Steel Hatch cover arrangement for general cargo ships -How to make them watertight ?
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.
A MacGregor single-pull weather-deck hatch cover is shown in Figure.
The hatch covers are arranged to move on rollers along a track on
top of the hatch coaming. The individual covers are linked together by
chains and ride up and tip onto a stowage rack at the hatch end. A
hydraulic power unit, operated from a control box at the hatch end, is
used to open and close the hatch cover. It is possible to open and close
the covers with a single wire pull from a crane or winch.
Watertigtitness
of the closed covers is achieved by pulling them down on to a
compressible jointing strip. This is done by the use of cleats which may
be hand-operated or automatically engaged as the hatch closes.
Hatch covers below the weather decks are arranged flush with the
deck. In the arrangement shown a
self-contained hydraulik power pack with reservoir pump and motor is
mounted into a pair of hatch covers. This power pack serves the
operating cylinder for the pair of covers. Control is from a nearby point
and hydraulic piping is reduced to a minimum.
Maintenance requirements for this equipment are usually minimal but
regular inspection and servicing should be undertaken. Most hatch
covers can, if necessary, be removed manually. The means of securing the hatches and maintaining their watertightness is tested initially and at periodic surveys.
Any hatch covering used on a ship is to be of sound construction
and material, of adequate strength for the purpose for which it is used, free
from patent defect and properly maintained.
A hatch covering is not to be used unless it can be removed and
replaced, whether manually or with mechanical power, without endangering
any person. Information showing the correct replacement position is to be
clearly marked, except where hatch coverings are interchangeable or
incapable of being incorrectly replaced.
A hatch is not to be used unless the hatch covering has been
completely removed, or if not completely removed, is properly secure.
Before vessel departure, weather deck hatch covers should be
secured in the correct closed position. Whilst the vessel is at sea they
should be regularly inspected to ensure that integrity is being maintained.
All hatch covers should be properly maintained. Defective or
damaged covers should be replaced/repaired as soon as possible. All covers
and beams should only be used if they are a good fit and overlap their end
supports to an extent which is adequate but not excessive.
Hatch coaming drain channels and associated compression bars must always be well maintained and, most importantly, be free of rust. Heavily worn or corroded compression bars will damage the hatch lid rubbers and may not properly seal the hatch. Cargo claims could then result due to ingress of water into the cargo holds.
All personnel involved with the handling and/or operation of hatch
covers must be properly instructed in their handling and operation. All
stages of opening or closing hatches should be supervised by a responsible
person. When hatches are open, the area around the opening and in the
hatchways should be appropriately illuminated and guard-rails erected.
Guard-rails should be tight with stanchions secured in position, and properly
maintained. No hatch cover should be replaced contrary to information
showing the correct replacement position.
Where lifting appliances are used, they should be attached to
hatch covers from a safe position and without personnel being exposed to
the danger of falling or being trapped.
No loads should be placed over, nor work take place on, any
section of hatch cover unless it is known that the cover is properly secured
and can safely support the load.
Partly opened unguarded hatches should never be covered with
tarpaulins; this would present a serious hazard for any person walking across
the hatch. Hatch covers should not be used for any other purpose.
During operations, personnel should keep clear of the hatches and
the cover stowage positions. The area should be kept clear of all items
which might foul the covers or the handling equipment.
Special attention should be paid to the trim of the vessel when
handling mechanical covers. The hatch locking pins or preventers of rolling
hatch covers should not be removed until a check wire is fast to prevent
premature rolling when the tracking is not horizontal.
Hatch wheels should be kept greased and free from dirt and the
coaming runways and the drainage channels kept clean. The rubber sealing
joints should be properly secured and be in good condition so as to provide
a proper weathertight seal.
All locking and tightening devices should be secured in place on a
closed hatch at all times when at sea. Securing cleats should be kept
greased. Cleats, top-wedges and other tightening devices should be checked
regularly whilst at sea.
Folding hatch covers -are designed to facilitate flexible cargo handling operations
Hatch covers should be properly secured immediately after closing
or opening. They should be secured in the open position with chain
preventers or by other suitable means. No one should climb on to any
hatch cover unless it is properly secured.
Unless hatches are fitted with coamings to a height of at least 760
mm (30 inches) they should be securely covered or fenced to a height of 1
metre (39 inches) when not in use for the passage of cargo. Inspection/access hatch lids should be constructed of steel or similar material, and hinged so they can be easily and safely opened or
closed. Those on weather decks should be seated on watertight rubber
gaskets and secured weathertight by adequate dogs, side cleats or
equivalent tightening devices.
Except in the event of an emergency endangering health or safety,
no person should operate a hatch covering which is power-operated or a
ship's ramp or a retractable car-deck unless authorised to do so by a
responsible ship's officer.
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 . More .....
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. More .....
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. More .....
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. More .....
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 . More .....
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. . More .....
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.. More .....
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
. More .....
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. More .....
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 . More .....
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. More .....
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. More .....
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.. More .....
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.. More .....
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. . More .....
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 . More .....
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.. More .....
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