New Pump Selection
I know the required flow/head or operating condition and need to identify a suitable split-case configuration.
Build Selection BriefTechnical Resources
Split Case Pump Selection & Performance Guide
Use flow, head, liquid properties, NPSH, speed and installation constraints to build a practical split-case pump selection or replacement brief.
QFlow / capacity
HHead
NPSHrPump required NPSH
rpmSpeed / frequency
Selection first, product secondUse this page to organize the operating condition, then move into the S-series model selector or replacement workflow.
Project Route
What Are You Working On?
Existing Pump Replacement
I have an installed KSB Omega, Sulzer ZPP or another split-case pump and need a replacement review.
Start Replacement ReviewSelection Workspace
Start with the operating condition, not the model number
Enter the operating condition to build a practical selection brief before choosing a model.
Selection brief not built yet
Enter the operating condition to generate the next engineering checks.
Flow and head define the hydraulic target.
Liquid and temperature drive material and seal review.
Installation and retrofit constraints determine the next page.
Read the Performance Data
Understand the fields before comparing models
Review the hydraulic fields used to compare candidate pump models and verify the final duty point.
Q
Flow / Capacity
The required liquid volume per unit time. Use the real system requirement rather than selecting a pump only from nominal size.
Double-Suction Design
Why the hydraulic architecture matters in high-flow service
A double-suction impeller distributes inlet flow across both sides. Double-suction and double-volute describe different design features; confirm the approved pump construction for the selected model.
01
Two-sided inletLiquid enters both impeller eyes, allowing the double-suction arrangement to handle high flow while helping reduce hydraulic axial imbalance.
02
Axial-force reductionOpposed inlet flow helps reduce axial hydraulic thrust. Final rotor and bearing loading still depends on the actual hydraulic design and operating point.
03
Split casing service accessThe upper casing can be removed for rotor inspection while the main suction and discharge piping remain connected, subject to installation access and the approved pump arrangement.
Split-Case Engineering Insights
Separate axial-thrust balance from radial-force balance
These are related but different design topics. A double-suction impeller and a double-volute casing should not be treated as the same feature.
Double-Suction Impeller → Axial Thrust Balance
Opposed inlet flow helps balance and reduce axial hydraulic thrust; it should not be interpreted as complete elimination of axial force under every operating condition.
Double-Volute Casing → Radial Force Balance
Some split-case designs use a double-volute casing to reduce radial hydraulic force. Confirm the construction of the selected model rather than assuming every S-Series configuration uses the same casing architecture.
NPSH Quick Check
Use a simple head-form NPSH check before model comparison
This calculator is intentionally lightweight. It helps organize the suction-side inputs; final NPSH margin still requires project engineering review.
NPSHa = Pa + Hz − Hf − Pv
Enter all terms as liquid head (m). NPSHa is compared with the selected pump's required NPSHr; any desired margin is an engineering input, not a universal rule.
Result
Calculated available NPSH
– mSelected pump NPSHr
Not enteredDifference vs NPSHr
– mEnter suction-side values to calculate the available NPSH and compare it with NPSHr.
This is a simplified screening tool. Unit consistency, elevation datum, fluid vapor pressure and project-specific margin must be verified before final pump selection.
Horizontal vs Vertical Decision Matrix
Choose the arrangement from site constraints, not a generic preference
The S-series catalog states that horizontal or vertical mounting can be used depending on site conditions. The final configuration requires the correct GA drawing.
| Decision factor | Horizontal arrangement | Vertical arrangement |
|---|---|---|
| Floor space | Requires a conventional horizontal footprint. | May reduce floor-area demand, subject to the actual vertical configuration. |
| Maintenance access | Often straightforward for top-casing inspection and horizontal drive alignment. | Access strategy depends on the actual driver and support arrangement. |
| Motor / coupling | Horizontal motor and coupling arrangement is typical. | Vertical driver arrangement must be verified from GA and project design. |
| Foundation / structure | Conventional baseplate / foundation review. | Structural support and vertical load path require specific review. |
| Piping | Check suction / discharge centerlines and flange orientation. | Check flange orientation, piping loads and support arrangement. |
| Existing retrofit | Common for installed horizontal split-case systems. | Do not assume interchangeability; field layout and GA are essential. |
Operating Range Check
BEP, POR and AOR belong in the final performance review
Compare the required duty point with the verified performance curve. Do not assume a universal POR percentage or invent a BEP point when the approved curve is not available.
01
BEP
Best Efficiency Point
The highest-efficiency point shown on the approved pump curve.
02
POR
Preferred Operating Range
The operating range defined by the manufacturer or project specification.
03
AOR
Allowable Operating Range
The wider allowable range, subject to hydraulic, mechanical and NPSH checks.
Configuration Decision
Split Case vs End-Suction Pump: When Does the Selection Change?
| Selection Factor | End-Suction Pump | Split-Case Pump |
|---|---|---|
| Moderate flow | Often suitable | May be unnecessary |
| Very high flow | Larger/multiple units may be required | Often a strong candidate |
| Footprint | Usually compact | Larger horizontal footprint |
| Maintenance | Design-dependent | Top casing access can be advantageous |
| Retrofit | Standardized process-pump interfaces may simplify some replacements | GA/interface review is critical |
| Existing installation | Verify duty and interfaces | Installed dimensions are a major selection input |
For ANSI B73.1 process-pump replacements, review the ANSI process pump range.
Application Decision
When a Split-Case Pump Is Worth Considering
High-Flow Cooling Water
Consider split-case architecture where continuous high flow and maintainability are major design drivers.
Municipal / Water Transfer
Suitable for large-volume water movement when hydraulic duty, installation layout and lifecycle access justify the configuration.
HVAC / District Cooling
Often considered for condenser-water or chilled-water circulation at large flow rates.
Power / Industrial Circulation
Use duty point, NPSH, speed and service conditions to determine whether the split-case arrangement is appropriate.
Common Selection Mistakes
Six Common Split-Case Pump Selection Mistakes
Each mistake below changes the engineering decision or the evidence required for release.
01
Oversizing Head “for safety”
Excess head can move the operating point away from the intended duty and may increase flow, power demand and operating instability.
02
Ignoring NPSH Margin
Checking only Q/H while neglecting suction conditions can leave too little margin against cavitation.
03
Choosing Speed Too Early
Coordinate speed with motor frequency, impeller trim, hydraulic performance and service expectations.
04
Using Nominal Size as Selection
A matching DN does not prove hydraulic suitability. Compare the real duty point and verified performance data.
05
Retrofit Without GA Review
For an existing installation, flange location, centerline, footprint and coupling interface can matter as much as Q/H.
06
Ignoring Driver, Material & Service Constraints
Confirm the driver, liquid properties, temperature, material and seal requirements for the actual service before releasing the selection.
Materials & Sealing
Start from verified catalog options
Final material selection depends on the real liquid, temperature and project requirement.
| Component | Verified GB grades | Selection note |
|---|---|---|
| Pump casing | HT250 / QT400-18 / ZG230-450 | Confirm against service and project specification. |
| Impeller | ZCuSn10Pb1 / HT250 / ZCuZn16Si4 / ZG1Cr18Ni9Ti | Confirm against liquid chemistry and operating condition. |
| Shaft | 2Cr13 / 45# | Confirm environment and mechanical requirements. |
| Shaft seal | Mechanical seal / Packing | Confirm leakage, maintenance and service requirements. |
Pump Sizing Sheet
Turn the selection brief into a shareable engineering record
Review the data, save the sheet as PDF if needed, and send it for engineering follow-up.
Engineering Review
Split Case Pump Sizing Sheet
Carry the duty point, liquid, installation and NPSH screening result into a compact project sheet that can be saved as PDF or sent with an RFQ.
ANSI Pumps Pro – Split Case Pump Sizing Sheet
Engineering screening record
| Flow Q | – |
| Head H | – |
| Liquid | – |
| Temperature | – |
| Speed / Frequency | – |
| Installation | – |
| Project type | – |
| Existing Brand | – |
| Existing Model | – |
| Nameplate / GA availability | – |
| NPSHa screening | Not calculated |
| NPSH comparison | Not calculated |
| Recommended next step | Build selection brief |
Send a Simple Inquiry
Write the same message you would send by email. The selection brief and NPSH result above are carried into the inquiry automatically.
Use Print / Save PDF for a local engineering record. You can also send a short inquiry and attach any available project document.
Choose Your Next Step
Continue with the workflow that matches the project
New Split-Case Pump
Review the S-Series range and continue from the duty point.
Browse S-Series Split Case PumpsKSB Omega / Omega V Replacement
Submit the installed configuration for hydraulic and interface review.
Review KSB Omega ReplacementSulzer ZPP Replacement
Continue to the dedicated ZPP replacement engineering route.
Review Sulzer ZPP ReplacementSelection brief updated