Job Sheet 5 Hydraulic Unit Circuit

Transcription

1 Job Sheet 5 Hydraulic Unit Circuit The key components involved in the cylinder piston rod actuation (solenoid valves SV1, SV2, SV3A, and SV3B) are within the core components of the hydraulic unit of the hydraulic pitch hub trainer. The hydraulic pump supplies the pressure required by the hydraulic unit. It is assisted by the pressure accumulator that provides the immediate response to compensate system pressure loss, while the hydraulic pump completes the required pressure to maintain the system within a working pressure range. These automated tasks are commanded by the PLC unit through the pressure transducer PSP2, which constantly monitors the system pressure by converting pressure into analog low-level electrical signals, providing an electrical output that is proportional to the sensed pressure back to the PLC. The solenoid valve SV1 is activated (solenoid turned on) when pressure reaches its peak at 925 psi. When pressure descends to 900 psi, the valve solenoid turns off and the hydraulic pump stops. If SV1 is manually opened (knob), the hydraulic pump runs continuously, the system working The solenoid valve SV2 valve controls the pressure downstream (the actuator s working pressure) of SV3A/B by stabilizing the pressure at approximately 900 psi. SV2 valve solenoid lights up when the hydraulic unit is started and the pressure reaches 600 psi, and stays lit until the hydraulic system is turned off. SV2 valve solenoid must be on (locked position) to effectively work in either Auto and Manual modes. During the hydraulic unit operation, the hydraulic pump starts to compensate pressure loss within the system (e.g., when the cylinder piston rod is actuated). If the SV2 solenoid valve is turned off, or SV2 is manually opened (unlocked), that branch of the circuit gets over pressured (above 925 psi). If that happens, the relief valve releases the excess pressure; but the hydraulic pump remains running in a loop to compensate the loss of pressure, which continuously oscillates between 400 psi and 925 psi. Solenoid valves SV1, SV2, SV3A and SV3B can be activated individually, or turned on/off on the HMI screen Debug Mode section in the Services menu. Although, precautions might be taken to prevent the hydraulic pump from running continuously. Many valves of this type can be also manually overridden. The override provides a means of shifting the solenoid valve due to a loss of power or a coil failure. Depending on the valve, they can be manually operated by pulling the knob (SV3), twisting (SV2), pulling and twisting (SV1), or just lifting the lever (MV1). Festo Didactic Inc

2 In the event the motor pump is not operational due to a power or mechanical failure, the hydraulic manual pump must be actuated in order to provide enough pressure to retract the cylinder piston rod to its home position. In this case, SV3 valve must be manually overridden. On the other hand, if the hydraulic system is over pressured, the manually operated relief valve MV1 must be actuated. The four-way, three-position double solenoid (SV3A and SV3B) directional control valve is used to alternately extend and retract the cylinder piston rod that operates in two directions (doubleacting cylinder). In order to move the actuator, the valve solenoids must be energized. In a wind turbine scenario, the PLC system receives feedback information from the different external sensors when the wind speed and wind direction change. It also receives feedback from internal sensors (positioning sensors, pressure sensors, etc). Based on current conditions, the PLC sends commands to the appropriate component(s) to execute the required action. Depending on the blade pitch position (directly related to the piston rod extension), SV3A is energized to extend the cylinder piston rod, pitching the rotor blade clockwise (Figure 5-1). Cylinder Extends SV3A Energized Figure 5-1. SV3A Valve Solenoid Energized. 68 Festo Didactic Inc

3 By default, the valve solenoids are de-energized (normally closed position). In this state, the piston rod does not actuate (Figure 5-2). SV3A De-energized Cylinder Steady SV3B De-energized Figure 5-2. SV3A and SV3B Valve Solenoids De-energized. If SV3B is energized, the cylinder piston rod is retracted, and the rotor blade is turned counterclockwise (Figure 5-3). Cylinder Retracts SV3B Energized Figure 5-3. SV3B Valve Solenoid Energized. Hydraulic Pitch Control Flowchart actions based on those measurements. The program can be represented symbolically using a steps. Festo Didactic Inc

4 Although the hydraulic pump activity (hydraulic pump routine) is included in the hydraulic pitch hydraulic unit starts, the hydraulic pump supplies the required pressure to the system. The pressure is monitored by the pressure transducer. Once the pressure reaches 600 psi, the SV2 valve solenoid is turned on to keep the working pressure above that limit. When the pressure reaches its threshold of 925 psi, the SV1 valve solenoid is tuned on and the hydraulic pump stops. Excess pressure is released by the relief valve. When pressure stabilizes below this value, the SV1 valve solenoid is tuned off. Hydraulic Pump Routine System Pressure < 600 PSI? SV2 = ON? SV2=ON System Pressure > 925 PSI? Hydraulic Pump Runs SV1=ON Stop Hydraulic Pump SV1=OFF Exit Routine Figure 5-4. Hydraulic Pump Routine Flowchart. 70 Festo Didactic Inc

5 program. If we run through the diagrammed process, we see that all solenoid valves are off before the hydraulic unit is started. The cylinder piston rod position is constantly monitored by the PLC, which controls whether it is moving or stopped and at any position. When the PLC receives feedback information from the wind speed sensors, it decides whether the solenoid valve must be energized in order to extend or retract the cylinder piston rod for pitching the blades, or if it should take no action (blade pitch position is set to current wind speed for maximum wind energy capture) and keep the solenoid valve de-energized (piston rod stopped). te that the hydraulic pump routine is always present in the piston rod extension and retraction loops. The cylinder piston rod actuation produces a pressure drop in the system, which requires the accumulator and the hydraulic pump to take action to compensate for pressure loss and keep the system pressure within its working pressure range. If an emergency stop condition is present, the system stops and the cylinder piston rod retracts to home position. Festo Didactic Inc

6 Start Trainer SV1=OFF SV2=OFF SV3A=OFF SV3B=OFF Hydraulic Pump Routine Piston Rod Position Sensor=90º? Piston Rod Stopped at Home Position Piston Rod Position Sensor=0º? Piston Rod Stopped at Maximum Position SV3A=ON? Piston Rod Stops Hydraulic Pump Routine SV3B=ON? Piston Rod Extends Piston Rod Stops Hydraulic Pump Routine Piston Rod Retracts E-Stop Pressed? Exit Figure 5-5. Hydraulic Pitch Control Flowchart. 72 Festo Didactic Inc

7 OBJECTIVES In this job sheet, you will determine the logic involved in the cylinder actuation to pitch the blades to the current wind speed in a wind turbine hydraulic pitch hub. You will perform a hands-on activity that requires you to manually operate the hydraulic unit in order to actuate some of its components. EQUIPMENT REQUIRED Refer to the Equipment Utilization Chart in Appendix A to obtain the list of equipment required for this job. SAFETY PROCEDURES Before proceeding with this job, complete the following checklist. You are wearing safety glasses. You are wearing safety shoes. You are not wearing anything that might get caught such as a tie, jewelry, or loose clothes. If your hair is long, tie it out of the way. The working area is clean and free of oil. Your sleeves are rolled up. PROCEDURE Setup Perform the Basic Setup procedure described in Appendix D. Perform the Lockout/Tagout procedure described in Appendix D. Begin Perform the Energizing procedure described in Appendix D. Apply power to the training system by turning on the Main power switch. Festo Didactic Inc

8 Press the green Start button. Ensure the Emergency Stop switch is on (pulled outward). On the main screen of the hydraulic hub trainer HMI, verify that there are no alarms triggered (in System Status box and Alarm button). On the Main section window, tap the Start Trainer button. The hydraulic unit starts. Tap the Manual button (to the right, below the wind vane indicator) to enable manual operation of the trainer functions. w, tap the Manual menu button (on bottom of the screen). Tap the Move to Position button to expand the cylinder piston rod to its maximum length. Read and record the actual blade pitch position on the HMI (in degrees). w, expand the menu for more options by tapping the right arrow button (on the right of the screen). On the Hydraulic Unit Control section, tap the Stop button to turn the hydraulic unit off. The Off-Drive ready message displays. Read and record the pressure displayed on the screen for PSP2: (psi). It should match the pressure read on the hydraulic unit GP2 gauge (on the right). The accumulator should stay charged when the hydraulic unit is stopped. Gently actuate the manual relief valve on the hydraulic unit block port MV1 to depressurize the circuit. Observe the system pressure dropping by reading the pressure value displayed on the screen (PSP2) and reading the GP2 gauge. Stop actuating this valve when system pressure is between 200 psi and 250 psi. 74 Festo Didactic Inc

9 Go back to the previous menu by tapping the left arrow button (on the right of the screen). Rotate the blade toward its home position (90 ) by tapping the Jog + button. When it stops, read and record the blade actual pitch position (in degrees). Read and record the pressure measurements on the GP2 gauge: (psi). Did the cylinder piston rod retract completely? If the blade position recorded in procedure step 20 was not 90º, what might have happened? Why did this happen? If blade position recorded in procedure step 20 is not 90º, what should you do to make the blade reach its home position? As the hydraulic unit pump is not operational (stopped in procedure step 14), the hand pump must be used to provide pressure to the system. Manually pump pressure into the system until the GP2 gauge reads 300 psi. SV3 is the solenoid valve that allows the cylinder piston rod to extend (SV3A) or retract (SV3B). Many valves of this type can be manually overridden. The override provides a means of shifting the solenoid valve due to a loss of power or a coil failure. Festo Didactic Inc

10 Manually operate the SV3 valve by pulling the knob until the cylinder piston rod retracts to its home position. Once the cylinder piston rod is completely retracted, make sure to return the SV3 valve knob to its original position. Then, go to the Manual section of the HMI. On the Hydraulic Unit Control screen, tap the Start button to turn the hydraulic unit on. The Pump Enable waiting to run message displays. Shut down the trainer. Perform the Lockout/Tagout procedure (see Appendix D). Review Questions 1. a. gets energized (turned on). b. gets energized (turned on) when system pressure reaches 600 psi. c. gets energized (turned on) when system pressure reaches 925 psi. d. gets energized (turned on) when system pressure reaches 925 psi. Then, it turns off. 2. In order to effectively work in Automatic mode, SV2 valve solenoid a. must be manually set to on (locked position). b. must be manually set to off (unlocked position). c. can be manually set to either the locked or unlocked position. d. cannot be manually set. 3. SV3A is energized a. to extend the cylinder piston rod, pitching the rotor blade clockwise. b. to extend the cylinder piston rod, pitching the rotor blade counterclockwise. c. to retract the cylinder piston rod, pitching the rotor blade clockwise. d. to retract the cylinder piston rod, pitching the rotor blade counterclockwise. 76 Festo Didactic Inc