Category: Blog

When it comes to the field of engineering, the concept of a gerotor is widely used in the production of various machines and devices, but what exactly is a gerotor pump and how does it work?

In this blog, we’ll provide a comprehensive overview of the gerotor pump, including its design, functionality, advantages, disadvantages, and applications.

What is a Gerotor Pump?

A gerotor pump is a type of positive displacement pump consisting of an outer gerotor, an inner gerotor, and a housing. 

As you can see in the illustration below, the outer gerotor has one tooth more than the inner gerotor and has a convex cycloidal profile on its external surface. The inner gerotor has a concave cycloidal profile on its internal surface and is mounted off-center within the outer gerotor.

The two gerotors are positioned such that the convex and concave surfaces are in contact with each other. 

The housing, which is typically made of cast iron or aluminum, contains the rotors and provides the necessary support.

How Does a Gerotor Pump Work?

A gerotor pump operates by trapping fluid between the rotor teeth and the housing, creating a seal. As the rotors rotate, the fluid is carried around the outer rotor and into the inner rotor, where it is then discharged. The amount of fluid pumped per revolution is dependent on the size and shape of the rotors and the housing, as well as the speed of rotation.

Gerotor Pump Advantages & Disadvantages

In this section, we explore the advantages and disadvantages of gerotor pumps to help you determine whether a gerotor pump is the best choice for your specific pumping needs.

Advantages of Gerotor Pumps

Gerotor pumps offer several advantages over other types of pumps, including:

1. High Efficiency: Gerotor pumps offer high volumetric efficiency, meaning they can move a high volume of fluid per revolution. They have volumetric efficiencies of up to 98%, making them one of the most efficient types of displacement pumps.
2. Low Noise & Vibration: Gerotor pumps operate with low noise and vibration levels, making them ideal for applications that require quiet operation. They generate less noise and vibration than other types of pumps, such as gear or vane pumps.
3. Compact Size: Gerotor pumps are relatively compact and lightweight compared to other types of positive displacement pumps. They take up less space, making them ideal for applications where space is limited.
4. High-Pressure Capabilities: Gerotor pumps can operate at high pressures, with maximum pressure ratings of up to 10,000 PSI.
5. Self-Priming: Gerotor pumps are self-priming, meaning they can operate without the need for external priming. This makes them ideal for applications where the fluid being pumped may contain air or gas.

Disadvantages of Gerotor Pumps

As with any type of pump, there are disadvantages. The main disadvantages of gerotor pumps include:

1. Limited Viscosity Range: Gerotor pumps have a limited range of viscosity that they can pump effectively. They’re best suited for pumping low to medium-viscosity fluids, such as oil, fuel, or water. They’re not well-suited for pumping high-viscosity fluids, such as molasses or honey.
2. Limited Suction Capability: Gerotor pumps have a limited suction capability, which means they can’t draw fluid from a deep source or a high elevation. They require a positive head of fluid to operate efficiently.
3. Wear & Tear: Gerotor pumps can experience wear and tear over time due to the close tolerances between the rotors and the housing. This can lead to decreased efficiency and increased maintenance costs.

Gerotor Pump Applications

Gerotors are used in a variety of industrial and automotive applications, particularly in hydraulic systems where precise and efficient fluid flow is required. They can also be useful in other non-industrial applications, such as power steering systems for vehicles, due to their low sound levels compared to rotary pumps operating at higher speeds (noise can be an issue when running machines close to people).

Other common applications of gerotors include:

• Engine oil pumps and fuel pumps in automobiles and other internal combustion engines
• Lubrication systems in compressors, gearboxes, and other industrial machinery
• Hydraulic elevators and lifts in industrial and commercial buildings
• High-pressure hydraulic systems in aerospace and defense applications
• Vacuum pumps and blowers in a wide range of industries
• Positive displacement compressors for gasses and other compressible fluids
• Hydraulic motors for driving conveyor belts, mixers, and other industrial machinery
• Coolant pumps for engines and other heat-generating equipment
• Braking systems in off-road vehicles and heavy equipment

These are just a few of the many applications for gerotors, which are valued for their efficiency, reliability, and ability to handle a wide range of fluid viscosities. 

Gerotor Pumps: Efficient & Versatile Pumping Systems

Overall, gerotor pumps offer a reliable, quiet, and efficient pumping solution for a wide range of applications. 

When selecting a pump for your application, it’s important to consider your specific pumping needs, along with the advantages and disadvantages of the pump types you’re considering to determine the best fit. 

Ready to learn more? Check out our other resources!

Functionally, pumps are simple. 

When it comes to increasing flow rate and pump efficiency, not so much. 

Determining how to maintain a high flow rate and efficiency is essential to ensure your pump is minimizing wear and tear and performing at full capacity.

Before we dive into improving pump efficiency, let’s dive into what pump efficiency is and how it works.

 

Understanding Pump Efficiency

First, let’s go with the most basic question on the topic: what is a pump?

Pumps are devices that move fluids, liquids, or gases, in a certain direction, typically in applications like engines or irrigation systems. Maintaining efficiency is essential to reduce energy consumption and costs.

 

What is Pump Efficiency?

On a high level, pump efficiency refers to how well a pump is able to convert one energy form to another – if the power entering the pump is equal to the power leaving the pump, the pump would reach 100% efficiency (something that’s impossible).

 

What is the Pump Flow Rate?

Flow rate is the volume of fluid that moves through a certain time period – typically calculated and measured using flow meters. It’s often confused for efficiency. 

Pump efficiency and flow rate should be determined before choosing a pump, so it’s the best fit for your application.

 

5 Tips on Improving Pump Flow Rate and Efficiency

Because they go hand-in-hand, both pump flow rate and efficiency need to be at the forefront of your mind when working with pumps. Here are five tips to get started with improving pump flow rate and efficiency:

1. Pump selection
2. Maintaining the pump
3. Check the impeller
4. Install control systems
5. Pump in parallel 

1. Pump Selection

Different pumps have different flow rates and efficiencies, so choosing a pump specific to your application is necessary. 

How do I choose a pump?

Pumps can come in many different shapes and sizes, but there are four main types of pumps:

• Gerotor pumps
• Hydraulic pumps
• Mechanical pumps
• Electric pumps 

Engineers sometimes get in the mindset that bigger is better, which isn’t always the case. Oftentimes, pumps end up being oversized by 20-30%. This can cause unnecessary energy consumption as the pump would require more power from the motor than expected, therefore reducing efficiency. 

How do I fix an oversized pump?

Trimming the impeller is a way to reduce the pressure and energy consumption caused by oversized pumps – causing efficiency improvements.

 

2. Maintaining the Pump

Imagine never changing the oil in your car. Eventually, the car would stop running because the engine would succumb to damage caused by friction. 

The same concept applies to pumps. If you aren’t regularly applying lubrication to your pump, it will create friction and pump wear, which can cause efficiency losses from 10-25%. To prevent losses, pump maintenance is necessary.

How do I know when my pump needs maintenance?

Think of maintenance like your car inspection. Every component needs to be checked at regular intervals for wear and tear to ensure the pump is functioning properly. While wear and tear are inevitable, maintenance can help prevent costly, unexpected breaks in your pump. 

What does pump maintenance consist of?

• Replacing worn parts like impellers
• Checking on the bearings
• Making sure enough lubrication is flowing throughout
• Inspecting any seals in the pump 

When this maintenance isn’t improving performance and efficiency, it may be time to replace the pump.

 

3. Check the Impeller

Checking the impeller frequently outside of maintenance is necessary. The impeller is the part of the pump that actually moves the fluid. If it’s damaged, the pump could reduce the flow rate and efficiency, or even stop the pump completely.

 

4. Install Control Systems

Pump control systems regulate the flow rate and optimize energy efficiency. If only one pump is necessary to reach the desired flow rate, the control system will turn off the other pump until it’s needed again. 

The most efficient way to control the pump flow rate is through Variable Frequency Drives (VFDs). VFDs control the motor’s speed to ensure it’s just enough for the flow requirements. 

Since this control system doesn’t use any more energy than what’s needed, energy consumption and wear and tear on the pump are greatly reduced, making the pumps more efficient than most. VFDs are commonly found in the agricultural industry in irrigation systems where efficiency is crucial.

 

5. Pump in Parallel

If you’re only using one pump, chances are it isn’t at full efficiency and using an excessive amount of energy. When you implement a smaller, second pump, it takes on some of the workload, resulting in two pumps operating at optimum capacity. 

Additionally, if one of your pumps stops working or is undergoing maintenance, you still have another pump available for operation.

 

What Should Your Pump Efficiency Rating Be?

Pump efficiency varies based on the type and size of pump you choose, as well as the motor. If you have a higher-quality pump with regular maintenance, efficiency can be above 90%. However, if you have a smaller pump or a pump that isn’t well maintained, it could be much less efficient. 

The type of engine or motor you choose can also offer different levels of efficiency. While internal combustion engines have an efficiency of around 75-93%, AC motors typically run around 90% efficiency.

Whether the size of your pump or type of motor is affecting your efficiency, a good efficiency rating should maintain around 70-90%.

 

How to Calculate Pump Efficiency and Flow Rate

There are many ways to calculate pump efficiency and flow rate, some of the calculations include the following:

Getting Started with Maximizing Pump Efficiency

There are a variety of factors that impact the efficiency of your pump, and knowing where to start to increase your pump efficiency can be difficult. 

Once you find the reason for inefficiency, getting started right away is essential to start saving costs, time, and energy spent.

 

Start Improving Your Pumps

When getting started on investing in efficiency, it’s best to consult with an expert to ensure you’re on the right track. Reach out to one of ours at Nichols Portland today.

 

Today, the focus on environmentally friendly solutions is more vital than ever, manufacturing isn’t excluded. 

In manufacturing, designing for recyclability/remanufacturing involves producing parts that can easily be broken down into reusable materials at the end of their life cycle. 

In this blog, we’ll discuss why it’s essential to have a sustainable pump design and how to achieve it.

The Importance of Sustainable Pump Design 

You may be wondering, why does sustainable pump design matter? 

Pump manufacturers use large quantities of raw materials to produce their parts. If manufacturers were only to use new, unused materials, they would solely rely on natural resources. Instead, using recycled materials allows manufacturers to have a nearly unlimited supply of materials. 

Solely using new materials isn’t only unreliable, it could lead to increased costs, missed opportunities for advancement, and negatively impact your brand’s image.

Cost Increases 

Cost increases are inevitable when manufacturers solely use virgin resources. Sourcing raw materials for pumps is expensive and requires many resources.

Missed Opportunities for Advancement

If raw materials were the only option, there would be several missed opportunities for advancement. Reusing materials creates a circular economy, where these materials are used to their full potential. This can lead to innovative manufacturers using resources for products they wouldn’t have thought of before.

Impacts on Your Brand’s Image

There are countless pump manufacturers to choose from – consumers and businesses are looking for someone that stands out and is environmentally conscious. 

If your pump manufacturing doesn’t reuse materials, it could be perceived as less sustainable and eco-friendly, negatively impacting your brand image.

3 Design Considerations for Producing Recyclable Pump Components

Sustainable pump design is essential for long-term success. There are three design considerations for producing recyclable pump components to keep in mind. 

1. Material selection 
2. Design for disassembly
3. Proper labeling and storage

1. Material Selection 

When designing your pump, think about how recyclable and eco-friendly the materials are.

While it is essential to evaluate each material’s properties carefully to ensure they’ll meet your

performance requirements, small adjustments can be made to either start with recycled content or enable the material to become recycled later on in its life cycle. 

If you select the wrong material, you may have to dispose of it and start again, leaving waste behind. For example, ferrous powdered metals are inherently sustainable, as a good portion of powder originates from iron and steel scrap. 

Design your pump so it can easily be taken apart at the end of its life, and make sure the end user knows to return this to iron and steel scrap – and you have introduced a material that can be recycled over and over again. A similar approach can be used for other metals, such as copper, or even plastics.

2. Design for Disassembly

When designing your part, design as if you were taking it apart the next day. You’ll want to use three approaches when designing:

• Modular design approaches include creating distinct modules that are easily removable and replaceable. This will allow you to repair your pump, rather than replace it. Pump manufacturers typically sell replaceable pump components, so repairs will be a fraction of the cost compared to replacing.
• Standardized interfaces involve designing pump components to follow industry standards and regulations. Using standardized parts will make it easier in the future if you’re looking to upgrade or replace parts.
• Universal fastening mechanisms should easily be able to disassemble and reassemble. Using screws, bolts, and other fasteners that can be taken apart with universal tools will make taking apart and putting together pumps much easier.
  

3. Proper Labeling

Proper labeling is an essential part of designing for recyclability but is commonly overlooked. Materials should always be stored in the correct places, either non-recyclable or recyclable to ensure they aren’t mixed. 

It’s important to label subcomponents wherever possible to allow the end user to easily drop them into a recycling bin at the end of the component’s life. Plastic materials often follow a standardized labeling method and including such markings within tooling comes at zero additional cost to the manufacturer.

By taking these three factors into consideration, you’ll meet your pump’s performance requirements as well as sustainability goals.

Challenges & Limitations of Sustainable Pump Design

When implementing sustainable practices, there are two main concerns that go hand-in-hand – long-term costs and upfront investment. 

The first question in nearly any business decision is “What’s the cost?” When designing for recyclability, ideally, the pump design should be cost-effective. However, depending on the materials needed or advanced technologies, such as new equipment, the upfront investment may be costly. Fortunately, most sustainable manufacturing methods increase your long-term savings.

 

The Future of Manufacturing – A Focus on Sustainability 

Without sustainable pump design, manufacturers won’t see long-term success. The increased demand for eco-friendly products as well as the availability of natural resources ensures that sustainable pump design is necessary.

Start Designing for Recyclability

Incorporating sustainable methods into your production can be a difficult task. Reach out to one of our experts at Nichols Portland to start designing for recyclability.

Consistency, efficiency, and versatility. 

When asked what sets gerotor pumps apart from other pumps, these are the answers. 

Gerotor pumps have been around for more than a century as a preferred method of pumping fluids. In this blog, we’ll discuss the gerotor pumps advantages and disadvantages, as well as when gerotor pumps are best.

What Are Gerotor Pumps?

Before diving into the advantages and disadvantages of gerotor pumps, understanding what gerotor pumps are and how they work is essential. 

We’ll start with the basics. What are gerotor pumps?

They’re positive displacement pumps used to pump fluids of nearly any viscosity. Broken down, gerotor pumps consist of rotating inner and outer gears.

As the inner and outer gears rotate, the space between the inner and outer gear profile increases creating suction and drawing fluid into the pumping chambers. As rotation continues, the space between the inner and outer gear profile decreases and the fluid is pushed out.

 

Advantages of Gerotor Pumps

There are several positive displacement pumps to choose from. What are the advantages of gerotor pumps?

1. Consistent, constant fluid distribution
2. Simple operation & functionality
3. High efficiency
4. Extreme versatility from gerotors

1. Consistent, Constant Fluid Distribution

Regardless of viscosity, a gerotor pump maintains a constant and consistent fluid distribution. Gerotor pumps pump oil, water, or even fuels with minimal leakage, maintaining a near-

constant volume of fluid displacement per revolution across a broad range of outlet pressure.

 

2. Simple Operation & Functionality

While gerotors are complex structures, the functionality is pretty straightforward. Gerotor pumps function in either direction and are relatively quiet. With only two moving parts, the chance of parts breaking or malfunctioning is much less than other pumps – resulting in low maintenance and repair costs.

As a low-cost, quiet way to pump fluid, gerotor pumps are highly sought after in applications for vehicles and aircraft.

 

3. High Efficiency

Due to their design, gerotor pumps are highly efficient. With large teeth that allow fluid to flow smoothly, there is low vibration during the process – resulting in minimal wear and tear as well as lower energy consumption.

The overall compact size of the gerotor pump also ensures efficiency. These pumps only hold a specific amount of fluid, so the energy to operate is much less than in larger pumps.

 

4. Extreme Versatility from Gerotors

The versatility of gerotors is one of the main advantages of gerotor pumps. Gerotors have the ability to be mounted directly on an existing shaft or be driven via the outer rotor. 

They can be packaged easily into a large system, such as an engine or a transmission. Due to their ability to build suction pressure, they need not be submerged in a fluid sump – in fact, gerotors are an excellent choice for lifting liquids from a tank and pulling it through hoses or internal channels.

On the other hand, internally, a single gerotor set can accommodate multiple inlet flow streams operating at different pressures.

 

Disadvantages of Gerotor Pumps

Although gerotor pumps are ideal for several applications, there are three main disadvantages to the process: 

1. Unable to process solid inputs
2. Limited scalability
3. Fixed clearances

 

1. Unable to Process Solid Inputs

While gerotor pumps handle fluids of nearly any viscosity, they can’t process solid inputs. The gears of gerotor pumps are meant to rotate smoothly and quickly. If a solid is inputted, the gears can get stuck or shift, resulting in potential damage, wear and tear, and inefficient processes.

 

2. Limited Scalability

All pumps have size limitations. No matter the size of the pump, the amount of fluid can’t exceed the pump cavity’s volume capacity.

How does this affect the flow rate? 

For any application, the maximum flow rate that the pump can supply is its RPM

multiplied by its displacement. A pump that is spinning too slow will be extremely

inefficient, or fail to support its internal journal bearings. 

Speeding the pump up, a limit will be reached when the tip speed of the gear set is so high that fluid does not fill the inlet. It is crucial to identify the optimal speed for a gerotor pump – or conversely, the optimal gerotor pump for a given application.

 

3. Fixed Clearances

In gerotor pumps, the distance between the inner and outer rotor and the fixed surfaces on

either side is known as axial clearance. Inner and outer rotors also have a radial clearance. These clearances are defined when a gerotor pumping element is designed into a pocket in a

pump housing.

When the clearance is too large, a significant quantity of fluid can leak from high pressure regions to low-pressure regions, resulting in decreased volumetric efficiency. When the clearance is too small, especially in relation to the pumped fluid’s viscosity, much of the torque input to the gear set is used for simply overcoming the fluid drag, resulting in decreased mechanical efficiency.

Pro Tip! In pumps, the chance of decreased efficiency and increased leaks is high. Regularly keeping up with pump maintenance is important to avoid leaks and decreases in efficiency.

 

When Gerotor Pumps Are Best

When choosing a pump for an application, it’s usually based on ease of packaging and optimizing efficiency.

Since gerotor pumps are compact to package, energy efficient, and quiet, they are the preferred pump choice in many industries, most notably aerospace and automotive. 

For applications in both, fuel and oil need to be pumped through engine systems with minimal environmental impact, and high efficiency.

 

Gerotor Pumps Moving Forward

As a consistent, efficient way to pump fluids for over a century, gerotor pumps will remain a viable option in many industries for years to come. 

With its efficiency and other advantages, gerotor pumps bring a new level of optimization to an application.

 

Ready to Choose a Pump? 

Weighing your options when selecting a pump is difficult. Consult with one of our specialists to ensure you’re making the correct decision. 

Positive displacement pumps are pivotal elements of several industries, performing essential tasks that involve moving fluids at constant volumes. However, their performance and longevity significantly depend on maintenance. Properly maintaining your positive displacement pump is crucial to ensuring it operates efficiently and lasts for a long time. This blog post will cover the primary considerations and steps for positive displacement pump maintenance.

 

Understanding Positive Displacement Pumps

Before diving into the maintenance aspect, it’s necessary to comprehend what a positive displacement pump is. Positive displacement pumps move fluids by trapping a specific amount and forcing (displacing) that trapped volume into the discharge pipe.

 

Routine Maintenance

Regular maintenance is key to the longevity of positive displacement pumps. Here are a few routine maintenance activities to ensure your pump’s optimal performance:

1. Lubrication: The parts of the pump need regular lubrication to function smoothly. Check the conditions of bearings and seals for any signs that lubrication is inadequate. 
2. Seal Inspection: Inspect pump seals for leaks regularly. If there are any leaks, this could signal wear and tear, requiring seal replacement. In the absence of any leaks, check the visible sealing surface for wear marks.
3. Vibration analysis: Regularly checking for excessive vibration can help predict potential failures. Unusual vibrations may indicate imbalances, misalignments, or mechanical wear in the pump components.
4. Temperature monitoring: Keep a regular check on the operating temperature of the pump, and in areas where evidence of excessive heat could lead to wear or catastrophic failure, such as gear teeth. Overheating can lead to severe damage, reducing the life of your pump.

Preventative Maintenance for Positive Displacement Pumps

Preventative maintenance involves tasks performed to avoid potential failures. Here are a few key preventative measures:

1. Regular inspections: Regularly inspect all pump components, such as the motor, seals, bearings, and pumping elements.
2. Proper installation: Proper installation plays a significant role in the pump’s overall life. Ensure the pump is correctly aligned and all parts are tightened as per manufacturer’s recommendations.
3. Scheduled servicing: Stick to the servicing schedule as advised by the pump manufacturer. Regular servicing involves cleaning, inspecting, and if required, replacing worn-out components.

Corrective Maintenance

Despite the best preventative practices, pumps may eventually fail. Corrective maintenance comes into play when there are pump issues that need immediate attention. Here are a few measures for corrective maintenance:

1. Replacement of parts: If any component of the pump shows signs of severe wear and tear, it should be replaced promptly.
2. Correcting misalignments: Misalignment is a common issue that can cause excessive vibration, leading to premature wear and tear. A pump’s bearings and pumping elements should move smoothly, without any hitching or unusual noise. Correcting misalignments promptly can prevent further damage.
3. Troubleshooting: Any operational issues should be dealt with promptly. This involves identifying the root cause of the problem and addressing it.

Maintaining Your Pump

Proper maintenance of your positive displacement pump can significantly enhance its lifespan and efficiency, thus reducing downtime and saving costs in the long run. Always remember that preventative maintenance is more cost-effective than corrective maintenance. Keep a maintenance schedule and stick to it for optimal performance of your positive displacement pump.

Stay on top of your pump maintenance and you’ll have a machine that keeps your operations running smoothly and efficiently for a long time. Remember, an ounce of prevention is worth a pound of cure, especially when it comes to maintaining industrial equipment like positive displacement pumps.

Ready to learn more? Check out our other resources.

Imagine trying to sip a milkshake through a tiny straw – it takes much more effort than sipping water through the same straw, right?

This simple example illustrates the challenges of handling fluids with different viscosities, a factor that plays a critical role in the performance of positive displacement (PD) pumps. 

Join us while we delve into the fascinating world of fluid dynamics, exploring how viscosity affects pump performance and providing tips for optimizing pump selection and operation based on fluid properties. So grab your favorite milkshake (or any viscous fluid), and let’s start!

 

Effects of Viscosity on Positive Displacement Pump Performance

In this section, we’ll unravel the intriguing effects of viscosity on pump performance, from temperature effects to power requirements and cavitation risks. Viscosity can affect positive displacement pumps in the following ways:

1. Temperature Effects on Viscosity
2. Power Requirements
3. Cavitation Risk

Temperature Effects on Viscosity

The viscosity of liquids decreases rapidly as they heat up, and vice versa. Some commonly pumped fluids, such as gear oil, have viscosities that increase exponentially with temperature. 

It’s essential to understand the operating temperature range of the pumped fluid so that the best method of handling the viscosity changes can be discussed. For example, cold temperature additives are used for fuels like diesel. Newer oils, such as those used in electric vehicle lubrication, are formulated with viscosity enhancers.

 

Power Requirements

Higher viscosity fluids require more energy to pump due to increased resistance to flow. As a result, the power requirements for the pump will increase, leading to higher energy consumption and operational costs. It’s crucial to accurately estimate the power requirements when selecting the pump motor to avoid overloading and premature motor failure.

 

Cavitation Risk

Cavitation occurs when the fluid pressure drops below its vapor pressure, leading to the formation and subsequent collapse of vapor bubbles. High-viscosity fluids can increase the risk of cavitation in positive displacement pumps, as they require more suction head to overcome the resistance to flow. Insufficient suction head can lead to pressure drops, resulting in cavitation, which can cause pump damage and reduced performance.

 

Strategies for Handling High-Viscosity Fluids

Now that we’ve delved into the challenges of pumping high-viscosity fluids, it’s time to discover the secrets to successfully navigating the complex world of high-viscosity fluid handling. From selecting the perfect pump type to optimizing pump speed and exploring innovative solutions like fluid heating, we’ve got you covered.

Strategies for handling high-viscosity fluids include:

1. Pump selection
2. Optimizing Pump Speed
3. Heating the Fluid
4. Properly Sizing Suction Piping

Pump Selection

Choose a positive displacement pump designed specifically for high-viscosity fluids, such as gear pumps, lobe pumps, or progressing cavity pumps. These pumps typically have larger clearances and are designed to handle the increased resistance to flow.

 

Optimizing Pump Speed

Reducing the pump speed can help minimize slip and improve volumetric efficiency when handling high-viscosity fluids. Operating at lower speeds also reduces wear on pump components and lowers the risk of cavitation.

 

Heating the Fluid

For temperature-sensitive fluids, heating the fluid can lower its viscosity, making it easier to pump. This can improve the pump’s efficiency and reduce energy consumption. However, care must be taken not to exceed the fluid’s thermal limits or damage its properties.

 

Properly Sizing Suction Piping

Design the suction piping system to minimize pressure losses, ensuring adequate suction head is available to prevent cavitation. This may include using larger diameter pipes, minimizing bends, and avoiding obstructions.

 

Viscosity Correction for Positive Displacement Pumps

When dealing with fluids of varying viscosities, understanding how to apply viscosity corrections to pd pump performance data is crucial for accurate pump sizing and selection. Here, we explore the concept of viscosity correction, its importance, and the steps to apply these adjustments to PD pump performance data.

 

Steps for Viscosity Correction

Positive displacement pump performance characteristics, such as flow rate, pressure, and efficiency, can be significantly affected by fluid viscosity. Applying viscosity corrections to pump performance data ensures that the pump is accurately sized and selected for the specific fluid properties and operating conditions, ultimately leading to optimal pump performance and reliability.

Steps for viscosity correction include:

1. Identify Fluid Viscosity
2. Determining Pump Performance at Reference Viscosity
3. Identify the Appropriate Correction Factors
4. Applying the Correction Factors

Identify Fluid Viscosity

The first step is determining the fluid’s viscosity at the operating temperature. This information can typically be found in the fluid’s data sheet or through laboratory testing.

Determining Pump Performance at Reference Viscosity

Obtain the PD pump performance data at a reference viscosity (usually for water, with a viscosity of 1 centipoise) from the pump manufacturer. This data typically includes flow rate, pressure, and efficiency values.

Identify the Appropriate Correction Factors

Consult the pump manufacturer’s guidelines or charts to identify the correction factors for your specific pump type and fluid viscosity. These factors may include flow rate correction, pressure drop correction, and efficiency correction.

Apply the Correction Factors

Adjust the pump performance data at the reference viscosity using the identified correction factors. This will provide the pump performance data for the specific fluid viscosity:

• Flow Rate Correction: Multiply the reference flow rate by the flow rate correction factor.
• Pressure Drop Correction: Multiply the reference pressure drop by the pressure drop correction factor.
• Efficiency Correction: Multiply the reference efficiency by the efficiency correction factor.

Re-Evaluate the Pump Selection

With the corrected pump performance data, re-evaluate the pump selection to ensure it meets the system requirements for the specific fluid properties and operating conditions.

 

Thixotropic & Shear-Thinning Fluids: Navigating the World of Non-Newtonian Fluids

Thixotropic and shear-thinning fluids exhibit unique viscosity characteristics that can have significant implications for PD pump performance. Let’s explore the behavior of these fluids and reveal strategies for pumping them effectively and efficiently.

Thixotropic Fluids

Thixotropic fluids experience a decrease in viscosity over time when subjected to constant shear stress, and their viscosity returns to its original state once the stress is removed. Common examples of thixotropic fluids include certain paints, gels, and ketchup. When pumping thixotropic fluids, it’s essential to consider the time-dependent viscosity changes, as this can affect the pump’s efficiency and the ability to maintain consistent flow rates.

Shear-Thinning Fluids

Shear-thinning fluids, known as pseudoplastic fluids, decrease viscosity as the shear stress increases. This behavior can be advantageous in PD pump applications because it allows the fluid to flow more easily through the pump under high shear conditions, reducing the energy required for pumping. Examples of shear-thinning fluids include certain polymer solutions, food products like honey, and blood.

Strategies for Pumping Thixotropic & Shear-Thinning Fluids

When pumping thixotropic and shear-thinning fluids, keep the following principles in mind:

1. Pump Selection
2. Optimize Pump Speed
3. Pulsation Dampeners
4. Proper System Design

Pump Selection

Choose a PD pump type suitable for handling non-Newtonian fluids, such as progressing cavity pumps, peristaltic pumps, or lobe pumps. These pumps can provide gentle handling and minimize the potential for fluid degradation due to shear forces.

Optimize Pump Speed

Selecting the appropriate pump speed is crucial for maintaining consistent flow rates and ensuring the proper handling of thixotropic and shear-thinning fluids. Too high of a pump speed can cause excessive shear forces, while too low can lead to insufficient flow rates and potential settling or separation issues.

Pulsation Dampeners

Adding pulsation dampeners to the pump system can help minimize pressure fluctuations and ensure a smoother flow, especially when handling thixotropic fluids with time-dependent viscosity changes.

Proper System Design

Designing the piping system and other components to minimize pressure losses and shear forces can enhance the performance of PD pumps handling non-Newtonian fluids. This may include larger diameter pipes, minimizing bends, and avoiding obstructions.

 

Conquering PD Pump Performance Challenges

Understanding the impact of viscosity on positive displacement pump performance is essential for efficient and reliable operation. By considering the fluid properties and selecting the appropriate pump type, speed, and system design, you can optimize the pump’s performance and extend its service life, even when handling high-viscosity fluids.

Have more questions? Contact one of our experts!

Fluid enters. Flows. Fluid leaves. 

Functionally, that’s all that a pump is.

However, with complex and unique design features, the pump variations available are countless. One of the most widely known is positive displacement pumps.

What is a Positive Displacement Pump?

A positive displacement pump takes a specific amount of fluid and pushes it to its outlet. 

How do positive displacement pumps move fluid?

A cavity in the pump expands and contracts to cause displacement, which pushes the fluid from the inlet to the outlet. 

Pump designs vary, but most pumps can be divided into two categories: reciprocating and rotary.

Reciprocating Pumps

Reciprocating pumps move fluids through displacement by using a back-and-forth motion. 

There are three common types of reciprocating pumps:

• Piston pumps
• Plunger pumps
• Diaphragm pumps

Piston and plunger pumps are functionally the same with slight design differences. These pumps will typically have a piston or plunger inside that shifts back and forth in a larger cylinder. This movement creates a vacuum-like suction on one side of the pump that pulls fluid in. When the piston or plunger moves to the other side, fluid is compressed and pushed through the outlet. 

On the other hand, diaphragm pumps use a flexible membrane to draw fluid into a pumping chamber, and push it out.

Rotary Pumps

Unlike the back-and-forth motion in reciprocating pumps, rotary pumps use rotating mechanisms, such as gears to pump and transfer fluid. These pumps create a vacuum-like suction to draw in the fluid, carry it within the teeth of the gear, and transfer it to the outlet.

Although the basic functionality remains the same, the three types of rotary pumps vary in design:

1. Gear pumps use two or more gears that drive each other within a pumping chamber to create pockets of pumped fluid.
2. Vane pumps move its vanes in and out of a rotor to create spaces that move fluid out of the pump.
3. Lobe pumps use multiple rounding lobes that create pockets of fluid volume that are moved from inlet to outlet. 

While these three rotary pumps have very different designs, all positive displacement pumps have the same functionality – moving fluid from the inlet to the outlet.

Positive Displacement Pump End-Use Applications

Positive displacement pumps transfer fluids accurately and without a broad operating range. As a result, these pumps are widely used: 

• Oil and gas industry
• Agriculture
• Food and beverage
  

Oil and Gas

As a reliable, accurate way to transfer fluids, these pumps are becoming an increasingly popular solution for efficiency. Positive displacement pumps frequently are found transferring crude oil, petroleum products, and natural gas.

Agriculture 

With their ability to handle a vast range of fluids and operating conditions, positive displacement pumps are the perfect fit for agriculture. These pumps are most commonly used in irrigation systems, but also transfer chemicals and work in water supply systems.

Food and Beverage

For the food and beverage industry, control is the main focus. Positive displacement pumps transfer fluid at a controlled, measurable rate while maintaining sanitary conditions.

Rotary lobe pumps and diaphragm pumps are two of the most frequently used pumps in the industry. Rotary lobe pumps transfer fluids such as dairy, fruit juices, and sauces. Diaphragm pumps are used for things such as processing ingredients.

Limitations of Positive Displacement Pumps

While positive displacement pumps have their advantages, they do have their limitations: 

1. Less efficient than centrifugal pumps
2. Handling low viscosity
3. Maintenance
   

1. Less Efficient Than Centrifugal Pumps

As a positive displacement pump uses mechanical energy to push each volume of fluid against a system restriction, it generally uses more energy to move a given volume of fluid than a centrifugal pump, which has much less internal mechanical resistance. 

The conditions of service may determine that a centrifugal pump is better suited to a certain application.

2. Handling Low Viscosity

Since positive displacement pumps are designed for moving highly viscous fluids, working with low-viscosity fluids can result in slippage and leaks.

Slippage occurs when the fluid pumped leaks back into the clearance of the pump, instead of the outlet. Most positive displacement pumps also count on the fluid to provide a fluid film that prevents contact of the meshing surfaces and supports journal bearings. As a result, the pumping process decreases efficiency and increases wear and tear on the pump.

Although positive displacement pumps can pump these fluids, to avoid slippage centrifugal pumps are the preferred alternative. 

Positive Displacement Pumps vs. Centrifugal Pumps  Centrifugal pumps move fluid by using impellers to transfer rotational energy. Fluid enters the pump and lands on the impeller axis, then centrifugal force pushes the fluid through the impeller’s vane tips and towards the pump outlet. While both centrifugal and positive displacement pumps work to pump fluids, there’s one major difference – the viscosity. Centrifugal pumps are most efficient when pumping low-viscosity fluids in low-pressure environments. Choosing one pump over the other heavily depends on this key difference.

3. Maintenance

Think of a puzzle. When you have thousands of pieces, the likelihood of losing a piece while putting it together is nearly inevitable – resulting in an unfinished project.

The same concept applies to pumps. 

Typically in pumps, the internal design all fits together and relies on the other parts. If one stops working, the whole pump will break down. 

Spending extra time and money on maintenance is critical to ensure one part doesn’t affect the rest of the pump.

Positive Displacement Pumps: Simple, Yet Complex

While simple in function, positive displacement pumps have a complex design. Designed for pumping highly viscous fluids efficiently, positive displacement pumps have been and will continue to be a preferred method in many industries. 

Which Type of Positive Displacement Pump is Best?

Choosing the right positive displacement pump is a tough decision. 

Reach out to one of our technicians to simplify your decision.

Pumps play a vital role in many industries, facilitating the transfer of fluids in a wide range of applications. While there are numerous pump types available, they can be broadly classified into two categories: positive displacement (PD) pumps and dynamic pumps.

Here, we explore the key differences between positive displacement pumps and other common pump types, focusing on their operating principles, advantages, disadvantages, and typical applications.

Operating Principles of Positive Displacement & Dynamic Pumps

First, let’s begin by examining how PD pumps and dynamic pumps work:

Positive Displacement Pumps: Operating Principle

PD pumps transfer fluid by capturing a fixed volume of fluid within a cavity and then mechanically displacing it into the discharge pipe. This process is achieved through reciprocating or rotary elements, such as pistons, diaphragms, gears, or screws. Examples of PD pumps include gear pumps, diaphragm pumps, piston pumps, and progressive cavity pumps.

Dynamic Pumps: Operating Principle

Dynamic pumps, also known as kinetic pumps, transfer fluid by imparting kinetic energy to the fluid through the action of a rotating impeller or a spinning disk. This kinetic energy is then converted into pressure energy, propelling the fluid through the discharge pipe. Examples of dynamic pumps include centrifugal pumps, axial flow pumps, and regenerative turbine pumps.

Comparing Positive Displacement & Dynamic Pumps

Here, we contrast selection criteria for PD pumps and dynamic pumps in various key areas, including flow rate and pressure, viscosity, efficiency, pulsation and shear sensitivity, self-priming capability, and maintenance and wear.

Flow Rate & Pressure

PD pumps deliver a consistent flow rate regardless of the discharge pressure, making them ideal for applications that require precise dosing or constant flow. In contrast, the flow rate of dynamic pumps is highly dependent on the system pressure, with the flow rate decreasing as the pressure increases.

Viscosity

PD pumps can handle fluids with a wide range of viscosities, including high-viscosity fluids which can be challenging for dynamic pumps. Dynamic pumps, particularly centrifugal pumps, are generally more suited for low to medium-viscosity fluids, as high-viscosity fluids can result in reduced efficiency and increased wear.

Efficiency

Positive displacement pumps typically have higher volumetric efficiency than dynamic pumps, especially when dealing with high-viscosity fluids or high-pressure applications. Dynamic pumps may offer higher overall efficiency for low-viscosity fluids and low-pressure applications.

Pulsation & Shear Sensitivity

PD pumps can generate pulsating flow, which may not be suitable for certain applications, such as those involving shear-sensitive fluids or where a smooth constant flow is required. However, there are possible pump/porting design options that can minimize the impact of pulsations. Dynamic pumps, particularly centrifugal pumps, generate a smoother flow with less pulsation.

Self-Priming Capability

Most PD pumps have self-priming capabilities, allowing them to handle fluids with entrained gases or operate under suction lift conditions. Dynamic pumps typically require a flooded suction or an external priming system to function effectively.

Maintenance & Wear

PD pumps generally have more moving parts and can be more susceptible to wear, particularly in applications involving abrasive or corrosive fluids. However, with proper pump selection and maintenance, you can minimize wear and tear. Dynamic pumps, especially centrifugal pumps, tend to have simpler designs with fewer moving parts, which can translate to lower maintenance requirements.

Which Pump Type Will You Choose?

Selecting the right pump type for a specific application requires a thorough understanding of the differences between positive displacement and dynamic pumps. By considering the aforementioned factors, you can make informed decisions that optimize system performance, efficiency, and reliability.

Ultimately, the choice between a positive displacement pump and a dynamic pump will depend on the unique requirements of each application, with each pump type offering distinct advantages and disadvantages suited for different scenarios.

Ready to learn more? Check out our resources page.

Positive displacement (PD) pumps are essential in numerous industries, including oil and gas, food processing, and pharmaceuticals, providing consistent and efficient fluid transfer. However, one common issue that can impact the performance and lifespan of your PD pump is cavitation. 

Here, we explore the phenomenon of PD pump cavitation, its causes, consequences, and effective strategies to mitigate its occurrence.

What is Positive Displacement Pump Cavitation?

Cavitation is a phenomenon that occurs when the pressure in the pumped fluid falls below the fluid’s vapor pressure, causing the formation of vapor bubbles or cavities. As these bubbles travel through the pump, they collapse when they reach regions of higher pressure, releasing energy as shock waves. These shock waves can cause significant damage to the pump components, reduce efficiency, and increase noise and vibration levels.

What Causes Cavitation in Positive Displacement Pumps?

The main causes of cavitation in positive displacement pumps include:

1. Insufficient Net Positive Suction Head (NPSH): NPSH is a measure of the energy available in the fluid at the pump inlet relative to the fluid’s vapor pressure. When the NPSH available (NPSHa) is less than the NPSH required by the pump (NPSHr), cavitation is likely to occur. 
2. High Viscosity Fluids: Pumping high-viscosity fluids can lead to increased resistance to flow, resulting in a pressure drop at the pump inlet, increasing the risk of cavitation.
3. Inadequate Suction Piping Design: Improper design or installation of the suction piping system, including undersized piping, excessive pipe length, numerous bends or elbows, and partially closed or obstructed valves, can cause pressure losses and contribute to cavitation.
4. Blocked or Clogged Filters/Strainers: Obstructions in filters or strainers can cause a pressure drop at the pump inlet, increasing the risk of cavitation.
5. Pump Operating at High Speeds: When positive displacement pumps operate at high speeds, the time available for fluid to fill the pump chamber decreases, which can cause a pressure drop and promote cavitation.
6. Inappropriate Pump Selection: Using a pump unsuitable for the specific application or fluid properties can lead to inadequate performance and an increased risk of cavitation.
7. High-Altitude Operation: Pumps operating at higher altitudes have a lower atmospheric pressure, which reduces the available NPSH and increases the likelihood of cavitation.
8. High-Fluid Temperature: Elevated fluid temperatures can lower the fluid’s vapor pressure, making it more susceptible to cavitation.
9. Air or Gas Entrainment: The presence of air or gas in the fluid being pumped can reduce the fluid’s effective NPSH, increasing the risk of cavitation.

Ways to Address PD Pump Cavitation

The good news is that there are steps you can take to keep your PD pump running smoothly, including:

Ensure Adequate Net Positive Suction Head 

To prevent cavitation, it is crucial to maintain an adequate NPSH. This can be achieved by reducing the suction lift, increasing the suction pipe diameter, or using a booster pump to increase the available pressure.

Select the Appropriate Pump

Choose a PD pump specifically designed for the fluid properties, system requirements, and operating conditions of your application. Consult with your pump manufacturer or engineers for proper pump selection.

Proper Pump Installation

Ensuring your PD pump is correctly installed, aligned, and connected to the piping system can help reduce the risk of cavitation.

Regular Maintenance

Regularly inspecting and maintaining your pump and its components can help identify early signs of cavitation and take corrective measures before significant damage occurs.

Monitor Pump Performance

Regularly monitoring pump performance indicators, such as flow rate, pressure, and temperature can help identify potential cavitation issues and enable proactive maintenance or system adjustments.

Determining the Speed of Pump Cavitation

Determining the speed at which a pump will begin to cavitate is a fairly complicated process. Numerous factors contribute to pump cavitation, including:

• Vapor pressure of the fluid (water, oil, gasoline)
• Available atmospheric pressure (sea level, higher altitude)
• Pressure losses in the inlet lines (length, diameter, surface roughness, momentum changes, turbulent flow, laminar flow)
• Pressure losses in the pump itself (length, diameter, surface roughness, momentum changes, turbulent flow, laminar flow, bypass circuit)
• Rotor geometry (diameter, chamber volume as a function of rotation, carry-over volumes)
• Pump’s operation speed

To determine the speed of pump cavitation, engineers use a combination of analytical methods, computer simulations, and experimental testing. Computational fluid dynamics (CFD) analysis can be a valuable tool to simulate fluid flow and pressure changes within the pump and the system, allowing you to identify potential cavitation risks and optimize the pump design and operating conditions to minimize cavitation. 

In addition, conducting tests on physical pump prototypes and monitoring for signs of cavitation, such as noise, vibration, and reduced pump performance, can help confirm the theoretical predictions and refine the cavitation risk assessment.

Preventing Displacement Pump Cavitation

Understanding and addressing the causes of positive displacement pump cavitation are critical to maintaining the efficiency, reliability, and longevity of your pumping equipment. By following these steps, you can mitigate the risk of cavitation and maximize the performance of your PD pump systems.

Have any other questions on PD pumps or cavitation? – Reach out to one of our experts.