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Role of Classification Societies in maintaining cargo ships seaworthiness
A cargo shipper and the underwriter requested to insure a maritime risk
require some assurance that any particular vessel is structurally fit to undertake
a proposed voyage. To enable the shipper and underwriter to distinguish
the good risk from the bad a system of classification has been
formulated over a period of some two hundred years. During this period
reliable organizations have been created for the initial and continuing
inspection of ships so that classification may be assessed and maintained.
The principal maritime nations have the following classification societies:
Great Britain—Lloyd’s Register of Shipping
France—Bureau Veritas
Germany—Germanischer Lloyd
Norway—Det Norske Veritas
Italy—Registro Italiano Navale
United States of America—American Bureau of Shipping
Russia—Russian Register of Shipping
Japan—Nippon Kaiji Kyokai
These classification societies publish rules and regulations which are principally
concerned with the strength of the ship, the provision of adequate
equipment, and the reliability of the machinery. Ships may be built in any
country to a particular classification society’s rules, and they are not
restricted to classification by the relevant society of the country where they
are built. Classification is not compulsory but the shipowner with an
unclassed ship will be required to satisfy governmental regulating bodies
that it has sufficient structural strength for assignment of a load line and
issue of a safety construction certificate.
Steel ships built in accordance with classification societies rules
or equivalent standards, are assigned a class in their Register Book, and
continue to be classed so long as they are maintained in accordance with
the Rules.
Developing Structural Design Programs for use by shipyards
In recent years the principal classification societies have developed software
packages for use by shipyards which incorporate dynamic-based
criteria for the scantlings, structural arrangements and details of ship
structures. This was a response to a perception that the traditional semiempirical
published classification rules based on experience could be
inadequate for new and larger vessel trends.
The computer programs made
available to shipyards incorporate a realistic representation of the dynamic
loads likely to be experienced by the ship and are used to determine the
scantlings and investigate the structural responses of critical areas of the
ship’s structure. They include a program for fatigue design assessment
(FDA) which is commonly used to assess the structural design detail of
large container ships, tankers and bulk carriers. Evaluation of the structural
design by means of these programs can result in the ship being assigned
further relevant notations.
42 Ships Detained Due To Structural Safety, Load Lines Deficiencies
The Concentrated Inspection Campaign (CIC) on Structural Safety and the International Convention on Load Lines on Tuesday issued preliminary results carried out in the Paris MoU region between September 1, 2011 and November 30, 2011. The results show - 42 ships were detained as a direct result of the CIC for deficiencies related to structural safety and load lines in the Paris MoU region. Problem areas included stability, strength and loading information, ballast and fuel tanks and water and weather tight conditions.
The CIC questionnaire was completed during 4,386 inspections on 4,250 individual ships. A total of 1,589 CIC-related deficiencies were recorded and 42 ships (1%) were detained for CIC-related deficiencies.
During the campaign most inspections concerned general cargo/multi-purpose ships with 1,563 (36%) inspections, followed by bulk carriers with 795 (18%) inspections, container ships with 495 (11%) inspections, chemical tankers with 433 (10%) inspections and oil tankers with 296 (7%) inspections. 24 (60%) ships, detained for CIC-related deficiencies, were general cargo/multipurpose ships and 5 (12%) were bulk carriers. Among the other detained ships were two container vessels, two offshore supply ships, two passenger ships and two refrigerated cargo ships. 31% of the detained ships were 30 years or older.
Analysis of the recorded deficiencies shows that most deficiencies relate to the freeboard marks (12%), ventilators, air pipes and casings (7%), stability/strength/loading information and instruments (7%) and ballast, fuel and other tanks (5%).
More on general cargo ship :
- Rope handling safe procedure
Ropes are made of short fibres that are spun into yarns,
which are then made into flat or twisted strands.
And the strands are spun or braided to make the finished
rope .
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Synthetic man-made ropes and hawsers
Although natural fibre ropes are still widely used throughout the marine industry, they have been superseded by synthetic fibres for a great many
purposes. Not only do the majority of synthetic ropes have greater strength
than their natural fibre counterparts, but they are more easily obtainable
and at present considerably cheaper.
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Natural fibre rope
All natural fibre rope is manufactured from manilla, sisal, hemp, coir, cotton
or flax fibres.The process of manufacture consists of twisting the fibres
into yarns and turning the yarns in an opposite direction to establish the
strands.
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Lay of Ropes and hawsers - Small Stuff descriptions
The lay of rope is a term used to describe the nature of the twist that produces the complete rope .The most common form of rope at sea is known as ‘hawser laid rope’ comprising three strands laid up right- or lefthanded.
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- Stresses in ship structures and how to mitigate
Heavy weights tend to cause a downward deflection of the deck area supporting the load .This subsequently produces stresses, with
consequent inward and outward deflections of supporting bulkheads,
depending on the position of initial loading .
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- Anchoring safe practice
Prior approaching an area for anchoring ships master should investigate fully a suitable anchoring position and conduct a planned approach including speed reduction in ample time and orienting the ships head prior anchoring to same as similar sized vessels around or stem the tide or wind whichever is stronger . Final decision to be made on method of anchoring to be used , the number of shackles , the depth of water, expected weather and holding ground. .
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- MacGregor single-pull weather-deck hatch cover
Hatch covers are used to close off the hatch opening and make it
watertight. Wooden hatch covers, consisting of beams and boards over
the opening and covered with tarpaulins, were once used but are no
longer fitted. Steel hatch covers, comprising a number of linked steel
covers, are now fitted universally. Various designs exist for particular
applications, but most offer simple and quick opening and closing,
which speed up the cargo handling operation..
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- Cargo holds access arrangement
The access shall be separate from the hatchway opening, and shall be by a stairway if possible. A fixed ladder, or a line of fixed rungs, shall have no point where they fill a reverse slope
.
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- Prepare cargo holds prior loading
Washing is always carried out after the compartment has been swept. Drying time for washed compartments must be allowed for, before loading the next cargo; this time will vary with the climate, but two to three days must be expected.
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- Strength and stability of the Lifting appliances
The vessel's structure, crane, derrick or other lifting device and the supporting structure should be of sufficient strength to withstand the loads
that will be imposed when operating at its maximum load moment .
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- Lifting appliances - Maintenance, testing, controls & safety measures
When there is any suspicion that any appliance or item of
equipment may have been subjected to excessive loads, exceeding the Safe
Working Load (SWL), or subjected to treatment likely to cause damage, it
should be taken out of service until it can be subjected to a thorough
examination by a competent person.
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- Safe operation of Lifting appliances and gears
All lifting operations must be properly planned, appropriately
supervised and carried out to protect the safety of workers.
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- Derricks for lifting cargo on board
Derricks for lifting cargo on board is required to be of adequate strength and stability for each load, having regard in particular to the stress induced at its mounting or fixing points , securely anchored, adequately ballasted or counterbalanced and supported by outriggers
as necessary to ensure its stability when lifting.
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- Deck cranes
Deck cranes have a number of advantages, the rigging
time being negligible, and the crane is able to pick up and land permitted
loads anywhere within its working radius. The safe working loads of cranes
is generally of the order of 10 to 15 tonnes and larger cranes are available
capable of lifts from 30 to 40 tonnes..
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- Characteristics of Marine paints
Paint consists of pigment dispersed in a liquid referred to as the ‘vehicle’.
When spread out thinly the vehicle changes in time to an adherent dry film.
The drying may take place through one of the following processes..
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- Protection by Means of Paints
It is often assumed that all paint coatings prevent attack on the metal
covered simply by excluding the corrosive agency, whether air or water. This
is often the main and sometimes the only form of protection; however there
are many paints which afford protection even though they present a porous
surface or contain various discontinuities. .
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- Role classification societies maintaining seaworthiness of vessels
classification societies publish rules and regulations which are principally concerned with the strength of the ship, the provision of adequate equipment, and the reliability of the machinery .
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- Periodic survey requirement by classification societies
To maintain the assigned class all steel ships are required to be surveyed and examined by the Society’s
surveyors at regular periods.
The major hull items to be examined at these surveys only are discussed
here..
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