Class 2 (2nd Engineer) MEKG 📅 Sep 2022

Exam Question

With reference to Automatic sprinkler systems for firefighting purposes:

(a) Explain, with the aid of a Heat Release versus Time diagram, the difference between fire control and fire suppression

(b) State the limitations of using glass bulbs to activate sprinkler heads and suggest, with reasons, an alternative mechanism.

(d) The parameters governing the volume of the pressure tank

Reference Answer

(a) Fire control can be defined as limiting the size of the fire by distributing the water so as to decrease the heat release rate and pre-wet adjacent combustibles whilst controlling deck-head gas temperatures to avoid structural damage. 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.
(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.
(c) Safety Features Incorporated into the System:

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