Top OEMs for Split Case Pumps in Water & Wastewater Applications

Introduction to Split Case Pumps in Water and Wastewater Infrastructure

In the hierarchy of municipal and industrial hydraulic machinery, the split case pump stands as the predominant choice for high-flow, low-to-medium head applications. Characterized by a casing that is split parallel to the shaft axis (axially split) or perpendicular to it (radially split), this pump architecture is engineered to facilitate maintenance while offering inherent mechanical advantages regarding axial thrust balance.
For consulting engineers and plant managers, the split case pump represents the backbone of potable water distribution, raw water intake, and treated wastewater effluent pumping. Unlike submersible pumps or end-suction designs, the split case pump—specifically the double-suction horizontal split case (HSC)—is designed for longevity, often serving as a permanent fixture in a facility for 30 to 50 years. Consequently, the selection of an Original Equipment Manufacturer (OEM) is not merely a procurement decision; it is a long-term infrastructure commitment.
The operational environment for these pumps is rigorous. In potable water applications, they must deliver consistent pressure management with high wire-to-water efficiency to minimize electrical operating costs. In wastewater applications, typically utilized for secondary effluent or filtered water, they must handle potentially corrosive fluids and minor suspended solids without suffering premature volute erosion or seal failure.
The selection process is further complicated by the subtle variances in hydraulic design, metallurgy, and mechanical stiffness offered by different OEMs. While the fundamental physics of a centrifugal double-suction pump remains constant, the engineering execution—ranging from casing wall thickness and shaft deflection ratios to bearing housing designs and impeller trimming capabilities—varies significantly between manufacturers. This article provides a comprehensive, engineer-focused analysis of the top OEMs in the split case category, adhering strictly to specification-safe criteria and excluding marketing rhetoric.

Engineering Criteria for Selecting Split Case Pumps

Specifying a split case pump requires a multi-dimensional analysis that extends beyond the pump curve. Engineers must evaluate the mechanical integrity of the unit, its adaptability to the system curve, and its long-term serviceability.

Hydraulic Performance and Efficiency

The primary advantage of the split case design, particularly the double-suction impeller, is hydraulic balance. Fluid enters the impeller from both sides, theoretically canceling out axial thrust forces. However, hydraulic performance varies based on volute design.
* Best Efficiency Point (BEP): Selection should target pumps where the duty point falls within 80% to 110% of the BEP. Operating too far left of the curve induces recirculation cavitation, while operating too far right increases Net Positive Suction Head required (NPSHr), risking classic cavitation.
* NPSHr Margins: In open systems like cooling towers or raw water intakes, the margin between NPSHa (available) and NPSHr is critical. Premium OEMs optimize the suction eye geometry to minimize NPSHr, a critical factor when suction lift is required.
* Variable Speed Integration: Modern specifications almost universally require compatibility with Variable Frequency Drives (VFDs). The pump’s critical speed analysis must confirm that no resonance frequencies exist within the operating speed range of the VFD.

Mechanical Rigidity and Shaft Deflection

Long-term reliability is directly correlated to shaft stiffness. The “L3/D4” ratio (where L is the span between bearings and D is the shaft diameter) determines the shaft’s resistance to deflection.
* Deflection Limits: High-quality specifications typically limit shaft deflection at the seal face to less than 0.002 inches (0.05 mm) at dynamic conditions. Excessive deflection leads to rapid mechanical seal failure and decreased bearing life.
* Bearing Life (L10): Municipal specifications should demand an L10 bearing life of a minimum of 50,000 hours, with critical stations often requiring 100,000 hours. The spacing of the inboard and outboard bearings in a split case design is crucial for handling radial loads, especially when the pump operates off-BEP.

Materials of Construction and Metallurgy

The material selection dictates the lifecycle in aggressive environments.
* Casings: While Cast Iron (ASTM A48 Class 30 or 40) is standard for fresh water, Ductile Iron (ASTM A536) is preferred for higher pressure ratings due to its tensile strength.
* Impellers: Bronze (C87600 or C95200) is traditional, but 316 Stainless Steel or Duplex Stainless Steel (CD4MCu) is increasingly specified for wastewater effluent to resist erosion-corrosion and pitting from chlorides.
* Shafts and Sleeves: 420 or 316 Stainless Steel shafts are standard. Shaft sleeves are critical in packed pump applications to prevent shaft wear, often coated with ceramic or tungsten carbide in abrasive services.

Maintenance and Serviceability

The defining feature of the horizontal split case pump is the ability to remove the upper casing half to access the rotating assembly without disturbing the suction or discharge piping or moving the driver (motor).
* Jackings Screws: High-quality casings include integrated jacking screws to safely separate the casing halves, breaking the gasket seal without using wedges or chisels that could damage the machined faces.
* Seal Chambers: Engineers must evaluate the seal chamber space. Is there sufficient room to upgrade from packing to component mechanical seals, or to split-cartridge seals later in the pump’s life?
* Wear Rings: Replaceable casing and impeller wear rings are mandatory for municipal grade pumps. They allow operators to restore hydraulic efficiency by restoring tight clearances rather than replacing the expensive impeller or casing.

Comparative Analysis of Top OEMs

The following table outlines the operational profiles of the designated OEMs for split case pumps. This data reflects general product positioning and is not a substitute for specific curve analysis.

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Detailed Evaluation of Top OEM Manufacturers

The following manufacturers have been vetted based on their presence in the North American and Global municipal markets, the robustness of their split case product lines, and their adherence to Hydraulic Institute (HI) standards.

Fairbanks Nijhuis (Pentair)

Fairbanks Nijhuis represents a consolidation of historic brands with a deep focus on large-scale water movement. In the split case category, they are distinct for their ability to manufacture massive units that fall outside the catalogs of standard commercial pump manufacturers.
Technical Focus:
Fairbanks Nijhuis split case pumps are frequently specified for raw water intakes where flow rates are high and suction conditions are challenging. Their hydraulic designs often feature generous volute passages, which, while primarily for water, provide a degree of forgiveness regarding small solids that would foul tighter commercial pumps. Engineers often select Fairbanks for their versatility in configuration; they offer horizontal and vertical split case options, as well as bottom-suction configurations that can simplify piping layouts in compact pump stations.
Lifecycle & Build:
The casting quality of Fairbanks pumps is generally high, with heavy wall thicknesses that provide excellent corrosion allowance. Their “Sentinel” and standard split case lines often feature widely spaced bearings, contributing to favorable L3/D4 ratios. This results in minimal shaft deflection, a critical factor for maintaining seal integrity in large pumps starting across the line or via soft starters.

Goulds Pumps (Xylem)

Goulds Pumps, a brand within the Xylem portfolio, is perhaps the most ubiquitous name in North American pumping. The 3400 series of double-suction split case pumps is an industry benchmark for potable water distribution.
Technical Focus:
Goulds excels in hydraulic efficiency. Their engineering team heavily utilizes Computational Fluid Dynamics (CFD) to optimize the impeller eye and volute cutwater, resulting in pumps that frequently offer the highest wire-to-water efficiency in their class. For consulting engineers, this makes Goulds a strong candidate for projects with strict energy consumption constraints or LEED certification goals.
Lifecycle & Build:
A key differentiator for Goulds is the integration of technology. Many of their split case pumps come standard or optional with the i-Alert condition monitoring system, which tracks vibration and temperature. From a mechanical standpoint, they utilize a renewable casing wear ring design that locks securely to prevent rotation—a common failure mode in lesser pumps. Their shaft kits are modular, allowing for relatively easy change-outs of mechanical seals.

KSB

Headquartered in Germany, KSB is a global heavyweight in hydraulic engineering. Their Omega and RDLO series split case pumps are engineering marvels, often utilized in the largest water transport schemes globally.
Technical Focus:
KSB pumps are characterized by their interior hydraulic finish and precision. The RDLO series, for instance, features a double-volute design (on larger sizes) that effectively balances radial forces across the entire operating range, not just at the Best Efficiency Point (BEP). This allows for wider turndown ratios on VFDs without causing bearing fatigue. KSB is often the preferred OEM for high-head water transport applications where the pump must operate continuously at high pressures.
Lifecycle & Build:
The metallurgy offered by KSB is extensive, including Norihard and various Duplex Stainless Steel grades for aggressive water chemistries (such as brackish water or desalination permeate). The maintenance philosophy is one of “install and ignore” for long periods; however, engineers should note that KSB spares are proprietary and lead times can be longer than domestic US brands if not stocked locally.

Flowserve

Flowserve’s lineage includes Worthington and Ingersoll-Rand, brands that practically invented heavy-duty pumping. Their LNN and LN series split case pumps are built with an industrial mindset, prioritizing pressure containment and extreme duty cycles.
Technical Focus:
Flowserve dominates in applications requiring high pressure. While many split case pumps top out at 250-300 psi working pressure, Flowserve offers designs capable of significantly higher pressures, making them ideal for long-distance water transmission pipelines. Their hydraulic designs are stable, with relatively flat curves that are advantageous in systems where maintaining pressure is more critical than varying flow.
Lifecycle & Build:
The mechanical design of the LNN series emphasizes stiffness. The bearing housings are typically robust, 360-degree machined fits that ensure perfect alignment. Flowserve also offers extensive API-style baseplate options, which, while overkill for some municipal applications, provide a rigidity that prevents piping strain from distorting the pump casing—a leading cause of vibration issues.

Sulzer

Sulzer is a technology-driven OEM with a strong foothold in the water, oil, and gas sectors. Their split case offerings (SMD, SMH series) are highly regarded for their efficiency and compact power density.
Technical Focus:
Sulzer’s hydraulic profiles are optimized for low NPSHr, making them excellent candidates for retrofitting existing pump stations where suction conditions cannot be improved. They have also pioneered various coating technologies to improve hydraulic smoothers and resist corrosion, which can yield efficiency gains of 1-2%—significant over a 20-year lifecycle.
Lifecycle & Build:
Sulzer pumps are designed with the global market in mind, meaning they comply with both ISO and ANSI standards depending on the specification. Their split case designs often feature shorter bearing spans to increase shaft stiffness, utilizing modern manufacturing techniques to maintain tight tolerances. This results in very low vibration levels.

Peerless Pump

Peerless Pump has a unique reputation built on the absolute reliability required by the fire protection market (where they are a dominant player). This engineering philosophy permeates their municipal and industrial split case lines (AE Series).
Technical Focus:
Peerless split case pumps are straightforward, rugged, and reliable. While they may not always claim the absolute highest efficiency point compared to a CFD-optimized KSB or Goulds model, their curves are stable and predictable. They are particularly strong in the horizontal split case market for booster applications.
Lifecycle & Build:
The AE series is designed for ease of maintenance. The casing split line is precision machined, and the layout of the bearing housings allows for quick inspection. Peerless pumps are known for having generous service factors in their shaft sizing, making them forgiving of minor misalignments or system upsets that might damage more delicate, high-speed machines.

Aurora Pump (Pentair)

Aurora, a sister brand to Fairbanks Nijhuis under Pentair, occupies a vital niche. While Fairbanks handles the massive infrastructure projects, Aurora (specifically the 410 Series) is the workhorse for commercial, HVAC, and light-to-medium municipal applications.
Technical Focus:
Aurora pumps are designed for cost-efficiency and standardization. They offer excellent performance for standard water duty points. Their ” 90-Series” designation within the split case line is widely recognized. For consulting engineers working on standard booster stations, schools, or hospitals, Aurora provides a specification-compliant solution that fits budget constraints without sacrificing fundamental reliability.
Lifecycle & Build:
Aurora pumps utilize a specific locking methodology for their impeller wear rings that prevents rotation. They also offer “case-hardened” wear rings as an option. The design is modular, and because of their vast install base in the HVAC market, parts availability is among the best in the industry.

Patterson Pump

Patterson is a strong contender in the US market, particularly in the Southeast and for flood control applications. Like Peerless, they have a strong fire pump heritage that influences their general service water pumps.
Technical Focus:
Patterson’s split case pumps are known for high-flow capabilities. Their “Sentinel” series and HVAC/Municipal lines are characterized by simple, robust fluid dynamics. They are less likely to push the envelope on extreme efficiency if it compromises the mechanical safety factor of the pump.
Lifecycle & Build:
Patterson pumps are heavy. The casting walls are thick, providing good noise dampening and vibration resistance. They are a “maintenance-friendly” OEM, often using standard bearing sizes and seal configurations that do not require specialized proprietary tools to service. This makes them a favorite among municipal public works departments with limited specialized maintenance crews.

Application Fit Guidance

Selecting the right OEM often depends on the specific nuance of the application. While all listed manufacturers make split case pumps, their “sweet spots” differ.

Potable Water Distribution (High Service)

Primary Driver: Efficiency and Reliability.
Preferred OEMs: Goulds Pumps, KSB, Flowserve.
In high-service pumping, a 1% gain in efficiency translates to tens of thousands of dollars in energy savings annually. Goulds and KSB typically lead in wire-to-water efficiency. Their sophisticated monitoring options (vibration/temp) also suit these critical, often unmanned stations.

Raw Water Intake

Primary Driver: Solids Tolerance and NPSH.
Preferred OEMs: Fairbanks Nijhuis, Patterson, Flowserve.
Raw water often contains silt, sand, and organic debris. The tighter clearances of high-efficiency pumps can be a liability here. Fairbanks Nijhuis and Patterson offer robust designs with slightly more generous internal clearances and heavier wall thicknesses to withstand the abrasive nature of raw water.

Wastewater Effluent (Reuse)

Primary Driver: Corrosion Resistance.
Preferred OEMs: Sulzer, Goulds.
“Clean” wastewater is never truly clean. It contains chlorides and fine particulates. Sulzer’s experience with difficult fluids and their Duplex Stainless Steel material options make them a top contender. Goulds also offers robust material upgrades suitable for this environment.

Fire Protection and Emergency Systems

Primary Driver: Absolute Reliability and Code Compliance.
Preferred OEMs: Peerless Pump, Patterson, Aurora.
While this article focuses on municipal process water, dual-use stations often employ these brands. Their pumps are engineered to run to destruction if necessary, prioritizing flow delivery over equipment preservation during emergency events.

Engineer & Operator Considerations

Beyond the brand name, the success of a split case pump installation relies on the intersection of design and operation.

Maintenance Access and Piping Layout

A common engineering oversight is failing to provide adequate overhead clearance for lifting the upper casing half. Split case pumps require a vertical lift directly above the shaft.
* Guidance: Ensure the pump room design includes a monorail or bridge crane centered over the pump axis.
* Piping Strain: Split case pumps are susceptible to casing distortion if piping is not independently supported. Even minor distortion at the flange can misalign the bearing bores, leading to vibration. Flexible couplings are not a substitute for proper pipe support.

Sealing Systems: Packing vs. Mechanical Seals

* Packing: Traditional, allows for some leakage (cooling), and is forgiving of shaft deflection. Preferred in raw water applications where grit might shatter a mechanical seal face.
* Mechanical Seals: Zero leakage, lower friction. However, changing a standard mechanical seal on a split case pump requires decoupling the motor and potentially removing the bearing housing.
* The Split Seal Solution: Operators should strongly consider specifying split mechanical seals. These allow the seal faces to be replaced without stripping the pump down to the shaft, drastically reducing Mean Time To Repair (MTTR).

Spare Parts and Obsolescence

Municipal infrastructure lives on a timescale of decades.
* Guidance: Specification documents should require the OEM to guarantee parts availability for a minimum of 20 years.
* Standardization: If a plant already operates 10 Goulds pumps, the operational benefit of adding an 11th (interchangeable seals, bearings, and couplings) often outweighs a minor efficiency gain from a competitor.

Common Failure Modes to Anticipate

* Recirculation Cavitation: Occurs when oversized pumps run at low flows (far left of BEP). This attacks the impeller vanes and causes distinctive popping noises.
* Air Entrainment: Split case pumps in open suction systems (intakes) are vulnerable to vortices. Proper sump design (HI 9.8 standard) is as critical as pump selection.

Conclusion

The selection of a split case pump OEM for water and wastewater applications is a balance of hydraulic precision, mechanical robustness, and lifecycle support.
* Fairbanks Nijhuis and Flowserve excel in massive, custom, or high-pressure applications.
* Goulds Pumps and KSB set the standard for hydraulic efficiency and advanced monitoring in clean water distribution.
* Sulzer offers distinct advantages in corrosive or effluent environments.
* Peerless, Aurora, and Patterson provide rugged, reliable solutions that balance cost with proven performance in standard municipal duties.
For the consulting engineer, the goal is not merely to select a pump that meets the design point, but to specify a machine that fits the facility’s maintenance culture and operational profile. Detailed evaluation of the L3/D4 ratios, material specifications, and local support networks will yield a system that operates reliably for the next generation of public works.