Understanding Pump Performance: Flow, Head, and System Matching

A technical guide to selecting and matching pumps based on system curves, efficiency, and application requirements.

Why Pump Selection Must Be Based on System Performance

Pump performance is not determined by horsepower alone. Proper pump selection requires matching the pump curve to the system curve to ensure efficient, reliable operation.

Incorrect selection leads to:

• Reduced efficiency
• Increased wear
• Excessive energy consumption
• Premature pump failure

 PUMP CURVES

Pump Performance Curves Explained

$y = H(Q)$

A pump curve represents the relationship between:

• Flow (Q) – gallons per minute (GPM)
• Head (H) – total dynamic head (TDH)

Key elements of a pump curve:

• Best Efficiency Point (BEP)
• Shutoff head
• Operating range

 Pumps should operate near BEP for maximum efficiency and longevity.

 SYSTEM CURVE

System Curve vs Pump Curve

$H = H_s + kQ^2$

The system curve represents the resistance of the piping system.

It includes:

• Static head
• Friction losses
• Pressure requirements

Key concept:

The intersection of pump curve and system curve determines actual operating point.

 BEST EFFICIENCY POINT (BEP)

Operating at the Best Efficiency Point

The BEP is where:

• Efficiency is highest
• Vibration is lowest
• Mechanical stress is minimized

Operating away from BEP causes:

• Seal failures
• Bearing wear
• Increased energy cost

 Always size pumps to run close to BEP.

IMPELLER TYPES & PERFORMANCE

Impeller Selection Based on Application

Closed Impeller

• High efficiency
• Clean liquids

Open / Non-Clog Impeller

• Solids handling
• Wastewater applications

Vortex Impeller

• Minimal clogging
• Sludge and debris

Grinder / Cutter System

• Breaks down solids
• Used in pressure sewer systems

 FLUID PROPERTIES

Impact of Fluid Properties on Pump Selection

Pump performance changes based on:

• Viscosity
• Solids content
• Abrasiveness
• Temperature

Example:

• Slurry → requires hardened materials
• Wastewater → requires solids handling design

 POWER REQUIREMENTS

Power and Motor Sizing

$P = \frac{\rho g Q H}{\eta}$

Where:

• P = power
• ρ = fluid density
• Q = flow
• H = head
• η = efficiency

👉 Higher head and flow = higher power demand

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 REAL-WORLD APPLICATION MATCHING

Application-Based Pump Selection

 INDUSTRIAL APPLICATION EXAMPLES

Typical Use Cases

• Wastewater treatment plants
• Industrial processing systems
• Mining slurry transport
• Lift stations and force mains

 COMMON ENGINEERING ERRORS

Common Pump Selection Errors

• Selecting based on horsepower only
• Ignoring system curve
• Operating far from BEP
• Not accounting for solids
• Undersizing or oversizing pumps

REPLACEMENT & OPTIMIZATION

Optimizing Existing Pump Systems

Existing pumps can often be replaced with improved performance alternatives.

We match pumps from:

• Gorman-Rupp
• Tsurumi
• Flygt

to Barmesa Pumps equivalents with optimized efficiency and faster availability.

Common Brands Covered

This crossover system includes commonly used pumps from Flygt, Xylem, and Gorman-Rupp, with Barmesa equivalents identified based on performance and application requirements.

Need Help Matching a Pump?

If you need help selecting a replacement for a Flygt, Gorman-Rupp, or Xylem pump, contact our team with your model number, application, and operating conditions. We will identify the correct Barmesa equivalent.

North Coast Process Equipment specializes in identifying Barmesa pump equivalents for wastewater and industrial applications. North Coast Process Equipment provides pump cross reference solutions for municipal and industrial applications.

Serving municipal and industrial facilities across Ohio and the Midwest.