New York Low Pressure Boiler COF Practice

What is the minimum dial arc on a 2-1/4" gauge?

1. 180 degrees

2. 240 degrees

3. 270 degrees

4. 300 degrees

The correct answer is: 270 degrees

The minimum dial arc on a 2-1/4" gauge is 270 degrees, which is significant for ensuring accurate readings and proper calibration of the gauge. A dial arc of this size allows for a more precise measurement of pressure across the full scale of the gauge. In smaller diameter gauges, a minimum arc of 270 degrees is established as a standard to reduce the potential for parallax errors when reading the gauge. This helps operators to clearly interpret the pressure readings without confusion or misjudgment. A wider arc also provides a larger visual space for the pointer, making it easier to see the exact pressure at a glance. If the gauge had a narrower arc, such as 180 or 240 degrees, it would not provide the same level of accuracy or ease in reading, which is why these options are less appropriate. A 300-degree dial arc, while offering even more area for visibility, exceeds the minimum requirement and is not the correct answer to the question about the minimum.