Positive Displacement Flow Meter Comprehensive Guide

29 Jul.,2024

 

Positive Displacement Flow Meter Comprehensive Guide

Accurate liquid flow measurement is crucial for various industries, enabling precise control of processes, efficient resource allocation, and reliable operation. A positive displacement flow meter, or pd meter, is vital in achieving this accuracy by providing highly precise and repeatable measurements. These meters are designed to accurately measure the volume of fluid flowing through a system, making them suitable for a wide range of applications, from low flows to high viscosities.

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Positive displacement flowmeters are a type of flow meter that operates by trapping and measuring discrete volumes of fluid. They offer exceptional accuracy, even in challenging flow conditions, and are known for their reliability and versatility. Positive displacement flow meters are available in various designs, such as gear meters, oval gear flow meters, nutating disk meters, and piston meters, each with unique working principles and advantages.

Positive displacement flowmeters have significant importance across multiple industries. Oil and gas are used for precise custody transfer, well production measurement, and process monitoring. In chemical processing, positive displacement flow meters ensure accurate dosing and blending of chemicals. Food and beverage industries rely on these meters for precise filling, batching, and dispensing. Pharmaceutical and biotechnology sectors use positive displacement flow meters for accurate dosage and process control. The versatility and reliability of positive displacement flow meters make them valuable for ensuring accurate flow measurement across a wide range of fluid types and applications in different industries.

How Positive Displacement Flow Meters Work

Positive Displacement Flowmeter Technology

A positive displacement flow meter (PD meter) is an instrument used to measure the flow rate of fluids by trapping and measuring discrete volumes of fluid as it passes through the meter. The meter&#;s internal components, such as gears, helical rotors, nutating disks, or pistons, create a chamber that fills and empties each fluid volume, providing accurate and reliable flow readings. As the fluid flows through the chamber, the internal components rotate or move, measuring the volume of fluid displaced. This rotation or movement is directly proportional to the flow rate, allowing the flow meter to calculate and accurately measure the fluid flow rate by counting and averaging the rotations or movements over time.

Positive Displacement Meter Types

  1. Oval Gear Positive Displacement Meters: These meters utilize two interlocking oval gears to measure liquid flow. The fluid enters the chamber between the gears, causing them to rotate and displacing a fixed fluid volume with each revolution.
  2. Helical Gear Flow Meters: HelixGear meters employ helical rotors with a unique twisted shape. As the fluid passes through the rotor chambers, it causes the rotors to rotate, measuring the flow based on the volume of fluid displaced.
  3. Nutating Disk Positive Displacement Flow Meters: Nutating disk meters feature a disk that wobbles or nutates within a spherical chamber. The disk nutates as the liquid flows into the chamber, creating a measuring action that quantifies the volume of fluid passing through.
  4. Piston Flow Meters: Piston meters consist of a cylindrical chamber with a piston that moves back and forth as fluid enters. The piston&#;s movement displaces a fixed fluid volume with each stroke, allowing for accurate flow measurement.
Photo Courtesy of Omega Engineering

Advantages and Applications of Positive Displacement Flow Meters

High Accuracy and Precision for Reliable Flow Measurement

The positive displacement flowmeter offers exceptional accuracy and precision in flow measurement. Their displacement-based measurement mechanism ensures reliable and repeatable readings, making them ideal for applications that require precise flow control and accurate volume measurement. Some offer incredible linearity of ±0.075% and repeatability of 0.02%.

Suitable for a Wide Range of Fluids and Viscosities

Positive displacement flowmeters are highly versatile and can handle various fluids, including viscous liquids. Whether measuring low flow rates or high-viscosity fluids, positive displacement meters can provide accurate and reliable readings, making them suitable for various industries and applications.

Various Applications

Positive displacement flowmeters play a critical role in the oil and gas industry, providing accurate measurement for marketing terminals, refined product pipelines, crude oil transfer, feedstock import measurement, renewable fuels blending, aviation refueling, bunkering, and offloading.


The Best PD Meter In The Industry &#; Brodie International&#;s BiRotor Plus Meter

The Brodie BiRotor Plus Meter stands out as the best positive displacement (pd) meter on the market. Its advanced design and superior performance set a new standard for accuracy, reliability, and versatility. The BiRotor Plus Meter incorporates cutting-edge technology and engineering innovations, ensuring precise flow measurement even in challenging conditions. Its double-case design combines rugged durability, improved accuracy, and reliable pulse output. The meter&#;s helical rotors eliminate the possibility of buildup, offering low maintenance requirements and extended service life. With a wide range of available sizes and pressure ratings, the BiRotor Plus Meter caters to diverse industry needs. It is the go-to choice for optimizing flow measurement in petroleum, industrial, and other relevant sectors.

Key Considerations for Positive Displacement Flow Meters

Fluid Viscosity and Temperature Range on Meter Selection

When selecting a pd flow meter, it is crucial to consider the viscosity and temperature range of the fluid being measured. Different flow meters are designed to handle specific viscosities and temperature ranges effectively. Understanding the fluid&#;s characteristics ensures the appropriate meter is selected to maintain accurate flow measurement.

Pressure Drop and Compatibility with System Requirements

Positive displacement flow meters can introduce a pressure drop in the system due to their design. Considering the pressure drop and ensuring compatibility with the system requirements is essential. Proper sizing and selection of the meter help minimize pressure drop while maintaining accurate flow measurement.

Maintenance and Calibration: Ensuring Optimal Performance

Regular maintenance and calibration are vital for the optimal performance of pd flowmeters. Following manufacturer guidelines for maintenance, such as cleaning and inspecting the meter to prevent clogging or damage. Additionally, periodic calibration ensures accurate measurement and reliable performance over time.

Factors Affecting Meter Accuracy and Longevity

Several factors can affect the accuracy and longevity of a positive displacement flowmeter. Understanding these factors allows for better management of the meter&#;s performance. Factors such as fluid composition, particulate matter, and system conditions can impact meter accuracy and longevity. Proper filtration, cleaning, and monitoring can help mitigate these factors and ensure the continued accuracy and longevity of the flowmeter.

Comparison with Other Flow Measurement Technologies

Positive Displacement Flow Meters vs. Turbine Flow Meters

Positive displacement and turbine flow meters are commonly used for flow measurement but differ in operating principles. Pd meters measure liquids flow by trapping and measuring discrete volumes, while turbine flow meters use a rotor with blades or vanes that rotate in response to fluid flow.

Positive Displacement Flow Meters vs. Magnetic Flow Meters

Positive displacement and magnetic flow meters are two distinct technologies employed for flow measurement. Positive displacement flow meters measure flow by displacing fluid tp calculate volumetric flow rate, whereas magnetic flow meters utilize electromagnetic principles to measure the velocity of conductive fluids. Magnetic flow meters are suitable for larger pipe sizes and can handle various liquids. In contrast, positive displacement flow meters accurately measure low to moderate flow rates and suit various fluid viscosities.

Positive Displacement Flow Meters vs. Coriolis Flow Meters

Positive displacement and Coriolis flow meters are highly accurate flow measurement technologies. Pd meters measure fluid flow by trapping and measuring volumetric flow, while Coriolis flow meters detect the deflection of liquids as it flows through vibrating tubes. Coriolis flow meters are known for their exceptional accuracy and suitability for various fluids. In contrast, the positive displacement flow meter offers advantages in lower pressure drop, suitability for viscous fluids, and the ability to handle a broader range of flow rates.

Maintenance and Troubleshooting Tips for Positive Displacement Flow Meters

Regular Inspection and Cleaning Procedures

Positive displacement flow meters require regular inspection and cleaning to maintain optimal performance. This includes checking for debris or buildup that may affect the meter&#;s accuracy or obstruct its moving parts. Following manufacturer guidelines, users should implement routine cleaning procedures. Regular inspection helps identify potential issues early on, ensuring the meter delivers accurate flow measurements.

Ensuring Proper Calibration and Accuracy

Calibration is crucial to maintaining accurate flow measurements with a positive displacement flowmeter. Regular calibration checks help verify the meter&#;s accuracy and make any necessary adjustments. Users should follow recommended calibration intervals and procedures outlined by the manufacturer. Users can maintain reliable and precise flow measurements over time by ensuring proper calibration.

Conclusion

In conclusion, pd flow meters are highly accurate and versatile instruments crucial in achieving precise and reliable flow measurements. Their unique working principles and design variations, such as gear meters, oval gear flow meters, nutating disk meters, and piston meters, offer exceptional accuracy and repeatability across various industries. These meters are suitable for measuring a wide range of fluids, including viscous liquids, and can handle different flow rates effectively. Proper consideration of fluid viscosity, temperature range, pressure drop, and regular maintenance is essential for optimizing their performance. With their ability to deliver precise and reliable measurements, positive displacement flow meters are invaluable in achieving efficient and optimized processes in industries such as oil and gas, chemical processing, and more.

Are you interested in learning more about Cherokee Measurement & Control&#;s exceptional PD flow meter offerings? Take the next step towards optimizing your flow measurement processes. Contact us today!

Flow Meter Types & Their Functions

Welcome to the Blue-White guide to flow meters and their functions. Flow meters are devices used to measure the flow of fluids, such as fuel, water, and other liquids. They are essential for many industries and applications, including industrial process control, medical diagnostics, and energy management. This guide will provide an overview of the different types of flow meters available from Blue-White and information on how to use and maintain them properly.

Flow Meter

A flow meter is a device used to measure the flow rate or quantity of a gas or liquid moving through a pipe. Flow meters measure the volumetric or mass flow rate of a liquid or gas. They are used to measure how much of a substance passes through a pipe over a period of time. Flow meters can measure flow in many applications, including water, oil, fuel, air, and steam.

They have applications in many industries, including water treatment, heating and air conditioning, industrial manufacturing, process control, and waste management.

For Starters, What is Flow?

Flow is a term used to describe the movement of materials or energy from one place to another in a continuous and organized manner. This can refer to the flow of fluids such as water, gas, and oil. Flow is an important concept in engineering and manufacturing in understanding how systems and processes work.

In this case, we will refer to flow as it applies to fluids in pipes. And in this application, flow is typically divided into two types: Open channel flow and closed conduit flow.

Open Channel Flow

Open channels are streams with an exposed surface and unrestricted access to the atmosphere. For example, canals and pipelines that are not completely full, such as drains and sewers.

In open channel flow, gravity is responsible for the motion of the liquid. The water level will gradually decrease down the stream as the flow progresses.

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Closed Conduit Flow

Closed conduit flow is the flow of a liquid or gas through a pipe, channel, or another closed vessel. Closed conduit flow typically occurs at a constant velocity and depends on factors such as the pressure difference between the ends of the conduit and its length.

F-420 Acrylic Flow Meter

Water supply and district heating pipes are common places to observe closed conduit flow. Even drinking straws are a simple but efficient example of this. The flow rate here is largely determined by the pressure difference between the two ends, the distance between them, and the area of the conduit. Additionally, the hydraulics of the pipeline &#; such as its shape, roughness, and bends &#; also have an impact. All these factors come together to create the rate of flow.

Ranges of Flow Pressure

Flow pressure measures how much force is needed to move a liquid or gas through a system. It is measured in pounds per square inch (PSI) or kilopascals (KPa). The flow pressure range can vary greatly depending on the type of system, the size of the pipes, and the type of liquid or gas being pumped. For example, a residential water system typically operates at a much lower flow pressure than an industrial system. Flow pressure can also be increased or decreased by changing the size of the pipes, the number of fittings, and the type of pump.

Ranges of Temperature

Any flow will also have a temperature, with the typical range in most industries where they are used being from -40°F to +400°F (-40°C to +204°C). And to measure this, flow meters are designed to measure the flow rate in fluids with a wide range of viscosities, temperatures, and pressures. Flow meters can also detect changes in flow rates and can be used to detect leaks or other irregularities in the system.

Another term is thermal flow measurement, which reads how much heat is transferred while a gas passes a surface. The two main measurements taken with regard to temperature are simple readings via a temperature sensor and a heated flow sensor that measures the heat transfer from the flow of any given material inside the system.

F-460 Polysulfone Flow Meter

What Does a Flow Meter Do?

As mentioned above, a flow meter is an instrument used to measure the flow rate of liquid or gas. It measures the flow rate by detecting and monitoring changes in pressure, level, or another variable caused by fluid passage through pipes.

Types of Flow Meters and Their Functions

Flow meters measure fluids, but fluids can be any liquid, viscous, or gas known to us. Hence, a wide range of flow meters is available on the market. All of these types vary in function and application.

Differential Pressure Flow Meters

Differential pressure flow meters employ the Bernoulli Equation, which states that a fluid&#;s pressure decreases while its speed increases. These types of flow meters report the difference between the two measurements. The first measurement causes a shift in kinetic energy when the air is forced through a hole in the flow meter, which is then measured by the second element.

The sub-types of differential pressure flow meters are rotameters / variable area flow meters, orifice plates, venturi flow meters, and pitot tube flow meters. These meters measure the pressure difference between two points, allowing for a precise calculation of the fluid flow rate.

Rotameters / Variable Area

A variable area flow meter is a differential pressure flow meter. Variable area flow meters are simple, versatile, and cost-effective devices that operate at a relatively constant pressure drop and measure liquids, gases, and steam flow. The variable area flow meter is popular for industrial and commercial flow indication because it has a linear scale, a relatively long measurement range, and a low-pressure drop &#; plus, they are simple to install and maintain.

Orifice Flow Meter

The orifice plate flow meter is a differential pressure flow meter used in clean liquid, gas, and stream mass flow measurements. It is available for a wide range of pipe sizes and allows for measuring fluid flows in larger pipes (over 6&#; in diameter).

Venturi Flow Meter

Venturi flow meters allow the fluid to flow through a constricted section of pipe called a throat, where a pressure difference is created. The liquid speeds up and creates a pressure differential as it passes through, which is then used to calculate the volumetric flow rate of the fluid. Venturi meters are often used in applications requiring high precision levels with large volumes of liquid at low-pressure drops. They&#;re also suitable for liquids with a high solids content. Additionally, they are relatively easy to install because they have no moving parts. They can be fitted via flanged, welded, or threaded-end fittings, making them a popular choice for many applications.

Pitot Tube Flow Meter

Pitot tube flow meters are a common and cost-effective tool for measuring fluid flow rate in a pipe or duct. The pitot tube is inserted into the pipe to measure the difference in pressure between the upstream and downstream of the flowing fluid.

The installation process for a pitot tube is relatively straightforward, as it typically involves drilling a hole into a pipe and inserting the pitot tube into the fluid path with its impact port facing directly into the fluid flow.

Pitot tube flow meters remain attractive for many applications due to their low cost and easy installation process. They&#;re frequently used in HVAC and commercial aquatics systems, for example. Moreover, they offer minimal pressure drop, meaning they do not significantly impede the flow rate of the fluid.

F-300 Pitot Tube Acrylic Flow Meter

Positive Displacement Flow Meter

A Positive Displacement Flow Meter is a device that measures the flow rate of a fluid by measuring the amount of fluid that is displaced by a series of chambers or rotors. This type of flow meter is highly accurate, durable, and efficient and is commonly used in industries such as oil and gas, food and beverage, and chemical processing.

PD or Positive Displacement flowmeters utilize a rotating mechanism within a precision-engineered chamber to capture fluid pockets, like filling a beaker with liquid and pouring it down an aisle, counting each fill.

  • Reciprocating Piston Meter:

A reciprocating piston meter is a positive displacement flow meter that measures the volumetric flow rate of liquids and gases. It consists of a chamber with a piston, an inlet and an outlet valve, and a pressure transducer. The piston is driven by an external power source, such as an electric motor, magnetic field, or pneumatic cylinder, and moves back and forth in the chamber. As the piston moves, it displaces a fixed volume of liquid or gas, and the flow rate is calculated based on the speed of the piston and the volume displaced. The inlet and outlet valves open and close to control the flow rate, and the pressure transducer measures the pressure inside the chamber.

  • Oval-Gear Meter:

An oval-gear meter is a positive displacement flow meter that measures fluid or gas flow through two oval-shaped gears with close-fitting teeth. The gears are connected to each other and are placed in a chamber that has a known volume. As the fluid or gas passes through the chamber, the gears rotate, and the volume of the chamber is displaced. The displacement of the volume is measured, and the flow rate of the fluid or gas is calculated.

  • Nutating-Disk Meter:

A nutating-disk flow meter works by passing fluid through a disk that is mounted on a shaft, which is connected to a motor. The disk is free to rotate around the shaft as the fluid passes through, causing the disk to rotate, or nutate, at a rate proportional to the flow rate. The rate of rotation and nutation is then measured and converted into a flow rate.

  • Rotary-Vane Meter:

A rotary-vane flow meter uses a rotary vane, a type of impeller, to create a pressure differential across the meter, which is then used to calculate the flow rate. The inner part of the rotary vane meter consists of several vanes, each connected to a central shaft. As the fluid passes through the meter, the vanes rotate, causing a series of gears to turn. The gears are connected to a mechanical counter that records the total flow rate. The rotary vane meter is highly accurate and reliable, often used in the automotive industry to measure fuel and oil flow rates. The rotary vane meter is also used in medical applications, such as anesthetic delivery systems. The design of the rotary vane meter allows it to be used in a wide range of temperatures and pressure ranges.

SONIC-PRO® S6A Digital Ultrasonic Flow Meter

Volumetric Flow Meter

Volumetric flow meters measure the speed of the flow rather than the actual volumetric rate directly. The volumetric flow rate is calculated by multiplying the measured velocity by the cross-sectional area at which it&#;s installed, accurately representing how much material passes through in a given time period. Flow meter technology has become more advanced, with digital displays becoming more commonplace with improved accuracy due to better calibration technology and new sensing methods.

Ultrasonic Flow Meter

Ultrasonic flow meters measure flow rate by detecting fluctuations in ultrasonic oscillations. They come in two varieties: time difference and Doppler. Time difference type meters, also called time-of-travel meters or transit meters, measure the time taken for ultrasonic waves to travel from one point to another, while Doppler-type meters measure the frequency shift of soundwaves reflected from the moving particles in the medium. Both are used for accurate flow rate measurement.

Mass Flow Meter

Mass flow meters measure the mass of a material that passes through the system in a given period of time. They measure the mass per unit of time, typically expressed in kilograms per second (kg/s). Mass flow meters measure the speed and density of the material as it passes through the device. This data is then used to calculate the mass flow rate. Mass flow meters are typically used to measure the flow of liquids, gases, and solids in industrial processes, such as the chemical, food, and pharmaceutical industries. Coriolis flow meters are the most popular mass flow meters used in industries today.

Blue-White Flow Meters For Any System

Flow meters are an incredibly important and versatile tool for measuring the flow of liquids, gases, and solids in a variety of industries. There is an ideal meter for any application, from ultrasonic flow meters to variable area flow meters.

Blue-White has you covered when it comes to fluid control processes. We manufacture industrial-grade flow meters that are accurate and robust, so you can depend on them to keep your processes running smoothly, safely, and cost-effectively. From rotameters / variable area flow meters to paddlewheel flow meters to ultrasonic flow meters, all our products are Made in the USA and ready to ship! Get peace of mind by knowing your flow meters are reliable and of the highest quality. Trust Blue-White for all your flow meter needs.

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