Why Must You Maintain Flow Meter Accuracy?

Flowmeter Accuracy | Flowmetrics

In the fight for achieving maximum efficiency, businesses in every sector of the commercial world view energy savings as a key part in this battle.

To achieve any form of financial savings for the company through improvements in efficiency greatly depends upon the control system that is in place, to which accuracy is a key component.  But accuracy is a deceptive word and knowing this will help us move closer to understanding the necessity for maintaining flow meter accuracy.

Accuracy, Precision, And Exactness

In general conversation, there is little difference between these three terms, but this is not correct in the truest context of their meanings.

Accuracy is a term used to depict an approximation to either the desired target or a true value. This means that there is a margin of error allowed within something’s accuracy and it’s these parameters which are used to create the window with which we can claim if something is accurate or not depending upon if the measurement falls inside or out of this target area.

Precision meanwhile represents how closely repeated values relate to each other. This means that a value can be repeatedly inaccurate but precise in its own way as it achieves the same result.  It also means that something can be consistently accurate within set boundaries, whilst also being imprecise in its own standards.

Exacting is a combination of being both accurate and precise to repeatedly achieve either the desired target or a true value on every occasion, exactly as required.

Limitations Of Flow Measurements

The primary function of a flow meter is simply to measure the rate at which a fluid is flowing, irrespective of which application it is being used for. This information can then be used to control systems to achieve performance levels within and of the holistic system and in doing so, create savings in product materials, energy, time and other such commodities which streamline the operation.

The measurements carried out by flow meters and the associated peripheral devices which constitute the flow control system are not of an exacting nature, and there are many factors which can affect the quality of information produced by flow meters. These are often known as the five V’s, which are:

  • Variability
  • Variety
  • Velocity
  • Volume
  • Veracity

As these measurements can never plausibly achieve consistent exactness, there is, therefore, an acceptance that accuracy is another parameter within the system that can be improved upon in trying to achieve a maximum running efficiency.  The accuracy of a flow meter and other detection equipment is thus produced with an operational error percentage that denotes the expected level that the device can be expected to comply to.

Varying Degrees Of Flow Meter Accuracy

Regardless of the type, manufacturer or model of flow meter used in a system, there are two main elements of flow meter accuracy which need to be taken into consideration.

Firstly, the actual stated accuracy range of the equipment which will be provided as a percentage figure such as +/- 0.2%. This would indicate that the device has a 0.4% range of accuracy, however, to achieve this in realistic operational situations, it would require every other aspect of the system to operate at maximum potential, or to put it another way, to work perfectly.

Secondly, once accounting for other factors, such as the accuracy ranges of external sensors and the flow profile of the pipes transporting the fluid, there is another major concept to account for, namely the rangeability of the flow meter. This is the parameter range of the fluids velocity in which the flow meter can successfully measure to its full potential.

Often referred to as the turndown ratio, this is the difference between the highest and lowest flowrates that the equipment can measure to its stated accuracy level. Once the flowrate either exceeds or drops below this range, the achievable accuracy of the equipment quickly dissipates. The expected system dynamics is, therefore, a key factor that should be taken into account when choosing a suitable flow meter which will be fit for purpose.

Aside from the operational aspects of the flow meter, there is another major factor which heavily affects the accuracy achieved in field measurements.

Increased Flow Meter Accuracy Levels Through Calibration

With a host of factors that can have a large, adverse effect on the resulting measurements made by flow meters, it is critical that the equipment is configured correctly upon installation by trained technicians, who will ensure that the system runs up to and above its optimal potential.

An important point to remember in the initial installation process is that a calibration test must be carried out under normal operational circumstances in order to provide a true reflection of the systems activity. This means that after the initial setup has been completed, the system must then be allowed to run until it reaches a natural level of fluid behavior, which can then be used to configure the equipment accordingly.

There is also a further partial solution now available in the form of flow computer software packages which can account for minute errors and adjust accordingly to maintain a higher degree of flow meter accuracy. But in practice, there is only one true method that can maintain a high level of flow meter accuracy within the control system.

Maintenance And Upkeep

In addition to setting up the equipment correctly on installation, a regular series of calibration tests are required to both align the equipment and test the integrity of the individual components in the setup.

Similar to any machine that features moving parts, the flow meter is liable to depreciation that will result in a reduced level of performance and effectiveness.  Therefore, flow meters must be subject to routine cleaning and re-calibration tests to verify the device against an industry-approved standard.  This can be achieved through either system diagnostics which can highlight any irregular characteristics or independent software packages that run parallel to the existing equipment to provide a comparison.

With a small degree of error within each component of the chain involved in providing the flow rate measurements, a large level of overall inaccuracy is attained. So whether you choose to use in-house engineers, specialist service companies or representatives from the manufacturer or supplier of the equipment you use, it is imperative that this process is taken seriously to battle against the constant erosion of time and take a step towards achieving maximum efficiency.

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