What is a hydraulic double vane pump?

What is a hydraulic double vane pump, and how does its internal design differ from a single vane pump?

A hydraulic double vane pump is essentially two single vane pump cartridges assembled within a common housing and driven by a single shaft. Its primary distinction from a standard single vane pump lies in this dual-cartridge construction.

Internally, the pump contains two separate sets of key components operating in parallel: two rotors with sliding vanes, two elliptical cam rings (stators), and two sets of port plates. These two internal pumping chambers share a common drive shaft and housing. The fluid inlet and outlet ports for each chamber are often manifolded together internally, so the pump has a single suction port and a single pressure port on its exterior. However, the flow paths for the two chambers remain hydraulically separate until they merge at the common outlet. This design effectively doubles the fluid displacement per revolution compared to a single cartridge of the same size, or allows for a more compact pump to achieve a given flow rate.

What are the functional reasons for selecting a double vane pump over other types?

The selection of a double vane pump is typically based on two interrelated performance goals: achieving higher flow rates and reducing flow pulsation.

The direct reason is to increase flow output within spatial constraints. Instead of using one physically larger pump, which may not fit the available space or require a larger, more expensive prime mover, two smaller pump cartridges can be combined. This allows a higher total flow rate from a package that is often more compact in diameter than a single pump of equivalent displacement.

A secondary, important reason is to mitigate pressure and flow pulsation. In a single vane pump, the output flow has inherent ripples as each vane chamber transitions through its cycle. In a double vane pump, the two internal cam rings are often clocked or phased relative to each other. This means the discharge pulses from one chamber are timed to fill the troughs in the flow output from the other chamber. The result is a combined output with significantly smoother flow, bring about reduced pressure ripple, less vibration, and quieter operation in the hydraulic system.

What are common application areas for these pumps?

Double vane pumps are employed in industrial machinery where their specific output characteristics are beneficial. A primary application is in machine tool hydraulics, such as for the feed drives and clamping circuits of milling machines or lathes, where smooth, reliable flow is valued. They are also found in injection molding machines to provide the high, steady flow required for the plastication and injection phases. Furthermore, they are used in certain mobile hydraulic equipment and press circuits where space for a larger single pump is limited but higher flow is necessary for faster cylinder actuation.

What are important maintenance considerations specific to this design?

Maintenance considerations for double vane pumps share the general requirements of all vane pumps but are intensified due to the duplicated internal components. Fluid cleanliness is critically important, as contamination will simultaneously affect both pumping chambers, accelerating wear and potentially bring about failure. The pump has twice the number of critical wear surfaces—vane tips, cam rings, and port plates—compared to a single pump. Monitoring for a drop in volumetric efficiency (e.g., slower actuator speed) or increased noise can indicate wear in one or both chambers. While the chambers are independent, wear is often concurrent. Shaft alignment during installation is important, as misalignment can cause uneven load and premature failure on the bearings supporting the common shaft. Finally, understanding the internal porting configuration is necessary for correct system plumbing; some double pumps may be configured for separate outlet lines, while the standard design combines flow into a single outlet.

The hydraulic double vane pump is a design solution focused on delivering higher, smoother flow from a compact package. Its operation is based on two phased pumping chambers sharing a common drive. Its use is justified in applications prioritizing these flow characteristics, while its maintenance requires attention to fluid quality and the health of its dual internal assemblies.