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Sunday, November 2, 2014

Flow and Pressure testing of Hydraulic Circuits

A few years ago we were asked by one of our clients  "Do you do Flow Testing?"
We said "not yet, but we will investigate and get back to you". 
We called our specialist hydraulics suppliers looking for a Hydraulic flow test kit and we were astounded at the prices of flow test kits.
Starting from $4400 and you still needed to supply your own hoses and adaptors to connect to the hydraulic circuit you wanted to test. So flow testing went on the back burner for a while.
Eventually with more and more clients requesting flow testing services we borrowed a flow tester from one of our trusted advisers, Charlie Gray.
Charlie had built his own from bits and pieces laying around his hydraulics workshop and had then mounted it all into an empty Bosch drill case.
The seed was planted and we then took Charlie's Idea a few steps further and designed and assembled our own flow test kit with the following capabilities. 
  • Measure Oil Flows up to 120 litres per minute or (32 gallons/Min).
  • Induce Pressures up to 350 Bar (5150 PSI) 
  • Measure Oil Tempetatures up to 110 Degrees Celsius.
Supplied with two 1.5 meter long  3/4" High Pressure Hoses  and a selection of 28 adaptors allows the user of this kit to virtually connect to any BSP, JIC or SAE Flanged equipment.

We have sold this Flow Test Kit (see picture below) all over Australia. 
Our Price as you see it Under $2000 inclusive of GST.

A flow test is the quickest and least invasive way to quickly check for internal leakage of a suspected component in a hydraulic circuit be it a valve, motor or pump.
A flow test can also be used to ascertain if the engine or motor powering the hydraulic system is in good condition and or even capable of powering the hydraulic system's requirements. 
Hydraulic pumps, directional control valves, relief valves and cylinders in a hydraulic circuit can be individually checked for internal leakage.
Principle of operation,
The flow test kit is added into the hydraulic circuit and is connected as close as possible before or after the suspected component.
Using a relatively easy process of recorded measurements, logic and simple elimination each component can be individually tested and results compared to the performance of the rest of the hydraulic circuit.

The process described below is used for testing a hydraulic pump. 
The flow test kit is installed as close as possible to the pump's pressure port.
The pump is started and allowed to free flow without load. Flow, and temperature are recorded at free flow.
The flow control valve is then slowly closed to induce a resistance to flow and any changes to flow, pressure and temperature are recorded (usually at 20 Bar or 250 PSI intervals) this test is usually carried out up to the pump's maximum manufacturers recommended pressure. 
Results are then compared to manufacturer's data to ascertain any loss in performance. 
As a rule: If a pump at 0 Bar pressure flows 100 Litres Per Min
and flows 75 litres per Minute at 210 bar or 3000 PSI Pressure (75%) it is considered OK.  


  1. That is why it is so important to keep up with mobile hydraulic repairs. I am glad to see that there are so many tools available to fix these issues. I'm going to go in for a flow test myself just to make sure everything is running smoothly. http://www.southernhydraulics.net.au/services

  2. The flow of fluids has to be measured and accounted for by use of a highly dependable method. Otherwise, water companies would not know how many gallons of water were being dispensed in a certain period of time, manufacturing plants could not control the flow of liquid materials and one could not measure the flow of clean medium to high-speed liquids and gases.

    Hydraulic Flowmeter