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Maintaining a garden pond or a bigger aquatic pond for commercial purposes requires proper water circulation. This is why you need to invest in a highly reliable pump, whether you have one at home or in a bigger location, like a farm. It is responsible for the oxygen in the water and in contributing to the biofilter of the pond, which is necessary in purifying or cleaning the water. Due to their versatility and ability to handle suspension excellently, centrifugal pumps are a popular choice for many pond operators or fish farm owners. Other types include diaphragm, roller, and piston pumps.

Pump buying considerations

When it comes to buying pumps for your fish pond, you will need to factor in the flow rate and water head or pressure produced by the pump. The flow rate is also known as the output, often determined in liters or gallons. Make sure that you choose one that is a good fit for the size of your pond. A bigger pond will require a more powerful pump, but installing a powerful pump in a small pond often causes problems. A flow rate that is too powerful may stir up sand in the pond, resulting in murkier waters.

The ability of the pump to spurt water at a specific height is known as its water head or water pressure. Prior to buying one, it will be helpful for you to at least estimate how much water head your application will need. This way, you’ll be able to get the best type of pump to match your project. Most fountains and waterfalls require pumps with higher water head.

The advantages of centrifugal pumps

Centrifugal pumps are popular for several reasons. These are versatile and come in many different types. These include standard centrifugal, high pressure, and trash centrifugal pumps. Centrifugal pumps are also high capacity pumps and don’t require as much maintenance as other kinds of pumps. There are also designs of centrifugal pumps which are meant to handle solids, which are recommended for washing down equipment.

The Pentair Water - Flotec - Simer Centrifugal Pump is built for general purpose pumping, whether for ponds, fountains, waterfalls, or pressure sprinkling. This pump comes with rugged cast iron housing, making it perfect for heavy duty use. Buying a versatile and easy-to-use pump is excellent for a wide range of water gardening or clear water applications. With a ready to install pump, you’ll have your pond in stable working condition within minutes.

Water pumps are used mainly to move water for a variety of purposes. From applications requiring standard water flow or movement to applications that need high pressure pumping, water pumps are used across different industries and even at home. A wide range of contractor pumps nowadays work through centrifugal force and are known as centrifugal water pumps. These may be used for a range of applications requiring water transfer and water movement, including garden waterfalls, fountains, and sprinkling.

Types of centrifugal pumps

A centrifugal pump works through an impeller and volute in order to produce the vacuum and pressure needed for water movement. Both the impeller and volute influence the flow of water, as well as its pressure and handling.

These come in different designs, which in turn produce different discharge rates and water pressure. Standard ones are used for different water applications, whether for home or agricultural use. These are also used in different industries. Although these pumps do have limited capabilities when it comes to handling, they are an economical choice for many users. For higher pressure and flow, high pressure centrifugal pumps - with a capacity of producing 100 GPM - are more ideal. These are useful in washing equipment, fire control, and irrigation.

The last type or design is the trash centrifugal pump. Don’t be misled by the name - it’s merely referring to what goes down the pump! With the ability to wash down large amounts of waste, these types of pumps are used widely by many contractors. Trash pumps are usually priced higher than standard centrifugal pumps due to its higher horsepower requirement.

How to choose a good pump

When it comes to choosing a pump, you should consider first of all the volume and pressure requirements of the application as well as the material being pumped. Along with clear water, oil, fertilizer and other chemicals may also be pumped. You will also need to check for horsepower requirements especially in terms of discharge pressure and volume. Centrifugal are known to handle suspension excellently and don’t require high maintenance.

The Pentair Water - Flotec - Simer General Purpose Centrifugal Pump can be used for a variety of water transfer and water circulation purposes, whether for gardens, ponds, or other clear water applications. By using a centrifugal built for versatile purposes, you are assured of successful water transfer and water movement results, for a wide range of residential, agricultural, or industrial applications.

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The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) disclosed recently the inauguration of its latest product section, Fluid Pumps.

The product section was agreed upon in unanimity by AHRI’s Board of Directors at its meeting on November 15, 2009, and will be added to AHRI’s 40 other product sections.
 
“This is an exciting opportunity to bring together manufacturers of fluid pump equipment to address issues of common interest in this growing market, and to establish a dialogue among industry leaders,” - Henry Hwong, AHRI’s Vice President of Product Section Services.
 
The new section was launched in order to meet requests from fluid pump producers for the creating of a forum where common issues can be discussed and solved. The approved range of the section covers the whole array of roto-dynamic centrifugal pumps/circulators used for fluids flow in residential and commercial buildings, mainly used in closed loop heating and cooling systems, domestic hot water recirculation, steam systems, cooling towers, geothermal and solar industries etc.

The water pump impeller on a boat is a crucial piece of equipment that allows the water pump to pump water through the motor to keep it cool. The impeller is a rubber turbine that, when it turns, creates a vacuum in the pump body and draws water through the pump and the rest of the motor. Replacing the impeller is a common maintenance procedure as over time it can become cracked and worn.

The overwhelming majority of contractor pumps use centrifugal force to move water. Centrifugal force is defined as the action that causes something, in this case water, to move away from its center of rotation.

All centrifugal pumps use an impeller and volute to create the partial vacuum and discharge pressure necessary to move water through the casing. The impeller and volute form the heart of the pump and help determine its flow, pressure and solid handling capability.

An impeller is a rotating disk with a set of vanes coupled to the engine/motor shaft that produces centrifugal force within the pump casing. A volute is the stationary housing (in which the impeller rotates) that collects, discharges and recirculates water entering the pump. A diffuser is used on high pressure pumps and is similar to a volute but more compact in design. Many types of material can be used in their manufactire but cast iron is most commonly used for construction applications.

In order for a centrifugal pump, or self priming, pump to attain its initial prime the casing must first be manually primed or filled with water. Afterwards, unless it is run dry or drained, a sufficient amount of water should remain in the pump to ensure quick priming the next time it is needed.
As the impeller churns the water (see figure above), it purges air from the casing creating an area of low pressure, or partial vacuum, at the eye (center) of the impeller. The weight of the atmosphere on the external body of water pushes water rapidly through the hose and pump casing toward the eye of the impeller.
Centrifugal force created by the rotating impeller pushes water away from the eye, where pressure is lowest, to the vane tips where the pressure is highest. The velocity of the rotating vanes pressurizes the water forced through the volute and discharges it from the pump.
Water passing through the pump brings with it solids and other abrasive material that will gradually wear down the impeller or volute. This wear can increase the distance between the impeller and the volute resulting in decreased flows, decreased heads and longer priming times. Periodic inspection and maintenance is necessary to keep pumps running like new.

Another key component of the pump is its mechanical seal. This spring loaded component consists of two faces, one stationary and another rotating, and is located on the engine shaft between the impeller and the rear casing (see figure below). It is designed to prevent water from seeping into and damaging the engine. Pumps designed for work in harsh environments require a seal that is more abrasion resistant than pumps designed for regular household use. Typically seals are cooled by water as it passes through the pump. If the pump is dry or has insufficient water for priming it could damage the mechanical seal. Oil-lubricated an occasionally grease-lubricated seals are available on some pumps that provide positive lubrication in the event that the pump is run without water. The seal is a common wear part that should be periodically inspected.

Regardless of whether the application calls for a standard, high pressure, or trash every centrifugal pump lifts and discharges water in the same way. The following section will point out design differences between these pumps.
Standard Centrifugal Pumps
Standard centrifugal pumps provide an economical choice for general purpose dewatering. A number of different sizes are available but the most common model offerings are in the 2 to 4 inch range with flows from 142 to 500 gallons per minute (GPM) and heads in the range of 90 to 115 feet.

these pumps should only be used in clear water applications (agricultural, industrial, residential) as they have a limited solid handling capability of only 10% by volume.
The impellers typically use a three-vane design (see figure below) and the volute is compact, preventing the passage of large solids. The rule of thumb is the pump will only pass spherical solids 1/4 the diameter of the suction inlet.
One advantage these pumps have over comparably sized trash models is their low initial cost. There are several reasons for this difference. Lower horsepower engines are utilized that are smaller in size and more fuel efficient. The mechanical seals, since they are not subjected to harsh working conditions, can be made of less costly material. Additionally, the casings are smaller and have fewer machined parts that when combined with the smaller engines make the pumps much lighter in weight.

High Pressure Centrifugal Pumps
High pressure centrifugal pumps are designed for use in applications requireing high discharge pressures and flows. Contractors may use them to wash down equipment on the job site as well as install them on water trailers. Other uses include irrigation and as emergency standby pumps in areas where there is a high risk of fire.

Typically these pumps will discharge around 100 GPM and produce heads in excess of 240 feet. The pump may have a 2 inch suction port and up to three discharge ports of varying size for added versatility. The impellers used on these pumps are a closed design (see figure below) and not open like those used on other types of centrifugal pumps. Similarly the diffuser is more compact than a regular volute in order to generate the high discharge pressures. These pumps by design are not capable of handling any types of solids or even sandy water, Silt, sand or debris would almost immediately clog the pump if allowed to enter into the casing. Additionally, the impeller and diffuser may be made of aluminum rather than weather resistant cast iron since they are not subject to abrasive materials. It is recommended that a mesh net always be placed over the suction strainer if the pump is being used in dirty water.

Trash Centrifugal Pumps
Trash centrifugal pumps get their name from their ability to handle large amounts of debris and are the preferred choice of contractors and the rental industry. The most common sizes are in the 2 to 6 inch range producing flows from 200 to 1,600 GPM and heads up to 150 feet.

The rule of thumb is that a trash pump will generally handle spherical solids up to 1/2 the diameter of the suction inlet. Solids (sticks, stones and debris) flow through without cloggin making themideal for the water conditions typically found on job sites. Trash pumps handle up to 25% suspended solids by volume.

Trash pumps offer another benefit in that they can be quickly and easily disassembled for service or inspection. While standard pumps require special tools that are not always available the inside of a trash pump gousing can usually be accessed with common tools.

Customers occasionally ask why a trash pump costs more than standard centrifugal pumps. One big reason is that higher horsepower engines are neeed for trash pumps. The impeller is typically a cast iron two-vane design (see figure below) and a large volute is required to handle the higher volume of water and debris. The mechanical seal - like the impeller and volute - is selected for its abrasion resistance and more parts are machined for the casing. While there is a higher initial cost it must be noted that is is recovered through the reduced maintenance over the life of an often used pump.

Choosing the correct pump for an application should not be difficult if a few basic preliminary steps are followed.
• Volume and pressure requirements of the system
• Type of material being pumped – oil, fertilizer, insecticides, chemicals, and at what temperature
• How the pump will be driven and at what speed – PTO, engine, electric motor or hydraulic motor
• Check HP requirements of power unit for system pressure and volume

Diaphragm Pumps
A diaphragm pump is a positive displacement which means flow stays constant with speed. Flow is also variable with change of speed. This type of pump is reliable and compact compared to other pumps that have similar flow and pressure ratings. These pumps are excellent for agriculture, industrial, lawn care and nursery requirements because of their adaptability to spraying conditions.
ADVANTAGES
• Wide range of flow and pressure specifications
• Low maintenance and almost wear-free operation
• Self-priming
• Handles wide range of materials that would damage other pumps such as corrosive chemicals, wettable powders and other abrasive solutions.

Roller Pumps
A roller pump is similar to a vane pump except it utilizes multiple rollers in place of sliding vanes. Its unique design adapts to a variety of spraying applications, especially for the lower PTO speed requirements of agricultural spraying systems.
ADVANTAGES
• Low initial and maintenance costs
• Operates efficiently at PTO speeds
• Good priming characteristics
• Compact size in relation to capacity
• Easily mounts

Centrifugal Pumps
Centrifugal pumps are very popular because of their versatility. They provide high capacities and handle abrasive and wettable powders. Centrifugal pumps require higher operating speeds which make them ideal for small engine applications of liquid transfer.
ADVANTAGES
• Handles suspensions well
• High capacity
• Low maintenance
• Low pressure characteristics, pressure only needs to be controlled by by-pass valve
• Some designs can handle solids,

Piston Pumps
A piston pump is a positive displacement pump which means it delivers variable output in proportion to its driven speed. It also develops the higher pressure needed for washing equipment, injecting chemicals, and other agricultural and industrial needs that require long life and dependability.
ADVANTAGES
• Wear resistant
• Positive displacement
• High pressure capability
• Good priming characteristics
• Handles various chemicals, wettable powder suspensions, and other abrasive liquids

Pressure Washer Components

Pump
Creates flow in the system
Nozzle
Sized to the pumps output flow to obtain desired output pressure. Using nozzles, with different orifice sizes, with a fixed flow rate, can change output pressures.
Unloader Valve
Pressure actuated plunger bypasses flow under low pressure to the intake side of pump when the trigger gun is closed. This relives engine load. Opening trigger gun allows unloader to redirect water to the gun.
Pressure Reducing Valve
Lowers inlet water pressure to allow upstream chemical injection to operate.
Pulsation Dampener
Reduces water hammer and smoothes output flow reducing wear on components,
Bypass Hose
Directs water from unloaded to inlet side of pump.
Strainer
Prevents foreign matter from entering system.

Pressure Washer with Downstream Injection

Chemical Injection
Chemical injectors provide a mechanical means of introducing chemical into the water stream. The addition of chemical provides better cleaning results while saving time and water consumption. This chemical can be introduced into the water stream by either upstream (before the pump) or downstream injection.

Methods of Chemical Injection
Upstream

1. Three way selector valve to select between chemical tank and rinse water.
2. Chemical injector on inlet.
3. Pump mounted injector.

Downstream

1. Chemical injector on outlet side of pump.

Operation
Upstream
Upstream chemical injection allows user to inject the chemical at high pressure. Chemical is metered or controlled by a valve mounted at the injector. Operator must return to pressure washer to operator injector.
Downstream
Downstream injection allows operator to control injection at the gun. Chemical is introduced into the water stream at a reduced pressure (normally less that 250 PSI) by increasing nozzle opening size. At reduced pressure, water passes through a venturi drawing chemical with it to the gun. At high pressure water still passes through the venturi but it closes a check valve preventing chemical flow.