Introduction to Fault Finding Section
Fault finding in modern complex hydraulic systems can be an extremely time consuming task. This can be made easier by using one of Kisakurek' Flowmeter.
The Kisakurek Flowmeter has been designed for easy connection into the Hydraulic Circuit so that flow, pressure and temperature can be easily checked, without having to remove components from the machine.
The Kisakurek Flowmeter will take full back pressure up to 400 bar and the built-in loading valve enables many of the operating conditions to be simulated. The Flowmeter can be used to control pressure and monitor the flow in both directions. This feature makes it much easier to test cylinders, motors, and hydrostatic transmissions. It also avoids the risk of wrong connection on a complex or unfamiliar circuit where the direction of flow is not known.
All tests should be carried out at normal operating temperatures because as the oil temperature increases it becomes thinner and therefore any internal leakage becomes greater.
Speed of testing will be increased if quick disconnect couplers are used to attach the test unit. A preliminary check of the hydraulic system's oil supply (level), pump rotation, filters, oil lines, cylinder rods as well as looking for external leaks should be made prior to installing the Hydraulic Tester.
1.0 Test 1 - Pump in Line
1.1 Install the Flowmeter into the system between the pump outlet port and the inlet to the directional control valve.
1.2 Open Test Loading Valve to read maximum pump flow at minimum pressure.
1.3 Close Loading Valve slowly to increase pressure and note reduction of flow as the pressure is increased to maximum pump pressure to determine pump condition.
1.4 Pump flow at rated pressure can now be checked against the pump manufacturer's specifications. The decrease in flow from minimum pressure to maximum pressure determines the pump condition. Typically a worn or damaged pump will lose 20 - 30 percent. A pump that delivers low flow at both minimum and maximum pressure indicates suction problems. Blocked suction filters and pump cavitation problems can also be checked by recording the pump flow at various engine speeds.
This test method can be used at several points in the circuit and the machine can be used under its normal working conditions to evaluate the performance of circuit elements, such as pump, control valve, cylinder and hydraulic motor.
2.0 Test 2
2.1 A 'Tee' must be installed at one point between the pump and control valve when connected to the 'IN' port of the Flowmeter. The 'OUT' port of the Flowmeter is connected back to the tank. Make sure loading valve is open.
2.12 Pump Test. Disconnect the plug connection to control valve and proceed as in points 1.2, 1.3 and 1.4 of the previous section .
2.2 Overall System and Relief Valve Test 2
(For Relief valve integral and Directional Control Valve)
2.21 Connect control valve to 'Tee'. Operate control valve to extend the cylinder to end stroke.
2.22 Close the Flowmeter Loading Valve while watching pressure and flow meter reading. Pressure will increase until relief valve opens at which point flow reading will return to Zero. Note or record pressure at this point. Adjust the relief valve if the pressure is below the recommended setting. It
is not unusual for a relief valve to start cracking open below a maximum pressure setting causing considerable leakage and loss of machine performance. The cracking pressure can be checked by increasing the pressure slowly and noting the pressure at which the flow starts falling rapidly to zero. The maximum relief valve setting is when the flow is at zero.
2.3 Control Valve, Cylinder 'Tee' Test
2.31 Put control valve in power position. (On multiple spool valves, only one spool should be in a power position at any one time). The cylinder should be extended to the end of the stroke.
2.32 Close Flowmeter Loading Valve slowly while recording pressure and flow rate. 2.33 Repeat 2.32 for power position, for all spools of all control valves.
2.331 If all components are in good operating condition, pressure and flow measurement should be the same as in the pump test paragraph 1.0.
2.332 If a decrease in flow of any control valve position is noted, leakage is indicated in this control valve or cylinder. See paragraph 2.4 for test routine to determine which is a fault.
2.333 If the decrease in flow is the same for the control valve(s) in all positions, it indicates the relief valve is at fault. (NOTE: This can also indicate some other leak is present in the control valve such as a defective casting - but always check the relief valve immediately).
2.4 Additional test to locate fault in control valve of cylinder (see paragraph 2.332). Disconnect line to cylinder and plug valve port.
2.41 Place control valve handle in position where greatest decrease of flow was noted.
2.42 Close Flowmeter Loading Valve and record both pressure and flow.
If the same decrease in flow is noted as in test per paragraph 2.332 then the control valve is at fault. if the flow readings are now higher and comparable to the other control valves, then a faulty cylinder is indicated.
3.0 Directional Control Valve 'In Line' Test 3
3.01 To check relief valve pressure setting where relief valves are integral with control valve, install flow meter in the cylinder line as shown in Figure1B, ensuring that loading valve is open
(turn anti-clockwise). Start pump and operate the lever on the valve in which the flowmeter is situated to raise load. Slowly close the unloading valve (turn clockwise), reading pressure and flow, continue until loading valve is fully closed, pressure reading obtained is then relief valve pressure. Compare with manufacturer's recommendations. Adjust relief valve if necessary. When using the Kisakurek flowmeter, the cylinder and valve may be tested in the opposite direction by operating the lever to retract the cylinder.
3.02 Control Valve Leakage
With flow meter installed as in 3.01, repeat test and compare flow readings for comparable pump test 1.3. Differences in flow readings indicate leakage within control valve. Repeat test for all power ports to fully determine valve condition. Replace control valve block or valve segment where necessary.
3.1 Cylinder Test (See Figure 1B)
3.11 If the cylinder is slow in operation or cylinder 'creeps' under load the following test should be carried out to check the cylinder seals.
Install the flow meter 'in line' as shown in Figure 1B. Actuate the cylinder to raise load. Note flow and pressure readings, also note the time taken by the cylinder to reach full stroke. Compare all readings with manufacturer's recommended figures. If the flow is correct but time to extend cylinder is greater than expected, leakage across the cylinder seals is indicated. If flow is lower than expected, investigate control valve function. See Test 3.0.
The cylinder may be tested in the other direction by selecting the directional valve lever and recording the flow.
3.2 Motor Test
3.21 Motor performance is checked by measuring the flow and comparing it to the equivalent motor speed. Install the tester in the line upstream of the motor as indicated by the arrow A in Figure 1B. Fully open the loading valve and operate the directional control valve ensuring the motor rotates in the correct direction. Allow motor to run under normal load. Note the flow and pressure readings. If flow is below manufacturer's data sheet or lower than pump test (1.0) investigate control valve function.
NOTE: The motor may only be tested in reverse if it has an external drain. Do not pressurize the outlet port of the motor without first checking the allowable back pressure with the manufacturer.
3.22 Measure hydraulic motor rpm with tachometer when motor is working at normal pressure. If the motor speed is low and the inlet flow in 3.21 is found to be correct, internal leakage in the motor is indicated. Check with data sheet and change motor if necessary.
3.23 When the motor does not have an external drain or the motor cannot be back pressure loaded connect tester in the other line and repeat the test 3.21 and 3.22 for the other motor direction.
3.3 Alternative Cylinder and Motor Test
3.31 Both motors and cylinder may also be tested as shown in Figure 2B. Disconnect the two lines from the motor and connect the tester into these lines. Fully open the loading valve, start the pump and bias the directional valve to allow flow into the inlet port of the tester. Slowly close the loading valve by turning clockwise and note the flow and pressure. If the flow is below the manufacturer's data or lower than the pump flow test (1.0) investigate the control valve function. See test (3.0). If the flow is correct and the speed is slow this indicates a defective motor or cylinder.
When using Bi-directional flowmeter operate the directional valve to reverse the flow through the tester and record the flow throughout the pressure range.
PRELIMINARY: Check oil level in tank, pump drive, valve linkage for damaged parts, external oil leaks etc.
Further System Diagnosis
1. Components not properly cleaned after servicing.
2. Air Breathing not installed.
3. Tank not properly gasket fixed.
4. Pipe lines not flushed when installed or after servicing.
4. Incorrect tank design without baffle stop provide settlement traps. 6. Filters not replaced at correct intervals.
Oil with foam
1. Return tank line not below fluid level. Broken pipe. 2. Inadequate baffles in reservoir.
3. Fluid contamination.
4. Suction leak to pump allowing oil to aerate.
Oil with moisture
1. Moisture in cans used to fill tank.
2. Water drain not fitted to lowest point in the tank.
3. Cold lines fastened directly against the hot tank causing condensation. 4. Cooling coils not below fluid level.
1. Water shut off or heat exchanged clogged.
2. Continuous operation at relief valve setting. a. Stalling over load etc.
b. Fluid viscosity too high.
3. Excessive slippage of internal leakage.
a. Check stall leakage past pump, motor and cylinders. b. Fluid viscosity too low.
4. Tank size too small. The tank should be sized to approximately three times the capacity of the pump. Allowance should be made when using large bore cylinders for the amount of oil required for cylinder extension and retraction. This also applies
where large number of small cylinders are in the circuit.
5. Inadequate baffling in the tank.
6. Pipe or hose ID too small causing high fluid velocities to be achieved. 7. Valves sized too small causing high fluid velocities to be achieved.
8. Lack of air circulation around the oil tank.
9. System valve set too high.
10. Ambient temperature around tank too high.