Design of bulkhead for marine vessels.
Introduction
The walls of the ship serve a variety of functions. The main reason for the formation of bulkheads is to create compartments which can be used for storing cargos or creating accommodation spaces. It’s believed that Chinese were the first people who started using bulkheads in their ships. Prior to that the whole hull of the ship used to be an open space. Not only that, bulkheads provide structural stability and rigidity to the ships. They also minimizes the violent sheer forces acting on the ship, that are generated due to waves. Moreover bulkheads are also useful from safety point of view. They prevent water from entering different parts of the ship in case there is flooding.Let’s take a look at the basic bulkhead designs.
Bulkhead Designs
Contruction of bulkheads mainly depend on the utility and type of the ship. Though there are different types of bulkheads that are designed to carry out different function, they are classified mainly into following types:
- Watertight
- Non-watertight
- Tank
Watertight Bulkheads
These type of bulkheads are used nowadays in all most all types of ships. They provide maximum safety in times of flooding or damage of hull. They divide the ship into watertight compartments which prevents seeping of water to other parts of the ship incase the hull is broken. The number of compartments that a particular ship has depends on the type and requirement of the vessel.
They also facilitate storage of different types of cargo at the same time. Incase there is a fire, they prevent the source of fire or the flame to pass over to other compartment. They increase the overall strength of the ship by increasing the transverse strength.The number of bulkheads depends on the length of the ship and arrangement of machinery. It is imperative for all the ships to have a collison bulkhead
The stern tube should be enclosed in a separate water tight compartment. This compartment can be formed by aftpeak bulkhead and stern frame.All these bulkheads can withstand full head pressure. This is generally done by keeping the bottom thickness of the bulkheads greater than that of the top
Water Tight Doors
If the water tight bulkheads are made to use them as accommodation or machinery spaces, they are provided with water tight doors. The main types of watertight doors are as follows:
Vertically Mounted Watertight doors :
These types of doors are of mild or cast steel and can be arranged to be opened vertically or horizontally. They shouldn’t rely on gravity for opening and should be located 2.2 meters above the deck.
Hinged Watertight Doors:
These are generally heavy doors that when closed, seals on a packing material that is welded to the door frame with the help of a metal strip. The door is firmly held in the door frame with the help of a dogging arrangement as shown in the figure.
Automatic watertight operating system:
This system is used in case there is a fire or flooding. In such situations, a signal is sent from bridge or engine room to an oil diverter valve. The door is operated with the help of pressurised hydraulic oil which moves the ram that controls the opening and closing of the door. The system can also be operated with the help of a local manual hand pump.
Non watertight and Tank bulkheads
Construction of Non Watertight bulkheads is now Obsolete. They are made just to increase the strength and rigidity of ships. Nowadays as all the ships fully use the hull spaces, these types of bulkheads are not in use anymore.
Tanks bulkheads are normal watertight bulkheads that are used to create watertight tanks.All the ships use these bulkheads to make provision for different tanks on ship.
References
Image credits
https://www.marineengineering.org.uk/
