Pump Selection Guide

What Is Pump Selection?

A process of aligning process duty, system characteristics, fluid properties, pump hydraulics, mechanical design, materials, driver, standards, and operating conditions.

A pump is not selected from a catalog by flow rate alone. The selection process must consider the entire system — from suction conditions to discharge requirements, fluid behaviour, and the pump’s hydraulic performance envelope.

Pump selection is a decision that affects capital cost, operating cost, reliability, and maintainability for the life of the plant. In Oil & Gas, Petrochemical, and Refinery services, the consequences of an incorrect selection can be costly and hazardous. This guide walks you through the key engineering steps to make a sound selection.

How Engineers Select a Pump

Duty Definition ↓ Fluid Properties ↓ Flow & Head ↓ System Analysis ↓ Pump Type ↓ NPSH Check ↓ Pump Curve ↓ Materials ↓ Driver ↓ Standards ↓ Performance Verification

What Data Do You Need to Select a Pump?

A complete process datasheet is the foundation. Below is a checklist of essential parameters.

Parameter	Why It Matters	Typical Input
Flow Rate (Normal / Min / Max)	Defines pump sizing; must cover operating range	m³/h
Total Dynamic Head	Sum of static, pressure, friction, and velocity head	m
Suction Pressure	Affects NPSHA and suction-specific speed	bar(a) or bar(g)
Discharge Pressure	Required to overcome system backpressure	bar(g)
Fluid Temperature	Affects vapor pressure, viscosity, material limits	°C
Specific Gravity	Converts pressure to head; affects power	—
Viscosity	Affects pump performance and efficiency, especially for centrifugal pumps	cSt
Vapor Pressure	Required for NPSH calculation	bar(a)
NPSHA	Must exceed NPSHR with adequate margin	m
Solids / Corrosiveness	Determines material selection and pump type (e.g. slurry)	—
Operating Hours / Duty Cycle	Affects motor sizing, reliability, lifecycle cost	hrs/day
Applicable Standard	API 610, API 674, ISO 5199, etc.	—

Step 1 — Define the Required Flow

The flow rate is the starting point. You must distinguish between:

Normal Flow — the expected operating duty.
Minimum Flow — below which recirculation or thermal issues may occur.
Maximum Flow — the highest flow the pump must deliver.
Design Flow — often chosen at a point near BEP for best efficiency.

Selecting based on a single “max” flow without considering the operating range can lead to oversizing or operating too far from BEP. In continuous processes, the pump should be sized for the normal flow, but must be able to handle the extremes.

Illustrative Example: A refinery cooling water service requires 800 m³/h normal, 600 m³/h minimum, and 950 m³/h maximum. Sizing the pump for 950 m³/h at BEP would push normal operation far to the left, reducing efficiency and potentially causing recirculation.

Step 2 — Calculate the Required Head

Total Dynamic Head (TDH) is the energy the pump must add to the fluid. It is the sum of:

Static Head — difference in elevation between suction and discharge liquid levels.
Pressure Head — difference between discharge and suction vessel pressures converted to head.
Friction Head — losses in piping, valves, and fittings.
Equipment Pressure Drop — losses across heat exchangers, filters, etc.

Formula: TDH (m) = (P_discharge – P_suction) × 10.197 / SG + (Z_discharge – Z_suction) + h_friction

Where pressures are in bar(g), SG = specific gravity, Z in metres, h_friction in metres.

Always calculate head for the full operating range, including normal, minimum, and maximum flow.

Step 3 — Understand the Fluid

Fluid properties often dictate pump type, materials, and hydraulic selection. Key properties include:

Density / Specific Gravity — affects head-pressure conversion and power.
Viscosity — higher viscosity reduces centrifugal pump performance (head, flow, efficiency) and favours positive displacement pumps.
Temperature — influences vapor pressure, material strength, seal selection.
Vapor Pressure — critical for NPSH calculation.
Solids / Corrosive / Hazardous — may require special materials or pump types (slurry, lined, metallic).

Effect of viscosity: A centrifugal pump handling a fluid with viscosity above 100 cSt will experience significant head and flow reduction. The Hydraulic Institute provides correction factors; many OEMs have performance curves for viscous fluids.

Step 4 — Check the System Curve

The system curve represents the relationship between flow and head required by the system. The operating point is where the pump curve intersects the system curve.

Illustrative Example: Pump and System curves intersect at the operating point; BEP is shown for reference.

Select a pump whose curve intersects the system curve near BEP at the normal operating flow. A pump with a flat curve may be preferred when the system head varies; a steep curve is better for constant head.

Understanding a Centrifugal Pump Curve

A centrifugal pump curve displays the relationship between head (H), flow (Q), efficiency (η), power (P), and NPSHR. The key curves are:

Q-H Curve: Head vs. flow. Typically decreasing with flow.
Efficiency Curve: Efficiency vs. flow. Peaks at BEP.
Power Curve: Shaft power vs. flow. Usually increases with flow.
NPSHR Curve: Required NPSH vs. flow.

Note: The Q-H curve is based on water at a specific speed and impeller diameter. For other fluids, corrections for viscosity and SG are required.

When selecting, ensure the operating point falls within the preferred operating region (POR) – typically 70-120% of BEP flow. Avoid operating far to the left of BEP (recirculation, vibration) or to the right (cavitation, overload).

Best Efficiency Point (BEP)

BEP is the flow at which the pump operates at its highest efficiency. Operating near BEP minimises hydraulic loads, vibration, and noise, and maximises bearing and seal life.

Operating away from BEP:

Left of BEP: Increased radial thrust, recirculation, higher bearing loads, noise.
Right of BEP: Increased NPSHR, potential cavitation, higher power consumption.

Engineering best practice: For continuous duty, select a pump such that the normal operating point is between 80% and 110% of BEP flow. For variable speed, ensure the operating envelope remains within the POR.

NPSH — One of the Most Important Checks

Net Positive Suction Head (NPSH) is a measure of the energy available at the pump suction to prevent cavitation. It is a critical check because cavitation can lead to impeller erosion, vibration, seal failure, and loss of performance.

NPSHA > NPSHR is necessary, but not sufficient. Engineers must also consider margin for operating condition variations, and the basis of NPSHR (usually NPSH3).

Factors reducing NPSHA:

Higher liquid temperature (increases vapor pressure)
Higher suction piping losses
Lower liquid level in suction vessel
Higher elevation of the pump relative to liquid source
Higher vapor pressure of the fluid

Illustrative: NPSHA is calculated from the suction system to the impeller eye.

Avoiding Pump Oversizing

Bigger is not always better. Oversizing a pump forces operation away from BEP, throttling, wasted energy, and increased lifecycle cost.

An oversized pump may also cause:

Higher capital cost
Lower efficiency at normal duty
Increased vibration and noise
Higher bearing and seal loads
Potential motor overload if not properly controlled

If variable speed or impeller trimming is not an option, the next smaller pump size should be evaluated.

How to Choose the Right Pump Type

The table below provides general guidance. Final selection must be validated with detailed hydraulic and mechanical analysis.

Pump Type	Key Characteristics	Typical Applications
Centrifugal	High flow, low to medium head, low to medium viscosity	Water, chemicals, light hydrocarbons
Reciprocating (Piston/Plunger)	Low flow, very high head, medium viscosity	Injection, metering, high-pressure services
Gear	Low flow, medium head, high viscosity	Lube oil, bitumen, viscous fluids
Screw	Medium flow, medium head, very high viscosity	Crude oil, residues, multiphase
Slurry	Medium flow, low head, abrasive fluids	Mining, tailings, mud

Positive displacement pumps are typically selected for high viscosity or high-pressure-low-flow duties, while centrifugal pumps are preferred for low-viscosity, high-flow applications.

API 610 Pump Selection

API 610 (Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries) is the most widely used standard for process pumps in Oil & Gas. As of August 2026, the current edition is API 610 12th Edition (2020).

It covers design requirements, materials, inspection, testing, and documentation. Selecting an API 610 pump ensures reliability, interchangeability, and compliance with industry best practices.

When to specify API 610: For critical process services where the consequences of failure are high (e.g., hydrocarbon handling, high temperature, high pressure). For non-critical services, general industrial standards (ISO 5199) may be appropriate.

Note: API 610 pumps are often heavier, have larger shafts, and are designed for continuous, demanding operation compared to general industrial pumps.

API 674 Reciprocating Pump Selection

API 674 (Positive Displacement Pumps – Reciprocating) is the standard for reciprocating pumps in petroleum and chemical services. As of August 2026, the current edition is API 674 4th Edition (2021).

It covers piston, plunger, and diaphragm pumps. Applications include:

Chemical injection
Boiler feed
High-pressure water injection
Metering and dosing

When selecting an API 674 pump, consider pulsation dampening, driver compatibility, valve design, and material selection for the specific service.

Pump Selection for Oil & Gas

Oil & Gas applications demand robust pumps with high reliability and compliance with industry standards. Common services include:

Crude Oil Transfer – often uses centrifugal (API 610) or screw pumps.
Refinery Process – centrifugal pumps for hydrocarbons, often with mechanical seals and special metallurgy.
Water Injection – high-pressure reciprocating or multistage centrifugal pumps.
Boiler Feed – multistage centrifugal (BB4/BB5) or reciprocating pumps.
Cooling Water – large single-stage centrifugal pumps.

Each service requires careful evaluation of temperature, pressure, fluid composition, and operating regime.

Illustrative Pump Selection Example

This is an educational example to illustrate the logical steps of pump selection. It does not represent a Petropedam product.

Duty:

Fluid: Water
Flow: 100 m³/h
Head: 50 m
Temperature: 25°C
Specific Gravity: 1.0

Steps:

Define duty (flow, head, fluid).
Check fluid properties – temperature, viscosity, vapour pressure.
Determine total dynamic head (static + pressure + friction).
Review system curve to establish operating point.
Check NPSHA against NPSHR with margin.
Review pump curve for the required flow and head.
Check that the operating point is near BEP.
Check minimum continuous stable flow.
Select materials compatible with the fluid.
Verify driver sizing and applicable standard.

Illustrative example only. Actual pump selection requires verification of the complete process and system conditions.

Common Pump Selection Mistakes

1. Selecting by flow alone – ignores head, system, and fluid effects.
2. Ignoring the system curve – leads to wrong operating point.
3. Ignoring NPSH – causes cavitation.
4. Oversizing – wastes energy and reduces reliability.
5. Ignoring minimum flow – recirculation damage.
6. Ignoring viscosity – performance deviation for centrifugal pumps.
7. Ignoring temperature – affects material, seal, and NPSH.
8. Wrong material selection – corrosion/erosion failure.
9. Ignoring operating range – pump may run outside BEP.
10. Ignoring lifecycle cost – not just initial capital.
11. Ignoring driver requirements – motor sizing, power supply.
12. Treating catalogue data as complete – curves must be validated for the specific service.

Pump Selection by Industry

Oil & Gas

Crude transfer, injection, pipeline

Petrochemical

Process pumps, chemicals, polymers

Refinery

Hydrocarbon processing, utilities

Power Generation

Boiler feed, cooling, condensate

Steel & Metals

Cooling, descaling, dust suppression

Mining

Slurry, dewatering, process water

Water Treatment

Raw water, wastewater, reverse osmosis

Explore Petropedam Pump Products

From Pump Selection to Final Specification

Initial selection is only the first step. The final specification involves:

Initial Duty → Hydraulic Selection → Pump Curve Verification → Mechanical Review → Materials → Seal/Bearing → Driver → Standard → Datasheet → Vendor Review → Testing/Inspection → Final Selection

Each stage adds confidence and ensures the pump will perform reliably in the actual operating conditions.

Frequently Asked Questions

What information is needed for pump selection?

You need flow rate (normal, min, max), total head, suction and discharge pressures, fluid properties (temperature, SG, viscosity, vapour pressure), NPSHA, operating hours, and applicable standard (API 610, 674, etc.).

How do I select a centrifugal pump?

Define duty, calculate head and NPSH, select pump type (OH1, OH2, BB, VS), review Q-H curve, check BEP and power, select materials, driver, and standard.

How do I calculate pump head?

Head = static head + pressure head + friction head + velocity head. Use the formula TDH = (P_disch – P_suct) × 10.197 / SG + (Z_disch – Z_suct) + h_friction.

What is NPSHA?

Net Positive Suction Head Available is the energy at the pump suction above vapour pressure. It depends on suction pressure, liquid level, losses, and vapour pressure.

What is NPSHR?

Net Positive Suction Head Required is the minimum suction energy needed to avoid cavitation. It is determined by the pump manufacturer at the specified flow.

What is BEP?

Best Efficiency Point is the flow at which the pump operates at its highest efficiency. Operating near BEP maximises reliability and minimises energy consumption.

What happens if a pump is oversized?

Oversizing leads to operation away from BEP, throttling losses, higher vibration, reduced bearing/seal life, and increased lifecycle costs.

How does viscosity affect centrifugal pump selection?

Higher viscosity reduces head, flow, and efficiency. Corrections per Hydraulic Institute standards must be applied; positive displacement pumps are often preferred for viscous fluids.

When should I use a reciprocating pump?

Reciprocating pumps are used for low-flow, high-pressure applications, especially for metering, injection, and viscous or shear-sensitive fluids.

What is API 610?

API 610 is the standard for centrifugal pumps for petroleum, petrochemical, and natural gas industries. It specifies design, materials, testing, and documentation requirements. Current edition as of August 2026: API 610 12th Ed. (2020).

What is API 674?

API 674 is the standard for reciprocating positive displacement pumps for petroleum and chemical services. It covers piston, plunger, and diaphragm pumps. Current edition as of August 2026: API 674 4th Ed. (2021).

How do I select a pump for an oil and gas application?

Select a pump that meets API standards (610 or 674), with suitable materials for hydrocarbon service, correct NPSH margin, and capable of the required flow and head over the operating range.

Why Work With Petropedam?

Oil & Gas Focus

Experience in refinery and petrochemical projects.

API Experience

Pumps designed and supplied per API 610, 674, 676.

Engineering Depth

In-house hydraulic and mechanical engineering capability.

Project History

Proven delivery for industrial projects.

Technical References

API Standards – API 610 12th Ed. (2020) and API 674 4th Ed. (2021)
Hydraulic Institute – pump standards and guidelines
ISO 5199 – Technical specifications for centrifugal pumps
ISO 9906 – Rotodynamic pump performance tests
KSB – pump selection and engineering knowledge
Flowserve – industrial pump resources
Sulzer – pump technology and applications

Technical content reviewed: August 2026