LAB _7_301305308

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Centennial College *

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226

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Mechanical Engineering

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Oct 30, 2023

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Automation & Robotics ROBO-226 Fluid Power Lab 7: Metering Circuits Objective: Control the speed of a cylinder using Meter In and Meter Out principles. Upon successful completion of this lab, the learner will be able to: ▪ Design and construct Meter In, Meter Out and Bleed Off hydraulic circuit to control the speed of a cylinder. ▪ Observe pressure, flow rate and time readings indicated on the various gauges. ▪ Identify the difference between Meter IN, Meter OUT and Bleed OFF circuits. Procedure: Using Hydraulic training bench Meter IN Circuit: Set the system pressure to 800 psi. Using the ANSI schematic circuit as a guide, connect the Meter IN circuit illustrated on the training bench. Set the FCV to fully open. Using the SDCV selector switch cycle the cylinder. After each cycle of the cylinder close the FCV by one half turn and record the readings on the pressure gauge, flow meter and time to extend the cylinder until the FCV is almost fully closed. Dis-assemble the Meter IN circuit. Meter OUT Circuit: Set the system pressure to 800 psi. Using the ANSI schematic circuit as a guide, connect the Meter OUT circuit illustrated on the training bench. Set the FCV to fully open. Using the SDCV selector switch cycle the cylinder. After each cycle of the cylinder close the FCV by one half turn and record the readings on the pressure gauge, flow meter and time to extend the cylinder until the FCV is almost fully closed. Dis-assemble the Meter OUT circuit. Bleed OFF Circuit: Set the system pressure to 800 psi. Using the ANSI schematic circuit as a guide, connect the Bleed OFF circuit illustrated on the training bench. Set the FCV to fully open. Using the SDCV selector switch cycle the cylinder.

ROBO 226 Fluid Power Lab 6: Metering Circuits After each cycle of the cylinder close the FCV by one half turn and record the readings on the pressure gauge, flow meter and time to extend the cylinder until the FCV is almost fully closed. Dis-assemble the Bleed OFF circuit. METER-IN SCHEMATIC

METER-OUT SCHEMATIC

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BLEED-OFF SCHEMATIC 1. Describe what is meant by the term “opposing load” as it applies to cylinder motion. ANS. If the load is acting in opposing direction to the cylinder or motor it ’ s said to be opposing load. In the lab the load is opposing to the motor. 2. Explain why the Meter in principle can’t be used on application where the load can “runaway”. In application runaway load, the counterbalance valve makes cylinder movement resistive. 3. If the bleed off needle valve opening is reduced, how will that affect the cylinder speed? The speed will reduce slowly. If you keep reducing the opening the speed will reduce drastically.

4. Think of simple examples where bleed off circuit could be used. Bleed-off circuits are used where pressure is reasonably constant and precise control is not required. These circuits are mostly used in broaching machine, shapers, planers, where large quantity of fluid is used. 5. Describe the difference between meter in and meter out flow control. In meter-in system the external load opposes the direction of motion of cylinder. On the other hand, in meter-out system the oil flow rate out of the cylinder. Flow control valve ’s connection is different in both circuits. There is no pressure drop in meter-out flow control. 6. Define pressure intensification. In the circuit, the piston side in a double acting cylinder is pressurized and at the same time fluid is prevented from escaping from the rod side, pressure will intensify. This is called pressure intensification. 7. What is the purpose of the check valve in the flow control valve? The check valve is a device that allows the flow of fluid to move in only one direction. The primary purpose of a check valve is to prevent backflow in the system. METER-IN table data PRESSURE GAUGE PSI FLOW METER IN GPM TIME IN SECONDS 100 psi 4 GPM 1.53 sec 200 psi 4 GPM 1.69 sec 650 psi 3 GPM 2.06 sec 690 psi 2.4 GPM 2.89 sec 720 psi 1.5 GPM 4.88 sec 750 psi 0.5 GPM 16.83 sec METER-OUT table data PRESSURE GAUGE PSI FLOW METER IN GPM TIME IN SECONDS 150 psi 2.6 GPM 1.73 sec 160 psi 2.6 GPM 1.43 sec 370 psi 2.6 GPM 1.54 sec 700 psi 2.5 GPM 1.56 sec

1070 psi 2.0 GPM 2.03 sec Psi230 0.6 GPM 11.10 sec BLEED-OFF table data PRESSURE FLOWMETER TIME 150 psi 1.4 GPM 2.05 sec 150 psi 1.1 GPM 1.94 sec 150 psi 0.6 GPM 1.67 sec 150 psi 0.1 GPM 1.58 sec

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