What Is A Split Case Pump?

A split case pump, also known as a double suction pump, is a specialized type of centrifugal pump distinguished by its uniquely divided casing design. Unlike conventional pumps with integrated housings, its casing splits into two separable halves—typically horizontally or vertically—enabling easy access to internal components. This design, combined with its double-suction impeller, makes it a cornerstone in high-flow industrial applications worldwide.

Industry data underscores its significance: the global split casing pump market was valued at approximately USD 7.05 billion in 2024 and is projected to reach USD 12.8 billion by 2032, growing at a CAGR of 6.89% [grandview2024]. Another report further confirms this upward trend, estimating the 2024 market size at USD 8.444 billion with a 6.2% CAGR through 2033 [marketsandmarkets2024].

1. Core Design & Key Components

The split case pump's reliability stems from its robust, modular construction. Key technical components include:

• Split Casing: The signature two-piece housing (horizontal split is 80% more common than vertical) connects via bolts. It acts as a pressure containment vessel and allows top-half removal for maintenance without disconnecting piping or motors [ksb2023].

• Double-Suction Impeller: A rotating component that draws fluid from both sides, balancing hydraulic forces to reduce axial thrust by up to 40% compared to single-suction designs—significantly extending bearing lifespan [journalfluids2022].

• Drive Shaft: Typically made of 316 stainless steel, it transmits torque from the motor to the impeller, supported by anti-friction bearings to minimize energy loss [grundfos2024].

• Volute Casing: A curved chamber that converts the fluid's kinetic energy (from the impeller) into static pressure, with optimized flow paths to reduce turbulence by 25% [iso9906].

• Mechanical Seals: Prevents fluid leakage along the shaft, with materials (e.g., silicon carbide) selected based on the pumped medium's corrosivity [pumpengineering2023].

1.1 Split Case Pump Structure Diagram

Figure 1 illustrates the cross-sectional structure of a horizontal split case pump, highlighting core components and fluid flow paths.

Cross-sectional view of a horizontal split case pump (HSC) [ksb2023]

2. Operating Principle: How It Works

Split case pumps operate on the centrifugal force principle, following a four-stage process that ensures efficient fluid transfer:

• Fluid Inlet: Liquid enters the pump through central suction flanges, drawn equally into both sides of the double-suction impeller.

•  Energy Transfer: The motor-driven impeller (rotating at 1,450–3,600 RPM) imparts kinetic energy to the fluid, accelerating it radially outward.

• Pressure Conversion: The volute casing slows the high-velocity fluid, converting 60–70% of its kinetic energy into usable pressure energy [journalfluids2022].

• Discharge: Pressurized fluid exits through the discharge nozzle, with flow rates ranging from 50 to 10,000 m³/h depending on the model.

2.1 Key Hydraulic Formulas

The performance of split case pumps is governed by fundamental fluid mechanics equations:

2.1.1 Hydraulic Efficiency

Hydraulic efficiency (η) measures the ratio of useful water power to the shaft power input, a critical metric for energy-saving evaluation [iso9906]:

Where:  

• ρ = fluid density (kg/m³, typically 1000 kg/m³ for water),

• g = gravitational acceleration (9.81 m/s⊃2;), 

• Q = volumetric flow rate (m³/s), 

• H = total head (m), 

• P = shaft power (W).  

2.1.2 Axial Thrust Balance

A unique advantage of double-suction impellers is reduced axial thrust (F). For single-suction pumps, axial thrust is proportional to the impeller’s projected area; for split case pumps, it is approximated as [journalfluids2022]:

Where:  

• D = impeller outer diameter (m),

• ΔP = pressure difference across the impeller (Pa).

2.2 Performance Curve

3. Main Types: Horizontal vs. Vertical

The two primary configurations cater to distinct installation and operational needs. Table 1 summarizes their key differences and applications [marketsandmarkets2024, pumpengineering2023].

4. Key Applications & Industry Adoption

Split case pumps dominate applications requiring high flow rates (50–10,000 m³/h) and moderate heads (up to 200 meters). Major end-user segments include:

• Municipal Water & Wastewater: 35% of global demand—used for water treatment plants, distribution networks, and flood control. A single HSC pump can supply water to 50,000 residents [awwa2023].

• Power Generation: Critical for cooling water circulation in coal-fired and nuclear plants. A 1,000 MW power plant requires 4–6 split case pumps to handle 8,000 m³/h of cooling water [iea2024].

• Oil & Gas: Employed in crude oil transportation and refinery processes, with corrosion-resistant casings to handle hydrocarbons [api541].

• Fire Protection: Mandatory in industrial facilities and high-rises, as they meet NFPA 20 standards for reliable high-pressure water supply (10–20 bar) during emergencies [nfpa2023].

• Agriculture: Used in large-scale irrigation systems, with flow rates up to 5,000 m³/h to water 1,000 hectares of farmland.

5. Technical Advantages & Market Drivers

5.1 Core Performance Benefits

• Low Maintenance Cost: Split design reduces downtime by 50% vs. end-suction pumps—maintenance can be completed in 4–6 hours instead of 12+ hours [ksb2023].

• High Efficiency: Typical hydraulic efficiency of 75–90%, exceeding IE3 energy standards. This translates to 15–20% lower electricity costs over a 10-year lifespan [iso9906].

• Balanced Operation: Double-suction impeller minimizes axial thrust, reducing bearing wear by 30% and extending service life to 8–10 years [journalfluids2022].

5.2 Key Market Growth Drivers

• Rapid urbanization in Asia-Pacific: China and India account for 40% of new installations due to municipal infrastructure expansion [grandview2024].

• Industrialization: Growing demand from chemical and manufacturing sectors for reliable fluid handling [marketsandmarkets2024].

• Energy efficiency regulations: Governments mandating replacement of outdated pumps with high-efficiency split case models [iea2024].

6. Limitations & Considerations

Despite its advantages, the split case pump has constraints:

• Higher initial cost: 20–30% more expensive than end-suction pumps, though offset by lower lifecycle costs [pumpengineering2023].

• Not for high-pressure applications: Limited to heads below 200 meters—unsuitable for deep oil wells or high-rise boiler feed systems [grundfos2024].

• Size constraints: Horizontal models require more floor space, making them impractical for compact facilities [ksb2023].

1. [grandview2024] Grand View Research. (2024). Split Case Pump Market Size Report, 2032.

2. [marketsandmarkets2024] MarketsandMarkets. (2024). Centrifugal Pumps Market - Global Forecast to 2033.

3. [ksb2023] KSB SE & Co. KGaA. (2023). Split Case Pump Technical Handbook.

4. [journalfluids2022] Journal of Fluids Engineering. (2022). "Hydraulic Performance Optimization of Double-Suction Impellers".

5. [grundfos2024] Grundfos Group. (2024). Industrial Split Case Pump Catalog.

6. [iso9906] ISO 9906:2012. Rotodynamic Pumps - Hydraulic Performance Acceptance Tests.

7. [pumpengineering2023] Pump Engineering Magazine. (2023). "Split Case Pumps: Design Trends and Applications".

8. [awwa2023] American Water Works Association (AWWA). (2023). Water Supply System Design Manual.

9. [iea2024] International Energy Agency (IEA). (2024). Power Sector Fluid Handling Equipment Outlook.

10. [api541] American Petroleum Institute (API). (2022). API 541 Standard for Centrifugal Pumps in Petroleum Refineries.

11. [nfpa2023] National Fire Protection Association (NFPA). (2023). NFPA 20: Standard for the Installation of Stationary Pumps for Fire Protection.

12. [fao2022] Food and Agriculture Organization (FAO). (2022). Large-Scale Irrigation Equipment Guidelines.

Ready to upgrade your pump system? Contact us now for a free consultation. Let's find the perfect fit for your industry.