The highest end of the scale for mechanical gauges used to measure test pressures must not exceed how many times the test pressure?

Mechanical gauges used to measure test pressures are designed to provide accurate readings within a specified range, ensuring the measurement is safe and reliable. The industry standard for the highest end of the scale is typically set at not exceeding five times the test pressure. This guideline helps prevent situations where a gauge could be subjected to pressures beyond its calibrated limit, potentially leading to gauge failure or inaccurate readings.

Exceeding this ratio can compromise the gauge's integrity and safety, as gauges are often designed to operate optimally within a defined range. Therefore, measuring pressures at excessive multiples of the test pressure increases the risk of damage and can lead to misleading information about the system's status. In contrast, using a gauge scale that only goes up to three or four times the test pressure might not adequately reflect higher pressure conditions without risking potential inaccuracies or failures. Thus, setting the maximum scale limit at five times ensures both the safety and performance integrity of the gauges during operations.