Regarding instrument calibration

The calibration of instruments is primarily based on the inspection regulations for instruments (JJG) or calibration specifications (JJF); such documents do exist. For example, for transmitters, there is JJG882-2004 \"Inspection Regulations for Pressure Transmitters\" and JJF 1183-2007 \"Calibration Specifications for Temperature Transmitters\".........

Is it debugging before the project’s trial run? Perform loop testing, interlock testing, and alarm testing on all points. The on-site pressure gauges have calibration records (for internal inspection), and the on-site alarms come with certification certificates issued by the metrology department; instruments that are subject to mandatory inspection (such as those used in hazardous chemical storage tanks, reaction vessels, pressure vessels, and high-temperature and high-pressure processes) must have certification certificates from the metrology department. All kinds of operating procedures and management regulations need to be properly formulated. Additionally, it seems there are no national standards specifying how to calibrate instruments; it’s probably the five-point calibration method.

The Chemical Industry Press has a book titled \"Essentials for Instrument Operators\" (published in November 2014), whose Chapter 9 is dedicated to the individual calibration of instruments. The table of contents for this chapter is copied below for reference. 9. Instrument Calibration Skills 9.1 Calibration of Bourdon Tube Pressure Gauges 9.1.1 Calculation of Errors in Bourdon Tube Pressure Gauges 9.1.2 Methods for Calibrating Bourdon Tube Pressure Gauges 9.2 Calibration of Pressure and Differential Pressure Transmitters 9.2.1 Calculation of Allowable Errors in Pressure and Differential Pressure Transmitters 9.2.2 Calibration Methods for Analog Pressure and Differential Pressure Transmitters 9.2.3 Calibration Methods for Intelligent Pressure and Differential Pressure Transmitters 9.3 Calibration of Double-Flange Differential Pressure Level Transmitters 9.4 Calibration of Thermocouples 9.4.1 Allowable Deviations for Common Thermocouples 9.4.2 Calibration of Thermocouples 9.5 Calibration of Thermal Resistors 9.5.1 Allowable Errors for Common Thermal Resistors 9.5.2 Selection of Calibration Points and Measurement Methods 9.5.3 Calibration of Thermal Resistors 9.6 Calibration of Temperature Transmitters 9.6.1 Calibration Methods for Thermocouple Temperature Transmitters 9.6.2 Calibration Methods for Thermal Resistor Temperature Transmitters 9.7 Calibration of Flow Integrators 9.8 Calibration of Digital Displays 9.8.1 Error Representation and Calculation Formulas for Digital Displays 9.8.2 Calibration Methods for Digital Displays 9.9 Calibration of Recorders 9.10 Calibration of Regulators 9.10.1 Preliminary Knowledge for Regulator Calibration 9.10.2 Open-Loop Calibration of Regulators 9.10.3 Closed-Loop Calibration of Regulators 9.11 Commissioning of Electric Actuators 9.11.1 Commissioning of DK-Type Electric Actuators 9.11.2 Commissioning of RS-Type Electric Actuators 9.11.3 On-Site Online Commissioning 9.12 Methods for Calibrating Instruments Using Process Calibrators

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Bro, you’re really lucky! I just wrote out procedures for single-unit testing, and I’m sharing them here to help everyone improve their work: 5.1 Point Inspection – Purpose: This step is used to verify the circuits after new devices are connected to the control system but before power is applied. It involves checking the quality of cable installation and the correctness of the connection points. It’s essential that the point inspection is successful before powering on the instruments; otherwise, powering them on is not allowed； Tools required: wire, walkie-talkie, multimeter, wrench, screwdriver, etc ； Verification method: ① Confirm that the on-site wiring and controller wiring have been connected fully, and the system has not been powered on ； ② Refer to the I/O point table of the control design, and conduct continuity tests on each point one by one; that is, use short wires to connect each set of wires, and the control room should use a multimeter to check for continuity. It is important to perform at least two continuity tests for each set of wires in order to avoid test errors caused by interference from other factors. 5.2 Detection circuit test: Purpose: To check whether the circuit parameters are correct ； Check whether the circuit logic is correct ； Check whether the card module from the input terminals in the cabinet to the control room is damaged ； Tools required: hand controller, signal generator, short wire, walkie-talkie, wrench, screwdriver, etc ； Verification method: ① Check the status of the instruments on-site and confirm whether the point type is correct (AI, DI) ； ② Check the range of the instruments on site and verify that it matches the values shown on the computer in the control room (except for thermal resistors and thermocouples without transmitters; in such cases, the temperature range must be checked on the isolator) ； ③ For analog input points, a handheld operator or signal generator is used to input standard signals from the field instruments; the test points should include at least 0%, 25%, 50%, 75%, and 100% of the range, so as to check on the host computer whether the displayed values are accurate and precise ； ④ For digital input points, use a short wire to short-circuit the on-site status feedback line, and check on the host computer whether the status has changed, as well as whether this change is synchronized and consistent with the actual on-site condition. 5.3 Output Circuit Testing Specifications Purpose: To check whether the output status and the response of field actuators are correct ； Check whether the circuit logic is correct ； Check whether the circuit card module is damaged ； Check whether the actuator is damaged ； Tools required: walkie-talkie, multimeter, wrenches, screwdrivers, etc ； Verification method: ① Confirm that the on-site process conditions meet the testing requirements, and that the opening/closing of valves and the starting/stopping of pumps will not pose any risks to the safety of the process equipment or the personnel ； ② Check the on-site actuator to confirm the output point type (AO, DO) ； ③ For analog output points (such as analog signals from control valves, frequency converters, etc.), the output values provided by the host computer should include at least 0%, 25%, 50%, 75%, and 100% of the range, so that it can be checked on-site whether the action of the actuator is synchronized with that of the host computer ； ④ For digital output points (such as on/off signals for shut-off valves, solenoid valves, pump start/stop, etc.), the corresponding “on/off (1/0)” signal is sent from the host computer to determine whether the field actuators are operating and have reached their intended position ； For components that cannot be observed directly with the naked eye, such as solenoid valves, the coil voltage can be measured using a multimeter to determine whether a signal is being sent ； 5.4 Specifications for Testing the Control Logic of the Station Control System: Purpose: To verify whether the operation logic of the on-site actuators/pumps is correct ； Check whether the parameter configuration is reasonable ； Check whether the action response is timely and effective ； Tools required: handheld controller, signal generator, walkie-talkie, wrench, screwdriver, etc ； Verification method: ① Confirm that the on-site process conditions meet the testing requirements, and that the opening/closing of valves and the starting/stopping of pumps will not pose any risks to the safety of the process equipment or the personnel ； ② For the single-loop automatic control of control valves, first switch to \"automatic\" mode, and send a signal at the control point (sensor). Signals are sent based on whether the value is greater than/less than the set value; by observing the operation logic of the control valve, it can be determined that when the value is greater than the set value, the valve should open/close, and when it is less than the set value, the valve should close/open ； ③ For the regulation of control valve cascade loops, testing should first be carried out in the secondary loop in accordance with point ②, followed by testing in the primary loop; the valves must operate correctly in both cases ； ④ For the automatic control of the shut-off valve, first set it to \"automatic\" mode, and send a signal at the control point (sensor). Signals are sent based on whether the value is greater than or less than the set value, in order to determine whether the shut-off valve should close or open. Once the value returns to the normal range, it is checked whether the valve is open or closed ； ⑤ For pump operation, first set it to “remote/automatic”; send signals at the control point (sensing instrument), providing signals corresponding to values greater than/less than the set values, to check whether the pump starts/stops. Once the value is within the normal range, determine whether the valve stops/start ； ⑥ It should be noted that when setting values for the cut-off valves and pump operation control points, the values must be set accurately, with the error not exceeding that of the measuring instruments. 5.5 SIS System Interlock Testing Specifications Purpose: To verify whether the operation logic of field actuators/pumps is correct ； Check whether the parameter configuration is reasonable ； Check whether the action response is timely and effective ； Tools required: handheld controller, signal generator, walkie-talkie, wrench, screwdriver, etc ； Verification method: ① The operators shall confirm that the on-site process conditions meet the testing requirements, and that the opening/closing of valves and the starting/stopping of pumps will not pose any risk to the safety of the process equipment or the personnel ； ② Inform the on-site workers about the arrangements for the interlock testing, organize the personnel in the work area to work together in a coordinated manner; these personnel can be divided into groups such as those responsible for monitoring on-site equipment, those in the control room, those handling on-site instruments, the logistics team, and the emergency response team, so as to carry out all the preparatory work before the testing ； ③ Refer to the causal interlock diagram to analyze one by one the operating conditions, the relationships between these conditions, how many operating conditions are involved in the operation of a single valve, and the response levels ； ④ During testing, proceed in the order of three-level interlock → two-level interlock → one-level interlock. When multiple interlocks simultaneously trigger the operation of the same valve(s), other conditions should first be kept within their normal ranges (or those conditions can be ignored; this method should only be used when the previous approach is not feasible) to avoid inaccurate test results ； ⑤ When setting the interlock conditions via on-site instruments, the values must be accurate, with the error not exceeding that of the measuring instruments, in order to test the accuracy of the interlock operation.