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Interlock test plan for large-scale units 1. Startup and shutdown conditions of the unit: Whether the startup and shutdown conditions of the unit are met depends on whether the instrument monitoring system is functioning properly and whether the interlock protection system is in good condition. Before starting the machine, it is necessary to determine what the conditions for starting and stopping it are; each of these conditions should be tested individually. The switches and pressure transmitters are first tested separately and then together. During individual testing, the pressure transmitters and switches are calibrated first, after which their associated circuits and alarms are checked. When testing in combination, once all conditions are met, one condition is intentionally violated to check the output related to the starting and stopping conditions as well as the alarms. Driving conditions confirmation form: Parking conditions confirmation form: 2. Inspection and testing of the lubricating oil system. The lubricating oil system of the unit is an essential condition for its safe operation. First, it is necessary to check that the pressure transmitter or pressure switch is functioning properly. Once the transmitter and switch are in good working order, coordination with the process team should be sought to carry out the interlock tests for the lubricating oil system. 2·1 Test for low outlet pressure alarm of the main oil pump: For large-scale units, to ensure safety, both a main oil pump and an auxiliary oil pump are used, with one acting as a backup to the other through outlet pressure interlocking. Units without a high-level oil tank are equipped with an emergency oil pump to ensure the proper operation of the lubrication system. The main oil pump is running, the auxiliary oil pump is in the “automatic” position, and the oil pressure is normal. Connect to the outlet return valve of the pump that is started slowly according to the process; when the oil pressure drops to a certain level, the valve will operate, the standby oil pump will start automatically, and an appropriate alarm will be issued. Record the oil pressure when it drops to the value at pump startup, and check whether the set values of the switch or transmitter match the actual operation. 2·1 Test for low-low pressure alarm at the main oil pump outlet: For large-scale units, a \"three-out-of-two\" interlock is generally used for low-pressure conditions at the main oil pump outlet. The main oil pump is running, the auxiliary oil pump is in the “manual” position, and the oil pressure is normal. The unit interlock is in the reset state, allowing the process to gradually reduce the oil pressure; when the oil pressure drops to the level at which the \"two-out-of-three\" interlock triggers, an appropriate alarm is issued. Record the oil pressure value and compare it with the set value to determine whether the actual oil pressure triggers the interlock action in accordance with the settings of the switch or transmitter. For the turbine, check whether the stop oil solenoid valve operates after the oil pressure interlock activates, and whether the main interlock is triggered. Oil system test table: Tag number, Set value, Operating value, Operating result. 3. Inspection of the control oil system – Control oil is an important component of turbine control; tests on control oil must be carried out in conjunction with the process parameters. Control oil involves primary oil, starting oil, shutdown oil, return oil, secondary oil, as well as oil solenoid valves and electro-hydraulic converters. 3·1 Testing and inspection of the control oil accumulator: The accumulator is a key device for generating start-up oil, shutdown oil, and secondary oil; its performance has a direct impact on the operation of the unit. Tests on the accumulator are primarily carried out using specialized procedures, with the assistance of instruments. The unit’s process interlocks are satisfied; by pressing the reset button in the control room, the three-way solenoid valve that controls the quick-shut valve (main steam valve) becomes energized ； Rotate the accumulator handle according to the procedure, generate trip oil, open the main steam valve, and reduce the oil pressure to zero ； The procedure involves pressing the stop button for the main oil pump; the auxiliary oil pump then starts automatically. If, at this point, the trip oil switch does not activate and the main steam valve remains open, it indicates that the accumulator is in good condition. Otherwise, the performance of the accumulator needs to be checked. Regulator Performance Check Sheet: Primary oil pressure, Secondary oil pressure, Shutdown oil pressure, Startup oil pressure, Before pump switchover, After pump switchover – Is it qualified? 3·3 Electro-hydraulic converter test check: The electro-hydraulic converter converts the shutdown signal into an oil pressure signal based on a certain electrical signal ratio, thereby controlling the opening degree of the high-pressure valve or low-pressure valve to regulate the speed of the unit. A shutdown oil is established for the process; the instruments are connected to signal generators, which send out specific electrical signals as required by the electro-hydraulic converter. Signals of 4mA, 8mA, 12mA, 16mA, and 20mA correspond to secondary oil pressures of 0.15 Mp, 0.225 Mp, 0.3 Mp, 0.375 Mp, and 0.45 Mp respectively, while the opening degrees of the high-pressure valve or low-pressure valve correspond to 0%, 25%, 50%, 75%, and 100% respectively. If there is a large discrepancy between the electrical signal, the secondary oil pressure, and the valve opening, readjust the output and identify the cause. This test can also be carried out before the unit is put into operation, as a test specific to the governor, to check whether the governor’s output is normal. Electro-hydraulic converter test sheet: Electrical signal, secondary oil pressure, opening degree of the control valve – whether it is proportional. 3·4 Unit emergency stop test: The emergency stop test is designed to verify whether the emergency stop interlock system is safe and reliable in abnormal conditions. The conditions for starting the unit are met; the unit’s interlocks are reset, and the emergency shutdown oil supply is activated. The main steam valve is opened. Tests are conducted using the on-site stop lever connected to the oil solenoid valve, the on-site emergency stop button, the central control emergency stop button, or the control panel emergency stop button. When the stop lever is pulled or the emergency stop button is pressed, it is checked whether the oil solenoid valve that controls the main steam valve loses power, how the emergency shutdown oil switch operates, and what the speed of closure of the main steam valve is. Relevant alarms are also monitored. 4. Unit surge protection test: The surge valve is an important safety valve for the unit. Surge phenomenon is an inherent characteristic of the unit, and preventing such surge requires reliable surge protectors or surge control valves. Anti-surge valves are required to have a fast-opening and slow-closing characteristic in order to respond quickly when the unit approaches surge. When the unit is shut down, it is necessary to inspect and verify the flow meters, pressure gauges, temperature sensors, and anti-surge valves related to the anti-surge regulator. Ensuring that the measuring instruments and control valves are in good condition is key to the proper operation of the unit’s anti-surge regulator. When the unit is started up, the anti-surge valve must be adjusted; the solenoid valve associated with this valve should be powered, and signals should be applied using a signal generator in order to ensure that the control valve operates with good linearity. During shutdown, the solenoid valve of the anti-surge valve loses power; when the operating conditions of the unit are suitable, the solenoid valve is energized. The adjustment of the anti-surge regulator takes place in accordance with the unit’s load. The testing of this regulator involves checking that when the set value is lower than the actual process value during operation, the control valve opens quickly, which indicates that the anti-surge regulator is functioning properly. Anti-surge valve test table: MV values – 4mA, 8mA, 12mA, 16mA, 20mA; Valve opening degree. Time for the anti-surge valve solenoid to open in the event of a power loss: seconds. 5. Crankshaft rotation tester: If a large-scale unit is equipped with a crankshaft rotation device, this device must be operated before starting up and after shutting down the unit. There are two types of crankshaft rotation systems: those driven by motors and those driven without motors. For motor-driven systems, the motor will start once the necessary conditions are met. For non-motor driven turntables, the focus is on whether the solenoid valves controlling the oil flow are powered or not. During testing, start the turntable oil pump, and check the proximity switches at the two positions, as well as the speed contacts provided by the governor. Conditions for starting the cranker: 1. Voltage level when the position switch is closed; 2. Voltage level when the position switch is open; 3. Condition of the governor’s output contacts, etc.; 6. Unit overspeed test. The unit’s overspeed protection includes both mechanical and electronic mechanisms. In the case of mechanical overspeed, when the unit’s speed reaches the level at which the emergency shutdown device activates, the centrifugal force causes the weight or ring attached to this device to fly out and strike the emergency shut-off valve, thereby causing it to operate and quickly closing the main steam valve and control valves. Electronic overspeed protection comes in two forms: specialized overspeed protectors and electronic governors. An electronic overspeed protection system is a device designed to prevent rotating machinery from operating at excessive speeds, which could otherwise damage the equipment. It uses speed measurement gears or passive or active speed sensors as primary sensing elements, while a monitoring unit based on a microprocessor counts the detected speed signals and performs logical operations to generate corresponding protection signals. Electronic overspeed protection systems typically use three identical monitoring devices to measure the same rotational speed, and after applying a \"3-out-of-2\" logic operation, they output a protection signal to trigger shutdown. 6·1 Over-speed protection test of the electronic governor (505 or 505E) (1) Over-speed protection test of the electronic governor when the unit is shut down. Short-circuit the external trip signal of the electronic governor, and use a signal generator to replace the speed sensor for simulation tests. Operate the governor and gradually increase the speed signal; when the overspeed protection light flashes (OVERSPEED TEST ENABLE), record the comparison between the speed signal and the overspeed protection set value. (2) Over-speed protection test of the electronic governor during unit operation. When the unit is operating normally, press the “OVERSPEED TEST ENABLE” button on the governor, while continuously increasing the turbine speed until the red light on this button starts to flash. At that point, record the turbine speed value; the governor will then send an over-speed protection signal, causing the unit to shut down. Verify whether the turbine’s speed at shutdown matches the set value. Over-speed protection test table: Over-speed protection setting value, over-speed shutdown speed value, whether it meets the requirements. 6·1 Over-speed protector (WOODWARD PROTECH 203 system) over-speed protection test – The over-speed test of the over-speed protector is generally carried out with the unit not in operation. Simulate tests on the system by using two signal generators in place of the speed sensor; gradually increase one speed signal, and when the system triggers an alarm, record the comparison between the speed signal and the set value. Then increase another speed signal until the relay of the overspeed protector activates, and record the comparison between that speed signal and the set value to verify the operating value of the \"three-out-of-two\" interlock mechanism. Over-speed protector test table: Set value, Over-speed activation speed value, Activation result, Speed signal 1, Speed signal 2, Speed signal 3. 7. Vibration displacement detection system test: The Bentley 3300 system consists of a frame, power supply, system detector, and test table, while the 3500 system comprises a power supply card, test table, communication card, relay card, etc. When the system is operating properly and the displacement and vibration levels are within the set limits, no alarm is generated. 7·1 Sensor characteristic curve testing: Testing of the sensor characteristics is required for newly replaced probes or those suspected to have issues, in order to ensure their proper performance. (1) Set the TK3 shaft micrometer to zero, place the probe in the shaft micrometer so that its end face makes light contact with it, secure the probe, and adjust the zero setting of the shaft micrometer to ensure proper positioning of the probe. (2) Connect the probe and preamplifier using a matching extension cable. (3) Disconnect the input power supply; connect the negative terminal of the power supply to the VT terminal of the preamplifier, and connect the positive terminal of the power supply to the COM terminal. (4) Connect a digital multimeter to the OUT and COM terminals of the preamplifier. (5) Connect to power. (6) Use the shaft micrometer to rotate the rod micrometer away from the contact point in increments of 0.25 mm in order to increase the gap, and record the DC voltage output of the preamplifier at each step. (7) Record the DC voltage values at ten points corresponding to 0, 0.25 mm, 0.50 mm…2.50 mm; then plot a calibration graph for the sensor system with the gap on the horizontal axis and the voltage on the vertical axis. (8) If the probe’s characteristic curve is good, especially if the linear section around 1.27 mm remains linear, then the probe performs well. Probe characteristic curve record sheet: Gap value (mm), Voltage value (V). After the vibration probe is installed, it is necessary to measure the voltage at the probe gap; the output voltage of the preamplifier should be consistent with the voltage shown on the meter, around 9.5V ± 0.5V. The installation of the displacement probe must be coordinated with the machinery; the machinery provides the displacement value, and after the probe is installed based on this value, the machinery generates another displacement measurement. If the displacement value provided by the machinery matches the one detected by the 3300 system or the 3500 system, then the probe is installed correctly. If there is a discrepancy, find the reason. August 2007