The selection and application of PD flow meters in oil-liquid systems is a critical factor in ensuring accurate and reliable flow measurements. PD flow meters offer the professional engineer a wide range of features, making them suitable for a variety of applications. This article will provide an overview of PD flow meters and their key features, as well as advice on how to select and apply them to achieve optimal results.
What is a PD flow meter?
PD flow meters (positive displacement flow meters) are the most accurate and reliable method for measuring the volume of fluid passing through the flow meter. Sophisticated rotating components within a high-precision chamber capture the fluid, and the rotational speed of the rotor is proportional to the flow rate. When the flow of fluid causes rotation, mechanical flow meters rely on this rotation to drive a magnetic coupling or direct gear train connected to a mechanical counter. The volume of this metering space is then determined, and the number of rotations of the rotor can be used to calculate the cumulative volume of fluid passing through the flow meter. Professional engineers rely on PD flow meters to ensure accurate measurements.
Features of PD Flow Meters
Advantages
- High measurement accuracy, unaffected by pipeline conditions;
- Ability to measure high-viscosity liquids;
- Wide range of measurements;
- Direct-reading instrument that requires no external energy to obtain the accumulation and is easy to operate.
Disadvantages
The disadvantages of PD flow meters are complex and can be significant. These includes:
- A complex structure resulting in a large volume; limited types, calibers and working states of the media to be tested;
- Not suitable for use in high and low-temperature environments; most instruments are only suitable for clean single-phase fluids; and
- The possibility of generating noise and vibration.
Types of PD Flow Meters
Positive displacement flow meters, or PD Flow Meters, are a reliable and accurate solution for measuring the volume of a fluid. They are composed of two main elements: the measuring body and the measuring parts. The measuring body consists of a shell and a movable body, such as a rotor in a rotameter, which forms each measuring cavity. The core of the PD flow meter is the movable body, which is the part that moves during the measurement process.
The measuring part is a rotational speed or counting sensor that includes a magnetic material embedded in a pinion extending from one of the screwed elements. This sensor identifies the rotational speed of the screw through the magnetic effect and converts it into a standard pulse signal or current signal. This signal can then be used to directly display the flow on a secondary instrument or be collected and analyzed by a computer.
There are many types of positive displacement flow meters that can be classified according to different principles, typically based on the structure of the measuring element. These include rotor type, such as gear type, screw type, waist wheel type, and egg wheel type flow meters; scraper type; rotary piston type; reciprocating piston type; and diaphragm type.
Of these, rotor type is the most commonly used. As a professional, it is important to be aware of the various types of flow meters available and their capabilities to ensure you are using the right equipment for the job.
Working Principle of PD Flow Meters
The Positive Displacement Flow meter works on a simple principle: Its interior is designed with a space that constitutes a specific volume. The rotor inside the flow meter rotates under the pressure of the fluid that enters through the inflow port. As the rotor rotates, the fluid flows from the inflow port to the discharge port.
The specific volume space that is formed between the rotor and the flow meter housing fills with the rotation of the rotor. This space is then continuously sent to the discharge port. By measuring the number of rotations of the rotor, the volume of the space can be determined, giving an indication of the amount of fluid flowing through.
These principles make the Positive Displacement Flow meter an effective tool for professionals in measuring fluid flow.
Applications of PD Flow Meters
The fixed-displacement flow measurement method for positive displacement flow meters has been around since the 18th century. However, it wasn’t until the 1930s that it entered a stage of widespread commercial application.
Today, PD flow meters have seen tremendous success in industrialized countries, with sales often surpassing 20% in some cases. In my country, it’s estimated that PD flow meters account for around 20% of the market. This is largely due to its accurate metering characteristics, which has enabled it to expand quickly into new sectors such as chemicals, food, and medical, where precision in the measurement of expensive media is essential.
PD flow meters are the go-to solution for professionals looking for a reliable and accurate means of measuring fluid flow.
The measurement of petroleum requires the use of international standards, such as ISO/DIS 2714. Positive displacement flow meters are recognized for their high accuracy and long-term performance retention, making them ideal for measuring the flow of relatively expensive media, including those with high viscosity. As a result, they are commonly used in petroleum, chemical, metallurgical and other industries for measuring and calibrating industrial instruments.
Moreover, positive displacement flow meters are also suitable for measuring low-viscosity liquids and gases, and the installation of a positive displacement flow meter does not require the front and rear straight pipe sections. This makes them a trusted choice for professionals in the petroleum industry.
Conclusion
Positive displacement flow meters are a trusted choice for professionals in the petroleum industry due to their high accuracy, long-term performance retention, and the ability to measure low-viscosity liquids and gases without requiring front and rear straight pipe sections. This makes them ideal for measuring the flow of relatively expensive media, including those with high viscosity, and they are commonly used in petroleum, chemical, metallurgical and other industries for measuring and calibrating industrial instruments.
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