Question

Define briefly the construction details peculiar to each of the following types of closure that enables their primary function to be fully realized:

(a) Water tight doors,

(b) Fire proof doors,

(c) Gas tight doors,

(c) With reference to above doors, State why (a) can perform function of (b) as well as of (c), whereas function of (b) and (c) are restricted solely to their primary function.

Answer 1

Define briefly the construction details peculiar to each of the following types of closure that enables their primary function to be fully realized:

Part (a)

Water tight doors

Part (b)

Fire proof doors

Part (c)

Gas tight doors

Part (d)

With reference to the above doors, state why (a) can perform the function of (b) as well as of (c), whereas the function of (b) and (c) are restricted solely to their primary function.

Part (a)

Watertight doors: A watertight door is designed to prevent the passage of water through a watertight bulkhead, maintaining the watertight integrity of the ship's subdivision. Construction details: the door is made of steel, fitted in a steel frame, with a gasket/sealing arrangement (a rubber or neoprene gasket) compressed by dogs (quick-acting clamps) or a wheel-operated mechanism that forces the door against the frame to make a watertight seal. The door is fitted with a watertight seal around the perimeter, and the dogs/cleats are arranged so that the door can be closed quickly and securely. Watertight doors may be sliding (vertical) or hinged, and are operated manually or by power (with a remote control and an alarm). The door and its frame are tested for watertightness (hose test) and are designed to withstand the water pressure.

Part (b)

Fireproof (fire-resisting) doors: A fire door is designed to prevent the passage of fire and smoke, maintaining the fire-resisting integrity of the fire divisions (A-class or B-class bulkheads). Construction details: the door is made of steel (or a fire-resisting material) with a fire-resisting core/insulation, fitted in a steel frame, with intumescent seals or a fire-resisting gasket that expands when heated to seal the gaps. The door is self-closing (with a self-closing device) and is fitted with a latch. It is tested to the fire-resistance standard (e.g. A-60, A-30, B-15) and is designed to withstand the fire for the specified period, preventing the spread of fire and smoke. Fire doors are not necessarily watertight.

Part (c)

Gas-tight doors: A gas-tight door is designed to prevent the passage of gas (e.g. in a gas-tight space, or to prevent the passage of flammable/toxic gas). Construction details: the door is made of steel with a gas-tight seal (a gasket that seals the perimeter completely), fitted in a steel frame, with a clamping mechanism that compresses the gasket to make a gas-tight seal. The door is designed to prevent the passage of gas, and is tested for gas-tightness. Gas-tight doors are used in spaces where gas-tight integrity is required (e.g. in tankers, or to isolate a space containing gas).

Part (d)

Why a watertight door can perform the function of a fire door and a gas-tight door, whereas a fire door and a gas-tight door are restricted to their primary function:

A watertight door, being made of steel with a full perimeter seal (gasket) and a clamping mechanism, provides a complete, sealed closure that is also fire-resisting (steel is fire-resisting) and gas-tight (the full seal prevents the passage of gas). Therefore a watertight door can also act as a fire door (it is made of steel and provides a fire-resisting barrier) and as a gas-tight door (its seal prevents gas passage).

A fire door, however, is designed primarily to resist fire and smoke; it is not necessarily watertight (it may not have a watertight seal and may not withstand water pressure) and is not necessarily gas-tight (its fire-resisting gasket may not provide a complete gas seal). Similarly, a gas-tight door is designed to prevent gas passage but is not necessarily fire-resisting to the required standard or watertight. Hence the fire door and gas-tight door are restricted to their primary function, whereas the watertight door, by virtue of its steel construction and full seal, can perform all three functions.

✓ Verified Model Answer (Text Solution)

Water tight doors

Fire proof doors

Gas tight doors

With reference to the above doors, state why (a) can perform the function of (b) as well as of (c), whereas the function of (b) and (c) are restricted solely to their primary function.

Why a watertight door can perform the function of a fire door and a gas-tight door, whereas a fire door and a gas-tight door are restricted to their primary function: