According to NFPA, how often should the mercury gauges on tanks be tested?

According to NFPA, how often should the mercury gauges on tanks be tested?

• A. Every 7 years
• B. Every 5 years
• C. Every 3 years
• D. Every 10 years

Answer: (B)

Gauges that indicate tank contents must be kept accurate to prevent overfill, underfill, or unsafe conditions. Mercury gauges are mechanical devices that can drift with age, vibration, temperature changes, or seal and glass wear, so they need a planned check to confirm they still read correctly. NFPA specifies a fixed periodic testing schedule for this type of gauge to catch drift before it affects operation, without requiring constant maintenance. The established interval is a five-year cadence, which provides a practical balance between reliable readings and reasonable maintenance effort. During the test, the gauge is checked against a calibrated reference or known standard, and any deviation beyond the acceptable tolerance leads to recalibration, repair, or replacement. Other intervals would either miss drift too long or add unnecessary work, which is why the five-year schedule aligns with the standard.

Gauges that indicate tank contents must be kept accurate to prevent overfill, underfill, or unsafe conditions. Mercury gauges are mechanical devices that can drift with age, vibration, temperature changes, or seal and glass wear, so they need a planned check to confirm they still read correctly. NFPA specifies a fixed periodic testing schedule for this type of gauge to catch drift before it affects operation, without requiring constant maintenance. The established interval is a five-year cadence, which provides a practical balance between reliable readings and reasonable maintenance effort. During the test, the gauge is checked against a calibrated reference or known standard, and any deviation beyond the acceptable tolerance leads to recalibration, repair, or replacement. Other intervals would either miss drift too long or add unnecessary work, which is why the five-year schedule aligns with the standard.