Chemical process instrument tag number
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I’m new to instrumentation work and have been getting familiar with the instrument tag numbers in the company recently; I have a few questions if anyone can help. 1. What is the difference between a PIT and a PDIT? Both are pressure transmitters. The difference lies in the fact that a PIT transmitter has its low-pressure side connected to atmospheric pressure, so the pressure measured is gauge pressure, while a PDIT transmitter has pressure measurement points on both the high-pressure and low-pressure sides; the actual value obtained is the difference between these two pressures? 2. The designations for pressure control valves are TV, FV, and LV; their literal meanings are temperature valve, flow valve, and level valve. What do these mean? There are also TCV, FCV, LCV, HCV, PCV, PaV. . . . . . 3. The automatic valve positions are HV and EBV, etc. . . None of these are very clear.
Transmitters, pressure regulating valves, and automatic valves are all from Yamaki
1. pit and pdit: P stands for pressure, d stands for pressure difference, i stands for indication, and t stands for transmission. 2. TV: Adjusts in response to temperature changes; FV: Adjusts in response to flow rate changes; LV: Adjusts in response to liquid level changes. TCV, FCV, LCV, HCV, PCV, PaV are likely the names of the control circuits. 3. HV: This probably refers to a manual valve; EBV: (Emergency Block Valve) emergency shut-off valve
Learn about HG/T 20505-2014 \"Functional Indicators and Graphic Symbols for Process Measurement and Control Instruments\"
By referring to the standard \"Functional Indicators and Graphic Symbols for Process Measurement and Control Instruments\", looking at the parameter table of the instrument equipment, and then examining the circuit diagram corresponding to its tag number, everything becomes clear at a glance
HV – here it refers to an automatic valve. Thank you!
The first character indicates the type of measurement signal, while the subsequent characters denote the function of the signal, etc. In practical use, strict requirements are not usually imposed. I represents T-transmission, Q represents accumulation, C represents control, and S represents interlock. Common types include PI, PIT, PT; these are often used interchangeably. Similar symbols such as FI, FT, FIT, FIQ, and HV denote manual valves; if automation is implemented, the purpose of these symbols changes accordingly. Once the tag number is set, it is generally not changed later, but functions such as control C and interlock S may be added.