering angle and the force required for each pressure propeller.

Image credit: wikimedia.org/wikipedia.org

Class Requirement

Based on the publication of IMO (International Maritime Organization) the classification societies have described rules for dynamically positioned vessels under Class 1, Class 2 and Class 3.

• Class 1 devices do not have redundancy. The loss of position in case of a single error can occur anytime.
• The class 2 team redundancy, so no single error in an active system causes the system failure. The loss should not occur due to a component fault or an active system, such as generators, engines, tables, remote control valves, etc., but may occur after a failure of static component, such as cables, pipes, manual valves, etc.
• Class team 3 must also be able to withstand fire or high water in a compartment without system failure. Loss position will not be expected for failure, which includes a subdivision in fire/water or flooding in completely sealed chamber.

Different Class have different rules for D.p vessels in compliance with IMO Rule.

# Various books, study material and other online sources has been refereed prior to writing this article but no part is copied or produced  from any of the source but explained same thing in better detailed way.

Cover image Credit: http://www.offshoreenergytoday.com

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Author Amit                                                                         Article Requested By: Indralal Gunaratna

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Unmanned machinery space| essential requirements,Safety precautions and checks

UMS Stands for Unmanned or Unattended machinery space. The sole purpose of UMS is to ensure safe and efficient working of all machineries on board ship under all circumstances.

UMS ships in recent years has increased rapidly. The control systems are much more reliable than they were when first applied to ships. Most owners are understanding the need for training of their crews to understand control functions. In the future, further ships will be equipped with remote control systems as a means to reduce crew.

Today, however, many other boats/ships work on UMS. Crews familiar with the systems and training are the most productive. In the immediate future owners take UMS not only as a way to reduce the crew to a minimum and reduce the operating costs, but also for security reasons.

Basic Requirements for operation of UMS:

• central control:
  A central control room, which is easily accessible, should be equiped with instrumentation and adequate equipment. The equipment installed in must be able to monitor and operate all main and auxiliary machines.
• Automatic fire alarm system:
  A fire alarm system that works very quickly, you must also be able to deliver early warning of fire in the engine rooms, in particular for the following:
  (A) The boiler
  (B) The Scavenge air belt of the Main Engine
  C)  The Crankcase of the Main Engine
  Oil mist detectors must be installed motors 2250 kilowatts or more, or if the motor is greater than 300 mm, especially in explosive areas. These sensors are numerous, well set up and react quickly.
• Integrated alarm system machines:
  This system must be able to show an abnormality of machines, to bridges and accommodation spaces including the cabin service technician, senior engineer's cabin and all public spaces.
  The power supply of the alarm system must have a standard telephone emergency help in case of power failure, and it should be an alarm to indicate this condition.
• A fire control station:
  In addition to conventional portable fire extinguishers, it is imperative to have a fire station located remotely in space machines. The station must facilitate monitoring of the emergency pumps, generators, valves, fans etc., extinguishing agent.
• Automatic alarms for bilge pump systems:
  To protect against flooding, shafts should be monitored for excessive levels under normal heel angle and trim. For the automatic bilge pumps an alarm must be provided "long-term". This indicates overloading of the wedge and the pump which Generally do not cope with the penetration of water. They must be fitted with bilge chambers manual detection devices or with automatic alarm and pump control.
• Emergency power Generators automatically starts essential services:
  This generator is connected almost always to emergency busbars on its own separate distribution box, away from the main system. The main function of such a generator automatically overcomes the power failure or a dead vessel (Within a maximum of 45 seconds).
• Local control of essential services (manual):
  Local drivers work certain machines that can not be automatically controlled or manually controlled better.
• An automatic control system for the boiler:
  The boiler system is automatically controlled using a level regulator and amplifier; There is also a combustion control system with many safety features to prevent fire.

Safety precaution for Unmanned machinery Space:

The staff must never enter or be alone in a unmanned engine room unless when approved, or was told so by the responsible engineer officer at that time. It is not possible to perform services on machinery without permission even it is expected to be completed in a relatively short time. Before entering the Engine room at regular intervals in unmanned machinery space , so that the needs to inform said on the phone or in a civil manner. Before the room enters, the procedure of the application must be explained clearly. If necessary, consider working with a work permit.

Even if you are engineer incharge on watch must notify the bridge before attending mechanical work in the machine room. Checking the safety rules for unmanned engine room, Workers need to adhere to specific locations, and all input. It is a place of machines in a sudden start.

The unmanned engine rooms must be adequately illuminated at all times. When the machine is under the control of the bridge, the bridge must always be notified when the mechanism is called a change by the staff of the engine room, and before the machine back in the engine room.

Checks Before switching to U.M.S:

Before UMS, the service technician must ensure that all tanks i.e daily fuel oil tanks, cylinder head cooling water, lubricating oil, etc. are full. There should be an inspection of all machines and operating systems and active services in all areas of the machinery, in particular for fuel and lubrication oil leakage.

1. The main engine is on the bridge control
2. Check if all bilges and barriers are empty.
3. Test the M. E. oil mist detector,  bilge wells High Levels Alarms, test Boiler High / Low / Alarms Court if necessary
4. Check the bilge pump working automatically.
5. Make sure the DG emergency power is on backup.
6. Verify that the GD is in automatic startup.
7. Check the steering geared motors are at rest.
8. Ensure that all pumps are automatic start-up.
9. OWS check valve is attached to the rail .
10. Make sure that all fire loops are activated.
11. Check that all doors / waterproof and weather openings are closed.
12. Check that the Purifier Room and Steering Gear door is closed
13. Check alarms in cabin / public spaces and in front of the engine room is working.
14. Inform bridge and confirm UMS before leaving E/R
15. Make sure that all flammable liquids in airtight containers.
16. Check whether all oil spills, etc. have been cleaned.
17. Ensure that all waste, rags and other cleaning agents are stored.
18. Ensure all the gears of the engine room, spare parts, etc. they are safe.
19. Ensure that all alarms are active.
20. Check if all fire detection sensors are active.
21. Make sure that all fire doors are closed.
22. Test the “Deadman” alarm and Engineer’s Call Alarms, ensuring they are sounding in public rooms, Bridge, Cargo Offices and appropriate cabins.

As soon as you have completed the checklist, the machine room "UMS mode" alarms must be set and the bridge has to be informed about the machine room and service technicians. A notation should be made in the logbook of the engine compartment.

*Topic "Before Going UMS" from http://www.machineryspaces.com/unmanned-machinery-spaces.html has been used as a reference during writing Topic "Checks Before switching to U.M.S" on this post. (If you have any problem regarding this post contact us!)

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Author Amit                                                                            

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What is stern tube? its working and function

The Stern tube is a narrow hole in the hull structure at the rear end of the ship/boat that connects the propulsion shaft and the engine and the propeller. Purpose of Stern tube is to support the shaft. It forms the after bearing for the propeller shaft and to make water tight joint/gland where the shaft passes through the hull.

Two types of stern tubes are in common use, one with water lubricated bearings with the after end open to the sea & the other type is closed at both ends and has metal bearing surfaces lubricated by oil.

Water lubricated stern tube

Image credit: http://www.marineengineering.org.uk

• The tube is usually constructed of cast steel with a flange at its forward end & a thread at the aft end.
• Also at the aft end, tube has small flange cast on it. ( we can say this as collar)
• the tube is inserted from the forward end and the flange is bolted to the aft peak bulkhead with a gasket to ensure water-tightness.
• A steel nut placed on the thread at aft end retain the tube in position with its collar hard against the stern frame.
• Inside the tube is a brass bush which has grooves in it, running fore and aft.
• Strips of lignum vitae ( a resinous dense hardwood) are fitted into these grooves to act as bearing for the shaft.
• Small spaces are left between the lignum vitae strips. Through these spaces water can enter to lubricate and cool the shaft.
• A check ring bolted on the after end of the tube, keeps the strips in place.
• A stuffing box/water tight gland  is fitted at the fore end of the tube ----- to prevent water from getting into machinery or tunnel space but slight leakage is allowed to ensure cooling of this packing.
• A brass/gunmetal liner is shrunk fitted to the tail end shaft, usually for the full length of the stern tube.
• Bearing length is 4 times the shaft diameter.

Advantage:

1. Natural lubrication assisted by SW.
2. Predictable wear rate allows scheduling of dry-docking in advance. 
3. No sophisticated forward/aft seals required. 
4. No chances of pollution due to leakage of oil into water as in case of oil lubricated type.

Nearly all outboard bearings were water lubricated until about 1960, when transition to oil lubricated bearing begin due to following drawbacks:

Excessive wear-down of bearing materials was caused by the trend to larger ship sizes, which had higher bearing loads. Also Larger ships generally operate at deeper drafts; and with less clearance between the hull and the channel bottom more contaminants, such as silt, mud and sand are drawn into the bearing clearance causing their wear down.

Poor quality of work when rewooding, inferior materials, presence of sand, sediments in the water required early rewooding. Vessels with engine aft, and particularly tankers & ore carriers which spend long periods in ballast sometimes rewooding is required in 18 months. Shaft needs extra liner for SW corrosion protection.

By using oil lubricated stern tube bearings above problems can be eliminated. Oil lubricated stern tube bearings also reduce the power loss in the shafting system. Also oil is better vibration damper & superior lubricant than water

Oil lubricated Stern tube

• White metal lined with oil grooves , cast iron or bronze  bush replaces wood lined brass bush.
• Shaft is protected from metal-to-metal contact  with bearing by oil lubrication which  is supplied from a header tank in the Engine Room.
• a minimum bearing length of 2 times of shaft diameter will ensure that bearing load does not exceed 0.8N/mm2
• propeller shaft has 2 short rotating liners of chrome steel.
• Liner at after end is bolted to the Propeller boss. Inboard liner is fixed by clamping ring.

Aft Seal

It is composed of casing fixed to stern frame and chrome steel liner which is  fixed to propeller boss & rotates with propeller shaft. Ingress of sea-water is prevented by fitting a rubber sealing ring between Propeller boss and the chrome liner.

The casing which is stationary part consists of 3 types of metal rings:-Flange ring, Intermediate rings and Cover rings which are tightened to each other with bolts. These metal rings contains the sealing rings which may be 3 or 4. In our case we discuss 3 sealing rings. The leading edge(lips) of the rings are pressed hard against the rotating liner by the water and oil pressures, elasticity of the rubber material and the tightening force of the springs to maintain sealing effect.
The sealing rings are numbered 1,2,3 from the SW side.

Two outer sealing rings (made of VITON or NITRILE BUTADIENE RUBBER also called NBR which is oil & water resistant) are fitted to prevent SW penetrating the lub oil space. Viton sealing rings are particularly excellent in heat resistant property.Sealing ring also has the function of protecting the inside of the stern tube from the foreign matter in the SW.

Inner sealing ring fitted in the opposite fashion, prevents the oil in the stern tube leaking into the sea. Garter spring --- held the sealing rings on rotating chrome liner.

Normally 2 gravity tanks (High & Low) are provided for oiling for deep draft and shallow draft condition so that oil pressure can be set approx 0.2 to 0.3 bar more then SW pressure applied to the centre of tail shaft so as to prevent SW from penetrating into the S/T. Please follow the specific instructions while changing over from high to low gravity tank & vice versa.

Forward Seal

It is of similar construction to the aft seal. Only 2 sealing rings are used running against on chrome liner preventing leakage of oil into Engine Room. Oil is supplied by gravity tank installed approx 0.5 m above the top of the casing.

Disadvantage of Oil lubricates seals:

1. White metal debris may choke and restrict oil supply, speeding up failure.
2. Contaminated oil supply, causes abrasive wear.
3. Lack of oil supply can happen due to low level in header tank/obstructed flow/damaged pipework.
4. If using high gravity tank in ballast condition, chance of oil leakage into sea (in case of seal failure), causing oil pollution.

Stern Tube wear down measurement 

Stern tube bearing wear down is measured by Poker gauge. Values measured are recorded on the recording board in the wear down gauge. Initial measurement is taken when ship has been completed and the shafting/propeller and the seals have been installed completely.  This is the reference measurement. Measurements thereafter shall be taken normally each time the ship goes to the dock, and values measured are compared with those measured previously.

Split type stern tube (Ross-turnbull)

The roller lower half is machined in the two horizontal front and rear surfaces machined in the rear frame. The bearing is held in a vertical position by two bushes 50 tons of tap pilger, determines the thickness of the spacer around the height of the bearing. These cats also hold the two halves of the camp. The lateral positioning of the bearing is formed by two types of 30 pilgrim tonnes arranged on both sides of the carrier cat.


A bearing ring is arranged above the bearing to facilitate easy transport of the upper half of the rollers, are provided at the bottom with rolling bearing to enable transport from the lower half. After removal of the lower half of the bearing, the first cylinder is arranged below the elevator free of its mounting gaps. Then the washers are removed and the base is resting on the rollers. The weight of the propeller and the shaft is integrated into the rear by a fork support structure.

Stresses in tail shafts and stern tube

Due to the considerable weight of the propeller, the axis of the tail is subjected to bending. However, there are also other reasons which are likely possible. There is a torsional stress due to the drag torque of the propeller and the motor/engine, and a compressive stress due to the pressure support.

All these tensions, and that the tree can be in contact with highly corrosive seawater, makes the probability of an attack corrosion is very likely.

Examining a tail shaft and stern tube

1. It is necessary to measure bearing wear before regular inspection.
2. To remove the stem after thorough examination.
3. In setting bronze coating integrity of the water lubricated shaft must be checked by knocking with a hammer on its entire length to hear its hollow indicating separation.
4. Measuring the wear of the shaft.
5. Examine the button shaped cracks.
6. Replace the rubber rings.

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Author Amit                                                                            

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What is rudder and how it turns the ship? | Construction and Working

What is a rudder? It is the fin at the rear of a ship used for directing the ship?? Actually rudder is a primary control device used to steer a ship, boat, submarine or hovercraft. In simple terms it creates resistance in the water on one side or another and causes the ship to turn.

A rudder makes the boat/ship to rotate and are hollow to provide some buoyancy. To minimize any risk due to corrosion, the inner surface is applied with a protective coating and a drain plug provided to allow drainage of the water. Many of the rudders which are found on present-day ships are semi-balanced, i.e. they have a small proportion of their lateral area forward of the turning axis (less than 20 per cent). A rudder with 20 to 40% of the area before the rudder stock is considered balanced, Most modern rudders are half-balanced design. Which means a part of the force acting on the rear wheel of the water is counteracted by the force acting on the other half of rudder; Therefore, the design can be lighter and smaller. Then rudder is supported by a bearing pintle or a lower bearing according to the design.

There are two main types of rudder based on their design:

Fully fabricated Rudder:

A side plate and the strips of horizontal & vertical reinforcement is welded on the plate. Another plate, often referred to as a "top plate", is weld then only to all internal structure from the outside. Other cables entering the desert tray Welding can be achieved by sealing the plate shown in the solution slot.

Rudder with a cast Frame:

Rudders frames were welded with the side wall. Grooves in the bore of the lever, can take the shape of the solder tube with the plug hole from the bottom and the side plates and the end of the fold. To avoid corrosion in the region, where the wheels can sometimes be inert foamed plastic. On the water under the stairs in the upper surface of the top pole once tested per 2.45 m wheel.

The Rudder consists of five main parts:

1. Rudder Flap (Mentioned and explained above)
2. Rudder stock
3. Rudders bearings
4. Rudder pintles
5. Rudder trunk

Rudder Stock

Rudder stock is the vertical member at the forward edge of a rudder, hinged at the stern post and attached to the helm or steering gear. A rudder stock can be casted or forge. Diameter bending moment is preserve in every moment. Its lower end is connected to the screw bolt horizontally or vertically with respect to the wheel arrangement, which is adapted to withstand torque output. This clutch allows the navigation ease for inspection and service rolls.

Rudder Bearing

To support the weight of the spindle in the internal part of the lower part of the spindle space bearings are provided. Some types of bearings is in segment others in the housing and supported by various kinds of weight bearing Resistances blades. The waterproof steering bearings can be installed on the top edge of the cover of the steering wheel.

Rudder Pintles

A pintle is a pin or bolt, usually inserted into a gudgeon, which is used as part of a pivot or hinge. Pintles have a taper on the radius, and a bearing length which exceeds the diameter.

A gudgeon is a circular fastener, often made of metal, which is bonded to a surface. It allows you to rotate an accessory. It is generally used with an axis of rotation, which is a pivot point in the piston bore. As such is a smooth bearing pin.

Rudder Trunk

Rudder reserves carried in the trunk of the rudder, which closed at its lower end typically does not install the case, a stuffing box, but in the upper part of the trunk when the supply of the trunk intact. This log is kept sufficiently short so that the bearing does not support a minimum length, and is constructed from welded box-shaped with the crossbar forming the bottom of its end plates. The effect of the inside of the helmet in an emergency, a small opening with a cover can be closed so that these initiations are provided on one side of the inspection.

# Various books, study material and other online sources has been refereed prior to writing this article but no part is copied or produced  from any of the source but explained same thing in better detailed way.

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Author Amit                                                                            

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6 Silly reasons why you get failed in mmd examinations again and again!

You have filled documents , applied and even prepared well, even get some coaching second time but still not get through the passing grades. Have you think what went wrong all the times?

why are u failing repeatedly in MMD Exams despite writing all correct answers? Following silly mistakes may be a reason :

1. Please don't make any identification marks on your answer sheet. Also dont write your rotation no. anywhere except the place provided for the same.
2. First question is always compulsory. Start your answers from question no. 1 only. As attempting it in the last gives an impression that you don't know the subject well.
3. Do not attempt survey related questions. i.e. Boiler survey, Load line survey etc. Because these answers require specific attention on some important issues and areas, which you can miss out and this may turn out to be failing mistake.
4. Sketches leave good impression. It can be drawn free hand,but should be neat and clear. Be careful, there should not be failing mistakes in your sketch.
5. Start writing answer from the back of cover page only. Leaving that page blank may leave you disqualified from exam. Also where you finish your answer, remaining page should be struck down by single line and answer of next question must start from new page.
6. Use only one color pen, preferably black, during your exam. Please don’t use other color pen not even for headings or underlining.

#Note: The following article is property of ( Marine Republic) http://www.marinerepublic.in  and re-used with few modifications after taking due permission.

Source: http://www.marinerepublic.in/2014/09/10-tips-to-crack-mmd-written-exam.html

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Lifeboat Launching Order | Full Procedure step by step

Lifeboats and rescue boats are delivered on board ships as a means to rescue lives in emergencies. The number of rescue boats and life rafts is provided, based on the ability of these equipment and the number of ships rescue crew.

SOLAS requirements for lifeboats

• The life boat is rigid construction capable of maintaining positive stability in the upright position when loaded with a complete list of people and equipment in the calm water.
• Except in the free fall, each vessel which to be released from the drop must have sufficient strength to withstand when loaded with their full team and skates or fenders in position, a lateral impact against ship side at an impact velocity of at least 3.5m/sec and also a drop into water from a height of at least 3 mtrs.
• The rescue boat/ life boat will carry all the devices described under SOLAS that can be used in marine survival.
• The requirement of a cargo ships lifeboat with 20 000 GT is the lifeboat should be able to throw when the ship is running at a speed of 5 knots.
• The life boat should be no less than 7.3 meters long and two rescue/life boats are provided on both sides of the ship (port and starboard). The size, number and capacity of the rescue vessel of a merchant vessel are decided by vessel type and number of ships.
• Each seat position clearly on the boat must be indicated.
• The rise time for the launcher should not be less than 0.3 m / s when the vessel is loaded around the capacity.
• The life boat has to print internationally orange posters painted with glossy boot.
• The wires which lift or lower the lifeboat are known as falls and the speed of the lifeboat descent should not be more then 36m/ min which is controlled by means of centrifugal brakes.
• Regular exercise should ensure that the members of the ship's crew are able to start and lower the boat with a minimum of time in a real emergency.

 LIFEBOAT LAUNCHING ORDERS

In order to lower the boat, a minimum of 6 crew members, apart from the coxswain (steering wheel) are required.

Their duties are as follows:-
1. Bowman (Passes the painter forward & releases falls fwd.)……..AB
2. Forward gripes, harbour safety pin and painter (Removes forward gripes, checks safety pin and makes fast the painter forward)…..AB
3. Brakes-man (Operates the dead man’s handle)…….BOSUN
4. After gripes, harbor safety pin (Removes after gripes, checks safety pin )……..AB
5. Jacob’s ladder (Rig Jacob’s ladder and help passengers and crew embark the boat from the embarkation deck)……..OS
6. Stern sheet (Checks boat plug shipped in and releases falls aft)…….OS
The orders to the crew members are given by the Master as follows:-

1. “Stations”
  Upon this order, the boat’s crew proceed to their designated Stations.
2. “Clear away”
Upon this order, the boat’s crew sees that there is no obstruction for launching of the boat.
3. “Unship the safety pins”
Upon this order, No.2 and No.4 check and unship the harbor safety pins forward and aft, if required.
4. “Let go gripes forward and aft”
Upon this order No.2 and No.4 let go the fwd. and after gripes. Make sure that the gripes triggers have fallen. The bowman passes the painter well forward making sure that it is well clear. The stern-sheet sees that the rudder is free and boat plug is shipped. The bowman and stern sheet make sure that the falls are clear and life lines are secured.
5. “Lower the boat to the embarkation deck”
Upon this order the brakes-man lowers the boat to the embarkation  deck by gradually releasing the hand brake. Every time the boat is lowered, the coxswain and the bakes-man must make sure that the crank handle is unshipped (especially if the boat was hoisted earlier with the crank handle) otherwise when boat is lowered,   this may injure the brakes-man and any other person in the vicinity. The brakes-man will lower the boat by the brake and the boats moves on track-ways, till the tricing pendants have brought the boats alongside to the embarkation deck. The full weight of the boat should not be allowed to come on tricing pendant. If the brakes-man releases the brake and the boat does not come down, that means there is some obstruction preventing the boat from sliding on the track-ways. The obstruction should be removed.
6.  “Make fast bowsing in tackles”
Upon this order, the bowman and the stern sheet from the boat hook up the bowsing in tackles on to the floating blocks and on the ring bolts provided on the ship’s side, or on the gravity davits, making sure that the hauling parts are hooked on the ship-side. Then haul on the bowsing in tackles taut and make fast in the boat. The purpose of the bowsing in tackles is to keep the boat alongside the embarkation deck.
7.  “Let go tricing pendant”
Upon this order, the tricing pendant must be removed and the weight of the boat is taken up by the falls and the bowsing in tackles. Tricing pedant must be released before persons are allowed to embark; that will ensure that the full weight of the boat is taken by the boat falls.
8.  “Embark passengers and crew”
Upon this order, the women and children embark first, then the rest of the passengers and finally the crew. All the persons in the boat must be seated as low as possible, away from the entrance and their hands and elbows must be off the gunwale.
9.  “Ease the bowsing in tackles”
Upon this order, the browsing in tackles are eased off and then let go. The bowsing in tackles should be detached from the falls and kept hanging on the ship-side.
10. “Lower away the boat”. The boat is lowered by the brakes-man on the crest of the waves then allowed to drop into the trough while afloat. This will overhaul the falls so that when the boat rises on the next crest, the falls can be unlocked. The bowman and sternsheet make sure that both the falls are hooked together. If however, the ship has any headway on her, it is better to let go after falls first, rather than risk the boat being towed by the after falls. In a calm sea it is better to let the boat go last 3 meters (10 feet) with run, so the boat will plunge and overhaul the falls sufficiently for them to be unhooked. After the falls are unhooked, care should be taken so that the blocks of the falls do not injure any one because blocks will swing about after they have been let go. Therefore, as soon as the blocks are released, if emergency power is available on the winch, the falls can be heaved up by the winch-man so as to be well clear of the survivors. If the power is not available, boat could be pulled little away forward by means of toggle painter, while waiting for the winch-man to come down the ladder. After the winch-man and the coxswain have come down, pass the toggle painter aft, put the tiller towards the shipside and get the boat away from the shipside and then let go the toggle painter. The boat should be pulled about ¼ mile away from the ship, then stream the sea anchor and wait for orders from the senior officer’s boat.

If the order “Still” is given whilst the boat is being swung out and lowered, everyone stops whatever he is doing. This order is given when some fault is found and there may be immediate danger of an accident taking place. When the fault is corrected “Carry on” is given.

Six easy steps to launch an open life boat are given below which are self explanatory.

Image credit and source: http://imostickers.com

 Cover image Credit: http://www.demetriadesgroup.com ( Image used for reference purpose only)

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Author Amit                                                                            Article Requested By: Prevesh pradhan

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