First patented in the 1870s, vane pumps have a long and significant history in hydraulic systems. However, their usage has tailed off somewhat in recent years, in favour of gear and piston pumps. It may seem that hydraulic vane pumps have had their day. However, they are still valuable for specific applications and shouldn’t yet be written off.
What Are Hydraulic Vane Pumps?
Vane pumps are positive-displacement pumps used to produce the pressure and flow needed to operate hydraulic systems. At its simplest, a vane pump consists of two or more ‘vanes’ attached to a rotor, turning within a larger cylindrical cavity. The vanes are tensioned to maintain contact with the inside of the cylinder as the inner rotor revolves. The offset centre of the inner rotor creates vane cavities that produce the requisite flow, drawing in and expelling hydraulic fluid.
Since its initial invention, the vane pump has seen several improvements. Early pumps were limited in terms of operating pressure and fluid viscosity. While moderate pressure would produce an effective seal for the pump against the cam ring, higher pressures tended to cause excess friction and wear, and eventual failure. This meant that, in their early decades at least, vane pumps were limited to low pressure applications.
How Are Vane Pumps Used?
While earlier iterations of vane pumps were limited to around 2000psi, the introduction of pressure compensators allowed the cam ring itself to move, lowering pump displacement and raising pressure tolerance. Pressure-compensated vane pumps went on to dominate industry for much of the twentieth century. They have been very effective for devices like jaws and clamps, valued for their low noise and efficiency.
More recent technological improvements in vane pumps have included tighter tolerance and pitched vane angles, giving them higher durability. Hardened steel construction has also improved performance and usage range, by allowing them to operate with pressures over 5000psi.
However, as precision engineering has developed, even these improvements have not been enough for vane pumps to keep up with the demands of high pressure, low flow devices used for many modern applications, such as precise CNC machine cutting tools, injection moulding or wind energy applications. For these applications, radial piston pumps are typically favoured. Meanwhile, for low pressure applications, gear pumps are a cheaper option.
Are Vane Pumps Relevant In Modern Hydraulic System Design?
While once dominant, vane pumps now appear marginalised by design engineers. Caught between cheaper gear pumps and higher performance piston pumps, they seem not to offer much for the future. That said, there are still values to the venerable vane pump that should not be overlooked.
Vane pumps are still widely used as the default option in many low pressure CNC machine tool applications. The relative quietness and efficiency of vane pumps also makes them suited more widely to low or mid pressure devices in catering applications like soft-drinks dispensers and coffee machines. What’s more, provided pressures do not exceed 5000psi, vane pumps offer better resistance against contamination than piston pumps, as well as being quieter and cheaper. And innovations in vane pumps have not ceased. Recent innovations in closed-circuit pumps have allowed more precise control of output pressure and greater efficiency, meaning there is life in these pumps yet.
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