WEBTEC DHT 2 Series User manual

Digital Hydraulic Testers
DHT Series 2
DHCR Series 2
Webtec Products Limited
Digital Hydraulic Testers Operating Manual
www.webtec.co.uk

1
Introduction
DH Series Digital Portable Hydraulic Testers have been designed for easy connection to a
hydraulic circuit so that flow, pressure and temperature can be readily checked. To facilitate
easy operation all common engineering units can be selected and the display update time can
be varied. Testers can take full back pressure up to 350/420 bar (depending on model) and the
built-in loading valve enables many of the operating conditions to be simulated. The tester can
be connected anywhere in the hydraulic system to test pumps motors, valves and cylinders in
both flow directions.
Bi-Directional Flow Testing
1. The loading valve gives smooth control of pressure in both flow directions and is protected
in both flow directions by two replaceable safety discs which are designed to rupture at
approximately 7 bar (100 psi) over the maximum working pressure. When these discs
rupture the oil by-passes the loading valve at low pressure and continues to flow freely
through the hydraulic system. A range of pressure safety discs are available to protect both
the tester and other components in the hydraulic system.
2. Although the bi-directional tester can be used in both flow directions, the preferred direction
is indicated by IN and OUT on the tester block. When the tester block is used for reverse
flow tests, slightly lower accuracies may be obtained depending on the oil viscosity, density
and compressibility.
3. The tester should be connected to the hydraulic circuit by means of flexible hoses, DHT
1 - 2 metre long and DHCR 1/4 metre long. The use of quick-disconnect couplings can save
time. Make sure the hoses are long enough so that the tester can be used conveniently on
the machine. The hoses and fittings at the inlet to the tester must be of adequate size for
the flow being tested. Elbows, rotary couplings etc., at the inlet and outlet ports of the tester
should be avoided to ensure accurate readings.
4. With the DHCR Testers connect the cable and micro-bore hose assembly at the readout
then connect to the flow block. IMPORTANT, after testing, disconnect at the flow block first
to avoid oil spillage.
5. On the DHT Testers the use of the flexible hoses will help to isolate the test unit from
vibration which often exists, DHCR Testers may be connected with rigid pipes.
6. After installing the Tester it is important to ensure that all connections are tightened and the
oil can flow freely throughout the hydraulic system BEFORE running the machine at full
speed. Check that the circuit is correctly connected and any shut-offvalves are opened,
also quick disconnect couplers MUST be open. IMPORTANT start the pump momentarily
to ensure there is no obstruction which could cause pressure build up.
7. When using the DHCR or an external flow block with the DHT Testers ensure that the
appropriate calibration factor is entered. See section on PROGRAMMING for details.
8. Testers have an automatic electronic system which shuts the power off after approximately
15 minutes should you forget. To reactivate the tester, press the “ON” KEY.

9. If using the LT5, LT10 or LT20 positive displacement flow blocks as remote input to
measure case drain leakage, it is recommended that a relief valve or check valve 1 bar (15
psi) is fitted in a tee to protect the pump or motor against excessive pressure in the event
of a surge flow. Consult Sales Office for further information on Tee fittings.
10. An additional gauge may be connected to the tester block using a pressure test point and
micro bore hose. See page 4 for details. Note: Always disconnect the low pressure gauge
for high pressure testing if it is not protected by an automatic cut-out valve.
Trouble Shooting with the Hydraulic Tester
PRELIMINARY: Check oil level in tank, pump drive, valve linkage for damaged parts, external
oil leaks etc
2
Excessive pump noise
fluctuating pressure
Low flow under no load
Decreasing performance
as pressure increases on
all circuits
On one circuit
Fails to hold load
Pump cavitation caused by:
a) Clogged suction filter
b) Restricted suction line
c) Air leak in pump suction line,
fittings, shaft seals etc.
d) Pump speed too high
Internal leakage in:
a) Pump
b) Main Relief Valve
c) Directional Control Valve
d) Cylinder or Hydraulic Motor
Directional Control Valve
Cross line Relief Valve
Cylinder
3.0; 4.1
3.0; 4.1
4.2; 4.3
4.2; 4.3; 4.4; 5.0
5.1; 5.2
4.2; 4.3; 4.4; 5.0
5.02
5.0; 5.2
Do not use with Water
The standard Webtec Hydraulic Testers are designed for use with mineral oil having reasonable
lubrication properties. They are not suitable for use with water or fluids with a high water
content. If a tester is used with water it should be flushed immediately after use with white or
methylated spirit or similar and then flushed with mineral oil to minimise any internal corrosion.
This may avoid an expensive repair. Damage to a tester from the use of a non-approved fluid
invalidates our normal warranty.
Problem Possible Cause Suggested Test,
See Paragraph:

3
Operation
Models: DHT and DHCR
Temperature
The thermistor type temperature transducer is in contact with the oil flow and temperature is
displayed on the left hand side of the digital display. Temperature from the internal transducer
is displayed in the INT and TACH position; temperature from a remote turbine is displayed in
the EXT position. Pressing the °C/°F button toggles the display between Centigrade and
Fahrenheit, the unit selected is indicated by a cursor arrow.
Flow Meter
The Flow Meter comprises an axial turbine mounted in an aluminium block. The oil flow rotates
the turbine and its speed is proportional to the oil velocity. The revolutions of the turbine are
measured by means of a magnetic sensing head which feeds a pulse every time a turbine blade
goes by,to an electric circuit. The circuit amplifies the pulse, shapes it into square wave form
and has a digital output which is directly proportional to the number of pulses per second.
Flowrate is displayed in the right hand side of the digital display when INT or EXT are selected.
Pressing the units button switches the display to USGPM, IGPM or LPM and the selection is
indicated by a cursor arrow. When the flow rate falls below the minimum allowable “L” is
indicated on the display. When flowrate exceeds the maximum “H” is indicated on the display.
Tachometer
RPM is displayed in the right hand side of the digital display when “TACH” is selected on the
rotary switch. Pressing the units button switches to RPM or RPM/N indication. RPM assumes
the sensor provides one pulse per revolution of the shaft. RPM/N assumes the sensor provides
Npulses each revolution of the shaft. (See section on Tacho Generator) The value of N can be
varied (See section on programming).
Pressure Gauge
The pressure gauge has a spiral Bourdon tube and the gauge case is filled with glycerine to
ensure good dampening on pulsating pressures. The gauge is connected to the turbine block
by fine bore capillary tube. Testers with BUILT-IN load valve have a shuttle valve which
automatically reads the highest pressure in both directions of flow. A gauge port is provided in
the block for the addition of a low pressure gauge.
Fast Button
The fast button changes the update time of the display. In some situations quick response to
flowrate changes is required. With the cursor arrow highlighting the fast position, the update
time is approximately 1/3 second. Otherwise the update time is approximately 1 second. When
using the fast update, the display will be less stable on flow and shaft speed.

4
Tach. Ext. Flow
Off
Tach.
Int. Flow
Ext. Flow
-
9V
+
!
-)-
Int. Flow
Fast OnUnits°C/°F
FLOW / RPM
TEMPERATURE
o
F
o
C
US
GPM
IMP
GPM
RPM
NRPM LPMFAST
ON Button
The unit is designed to turn off automatically after approximately 15 minutes to conserve power.
When this occurs user programmed values are retained in the memory. The unit is restarted by
pressing the “ON” button.
Bi-Directional Loading Valve
The reverse flow valve gives positive shut-off and pressure control in both directions of flow.
The loading valve has two easily replaceable safety discs located in the valve assembly which
internally protect the tester and machine in both flow directions.
Accessories
An infrared photo-tachometer is available along with a flexible magnetic base.
Low Pressure Gauge Kit comprises 63 mm 2 1/2” Glycerine filled 40 bar (600 psi) gauge with
automatic cut-out valve, pressure test point and 300 mm (12”) long micro bore hose. The test
point is fitted permanently into the tester block and the low pressure gauge can be connected
by hand without the need to stop the machine.
Adaptors.Fitting kits are available for all testers. Consult Sales Office.

5
Programming
Models DHT and DHCR
The DHT and specified DHCR Testers are pre-programmed with the calibration number (PPL)
as follows: INTERNAL meter factor to suit the tester turbine, EXTERNAL meter has a standard
calibration number and the actual calibration number from the turbine must be loaded into the
unit.
The DHCR unspecified Testers INTERNAL and EXTERNAL inputs, the calibration numbers
have not been loaded. Both inputs have the standard calibration numbers.
To program these values follow the procedure below:
PROGRAM MODE - EXT, INT and TACH.
External Flow - EXT
1.) Turn selector switch to Ext.Flow and press the ON button.
2.) Press °C/°F button and hold down. Then press ON i.e. two buttons are pressed at the
same time.
3.) On the left side of the display appears the turbine type number i.e. 750 is 750 lpm, on
the right side of the display is the standard calibration number. Use the FAST key to
browse through the list of turbine types. Press UNITS to select a turbine type.
4.) Use the FAST key to increment the number above the cursor. Press UNITS to move to
the next column. After entering the calibration factor press UNITS until the display
overflows. The display will now show the number of digits after the decimal point. Use
the FAST key to select the number of decimal places to appear on the display.
5.) Press the ON button to store the entries.
Internal Flow - INT
The calibration factor for internal flow on the DHT Testers is pre-programmed. It can be checked
as detailed above, but it is not possible to change it. The internal calibration factor on the DHCR
should be loaded by switching to INT and repeating the program instructions above.
TACH
The calibration factor for RPM is pre-programmed for a factor of 1.0. For the RPM/N function
the tachometer provides N pulses per revolution of the shaft.
To set factor N:
1.) Turn selector switch to TACH and press the ON button.
2.) Press °C/°F button and hold down. Then press ON i.e. two buttons are pressed at the
same time.
3.) The display shows the current value for “N”. Use the FAST key to increment the number
above the cursor. Press UNITS to move to the next column.
4.) Press the ON button to store the entries.

6
Instructions for using the portable Hydraulic Tester
Models - DHT and DHCR
0.0 The Tester is designed to measure flow, pressure, temperature and rpm. It can take full
system pressure up to 420 bar (depending on model) and measure flow in both directions
for motor and cylinder testing.
0.1 Make all tests at operating temperatures because as the oil temperature increases it
becomes thinner and any internal leakage becomes greater.
0.2 Testing will be easier and faster if quick disconnect couplers are used to attach the Test Unit.
0.3 There are two basic test ‘set-ups’ when using either the DHT or DHCR Testers:
A) The In Line test to check out pumps, entire systems and also monitoring operating
conditions.
B) The Tee Test to check out pumps, directional control valves and overall system
condition.
0.4 A preliminary check of the hydraulic system’s oil supply, 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 Installing the Test Unit
1.1 Connect the Tester to the circuit, see page 22 for Port Sizes. The inlet and outlet ports
are marked on the turbine block. Use hoses and fittings of sufficient diameter for the flow
being tested. Avoid restrictions at inlet and outlet ports of the Tester. Also avoid sharp
bends because at high pressure hoses will deflect and straighten under pressure.
1.2 When the pressure loading valve is used ensure it is fully opened by turning the knob
counter clockwise.
1.3 When no flow is passing through the turbine, the display will read “L” for “LOW” flow.
1.4 When low pressure testing is required connect the optional low pressure gauge with
quick disconnect coupler only after the pressure has first been checked on the high
pressure gauge. REMEMBER to disconnect the low pressure gauge for high pressure
tests otherwise the gauge will be damaged. Note: An automatic cut-out valve which
protects the LP gauge is available. Consult sales office.
1.5 With the DHCR Testers connect the cable and micro-bore hose assembly at the
readout then connect to the flow block. IMPORTANT after testing disconnect at the
flow block first to avoid oil spillage.
1.6 Connect the remote flow block to the circuit as specified above in 1.1 and 1.2.
1.7 Select “EXT” on switch and program in correct meter factor if not already present.
(see section on programming).
1.8 Continue tests as specified for the hydraulic tester.

2.0 Standard Test Conditions
2.1 Position the Hydraulic Test Unit as described in paragraph 3.0 or 4.0.
2.2 Open loading valve. (Rotate counter-clockwise) and select high flow range.
2.3 Start pump momentarily to ensure that oil flows freely through the hydraulic system,
then run pump at normal maximum speed. Do not change pump speed while using
the loading valve.
2.4 Slowly close Test Unit Loading Valve to develop desired pressure. Run the machine
until normal operating temperature is reached.
2.5 Open the Testing Loading Valve and proceed with required test procedure (see
paragraph 3.0 or 4.0).
2.6 Keep a record of flow readings at various operating pressures for comparison of test
results. The machine Manufacturer’s service manual should be consulted.
3.0 Test 1 - Pump In Line Test (See Test Diagram A1) using DHT or DHCR
3.1 Install the Tester into the system between the pump outlet port and the inlet to the
directional control valve.
3.2 Open Tester loading valve to read maximum pump flow at minimum pressure.
3.3 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.
7
Drawing A1
Directional Valve
Cylinder
Remote
Flow Block
Pump DHT Test Hose
Relief
Valve
US

3.4 Pump flow at rated pressure can now be checked against the pump manufacturer’s
specifications. The decrease in flow from the 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.
3.5 The tester 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 the circuit
elements, such as pump, control valve, cylinder and hydraulic motor.
4.0 Test B - ‘TEE’ Test (See Drawing A2) using DHT or DHCR
4.1 A ‘Tee’ must be installed at one point between the pump and control valve then
connected to the “IN” port of the Tester.The “OUT” port of the tester is connected
back to the tank. Make sure the loading valve is open. Note: Typically an elbow may
be changed to a ‘Tee’ in most hydraulic circuits and the ‘Tee’ can be capped with a
steel cap when not used for testing.
4.12 Pump Test. Disconnect and plug connection to control valve and proceed as in
paragraph 3.2; 3.3 and 3.4.
4.2 Overall System and Relief Valve Test (See drawing A2)
(For relief valve integral with directional control valves)
4.21 Connect control valve to ‘Tee’. Operate control valve to extend the cylinder to
end of stroke.
4.22 Close the Tester 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.
8
Drawing A2
Cylinder
Pump Tee Connection
Test Hose
Relief Valve
Overall System
‘Tee’ Test
DHT
US