Positive Displacement Flow Meter – Vetrix MT Series

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MT series meter is a positive displacement meter for liquids. They are designed for liquid metering both in transfer and process control applications. Thanks to their design they are easy to keep and can suit a wide range of applications.

What is Positive Displacement Flowmeters Work

A positive displacement meter is a type of flow meter that requires fluid to mechanically displace components in the meter in order for flow measurement. Positive displacement (PD) flow meters measure the volumetric flow rate of a moving fluid or gas by dividing the media into fixed, metered volumes (finite increments or volumes of the fluid). A basic analogy would be holding a bucket below a tap, filling it to a set level, then quickly replacing it with another bucket and timing the rate at which the buckets are filled (or the total number of buckets for the “totalized” flow). With appropriate pressure and temperature compensation, the mass flow rate can be accurately determined.

Principle Of Positive Displacement Flowmeters

PD Meters (Positive displacement meter) work on the principle similar to the concept of repeatedly filling a beaker with any fluid and then pouring it downstream while keeping a count of the number of the times the beaker is filled so as to determine its volume. It is capable of measuring a very low flow of fluids because its internal components are mass balanced but are not balanced hydraulically. This is the only device that measures the volume of the liquid passing through it directly without using any external power. In order to determine volume, small pockets of the fluid are trapped within a high precision chamber between the rotating components. The rotational velocity of the rotor is directly proportional to the fluid flow rate because it is the flow of fluid which is causing the rotation in the flow meter.

How Positive Displacement Flowmeters Work

Positive displacement flowmeter technology is the only flow measurement technology that directly measures the volume of the fluid passing through the flowmeter. Positive displacement flowmeters achieve this by repeatedly entrapping fluid in order to measure its flow. This process can be thought of as repeatedly filling a bucket with fluid before dumping the contents downstream. The number of times that the bucket is filled and emptied is indicative of the flow through the flowmeter. Many positive displacement flowmeter geometries are available.

Entrapment is usually accomplished using rotating parts that form moving seals between each other and/or the flowmeter body. In most designs, the rotating parts have tight tolerances so these seals can prevent fluid from going through the flowmeter without being measured (slippage). In some positive displacement flowmeter designs, bearings are used to support the rotating parts. Rotation can be sensed mechanically or by detecting the movement of a rotating part. When more fluid is flowing, the rotating parts turn proportionally faster. The transmitter processes the signal generated by the rotation to determine the flow of the fluid. Some positive displacement flowmeters have mechanical registers that show the total flow on a local display. Other positive displacement flowmeters output pulses that can be used by a secondary electronic device to determine the flow rate.

Positive displacement flowmeters can be applied to clean, sanitary, and corrosive liquids, such as water and foods, and some gases. Usually best applied when high accuracy is required at a reasonable price.

Applications

• Check of loading/unloading operations of fuel and petrochemical products in fuel bulk plants and/or refineries
• Wine manufacturer
• Oil and gas plant

Dimension

Model Description