Which of the following is the true psi reading when a gauge shows 175 psi and is situated 45 feet below the boiler connection?

To determine the true psi reading when a gauge shows 175 psi located 45 feet below the boiler connection, it is essential to account for the hydrostatic pressure exerted by the height of the water column above the gauge. The pressure due to the height of a water column can be calculated using the formula:

Pressure (psi) = Height (feet) × 0.433 psi/foot.

In this case, the height is 45 feet:

Pressure due to the water column = 45 feet × 0.433 psi/foot = 19.485 psi.

This value represents the additional pressure at the gauge due to the static head of water above it. Since the gauge reading already includes the pressure from the boiler (175 psi), to find the true pressure at the boiler connection, subtract the pressure due to the water column:

True pressure = Gauge pressure - Pressure due to water column

True pressure = 175 psi - 19.485 psi = 155.515 psi.

Rounding this result gives approximately 155.5 psi, which aligns with the correct answer. Understanding how to calculate the influence of hydrostatic pressure in this context is crucial for interpreting gauge readings accurately in systems where pressure measurements are affected by elevation differences.