Introduction Nine typical hydraulic circuits will be

investigated Several problem scenarios will be presented for

each circuit Each problem scenario is independent and does

not relate to any previous one for the same circuit

The class will participate in determining the possible solution(s) for each problem

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Unloading Relief Valve Circuit

a

2,000 psi

Unloading Relief Valve Circuit

Problem #1: When we start the machine, we find that there is not any flow indicated by the flowmeter when the directional control valve is in the neutral position.

Solutions: Problem #2: We find that the system is operating at 2,000 psi

when the directional control valve is in the neutral position. Solutions:

Problem #3: The system is suppose to operate at 1,800 psi to

extend the cylinder, the pressure gauge only indicates 30 psi. The cylinder will not extend.

Solutions:

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Relief Valve - Multiple (3) Pressure Circuit

b a

3,000 psi

1,000 psi 2,000 psi

Multiple Pressure Relief Circuit Problem #1: Look at the Multiple Pressure Relief Valve Circuit

to determine what the maximum pressure in the system should not exceed when the solenoid operated directional control valve on the relief solenoid(s): “a” is energized = __________________ psi “b” is energized = __________________ psi both are at rest, not energized = _______ psi

Problem #2: System will only operate at 2,000 or 3,000 psi, we

are unable to get the 1,000 psi setting. Solutions:

Multiple Pressure Relief Circuit

Problem #3: System will only operate at a maximum pressure of 1,000 psi when 2,000 psi is required in the system.

Solutions:

Problem #4: System will only operate at 3,000 psi, we are unable to adjust to 1,000 or 2,000 psi.

Solutions:

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Pressure Compensated Pump

2,400 psi

Pressure Compensated Pump Circuit

Problem #1: Normal pump flow is 10 GPM at 2,000 psi, when a pump test is performed. Due to an operator complaint of slow cylinder speed, flow was found to be 5.5 GPM at 2,000 psi.

Solution:

Problem #2: Normal operating temperature of the system was 110°F when the system was installed four years ago. A temperature check of the system indicates an operating temperature of 155°F.

Solution:

Pressure Compensated Pump Circuit

Problem #3: With the directional control valve in the neutral position, the pressure gauge indicated 2,200 psig.

Solution:

Problem #4: The machine operator has called you over to examine his machine, you find that the maximum pressure obtainable is 1,500 psi.

Solution:

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High Low Pump Circuit

a b

500 psi 2,500 psi

High Low Pump Circuit

Problem #1: High volume pump does not unload. Solution:

Problem #2: System pressure will not exceed 500 psi for

the feed stroke. Solution:

Problem #3: High volume pump is not putting flow into

the circuit when the pressure is less than 500 psi. Solution:

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Counterbalance Valve Circuit Load

a b

1,650 psi

Counterbalance Valve Circuit

Problem #1: The cylinder does not retract. Solution:

Problem #2: The cylinder will not remain in fully retracted

position when directional control valve is in the neutral position, it drifts down.

Solution:

Problem #3: The cylinder will not extend or lower the load. Solution:

Accumulator Circuit

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c a b

1,000 psi

1,200 psi

A B

P T

Accumulator Circuit

Problem # 1: The cylinder will not move, no pressure indicated in system.

Solution:

Problem #2: The cylinder extends, the maximum pressure indicated in circuit is 1,000 psi.

Solution:

Problem #3: The cylinder fails to move at rapid traverse speeds. Solution:

Sequencing Circuit

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a b c d

e

1,000 psi

1,200 psi

2,350 psi

Sequencing Circuit Problem #1: The clamp cylinder crushes the work piece. Solution:

Problem #2: The drill cylinder is not extending at the proper

time. Solution:

Problem #3: The system operates at a reduced speed. Solution:

Problem #4: The pump is noisy. Solution:

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Wire Winding Machine Circuit a b

Wire Winding Machine Circuit

Problem #1: The system does not operate, but the electric motor runs.

Solution: Problem #2: The motor does not decelerate. Solution: Problem #3: The directional control valve will not shift. Solution: Problem #4: The hydraulic motor operates erratically. Solution: Problem #5: The hydraulic motor will not start under load. Solution: Problem #6: The system is overheating. Solution:

Closed Circuit Hydrostatic Transmission

220 psi 180 psi

Closed Circuit Hydrostatic Transmission

Problem #1: The system will not operate in either direction. Solution: Problem #2: The system only operates in one direction. Solution: Problem #3: There is a loss of power in both directions. Solution: Problem #4: There is a loss of power in one direction only. Solution: Problem #5 System operating hot. Solution:

Thank you

Drill and Ream Circuit

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V3 a

a V2

ream Drill coarse feed

fine feed

Drill and Ream Circuit Problem #1: The system has a “rapid traverse” cycle, the system

operates in the coarse feed, fine feed, and ream cycles only. Solution: Problem #2: The system is “rapid traverse, coarse feed, and

ream”, we cannot obtain the fine feed part of the cycle. Solution: Problem #3: The system is operating in the “rapid traverse”

mode only, we are unable to get the coarse feed, fine feed, and ream cycles.

Solution:

Drill and Ream Circuit Problem #4: The system is operating in the “rapid traverse and

ream” cycles only, we are unable to get the coarse or fine feed part of the normal cycle.

Solution: