Question

Choose the CORRECT match of fire detection systems in GROUP X with their working mechanisms in GROUP Y.

GROUP X
(P) Fusible plug loops
(Q) Thermal and smoke detection system
(R) Gas detection system

GROUP Y
(I) Detects rise in temperature caused by fire and visible/invisible particles of combustion
(II) Functions based on drop in pressure that activates fire shutdown
(III) Detects flammables

• A. P-I; Q-II; R-III
• B. P-II; Q-I; R-III
• C. P-III; Q-I; R-II
• D. P-II; Q-III; R-I

Hint:

Ask what physically triggers each device: a melted plug causes a pressure loss, heat and smoke are picked up electronically, and gas sensors respond to flammable vapour concentration.

Answer 1

The Correct Option is B

Step 1: Understand how a fusible plug loop works:
A fusible plug loop is a pneumatic safety loop that is routed through the hazardous areas of an offshore platform or process facility. The loop is kept pressurised with air or nitrogen, and plugs made from a low melting point alloy are fitted at intervals along it. When a fire occurs near the loop, the heat melts the fusible alloy plug, the loop ruptures at that point, and the pressure inside the loop drops sharply. A pressure switch senses this drop and uses it directly to trigger the emergency shutdown and fire protection sequence. So a fusible plug loop is the system that works based on a drop in pressure that activates fire shutdown, which is GROUP Y statement (II).
Step 2: Understand how a thermal and smoke detection system works:
A combined thermal and smoke detector is an electronic device with two sensing elements. The thermal element responds to a fast rise in the surrounding temperature that a growing fire produces, while the smoke element, whether optical or ionisation type, responds to the visible and invisible particles of combustion released as material burns. Together these elements allow the detector to pick up both the heat signature and the smoke signature of a fire, matching GROUP Y statement (I), which describes detection of a temperature rise caused by fire along with visible and invisible combustion particles.
Step 3: Understand how a gas detection system works:
A gas detection system is installed to guard against the build-up of flammable hydrocarbon vapours, which is a serious hazard on a production platform even before an open fire develops. These detectors continuously monitor the surrounding atmosphere and respond once flammable gas concentration crosses a set fraction of the lower explosive limit. This matches GROUP Y statement (III), detection of flammables.
Step 4: Combine the three matches:
Putting the matches together gives P (Fusible plug loops) - II, Q (Thermal and smoke detection system) - I, and R (Gas detection system) - III, which is option (B).
Final Answer:
\[ \boxed{P-II;\ Q-I;\ R-III\ \text{(Option B)}} \]