Hydraulics is a mature industry, so it’s not everyday that you see creative new products come along. So it was interesting to hear about the new Variable Volume Reservoir (VVR), a compact hydraulic reservoir created by Smart Reservoir, a Canadian company. Smart Reservoir says that it can replace conventional hydraulic reservoirs—it’s a simple improvement and it addresses weight, space, cost, safety, oil contamination and environmental issues.
The VVR is available in 1.8 or 3.6 gals capacities; the models weigh 36 and 67 lbs. respectively when full of oil. (The company says it is also working on a 6.6 gal version.) On selected applications, they can replace conventional hydraulic oil reservoirs that are 40 times larger. A VVR can be installed on new equipment or retrofitted to existing systems.
Being sealed (and slightly pressurized at 1-9 psig) and airless, the VVR dramatically reduces the ingestion of solid contaminants and oxidation-producing moisture—this would increase fluid life by up to 5 times that with conventional reservoirs. The VVR maintains a relatively constant pressure at pump inlets, supercharging the pumps and reducing the possibility of cavitation, whatever the altitude and angle of the reservoir. Unlike gas accumulators, the pressurization is generated mechanically by a spring and will not be affected by temperature or ambient pressure.
The company says that the VVR isn’t impacted by pump flow or system pressure. They’ve tested it on a system with a flow rate of 80 gpm using the 7 smaller sized reservoir with great success. A Hägglunds MB283 motor was powered for 6 weeks using 1.25 gal of hydraulic oil—as opposed to the 80-120 gal normally required, based on the pump flow of 40 gpm.
Fluid enters or leaves the VVR only when there is the need for compensation during cylinder motion and/or thermal changes. Otherwise, the returning flow goes directly to the pump inlet. Using the VVR is similar to having a hydrostatic, closed loop system except that the VVR can be used with multiple pumps and multiple actuators.
A simple manifold system is required when a VVR is used to feed multiple pumps. A collector manifold can be added for multiple drain lines returning to the VVR. VVRs can also be installed in parallel when needed for larger differential volumes.
The appropriate reservoir size for an application is determined by two factors: The total differential volume of the cylinders and the system fill volume—including the fluid required in motors, pump housings, cylinder heads, hoses, filters and coolers. This oil will expand by a maximum of 10% if temperature ranges between -22° to 257° F.
The company doesn’t recommend using the VVR when oil temperatures are below -13° F. For extreme low temperature uses, an oil pre-heating system that will bring the oil above -13° F should be used.
For more details, visit the company website at www.variablevolumereservoir.com.
