Differences between operating pressure and design pressure, operating flow rate and design flow rate, operating temperature and design temperature
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When selecting instruments, what are the numerical relationships between the operating pressure and the design pressure, the operating flow rate and the design flow rate, as well as the operating temperature and the design temperature? Should the operating values or the design values be used as the basis for determining the range?
The operating values represent ideal conditions, while the design values correspond to extreme conditions. The selection should be based on the operating values; it’s best if the range matches the design values. If there is a significant difference, it’s necessary to discuss this with the process engineers and make appropriate adjustments
The operating values can be understood as the values commonly used in actual operation; select the scale range according to the design values
The operating value refers to the flow rate and pressure that will be reached in normal use, while the set value is the level that the instrument is theoretically capable of achieving. Theoretically, the set value is definitely greater than the operating value.
The operating value generally refers to the reading of the process system under normal operating conditions, while the design value is the extreme limit of the process system – a value that can cause sudden changes in the equipment or operating conditions, but which remains controllable. When selecting measurement and control equipment, the choice should be based on the design requirements. The normal operating value is a fraction or a few tens of percent of the design value. The normal choice is to select between 80% and 85%.
It’s simple: a tank is designed to withstand a pressure of 3.0 MPa, while the actual operating pressure is 1.0 MPa. These are the design pressure and operating pressure. The temperature is the same as well.