WEBTEC DHC 51 Operating Manual page 9

4.3 Control Valve. Cylinder 'TEE' Test
4.31 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.
4.32 Close tester loading valve slowly while recording pressures and flow rate.
4.33 Repeat 4.32 for power position, for all spools of all control valves.
4.331 If all components are in good operating condition, pressure and flow
measurements should be the same as in the pump test paragraph 3.0
4.332 If the decrease in the flow of any control valve position is noted, leakage is
indicated in this control valve or cylinder. See paragraph 4.4 for test routine
to determine which is at fault.
4.333 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 defective casting - but
always check the relief valve FIRST)
4.4 Additional test to locate fault in control valve or cylinder (see paragraph 4.332).
Disconnect line to cylinder and plug valve port.
4.41 Place control valve handle in position where greatest decrease of flow was
noted.
4.42 Close tester loading valve and record both pressure and flow.
4.43 If the SAME decrease in flow is noted as in test per paragraph 4.332 then the
control valve is at fault. HOWEVER, if the flow readings are now higher and
comparable to the other control valves, then a faulty cylinder is indicated.
5.0 DIRECTIONAL CONTROL VALVE 'IN-LINE' TEST (See drawing B.1) using DHT or DHC
5.01 To check the relief valve pressure setting where relief valves are integral with control
valve, install flow meter in the cylinder line as shown in drawing B1,ensuring that
loading valve is open (turn anti-clockwise). Start pump and operate the lever on the
valve in which the tester is situated to raise load. Slowly close the loading 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. Using bi-directional flow testers,
the cylinder and valve may be tested in the opposite direction by operating the lever
to retract the cylinder.
5.02 Control Valve Leakage
With flow meter installed as in 5.01, repeat test and compare flow readings obtained
for comparable pump test 3.3. 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.
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