Water Flow Meters: Guide About How to Calibrate
Why is calibration vital, and what does it involve? These are possible questions running through your mind right now. We’re here to help you understand and get the answers you’re seeking.
So, this is a comparison between a known measurement (the standard) and that using your instrument.
But if this is not subject to a metrological standard, calibration can be mandatory as per the underlying standard. Flow calibration of the meters is necessary when there is a need for defensible accuracy.
It’s essential to have a daily calibration. But it will depend on the industrial operation. For instance, this is critical against a built-in calibration meter in the petroleum industry.
Best Calibration Practices
Traceability assures measurement accuracy, removing all uncertainty to both a customer and manufacturer. Since calibration compares the meter and a standard, this must measure the exact quantity using an objective standard. And flow calibration can be unique;
- Where there is a 1″ gauge block for the machinist’s micrometer
- Where there is no “gallon per minute
- Where there is a cubic meter per hour
- A test artifact is required to run through a flow meter to perform the calibration.
Calibration of large-scale flows uses the gravimetric method. And it involves scales, timers, and temperature measurements to determine the flow under test (MUT). The devices measuring these parameters must show traceability to the highest level. They can be national or international standards.
What are the two primary objectives of water flow calibration? Typically, the accuracy of the standard must be ten times that of the measuring device tested. But most standard organizations accept an accuracy ratio of 3:1. The accuracy of the standard must be ten times the accuracy of the measuring device tested. But most standards organizations accept an accuracy ratio of 3:1.
A clear understanding of the fluid properties of water at the calibrating conditions is critical. Why? It provides appropriate calibration data. But certain factors may affect the interaction between the flow meter and the water. These include the water temperature, operating pressure, density, conductivity, and Reynolds number. What is Reynolds’s number? It’s a nondimensional value formed on the viscosity and velocity of the liquid through the meter.
It’s best to calibrate differential meters such as Venturi meters, orifice plates, and flow nozzles at the operating Reynolds meter number.
And if you want to avoid errors of using incorrect fluids, you must perform a meter calibration meter using a fluid with properties close to the actual operating conditions.
Cost Of Calibration
While flow calibration of the device is essential, the cost of doing this is something to consider. Differential meters have multiple piezometers, which may add to the cost of calibration. They are nonlinear devices where the signal varies with the square of the flow. These meters require additional data points to specify the meter performance. And this usually records the size and number of test points.
Simulated Installation Conditions
Meter installation is critical as it ensures the best piping conditions, whether upstream or downstream of the device. But the velocity distribution of the flow entering a meter can impact the response of the meter installed. The flow streaming in must have a developed velocity profile. Although, this will depend on the diameter of the internal pipe, its length, roughness, and Reynold’s number. One of the best ways of achieving this is providing various diameters of upstream pipe that are not interfered with by valves or diameter changes.
The primary objectives of the water flow calibration are to check the accuracy of the device and your measuring instruments. And the second one is to determine the traceability of the measurement. Calibration is an essential feature of instrumentation in most industries requiring high accuracy. And it requires a negligible percentage of error. Some of these include Oil & Gas and Petrochemical.