Boiler Mountings — Typical Number of Water Level Indicators (Gauges) In standard practice for boilers, how many independent water level indicators (gauge glasses) are generally provided for safety and monitoring?

Introduction / Context:
Maintaining correct water level is critical to boiler safety. Too low a level risks overheating of heating surfaces; too high a level risks water carryover to steam lines and turbines. Therefore, codes and good engineering practice require redundancy in water level indication.

Given Data / Assumptions:

• Conventional shell or water-tube boilers in industrial service.
• At least one direct-reading gauge glass plus redundancy.
• Auxiliary devices like remote level transmitters may also be installed but do not replace direct indicators in many jurisdictions.

Concept / Approach:
Two independent water level indicators are generally provided so that one can corroborate the other. This redundancy helps detect instrument failure, blockage, or misreading, and supports safer operation and compliance with regulatory inspections.

Step-by-Step Solution:
Identify the safety requirement: clear, reliable indication of drum or shell level.Apply redundancy principle: two gauge glasses are customary and often mandated.Therefore, the typical number is two.

Verification / Alternative check:
Many boiler standards and inspection authorities specify two direct level indicators on high-pressure boilers, with additional remote indicators or alarms as supplements.

Why Other Options Are Wrong:

• One: lacks redundancy; not preferred for safety.
• Three or four: unusual and unnecessary in most designs, though multiple indicators may be used in special cases.

Common Pitfalls:
Relying solely on remote transmitters; direct visual indication is critical during commissioning and abnormal events.

Final Answer:
two