Features of Liquid Flow Meters
As the name suggests, liquid flow meters are used for measuring the flow rate of liquids. They are an essential device for numerous industries: from oil and gas plants to chemical and pharmaceutical factories, they are used to measure gas, liquid, or both. Extremely durable, reliable, accurate, and cost-effective meters are now possible due to innovations by companies like Proteus Industries Inc. In response to increased industrial demand and technological progress, more computer-interfaced flow meters are being produced, enabling instantaneous and remote flow measurement monitoring.
Though there are various flow meters integrated with new and advanced features, some are essential. The most basic of these are accuracy in measurements, flow velocity range, installation method, and maintenance requirements, some of which are explained in depth below. Output connectivity options and mechanical restrictions should also be considered.
These fluid characters can significantly influence the performance of flow meters, and therefore should be taken into account to ensure the correct application of the device:
- Phase (Single/Double)
- Flow Profile (ex: Transitional, Turbulent, Laminar
Below are key, variable features of flow meters important to their application.
Minimum and maximum volumetric or mass flows to determine the flow velocity range of the flow meter. This ability is calculated using the ratio of maximum to minimum flow rates and a Reynolds Number. The ability of the flow meter is commonly denoted as a turndown ratio: using the meter outside this range can negatively affect its performance
The repeatability of the flow meter is based on two techniques.
Metering: The repeatability of a particular flow meter, through metering, is tested when the results of the successive measurements, using that particular meter are approximate, in conditions where the same quantity was measured by the same procedure, by the same person at the same location over a short duration. More precisely, it is the feature of the meter to give approximately close values under certain and constant conditions.
Laboratory Technique: In laboratory test technique, the repeatability of the meter is checked through comparing the difference obtained in successive measurements under some definite conditions, by the same operative using the same device plus same material and test technique.
The accuracy of a flow meter is its skill in determining the nearest approximation of the true value. Once the precise measurements and characteristics of the fluid and pipes to be used are noted, the next step is finding an appropriate flow meter with a high accuracy rate. Percentage of calibrated span (CS), the percentage of actual reading (AR), or percentage of full scale (FS) units are typically used to indicate the accuracy of flow meters. Percent CS and FS signify that the absolute error will increase with a change in the measured flow rate. In contrast, percent AR signifies no change in absolute error with rising and falling flow rates.
The k-factor is the ratio of the number of a meter’s pulses to the corresponding net volume of the fluid flowing through the meter during measurement; in other words, it is the pulses per unit volume, an indication of volumetric output. The received pulses are continuously divided by the k-factor through the electronic device giving various outputs like rate and factor totalization. 1\k is usually termed as meter factor. Though the frequency of the pulses is directly proportional to the turbine rotor rotational rate, effects like temperature and change in pressure can alternate the k-factor of a meter. So, the manufacturer of the meter should be consulted if the K factor varies with changes in liquid form or with changes in the area of the pipe.
The dependability of the K factor over a particular flow rate is defined as the linearity of the flow meter. This linearity of the flow meter is usually defined as the band, containing minimum and maximum k-factors as well as a k-mean. The manufacturer normally specifies these lower and upper limits as the maximum and minimum flow range of the particular liquid; these constraints are sometimes defined using temperature and pressure instead.