Ro-Ro Ships

Ro-Ro Ships

The roll-on/roll-off ship is one of the most successful types operating today. Its flexibility, ability to integrate with other transport systems and speed of operation have made it extremely popular on many shipping routes. The roll-on/roll-off ship is defined in the November 1995 amendments to Chapter II-1 of the International Convention for the Safety of Life at Sea (SOLAS), 1974 as being "a passenger ship with ro-ro cargo spaces or special category spaces..."

One of the ro-ro ship's most important roles is as a passenger/car ferry, particularly on short sea routes. But despite its commercial success, the ro-ro concept has always had its critics. There have been disturbing accidents involving different types of ro-ro ship, the worst being the sudden and catastrophic capsizing of the passenger/car ferry Herald of Free Enterprise in March 1987 and the even more tragic loss of the Estonia in September 1994.

Ro Ro Cargoes

“Roll-trailer” means a low vehicle for the carriage of cargo with one or more wheel axles on the rear and a support on the front end, which is towed or pushed in the port to and from its stowage on board the ship by a special tow-vehicle.
“Vehicle” mean any road vehicle, rail vehicle or other wheel based cargo unit.
“Vehicle securing point” means the location of a lashing point on a vehicle suitably reinforced to withstand the lashing forces.

General Recommendations
1. The cargo spaces in which Vehicles & Trailers are to be stowed should be dry, clean and free form grease and oil.
2. Vehicles and Trailers should be provided with adequate and clearly marked securing points or other equivalent means of sufficient strength to which lashings may be applied.
3. Vehicles and Trailers which are not provided with securing points should have those places where lashings may be applied, clearly marked.
4. Vehicles and Trailers which are not provided with rubber wheels or tracks with friction increasing
lower surfaces, should always be stowed on wooden dunnage or other friction increasing material such as soft boards, rubber mats etc.
5. When in stowage position, the brakes of a wheel based unit should be set.
6. Vehicles & Trailers should be secured to the ship by lashings made of material having strength and elongation characteristics at least equivalent to steel chain or wire.
7. Where possible, Vehicles & Trailers, carried as part of cargo, should be stowed close to the ship’s side or in stowage positions which are provided with sufficient securing points of sufficient strength, or be block stowed from side to side of the cargo space.
8. To prevent any lateral shifting of Vehicles & Trailers not provided with adequate securing points, such cargoes should, where practicable, be stowed close to the ship’s side and close to each other, or blocked off by other suitable units such as loaded containers, etc.
9. To prevent shifting, it is preferable to stow those cargoes in a fore- & aft direction rather than athwart ships with space around them for inspection during the voyage. If they are inevitably stowed athwart ships, additional lashing of sufficient strength may be necessary.
10. The wheels of vehicles should be blocked to prevent shifting.
11. Cargoes stowed on vehicles & trailers should be adequately secured to stowage platforms.
12. Lashings shall not be attached to lamp brackets, side guards or bumpers except those specially designed for this purpose.
13. Lashings on vehicles shall be under equal tension.
14. Only one lashing shall be attached to any one aperture, loop or lashing ring at each vehicle securing point.
15. Where practicable, the arrangement of lashings on both sides of a vehicle should be the same, and angled to provide some fore & aft restraint with an equal number pulling forward as are pulling aft.
16. The front ends of Roll trailers shall be placed on soft boards or rubber mats.
17. Caterpillar treaded vehicles such as bulldozers and cranes are prone to sliding when parked on bare steel decks owing to the low degree of frictional resistance between the threads and deck. Such vehicles shall be stowed on dunnage or soft boards before being secured.
18. Vehicles with engines should be left in gear during voyage.

Vehicle Lashings

Method of securing automobiles on board a ship

Cargo securing is basically dependent upon the securing means, the weight and type of vehicle and where it is stowed.\

The means of transport must be equipped for lashing vehicles correctly (lashings, lashing points, such as lashing rings and lashing pots and the like) When lashing belts are used care must be taken to ensure that the same number of lashing belts are used at both front and rear. If no specific loading instructions are available, such lashings are attached to special lashing rings or to the vehicle’s towing gear.

Cargo securing examples

Ro-Ro ship, special Ro-Ro ship (Car carrier)

Use lashing belts (e,g special automobile lashing belts with lever ratchet tensioner) to absorb horizontal forces in order to avoid slippage and tipping. In maritime transport, lashing belts should be tight, but not highly prestressed. The vehicles are generally secured with 2 lashing belts in the front and 2 to the rear.

On inclined surfaces (ramps) and in the case of stowage athwart ships, wheel chocks are additionally used and the number of front and rear lashing belts must be increased appropriately.

Both when applying and subsequently removing cargo securing materials, appropriate care must be taken to avoid damaging the vehicle
.
Care must furthermore be taken to ensure that
a) Only wheel chocks or stirrups of sufficient height ( height between 1/8 and 1/6 of wheel diameter ) which may be properly locked in place are used.
b) Hooks are only tensioned and not stressed to bending.
c) No damaged belts or the like are used, belts are not twisted.

If the vehicle is so equipped, its parking brake must be applied and 1st gear engaged or, in the case
of vehicles with an automatic transmission, park position selected. The steering lock must be
engaged.

There must always be sufficient number of persons employed to enable the lashing operations to
be completed before the vessel proceeds to sea.

LOADING OF VEHICLES

Before acceptance for loading, it is essential to ensure that
‐ Doors, windows and tank fillers are securely closed,
‐ The tyres are pumped up to a sufficient air pressure,
‐ External damage has been recorded and shown on the shipping documents,
‐ Installed or dismantled accessories (e.g radios, external mirrors) and spare parts are complete and in good condition,
‐ The fuel tank contains the appropriate quantity of fuel for cargo handling activities (no more than
 3 L),
‐ The automobile’s battery is functional and installed in an upright position,
‐ Or the car battery which had been disconnected for extended intermediate storage has been reconnected.

During loading & unloading operations care should be taken to ensure that
‐ The angle of the loading ramps is no more than 12° so that the vehicle under body not damaged (if necessary, such sections should be approached at an oblique angle),
‐ Experienced drivers are used,
‐ Handling personnel wear special working clothes without metal fastenings or zips,
‐ Right hand drive or left hand drive vehicles are appropriately stowed so that once the vehicle has been parked the driver can get out on the still unobstructed side.

The following general criteria should also be taken into account
‐ Admissible deck and ramp loads must not be exceeded,
‐ The storage spaces for maritime transport must be protected from direct ingress of seawater and if possible low acceleration forces should apply, (e.g stowage spaces amidships),
‐ Stowage spaces must be free from grease, oil and other friction reducing substances,
‐ Stowage spaces in which the deck surfaces may permanently be at high temps (e.g due to heated tanks) must be insulated with wooden dunnage to ensure that the tires suffer no
damage.
‐ Vehicles are generally fitted with suspension, which means that they may vibrate in the vertical and horizontal axes, so care must be taken to ensure that the spacing left between the individual vehicles is sufficient to prevent them from damaging each other due to their different vibration behaviour and to allow appropriate cargo securing to be applied. In maritime transport, care must in particular be taken to ensure that the spacing to the front is no less than 30 cms and that to the sides is no less than 10 cms.

Notes on Bow/Side opening doors on Ro-Ro Ships

Two types of bow door are provided for:
Visor doors opened by rotating upwards and outwards about a horizontal axis through two or more hinges located near the top of the door and connected to the primary structure of the door by
longitudinally arranged lifting arms, Side-opening doors opened either by rotating outwards about a
vertical axis through two or more hinges located near the outboard edges or by horizontal translation by means of linking arms arranged with pivoted attachments to the door and the ship. It is anticipated that side-opening bow doors are arranged in pairs

Precautions with side /bow doors - Side shell, bow and stern doors are to be fitted with adequate means of securing and supporting so as to be commensurate with the strength and stiffness of the
surrounding structure.

Where packing is required, the packing material is to be of a comparatively soft type, and the
supporting forces are to be carried by the steel structure only. A means is to be provided for mechanically fixing the door in the open position. Securing devices are to be simple to operate and
easily accessible

Securing devices are to be equipped with mechanical locking arrangement (self locking or separate arrangement), or are to be of the gravity type. The opening and closing systems as well as securing and locking devices are to be interlocked in such a way that they can only operate in the proper sequence.

Where hydraulic securing devices are applied, the system is to be mechanically lockable in closed
position. This means that, in the event of loss of the hydraulic fluid, the securing devices remain
locked.

The hydraulic system for securing and locking devices is to be isolated from other hydraulic circuits, when closed position.

Separate indicator lights and audible alarms are to be provided on the navigation bridge and on each operating panel to indicate that the doors are closed and that their securing and locking devices are properly positioned. The indication panel is to be provided with a lamp test function. It shall not be possible to turn off the indicator light.

For passenger ships, a water leakage detection system with audible alarm and television surveillance is to be arranged to provide an indication to the navigation bridge and to the engine control room of any leakage through the doors.

For cargo ships, a water leakage detection system with audible alarm is to be arranged to provide an indication to the navigation bridge.

An Operating and Maintenance Manual for the side shell doors and stern doors is to be provided on board and is to contain the necessary information.

Need to monitor Atmosphere in RO RO ship cargo spaces

Exhaust gases from motor vehicles contain hazardous substances. Carbon monoxide from petrol engines and nitric oxide (NO) & nitrogen dioxide (NO2) from diesel engines are released in the cargo spaces

These hazardous substances can effect people in many different way. Certain substances have a tangible, immediate effect, others only show injurious effects after a person has been exposed to them for some time.

Carbon monoxide is a colourless and odourless gas which, to a lesser or greater extent, inhibits the ability of the blood to absorb and transport oxygen. Inhalation of the gas can cause headaches, dizziness, and nausea and in extreme cases causes weakness, rapid breathing, unconsciousness and death.

Nitric oxide (NO) and nitrogen dioxide (NO2) are compounds of nitrogen and oxygen, together commonly referred to as oxides of nitrogen or NOx. NO itself is not of great concern as regards health effects; however a proportion of the NO formed will combine with oxygen to form NO2, which is of concern from the point of view of human health.

NO2 is a brown gas which has a stinging, suffocating odour. It exerts a detrimental effect on the human respiratory system. Asthmatics in particular are susceptible to exposure.

Measures
Therefore measures should be considered to minimize the health hazards. Such measures could include :
1. A reduction in exhaust gas emissions.
2. Provision of an adequate ventilation system
3. Prevention of exposure to the gases

To ensure the effectiveness of above recommended measures, it is essential that the atmosphere in the RO RO vessels is monitored.

Additional Information

Ventilation system for ro ro cargo spaces on board ship generally operate according to the principle of dilution ventilation, where by the supply air flow to the area is sufficient for the exhaust gases to mix thoroughly with the air and be removed.

There are two main types of dilution ventilation: exhaust air ventilation and supply air ventilation.

In exhaust air ventilation, fans remove air from a ro-ro cargo space and this is then replaced by outdoor air entering through open ramps, doors and other openings.

Exhaust air ventilation is employed when sub-atmospheric pressure is required in the ro-ro cargo space. The sub-atmospheric pressure prevents the pollution from spreading to adjacent areas. Supply air ventilation works in the opposite way. Fans deliver outdoor air into the ro-ro cargo space and the air is then exhausted through ramps and other openings.

Supply air ventilation usually creates slight pressurisation of the ro-ro cargo space. If supply air ventilation is used exclusively, pollutants may mix with the supply air, be pushed up the internal ramps and contaminate other decks. However, if sufficient mixing with supply air does not occur,
contaminants may remain on the deck in question.