A flow meter is a special device that measures the amount of gas or quantity of liquid or its flow rate moving through the pipe. Too little or too much gas or liquid flowing through the pipe may result in the malfunctioning of the machine. A proper reading is imperative at all times. Flow meters are used by measurement and test professionals in applications that depend on accurate flow measurements such as in utilities, energy, aerospace, water management, HVAC, pharmaceuticals, and agriculture industries. Flow meters are also frequently used to ensure optimum functioning of different types of industrial machines. Due to their frequent use, flow meters are susceptible to inaccurate readings. Even the most broken-in flow meters can easily veer off of calibration. It is only natural as instruments’ performance weakens with time due to certain parts wearing out or breaking. For instance, flow meters are easily affected by dirt that exists within the media that travels through them and by corrosion.
Since it is imperative to have high accuracy in taking measurements, regular calibration of a flow meter is necessary. Calibration provides assurance that the flow meter’s readings are actually what it states. Proper calibration of machinery and tools in any industry is part of the current Good Manufacturing Practice or cGMP as well as stringent FDA regulations. Just as there are standard ‘best practices’ in calibration, these principles apply to flow meter calibration as well. There are specific best practices that need to be implemented to receive the most accurate results from your flow meter.
These five best practices for calibrating flow meter are:
1: Calibration Standard
Proper calibration depends on a standard that is accurate. Thus, the calibration has to be even more precise than the flow meter it will measure. According to industry standards, the rule of thumb regarding calibration standard is, that it has to be four times more correct than the flowmeter that is tested. However, this rule of thumb may adapt depending upon specific requirements of the test.
A cost is also associated with seeking the most accurate calibration standard. The cost is proportionate to the breadth and quantity of test points recorded. Differential-producing meters are used to acquire these data points. Some of these meters may include several sets of piezometers, which will increase the cost. Thus, base price is determined first which includes a pre-decided number of data points and taps.
The remainder of the cost related to flow meter calibration includes the removal, transportation, and reinstallation of the flowmeter post calibration. These costs are quite high and depend on where the meter is located within the factory. A facility that has a meter bolted to downstream and upstream piping at ground level will have lower costs. The cost of flow meter calibration varies between $5,000 to $75,000 USD.
This best practice is an important and necessary form of documentation. It measures the standard as per which the flowmeter is calibrated. The standard used to calibrate your flow meter should be traceable to one that is recognized within the industry. Doing so helps to authenticate that the calibration system is capable of accurately calibrating the flow meter.
During traceability, the readings of your flow meter are compared against a standard, usually under controlled laboratory testing conditions. The standards used for comparison are typically traceable to national and international industry standards.
3: Rate of Flow
As a rule, the flow rate between the flow meter and the calibrator has to be consistent. Since calibration readings are actuated in real time based on the flow received from the flow meter, the flow must be constant to obtain a sound reading. It requires a thorough understanding of the properties of gas and fluids that are measured. Their properties have an effect on the flow meter and variations in these interaction affect measurements provided by your device.
4: Consistent Measuring
Apart from evaluating calibration methods, the flow meter needs to be examined to ensure the absence of significant issues that may alter the accuracy of measurement. A certified service provider or calibration laboratory can ensure that proper measurement procedures are followed, uncertainty is recorded, and the traceability standards are met. The lab will also monitor fluctuating temperature changes, which can also impact the flow meter. Having your flow meter tested by a professional also ensures its continued and proper functioning.
When the calibration test is being performed, efforts should be taken to ensure that the same conditions should be maintained as when the flow meter operates. There are specific factors, which can influence how a flow meter will operate. These are:
- Flow disturbances at the site
- Electronic interference
- Heat content of the gas or liquid measured
If calibration does not take these factors into account, you may not get a proper reading. One of the best ways to ensure that every factor is being taken into consideration is to measure your flow meter during operation in its daily capacity.
The tips mentioned above are five of the leading best practices for calibrating flow meter. Failure to calibrate your flow meter on a regular basis will negatively influence performance, leading to detrimental consequences, both to the employees who are working in the industry and to the consumers who purchase the products of that company. For example, a calibration in a food processing plant can have negative consequences for the safety and quality of the food products. If you take an example using natural gas or crude oil, the smallest mistake in a custody transfer application will result in millions of dollars in cost for customers. On the other hand, calibrating your flow meter too frequently can become a costly affair without any benefits.
By adhering to the five best practices mentioned above: maintaining calibration standards, traceability, simulation, consistent measuring by an accredited professional and rate of flow, you will ensure that your flow meter is giving out accurate measurements.