5th Class Power Engineering Practice Exam

The minimum graduation requirement for a pressure gauge installed on the high side of a refrigerating system is established to ensure accurate and reliable readings that can safely reflect the operating conditions of the system. A gauge that is graduated to 1.2 times the design working pressure ensures that it can accurately measure pressures above the normal operating range without risk of damage or failure.

Graduating the gauge at this level allows for some margin above the design pressure, accommodating potential fluctuations or surges in pressure that can occur during operation. This safety margin is critical in maintaining system reliability and safety, as pressures can occasionally exceed the standard operating conditions. By using a gauge that meets this graduation requirement, operators can better monitor the system's performance and detect any issues that may arise, thereby enhancing overall safety.

Graduating closer to the design pressure would limit the effectiveness of the gauge in critical situations, potentially leading to inadequate pressure monitoring and increased risk of accidents or system failures. Therefore, setting the graduation at 1.2 times the design working pressure is a standard practice that balances accuracy, reliability, and safety in refrigeration systems.