Slow or weak hydraulic operation can be caused by insufficient flow, inadequate pressure, internal leakage, a restriction in the circuit or a problem with an individual component.

Measuring flow, pressure and oil temperature while the system is operating helps narrow down the possible cause. A hydraulic tester can first be used to check the pump output and then connected at other points in the circuit to investigate valves, motors, cylinders or steering systems

A hydraulic pump should be tested by measuring its flow while gradually increasing the pressure against it. The measured flow at different pressures can then be compared with the pump or machine manufacturer’s expected performance figures. This test measures the pump’s volumetric efficiency and is also called a PQ test. Volumetric efficiency can provide a good indication of hydraulic pump health.

The RFIK combines a flow indicator, pressure gauge, thermometer and loading valve, allowing the pump to be tested under a controlled load with one self-contained instrument.

Yes. A pressure reading alone does not confirm that a pump is delivering sufficient flow.

A worn pump may still reach the expected pressure in some conditions but deliver less flow as the load increases. Measuring flow and pressure together provides a more useful indication of pump performance than relying on pressure alone

The three most useful measurements are generally:

• Flow, which shows how much oil is moving through the circuit 
• Pressure, which indicates the load or resistance within the system 
• Oil temperature, which helps account for changes in viscosity and operating conditions 

The RFIK displays all three measurements directly using mechanical dials and a built-in thermometer

Begin by testing the pump output under controlled conditions. If the pump is providing the expected flow at the required pressure, testing can then move further through the circuit.

Comparing measurements at different points can help isolate the section in which performance is being lost. The RFIK is designed for performance testing of pumps, motors, valves, steering systems, cylinders and complete hydraulic circuits.

A hydraulic tester does not automatically identify the defective component, but it provides the measurements needed to make a more informed diagnosis.

A loading valve creates a controlled restriction in the hydraulic circuit. Gradually closing the valve increases system pressure, allowing flow to be observed at different load conditions.

The RFIK loading valve is designed to provide smooth and progressive control of system pressure up to the tester’s rated limit of 420 bar. Testing should always remain within the rated pressure of the tester, hoses, fittings and machine being tested.

Hydraulic oil viscosity changes with temperature. This can affect internal leakage, pressure loss, component efficiency and the results recorded during a test.

Recording temperature alongside flow and pressure helps ensure that results are compared under similar operating conditions. The RFIK includes a thermometer positioned in the flow block close to the passing fluid.

Yes. A mechanical hydraulic tester can be useful for field servicing where batteries, charging facilities or an external power supply may not be available.

The RFIK is fully mechanical and self-contained. Its flow, pressure and temperature readings are displayed directly, so it requires no batteries or electrical connection. This makes it suitable for servicing agricultural and other mobile machinery away from a workshop.

The correct test point depends on the component or section of the circuit being investigated. The RFIK can be temporarily connected into either the pressure line or the return line.

Webtec recommends connecting it using flexible hoses at least 500 mm, or 1.5 ft, in length. The tester is intended for temporary diagnostic and commissioning work and is not designed for permanent installation.

The overall system test diagram on page 4 of the datasheet shows the tester connected between the pump and the rest of the machine circuit.

Choose a tester with a calibrated range that covers the maximum flow expected from the machine. Avoid selecting a range that is unnecessarily high, because flow accuracy is stated as a percentage of the instrument’s full scale.

The RFIK Series is available in the following calibrated ranges:

• 2–30 L/min
• 5–60 L/min
• 10–120 L/min
• 10–200 L/min
• 20–270 L/min

Equivalent US gallon ranges are available from 0.5–8 US gpm up to 5–70 US gpm. 

The required capacity depends on the machine being tested. The largest RFIK model is rated for flows up to 270 L/min, or 70 US gpm, and the Series has a maximum rated pressure of up to 420 bar. For flows greater than this, Webtec manufactures portable hydraulic testers rated up to 1500 L/min.

Lower-flow versions are available for systems where a smaller calibrated range provides a more appropriate measurement scale.

This depends on whether the tester is designed to permit reverse flow and whether it can also measure it.

The RFIK allows oil to pass through the instrument in the reverse direction, but it does not measure reverse flow. When the flow direction is reversed, the flow indicator needle will show zero. The loading valve can provide progressive pressure loading in either direction. If you need to measure flow in both directions, Webtec manufactures bi-directional hydraulic testers.

The RFIK incorporates Webtec’s Interpass® safety protection system. Replaceable safety burst discs operate if the maximum pressure is exceeded, allowing oil to bypass internally and relieving flow towards the return line.

This protection operates in either flow direction, and replacement safety discs are supplied with the tester. It is still essential to observe the pressure ratings of the complete test circuit.

Any instrument installed directly in a hydraulic line will introduce some resistance to flow. The amount of pressure drop depends on the tester model, the flow rate and the fluid conditions.

Page 3 of the RFIK datasheet provides separate pressure-drop curves for each flow range with the loading valve fully open. The tests were completed using ISO 32 mineral oil at 40°C with a viscosity of 32 cSt.