H2136201 - Hydraulic Gear Pump With 7/8-13 Spline Shaft And 2 Inch Diameter Gear

The H21 Series Hydraulic Gear Pump with Spline Shaft from Buyers Products is a sturdy, durable bi-rotational pump that can be 2- or 4-bolt mounted in an SAE B mount. The pump is built tough of cast iron with teflon-coated bronze thrust plates. Four internal dowels work to protect its structural integrity. Choose from a range of models with flow rates from 6.8 to 15.3 at 1000 RPM. The pumps are capable of higher pressures, taking up to 2500 or 3000 PSI. All of the models feature a 7/8 in. by 13 spline shaft.

Specifications

Advanced Technical Overview: H21 Series Hydraulic Gear Pump with 7/8-13 Spline Shaft and 2-Inch Gear

The H21 Series Hydraulic Gear Pump, specifically designed and manufactured by Buyers Products, represents a robust and highly reliable solution for a diverse range of hydraulic power transfer applications. Engineered for demanding environments, this external gear pump integrates advanced material science with precision mechanical design to deliver consistent performance, durability, and operational flexibility. This detailed technical exposition will delve into the critical aspects of its construction, performance parameters, and the engineering principles that contribute to its superior operational characteristics.

Fundamentals of External Gear Pump Operation

An external gear pump, such as the H21 Series, operates on the principle of positive displacement. Fluid is drawn into the pump by the rotation of two meshing gears, typically a drive gear and an idler gear. As the gears rotate, fluid is trapped in the spaces between the gear teeth and the pump housing. This trapped fluid is then carried from the inlet (suction) port to the outlet (pressure) port. As the gear teeth re-mesh at the outlet, the volume occupied by the fluid is reduced, forcing the fluid out under pressure. This mechanism ensures a consistent, pulsatile flow rate, largely independent of the system pressure, making external gear pumps highly efficient for generating hydraulic power.

The H21 Series distinguishes itself through its bi-rotational capability. This means the pump can operate equally effectively whether driven clockwise or counter-clockwise, providing significant versatility in installation and system design. This feature simplifies inventory management and offers greater adaptability for various power take-off (PTO) configurations or direct drive systems. The ability to reverse rotation is typically achieved through an internal valving arrangement or by designing the internal components to be symmetric, ensuring that the inlet and outlet functions can be reversed depending on the direction of shaft rotation.

Construction and Material Science: Engineered for Endurance

The foundation of the H21 Series pump's legendary durability lies in its material selection and meticulous construction. The primary housing is crafted from high-grade cast iron, a material celebrated for its exceptional strength-to-weight ratio, excellent vibration damping characteristics, and superior resistance to thermal distortion. In hydraulic applications, where fluctuating temperatures and high pressures are common, cast iron provides the structural integrity necessary to maintain tight internal tolerances over extended operating periods, which is crucial for maximizing volumetric efficiency and pump lifespan. The inherent density and rigidity of cast iron also contribute to lower noise emissions during operation, enhancing the overall user experience.

Within this robust housing, the H21 Series incorporates Teflon-coated bronze thrust plates. These components play a pivotal role in managing axial forces and minimizing internal leakage. Bronze, an alloy of copper and tin, offers excellent bearing properties and corrosion resistance. The addition of a Teflon (Polytetrafluoroethylene) coating significantly enhances these characteristics by drastically reducing the coefficient of friction. This low-friction interface between the rotating gears and the stationary thrust plates minimizes wear, reduces heat generation, and improves the pump's overall mechanical efficiency. Furthermore, these plates are crucial in controlling the axial clearance of the gears, which directly impacts volumetric efficiency by reducing fluid bypass from the high-pressure side to the low-pressure side.

Structural integrity is further bolstered by the inclusion of four internal dowels. These precision-machined pins serve multiple critical functions: they ensure precise alignment of the pump's internal components, including the gear housing and end plates, and they provide additional reinforcement against the substantial hydraulic forces generated during high-pressure operation. This meticulous alignment minimizes internal stresses, prevents premature wear, and maintains the tight dimensional tolerances necessary for consistent high performance and prolonged operational life.

Precision Gear Design and Displacement Characteristics

The core of any gear pump is its gear set, and the H21 Series features a precision-engineered gear set with a 2-inch diameter and a 2.000-inch gear width. These dimensions are directly correlated to the pump's volumetric displacement, which for this model, is approximately 4 cubic inches per revolution. Displacement is a fundamental parameter, defining the theoretical volume of fluid moved per revolution of the drive shaft. A 4 cubic inch displacement signifies a substantial fluid volume handled with each rotation, contributing to the impressive flow rates achieved even at moderate RPMs.

The precise machining of the gear teeth, often utilizing an involute profile, is paramount for smooth, quiet operation and efficient fluid transfer. Involute gears are designed to provide a constant velocity ratio between meshing gears, minimizing pulsation and vibration. The hardened steel gears are manufactured to exacting standards to resist wear from continuous contact and the abrasive nature of hydraulic fluid under pressure, ensuring long-term reliability and consistent performance.

Performance Envelopes: Flow, Pressure, and Rotational Speed

The H21 Series pump is engineered to deliver exceptional performance across its operational envelope. The flow rates provided are indicative of its high volumetric efficiency, even under varying load conditions. For the specific model detailed, a flow rate of 15 gallons per minute (GPM) at 1000 RPM is achieved. This translates to substantial hydraulic power for a wide array of applications. The detailed specifications further illustrate the pump's scalability across different RPMs:

• Flow at 600 RPM: 9.0 GPM
• Flow at 900 RPM: 13.5 GPM
• Flow at 1000 RPM: 15.0 GPM
• Flow at 1200 RPM: 18.36 GPM
• Flow at 1500 RPM: 22.5 GPM
• Flow at 1800 RPM: 27.0 GPM
• Flow at 2100 RPM: 31.5 GPM

These figures highlight the linear relationship between pump RPM and theoretical flow, a characteristic of positive displacement pumps. Slight deviations from perfect linearity in actual flow can occur due to internal leakage (slip), which increases with pressure and temperature. However, the H21 Series' design, incorporating features like Teflon-coated thrust plates and precision dowels, minimizes such losses, ensuring high volumetric efficiency across its operating range.

Pressure capability is another critical performance metric. This model is rated for a maximum pressure of 2500 PSI (pounds per square inch), with other variants in the H21 series capable of up to 3000 PSI. This high-pressure rating indicates the pump's ability to generate significant force within a hydraulic cylinder or motor, making it suitable for heavy-duty applications that require substantial lifting, pushing, or pulling power. The structural integrity of the cast iron housing, combined with robust internal components and sealing arrangements, allows the pump to withstand these intense pressures without deformation or premature failure.

The maximum recommended operational speed for this pump is 2000 RPM. Operating within this limit is essential for optimal performance and longevity. Exceeding the maximum RPM can lead to increased cavitation, excessive heat generation, accelerated wear on bearings and gears, and ultimately, premature pump failure. While flow data is provided up to 2100 RPM, this typically represents a peak or intermittent capability, and continuous operation should adhere to the specified maximum of 2000 RPM to ensure sustained reliability and warranty compliance.

Shaft Design and Power Transmission

A crucial interface between the power source (e.g., PTO, engine) and the hydraulic pump is the drive shaft. The H21 Series features a 7/8 inch by 13 spline shaft. A splined shaft is a superior choice for transmitting high torque loads compared to traditional keyed shafts. Splines are parallel ridges or teeth on a drive shaft that mesh with corresponding grooves in a mating hub or coupling. The advantages of a spline connection include:

• **Higher Torque Capacity:** Splines distribute the load over multiple teeth, reducing stress concentrations and allowing for higher torque transmission without slippage or damage.
• **Improved Alignment:** The multiple contact points of splines ensure better concentricity and alignment between the drive shaft and the driven component, minimizing vibration and wear on bearings.
• **Reduced Wear:** Even load distribution across many teeth reduces localized wear compared to a single keyway, extending the lifespan of the connection.
• **Axial Movement Capability:** Spline connections can often accommodate slight axial movement, which is beneficial in applications where minor misalignment or thermal expansion might occur.

The 7/8-inch nominal diameter with 13 splines is a standard configuration in mobile hydraulic applications, ensuring compatibility with a wide range of PTOs, gearboxes, and electric motors through appropriate couplings. The shaft itself is typically manufactured from high-strength alloy steel and often undergoes heat treatment processes such as induction hardening to enhance its torsional strength and wear resistance.

Mounting and Installation Versatility

The H21 Series Hydraulic Gear Pump offers significant flexibility in mounting, designed for a Direct Mount configuration utilizing an SAE B 2- or 4-bolt pattern. The Society of Automotive Engineers (SAE) B standard defines specific flange and bolt circle dimensions, ensuring interchangeability across various manufacturers' components. The availability of both 2-bolt and 4-bolt options provides adaptability for different drive configurations and torque requirements. The 4-bolt pattern generally offers greater rigidity and load distribution for more demanding applications. The 4.00-inch pilot diameter ensures precise concentric alignment with the mating drive component, which is critical for minimizing vibration, reducing shaft and bearing wear, and preventing premature seal failure.

The "Integral Bracket" input mount type further streamlines installation. This designation implies that the SAE B mounting flange is an integral part of the pump's cast iron housing, eliminating the need for separate adapters in many direct-mount scenarios. This design choice contributes to a more compact, rigid, and reliable installation, reducing potential points of failure and simplifying the overall system architecture.

Optimized Porting for System Integration

Efficient fluid transfer is paramount for hydraulic system performance, and the H21 Series addresses this with carefully sized and positioned ports. The inlet (suction) port and outlet (pressure) port are both 1 1/4 NPT (National Pipe Taper) connections. The generous sizing of the inlet port is critical for minimizing pressure drop and preventing cavitation, especially when handling higher flow rates or more viscous fluids. Cavitation, caused by insufficient inlet pressure leading to the formation and collapse of vapor bubbles, can severely damage a pump and degrade system performance. The 1 1/4 NPT size facilitates robust fluid intake, ensuring the pump is adequately supplied with hydraulic fluid.

Similarly, the 1 1/4 NPT outlet port is dimensioned to efficiently discharge the pressurized fluid into the hydraulic circuit with minimal restriction, thereby maximizing system efficiency. The use of NPT threads is standard in industrial and mobile hydraulics, providing a reliable, tapered seal when properly assembled with thread sealant. Furthermore, the pump offers both rear and side porting options, with a specific 1 NPT rear port size. This dual porting capability provides exceptional installation flexibility, allowing hydraulic lines to be routed optimally within the confines of diverse equipment designs, reducing hose lengths, and simplifying maintenance access.

System Considerations and Applications

Integration of the H21 Series hydraulic gear pump into a complete hydraulic system requires attention to several factors to ensure optimal performance and longevity. Proper hydraulic fluid selection, based on operating temperature and viscosity requirements, is crucial. High-quality filtration is indispensable for protecting the pump and other system components from particulate contamination, which is a leading cause of hydraulic component wear. A correctly sized reservoir and appropriate heat exchanger may also be necessary to maintain fluid temperature within acceptable limits.

Given its robust construction, high-pressure capability, and versatile mounting options, the H21 Series Hydraulic Gear Pump is ideally suited for a wide array of demanding mobile and industrial hydraulic applications, including but not limited to:

• Snowplows and salt spreaders
• Dump trucks and refuse vehicles
• Tow trucks and wreckers
• Agricultural machinery (e.g., tractors, harvesters)
• Construction equipment (e.g., compact loaders, excavators)
• Forestry equipment
• Material handling equipment
• Power units for various industrial processes

Conclusion

The H21 Series Hydraulic Gear Pump with its 7/8-13 spline shaft and 2-inch gear from Buyers Products stands as a testament to engineering excellence in hydraulic power transmission. Its meticulous design, combining a durable cast iron housing with advanced internal components like Teflon-coated bronze thrust plates and robust dowel pins, ensures exceptional reliability and longevity. The precision-engineered gear set delivers consistent, high-volume flow at pressures up to 2500 PSI, supporting a broad spectrum of demanding applications. Coupled with bi-rotational capability, versatile SAE B mounting, and optimized porting, this pump offers a highly adaptable and efficient solution for system designers and operators seeking uncompromised performance and enduring service life in their hydraulic systems.