Hotel Service Unit 15 Fire Q5 – Answer

  1. (a) Explain the need for fitting, location, and operation of an engine room fire main isolation valve.
    (4)
    (b) State the type of valve used in part (a).
    (1)
    (c) Describe, with the aid of a sketch, the construction of a sprinkler head.
    (5)

(a) Engine Room Fire Main Isolation Valve – Need, Location, Operation (4 marks)

  • Need for fitting:
    • To allow the engine room section of the fire main to be isolated in case of damage or fire in that area.
    • Ensures that the remainder of the fire main system (e.g. on deck or accommodation) remains operational.
  • Location:
    • Fitted on the fire main at the bulkhead where the fire main enters the machinery space, usually outside the engine room in a safe, accessible position.
  • Operation:
    • Valve can be quickly closed manually from outside the engine room, isolating the engine room branch.
    • Often designed for remote/manual operation so crew need not enter the space during a fire.

(b) Type of Valve Used (1 mark)

  • Normally a screw-down non-return valve (SDNR valve) or a gate valve is used, providing reliable shut-off.

(c) Sprinkler Head – Construction (with sketch) (5 marks)

Construction features:

  1. Body: Metal casting, connected to the water supply pipe.
  2. Deflector plate: Mounted below the nozzle, designed to spread water in a fine spray over a wide area.
  3. Glass bulb (or fusible link): Heat-sensitive element filled with liquid (glass bulb) or solder joint (fusible link).
  4. Sealing cap/valve: Held in place by the bulb or fusible link to prevent water discharge under normal conditions.
  5. Frame: Holds all components together.

Operation:

  • When a fire raises the ambient temperature to the rated activation temperature (e.g. 68 °C), the glass bulb bursts or fusible link melts.
  • The sealing cap is released, allowing water to discharge.
  • Water strikes the deflector plate and is distributed as a spray over the fire area.

Sketch (exam-style):

  • Draw sprinkler head with: inlet pipe → frame → glass bulb/fusible link → sealing cap → deflector plate at bottom.
  • Label all components clearly.