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Forum Pelaut (Jalesviva Jaya Mahe)

Sunday, April 18, 2010

STABILITY NOMENCLATURE




1. K = Keel
2. G = Center of gravity
3. B = Center of Buoyancy
4. M = Metacentre
5. ø = Angle of Heel
6. BM = Metacentric Radius
7. GM = Metacentric Height
8. GZ = Righting Lever measured from G
9. KB = Height of Center of Buoyancy from keel
10. KG = Height of Center of Gravity from keel
11. KM = Height of Metacenter from keel

KM = KG + GM
KM = KB + BM
GZ = KN - KG x sin ø where KN can be found from KN curves
Righting Moment = Δ x GZ where Δ = displacement


CALCULATION OF KG

KG = Total Vertical Moment of Weights about keel [metre.tonnes]
Δ [tonnes]

GG1 = Moment of Weight,W shifted over Distance, D [metre.tonnes]
Δ [tonnes]
: vertical shift of G

CALCULATION OF KM

KM = KB + BM

KB = 0.53 x Draft [metre]

BM = 2nd moment of waterplane area = I [metre]
volume of displacement V

where I = L x B3 [metre4] for a rectangular barge
12

CALCULATION OF GM

GM = KM - KG


VIRTUAL LOSS OF GM DUE TO FREE SURFACE

GGv = s.g. of Liquid in the Tank x I x 1
s.g. of Water in which vessel floats V n2

where GGv = virtual rise in G or deduction in G

I = 2nd moment of the free surface about the centre line

= L x B3 [metre4] for a rectangular compartment
12

L = Length of the Tank [metre]

B = Breadth of the Tank [metre]

V = Volume of the Tank [metre3]

n = number of longitudinal compartments into which the tank is
subdivided



CHANGE OF TRIM


- the difference between initial trim and final trim i.e. change of draught forward + change of draught aft

Trimming Moment = Weight x Distance shifted = W x d [tonnes.metre]

Change of Trim, t = Trimming Moment [metre]
100 x MCT.1cm

MCT.1cm = Moment To Change Trim by 1 cm

= Δ x GM L [tonnes.metre]
100 x L

≅ Δ x BM L [as GML is small when compared with BML]
100 x L

where Δ = displacement [tonnes]

GM L = Longitudinal Metacentric Height

BM L = height of the longitudinal metacentre, ML
above centre of buoyancy, B

GML = KB + BML - KG [metre]

where BML = long. 2nd mmt of waterplane about centre of flotation, F
volume of displacement

= I L [metre]
V

Change of draught aft, ta = l a x change of trim [metre]
L

Change of draught forward, tf = l f x change of trim [metre]
L

Change in mean draught = Weight loaded or discharged [metre]
TPC

TPC = Tonnes per Centimetre Immersion

= Aw x ρ
100

where Aw = area of waterplane [metre2]
= L x B x Cw (waterplane area coefficient)

ρ = density of sea water [tonnes per metre3]


LARGE CHANGE IN DISPLACEMENT

Trimming Moment = Δ x (longitudinal separation LCG and LCB)

where LCG = Longitudinal centre of gravity [metre]

LCB = Longitudinal centre of buoyancy [metre]


CHANGE IN DENSITY



Change in Mean draught due to change in density = Δ x (ρ1 - ρ2)
Aw (ρ1.ρ2)

Trimming Moment = Δ x (horizontal shift of LCB)

or (mass of layer of water added or removed due to change in density) x
(horizontal distance between initial LCB & final LCF of waterplane)



3




1. δLat = difference in Latitude between the 2 points, N or S
2. δLong = difference in Longitude between the 2 points, E or W
3. θm = mid-Latitude
4. θc = Course
5. D = Distance
6. p = Departure


COURSE

tan θc = cos θm x δLong
δLat


DISTANCE

Distance = 1
cos θc


ARRIVAL POSITION


Difference of Latitude = D x cos θc

Difference of Longitude = D x sin θc
cos θm
4.
PARALLEL OPERATION OF 2 PUMPS
- with single common Intake and Discharge

Total combined Discharge Head or Pressure

= ½ (Discharge Head at 1st Pump + Discharge Head at 2nd Pump)


Total combined Discharge Capacity

= (Capacity at 1st Pump + Capacity at 2nd Pump)


SERIES OPERATION OF 2 PUMPS
- with single common Intake and Discharge

Total combined Discharge Head or Pressure

= (Discharge Head at 1st Pump + Discharge Head at 2nd Pump)


Total combined Discharge Capacity

= ½(Capacity at 1st Pump + Capacity at 2nd Pump)

To Top

5. HYDROSTATIC PRESSURE

Pressure at any point in a fluid = ρ x g x h [KN/m2]

where ρ = density of liquid [tonnes/metre3]

g = 9.81 [metre/second2]

h = distance of the point from liquid surface [metre]

HYDROSTATIC LOAD


(1) Load acting on an immersed plate = Pressure x Area
= (ρ x g x h) x A [KN]

where ρ = density of liquid [tonnes/metre3]

g = 9.81 [metre/second2]

h = centroid of the immersed area from liquid surface* [metre]

A = immersed area of the plate [metre2]


(2) Load taken by a stiffener of an immersed plate = ρ x g x h x A [KN]

where ρ = density of liquid [tonnes/metre3]

g = 9.81 [metre/second2]

h = centroid of the immersed panel area from liquid surface
= depth of immersion of the plate divided by 2 [metre]

A = immersed area of the rectangular panel plate supported by
the stiffener
= width of panel x depth of immersion [metre2]


CENTRE OF PRESSURE
- the point of an immersed plate at which the resultant hydrostatic load acts.

Centre of pressure from liquid surface

= 2nd moment of area of immersed area about surface
1st moment of immersed area about surface

= I + A(h)2 [metre]
A(h)

where I = I NA [metre4]
= 2nd moment of area of the immersed area about
the neutral axis which is parallel to the liquid surface

A = immersed area [metre2]

h = position of the neutral axis from the surface [metre]
= centroid of the immersed area from the liquid surface


CALCULATION OF CENTROID

Centroid of immersed area from liquid surface = Σ (A x y)
ΣA

where Σ(A x y) = Moment of area about liquid surface

= (A1.y1 + A2.y2 + A3.y3 + ....)

yn = distance of centroid of each immersed area, An
from the liquid surface

ΣA = total immersed area
6. SLIP

Slip = 100% - Efficiency

Efficiency = observed speed or distance
engine speed or distance

Mean Apparent Slip = distance run by propeller - distance run by ship
per Day distance run by propeller

Dist. run by propeller in n.m. = pitch [m] x total engine revolution per day
1852

6.SWL, MSL and Breaking Strain

BREAKING STRAIN

For Manilla, Breaking Strain = Circumference2 [tonnes]
2.5

For Wire, Breaking Strain = Circumference2 x 2.5 [tonnes]


SAFE WORKING LOAD

SWL = Breaking Strength
Safety Factor


MAXIMUM SECURING LOAD (MSL)

Material MSL
Shackles, rings, deck eyes, turnbuckles made of mild steel 50% of Breaking Strength
Fibre rope 33% of Breaking Strength
Wire rope (single use) 80% of Breaking Strength
Wire rope (re-useable) 30% of Breaking Strength
Steel band (single use) 70% of Breaking Strength
Chains made of mild steel 50% of Breaking Strength
Chains made of high tensile steel 33% of Breaking Strength

In a combination of securing gear with different MSL for lashing, the overall lashing strength would equal the weakest link used, i.e. the gear with the smallest MSL.

To Top

7. PROPELLER PITCH

- the distance advanced by one turn of the propeller

Pitch = 2 x π x r x y [metre]
x

Sunday, April 4, 2010

ULCC
stand for Ultra Large Crude Carrier, i.e. a crude oil tanker with deadweight more than 300,000 tons

VLCC
stand for Very Large Crude Carrier, i.e. a crude oil tanker with deadweight between 200,000 and 300,000 tons
Click to save a copy of the term's definition to My Dictionary

FPSO
stand for Floating Production Storage and Offloading; FPSO is a specialised vessel moored at sea to receive the crude oil directly from seabed, and provided with means to process, store and offload oil to conventional tankers coming to it; compare to FSO , it incorporates production facilities

FSO
stand for Floating Storage and Offloading; FSO is a specialised vessel moored at sea to receive stabilised crude oil directly from seabed, and provided with means to store and offload oil to conventional tankers coming to it; unlike FPSO , it is not equipped with processing facilities

TWIN SCREW

twin screws twin propellers, one on each of centreline, rotate in opposite directions during operation

CPP

controllable pitch propeller
a propeller with blades that can be rotated in position to achieve ahead, astern or neutral thrust, the main engine only needs to run in a constant direction; also known as variable pitch propeller or CPP for short
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A I S

Automatic Identification System AIS for Ship is an electronic ship identification system for ship to ship collision avoidance, provides information and status of ships and their cargo onboard to other ships or shore parties and vessel traffic system in ports.

The AIS can be integrated to ship navigational equipment onboard, e.g. radar or electronic charts system to indicate the ships in vicinity.

The system also transmits information to the shore, a Ship to Shore information. This is extremely useful for Vessel Traffic Systems (VTS), guiding the ship in congested areas, but equally important for the Marine Rescue Co-ordination Centres (MRCC) in giving actual updated information on all ships participating in a rescue action. Compiled information from larger areas can give the authorities basic data for planning of fairways and routing systems.

The information provided by AIS consists of
the information sent between the ships and to and from the shore which comes in four categories:

1. Static information: ships standard details for identification purpose, e.g. the MMSI number, IMO number, call sign and name, length and beam, position for GNSS antenna, type of ship

2. Dynamic information: updated continuously at a rate varying from two seconds to three minutes depending upon traffic situation, e.g. position, time, speed, course over ground, heading, navigational status and rate of turn. The faster the ship runs, the more it has to update its position

3. Voyage related information: ships actual draft and cargo type e.g. dangerous cargo (DG), destination and estimated time of arrival (ETA)

4. Safety related information: short messages on weather conditions and navigational warnings transmitted from shore to ship
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SART Search and Rescue radar Transponder, a safety equipment to give a clearer indication of the position of the vessel when activated by boosting the signal received by a searching radar; usually carried in pair for larger ships

radar stands for Radio Detection and Ranging; an electronic equipment that uses radio pulse to determine the bearing and distance to objects

superheater
a bank of steel tubes placed in the path of the exhaust gases from the furnace; the waste heat in the gases is utilised to heat up the dry saturated steam flowing through the tubes at constant presssure to obtain superheated steam
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furnace
combustion chamber of a boiler into which fuel is injected for burning
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forced draught
combustion air for boiler furnace supplied under pressure from a forced draught fan

normalising a heat treatment process similar to annealing except that the metal cools more quickly to increase the strength, toughness and hardness; the metal is allowed to cool in still air rather than in the furnace
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Scotch boiler a large diameter cylindrical boiler with three or four furnaces connected at the back end to form a combustion chamber; combustion gases coming from the individual furnace into the chamber then passes through smoke tubes to the funnel uptake; the boiler water immerses the furnaces, chambers and tubes; suitable for comparatively low pressure operation around 15 bar; for higher pressure application, water tube boiler is used; sometimes known as smoke tube boiler

superheater a bank of steel tubes placed in the path of the exhaust gases from the furnace; the waste heat in the gases is utilised to heat up the dry saturated steam flowing through the tubes at constant presssure to obtain superheated steam

Friday, April 2, 2010

dictionary

Shipbroking and Chaertering Practice (Business of Shipping)
AIS
Automatic Identification System

AMVER
Automated Mutual-Assistance Vessel Rescue System: a worldwide voluntary system operated exclusively to support SAR and to make information available to all RCCs

ARCS
Admiralty Raster Chart Service: electronic raster charts produced by the United Kingdom Hydrographic Office

ARPA
Automatic Radar Plotting Aid

ASF
Additional Secondary Factor: corrections to be applied when plotting Loran C positions on charts to take into account variations in the conductivity of the earth’s surface over which the signals pass

ATA
Automatic Tracking Aid: electronic plotting device or radars

CES
Coast Earth Station: maritime name for an INMARSAT shore-based station linking ship earth tations with terrestrial communication networks

COLREGS
Convention on the International Regulations for Preventing Collisions at Sea, 1972, as amended

COSPAS-SARSAT
A satellite system designed to detect distress beacons transmitting on the frequency 406 MHz

DATUM
A datum is a reference system for specifying positions on the earth’s surface. Each datum is associated with a particular reference spheroid that can be different in size, orientation and relative position from the spheroids associated with other horizontal datums. Positions referred to different datums can differ by several hundred metres

DGPS
Differential Global Positioning System (see GNSS)

DOC
Document of Compliance issued to the ship operator under the ISM Code

DP
Dynamic Positioning: the ability of a ship to maintain automatically a pre-set position and heading by using her own propellers and thrusters

DPO
Dynamic Positioning Operator, usually a bridge watchkeeper

DSC
Digital Selective Calling: a technique using digital codes which enable a radio station to establish contact with, and transfer information to, another station or group of stations

EBL
Electronic Bearing Line: a radar feature

ECDIS
Electronic Chart Display and Information System

ECS
Electronic Chart System

EGC
Enhanced Group Call: part of the INMARSAT system that complements the NAVTEX system to supply SafetyNET and similar information broadcast services

ENC
Electronic Navigational Chart

EP
Estimated Position

EPA
Electronic Plotting Aid: electronic plotting device for radars

EPIRB
Emergency Position Indicating Radio Beacon: a device that transmits distress alerting signals usually via satellites

FPSO/FGSO
Floating Production, Storage and Offloading/Floating Gas Storage Offloading ship/vessel or unit: an oil/gas production facility

GLONASS
Global Navigation Satellite System (see GNSS)

GMDSS
Global Maritime Distress and Safety System: a global communications service based upon automated systems, both satellite and terrestrial, to provide distress alerting and promulgation of maritime safety information for mariners

GNSS
Global Navigation Satellite System: a worldwide position and time determination system that includes one or more satellite constellations and receivers

GOC
General Operator’s Certificate: a GMDSS radio operator’s certificate for use on ships trading beyond GMDSS Sea Area A1. This is now usually incorporated into the STCW qualifications of deck officers at the operational level.

GPS
Global Positioning System (see GNSS)

HF
High Frequency

HPR
Hydroacoustic Position Reference: a PRS often used in conjunction with DP, configured with sea-floor acoustic transponders

IAMSAR
International Aeronautical and Maritime Search and Rescue Manual: published in three volumes jointly by ICAO and IMO

IBS
Integrated Bridge System

ICAO
International Civil Aviation Organization: Montreal based United Nations intergovernmental body

IHO
International Hydrographic Organization: Monaco based intergovernmental body

ILO
International Labour Organization: Geneva based United Nations intergovernmental body, responsible for seafarers’ employment standards

IMO
International Maritime Organization: London based United Nations intergovernmental body, responsible for the safety of life at sea, including navigational rules, and the protection of the marine environment

NAVTEX
Telegraphy system for broadcasting marine weather forecasts, navigational warnings, SAR alerts and other warnings and urgent information to ships in coastal waters (up to 400 nautical miles) under the WWNWS

NBDP
Narrow-Band Direct Printing telegraphy used for radiotelex and NAVTEX

NOAA
National Oceanic and Atmospheric Administration: United States producer of electronic raster charts

OOW
Officer of the Watch

PRS
Position Reference System: a navigational sensor (e.g. DGPS) used in conjunction with a DP system

RCC
Rescue Co-ordination Centre: a unit responsible for promoting the efficient organisation of SAR services and for co-ordinating the conduct of SAR operations within a SAR region

RCDS
Raster Chart Display System

RENC
Regional Electronic Navigational Chart Co-ordinating Centre: supplier of official chart data

RNC
Raster Navigational Chart

ROC
Restricted Operator’s Certificate: a GMDSS radio operator’s certificate for use on ships trading only in GMDSS Sea Area A1 R/T Radio Telephony S-57 Edition 3 IHO’s latest transfer standard for digital hydrographic data for use with ECDIS

SafetyNET
INMARSAT service for promulgating MSI to ships on the high seas; it includes shore-to-ship relays of distress alerts and communications for SAR co-ordination

SAR
Search and Rescue/International Convention on Maritime Search and Rescue, 1979, as amended

SART
Search and Rescue Transponder: a portable radar transponder for use in survival craft, which transmits homing signals in the 9 GHz band

SENC
System Electronic Navigational Chart: a database that comprises ENC data, ENC updates and other data added by the mariner that is accessed by, and displayed on, the ECDIS

SES
Ship Earth Station: shipborne satellite communication station, used for exchanging messages with shore subscribers and ships

SMCP
Standard Marine Communication Phrases: an updated version of SMNV that includes phrases that have been developed to cover the most important safety-related fields of verbal communications

SMNV
Standard Marine Navigational Vocabulary: adopted by IMO for communications on board ship as well as for those between ship and shore

SMPEP
Shipboard Marine Pollution Emergency Plan

SMS
Safety Management System under the ISM Code

SOLAS
International Convention for the Safety of Life at Sea, 1974, as amended

SOPEP
Shipboard Oil Pollution Emergency Plan

STCW
International Convention on Standards of Training, Certification and Watchkeeping for Seafarers, 1978, as amended STCW Code Seafarers’ Training, Certification and Watchkeeping Code, appended to the STCW Convention

S-VDR
Simplified Voyage Data Recorder

TMC
Transmitting Magnetic Compass

UMS
Unmanned Machinery Space

VDR
Voyage Data Recorder

VRM
Variable Range Marker: a radar feature

VTS
Vessel Traffic Services

WEND
World Electronic Navigational Chart Database

WGS84
World Geodetic System 1984 datum

WMO
World Meteorological Organization: Geneva based United Nations intergovernmental body

WWNWS
World-Wide Navigational Warning Service: established by IMO in collaboration with IHO for the dissemination of navigational warnings to ships

WWRNS
World-Wide Radio Navigation System: terrestrial and satellite radio-navigation systems that have been accepted by IMO as capable of providing adequate position information to an unlimited number of ships

XTE
Cross Track Error

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