A digital hydraulic tester can be used to measure the main operating conditions in a hydraulic circuit. The Webtec DHT Series measures flow and temperature on a digital display, while hydraulic pressure is indicated by a glycerine-filled pressure gauge.

The tester also has an integrated loading valve, allowing pressure to be progressively increased while the system is being tested. This makes it suitable for checking hydraulic system performance during servicing, commissioning and maintenance

A hydraulic pump can be tested under load by using a tester with a built-in loading valve. The Webtec DHT allows the operator to progressively increase pressure to simulate the working pressure experienced during normal machine operation, while observing hydraulic flow and pressure.

This allows the performance of the pump and hydraulic circuit to be checked under realistic operating conditions rather than measuring unrestricted flow alone

Yes. The Webtec DHT Series is designed to support performance testing of hydraulic pumps, motors, valves and hydrostatic transmissions.

By measuring flow, pressure and temperature while the hydraulic circuit is operating, a service engineer can gather the information needed for reactive fault finding as well as proactive and preventative maintenance. The built-in loading valve also allows system performance to be observed as hydraulic pressure is progressively increased

Yes. The DHT Series is designed not only for hydraulic maintenance but also for setting up hydraulic attachments such as hammers and breakers.

The tester can be connected into the hydraulic circuit so that flow, pressure and temperature can be checked while the system is operating. Its loading valve can also be used to simulate working pressure, helping the engineer verify hydraulic conditions before or during attachment setup

Yes. The Webtec DHT is a bi-directional hydraulic tester and is designed to measure flow accurately in either direction.

Its turbine flow block contains built-in flow straighteners that reduce turbulence and allow accurate flow measurement in both directions. This gives greater flexibility when connecting the tester into a hydraulic circuit and avoids the forward-flow-only measurement limitation found on some types of hydraulic test equipment.

No. On the Webtec DHT Series, flow and temperature are shown on the digital LCD, while pressure is measured using a glycerine-filled pressure gauge.

This is an important distinction between the DHT and Webtec’s more advanced DHM Digital Hydraulic Multimeter, which digitally measures and displays flow, pressure and temperature. The DHT is therefore suited to applications where straightforward live hydraulic measurements and load testing are required without the DHM’s additional digital diagnostic and reporting features.

Both ranges measure hydraulic flow, pressure and temperature and include an integrated loading valve with Interpass® protection, but their measurement and diagnostic capabilities differ.

The DHT digitally displays flow and temperature and uses a glycerine gauge for pressure. The DHM digitally measures flow, pressure and temperature and adds features including peak-pressure capture, hydraulic power, volumetric efficiency, TrueFlow® flow-direction indication, data recording and Bluetooth communication with the QuickCert®+ App for remote viewing and test-certificate creation.

The appropriate tester therefore depends on the measurements and level of diagnostic information required. 

The DHT Series covers hydraulic flow rates of up to 800 L/min / 210 US gpm and pressures of up to 480 bar / 7,000 psi, depending on the model.

The DHT03 models have a calibrated flow range of 8–300 L/min / 2–80 US gpm and are rated to 420 bar / 6,000 psi. DHT04 models cover 10–400 L/min / 2.5–105 US gpm at up to 420 bar / 6,000 psi, while DHT08 models cover 20–800 L/min / 5–210 US gpm and are rated to a maximum of 480 bar / 7,000 psi. The exact model should therefore be selected to suit both the required flow range and system pressure.

Yes. The DHT08 models have limited pressure control when operating below 86 L/min / 23 US gpm.

Within this low-flow region, the datasheet specifies the maximum controllable pressure in bar as:
Maximum pressure = 5 × flow in L/min + 30

This limitation is separate from the DHT08’s maximum rated pressure of 480 bar / 7,000 psi and should be taken into account when selecting the tester for low-flow, high-pressure applications

The Webtec DHT Series has a specified hydraulic fluid temperature range of -10 to 125 °C / 14 to 257 °F. Its specified ambient operating temperature range is -10 to 50 °C / 14 to 122 °F.

The tester also incorporates a red LED operational warning if the electronics exceed their maximum working temperature. This provides an indication to the operator when testing hydraulic fluids at elevated temperatures.

The DHT Series is specified for use with mineral hydraulic oils to ISO 11158.

The flow block is manufactured from high-tensile aluminium and uses FKM seals. Where a different hydraulic fluid is required, the DHT datasheet advises consulting Webtec technical sales rather than assuming compatibility.

Webtec recommends connecting the DHT flow block using flexible hoses approximately 1–2 metres / 3–6 ft long.

The inlet and outlet hoses should have a similar bore size to the flow block connections to avoid restrictions that could affect the test conditions. Where pressure pulsations cause the hoses or pipework to move repeatedly at the tester connections, the hoses should be firmly clamped to reduce movement and strain on the ports.

The hydraulic system cleanliness should be better than DIN ISO 4406: 21/19/16 or NAS 10 when using the Webtec DHT Series.

The datasheet states that this is typically achieved using filtration in the 20–25 micron range. Maintaining the specified level of filtration helps protect the turbine flow-measuring components and supports reliable operation of the hydraulic tester.

The DHT’s integrated loading valve incorporates Webtec’s Interpass® safety protection system.

Replaceable safety burst discs operate if the maximum pressure is exceeded, relieving hydraulic flow to the return line. The replacement burst discs are stored in an internal holder machined into the rear of the flow block. Interpass® therefore provides a defined over-pressure protection mechanism while the loading valve is being used to progressively load the hydraulic circuit.

The Webtec DHT Series is IP65 rated and is described as being sealed against dust and water jets.

The tester is also designed as a portable and robust diagnostic instrument for service and maintenance work. All DHT testers are supplied with a five-year manufacturer’s warranty as standard. As with any hydraulic test equipment, it should still be used within the environmental and operating limits given in the product documentation.

Webtec recommends a 12-month period between services, with a maximum interval of 36 months for the DHT Series.

Each tester is supplied with a calibration certificate and is calibrated using ISO32 mineral hydraulic oil at a mean viscosity of 21 cSt. The DHT also displays a service reminder when it is powered on to help users keep track of servicing. The datasheet notes that accuracy can be affected by factors including the operating cycle, fluid condition and extended periods between services.

The DHT Series specifies flow accuracy of ±1% of full scale, pressure accuracy of ±1.6% of full scale and temperature accuracy of ±1 °C / ±2 °F.

When selecting a tester, it is also important to choose a calibrated flow range that suits the hydraulic system being tested. The DHT range includes models covering 8–300 L/min / 2–80 US gpm, 10–400 L/min / 2.5–105 US gpm and 20–800 L/min / 5–210 US gpm, so the appropriate measurement range depends on the application.