Industrial Web Search Buyer's Guide Sector
Machines that move liquids by adding energy to them, from water and chemicals to slurries, oils, and food products, in industrial, municipal, and commercial systems. This sector covers centrifugal and positive-displacement pumps of all types, together with the seals, drivers, baseplates, controls, and packaged systems that turn a pump into a working installation.
Overview
A working orientation to the sector before you compare specific pumps: how the category divides, what actually determines whether a pump will work, and the kinds of company you will end up talking to.
The first consideration when choosing a pump is the pumping principle, which is determined by the liquid. Centrifugal pumps, which use a spinning impeller, are ideal for water and low-viscosity liquids at moderate to high flows, while positive displacement pumps, which push a fixed volume with each cycle, are suitable for viscous, shear-sensitive, or solid-laden liquids. Each type has various constructions, such as end-suction or submersible for centrifugal pumps, and gear or diaphragm for positive displacement pumps.
Pumps can be standard catalog products or engineered for specific applications, with the latter typically costing more and taking longer to deliver. The system into which a pump is integrated is crucial; the pump operates based on where its performance curve intersects the system's curve. Factors like suction conditions and fluid characteristics significantly influence performance and efficiency, with most pump failures stemming from incorrect duty points or unaccounted suction conditions.
Five main types of companies supply this sector: pump manufacturers provide standard pumps; engineered manufacturers cater to critical applications; seal manufacturers focus on reliability components; packagers combine systems; and repair shops offer restoration services. This distinction affects who manages the application and guarantees performance. It also tells you what to search for. A chemical process replacement means catalog pump manufacturers reached through their distributors, matched to the dimensional standard of the installed baseplate. Hot, hazardous, or critical service to an API specification means that pump manufacturers are engineered. A dosing package, booster set, or skid means packagers. A seal problem on a pump that otherwise works means seal manufacturers. A failed installed pump means a repair-and-rebuild shop first, because restoring the existing pump is often faster than any of the above.
Sourcing Considerations
The decisions below are the ones that most often cause regret later. The detail sits in the guides at the bottom of this page.
Document the required flow, total head at that flow, operational range, and liquid properties (temperature, specific gravity, viscosity, vapor pressure, and solids content). Calculate the head using static lift, pressure difference, and friction losses. Avoid adding safety margins to prevent oversizing the pump, which wastes energy and accelerates wear. The duty point is essential for every quote.
The suction head for your installation depends on the site conditions, including liquid surface pressure, elevation, suction piping, and liquid temperature. Calculate this and compare it to the net positive suction head required by the pump at maximum flow, ensuring compliance with Hydraulic Institute guidelines. Remember, cavitation, a common cause of impeller failure, originates on the suction side.
Viscosity, shear sensitivity, and flow requirements favor positive-displacement pumps, while clean, low-viscosity liquids at moderate to high flow rates suit centrifugal pumps. Consider installation factors such as suction lift and construction access when making construction choices. Positive displacement pumps need overpressure protection, and centrifugal pumps must operate above their minimum continuous flow, making control design essential in pump selection.
Specify a chemical process pump to ASME B73 or ISO 5199 for general and corrosive duty, reserving API construction for hot, hazardous, or critical applications. Detail wetted materials by grade and include all liquid components, as corrosion and abrasion resistance greatly influence costs. A dimensional standard ensures an easier replacement path without re-piping, providing significant long-term value.
Evaluate whether the liquid's hazards or value warrant a sealless pump to eliminate leakage risks. If a mechanical seal is used, do not accept the manufacturer's default; ensure the seal materials and flush plan are specifically engineered for your liquid's temperature and solids content. Always request the API flush plan number and its justification to confirm the sealing environment has been properly designed.
Decide if you're purchasing a bare pump or a complete unit with motor, baseplate, coupling, and controls, and ensure quotes match, as efficiency rules and supplier responsibilities vary. Specify the performance test standard, required documentation, and necessary spare parts. For clean-water pumps, compare the pump energy index rather than catalog efficiency. Request dimensional drawings and maintenance clearances before approving the selection.
Glossary
The terms you will meet on a pump curve, a datasheet, or a supplier proposal, in plain English.
The relationships describe how a centrifugal pump's flow, head, and power change with speed or impeller diameter: flow varies directly, head varies quadratically, and power varies cubically. They are why a modest speed reduction saves a large amount of energy and why a variable speed drive is often the cheapest capacity control available, provided the system curve allows it.
A positive displacement pump in which compressed air drives two diaphragms alternately to move fluid through check valves. It handles solids, slurries, viscous and shear-sensitive fluids, runs dry without damage, and is inherently safe in many hazardous locations, at the cost of pulsating flow and low energy efficiency compared with electric drives.
The ranges of flow, defined by the manufacturer relative to the best efficiency point, within which a pump may be operated continuously (allowable) and within which vibration and hydraulic loads are lowest (preferred). Specifying that the duty point fall inside the preferred region is the simplest protection a buyer can write against premature bearing and seal failure.
A bare pump is the pump alone, without a motor, coupling, baseplate, or controls; a pumping unit or pump set includes one or more of these components. Quotes are frequently not comparable because one includes the driver and another does not, and the federal efficiency rule rates bare pumps and complete units differently, so say which you are buying.
The flow rate at which a centrifugal pump converts the most shaft power into hydraulic power for a given impeller and speed. Operation far from it raises vibration, radial loads, and recirculation and shortens seal and bearing life, so the distance between your duty point and the best efficiency point is the single most useful thing to check on a proposal curve.
The formation and collapse of vapor bubbles in the pumped liquid when local pressure falls below its vapor pressure, usually at the impeller inlet. It causes noise, vibration, loss of head, and rapid impeller erosion. It is prevented by ensuring that the net positive suction head available exceeds the pump's required margin, which is a property of your system, not the pump.
A pump that adds energy to a liquid by accelerating it with a rotating impeller and converting the velocity to pressure in the casing. It delivers a smooth flow that varies with system resistance, suits low-viscosity liquids at moderate to high flow rates, and is the default choice wherever those conditions hold. Its output depends on the system curve, so it cannot be specified without knowing the system.
Two ways of connecting a pump to its motor. A close-coupled pump mounts the impeller directly on the motor shaft, saving space and alignment work. A frame-mounted pump has its own bearings and shaft, coupled to the motor on a baseplate, allowing the motor to be changed independently and heavier duties to be handled. The choice affects maintenance as much as price.
The flow rate and head at which the pump is required to operate, set by the process and the system it serves. It is the one number pair every quote is built on, and a duty point calculated with excessive safety margin is the most common reason pumps are oversized and run outside their preferred operating region.
A rotary positive displacement pump that carries liquid between the teeth of meshing gears and the casing. It suits viscous liquids such as oils, resins, and polymers, delivers nearly constant flow against varying pressure, and is intolerant of abrasive solids and dry running. Internal and external gear types differ in pressure capacity and in their handling of viscous fluids.
The energy a pump adds to a liquid, expressed as the height of a column of that liquid, in meters or feet, rather than as pressure. Head is independent of the liquid's density, which is why pump curves are drawn in head and why a pump produces the same head but a different pressure on a heavier liquid. Total dynamic head is the sum of static lift, friction losses, and the pressure difference the pump must overcome.
Reducing a centrifugal impeller's diameter by machining to shift its curve downward and match a duty point without changing speed. It is how a standard pump is fitted to a specific duty, and a proposal should state the trimmed diameter relative to the maximum so you know how much future capacity the casing can still provide.
A seal-less centrifugal or rotary pump in which the motor drives the impeller through a magnetic coupling across a containment shell, with no shaft penetrating the casing. It eliminates seal leakage for hazardous, toxic, or expensive liquids, but it is sensitive to dry running, solids, and loss of cooling flow, and the containment shell has its own pressure and temperature limits.
A device that seals the rotating shaft where it passes through the pump casing using two flat faces, one rotating and one stationary, held together and lubricated by a thin film of liquid. Seal selection depends on the liquid, temperature, pressure, and solids, and the seal, with its support system, is frequently the part of the pump that fails first and the one that most affects lifetime cost.
A positive displacement pump, usually diaphragm- or plunger-type, designed to deliver an accurately adjustable volume of liquid under pressure for dosing chemicals. It is specified by capacity, pressure, accuracy, and the turndown over which that accuracy holds, and in regulated industries it has its own design standard.
The lowest flow at which a centrifugal pump may run continuously without overheating, excessive recirculation, or vibration damage. Systems that can throttle the pump below it need a bypass or a control that prevents it from doing so, and a buyer should ask for the figure because it shapes the control design as well as the pump selection.
The absolute pressure energy at the pump suction above the liquid's vapor pressure, expressed in head, determined by the system: the pressure on the liquid surface, the static height above or below the pump, friction in the suction line, and the liquid temperature. It must exceed the pump's requirement by margin, and it is the buyer's figure to calculate, not the supplier's.
The suction head a particular pump needs at a given flow to operate without a specified loss of performance due to cavitation, determined by testing and published on the pump curve. It rises with flow, so a pump pushed to the right of its duty point can begin to cavitate in a system that was adequate at the design point. Margin between available and required is set by a Hydraulic Institute guideline.
A pump that moves a fixed volume of liquid with each revolution or stroke by trapping it and forcing it to the discharge, so that flow is nearly independent of pressure. The family includes gear, lobe, vane, screw, progressive cavity, diaphragm, piston, and peristaltic types. It suits viscous, shear-sensitive, and metered duties, and it must always have overpressure protection because it will build pressure until something yields.
A rotary positive displacement pump in which a helical rotor turns inside a double-helix elastomer stator, moving sealed cavities of liquid along its length. It handles viscous, abrasive, and solids-laden fluids gently with low pulsation, but the stator wears and will be destroyed by dry running, and the pump is long, which affects the layout.
The manufacturer's graph of head, efficiency, power, and net positive suction head required against flow for a pump at a stated speed and impeller diameter. It is the document a centrifugal pump is bought against, and the duty point, the best efficiency point, and the margin to the end of the curve should all be read from it before a proposal is accepted.
The metric defined in the United States Department of Energy's efficiency regulation for certain clean water pumps, which expresses a pump's weighted energy consumption relative to a minimally compliant pump, with values at or below 1 indicating compliance. It applies only to pump types within the regulation's scope, and the Hydraulic Institute administers a voluntary labeling program that reports it. Ask whether your pump is in scope before assuming the figure exists.
A standardized piping arrangement that supplies, cools, or contains the liquid around a mechanical seal, identified by a plan number in the API sealing standard and reproduced in Hydraulic Institute material. The plan is part of the seal selection; it carries its own hardware and utility requirements, and asking for the plan number is how a buyer confirms the seal environment has been engineered rather than assumed.
A centrifugal pump designed to evacuate air from its suction line and re-establish flow on its own after being started with the casing full of liquid, allowing it to sit above the liquid source. It is specified by the suction lift it can achieve and the time it takes to prime; it still requires an initial fill and an adequate net positive suction head once primed.
The head a centrifugal pump produces at zero flow, with the discharge closed. It is the maximum pressure the pump can impose on the downstream piping and equipment, so the system must be rated for it. A pump run at shutoff for more than a short period overheats the liquid in the casing.
Two liquid properties that change what a pump does. Specific gravity converts head into pressure and determines the power absorbed, so a pump selected for water will overload its motor on a heavier liquid. Viscosity reduces a centrifugal pump's head, flow, and efficiency, and, above a certain point, makes a positive displacement pump the better choice. Both belong on every request for quotation.
A pump and sealed motor assembly designed to operate while immersed in the liquid it pumps, common in wells, sumps, and wastewater systems. It removes the suction lift problem and the pump house, but the motor cooling, cable, and seal arrangement are part of the design and the unit must be lifted out for service, which affects how the installation is built.
The relationship between flow and the total head a piping system demands, combining the fixed static head with friction losses that rise with the square of flow. A centrifugal pump operates where its curve crosses the system curve, so the system curve determines what the pump will actually do, and it is the buyer's responsibility to establish it.
A multistage centrifugal pump with bowl assemblies suspended on a column into a well, sump, or tank, driven by a motor at the surface. It handles deep sources and large flows with a small surface footprint, but the column length, shaft support, and motor thrust bearing are engineered for the installation and must be specified based on site data.
The parts of a pump that contact the pumped liquid include the casing, impeller or rotor, shaft, seal faces, elastomers, and fasteners inside the casing. Each must be compatible with the liquid at the operating temperature, and corrosion and abrasion resistance drive cost more than pump size does, so name the materials by grade and state the liquid's composition, including contaminants.
Standards
What each standard governs and why a buyer should care. Which ones apply depends on the liquid, the industry, the severity of the service, and where the pump will be installed.
Hydraulic performance, testing, and energy
Published by the Hydraulic Institute (HI), the trade association for U.S. pump manufacturers, these standards, approved by the American National Standards Institute, cover terminology, design, allowable operating regions, net positive suction head margins, pump piping, intake design, viscosity corrections, and performance tests for both rotodynamic and positive displacement pumps. They are crucial for industrial pump purchases, as they provide the vocabulary for datasheets and supplier quotes. While buyers don't need to own the standards, referencing the acceptance test standard and net positive suction head margin in specifications helps prevent disputes after delivery.
ANSI/HI 14.6, published by the Hydraulic Institute, and ISO 9906, by the International Organization for Standardization, both define acceptance tests for hydraulic performance in rotodynamic pumps. They specify the measurement of flow, head, power, efficiency, and net positive suction head, along with tolerance grades for guaranteed values. These standards are used for certified performance tests instead of typical catalog curves, particularly for engineered pumps with performance guarantees. It's important to specify the applicable standard and acceptance grade, as they differ between ANSI/HI and ISO.
Administered by the U.S. Department of Energy, minimum energy efficiency requirements apply to specific categories of clean water rotodynamic and circulator pumps, measured by a pump energy index using Hydraulic Institute test methods. These requirements are defined by pump type, size, speed, and application, and exclude categories such as wastewater pumps. Confirm whether your pump falls under these regulations, as noncompliance means it cannot be sold in the U.S. Use the energy index for comparisons rather than relying solely on catalog efficiency.
The Hydraulic Institute (HI) administers a voluntary labeling program where manufacturers publish energy performance ratings for pumps tested to federal standards. This program provides a public database showing how much a pump's performance exceeds regulatory minimums. It applies to specific pumps for which a verified energy figure is needed, and some utility incentive programs reference it. The rating is relevant only for federally scoped pumps and depends on the specific configuration, whether bare or with motor and controls, so check the listing for the configuration you intend to purchase.
Pump construction and sealing standards
Published by the American Society of Mechanical Engineers (ASME), specifications for B73.1 (horizontal end-suction), B73.2 (vertical in-line), and B73.3 (sealless) centrifugal pumps ensure dimensional interchangeability, construction features, materials, and testing requirements. These pumps are designed for general chemical and industrial processes involving hazardous or corrosive liquids, without requiring compliance with petroleum-industry standards. Specifying a B73 pump allows easy replacement without repiping, making it advantageous in competitive markets.
Published by the American Petroleum Institute (API) and adopted as ISO 13709, this standard for centrifugal pumps in the petroleum, petrochemical, and natural gas industries defines construction types, design life, materials, bearings, and shaft sealing (referencing API 682). It applies to refineries, petrochemical plants, and gas processing sites for hot, hazardous, or critical services. API pumps are more expensive and have longer lead times than typical chemical process pumps, so they should be specified only when necessary, not out of habit.
The American Petroleum Institute (API) publishes standards for positive-displacement pumps used in the petroleum, chemical, and gas industries, including reciprocating (674), metering (675), and rotary (676) pumps. These standards address design, materials, pulsation control, testing, and documentation, and are applied in facilities that require API construction. The metering pump standard is also recognized for its accuracy and testing outside the petroleum sector. Like API 610, these standards are geared towards severe service, which can increase costs and lead times.
The American Petroleum Institute (API) publishes standards for shaft sealing systems in centrifugal and rotary pumps, covering seal categories, types, and arrangements; qualification testing; and piping plans for seal environments. As referenced in API 610, it's crucial for pumps handling hazardous or high-value liquids, where seal reliability is vital. The standardized plan numbers guide seal suppliers and pump manufacturers, and inquiring about the proposed plan helps ensure the seal is suited for your application.
ISO 2858, published by the International Organization for Standardization (ISO) and adopted by the European Committee for Standardization (CEN), specifies the dimensions and duty points of end suction centrifugal pumps. ISO 5199 outlines their technical requirements, including construction and vibration limits. These standards are the European equivalents of ASME B73.1, ensuring dimensional interchangeability among pumps built to them, but not with B73 pumps. They are relevant for purchases from European manufacturers or installations that comply with European practices, requiring replacement pumps to match existing baseplate and piping standards.
Application-specific certifications
Published by NSF, NSF/ANSI/CAN 61 determines if materials in contact with drinking water contribute harmful contaminants, while NSF/ANSI/CAN 372 assesses compliance with lead content limits. These standards apply to pumps, components, and coatings used in potable water systems, with certification often required in U.S. and Canadian jurisdictions. Certification is specific to each product and material, so a pump with multiple material options may only be certified in some cases.
Published by the National Fire Protection Association (NFPA), this standard outlines the installation of stationary fire protection pumps, including types, drivers, controllers, acceptance testing, and fire pump room layout. It requires that pumps and controllers be listed by a recognized testing laboratory and applies to pumps supplying sprinkler or standpipe systems, which differ from industrial pumps and must be approved by the authority having jurisdiction. Code editions are revised periodically, so check the applicable edition locally.
3-A Sanitary Standards are published by 3-A Sanitary Standards, Inc. in the U.S., while EHEDG guidelines are issued by the European Hygienic Engineering and Design Group. Both establish hygienic design criteria for materials, surface finishes, drainability, and cleanability, with specific standards for centrifugal and positive-displacement pumps used in dairy, food, beverage, or pharmaceutical applications. Although they overlap, they are not interchangeable. Always confirm which authorization your customer requires for a specific pump type.
The directive from the European Parliament and Council governs equipment, including non-electrical items such as pumps, for use in potentially explosive atmospheres within the EU and the EEA. IEC 60079, published by the International Electrotechnical Commission, outlines protection methods and testing for electrical equipment. If a pump operates in a classified hazardous area in Europe, it requires assessment, including the pump itself, not just its motor. In North America, the National Electrical Code applies to motors and instruments, while the pump body is governed by the owner's hazardous area practice, so specify the destination and area classification at the RFQ stage.
Frequently Asked Questions
Direct answers to the questions buyers ask most often when sourcing in this sector.
A centrifugal pump adds energy to the liquid with a spinning impeller, and its flow depends on the resistance of the system it feeds, falling as system head rises. A positive displacement pump traps a fixed volume of liquid and forces it to the discharge each cycle, so its flow is nearly constant regardless of pressure, and it will build pressure until something yields if the discharge is blocked. Centrifugal pumps suit low-viscosity liquids at moderate to high flows and are the default for water, chemicals, and most process duties. Positive displacement pumps suit viscous liquids, shear-sensitive products, accurate dosing, and high pressure at low flow. The choice is made by the liquid and the duty, and a positive-displacement pump always requires a relief valve or equivalent protection.
The liquid and its properties: composition, temperature, specific gravity, viscosity, vapor pressure, solids content, and anything corrosive or abrasive in it. The duty: required flow and total head, with the operating range if it varies, and the net positive suction head available at the pump suction. The installation: suction conditions, whether the pump sits above or below the liquid, whether it is indoor or outdoor, and any hazardous area classification. The construction: the standard the pump must meet, required or excluded materials, seal type and flush plan, and whether you want a bare pump or a complete unit with motor, baseplate, and controls. And the required documentation and testing, including any performance test standard and grade. Net positive suction head available and the liquid's full composition are the items most often missing, and both can entirely change the selection.
Net positive suction head is the pressure energy available at the pump inlet above the liquid's vapor pressure, expressed as head. The system provides a certain amount, called NPSH available, determined by the pressure on the liquid surface, the height of the liquid relative to the pump, the friction in the suction piping, and the liquid's temperature. The pump requires a certain amount, called NPSH required, which the manufacturer establishes by test and publishes on the curve. If available does not exceed required by an adequate margin, the liquid boils at the impeller inlet, and the resulting cavitation destroys performance and erodes the impeller. Suppliers ask because the available figure is a property of your system that only you can establish, and because no pump selection can compensate for a suction arrangement that does not provide enough of it.
A centrifugal pump is designed to run near its best efficiency point, and operating well to the left or right of it increases hydraulic loads, vibration, and internal recirculation, which shorten seal and bearing life regardless of how well the pump is built. Manufacturers define an allowable operating region and a narrower preferred region around the best-efficiency point; a duty point within the preferred region is the simplest way to buy reliability. Oversizing is the usual cause of trouble: a duty point calculated with layers of safety margin produces a pump that runs throttled, far left of its best efficiency point, wasting energy and wearing out early. Establish the duty honestly, ask the supplier to show where it falls on the curve, and ask for the minimum continuous flow and the net positive suction head required at the highest flow the system can demand.
Head is the energy a pump adds to a liquid expressed as the height of a column of that liquid, in meters or feet. Pressure is the force that column exerts, which depends on the liquid's density. A pump produces the same head on any liquid at a given flow and speed, but the pressure at its discharge and the power its motor draws are proportional to the liquid's specific gravity. This is why pump curves are drawn in head, why a pump selected on water can overload its motor on a heavier liquid, and why a supplier will convert your pressure requirement into head using the specific gravity you give them. If you state pressure without specific gravity, the selection is a guess.
Specify API 610 when the service is hot, hazardous, or critical enough that your industry or your owner's engineering standards require it, which in practice means petroleum, petrochemical, and gas processing facilities and the most severe services elsewhere. Specify a chemical process pump to ASME B73 in North America or ISO 5199 in Europe and much of the rest of the world for general chemical and industrial duties, including corrosive and moderately hazardous liquids, where you want a competitive market of dimensionally interchangeable pumps at a fraction of the cost and lead time. API pumps are built to a much heavier standard with longer design life, stricter testing, and more documentation, and that is what you pay for. Citing API 610 out of caution for a service that does not need it is one of the more expensive habits in pump procurement.
Choose a sealless pump, magnetic drive, or canned motor when the liquid is toxic, hazardous, expensive, or subject to emission limits, and a mechanical seal leak is unacceptable; or when the liquid is clean, has some lubricating value, and the pump will not run dry. Choose a mechanical seal for the broader range of liquids, temperatures, solids, and sizes that sealless designs do not cover, and engineer the seal and its flush plan for the liquid rather than accepting a default. Sealless pumps remove the seal as a failure point but add sensitivity to dry running, solids, and loss of cooling flow, and their containment shells have their own limits. In both cases, the sealing decision drives lifetime cost more than pump size does, so make it a deliberate decision early.
The United States Department of Energy sets minimum energy efficiency levels for defined categories of clean-water rotodynamic pumps and, separately, for circulator pumps under its energy conservation regulations. Compliance is expressed as a pump energy index measured under a federal test procedure that incorporates Hydraulic Institute methods, and pumps within scope may not be sold in the United States unless they meet this requirement. The scope is bounded by pump type, size, speed, and application: it covers five defined clean water pump families, end suction close-coupled, end suction frame mounted, in-line, radially split multistage vertical in-line, and submersible turbine pumps, and excludes many categories, including wastewater pumps, so the first question is whether your pump is covered. If it is, the index and the Hydraulic Institute's voluntary energy rating label provide a verified basis for comparing energy performance among manufacturers, which, over a pump's life, usually matters more than its purchase price.
A pump curve is the manufacturer's graph of head against flow for a pump at a stated speed and impeller diameter, with efficiency, power, and net positive suction head required plotted against the same flow axis. Your duty point should be marked on it. Check that the duty point falls inside the preferred operating region around the best efficiency point, that the net positive suction head required at the highest flow your system can demand is comfortably below what your system provides, that the motor is not overloaded at the end of the curve on your liquid's specific gravity, and that the impeller trim leaves some room to increase capacity later if you may need it. A proposal that does not include a curve with the duty point marked is incomplete, and a curve drawn for water when your liquid is not water needs a viscosity or specific gravity correction before it means anything.
Buyer's Guides
In-depth guides covering the decisions above.
Buyer's Guide
How to match pump type to application on fluid, viscosity, flow control, NPSH and duty, and where centrifugal or positive displacement is the wrong answer.
Read the guideMore coming
Additional guides are added when there is something genuinely worth saying, not on a schedule. IWS is committed to providing educational content to help you find the right suppliers!
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