positive displacement flow meter types

Types of Positive Displacement Flowmeters

 

Positive displacement flowmeters, also known as fixed displacement flowmeters, or PD flowmeters for short, are a type of flow meter with higher accuracy. It uses a fixed small volume to measure repeatedly. According to the different measuring elements, positive displacement flowmeters can be divided into many types, mainly including the following:

 

Oval gear flow meter: Its flow part is mainly composed of two mutually meshing elliptical gears and their housings (metering chambers). This flowmeter is suitable for flow measurement of various clean liquids, especially high-viscosity liquids.

 

Scraper flowmeter: The fluid drives the scraper and rotor to rotate, and the scraper extends and retracts radially along a special trajectory. The distance between each two relative scraper end faces is a certain value. When the scraper rotates continuously, a fixed metering chamber is formed between two adjacent scrapers, rotors, the inner cavity of the shell, and the upper and lower cover plates. For each rotation of the rotor, four (or six) metering chamber volumes are discharged, that is, the circulation volume. According to whether the scraper contacts the cavity wall, it can be divided into two types: elastic scrapers and rigid scrapers, which are suitable for measuring liquids of different properties.

 

Double rotor flowmeter: It is the main type of volumetric flowmeter, with various forms and specifications, and can be used to measure various liquid and gas media.

Rotary piston flowmeter: The annular piston is inserted into the shell of a two-layer cylindrical cylinder, forming a form in which the annular piston rotates in the shell with the flow of the liquid. This flowmeter can be used to measure oil products and food.

 

Reciprocating piston flowmeter: The piston reciprocates in the cylinder under the push of the fluid to measure the volume flow. This type of flowmeter is often used in gas stations.

 

Disc flowmeter: Also known as nutating flowmeter, the disc with a central ball rotates and swings up and down in the metering chamber to enter and discharge the liquid. This flowmeter is mostly used as a domestic water meter and an industrial water meter in North America.

 

Liquid-sealed rotary drum flowmeter: Also known as a wet gas meter, it is used to measure the total amount of gas. The flowmeter shell contains about half of the sealing liquid (water or oil), and the rotary drum is half immersed in the sealing liquid, and the gas flows in to make it rotate. This flowmeter has stable performance and is often used as a meter for value transfer or a standard meter.

 

Diaphragm gas meter: This flowmeter is usually used to measure the flow of gas, such as household gas meters.

In addition, there is a lumbar wheel volume flowmeter (also known as a Roots volume flowmeter), whose working principle and working process are basically the same as the oval gear type, but there are no teeth on the lumbar wheel. They do not directly mesh with each other, but are transmitted through a transmission gear set installed outside the housing.

 

These different types of volumetric flowmeters have their own characteristics and applicable scopes. Users can choose according to specific measurement media, flow range, accuracy requirements, and working environment.

 

If you don’t know what kind of flowmeter is suitable for your on-site situation, please consult CIXIFM winny:
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