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. Engineering
units are factory preset. Testers can take full back pressure up to 350/420 bar (depending on
model) and the built-in loading (optional on DHC) 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 (where fitted) 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 1 - 2
metres 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.
5. The use of the flexible hoses will help to isolate the test unit from vibration which often
exists.
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-off valves 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.
8. Testers have an automatic electronic system which shuts the power off after approximately
20 mins on the DHT and 1 hour on the DHC. To reactivate the tester, switch it “OFF” and
the “ON” again.
9. If the display does not return, it may be necessary to replace the battery.
