Fire suppression can be defined as quickly lowering the heat release rate of a fire and preventing its regrowth using sufficient application of water through flames to the seat of the fire.

Key Differences in Performance

• Fire Control:
  • Limits the maximum heat release rate.
  • Controls room temperature and stops secondary ignition.
  • Allows the fire to burn under a restricted, steady state.
• Fire Suppression:
  • Drastically reduces the heat release rate quickly.
  • Overpowers the combustion reactions.
  • Leads directly to full extinguishment of the fire
  Part (b)

  Traditional glass bulb sprinklers do not operate instantly even when the surrounding temperatures reach the operating temperature of the bulb. There is a time delay whilst it heats up to its operating temperature. Because of this lag, the temperature surrounding the sprinkler head may be several hundred degrees higher than the operating temperature of the bulb.

  New heat-sensing elements with fusible elements are a modern alternative. These respond faster with less thermal delay. Deck-head temperature reaching 100C compared with 600C for traditional sprinkler heads.

  Part (c)

  Safety Features Incorporated into the System:

  • Non-Return Valve: This prevents seawater from mixing with the pressure tank, ensuring the integrity of the firefighting system.
  • Pressure Switch: A pressure switch is incorporated to automatically start the seawater pump when the pressure in the system drops. Additionally, pressure switches are fitted at each sprinkler station to detect line pressure variations.
  • Pump Testing Valve: This valve allows testing the automatic activation of the seawater pump when the system detects a drop in pressure.
  • Relief Valve: This is installed on the pressure tank to release excess air pressure.
  • Low Water Level Float Switch: This device triggers an alarm when the water level in the pressure tank falls below the required threshold.
  • Testing Valve: These valves are included to facilitate the testing of various sprinkler stations, ensuring all components of the system function correctly.
  Part (d)

  The volume of the pressure tank is governed by the following parameters, as specified in the SOLAS regulations:

  • The pump and piping system must maintain sufficient pressure at the highest-level sprinkler head to ensure adequate coverage of a minimum area of 280 m² with continuous water output.
  • The system must provide an average application rate of water not less than 5 litres per square meter per minute across the nominal area covered by the sprinkler.
  • The pressure tank must have a volume at least twice that of the water charge required to meet the above application rate, ensuring adequate water supply during emergencies.