CBTL-*4/*4 Type Tandem Gear Pumps

Shijiazhuang Laiye Import& Export Trading Co., Ltd. is one of the leading manufacturers and suppliers of cbtl-*4/*4 type tandem gear pumps in China, also supports customized service. If you're going to wholesale high quality cbtl-*4/*4 type tandem gear pumps made in China, welcome to get pricelist from our factory.

When engineers design hydraulic systems for 5-ton loaders, large agricultural tractors, and other heavy-duty mobile equipment, one challenge appears again and again: the machine has only a single PTO or pump drive, yet it needs to power two independent hydraulic circuits with different flow demands. One circuit may be responsible for high-load lifting operations, while the other must maintain smooth steering, pilot control, or auxiliary functions without interruption.

A common approach is to connect two separate pumps through an intermediate adapter. Although this method can achieve the required flow output, it also increases the overall drivetrain length and creates additional concerns, including shaft alignment, installation space, and long-term reliability under vibration and heavy working conditions.

The CBTL-*4/*4 series was developed to solve these practical challenges. Rather than simply combining two standard pumps, we designed a fully integrated tandem gear pump that brings both hydraulic circuits into one compact and robust assembly.

The series adopts a unique dual-module structure: the front pump uses a gear profile of m=4, while the rear pump utilizes a larger m=5 gear profile. This engineering approach enables flexible mixed-displacement combinations, such as a 30 mL/r front stage paired with a 10 mL/r rear stage, delivering the right flow where each circuit needs it most.

By integrating both stages into a single aluminum housing, the CBTL-*4/*4 achieves a shorter installation length, improved structural rigidity, and easier mounting directly to the engine block. No oversized support brackets or complex alignment adjustments are required. The result is a cleaner hydraulic layout, reduced installation difficulty, and a more reliable power solution built for demanding mobile machinery applications.

Internal functioning

Because both pump stages are driven by the same through-shaft, they rotate at the same speed while maintaining fully independent hydraulic circuits. Each stage has its own suction and pressure ports, allowing separate oil intake and output without internal interference. This design delivers two independent hydraulic flows from a single mechanical drive, ensuring that heavy operation in one circuit will not affect the performance of the other, providing stable and reliable power for demanding applications such as loaders, agricultural machinery, and industrial equipment.

Durability
We integrated three specific internal features to make this design durable. First, the axial clearance floating offset automatically adjusts for mechanical wear in both the m=4 and m=5 gear sets. It keeps the internal leakage rate low as the pump ages. Second, the pump includes a radial balance channel. Because a tandem pump is longer than a single stage, the bearings bear more bending stress. This channel diverts side-load pressure away from the shaft, which helps maintain alignment under high torque. Third, we use DU self-lubricating bearings in high-friction areas. These support reliable operation during cold starts when the oil is thick and flow is slow.

Built to eliminate the need for external flow dividers in complex machinery, the CBTL-*4/*4 Type Tandem Gear Pumps deliver the exact flow split required for primary and auxiliary hydraulic circuits. This integrated design reduces potential leak points and simplifies system schematics.

Two pressure ranges based on the task
Not all hydraulic applications need 20 MPa continuous operation. Running a high-pressure pump on a light-duty circuit wastes energy and creates unnecessary heat. We split the CBTL-*4/*4 series into two pressure groups based on the displacement combination selected. The F/F-rated models hold a continuous rating of 20 MPa. We reserve these for heavy lifting, digging, and other demanding functions. The E/E-rated models are rated for 16 MPa continuous. This approach allows you to choose a pump that closely matches the actual load requirements of your machine, rather than oversizing it.

Matching the pump shaft to your engine

One common challenge in global equipment integration is the variation in engine coupling standards across different markets. To simplify installation and improve compatibility, this series is available with four shaft-end options: plain key, rectangular spline, involute spline, and SAE spline. The SAE spline option is especially suitable for North American diesel engines, allowing direct connection to standard pump drives without the need for custom adapters, reducing installation time and complexity.

Efficiency
When you have mismatched gear modules, the displacement difference isn't linear. However, we have tuned the internal clearances so that both stages consistently maintain a volumetric efficiency of 92% across the series. This means the smaller rear stage won't bypass oil internally just because it is running behind a larger front stage-something we've seen happen in less carefully designed tandem pumps.

Operating Environment:

Hydraulic Oil: 20 - 43 cSt (Mineral hydraulic oil, ISO VG 32/46).

Working Temp.: -20°C to 80°C.

Filtration Accuracy: ≤ 25 μm.

Port Configuration: All models utilize flange connections. Mounting bolts for the pump housing and flange adapters are standardized to 8-M10X1.25 (depth 14).

Shaft Types: Plain Key, Rectangular Spline, Involute Spline, and SAE Spline.

Mounting: Standard 4-bolt oval flange.

Installation Dimensions (L1, L2, L): As shown in the table above, the total length L ranges from 225.5 mm to 254.5 mm. The three dimensions (L1, L2, and L) are critical for calculating mounting clearances.

The CBTL-*4/*4 type tandem gear pumps is most commonly found in mid-sized mobile machinery that needs two hydraulic circuits running off a single engine. In 5-ton wheel loaders, for example, the installation pattern we see most frequently is a CBTL-F420/F410. The 20 mL/r front pump drives the hydraulic cylinders for the loader bucket. The 10 mL/r rear pump is dedicated to the load-sensing steering system. This separation ensures that even when the bucket is forcing through a pile of material, the operator retains full steering control.

In larger agricultural tractors, the mixed displacement capability is often used for front-end loader attachments. A 20/16 mL/r combination gives the operator enough flow for the loader while still supplying a distinct flow for the rear remote valves that run driven implements.

For industrial hydraulic power units, this pump is a practical choice when you need to run two separate cylinders at different speeds, as long as the system is driven by a single electric motor.

Shaft end selection

Before you order, take a look at your engine's pump drive. If it's a North American SAE standard, order the SAE spline. If it's a European metric setup, you'll likely need the involute spline. We don't want you to end up with a mismatched shaft; that would require us to make a custom adapter, which pushes back your shipping date and adds extra machining costs.

Flange port connections

This series adopts flange connections for both inlet and outlet ports instead of threaded fittings. The mounting pattern is 8-M10×1.25. During installation, ensure the O-rings are correctly positioned and fully seated in their grooves. Avoid excessive bolt tightening, as it may deform the pump housing and lead to internal component binding, affecting overall performance and service life.

Mounting the unit
Because this pump can measure up to 254.5 mm in total length, the mounting bracket needs to support the full span. Use a torque wrench and tighten the four mounting bolts in a cross pattern. This prevents uneven stress on the aluminum housing.

Oil care

We advise keeping the hydraulic oil filtered to 25 microns or better. The internal bushings and the gear sets rely on a good fluid film to prevent wear. Regarding temperature: if the system runs above 80°C regularly, check the cooler. Since a tandem pump has more surface area than a single unit, thermal expansion isn't always even; the front stage and rear stage can expand differently, which often leads to the front stage showing wear before the rear stage does.

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