Hi 9.8 Rotodynamic Pumps For Pump Intake Design — Ansi

ANSI/HI 9.8-2024 is the current standard for the design and modification of rotodynamic pump intake structures, aiming to ensure uniform, steady flow while minimizing vortex formation and air entrainment. It covers diverse intake types—including rectangular, trench-type, and formed suction intakes—and provides crucial parameters for inlet bell design, minimum submergence, and acceptance criteria. For more details, visit Hydraulic Institute Store ANSI Webstore ANSI/HI 9.8-2018 - Rotodynamic Pumps for Pump Intake Design

The ANSI/HI 9.8 standard, titled "Rotodynamic Pumps for Pump Intake Design," provides essential guidelines for designing functional and economical pump intake structures. Its primary objective is to ensure that the liquid flow entering a pump is uniform, steady, and free from swirl or entrained air, which is critical for maintaining hydraulic efficiency and preventing premature mechanical failure. Core Objectives of the Standard

The standard aims to prevent several hydraulic issues that can reduce a pump's lifespan and performance:

Vortex Formation: Prevents both surface and sub-surface vortices that can lead to air ingestion and cavitation.

Flow Uniformity: Minimizes turbulence and non-uniform flow at the pump's inlet connection to reduce vibration and noise.

Solids Management: Provides specific design recommendations for intakes handling solids-bearing liquids (e.g., wastewater) to minimize accumulation and facilitate cleaning. Key Design Guidelines

The ANSI/HI 9.8-2024 standard, titled Rotodynamic Pumps for Pump Intake Design, is a critical industry benchmark for designing or modifying pumping facilities to ensure uniform, swirl-free, and air-free flow. Developed by the Hydraulic Institute (HI), it bridges fluid mechanics theory with practical geometry to maximize pump efficiency and lifespan. Core Design Objectives

The standard aims to prevent performance-degrading issues like cavitation, vibration, and loss of prime caused by poor intake geometry.

Uniformity: Ensures steady flow into the impeller eye to maintain optimum hydraulic efficiency.

Vortex Suppression: Provides criteria to minimize both free-surface and sub-surface vortices that can introduce air and damage mechanical seals or impellers.

NPSH Management: Helps engineers meet Net Positive Suction Head requirements by reducing entrance losses and pressure drops. Intake Types Covered

The standard provides specific recommendations for a wide variety of configurations:

The ANSI/HI 9.8 Rotodynamic Pumps for Pump Intake Design standard provides comprehensive criteria for designing pump intakes to ensure uniform, steady flow free from swirl and entrained air. Proper intake design is critical to maintaining high hydraulic efficiency, reducing vibration, and preventing premature pump failure. Core Design Principles

The standard identifies four primary goals for an ideal intake design:

Uniform Flow: Velocity should be consistent across the pump suction or inlet bell. Steady Flow: Flow patterns should remain stable over time.

Minimal Swirl: Rotation of the fluid before it enters the impeller should be minimized.

Air-Free: Preventing the ingestion of free-surface or entrained air to avoid cavitation and performance drops. Key Design Criteria & Limits

Designers use the standard to determine specific physical dimensions, including the height, length, and width of pumping stations. Swirl Angle: The average swirl angle should not exceed 5°.

Inlet Velocity: Typically recommended between 1.5 to 3.0 m/s (5 to 10 ft/sec), depending on fluid properties.

Submergence: Adequate depth must be maintained to prevent the formation of surface vortices.

Velocity Variation: Time-averaged velocities at the pump suction should be within ±10% of the cross-sectional average velocity. Applicable Intake Types

ANSI/HI 9.8 covers a wide range of specific configurations for both clear and solids-bearing liquids: ANSI/HI 9.8 Rotodynamic Pumps for Pump Intake Design

The silence in the subterranean pumping station was not truly silent. To the uninitiated, it was a cathedral of calm, punctuated only by the low, thrumming heartbeat of the district’s water supply. But to Elias Thorne, the silence was a chaotic symphony of friction, velocity, and pressure.

Elias stood on the grating of Intake Station #4, his hand resting on the guardrail. Below him, the wet well was a dark, still mirror, waiting.

"You're looking at the water again, Elias," a voice cracked over the radio. It was Miller, the new project manager, up in the control room. "The specs are on the server. Why are you down there with the bugs and the humidity?"

"Because the server doesn't tell me how the water feels, Miller," Elias muttered, keying the mic. He looked down at the surface. To most, it was a reservoir. To Elias, it was a battlefield waiting to happen.

The station was being retrofitted. The old pumps—reliable, brutish things from the seventies—were being swapped out for high-efficiency, variable-speed rotodynamic pumps. It was a delicate operation. The new pumps were sleek, powerful, and incredibly sensitive to bad manners.

And in the world of fluid dynamics, bad manners meant bad intake design.

Elias climbed the ladder back to the control room, his boots heavy on the rungs. He found Miller staring at a blueprint, a highlighter in his hand. Miller was a "numbers man." He lived in the clean, crisp lines of the AutoCAD drawing.

"Look," Miller said, tapping the paper. "We have the spacing. The suction bell is twelve inches off the floor. We’re good to go. I want to sign off on this today."

Elias walked over to the desk and picked up a heavy, bound book. The spine was cracked, the corners frayed. It was his bible: ANSI/HI 9.8: Rotodynamic Pumps for Pump Intake Design.

"You see a drawing, Miller," Elias said, his voice gravelly. "I see a trap."

Miller scoffed. "It meets the basic dimensions."

"It meets the minimums," Elias corrected. He opened the standard to a section on flow distribution. "See, the standard knows something you’re ignoring. Water is lazy. It takes the path of least resistance, and when you force it to turn, it gets angry."

Elias pointed to the blueprint. The layout called for a sharp 90-degree turn into the suction bell, just upstream of the pump.

"You've got high velocity coming in here," Elias traced the line with a callous finger. "The flow separation at that bend... you’re going to get a vortex."

"A vortex?" Miller laughed. "We have a vortex breaker designed in."

"The breaker handles the submerged vortices," Elias said quietly. "But what about the free-surface vortex? The one you can't see until it's screaming like a banshee and eating your impeller for breakfast?"

Miller stopped highlighting. He looked at Elias, then the book. "So what do we do?"

Elias flipped the pages of ANSI/HI 9.8 to the section on Approach Flow Distribution. The text was dry, technical, almost boring to the layman. But to Elias, it read like poetry. “Uniform velocity distribution... minimized swirl...” ansi hi 9.8 rotodynamic pumps for pump intake design

"The standard suggests a minimum straight run of pipe," Elias said. "But this geometry? It’s compromised. We need to break the flow. We need to tame it before it hits the eye of the impeller."

"You want to install a flow splitter?" Miller asked, the skepticism returning. "That’s extra steel. Extra time."

"It’s either a flow splitter now," Elias said, looking out the window at the dark water below, "or a new pump shaft in six months. You hear that silence, Miller?"

"Yeah."

"Right now, the water is resting. But when you spin that impeller at 1,800 RPM, you’re asking the fluid to accelerate and turn simultaneously. If the intake design is wrong—too shallow, too tight, wrong floor clearance—the water doesn't flow. It cavitates. It creates a low-pressure core. It drags air down from the surface."

Elias leaned in. "I've seen it happen. I was in Ohio in '09. Intake design ignored the ANSI standards. Thought they could cheat the floor clearance. The pump started singing. Sounded like gravel was going through it. Cavitation. The vibration tore the bearings apart in a week. We lost the whole station."

Miller swallowed. He looked at the ANSI/HI 9.8 standard, sitting there like a judgment stone. It wasn't just a guideline; it was the collected scars of a hundred failed pumps.

"So," Miller asked, the arrogance gone. "What does the book say?"

Elias smiled, a rare, tight expression. "It says we respect the fluid."

Together, they pored over the standard. They calculated the Froude number to check for floating ice potential, even though it was summer—prudence was the lesson. They adjusted the bell mouth clearance to the recommended value of 0.5 times the diameter to prevent floor vortices. They designed a cross-flow baffle to prevent swirl.

It took three days of redesigns. Miller complained about the budget, but Elias held firm. He cited paragraph after paragraph, wielding the standard like a shield against mediocrity.

Finally, the day of the startup arrived.

The station was sealed. The power was routed. Miller stood by the VFD (Variable Frequency Drive) panel, his hand hovering over the start button.

"Ready?" Miller asked.

Elias nodded. "Let’s see if we were polite."

The button was pressed.

The contactors slammed shut with a clack. The hum of the motor began, rising in pitch. Below the grating, the water began to move.

Usually, there is a moment of anxiety on startup. A shudder in the pipes. A groan from the bends as the water hammer works its way through. A brief rattle as air is purged.

But this time, there was nothing but the smooth, rising whine of the motor and the sound of rushing water, muffled and consistent.

Elias closed his eyes. He listened for the tell-tale crackle of cavitation—the sound of bubbles imploding under pressure. He listened for the rhythmic pulsing of a vortex sucking air.

There was none.

The amperage on the meter held steady. The pressure gauge climbed to the design head and settled.

"It's... smooth," Miller said, sounding surprised. "It's barely vibrating."

Elias opened his eyes. He walked over to the chart recorder. The line was a steady, unbroken horizon. No spikes. No surges.

"The water is happy," Elias said.

"Happy?" Miller looked confused.

"It went in straight, turned gently, and accelerated without breaking a sweat," Elias explained. "The intake design respected the laws of hydraulics. We followed the standard, so the physics didn't punish us."

Elias picked up his worn copy of ANSI/HI 9.8. He brushed a layer of dust off the cover. It was just a book of numbers, charts, and geometric ratios. But standing there in the cool, mechanical hum of a perfectly balanced pump, Elias knew it was something more. It was a map. It was the only way to navigate the invisible currents of a world that tried to drown you if you weren't paying attention.

Miller signed off on the paperwork. The project was a success. As they walked out of the station, the sun setting behind the treeline, Miller looked at Elias.

"Thanks for the fight on the baffles," Miller said.

Elias just tapped the book under his arm. "Don't thank me. Thank the guys who wrote this. They learned the hard way so we didn't have to."

Elias walked toward his truck, the heavy standard swinging by his side. The silence of the station behind him was heavy, durable, and safe. And for a hydraulic engineer, that was the deepest story of all.

Optimizing Pump Intake Design with ANSI/HI 9.8: A Guide to Rotodynamic Pumps

Rotodynamic pumps are a crucial component in various industrial and commercial applications, including water supply, wastewater treatment, and process industries. A well-designed pump intake is essential to ensure efficient and reliable operation of these pumps. The American National Standards Institute (ANSI) and the Hydraulic Institute (HI) have developed a standard specifically for rotodynamic pumps, ANSI/HI 9.8, which provides guidelines for pump intake design. In this blog post, we will explore the importance of pump intake design and how to apply the ANSI/HI 9.8 standard to optimize performance.

The Importance of Pump Intake Design

A pump intake is the inlet structure that supplies fluid to the pump. Its design plays a critical role in determining the pump's performance, efficiency, and reliability. A poorly designed intake can lead to:

Flow disturbances: Irregular flow patterns can cause uneven fluid distribution, leading to reduced pump performance and increased energy consumption.
Vortex formation: Vortices can form at the intake, causing suction lift, reduced pump performance, and increased risk of cavitation.
Sedimentation and debris accumulation: Inadequate intake design can lead to sedimentation and accumulation of debris, which can clog the pump and cause maintenance issues.

ANSI/HI 9.8: The Standard for Rotodynamic Pump Intake Design

The ANSI/HI 9.8 standard provides guidelines for the design of pump intakes for rotodynamic pumps. The standard covers various aspects of intake design, including:

Intake types: The standard identifies three types of intakes:
- Sump intake: A submerged intake with a sump or a pit.
- Canal intake: An intake that draws fluid from a canal or an open channel.
- Pipe intake: An intake that draws fluid directly from a pipe.
Design criteria: The standard provides guidelines for designing intakes, including:
- Approach flow: The standard recommends a minimum approach flow velocity of 0.3 m/s (1 ft/s) to minimize flow disturbances.
- Intake geometry: The standard provides guidelines for intake geometry, including the inlet bell shape, sump size, and submergence depth.
- Screen and trash rack design: The standard recommends design criteria for screens and trash racks to prevent debris accumulation.

Applying ANSI/HI 9.8 to Optimize Pump Intake Design ANSI/HI 9

To optimize pump intake design using the ANSI/HI 9.8 standard, follow these steps:

Determine the intake type: Select the intake type that best suits your application, considering factors such as fluid characteristics, available space, and pump requirements.
Conduct a site survey: Gather data on the site conditions, including topography, fluid level, and surrounding structures.
Design the intake: Apply the design criteria outlined in the standard, ensuring that the intake geometry, approach flow, and screen and trash rack design meet the guidelines.
Model and test the design: Use computational fluid dynamics (CFD) or physical models to test the design and identify potential issues.
Refine and finalize the design: Based on the results of the modeling and testing, refine the design and finalize the intake configuration.

Conclusion

A well-designed pump intake is crucial to ensure efficient and reliable operation of rotodynamic pumps. The ANSI/HI 9.8 standard provides a comprehensive framework for designing pump intakes, helping to minimize flow disturbances, vortex formation, and sedimentation. By applying the guidelines outlined in this standard, engineers and designers can optimize pump intake design, reduce energy consumption, and improve overall system performance.

References

ANSI/HI 9.8-2014: American National Standard for Rotodynamic Pumps for Pump Intake Design
Hydraulic Institute: Pump Intake Design Guidelines

The ANSI/HI 9.8 Rotodynamic Pumps for Pump Intake Design is a definitive industry standard developed by the Hydraulic Institute (HI) to ensure that the flow of liquid into a pump is uniform, steady, and free from hydraulic disturbances. Proper intake design is critical because poor hydraulic conditions can lead to reduced efficiency, excessive vibration, and premature mechanical failure. Core Objectives of ANSI/HI 9.8

The primary goal of the standard is to provide engineers and contractors with a foundation for developing functional and economical pumping facilities. Key objectives include:

Uniform Flow: Ensuring liquid enters the impeller eye at a steady velocity profile.

Vortex Prevention: Minimizing surface and sub-surface vortices that can entrain air or cause cavitation.

Optimal Performance: Reducing the risk of swirl and air ingestion, which can significantly decrease hydraulic efficiency. Scope and Applications

The standard covers a wide range of intake structures for both clear and solids-bearing liquids:

Intake Types: Includes rectangular intakes, formed suction intakes (FSI), trench-type intakes, circular pump stations, and unconfined intakes.

Pump Configurations: Applicable to vertical turbine pumps (can-type), barrel pumps, and suction tanks.

Market Use: Widely used in municipal water/wastewater, petrochemical, and power plant cooling systems. Key Design Criteria and Acceptance Standards

To achieve an "acceptable" design, the standard outlines specific measurable criteria, often verified through physical model studies or Computational Fluid Dynamics (CFD): Vortex Control at Pump Intake Using Double

Here’s a useful, structured content piece on ANSI/HI 9.8 – Rotodynamic Pumps for Pump Intake Design, aimed at engineers, plant operators, and design professionals.

7. Suggested Improvements for Next Edition

Add more case studies of successful CFD validation.
Provide simplified “good practice” tables for small pumps (<50 hp).
Include guidance on transient conditions (starting/stopping, rapid level changes).
Update vortex criteria for high-specific-speed mixed-flow pumps.

End of Draft Review

The ANSI/HI 9.8-2024 standard, titled Rotodynamic Pumps for Pump Intake Design, is the definitive American National Standard for engineering efficient, reliable pump stations. Developed by the Hydraulic Institute (HI), this standard provides the technical framework for designing new intakes and modifying existing ones to ensure optimal hydraulic performance. Core Objectives of ANSI/HI 9.8

The fundamental goal of the standard is to ensure that flow reaching the pump impeller is uniform, steady, and free from swirl or entrained air. Poorly designed intakes often lead to:

Reduced Efficiency: Non-uniform velocity distributions at the pump suction can significantly lower hydraulic performance.

Mechanical Damage: Problems like cavitation, high vibration, and noise can cause premature mechanical seal and bearing failures.

Operational Issues: Formation of surface or submerged vortices and excessive pre-swirl can lead to air entrainment and performance drop-off. Standard Intake Configurations

ANSI/HI 9.8 defines specific geometries for several common intake types. Adhering to these "standard" designs often eliminates the need for expensive physical testing. ANSI/HI 9.8-2018 - Rotodynamic Pumps for Pump Intake Design

The ANSI/HI 9.8-2024 standard, Rotodynamic Pumps for Pump Intake Design, provides the definitive guidelines for designing intakes that ensure uniform, steady flow into rotodynamic pumps. Its primary objective is to eliminate hydraulic phenomena like submerged vortices, entrained air, and non-uniform velocity distributions that cause vibration, noise, and premature mechanical failure. Key Design Pillars

The standard outlines specific criteria for various intake types to maintain hydraulic efficiency and equipment longevity:

Flow Uniformity: Ideally, liquid entering a pump should be free from swirl and entrained air. Lack of uniformity can result in lower hydraulic efficiency and reduced reliability.

Vortex Control: Provides rules for minimum submergence and wet well geometry to minimize surface and sub-surface vortices.

Velocity Limits: Recommends maximum inlet velocities (typically 1.2 to 3.0 m/s) to prevent cavitation and excessive pressure drops.

Physical Model Studies: Requires physical scale modeling if a proposed design deviates from the standard's established "standard intake" geometries. Common Intake Structures Covered The standard specifies designs for several applications:

Clear Liquids: Rectangular intakes, formed suction intakes (FSI), circular pump stations, and trench-type intakes.

Solids-Bearing Liquids: Specialized trench-type, circular, and rectangular wet wells designed to reduce solids buildup and allow for easy removal.

Suction Can Pumps: Detailed guidance on vertical turbine and submersible motor can intakes. ANSI/HI 9.8 Rotodynamic Pumps for Pump Intake Design

ANSI/HI 9.8 Rotodynamic Pumps for Pump Intake Design

Introduction

The American National Standards Institute (ANSI) and the Hydraulic Institute (HI) have collaborated to develop a standard for rotodynamic pumps, specifically focusing on pump intake design. This standard, ANSI/HI 9.8, provides guidelines and recommendations for the design of pump intakes to ensure efficient and reliable operation of rotodynamic pumps.

Scope

This standard applies to rotodynamic pumps, including centrifugal, mixed-flow, and axial-flow pumps, used in various industries such as water supply, wastewater treatment, and industrial processes. The standard covers pump intakes for both horizontal and vertical pumps, with a focus on design considerations for optimal performance.

Key Considerations for Pump Intake Design

The standard highlights several key considerations for pump intake design:

Inlet Velocity: The inlet velocity should be within the range of 0.3 to 1.5 m/s (1 to 5 ft/s) to minimize turbulence and ensure a smooth flow into the pump.
Submergence: The submergence of the pump intake should be sufficient to prevent vortex formation and ensure a stable flow. The recommended submergence is at least 0.3 to 0.6 m (1 to 2 ft) below the water surface.
Intake Shape and Size: The intake shape and size should be designed to minimize turbulence and ensure a uniform flow distribution. A well-designed intake should have a gradual transition from the approach flow to the pump inlet.
Approach Flow: The approach flow to the pump intake should be smooth and uniform, with minimal turbulence. This can be achieved by providing a sufficient straight pipe length upstream of the pump intake.

Design Guidelines

The standard provides detailed design guidelines for pump intakes, including:

Bellmouth Inlets: Bellmouth inlets should be designed with a gradual expansion to minimize turbulence and ensure a smooth flow into the pump.
Elbow Inlets: Elbow inlets should be designed with a large radius to minimize turbulence and ensure a smooth flow into the pump.
Intake Screens: Intake screens should be designed to minimize head loss and prevent debris from entering the pump.

Benefits of Proper Pump Intake Design

Proper pump intake design offers several benefits, including:

Improved Pump Performance: A well-designed pump intake ensures a smooth and uniform flow into the pump, resulting in improved pump performance and efficiency.
Reduced Maintenance: A properly designed pump intake reduces the risk of clogging and debris accumulation, resulting in reduced maintenance costs.
Increased Reliability: A well-designed pump intake ensures a reliable operation of the pump, reducing the risk of downtime and increasing overall system reliability.

Conclusion

The ANSI/HI 9.8 standard provides a comprehensive guide for pump intake design, ensuring that rotodynamic pumps operate efficiently and reliably. By following the guidelines and recommendations outlined in this standard, pump designers and engineers can design and install pump intakes that minimize turbulence, ensure a smooth flow into the pump, and optimize pump performance.

ANSI/HI 9.8 standard, titled "Rotodynamic Pumps for Pump Intake Design,"

is the definitive American national guideline for designing and evaluating pump station intake structures. Published by the Hydraulic Institute (HI)

, it provides normative criteria to ensure that the flow entering a pump is uniform, steady, and free from harmful phenomena like vortices or excessive swirl. Core Design Objectives

The primary goal of the standard is to optimize the hydraulic environment at the pump inlet to prevent reliability issues such as cavitation, vibration, and reduced hydraulic efficiency. Key objectives include: Uniform Flow Velocity:

Ensuring the velocity profile at the pump's impeller eye is consistent to prevent side-loading and uneven bearing wear. Vortex Suppression:

Minimizing free-surface and sub-surface vortices that can entrain air or cause pressure pulsations. Swirl Minimization:

Controlling the rotation of the fluid before it enters the pump. Solids Handling:

For wastewater applications, designs must prevent the buildup of solids and allow for easy removal of settled or floating debris. Intake Types Covered

The standard provides specific dimensional guidelines for various intake configurations: Pipes, Pumps & Valves Africa Jan-Feb 2023 - Issuu

Optimizing Performance: A Deep Dive into ANSI/HI 9.8 for Pump Intake Design

In the world of fluid handling, a pump is only as good as the water it receives. If the intake design is flawed, even the most expensive rotodynamic pump will suffer from efficiency loss, vibration, and premature mechanical failure. The industry gold standard for addressing these challenges is ANSI/HI 9.8 (Rotodynamic Pumps for Pump Intake Design)

This standard provides a rigorous framework for designing intake structures that ensure uniform, steady flow free from swirl and entrained air. The Core Objective: Uniform Flow

The primary goal of any intake designed under ANSI/HI 9.8 is to deliver a uniform velocity profile

to the pump impeller. Poor approach conditions can lead to several catastrophic issues:

Both surface and subsurface vortices can entrain air or create localized low-pressure zones, leading to cavitation. Pre-swirl:

Flow that enters the pump with a rotational component (swirl) changes the angle of attack on the impeller blades, drastically reducing hydraulic efficiency. Non-Uniform Velocity:

When flow hits one side of the impeller harder than the other, it creates unbalanced radial loads, leading to accelerated bearing wear and component fatigue. Key Design Requirements

ANSI/HI 9.8 outlines specific geometric and hydraulic requirements for various intake types, including rectangular, circular, trench-type, and unconfined intakes. 1. Minimum Submergence (

To prevent the formation of strong air-core surface vortices, the standard provides formulas based on the Froude number cap F sub cap D ). A common calculation for minimum submergence is:

cap S equals cap D open paren 1 plus 2.3 cap F sub cap D close paren is the outside diameter of the bell or pipe inlet. cap F sub cap D

is the Froude number, a dimensionless flow parameter representing the ratio of inertial to gravitational forces.

A. Bell Diameter (Db) vs. Pipe Diameter (Dp)

The pump bell (the flared inlet) is larger than the suction pipe. HI 9.8 defines Db as the critical dimension. All distances are ratios of Db.

C. Bell-to-Floor Clearance (C)

The distance from the bottom edge of the bell to the sump floor.

Range: 0.3 Db ≤ C ≤ 0.5 Db
Critical nuance: Too high (C > 0.5 Db) allows bottom vortices. Too low (C < 0.3 Db) restricts flow and causes high losses.

Operating Scenarios

You must design for:

One pump running at min flow.
One pump running at BEP (Best Efficiency Point).
Two pumps running in parallel.
Any combination of asymmetrical operation (e.g., left pump only, right pump off).

Failure mode: If you run only the left pump in a wide wet well without splitter walls, the flow will cross from the right bay, creating massive asymmetrical swirl.

1. Approach Flow Velocity

Maximum velocity in the intake channel: ≤ 0.5 m/s (1.6 ft/s) for critical pumps; ≤ 0.9 m/s (3 ft/s) for less critical.
Uniform velocity profile across the intake bay.

Mastering the Approach: A Deep Dive into ANSI/HI 9.8 for Rotodynamic Pump Intake Design

Introduction: The Hydraulic Highway

In the world of fluid handling, the pump is often considered the heart of the system. However, even the most efficiently engineered heart will fail if the veins leading to it are clogged or turbulent. For rotodynamic pumps (centrifugal, mixed flow, and axial flow), the intake structure—the sump, wet well, or suction piping—is that critical vascular system.

Poor intake design is the leading cause of pump vibration, cavitation, loss of efficiency, and premature bearing or seal failure. For decades, engineers relied on "rule of thumb" or disparate German (VDI) and British (BHRA) standards. Today, the global gold standard is ANSI/HI 9.8.

Published by the Hydraulic Institute (HI), ANSI/HI 9.8 Rotodynamic Pumps for Pump Intake Design is the definitive American National Standard for ensuring that the liquid arrives at the pump impeller eye with uniform velocity and zero swirl.

This article unpacks the critical requirements of ANSI/HI 9.8, exploring why suction-side hydraulics matter, the specific geometry rules for wet wells, the dangers of vortices, and the modeling techniques required for approval.

Part 4: Vortex Classification – The HI 9.8 “Vortex Scale”

Before you can design against vortices, you must identify them. HI 9.8 provides a standardized Vortex Scale (Type 1 to Type 6):

Design goal: Achieve Type 1 or 2 at minimum NPSH available and maximum flow.