For weather decks on a ship, drainage is very important. Any form of water accumulation can cause various problems, from sinking to interference with other entities, structures, equipment or machinery.
The main deck or weather deck is provided with gutters or drains to drain water. However, the requirement is higher when the ship is arranged with large bulwarks in the weather passage or main deck.
What is Bulwark mean literary?
Weather barriers installed on the roof are intended to protect personnel and are not intended to be a major structural feature. They are therefore of light timber construction and their connection to adjacent structures is very important if we are to avoid excessive stress on the bulwarks.
Scuppers are dug in the bulwarks to form wells in the roof so that water can drain quickly. The space required for scuppers should comply with the provisions of the Load Line Rules 1968. On both free and weather decks, bulkheads must be at least 1 metre high, but lower heights may be permitted if this would affect the operation of the vessel.
What should you know about Bulwark?
A bulwark is a wall-like projection around the weather deck that is flush with the side guards and therefore extends far above the height of the main deck. The purpose of the bulwark is to protect the crew, personnel, passengers and deck cargo (if any) from falling over the sides. In addition, bulwarks can also be used to protect the weather deck from the impact of waves and the intrusion of spray in rough seas.
The height of these bulkheads is subject to certain rules and guidelines, depending on the type of ship, service conditions and other factors. For barriers above a certain height, a well similar to a wall is created relative to the surface. Since water does not have a chance to drain out of the sides of the deck, it increases the risk of waterlogging.
Also, due to strength and design requirements, the number of drains, drains, etc. is limited. Moreover, these openings are usually small (due to some size restrictions related to surface strength).
In case of surface flooding, these openings are not completely effective in draining water. Moreover, horizontal openings on deck are more prone to blockage, inefficiency and obstruction in case of ice etc.
Therefore, some other means of drainage is required in addition to other drainage arrangements.
The 1966 Load Line Rules introduced relief ports to alleviate this problem. These are well-defined slots on the castle plate itself with specific numbers and spacing. They act as openings close to the deck level so that any form of accumulation of water on board can be constantly drained.
The design of the discharge and disposal outlets must be for the sole purpose of quickly removing water from the surface in all outdoor conditions. Since there is no hard and fast requirement, the relief ports can be of any shape, although in practical applications they are all circular.
However, according to the standards, they must have rounded corners to improve efficiency and reduce stress concentrations due to sharp edges.
The number, arrangement and location of discharge ports depend on the type of vessel, size, design, nature of decks and other means of drainage and of course the type of bulwarks.
Large vessels are expected to have more release ports than smaller ones. The composition of the bulwarks also plays an important role. When the entire exposed surface is adjacent to the bulwarks, the number of barriers is more than when the surface is only partially covered by barriers.
In addition, the height of the bulwarks also plays an important role. The higher the barriers, the more discharge ports there are and the greater the chances of waterlogging. The number of barriers alone is not a clear criterion as each release port also has size limits.
The number, size and arrangement are optimized as per the requirements. The total or aggregate area of all surface release ports is an important factor for the designer. Let us further understand the important aspects of edit ports.
Some important aspects of Feering outlets
The technical factors of design, construction, and arrangement of edit outlets rely on certain rules and regulations.
As for the number of free ports, as mentioned above, it depends on the design of the vessel and the arrangement of bulwarks.
- The number of outlets should be maximized to ensure complete drainage of water from the surface.
- The release ports should also be selected based on criteria such as slope, curvature, etc. That is, the arrangement of discharge ports should be concentrated in areas where there is a greater possibility of water accumulation.
- The lower end or edge of the discharge port opening should be as close to the deck edge or deck line as possible. For practical purposes, at least two-thirds of the outlet openings should be located vertically in the lower half of the height of the bulwark.
- The spacing between outlets (uniform or random) must be sufficient and meet 100% drainage under all conditions.
- After making the necessary arrangements and arrangements, the area of the opening is determined based on the total area. According to the Guidelines of the Load Line Convention, for ships less than 20 meters in length, the net area of the discharge port should be 0.7 + 0.035 × l, where l is the total linear span of the entire bulkhead in the direction of the deck. For ships with a length of more than 20 meters, the calculation formula is: 0.07 x L.
- The vertical height of the bulwark is also important. For each 0.1 meter increase in the height of the bulkhead above the deck level, the area of the discharge port calculated from above should be increased by 0.004 square meters. For example, if the height of the bulwark is 1.5 meters above the main deck, the area (A) obtained from the above relationship will be expressed as A + 0.004 × 3A, because there is an additional height of 0.3 meters relative to 1.2 meters.
- Similarly, when the length and height of the bulwark are less than 0.9 meters, the reduction in area is also 0.004 square meters per unit, which is a reduction of 0.1 meters relative to the reference height of 0.9 meters.
- In the absence of cuts, the area calculated above is increased by 5% over the area obtained above.
- Similarly, for some trunk and superstructure designs, the requirements are different.
- Generally speaking, manholes with a diameter greater than 230 meters must be provided with intermediate fences or safety rails.
- Some forts also have shutters that can be controlled as required. Although bulkheads are not primary or secondary structural components that affect the strength of the ship, in many designs they are often retained as a simple extension of the side plates. Therefore, for a large number of free ports or large ports, additional reinforcement is sometimes provided around the openings because they may reduce the structural integrity of the forts or even local areas of the sheltered path.
- Although it is not common to require clear ports, clear ports are also related to stability and buoyancy requirements. We all know about reserve buoyancy. From a practical point of view, if the maximum amount of water retained by the bulkheads and superstructures/tanks in the open deck path (taking into account the total water resistance) is greater than the buoyancy reserve required by the design, the number of water openings should be increased accordingly.
- Some ships, such as fishing vessels, have special provisions for free ports.
