technical info

Centrifugal pumps move liquids in industrial, commercial, and municipal applications. But what determines how much fluid a pump can move? The maximum flow rate isn’t only about the pump itself; it depends on several factors. 

8 Factors Impacting Centrifugal Pump Flow Rate

Ever wonder what’s really limiting your pump’s flow rate? Knowing these details helps you get the most out of your system.

1. Impeller Design

The impeller plays a major role in flow rate. Its design, size, and vane configuration affect how much liquid the pump moves.

• Larger impeller vanes generate higher flow rates by displacing more liquid with each rotation.
• Larger impeller diameters generate higher pressures by increasing the tip speed, which imparts more kinetic energy to the fluid, resulting in greater conversion to pressure head within the pump.
• Curved vanes improve efficiency by reducing turbulence, while straight vanes handle solids better but may slightly reduce efficiency.
• More vanes can improve efficiency in clean low-viscosity fluids but may reduce the pump’s ability to move debris or viscous liquids due to tighter flow passages.

However, bigger and faster isn’t always better. Selecting an impeller that is too large or aggressive for the system can lead to unnecessary energy use or excessive wear over time. A well-matched impeller design for actual operating conditions often works better than maximizing size and speed.

2. Pump Speed (RPM)

The rotational speed of the impeller (measured in RPM) affects the flow rate according to pump affinity laws, but system resistance may limit actual gains in flow. The faster it spins, the more liquid it moves. 

However, increasing speed isn’t always beneficial. Higher RPM increases flow rate, but exceeding recommended limits can cause excessive wear, overheating, or even pump failure.

Expert Tip: Variable-frequency drives can help fine-tune speed, but they are not a universal fix. If your system is poorly designed, a VFD may not solve efficiency issues.

3. Suction Conditions

Poor suction conditions can reduce a pump’s ability to move fluid. To maintain flow:

1. Keep the suction line clear and free of obstructions.
2. Ensure the inlet is submerged to prevent air entrainment.
3. Ensure that Net Positive Suction Head Available (NPSHa) is always higher than the pump’s required NPSHr to prevent cavitation, which can damage the impeller and reduce efficiency.
4. Use an adequately sized suction pipe to minimize friction losses.

Despite manufacturers’ claims, real-world suction conditions are rarely ideal. System design flaws, like poorly placed inlets or air leaks, often cause bigger performance issues than the pump itself. Addressing these external factors first can sometimes improve performance more than upgrading the centrifugal pump.

Expert Tip: A filter on the suction side will help prevent solids and debris from entering the pump. However, we recommend you maintain 5–10 pipe diameters of straight pipe between the filter and the pump suction inlet. Rule of Thumb: Don’t allow more than 1–2 psi pressure drop across the suction filter, especially in low-NPSHa systems.

4. Discharge Pressure 

Pump flow rate and discharge pressure have an inverse relationship: the higher the pressure required at the outlet, the lower the achievable flow rate. If the system demands high pressure, the pump has to work harder, potentially reducing efficiency. Reducing unnecessary restrictions in the discharge piping, such as excess valves and sharp bends, can help maintain flow.

Some operators mistakenly assume that increasing discharge pressure is necessary for better performance. In reality, many systems suffer from excessive pressure demands due to poor piping design rather than actual operational needs. Reevaluating system pressure requirements can sometimes improve efficiency without requiring a more powerful pump.

5. Fluid Characteristics

The type of liquid being pumped affects flow rate.

• Viscosity: Thicker fluids (like oil or syrup) move more slowly than water and require more power to pump at the same flow rate. Tip: For pumping viscous fluids, consider lowering RPM rather than increasing motor power to prevent excessive wear on the impeller.
• Temperature: Fluids with extreme temperatures can change viscosity, affecting how easily they flow.
• Specific Gravity: Heavier liquids exert more pressure on the pump, influencing how much volume can be moved and how much motor horsepower is required.

6. Pipe Size & Length

The size and length of the piping system also affect pump flow rate.

• Narrow pipes create friction, reducing the pump’s ability to move fluid efficiently.
• Long pipe runs add resistance, further limiting the achievable flow.
• Sharp bends and fittings introduce turbulence, increasing energy losses.

Instead of defaulting to a larger pump, many experts argue that modifying piping size and layout can achieve better results at a lower cost. 

7. System Design

A poorly designed system can restrict flow even if the pump itself is capable of high performance. Obstructive bends, tight valves, and improperly sized pump components create resistance that can reduce efficiency. Many flow limitations come from the broader system, not the pump itself. Total Dynamic Head (TDH), including friction loss and system resistance, plays a significant role in determining actual pump performance.

8. Pump Efficiency & Wear Over Time

Even a properly designed system can experience flow rate reductions due to wear and tear. Over time, impeller erosion, scaling, and corrosion inside the pump and pipes, as well as seal and bearing wear, can increase internal resistance and reduce efficiency.

Expert Tip: Regularly inspect and clean impellers, as mineral deposits and debris buildup can drastically reduce performance over time.

Find the Right Pump with American Stainless Pumps

American Stainless Pumps offers high-quality centrifugal pumps designed for efficiency and durability. Our stainless steel pumps are built to handle a range of industrial and commercial applications, ensuring reliability and long-term performance. 

Contact us today to learn more about ASP.

Centrifugal pumps are the backbone of countless industrial processes, but maintaining peak performance requires proper care and timely troubleshooting. In this guide, the pump experts at ASP explore maintenance practices and practical solutions to common centrifugal pump issues. American Stainless Pumps’ current line of products do not have wearing parts, and are assembled with electric motors that use sealed bearings. This drastically reduces maintenance requirements. The maintenance guidelines below are for centrifugal pumps in general and may vary based on the specific features of each pump.

Maintenance costs should always be weighed against the cost of a new replacement pump assembly, as well as the cost of potential downtime. In many cases, the cost of removing and disassembling the pump is greater than simply swapping the old one out for a new assembly.

Proper maintenance keeps your pump running smoothly, minimizes downtime, and extends its lifespan. Here are the key steps:

1. Perform Regular Inspections

In pumps with wearing parts, regular inspections are necessary to keep your centrifugal pump in acceptable condition. Look for visible signs of wear, corrosion, leaks, or misalignment, as these can lead to bigger issues if not addressed. Also, check that all bolts, seals, and connections are secure to prevent leaks and maintain optimal performance.

2. Keep the Impeller Clean

Check for debris or buildup on the impeller that could reduce performance. Clean it as needed to maintain proper flow and pressure. Ideally, a strainer would be introduced in the suction line, far away from the pump to avoid issues with NPSH available. The strainer should be placed at least 5 to 10 times the pipe diameter upstream of the pump suction inlet.

3. Monitor Bearings & Lubrication (for motors that contain non-sealed bearings)

• Bearing Maintenance: Inspect bearings for wear or damage. Replace them as needed.
• Lubrication: Make sure proper lubrication levels in bearing assemblies. Over-lubrication can cause friction and overheating, while under-lubrication can lead to wear.

4. Inspect Seals & Gaskets

• Mechanical Seals: Examine mechanical seals for leaks or damage. Worn seals can allow fluid to escape, leading to reduced pressure or contamination of the surrounding area.
• Gasket Integrity: Replace gaskets showing signs of wear, cracking, or deformation. Damaged gaskets can compromise the pump’s efficiency and safety.

5. Maintain the Pump Casing

Inspect the casing for cracks, corrosion, or wear. Even small cracks can lead to leaks or structural weakness, potentially causing catastrophic failure in high-pressure applications.

Also, keep the casing clean to prevent corrosive substances or debris from damaging the exterior, which could lead to long-term degradation.

6. Monitor Vibration & Noise Levels

• Vibration Analysis: Excessive vibration often indicates issues such as misalignment, imbalance, or damaged components. Use vibration monitoring tools to identify the source of the problem and address it promptly.
• Noise Monitoring: Listen for abnormal noises, such as grinding or whining. (These can signal problems with motor bearings, failing pump components,  or even cavitation, which occurs when vapor bubbles form in the fluid due to low pressure.)

Even with regular centrifugal pump maintenance, things can still go wrong from time to time. Here’s what we’ve learned about troubleshooting the most common centrifugal pump problems:

1. Low Flow or No Flow

• Check the Suction Line: Look for blockages or air leaks.
• Review System Conditions: verify the pump is operating within its designed parameters.
• Inspect the Impeller: Make sure it’s not clogged or damaged.

Centrifugal Pump Troubleshooting Tip: Regularly clean the impeller to prevent buildup from reducing performance.

2. Excessive Vibration

• Misalignment: For extended shaft pumps, realign the pump and motor shafts.
• Worn Bearings: Replace damaged bearings.

Note: In smaller 48/56 frame motors, the cost of switching bearings is usually more than a new motor. 

• Impeller Imbalance: Clean or replace the impeller if necessary. If it’s imbalanced, give it a clean or replace it.

3. Leaking Seals

• Inspect Seals & Packing: Replace worn seals or packing materials.
• Check for Overpressure: Verify the pump is not operating beyond its pressure limits and ensure the liquid inside the pump never freezes.

Centrifugal Pump Troubleshooting Tip: Install a pressure relief valve in your system to protect seals and gaskets from excessive pressure.

4. Overheating

• Insufficient Lubrication: Check lubrication levels in bearings.
• Blocked Flow: make sure the suction and discharge lines are clear to prevent issues with NPSHa.
• Overloading: Verify the pump is not handling a higher load than it was designed for. Operating within or more than the service factor of the motor may cause premature failure.

5. Noisy Operation

• Cavitation: Check for low suction pressure or excessively high fluid temperature.
• Loose Components: Tighten bolts and make sure all parts are securely attached.

• Always follow the pump manufacturer’s guidelines for operation and maintenance.
• Keep a log of maintenance activities to track performance trends.
• Don’t skimp on replacement parts. Use high-quality replacement parts to maintain performance and reliability.

When to Call an Expert

Some pump issues are best left to professionals. If you notice persistent problems like unusual noises, excessive vibration, or recurring leaks that standard centrifugal pump troubleshooting doesn’t resolve, it’s time to call a pump specialist. Experts have the tools and knowledge to perform in-depth diagnostics and address complex damage. They can help you avoid costly downtime by recommending repairs or replacements tailored to your system’s needs.

Contact American Stainless Pumps for Support

Having trouble maintaining or troubleshooting your centrifugal pump? At American Stainless Pumps, we provide commercial stainless steel pumps and expert guidance to keep your operations on track. 

Contact us today to learn more!

If you’re researching pumps, you’ve probably come across terms like “single-stage” and “multi-stage.” But what do they mean, and how are they different? The main difference is how many impellers they use and the pressure they can achieve. Here’s everything you need to know. 

What is a Single-Stage Centrifugal Pump?

A single-stage centrifugal pump features one impeller mounted on a pump shaft. This impeller is responsible for drawing fluid into the pump and imparting energy to move it through the system.

Features of Single-Stage Pumps:

• Simplicity - The straightforward design makes them easier to maintain and operate.
• Cost-Efficiency - Fewer components typically result in lower upfront and maintenance costs.
• Performance - Best suited for low to moderate pressure applications.
• Applications - Water supply systems, HVAC systems, General industrial uses

Limitations:

Single-stage pumps are not ideal for applications requiring high-pressure output, as the energy imparted by the single impeller may not be sufficient.

What is a Multi-Stage Centrifugal Pump?

A multi-stage centrifugal pump uses two or more impellers in series to pressurize fluid incrementally. Each impeller increases the energy of the fluid before passing it to the next stage, effectively multiplying the pressure generated by the pump.

Features of Multi-Stage Pumps:

• High Pressure Capability - By stacking impellers, these pumps can achieve significantly higher pressures.
• Efficiency - Designed for systems that require high head (vertical height of fluid transfer).
• Applications - Boiler feed systems, High-rise building water supply, Mining and dewatering operations

Limitations:

Multi-stage pumps are typically more complex and expensive than single-stage pumps. They often require more maintenance due to the increased number of components.

Performance Comparison:

Looking for reliable stainless steel pumps that can handle anything? Reach out to ASP and let’s find the perfect fit for you!

How They Work in Series and Parallel Configurations

When one pump can’t meet system requirements, multiple pumps can be configured in series or parallel to achieve the desired pressure or flow rate. Both single-stage and multi-stage pumps can be used in these setups.

Pumps in Series

In series, the discharge of one pump feeds into the suction of the next, increasing the pressure (head) without changing the flow rate significantly.

How It Works: Each pump adds energy to the fluid, raising the pressure progressively.

Pumps in Parallel

In parallel, multiple pumps share the same suction and discharge lines, increasing the flow rate while maintaining similar pressure.

How It Works: Each pump adds to the total flow rate as the fluid splits at the inlet and recombines at the outlet.

Choosing Between Single-Stage and Multi-Stage Pumps

The decision depends on your system’s specific needs:

1. Pressure Requirements - For high-pressure applications, a multi-stage pump is the better choice.
2. Flow Rate Needs - Single-stage pumps are typically more suitable for high flow rates at lower pressures.
3. Budget & Maintenance - If simplicity and lower costs are priorities, single-stage pumps are more appropriate.
4. Space Constraints - Multi-stage pumps often require more installation space.

Get the Right Pump for Your Application

Both single-stage and multi-stage centrifugal pumps have unique strengths, and selecting the right one depends on your application’s requirements. At American Stainless Pumps, we offer a range of customizable centrifugal pumps designed to meet diverse industry needs.

Contact us today to learn more about our products or to discuss your fluid-handling challenges. Our team of pump experts is ready to assist!

Centrifugal pumps are among the most widely used pump types in industrial applications due to their simplicity and efficiency. They rely on centrifugal force to move fluids through a system, making them ideal for transferring liquids in a variety of industries, including manufacturing, water treatment, and food processing. 

But how does a centrifugal pump work, and what are its key components? This guide will break it down step by step.

Centrifugal pumps are often chosen for their ability to handle:

• High flow rates with consistent pressure.
• Continuous operation with minimal maintenance.
• Customizability to fit specific needs, including material choices like stainless steel, cast iron, or bronze for compatibility with different fluids.
• Varying flow rates and pressure conditions.

Centrifugal Pumps are often the most cost effective pump for an application, with both low upfront costs and little to no maintenance required when compared to other types of pumps, especially all positive displacement pumps. 

Key Components of a Centrifugal Pump

Before understanding how a centrifugal pump works, it’s important to familiarize yourself with the main pump components:

Impeller: A rotating component with vanes or blades that accelerates the fluid outward.

Impellers come in three main types: open, semi-open, and enclosed. Open impellers are simple and ideal for fluids containing solids but are less efficient. Enclosed impellers, by contrast, are more efficient and suited for clean liquids. The choice of impeller depends on the specific application requirements.

Casing: A stationary housing that directs the fluid into the pump and collects it after it leaves the impeller. 

Casings can be designed as concentric casings, with a volute or with diffusers, and their geometry is critical for pump efficiency. Special coatings or materials, such as stainless steel, may be used for the casing to resist corrosion or abrasion in demanding environments.

Concentric casings are used in low flow (less than 200 gpm) or high pressure (higher than 75 psig) pumps.  Volutes are most common in larger pumps where flows are high relative to the pressure.  Diffusers are used most often in high head pumps where more than one impeller is needed for very high pressures.

Suction and Discharge Ports: The suction (inlet) port allows fluid to enter, while the discharge (outlet) port directs it out of the pump.

The orientation and size of these ports are determined by the pumps flow rates and the need to connect to the piping systems. Standardized flange connections help ensure the pump integrates seamlessly into existing setups.

Pump Shaft: Connects the impeller to the motor or drive mechanism.

In larger pumps, the shaft’s alignment is crucial to prevent vibration and wear. High-precision bearings are used to support the shaft and ensure smooth operation.

Mechanical Seal or Packing: Prevents leakage around the rotating shaft.

Mechanical seals are preferred in modern pumps because they minimize leakage and reduce maintenance requirements compared to traditional packing systems. Specialized seals, such as double or cartridge seals, are available for handling hazardous or abrasive fluids.  Packing is rarely used in pumps today.

How Does a Centrifugal Pump Work?

The operation of a centrifugal pump can be summarized in three main steps:

1. Fluid Entry (Suction)

Fluid enters the pump through the suction port, a critical stage influenced by pressure dynamics. To draw the fluid into the pump, a low-pressure zone is created at the eye (center) of the impeller. This low-pressure area is typically generated by the impeller’s rapid rotation, which reduces static pressure at the impeller’s eye relative to the atmospheric or system pressure at the suction port.

The pressure differential forces the fluid into the pump. For this to occur efficiently, it is essential to maintain a continuous flow without cavitation, which happens when the suction pressure falls below the fluid’s vapor pressure. Proper suction line design, including adequate pipe diameter and minimal bends, is key to optimizing fluid entry and preventing disruptions.

Be sure to check the pumps required net positive suction head (NPSHr) is satisfied by the available suction pressure (NPSHa).  If there is not enough suction pressure at startup the pump will cavitate, make a lot of noise and eventually destroy the impeller.

2. Acceleration (Impeller Rotation)

Once the fluid enters the pump, it reaches the rotating impeller, which is the primary energy-transferring component. The impeller blades accelerate the fluid radially outward through centrifugal force. This outward movement imparts significant kinetic energy to the fluid, increasing its velocity.

The impeller’s design – including blade curvature, diameter, and rotational speed – directly affects the pump’s performance. For example, the vane angles of the impeller blades will determine whether the pump has relatively high efficiencies and relatively low NPSHr. The impeller’s material must also match the application to resist wear, corrosion, or temperature extremes.

3. Conversion of Energy (Casing)

As the high-velocity fluid exits the impeller, it enters the volute or diffuser within the pump casing. Here, the casing plays a pivotal role in converting the fluid’s kinetic energy into pressure energy (also known as head).

• Volute Design: A spiral-shaped casing gradually increases in cross-sectional area, slowing the fluid velocity while raising its pressure.
• Diffuser Design: A series of stationary vanes surrounding the impeller reduces velocity more systematically, ensuring efficient energy conversion with minimal turbulence.

The result is a pressurized fluid stream that exits the pump through the discharge port. The discharge pressure depends on factors like impeller speed, casing design, and the fluid’s density. This high-pressure fluid is then ready to be transported through the system.

Contact American Stainless Pumps Today

At American Stainless Pumps, we deliver high-performance, close-coupled, customizable centrifugal pumps designed to meet the demands of your industry. So, whether you need a standard solution or a tailored design, our pumps will provide the durability and efficiency your operation requires.

Contact us today to discuss your needs and discover how our commercial stainless steel pumps can optimize your processes.

If you want your manufacturing operation to continue running smoothly, you need to be able to select the right electric motors for your applications. Jet pump motors come in all shapes and sizes, and the wrong motor might not only cost you money, but bring your operation to a halt. Unfortunately, many manufacturing leaders aren't sure exactly how to select electric motors, and they aren't even sure what they need for their organization.

So how exactly are you supposed to select the right jet pump motors for your commercial application?

Top Priorities for AC Electric Jet Pump Motors

There are many types of electric motors available, from a wide range of manufacturers. Before you can choose the “right” fit for your needs, you should nail down your priorities.

Typical priorities for buying jet pump motors include:

• Specialization/application. Are you going to use this pump motor for a [MB3] water pump? Or a commercial dishwasher pump? Or something else entirely? If you use a motor in the wrong application, it could cause devastating results[MB4] . Even in a best-case scenario, it's going to compromise your productivity and temporarily interfere with your ability to keep things running. In a worst-case scenario, you could be a major safety hazard, threatening your entire workforce.
• Reliability/quality. Obviously, you'll also need to think about reliability and quality. Even within the same category, some motors are strictly better than others. They can withstand harsher conditions, they don't need as much maintenance, and they could last for years longer than their counterparts. All other factors being equal, it's important to choose the most reliable, highest quality motor you can afford.
• Price. Speaking of affordability, you'll need to think about prices as well. This is especially true if you're buying multiple jet pump motors for your systems. Choosing the cheapest pump motor on the market usually isn't ideal, since it will force you to compromise on other factors. But at the same time, it's a good idea to compare cost so you can get the best deal on a pump motor for your specific application.

Key Motor Elements to Consider

Centrifugal pumps, fire sprinkler pumps, chiller pumps, and commercial dishwasher pumps are just a few of the types of pumps that could need a motor to function properly. Your application is going to dictate what type of motor you need.

These are some of the most important considerations:

Specific application needs.

One of the first things you'll need to think about is your specific application and its motor needs. For example, do your motor need to be compatible with a Variable Frequency Drive (VFD)? Does your motor need to be able to withstand a certain ambient temperature? Does your motor need to fit into a specific physical envelope? What size do you need and how much horsepower is required to meet your overall system’s needs?

Environment.

Some motor enclosures are more resistant to humid and/or hot environments than others. In general, the more protection against the elements your motor offers, the more expensive it will be. A totally enclosed fan cooled (TEFC) motor or Washdown Duty motor will often prevent your motor from failing prematurely due to water damage, but you’ll need to consider the specific application and how vulnerable your motor is. Consider consulting with one of our experts for more information.

Pump efficiency.

Some motors are more energy efficient than others. Though not always the case, higher efficiency motors can be more expensive, so this is a tradeoff you'll need to consider. In many cases, higher efficiency components end up paying for themselves, but the math depends on your specific application, the duty cycle of the motor, and how long you plan on using them. Consider consulting with one of our experts for more information.

Construction materials.

Jet pump motors can be made from a wide range of materials, each of which has advantages and disadvantages. Some motor materials are more resilient, some are more cost effective, and some are particularly suited to specific applications. Consider your options carefully and choose the best fit for your needs.

Manufacturer.  

Next, consider the manufacturer of the motor. Two motors that are otherwise identical may have very different levels of reliability due to how they were manufactured and quality checked. It's important to work with a manufacturer that you trust, and one with a reputation for quality work. American Stainless Pumps, Inc has decades of experience with several manufacturers, across multiple factories. We can help you select the best motor for your application.

Maintenance requirements.

Research the maintenance requirements of the jet pump motors you're considering. More complex jet pump motors and jet pump motors in more demanding applications are typically going to require more maintenance, which is something that needs to factor into your equations.

Availability.

You may also need to think about availability. If there are supply chain issues or other economic variables that interfere with the availability of jet pump motors, your first choice may not be immediately available. If you have urgent needs, you may be forced to make a compromise.

Cost.

Finally, you'll need to think about cost. This is the last item on the list because you may not have much wiggle room in what type of pump motor you buy. It's important to prioritize application specificity, quality, and type above price. Only then can you start conducting price comparison analyses in pursuit of the best deal.

There are a lot of factors to consider here, some of which may be beyond the scope of your current understanding. That's why it pays to work with a pump motor expert, who can help you evaluate your needs and choose the right pump motor for your manufacturing company.

Are you ready to buy stainless steel jet pump motors for your stainless steel pumps, chiller pumps, or other commercial applications? The best course of action is to talk to an expert who can help you find the perfect fit for your needs. 

If you’re ready to get started or if you’re interested in a free quote, contact us today!

Commercial pumps play an important role in a variety of industrial settings, so it's important to find the right products, made from the best possible materials. In many ways, stainless steel is advantageous over materials like cast iron, but what is it exactly about stainless steel that makes it such a powerful material for commercial pumps?

Advantages of Stainless Steel Pumps Over Plastic

We can start by comparing stainless steel pumps to their plastic counterparts. What are the advantages of stainless steel over plastic in this application?

• Durability. Different pumps and different applications may have different requirements, but most industrialists are always looking for something durable. Stainless steel is one of the most durable materials available, and it's much more durable than plastic. This allows stainless steel pumps to withstand more wear and tear and handle much more intense environments.
• Longevity. Partially as a byproduct of this, stainless steel offers superior longevity. Your stainless steel pumps are going to last much longer than plastic ones. If you're trying to get the most out of your investment, and make sure your pumps last for many years, stainless steel is likely the right option.
• Chemical and corrosion resistance. People popularly choose stainless steel for kitchen appliances in part because of its corrosion and chemical resistance. Plastics come in many varieties, and there are some designer plastics that are capable of resisting specific chemicals, but even these specially engineered plastics pale in comparison to stainless steel. That's because stainless steel naturally resists a wide range of chemicals and corrosive substances naturally, making it far more versatile and in many cases, more robustly resilient.
• Strength and integrity. Engineers love stainless steel because of its strength and structural integrity. You probably understand this intuitively, as plastic is designed to be somewhat flexible and malleable. Comparatively, stainless steel is stronger and more rigid, and it's far less likely to deform or crack when experiencing mechanical stress. This advantage makes stainless steel far superior to plastic in any heavy duty application.
• Temperature tolerances. You likely know that plastic has the potential to melt, or at least deform, under high temperatures. It also has a tendency to become brittle when experiencing extreme low temperatures. Comparatively, stainless steel has much higher temperature tolerance, and it's capable of withstanding both extreme highs and extreme lows without melting, warping, or becoming brittle.
• Environmental resistance. Generally, stainless steel is better than plastic at resisting environmental conditions. For example, plastic can easily be degraded by UV radiation or saltwater, but stainless steel is resilient to these elements.

Advantages of Stainless Steel Pumps Over Cast Iron

As you can imagine, cast iron has some critical advantages over plastic as well. So what makes stainless steel commercial pumps better than cast iron?

• Corrosion resistance. For starters, stainless steel pumps are more corrosion resistant than cast iron. If you're dealing with an application that involves a hostile environment or corrosive fluids, stainless steel is a better option. For example, in open impellers, cast iron has a tendency to bind up after accumulating rust, eventually leading to pump and motor failure.
• Lighter weight. Compared to cast iron, stainless steel is much lighter compared to its strength. Generally, this makes stainless steel a more versatile material for pumps, and it simultaneously makes stainless steel pumps easier to handle and install.
• Durability. Cast iron is a highly durable material, but stainless steel is arguably even more durable. It can take a more intense beating, and it's significantly less prone to cracking and breaking.
• Longevity. Just as in our comparison to plastic, stainless steel has more longevity. Because of its strength, durability, and other qualities, it's likely going to last much longer than a comparable cast iron pump. You'll also have fewer maintenance needs by upgrading to stainless steel.
• Hygiene and cleanliness. Stainless steel is also known for its hygiene and easy cleanability. It's one of the best materials for applications in industries where hygiene is crucial, such as food, beverage, and pharmaceutical industries. Comparatively, cast iron pumps are more susceptible to contaminants due to the porous nature of cast iron – and they're much harder to clean as well.
• Aesthetics and overall quality. Some people prefer stainless steel for pumps simply because of its aesthetic attributes. Stainless steel is smoother and more visually appealing than cast iron, which makes it the best option in any public-facing or high-end installation. Additionally, the sleek, smooth surface of stainless steel can lead to efficiency improvements.

Are There Downsides for Commercial Stainless Steel Pumps?

So are there any downsides for commercial stainless steel pumps?

The short answer is yes. In some contexts, stainless steel pumps are more expensive to purchase compared to pumps made from other materials such as plastic or cast iron. They’re also heavier than plastic pumps, making them unsuitable for some niche applications. Also, stainless steel is corrosion resistant, not corrosion immune; stainless steel pumps can’t stand up to chlorinated water or sea water in the long term. 

Still, stainless steel pumps are highly advantageous in most situations. 

The Bottom Line for Stainless Steel

So what's the bottom line here?

When it comes to commercial pumps, stainless steel is superior to cast iron and plastic in nearly all applications. It offers practically no downsides, and is the best material to choose if you want:

• A lightweight, relatively inexpensive, strong material. Stainless steel is incredibly strong, considering its weight, it's relatively inexpensive, and yet, it's also highly versatile.
• Corrosion, chemical, and environmental resistance. Stainless steel is also resistant to corrosion, various chemicals, and various environmental hazards, including extreme temperatures. If you need your pumps to be tough, stainless steel is the obvious answer.
• A long life. People also choose stainless steel for pumps they need to last. Stainless steel is relatively low maintenance, and it can last for decades with proper care.

Are you looking for commercial pumps? Are you unsure about the “best fit” for your needs? Our engineers can help guide you to find the perfect solution – so reach out for a free consultation today!

Every centrifugal pump needs a way to prevent the product liquid from leaking past the rotating drive shaft. The sealing method can be as simple as packing rope impregnated with graphite into a “packing box” or as complex as enclosing the entire pump in a chamber (mag drive or canned motors). The most common sealing method is a mechanical seal.

What is a Mechanical Seal?

A mechanical pump seal is a leakage control devices typically found on rotating equipment. They prevent the leakage of liquids from escaping into the environment.

The centrifugal pump mechanical seal relies on the product liquid to cool and lubricate the seal faces, preventing damage, with small amounts of vapor escaping. For abrasive or non-lubricating liquids, a “barrier fluid” may be needed to protect the seal faces. 

Basic Components of a Mechanical Pump Seal

The simplest mechanical seal consists of a “stationary face” attached to the pump housing and a “rotating face” attached to the rotating shaft. Both faces must be sealed to the pump via flexible “boots,” o-rings, or other means to prevent leakage. These boots are typically made of elastomers such as rubber (BUNA), EPR, or Viton. In some cases, flexible metal bellows or Teflon (though difficult to install) may be used.

How Does a Mechanical Seal Work?

Metal components keep the seal intact and provide spring pressure to maintain face contact. These parts are usually 316SS but can be made from other corrosion-resistant metals when needed.

A vast majority of centrifugal pumps will pump water in some varied conditions, possibly in combination with an antifreeze and some antibacterial additives. Since water by itself is not a very good lubricant (especially at high temperatures), the seal faces need to provide some lubricity of their own so that when they touch at startup or shutdown, the faces will not tear themselves up. This is usually accomplished by making one of the seal faces out of carbon or by some material impregnated with carbon. The other seal face is often a harder material that will resist wear from the carbon face, such as a ceramic or silicon carbide, or solid metal.

Note that although water is the most common liquid pumped, the different additives used can make a huge difference in the type of seal required. Relatively clean water, even when combined with glycol, is easy and inexpensive to seal, whereas dirty water or water with lots of additives can be very difficult. The difference is in the abrasiveness and lubricity of the liquid. If when you rub a sample between your fingers you can feel the lack of lubricity, or if your liquid has lots of salts or other dissolved solids, you may need a more complicated and expensive mechanical seal.

Selecting the Right Mechanical Seal for Your Application

Clean Water Mechanical Seal

For non-abrasive water, a basic seal is sufficient. The stationary face is typically ceramic, sealed with a Buna boot or o-ring. The rotating face is often carbon/graphite, also sealed with a Buna boot or o-ring. The spring and metal parts are 304SS or 316SS.

Water with Salts, Abrasives, or Additives

Water with any salts, abrasives, or additives is much harder on mechanical seal faces. When the mechanical pump seal is operating properly, small amounts of liquid enter the space between the two faces. As the liquid travels from the high-pressure side of the face to the low-pressure side, the liquid heats up and vaporizes. While this vaporization is needed to cool and lubricate the faces, it also leaves any salts or other solids in the space between the seal faces. These deposited solids are very abrasive and will accumulate over time and may quickly erode the faces (particularly the softer carbon face).

The simplest and cheapest solution for mildly abrasive liquids is to upgrade the seal faces to materials that can resist abrasives better than the inexpensive carbon/ceramic combination used for clean liquids. The least expensive harder material is usually silicon carbide, but other ceramics/metals are used. The downside of silicon carbide or any other hard material occurs when they run dry, even momentarily during startup and shutdown. Any period of dry running can cause wear and heat buildup and may cause the mechanical pump seal to fail. (In severe cases, the heat will melt the elastomeric parts). This dry running problem is significantly reduced when the silicon carbide faces are impregnated with carbon/graphite, but the problem is not eliminated. Depending on many variables, the seal with impregnated faces can only run dry for a short time before failing, but eventually, the seal will fail from heat buildup.

Other solutions for sealing abrasive liquids include flushing the seal faces with a clean liquid, but this option requires special seals (such as a double seal) and special flushing piping. The cost of this option gets expensive fast and may require a much larger, more expensive pump and seal combination.

Water at High or Low Temperatures

As water temperature gets lower than 32°F or higher than 212°F, the mechanical seal materials may need to be upgraded. Low temperatures usually need EPR elastomers to handle the cold, and higher temperatures may need Viton. Extreme temperatures may also require that the standard ceramic be replaced with the much tougher silicon carbide or other metal faces. Ceramic faces are very susceptible to thermal shock, and a sudden change in the temperature of the liquid can shatter the seal faces.

Food Grade Seals

Centrifugal pump seals used in food processing must meet sanitary requirements. These typically use Viton elastomers, 316SS metal parts, and other food-safe materials. Many food-grade seals are positioned outside the pump for easy daily cleaning, requiring specialized pump designs.

Liquids other than Water

Non-water liquids may require specialized centrifugal pump seals. Toxic or flammable liquids often demand double seals, barrier fluids, and specific flushing systems to protect both the seal and the environment. These advanced types of mechanical seals for pumps increase complexity and cost but are essential for safety and compliance. Consulting with a pump or seal specialist is recommended for these applications.

Pumps That Do Not Require a Mechanical Seal

If your liquid is very hard to seal or very dangerous, you may want to consider a “sealless” pump. The three most common types of sealless pumps are:

1. Mag Drive Pumps
2. Canned Rotor Pumps 
3. Vertical Cantilever Pumps

Mag Drive Pumps

A Mag Drive Pump uses magnets to drive the pump in a contained shell. One set of Magnets spins on an outside cylinder attached to the motor. Another set of magnets spins on an inside cylinder attached to the pump. The two sets of magnets are separated by a thin, non-metallic shell that keeps the pump liquid inside the shell. 

The problem with this arrangement is that there are lots of bushings and sleeves needed to support the pump shaft and the impeller. These bushings and sleeves are exposed to the pumped liquid, so any abrasives can kill the pump quickly. Repairing or replacing these bushings and sleeves is very difficult and very expensive and only adds to the cost of an already expensive pump. This pump is very useful for clean but dangerous liquids.

Canned Rotor Pumps

Canned rotor pumps take the sealless concept further by enclosing both the motor and pump in a sealed housing, eliminating the need for external magnets. However, they are highly sensitive to abrasive liquids, which can cause expensive damage. These pumps are ideal for certain hazardous or high-temperature applications.

Vertical Cantilever Pumps

Vertical cantilever pumps are well-suited for handling abrasive liquids. The motor is positioned above the liquid, and a long shaft extends down to drive the impeller. Bearings are kept out of the liquid, preventing wear. However, these pumps require additional space and structural support, and longer shaft lengths can reduce efficiency.

Contact American Stainless Pumps

At American Stainless Pumps, we specialize in high-quality stainless steel pumps designed for durability and efficiency. We also offer pump motors, pump components, seal kits, and more.

Contact us today to speak to a pump specialist.