Hydraulics, the recently trending industry that makes use of flowing high-pressure fluids. So, there may be certain hydraulic applications that need to measure the volume of fluid passes through a certain point at any particular time. This can be a part of troubleshooting, performance monitoring, comparison, etc.. But, how does this volume calculated in a hydraulic system?

It is a hydraulic flow meter that is used for measuring linear, nonlinear, mass or volumetric flow rate of a liquid. Flow meters are also known as flow gauge, flow indicator, and liquid meter based on the industry they are used with. Commonly the flow meters are constructed with brass, aluminium or stainless steel material. Flow meters constructed with aluminium are used for measuring the flow of noncorrosive water-based or petroleum-based fluids with a pressure up to 3500 PSI. Water monitoring applications or systems without corrosion inhibitors use brass flow meters and the stainless steel flow meters are used with corrosive caustic fluids with a pressure up to 6000 PSI.

How to use a hydraulic flow meter?

A flow meter can be placed in any location of the hydraulic line to detect the flow rate. Flow meters with variable port sizes are available that are suitable for different hydraulic systems. When the hydraulic system operates, the fluid is passed towards the flow meter. A flow meter mainly contains 3 parts; the primary device, a transducer and a transmitter. The transducer senses the hydraulic fluid passing through the primary device and a usable flow signal is generated by the transmitter when the sensed signal is sent by the transducer. The volume is calculated based on the principle that the volume of fluid passing is directly proportional to the cross-sectional area and the fluid velocity. Also, the mass flow is directly proportional to fluid density and volume. Then, this calculated hydraulic measurement is displayed on the hydraulic flow meter gauge. All standard hydraulic oil flow meters supports unidirectional flow. But, reverse flow by-pass options are also available with some selected flow meters.

Selecting a hydraulic flow meter is a difficult procedure. A wrong selection will cause errors in the diagnosed result. The factors that need to be considered while selecting a hydraulic flow meter are; the hydraulic fluid properties, operating condition of the hydraulic system, the need for measuring flow, the level of accuracy required, the effect of fluid on flow meter and vice-versa, and finally the budget.

Also, Read: Functions of Hydraulic Fluid

Hydraulic Flow Meter Types

Variable orifice flow meter

A variable orifice flow meter is the commonly used head type flow measuring device, where the orifice plate inserted in the pipeline.  The basic idea behind the variable orifice flow meter is the flow displacing object like the piston or ring. The piston is held by a spring and a force is exerted on the piston as a result of fluid momentum. Along with the increase in flow, the piston will move and the size of the orifice will increase. The flow is indicated on the analogue readout via the magnet linked to the piston.

Gear type flow meter

Gear type flow meters are positive displacement flow meters that look similar to a gear-type motor. This flow meter has a pair of intermeshed rotating gears and fluid passes around the outside of these gears. A transducer is connected with one of the gears and it will generate a pulse if the other gear passes under it. The rotation of these gears will depend on the fluid flow. That is, the gears will rotate faster if there is a high fluid flow and vice-versa. This flow meter can be noisy but have a very high accuracy level.

Turbine-type flow meter

The turbine-type flow meter is a volume sensing device that is constructed with a turbine rotor and blades. The turbine rotor is connected to a shaft and is placed between two sets of flow straighteners. When the fluid passes, the turbine blade rotates and the transducer located on the turbine rotor generates a pulse by sensing the rotation of these blades. This is a reliable and accurate flow meter for liquids and gases.