Can pressure cause a change in the measuring range of a vortex flowmeter?

Pressure changes can cause the measuring range of a vortex flowmeter to change. This is because pressure changes affect the density and flow rate of the fluid, which in turn affects the measurement results of the vortex flowmeter. The following is a detailed analysis:

Effect of pressure on fluid density

Gases:

Gases are compressible fluids whose density increases significantly with increasing pressure. According to the ideal gas equation of state (PV=nRT), the density of a gas is directly proportional to the pressure at a constant temperature.

For example, when pressure increases, the density of the gas increases, resulting in an increase in mass flow rate for the same volume flow rate.

Liquids:

Liquids are usually considered incompressible fluids, but under high pressure conditions, the density of liquids can change slightly. This change has a small effect on the measurement results, but still needs to be considered in high precision measurements.

Effect of pressure on flow rate

Gases:

In pipelines, the flow rate of gases is closely related to pressure. An increase in pressure leads to an increase in the gas flow rate, which affects the measurement results of the vortex flowmeter.

Liquids:

The flow rate of liquids is less affected by pressure, but under high pressure conditions, the flow rate of liquids can also change slightly.

The effect of pressure on the measuring range of vortex flowmeters

Definition of measurement range:

The measuring range of a vortex flowmeter usually refers to the minimum flow rate (lower limit) and the maximum flow rate (upper limit) that it can accurately measure.

The measuring range is affected by the density and flow rate of the fluid, which are closely related to the pressure.

Effect of pressure variations:

Gas Measurement:

When pressure increases, the density of the gas increases and the mass flow rate at the same volume flow rate increases, which may cause the meter to exceed its rated measurement range.

When the pressure decreases, the density of the gas decreases and the mass flow rate decreases for the same volume flow rate, which may result in the flowmeter being unable to accurately measure low flow rates.

Liquid Measurement:

Pressure changes have a small effect on the density and flow rate of liquids, but their effect on the measuring range still needs to be considered under high pressure conditions.

The role of temperature and pressure compensation

In order to eliminate the effect of pressure changes on the measurement results, vortex flowmeters usually need to be equipped with temperature and pressure compensation:

Pressure compensation:

By measuring the pressure of the fluid, combined with the pressure-density relationship of the fluid, the fluid density under the current pressure is calculated.

Comprehensive Compensation:

According to the real-time data of pressure and temperature, combined with the fluid’s equation of state, calculate the exact fluid density, so as to convert the volume flow rate to mass flow rate.

Considerations for practical application

Selection of a suitable flowmeter:

Select a suitable vortex flowmeter according to the pressure range of the actual working conditions, and ensure that its measuring range can cover the expected pressure variations.

Install pressure sensor:

If the vortex flowmeter itself does not come with a pressure compensation function, it can be compensated and calculated by an external pressure sensor and inputting the signal into the flow totaliser or control system.

Periodic calibration:

In occasions with large pressure variations, the vortex flowmeter needs to be calibrated periodically to ensure measurement accuracy.

Pressure variations can lead to changes in the measuring range of vortex flowmeters, especially in gas measurements, where the effect of pressure variations on density and flow rate is more significant. In order to eliminate the influence of pressure change on the measurement result, vortex flowmeter usually needs to be equipped with temperature and pressure compensation function. In practical application, the appropriate flowmeter should be selected according to the pressure range of the working condition and necessary compensation measures should be taken to ensure the measurement accuracy and reliability.