Operators of high-pressure pump equipment are well aware that a pump requires priming prior to operation. When you prime a pump, air is removed from the inlet tube, creating a vacuum and allowing the pump’s power to take up fluid and operate properly. But for jobs that require frequent starts and stops, the manual priming process can become a hassle.
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Some water pumps, such as those used in wells or common sump pumps, are inherently self-priming because they are submerged in water, naturally displacing any air gaps, thanks to gravity. But what about industries that use equipment above a main tank of fluid?
Self-priming plunger pumps are desirable in these applications, especially for commercial uses like cleaning, agriculture, pest control, disinfection, and other industries that use high-pressure pumps. There are things every operator should know before investing in a self-priming pump, however.
Benefits of Self-Priming Plunger Pumps
To prime a standard centrifugal pump requires filling the pump through a priming port, which needs to be done each time it’s used. A main advantage of self-priming plunger pumps is not having to take the extra step of priming it every time you use your equipment, saving significant time and labor. A self-priming pump is also more conducive to handling fluids that might have different viscosities or be more corrosive than water, such as harsh chemicals used in cleaning, lawn care, or fertigation equipment.
A true self-priming pump works against gravity by compressing air to get it to move and draw up fluids. They don’t need to be submerged in liquid or located below a water tank; instead, they can operate laterally or above the level of the fluids being drawn through the pump. The ability to remain mobile and efficiently operate pumps in varying configurations and environments is perhaps the greatest benefit of self-priming pumps.
Troubleshooting Self-Priming Pumps That Won’t Prime
There is a misnomer about self-priming pumps, however. There are still some initial steps that need to be taken before operation. Plus, there are certain conditions where the priming function of a self-priming plunger pump may not operate as it should. Some assume there to be a defect in the pump itself when, in reality, there are likely outside factors that need to be addressed.
Wondering how to prime a pump that’s self-priming? The following are some troubleshooting tips for self-priming pumps.
Conduct Initial Priming
A pump that has some liquid inside will prime a lot easier than one that’s completely dry. Before operating a brand new pump, it’s recommended to perform an initial priming step according to the manufacturer’s directions. If your pump remains in storage for a long period of time, you may need to perform this step again since any remaining liquid inside may have evaporated.
Check for Improperly Sized Inlet Hose
You want your inlet tube to have the smallest amount of air possible. The longer your inlet hose, the greater amount of air that needs to be displaced and the harder it is for your pump to prime. Likewise, the diameter of the hose makes a difference: the bigger the hose, the more air.
When possible, limit the length of tubing and go with the smallest size possible without creating cavitation. Finding the balance that’s “just right” might take some adjustments along the way.
Check Outlets
Just as important as properly sizing the inlet hose is ensuring there are no restrictions on the outlet. When a self-priming pump is running, it will pump air through itself until it draws the water in. If the air continually goes up against a regulator valve, it won’t have anywhere to go. You need to be able to build up enough pressure to get rid of the air and don’t want any resistance downstream.
Check Fittings
It’s important to ensure there are no leaks anywhere in the system. Check to make sure your suction line is sealed and that all hoses, connections, and O-rings are tight. Imagine trying to drink water through a straw with a hole in it; it’s nearly impossible to draw the water up into your mouth. This same concept explains why a poorly sealed pump system won’t prime.
Adjust Location of the Tank
Consider the location of your tank in comparison to the height of your pump. A pump with a low flow rate that is located adjacent to a tank is relatively easy to prime because the air and fluids just need to go sideways.
That same pump placed several feet above the tank will not only have a long inlet hose with lots of air inside; it will also need to overcome the gravitational pull of the weight of the water. A simple solution is to configure the pump location on the side of the tank rather than on top.
Right-size Your Pump
Priming is generally a larger issue with low flow rates. Some pump models have higher compression ratios than others and are able to create a better vacuum and higher air pressure output. The larger the pump, the farther the plunger moves within it, creating a higher compression ratio (and more power) in the pump chamber.
If you’ve addressed all the initial steps and potential issues with your self-priming pump and it still fails to prime properly upon startup, you might simply need a more powerful pump for your application.
The best way to ensure your self-priming pump operates correctly is to choose the right pump and properly design the system. When designed, configured, and installed correctly with the right fittings, relief valves, hoses, and other plumbing fixtures, a properly sized self-priming plunger pump will prove reliable for years to come.
Pumps play a vital role in an array of industries, from agriculture and manufacturing to water treatment and construction. These mechanical devices move fluids from one place to another, ensuring the smooth operation of countless processes. Among the various types of pumps available, self-priming and non-self-priming pumps stand out as key contenders, each offering distinct advantages and applications. Understanding the differences between these two pump types is crucial for anyone seeking to make an informed decision about which one best suits their specific needs. Let’s understand the complexities of self-priming and non-self-priming pumps to help you choose the right one for your requirements.
What Is a Self-Priming Pump?
A self-priming pump is a type of pump that possesses a unique ability to automatically evacuate air and prime itself, without external assistance, when starting or restarting the pumping process. These pumps achieve priming through a combination of design elements, such as an integrated air and fluid separation chamber or a built-in recirculation system. These mechanisms enable the pump to draw fluid and evacuate air automatically, creating a continuous and reliable flow.
What Is a Non-Self-Priming Pump?
A non-self-priming pump is a type of pump that does not possess the inherent capability to automatically remove air from the suction line or prime itself when starting. Instead, these pumps require manual priming or the implementation of auxiliary devices to ensure proper operation.
Key Differences between Self-Priming and Non-Self-Priming Pumps
Priming Process
Self-Priming Pumps: These pumps are designed with built-in mechanisms to automatically evacuate air from the suction line and initiate pumping without external assistance. They use their own design features, such as recirculation systems or air-fluid separation chambers, to create a vacuum and prime themselves. Self-priming pumps are capable of starting and restarting without manual intervention, making them suitable for applications with intermittent use.
Non-Self-Priming Pumps: Non-self-priming pumps lack the inherent ability to remove air from the suction line and establish suction on their own. They require external priming methods, such as manual filling of the pump casing or the use of priming chambers, vacuum systems, or gravity feed to remove air and create suction. The priming process in these pumps often requires manual effort or additional equipment, which can add complexity to the system.
Efficiency and Energy Consumption
Self-Priming Pumps: These pumps are typically less energy-efficient than non-self-priming pumps. This reduced efficiency is due to the additional energy expenditure associated with their self-priming mechanisms. While these mechanisms are essential for their automatic priming capability, they can introduce some energy losses during operation.
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Non-Self-Priming Pumps: These pumps are often more energy-efficient because they do not have the added energy consumption related to self-priming features. They tend to provide a more direct and efficient transfer of fluid without the need for additional components or processes that may result in energy losses.
Maintenance Requirements
Self-Priming Pumps: Self-priming pumps typically have somewhat higher maintenance requirements compared to non-self-priming pumps. The self-priming mechanisms, such as recirculation systems or air-fluid separation chambers, introduce additional components that need periodic inspection and maintenance. These mechanisms can be prone to wear and tear over time, potentially requiring more frequent servicing.
Non-Self-Priming Pumps: Non-self-priming pumps generally have lower maintenance requirements due to their simpler design. They lack the additional components associated with self-priming mechanisms, which can reduce the likelihood of component wear and maintenance needs. Maintenance tasks are typically more straightforward and less frequent, making them a cost-effective option in terms of upkeep.
Cost Considerations
Self-Priming Pumps: These pumps tend to have a higher upfront cost compared to non-self-priming pumps. This is because they incorporate specialized components and engineering to enable automatic priming, which can increase manufacturing and design expenses. While they may have a higher initial investment, the convenience and advantages of self-priming capabilities can offset this cost over time, especially in applications where frequent priming is necessary.
Non-Self-Priming Pumps: Non-self-priming pumps generally have a lower initial purchase cost. Their simpler design and fewer specialized components contribute to a more cost-effective upfront investment. However, it’s essential to consider the additional expenses associated with external priming methods, such as the cost of priming chambers or vacuum systems, when evaluating the total cost of ownership. In some cases, these external priming requirements can increase the overall cost, especially if they are not readily available in the existing infrastructure.
Pros and Cons of Self-Priming Pumps
Pros
Automatic Priming: Self-priming pumps can automatically remove air from the suction line and initiate pumping, eliminating the need for manual priming.
Versatility: They are adaptable to various environments, making them suitable for applications such as dewatering and water transfer.
Reduced Downtime: Self-priming pumps are less prone to cavitation, a common issue in non-self-priming pumps, which can damage pump components and cause downtime.
Efficiency: While not as energy-efficient as non-self-priming pumps due to their self-priming mechanisms, self-priming pumps still offer reasonable efficiency in many applications.
Cons
Higher Initial Cost: Self-priming pumps often come with a higher upfront cost compared to non-self-priming pumps, primarily due to their specialized design and components for automatic priming.
Maintenance Requirements: They may require more frequent maintenance due to the additional components involved in the self-priming process, which can introduce complexity, and wear and tear.
Energy Consumption: Self-priming pumps tend to consume more energy compared to non-self-priming pumps, which can result in higher operational costs over time.
Not Ideal for All Applications: While versatile, self-priming pumps may not be the best choice for applications where maximum energy efficiency is crucial or when the initial budget is a primary concern.
Choose a Self-priming Pump When
- Frequent Priming Is Needed
- Air Entrainment Is a Concern
- Continuous Flow Is Critical
Pros and Cons of Non-Self-Priming Pumps
Pros
Energy Efficiency: Non-self-priming pumps are often more energy-efficient compared to self-priming pumps because they do not have the additional energy consumption associated with self-priming mechanisms.
Simplicity of Design: They have a simpler and more straightforward design with fewer specialized components, which can reduce maintenance requirements and manufacturing costs.
Lower Initial Cost: Non-self-priming pumps generally have a lower upfront cost, making them an attractive option for applications with budget constraints.
Precise Control: They offer precise control over the priming process, allowing operators to ensure that the pump is properly primed before starting, which can be advantageous in critical applications.
Cons
Manual Priming Requirement: These pumps require external priming methods, which can involve manual effort or the use of additional equipment.
Limited Adaptability: They may not be well-suited for applications with frequent starts and stops or those involving air entrainment, as manual priming can be time-consuming and labor-intensive.
Potential for Cavitation: In applications where there is a risk of cavitation due to inadequate priming, non-self-priming pumps may experience damage to pump components, leading to maintenance and downtime.
Choose a Non-self-priming Pump When
- Energy Efficiency Is a Priority
- Precise Control Is Required
- Budget Constraints Exist
- Continuous Operation Is Not Essential
The choice between self-priming and non-self-priming pumps is a crucial decision that hinges on your specific requirements and the nature of your application. It’s essential to recognize the importance of selecting the right pump to ensure optimal performance, efficiency and cost-effectiveness. In some scenarios, self-priming pumps with their automatic priming capabilities might be the ideal choice, while in others, non-self-priming pumps may offer greater energy efficiency and cost savings.
By carefully evaluating your specific circumstances, you can confidently select the pump that will deliver the best results and maximize the success of your operations.
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