What is the minimum scale graduation required for a pressure gauge?

The minimum scale graduation required for a pressure gauge is set to ensure that the gauge can accurately measure pressures without risking damage or providing inaccurate readings. Choosing a scale graduation of one and one half times the maximum test pressure provides a buffer that allows for safe operation above the maximum expected pressure. This buffer helps account for potential pressure fluctuations or surges that can occur during normal operation.

Setting the gauge at this graduation level ensures that the readings remain reliable and that the gauge does not operate at full capacity, which could lead to quicker wear or failure. Additionally, this standard helps maintain safety by preventing pressure readings from reaching critical limits that could pose risks to equipment and personnel.

Other options suggest higher multiples of the maximum test pressure, which may not be necessary for accurate performance and could lead to increased costs or over-engineering. Thus, selecting one and one half times the maximum test pressure strikes an ideal balance between safety, accuracy, and cost-effectiveness in pressure gauge design and application.