# Bidirectional Flow Measurement

## What is bidirectional flow?

Bidirectional flow refers to forward and directional flow. Bi-directional flow lines are not common in most process plants. The measurement of unidirectional flow is easy to understand and is applicable to all types of flow technologies. However, most flow technologies cannot accurately measure two-way flow.
They always cause difficulties for process and instrument designers. For two-way flow, the pipeline scheme uses the same pipeline to achieve the transport and/or control function of the opposite flow (forward or reverse flow) according to the process conditions and goals.

## Can the flow meter perform bidirectional measurement?

If the flow direction of the medium in the pipeline is reversed. Does the flow meter need to be installed with a flow meter for forwarding use and a flow meter for reverse use accordingly? Is there a flow meter for normal measurement that does not consider the flow direction?

1. If you just look at the flow rate, you can. For example, an electromagnetic flowmeter. It doesn’t matter if you measure in the whole direction or in the reverse direction. Change the reverse measurement to allow in the prerequisite electromagnetic flowmeter settings.
2. It’s hard to say if you still need a cumulative amount. How do you convert the cumulative amount you measured forward and the cumulative amount you measured backward? Whether to subtract or add depends on your actual situation.

## How does the ultrasonic flowmeter realize bidirectional flow measurement?

The principle of the ultrasonic flowmeter is to calculate the fluid flow rate using the difference in sound velocity. And multiply the fluid velocity by the area to calculate the volume flow.

Usually, there is an incident angle between the probe of the ultrasonic flowmeter, that is, the transducer and the meter body. From 60 degrees to 45 degrees. Ultrasonic waves propagate between a pair of probes if there is no fluid, that is, at zero flow. The travel time back and forth is the same. It is equivalent to a zero flow rate.

Extended reading: Ultrasonic Flow Meters Types & Technical Guide

Once there is fluid, the speed of the ultrasonic flowmeter back and forth between a pair of probes is different. Regardless of the direction of fluid flow, there will be a difference in sound velocity. If one direction is set as the normal flow direction, then the normal sound velocity should be a positive number. If the sound velocity difference is negative, the flow is in the opposite direction. That is reverse measurement. The measurement accuracy of the two directions is the same.

Extended Reading: Inline Ultrasonic Flow Meter

## Can a vortex flowmeter measure bidirectional flow?

You cannot measure bidirectional flow with just one vortex flowmeter. But in some applications, you can use two for this.

The vortex flowmeter has a bluff body in front of the sensor, which is used to generate the vortex in the flow. As far as I know, no flowmeter has two bluff bodies to measure bidirectional flow.

If you have a two-way steam application. Then you can install two vortex flowmeters in the same line, as long as you respect the inlet and outlet operation of both. However, depending on the size of the line, this setting may become expensive.

## Bidirectional orifice flowmeter

The bidirectional orifice flowmeter is a differential pressure flowmeter. Mainly used for flow measurement of liquid and gas. According to the characteristics of the orifice flowmeter, it has the advantage of high temperature and high pressure. Therefore, the orifice flowmeter is widely used in the field of high temperature and high-pressure measurement. The orifice flowmeter has high accuracy and good stability and is unanimously recognized by users.

What kind of measurement conditions will use an orifice flowmeter to measure? It can be used according to the requirements of the site, such as typical boiler steam, the general temperature can be close to about 500 degrees, and general flow meters cannot be used. However, the orifice flowmeter can effectively solve this high-temperature working condition, and the only disadvantage is its high cost of use.

Extended reading: 2 inch Water Flow Meter

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Extended reading: Integral DP Flow Meter|Gas, liquid, steam|Compact structure

Sino-Inst offers over 50 flow meters for flow measurement. About 50% of these are differential pressure flow meters, 40% are the liquid flow sensor, and 20% are Ultrasonic Level Transmitter and mass flow meters.

A wide variety of flow meters options are available to you, such as free samples, paid samples.

Sino-Instrument is a globally recognized supplier and manufacturer of flow measurement instrumentation, located in China.

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