Frequently Asked Questions

A metering pump is a device that is used to add small, precise amounts of liquid to other fluid streams or vessels. Dosing and proportioning pumps are different names for metering pumps. Across a wide variety of discharge pressures, a metering pump must deliver liquid with an accuracy of higher than 3%.

Below are three of the most common metering applications:

  • Regardless of differential pressure or fluid viscosity, a consistent flow rate is maintained.
  • Maintaining a system parameter by delivering a varied flow (for example, pH).
  • Using a discrete dosage injection (typically required in batch processing).


Pharmaceuticals, water and sewage treatment, food and beverage production, electricity generation, chemical processing, petrochemicals, and oil and gas extraction require metering. Liquids can range from scents and pigments used in the cosmetics and food industries to acids and alkaline solutions used in chemical operations and water treatment.

It is possible to create a regulated flow using a centrifugal pump when delivering low viscosity liquids at high flow rates (>1 m3/h) and low delivery pressures. This may be the most economical option.

In some cases, however, precise metering involves the use of a positive displacement pump. This type of pump moves a fluid by confining it in a set volume and moving it mechanically through the system using seals or valves.

The pumping motion is cyclic, and a specified delivery rate or precise single dose can be achieved by regulating the motor’s speed or stroke length.

For metering and dosing, reciprocating pumps with plungers, pistons, or diaphragms have traditionally been employed. These pumps can maintain a constant flow rate across a wide range of pressures. Other types, such as peristaltic pumps or gear pumps, can now be used thanks to recent electronics and control technology improvements.

On the suction stroke of a piston pump, a defined volume of liquid is pulled into the pump and delivered on the compression stroke   .The plunger size determinesTheimportancee of fluid moved by a plunger pump. The volume of liquid given is known accurately in both circumstances. However, because of the reciprocating action, no fluid is delivered during the pumping cycle’s suction stroke. This causes pulses in the discharge, with the fluid speeding up during supply and slowing down during suction. Because pulsation can generate detrimental vibrations in the discharge system, damping or smoothing is frequently used. Using additional, out-of-phase pistons or plungers can also help to reduce pulsing.

A flexible membrane, rather than a piston or plunger, is used to move fluid in a diaphragm pump. The capacity of the pumping chamber is expanded by expanding the diaphragm, and fluid is sucked into the pump. The volume of the diaphragm is reduced when it is compressed, and some fluid is expended. Diaphragm pumps are useful for pumping hazardous substances since they are hermetically enclosed. The precision of delivery, on the other hand, is determined by the performance of the discharge and suction side valves, as well as the amount of backflow.

Pulsation in the discharge is also a problem with diaphragm pumps, although it can be reduced by using two (or more) diaphragms, one in compression and the other in suction. The air-operated double diaphragm pump is an example of this type of design (AODD). AODDs are a reasonably low-cost and dependable metering technology capable of functioning at up to 10 bar for flows below 10 m3/hr and when a 3 percent accuracy is acceptable. They can be used dry and can handle soiled or polluted liquids.

API 675 is a petroleum, petrochemical, and gas industry standard that specifies the minimum specifications for reciprocating, metering pumps. It applies circularly to both hydraulic diaphragm and packed plunger pumps. Direct mechanically actuated rotary pumps and diaphragm pumps are not included.

Traditionally, the motor stroke length of reciprocating metering pumps has been varied to ensure that the pump delivers the required flow rate. This method allows the drive motor to operate at its maximum efficiency. Motor speed can now be precisely adjusted thanks to advancements in drive and control technologies, allowing pumps to run more effectively. Pumps utilizing VSD technology may be more expensive than fixed-speed alternatives, but the extra cost will be quickly offset by the long-term energy savings.

A positive displacement pump called a dosing pump is used to inject a chemical or another substance into a flow of water, gas, or steam. Dosing pumps are normally modest, but they provide a very accurate flow rate for optimal control. They are the heart of an integrated dosing system meant to disperse chemicals automatically.

Dosing Pumps are a form of Positive Displacement Pump that provides low flow rates, excellent accuracy, and control for consistent product dosing. They’re also known as measuring pumps, and they’re commonly employed in the chemical and pharmaceutical industries, but their adaptability allows them to be employed in practically any business.

A tank-and-field septic system breaks down residential sewage and disperses it into the soil; a dosing system includes a pumping station to prevent floods or compensate for a location where gravity will not disperse the wastewater.

Non-positive displacement pumps, such as centrifugal pumps, are classified as such. Traps a particular volume of liquid and forces it through the discharge port from the suction. As pressure changes, the flow rate remains constant. Internal clearances enable the handling of higher viscosities.

A reciprocating pump is more efficient than a centrifugal pump in general. Reciprocating machines are commonly used in low-flow/high-head applications. On low-flow/high-head operations, centrifugal pumps can have efficiency as low as 40%.

Pump efficiency is defined as the ratio of the pump’s water horsepower output to the shaft horsepower input. The flow rate and pressure delivered by the pump define the water horsepower.

Rotary pumps rotate in a circular manner, dispensing a fixed amount of liquid with each revolution of the pump shaft. Centrifugal pumps differ from rotary pumps in that they use kinetic energy to transfer liquid rather than mechanical means.

The basic difference between a centrifugal and a reciprocating pump is that a centrifugal pump uses the impeller’s kinetic energy to continually supply fluid, whereas a reciprocating pump’s piston suctions the fluid and then pushes it out, which does not provide continuous supply.

For metering and dosing, plunger or piston pumps, diaphragm pumps, or peristaltic pumps have traditionally been utilized.

Compressed air is used to alternately drive a double diaphragm (two diaphragms) in air-operated diaphragm metering pumps. The airflow between the two diaphragms is alternated by a shuttle valve. The amount of air pressure provided to the pump controls the flow of the media being pumped.

A chemical metering pump transports a specific volume of liquid over a certain length of time to produce a very accurate flow rate, and the pumps offered by SR Metering are among the best on the market – and will undoubtedly give you a cost-effective solution.

Diaphragm-type dosing pumps are well-built dosing pumps that are widely employed in a variety of industries. In the event of a crack, the technically advanced range of these pumps comes standard with a separation chamber, which protects the medium from flooding the system components or the pump itself.

Pumping from reservoirs, lakes, streams, and shallow wells are done with centrifugal pumps. They’re also employed in irrigation pipelines as booster pumps. Before they can work, centrifugal pumps must be entirely filled with water, or “primed.”

You must know four things before you can choose a pump that will meet your needs: 1) the total head or pressure it must operate against 2) the desired flow rate, 3) the suction lift, and 4) the fluid properties.

Regardless of pressure fluctuations, a positive displacement pump maintains a steady flow at a fixed speed. … peristaltic hose pumps. The pump moves the fluid by trapping a specific amount and forcing the volume into the output pipe. Pumps with pistons.

A plunger pump is a positive displacement pump with a stationary high-pressure seal and a smooth cylindrical plunger that moves through it. This distinguishes them from piston pumps and enables them to operate at higher pressures.

A positive displacement pump transfers fluid by confining a defined volume with seals or valves and mechanically pushing it through the system. Pistons, screws, gears, lobes, diaphragms, and vanes can all be used to drive the pumping action. Reciprocal and rotary are the two primary forms.

Reciprocal pumps are now used to pump very viscous fluids such as concrete and heavy oils, as well as in applications requiring low flow rates against considerable resistance. Pumping water from wells was done with reciprocating hand pumps.

Positive displacement devices, such as reciprocating pumps, are often employed for low-flow, high-pressure applications. Pumping action is provided by pistons and diaphragms, with valves regulating flow into and out of the pump body. Large-scale power pumps to smaller pressure-washer devices are available.


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