The operating principle of a hydraulic pump is to transfer energy to a liquid to displace, evacuate or distribute it. There are many different pumping solutions. The choice of a hydraulic system depends on many factors. Let's take a closer look at the particularities of the different models of hydraulic pumps and all the elements to consider in order to make the right choice.
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The purpose of this operation is to put a liquid in motion in order to displace or pump it. This system uses mechanical energy to create hydraulic energy. Depending on the hydraulic station, it is the fluctuations in speed or pressure that drive the displacement of the fluid.
They use the mechanical energy of the impeller that is converted into hydraulic energy.
The liquid is sucked in by a toothed wheel with vanes or blades or a screw. Its speed drives the liquid to the discharge outlet. Here, it is the centrifugal force that enables the movement of the liquid.
Centrifugal pumps are very frequently used because they offer good hydraulic performance and high flow rates. However, it is important to point out that this type of pump is not designed to operate with highly viscous liquids.
These hydraulic pumps use variations in volume to put the fluid in motion. Contrary to centrifugal pumps, this type of pump is self-priming.
There is a very wide range of displacement pumps.
They operate via rectilinear displacement. Piston pumps and diaphragm pumps operate by cycles. The movement of the piston or diaphragm increases the volume of the pump body and creates a partial vacuum. The suction nozzle valve opens to allow the stored liquid to enter.
When the piston moves forward, the liquid is put under pressure. This pressure causes movement towards the discharge outlet. The cycle can begin again. Manual hydraulic pumps operate on this exact principle.
Their operating principle is the same except for one detail: it is the rotation that causes the liquid to move.
Although there are many models, the most common is the rotary gear pump. This hydraulic system consists of bearings and a rotor. Various seals ensure they are leakproof. Internal gear pumps possess, for example, two cogs that rotate in opposite directions.
Gear pumps are pumps with a fixed cylinder capacity that use variations in rotation speed to regulate their flow rate. The faster the gears turn, the higher the discharge flow.
Vane pumps are fitted with a rotor equipped with vanes or blades that rotate inside the pump casing. They are a type of variable cylinder pump. A manual or automatic flow regulator is installed on this type of pump. This variator enables very precise adjustment.
Viscosity and density are important elements to know in order to determine the most suitable pump. Indeed, the thicker the fluid, the greater its resistance to transfer.
The least viscous liquids are water, certain oils and alcohol. Although all hydraulic systems can be considered, centrifugal pumps are often chosen. Displacement pumps are chosen for denser and thicker fluids, like food products. They are also suitable for greases, paint and glue, even if these fluids are very thick at rest, their viscosity decreases when the rotation speed is constant.
The most common are gear pumps, which are the simplest and least expensive. They are suitable for many applications: with food products, including oils, fuel, lubricants, certain solvents, etc.
It is also important to consider the temperature of the pumped liquid and to determine whether the fluid is neutral or corrosive, contains particles or not. If it does contain particles, their size will determine the choice of the hydraulic equipment.
Generally speaking, we recommend you fully understand all the properties of the fluids used by consulting the safety data sheet (SDS). For use in an ATEX classified zone, it is obligatory to choose an ATEX pump.
It is essential to correctly measure and consider the elevation difference by measuring:
The length of the discharge and suction enables the length of the hoses to be determined. These elements also condition the choice of hose diameters.
This is usually given in litres per minute, l / min, but can also be expressed in gallons / minute or cubic centimetres / minute.
The flow rate corresponds to the quantity of fluid sucked in by the pump in a given time. To choose a pump that ensures a sufficient flow rate, it is essential to calculate the different yields.
The volumetric yield considers the loss of energy that a liquid undergoes when it is sucked into the pump. This leakage depends on the pressure and the temperature of the liquid sucked in. The hydraulic yield thus corresponds to the volume of liquid effectively sucked up in one minute.
It is important to choose a pump cylinder capacity that is greater than this yield. The cylinder capacity gives an indication of the capacity of the pump. It indicates the volume of liquid that it can pump in one revolution. It is expressed in cm3 / revolution. The mechanical yield corresponds to the friction inside the pump.
Certain additional parts are added on to meet the requirements for use: valve, elbow, delivery gun, meter, reel, etc.
To monitor the flow rate, it can be equipped with a pressure gauge, a flow regulator, etc. In case of wear, it is possible to find spare parts to repair the hydraulic systems of your pumps.
To find the most suitable hydraulic system, it is necessary to properly define the pumped product, your needs and the required flow rate. To obtain personalised advice and to inform us of your needs... These elements enable us to calculate the loss of load and to define the most suitable pump for you. Contact us by telephone on +33 (0) 3 81 96 16 47 or via our contact form.