Self-Priming Pump

What is Self-Priming Pump?

A self-priming pump is a liquid pump that can automatically prime itself and remove air when it starts or restarts pumping. This is possible because the pump body already contains some liquid, which is trapped by close-tolerance working parts to prevent it from returning to the suction side when the pump is not in use. The pump can then use this liquid to draw in more fluid and remove air, creating a continuous flow.

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ZX Series Self-Priming Centrifugal Pump

Advantages of Self Priming Pumps

Entrained Gas Handling

Due to their ability to vent suction lines they can handle fluids with entrained gasses, priming for up to 30 mins without drawing liquid.

Easy to Maintain

They are far easier to maintain than a submersible pump which is immersed in the liquid and may need confined space training to maintain.

Reliable

Their designs are not based on use with other accessories meaning they do not rely on additional valves to function which can sometimes fail.

Robust

As the motor and cable are not immersed in fluids, they are longer lasting and less exposed to pumping mediums when handling corrosive or aggressive fluids.

How A Self-Priming Pump Works

Some types of pumps are engineered to be automatically self-priming. Pumps of this nature feature close tolerance working parts that trap fluids in the pump's body, preventing them from returning from the discharge side of the pump to the suction side when the pump is not in operation.

In these types of pumps, the constant presence of fluid in the pump's body allows the pump to better handle what are called "air pockets". Air pockets are an accumulation of air bubbles in the pump's working mechanism, which can impair proper pump operation.

Most liquid pumps used in the sanitary processing industries are centrifugal-type pumps.
Centrifugal pumps are:
Simple
Sturdy
Relatively inexpensive
Ideal for pumping water and other low viscosity fluids such as CIP solutions under circumstances where suction conditions are difficult.

For these types of low viscosity fluids, a V-type centrifugal pump design is often preferred, featuring a vacuum pump and positive seal that is located close to the discharge port. This allows a V-type centrifugal pump to readily pull a vacuum until it is full of fluid.

However, standard centrifugal pumps are not designed to be self-priming. Unlike the pump types already described, standard centrifugal pumps do not trap liquids when not in use — although engineered modifications to the pump's housing may allow some of these types of pumps to be self-priming.

With centrifugal pumps, the pumping action occurs when an impeller is rotated in a liquid within a cavity or chamber of the pump, displacing the liquid and forcing it to flow into the discharge port of the pump via centrifugal force.

Fluids typically enter the pump at the center of the impeller and are discharged via a port on the outer perimeter of the pump's body. The impeller is often directly coupled to the pump's motor, in what is called a monoblock design.

Air is the primary enemy of this type of pump. When a standard centrifugal pump encounters air pockets, it can become "air bound", and refuse to operate. Air intrusion into standard centrifugal pumps is typical, as these types of pumps don't feature tightly coupled pumping mechanisms such as gears or screws and have no seals between the suction and discharge sides of the pump.

This blending allows the resulting mix to move readily through the pump's body on initial start-up, removing the air and aiding product flow on the suction side of the pump. The process liquids and any entrained air move toward the impeller, and normal pump operations commence.

In comparison to a standard centrifugal pump, what's notable in the design of a self-priming centrifugal pump is that it features a liquid reservoir built into the body of the pump, typically either above or in front of the impeller.

This reservoir allows the pump to rid the pump's body and suction line of air during the priming cycle, replacing it with liquid from the reservoir that is blended into the residual air. The "self-priming" capability of this type of centrifugal pump comes from the ability of the reservoir to retain liquid after its very first prime.

Applications for Self-Priming Pumps

Self-Priming pumps can be used in a variety of applications, here are a few examples along with some of our previous projects:

ATEX Fluid Transfer

Rather than having an ATEX submersible pump immersed in a flammable liquid, having a surface mounted pump which primes from pits can be far safer, and lead to fewer issues as the motor and cable glands are not immersed within the flammable liquid. One ATEX self-priming pump we provided in the past was for a distillery to bulk transfer Methanol at 95% concentration.

Pit Emptying

Units are great at pit emptying eliminating the need for confined space entry.

Solid Handling

Such designs are typically engineered to handle solids and can often transfer these comfortably. One of our previous projects that required solid handling was for a wheel wash system at a quarry.

Wastewater Handling & Dewatering

Units can be kept in situ with hoses ported around site for dewatering various areas rather than having to relocate pumps each time an area needs dewatering saving time, labour, and resources.

Tanker Offloading

Self priming pumps ensure that tankers, and storage tanks are stripped of fluid, maximising fluid transfer as well as eliminating vapour locking in suction lines.

Varying inlet / Tidal Conditions

For transferring from tidal rivers or the sea to on land, having a pump which can handle fluctuating intake conditions can help eliminate any possible issues caused by changes in fluid suction height.

Self-Priming vs. Non-Self-Priming Pumps: Which Is Right for You?

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.

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.

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.

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.

Choose a Self-priming Pump When

Frequent Priming Is Needed
Air Entrainment Is a Concern
Continuous Flow Is Critical

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.

Factors to Consider When Selecting a Self-Priming Pump

Before selecting the an application there are a few key factors you should consider:

Size of Solids - To ensure the impeller can sufficiently handle any particles without clogging.

Fluid Viscosity - This often determines pump speed, possible flow rate and if other devices are required such as a follower plate to help feed the pump.

Priming Distance - Not just the horizontal, and Vertical runs of pipework but also any accessories such as bends, strainers or valves which can add pressure losses and determine possible priming distance.

Fluctuating Fluid Levels - If water is being drawn from the sea, tidal rivers, or tanks where water levels change, care must be taken to ensure that the designed flow is possible at various heights without encountering issues due to a lack of suction pressure such as vortexing or cavitation due to insufficient NPSHA.

Priming Time - That the time taken to evacuate the suction pipe is checked and that the unit does not overheat or take too long to start up. During priming, fluid recirculates within the casing, creating a vacuum. As it recirculates it begins to heat up, and if left too long, it can heat above the temperature rating of gaskets and seals within the pump head.

Power Options - How to power the pump whether it be by single, or 3 phase, hydraulically driven or by engine.

Close Or Long Coupled - Whether a cost-effective unit is required or a robust long coupled unit.

Trailer Mounted, Baseplate or Pontoon Mounted - Whether your pump will stay in situ, require a trailer for portability across your land / domestic roads or installed on a pontoon for dewatering there are many options to consider.

Controls - How the pump will start, stop, and operate as part of your system, and whether certain events may be triggered..

Our Factory

Shandong Magtech Machinery Equipment Co., Ltd is a professional manufacturer of vacuum pump, water pump, slurry pump and other industrial pumps. In line with the concept of "science and technology leading, quality oriented, and reputation first", the company has made great efforts to innovate and forge ahead, so that excellent results have been achieved in the production and operation, new product development and other aspects of the company. Main products are SZ, SZB, SK, 2BV, 2BEA, 2BEC series water ring vacuum pump, roots water ring vacuum unit, closed cycling vacuum unit, WLW vertical oil-free reciprocating vacuum pump, etc. SH, S, OS, IS, ISG, LG, DL, DA1 series water pump.

FAQ

Q: What is a self-priming pump?

A: Self-priming pumps are a specific type of liquid pump designed to have the required liquid inside the cavity or pump body necessary to start the pumping process. This offers the potential for increased operating efficiencies in process plants where pumps are used for a variety of repeated yet intermittent operations.

Q: What is an example of a self-priming pump?

A: In principle, all positive displacement pumps are self-priming. In particular, this includes rotary gear pumps (internal and external), lobe pumps, vane pumps and diaphragm pumps.

Q: What is the advantage of a self-priming pump?

A: Self-priming pumps can be operated when not entirely filled, and can automatically overcome any problems when air mixes with the fluid, saving considerable time compared to manually priming the pump.

Q: What is necessary for self-priming to take place?

A: What is necessary for self priming to take place? Explanation: For self priming to take place, pump casing is necessary. This helps to evacuate air in normal conditions. Explanation: Centrifugal pumps with an internal suction stage are called as self priming pumps.

Q: What is the difference between self-priming and non-priming pumps?

A: A non-self-priming pump requires external assistance to remove air from the suction line and create a vacuum, allowing it to draw fluid from a source. Unlike self-priming pumps, non-self-priming pumps cannot operate without a constant fluid flow and a foot valve to maintain the necessary vacuum for priming.

Q: Which type of centrifugal pump does not require priming?

A: Self-priming centrifugal pumps are ideal for pumping slightly contaminated liquids with or without solid parts. Self-priming pumps are used in systems where priming can sometimes be difficult and where a regular end suction centrifugal pump doesn't work.

Q: Is a self-priming pump better?

A: 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.

Q: Where are self-priming pumps used?

A: Self-priming pumps are used in various industrial and commercial facilities, from steel mills, power plants, and sewage treatment facilities to wineries, breweries, and more. Common applications include: Pumping water, fuels, clear or gray water, raw sewage, industrial wastewater, and more. Liquid transfer systems.

Q: Do you need to prime a self-priming pump?

A: Even a self priming pump has to be primed initially. Even a self-priming pump has to be primed prior to the first operation. No matter the manufacturer, there is a priming chamber (integral or external) or some portion of the volute that will require filling prior to startup.

Q: Does a self-priming pump require a foot valve?

A: There is also no need to have a foot valve in the system as the primary unit is always capable of lifting the process fluid to the pump regardless of the air in the system and the pump will only start when properly primed.

Q: How long can a self-priming pump run dry?

A: This means the pump can run dry without fluid for a limited amount of time – typically 30 minutes. It is always recommended to avoid dry running with centrifugal pumps if possible as the pumped fluid is used to lubricate and cool internal parts.