Mobile machinery, compact power units, and dual-circuit systems. Dual (or tandem) gear pumps are a type of pump of interest. Specialized versions of these gear pumps offer significant advantages in applications requiring two hydraulic circuits or flow paths.
What Is a Double Gear Pump?
Definition & Terminology
A double gear pump-also commonly referred to as a tandem gear pump or dual gear pump-is a type of hydraulic positive-displacement pump where two gear-pump sections are integrated into a single housing and share a common drive shaft. Each section typically has its own sets of gears and its own outlet port; in some designs they may share or isolate the suction (inlet) port.
Basic Structure
Key structural components of a double gear pump include:
- Common drive shaft: The input shaft drives both gear sets simultaneously.
- Two gear-pump modules: Each section consists of gears (external or internal), bearings, housing segments, etc. They may be the same size (displacement) or different, depending on the design.
- Intermediate partition or isolation plate: A structural component that separates the two sections within the housing, sometimes incorporating seals or plates to prevent leakage between the two modules.
- Inlet and outlet ports: Often, there is a single inlet for both sections (shared suction) and two separate outlet ports (one per section); in other configurations, there may be dual inlets for full independence.
Comparison to Single Gear Pump
To appreciate the distinction, it helps to contrast a standard single gear pump with the double/tandem variant:
- A single gear pump has one set of meshing gears, one pump housing, one inlet and one outlet. It delivers one flow circuit. The flow is proportional to the shaft speed and the pump displacement.
- A double gear pump, by contrast, delivers two flows or two circuits (via two gear‐sets) from one drive. This allows one drive source to power dual hydraulic functions while saving on separate pump units, space, and potentially cost.
- Because the twin sections are housed in one unit and driven together, the design must ensure that gear clearances, alignment, and partition integrity are all maintained - making the manufacturing quality more critical.
How It Works – Working Principle
Basic positive‐displacement gear pump recap
Before diving into the dual‐section version, it's helpful to recap how a standard gear pump works, because the tandem version builds on the same principle.
A gear pump is a positive‐displacement pump: for each revolution of the drive, a fixed volume of fluid is moved (neglecting leakage).
Typical operation:
- On the inlet side, the meshing gears separate and create a vacuum that draws fluid in.
- The fluid is carried in the spaces between the gear teeth and the casing/housing, around from the inlet to the outlet.
- On the discharge side, the gears mesh again and the fluid is forced out through the outlet port. Tight gear/casing clearances prevent back-leakage and maintain volumetric efficiency.
- Because flow is proportional to shaft speed × displacement, gear pumps offer predictable flows and are widely used in hydraulic power applications.
Working principle of the double (tandem) gear pump
Now - how the double gear pump expands on the above:
- In a tandem gear pump, two (or more) gear‐pump modules (sections) are mounted on a common drive shaft inside a shared housing. Each section has its gear set, and typically has its own outlet port.
- The inlet (suction) side may be shared (one common suction port) or may be separate depending on design, but many designs share the suction for both modules.
As the shaft rotates:
- Both gear sets operate simultaneously, creating vacuum(s) at their inlet(s) and drawing fluid into each section. For example, as each gear pair un-meshes at the suction side, fluid is drawn in.
- The fluid is carried around the gear teeth/casing by each section's gear set. Because of the fixed displacement nature, each section moves a predictable volume per revolution. For different displacements, sections may be sized differently.
- The fluid exits each section via its outlet port: the meshing gears force the fluid out. Because there are two sections, you get two independent flows. These flows could be combined downstream, or directed to separate circuits (one section for circuit A, one for circuit B).
Key Features & Advantages
| Feature | Description | Benefit to Hydraulic Systems / OEMs |
|---|---|---|
| Compact design | Two gear-pump sections integrated into one housing with a common drive shaft. | Saves installation space, simplifies layout and is ideal for mobile/compact hydraulic units. |
| Dual-output flexibility | Each section can deliver independent flows or pressures (or both) from one unit. | Enables multi-circuit systems (e.g., one high-flow circuit + one low-flow circuit) without needing two separate pumps. |
| Simplified drive & plumbing | One drive shaft, fewer couplings, possibly shared suction port. | Reduces system complexity, fewer components, lower installation cost and fewer potential failure points. |
| Predictable flow behavior | As a positive-displacement gear design, flow is proportional to shaft speed and displacement. | Easier to size, control and integrate into hydraulic system designs with known flows. |
| Cost-effectiveness for dual-circuit applications | Fewer units, shared components and streamlined design for systems requiring two outputs. | Reduces hardware cost, installation labour, and possibly lowers maintenance overhead. |
Applications of a Double Gear Pump
Application Areas
Mobile hydraulics (construction & earth-moving)
Machines such as excavators, bulldozers and loaders often require two hydraulic circuits operating simultaneously: e.g., one circuit for the boom/lift function and another for auxiliary tool or swing function. A tandem gear pump allows a single drive to feed both circuits, saving space and complexity.
Compact hydraulic power units (HPUs)
In situations with limited installation space (mobile cranes, skid-mount units, integrated manifolds), using one pump housing with two sections is more compact than two separate pumps. It simplifies layout and reduces component count.
Dual-circuit systems requiring different flows or pressures
When an application demands, for example, one high-flow/low-pressure output and another low-flow/high-pressure output, a tandem gear pump enables exactly that - two distinct circuits driven by one shaft.
Industrial machines and tooling with lubrication + power requirements
Some manufacturing equipment uses one section for machine tool hydraulics and another for lubrication or auxiliary circuits - again benefitting from the dual-section design.
Manufacturer Recommendation & Product Introduction
Why choose Poocca's double gear pumps
- Poocca is a comprehensive hydraulic service enterprise with R&D, manufacturing, maintenance and sales capabilities, founded in 2006 in Shenzhen, China.
- Their tandem gear pump line is explicitly described as "double pumps, triple pumps and four-stage pumps … if the multi-pump you need does not appear in our multi-pump, please contact us."
- Key features: nominal pressure up to approximately 250 bar, with robust bearings and reinforced drive / cover materials for heavy-duty use.
- Poocca offers customization: different displacement combinations, different section sizes and configurations, to match dual-circuit requirements.
- Their published guidance on selecting a dual gear pump emphasises flow & pressure matching, material / structure selection and maintenance best practices.
How Poocca's tandem gear pump fits your application
Dual-flow requirement: If your machine needs two simultaneous circuits (e.g., primary lift + auxiliary tool), Poocca's double gear pump allows using one drive unit for both flows, reducing installation footprint.
Different displacement combinations: Poocca offers combinations like Section A (20 cc) + Section B (50 cc) in one housing, enabling custom flow splits.
High pressure capability: Many Poocca tandem gear pumps have nominal 230-250 bar pressure ratings, and intermittent peaks up to ~280 bar.
Customization/OEM support: Because Poocca offers OEM/ODM services, you can match flange, shaft, port configuration, installation, and displacement to your customer's system.
Frequently Asked Questions (FAQs)
What is the difference between a double gear pump and a conventional single gear pump?
A double (tandem) gear pump has two gear-pump modules in one housing with a shared drive shaft, enabling two independent output flows or circuits. A conventional single gear pump has only one module and delivers one flow path.
Can both sections of a double gear pump operate at the same pressure?
Yes - in many designs both sections can be rated for the same pressure. However, if one section is sized differently or directed to a different circuit, they may operate at different pressures depending on system design.
Is it possible to shut off one section of the double gear pump while the other continues to operate?
It depends on the design. While the drive continues rotating both modules, one section may be isolated by valves or throttled. But because the pump shares a housing and drive, you must verify that isolation won't cause cross-leakage or drive torque issues.
What are the key installation or maintenance concerns specific to a double gear pump?
Important considerations include: ensuring adequate suction/inlet for both modules, correct mounting and shaft alignment, ensuring internal partition/seals between modules prevent cross-leakage, monitoring wear in both sections (since shared drive means one failure affects entire unit).
When should I choose a double gear pump over two separate single gear pumps?
Choose a double gear pump when your system requires two hydraulic circuits (with different flows/pressures) but installation space, plumbing simplicity, and cost efficiency matter. If only one circuit is needed or very different drives/mountings are required, two separate pumps may be preferable.
