Boiler mountings — device on the steam chest to prevent overpressure damage Name the device fitted to the steam chest whose purpose is to prevent explosions by automatically releasing steam when internal pressure exceeds a safe limit.

Introduction / Context:
Boiler mountings are essential for safe operation. Among them, one device is specifically tasked with limiting pressure to avoid catastrophic failure by venting steam when pressure becomes excessive.

Given Data / Assumptions:

• Steam chest connected to the boiler drum or shell.
• Standard spring-loaded or deadweight valve calibrated to a set pressure.
• Regular testing and sealing per regulations.

Concept / Approach:
A safety valve automatically opens when pressure exceeds the set value and recloses after pressure falls below a reseat point. It is distinct from indicating devices (pressure gauge, water level indicator) and from low-water protection (fusible plug) or maintenance fittings (blow-off cock).

Step-by-Step Solution:

Verification / Alternative check:
Boiler codes mandate safety valves as primary overpressure protection and specify relieving capacity sized to firing rate.

Why Other Options Are Wrong:

• Water level indicator: indicates level; does not relieve pressure.
• Pressure gauge: measures pressure; does not control it.
• Fusible plug: protects against low water by melting; not overpressure relief.
• Blow-off cock: drains sludge/water; not automatic relief.

Common Pitfalls:
Confusing the fusible plug’s low-water function with overpressure protection; neglecting periodic testing of safety valves.

Final Answer: