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Bulkheads are an essential structural component of any ship, helping separate the vessel into watertight and fire-resistant compartments. In this article, we delve into the detail of different types of bulkheads and their qualifications.
To this end, we will explore all the different purposes of bulkheads, their placement in the ship, and their construction types. We also run over the three main classes of fire-resistance classification as per SOLAS.
After reading this article, yacht engineers should have a better understanding of the purpose of different bulkheads and some of the details that can help differentiate them. Let’s begin.
Purposes of bulkheads on a ship
Bulkheads are inner walls within the hull of a ship, used to separate it into smaller compartments. These partitions are believed to have appeared in the 12th century in Chinese junks and became widely used in the western navy in the early 19th century.
This compartmentalization of vessels has multiple purposes:
- Adds structural integrity to the hull - dividing a ship into smaller parts contributes to strengthening its hull. Bulkheads also support the deck, making it sturdier and more resistant to damage.
- Contain flooding in the event of damage - bulkheads add the possibility to seal damaged compartments and isolate them from the rest of the ship. This way, the captain can keep the ship afloat with the rest of the compartments remaining entirely usable (cargo, habitat, engine room) while it’s being repaired.
- Subdivision of the hull for storage and habitability purposes - dividing the hull into different sections allows seafarers to carry different types of cargo on the same vessel. This separation can have different purposes depending on the type of vessel. For instance, engineers use bulkheads to separate passengers’ from crewmembers’ cabins on yachts and commercial vessels.
- Create fire-resistant compartments - certain types of bulkheads can help contain fires on board. Same as with floods in watertight compartments, we can isolate fires from the rest of the ship by sealing bulkheads. Additionally, the crew can easily focus their efforts to extinguish the blaze on that particular part of the ship.
We categorize bulkheads following three major characteristics: their purpose, position, or construction. Below we look in detail at each of these categories and their sub-categories, to give you a more complete view of all the different types of ship bulkheads.
Types of bulkhead on the ship according to position
The first type of categorization of bulkheads is based upon their position in the vessel. There are two main types of ship bulkheads per position:
Transverse bulkheads
Transverse bulkheads divide the ship from side to side and are habitually used to create watertight compartments on the vessel. Additionally, they stiffen the structure of the hull, preventing deformation and racking stresses.
The video below explains how transverse bulkheads help with preventing structural damage to the ship.
Longitudinal bulkheads
Longitudinal bulkheads extend fore and aft and divide the vessel along its length. Engineers use them inside traverse bulkheads to increase the number of compartments even further. As a result, the ship conserves even more buoyancy when certain compartments are flooded and isolated.
Additionally, they are one of the main construction elements that strengthen the longitudinal integrity of the ship. Consequently, they are essential in larger vessels such as tankers and commercial vessels.
Types of bulkhead on the ship according to purpose
The second method of categorizing bulkheads is by purpose. Below we take a look at some major types of ship bulkheads regarding their usage.
Watertight Bulkheads
As their name suggests, watertight bulkheads have one main purpose - to divide the ship into smaller, watertight compartments. Depending on the size of the ship, they can be either:
- Constructed from a single plate for smaller ships.
- Reinforced to increase the stiffness of the bulkhead for larger ships. This way, the bulkhead can support a maximum amount of hydrostatic pressure once the compartment is flooded.
Once installed, shipbuilder engineers test watertight bulkheads with pressure hoses that should provide sufficient insight on possible leaks. Another, less invasive method to test leakages is by air-pressurizing the bulkhead chamber and inspecting for drops in pressure.
Finally, worth noting is that watertight bulkheads are usually equipped with watertight doors, that allow crew members to freely navigate the inside of the vessel.
To maintain the maximum integrity of the bulkhead, the dimension of the door is limited to a strict minimum. Furthermore, the opening is strengthened with additional plates of metal (doubler plate) that ensure that sturdiness is conserved around the watertight doors.
Non-watertight Bulkheads
Shipwrights install non-watertight bulkheads for any other type of use where there’s no need to isolate the compartment in case of a flood. They erect them to divide existing sections into smaller rooms to create cabins, storage compartments, engine casings, tool storage, etc.
Still, these bulkheads contribute to the stiffness of the yacht, making it resistant to deformation forces from navigation.
Collision bulkhead
Collision bulkheads are a type of watertight bulkhead situated in the front part of the ship. This part of the ship is particularly strong because as its name suggests, it limits the damage from full-on collisions with other vessels or segments of land. The anchor is usually situated in this part of the ship.
To determine the exact position of the collision bulkhead, engineers need to fulfil the following requirements:
- The bulkhead shouldn’t be too much in front and be able to get damaged upon frontal impact.
- The bulkhead shouldn’t be too far aft to allow the ship to trim by the stern considerably when the section is flooded. In addition to obvious safety concerns, this allows the captain to conserve fuel while heading back to shore when the ship is damaged.
- It should provide maximum cargo space.
- More precisely, the collision bulkhead should be 5 to 8% from the front of the ship.
If you are interested in learning more about additional regulations about the collision bulkhead, check out the video below.
Insulation bulkhead
Finally, the last type of ship bulkhead by purpose is the insulation bulkhead. Fire is a major concern on ships due to the high amounts of flammable materials (fuel, oil) that are carried at all times.
Engineers erect these types of bulkheads to isolate fire-hazard compartments from the rest of the ship. Consequently, bulkheads surrounding fuel compartments and engine rooms should be fire-resistant following SOLAS fire protection requirements.
Types of bulkhead on the ship according to construction
The final categorization of bulkheads is based on their construction. There are two main types of ship bulkheads according to this characteristic:
Plain bulkheads
You can easily distinguish plain bulkheads because they are constructed from a straight piece of metal. On smaller ships like yachts, plain bulkheads don’t need any reinforcements.
On larger vessels, however, engineers need to harden the plain bulkheads to provide maximum resistance. To achieve this, they weld or bolt down stiffeners to the bulkhead plates.
Corrugated bulkheads
Corrugated bulkheads are a type of bulkhead constructed from corrugated metal plates. Corrugation in engineering is used to naturally provide more rigidity to different types of materials, including cardboard and metal.
Thanks to this property, engineers do not need to reinforce corrugated bulkheads with stiffeners. As such, these bulkheads are lighter and sturdier than their plain counterparts.
Fire-resistance classifications of types of bulkheads as per SOLAS
Finally, there’s one last classification for bulkheads, which covers their insulation properties.
Class-A divisions
Class-A divisions include all watertight bulkheads. To be considered in this class, they need to fulfil the following criteria:
- Be made of metal and stiffened accordingly.
- They can prevent the passage of smoke and flame for the first 60 minutes following the fire.
- They are insulated with materials that prevent heat from spreading to the unexposed side for a determined amount of time. The temperature must not reach 140°C on average above the original temperature.
- Joints should never reach more than 180°C on average than the original temperature.
- The timeframe during which they can provide this insulation allows us to classify them further into the following sub-categories:
- Class A-60 - 60 minutes insulation.
- Class A-30 - 30 minutes insulation.
- Class A-15 - 15 minutes insulation.
Class-B divisions
Class-B panels cover the following characteristics:
- They are constructed from non-combustible materials, and all materials used for their erection are equally non-combustible.
- They can prevent the passage of flame for the first 30 minutes following the fire.
- They are insulated to protect heat of over 140°C propagating on the unexposed side.
- Joints should never reach more than 225°C on average than the original temperature.
Class-C divisions
Finally, Class C panels are constructed from fireproof materials. However, they do not need to meet additional requirements, such as insulation or preventing the passage of smoke or flame.
Wrapping up
In this article, we talked about the different types of ship bulkheads, how to recognize them, and their purpose on the yacht. To summarize we separated them into three major categories, each with its sub-categories.
- By position
- Transverse
- Longitudinal
- By purpose
- Watertight
- Non-watertight
- Collision
- Insulation
- By construction
- Plain
- Corrugated
Additionally, we detailed the different classes of bulkheads (A, B, and C) following their fire resistance and insulation capabilities.
All in all, bulkheads are essential construction components for vessels of any size. They increase the sturdiness of the ship and protect it from fire and flood damage.
