A flow meter
is used to measure the rate that fluid or gas travels through it. They are used by professionals in a wide variety of applications where it is crucial to have accurate flow measurements. These include applications such as gas meters, gear meters, ultrasonic flow meters and electromagnetic flow meters. With appliances such as these, it is very important to calibrate the flow meter on a regular basis. This will ensure that the measurements of your flow meter are always as accurate as possible. Even the most reliable flow meters
can begin to deteriorate over time when it comes to their performance and accuracy. This could be due to general wear and tear, along with the age of the equipment. Your flow meter can also be affected by other factors such as incorrect installation or dirt and corrosion. Knowing how to calibrate your flow meter correctly will be extremely beneficial in the long run.
Every so often flow meters need to be calibrated. This means their performance must be compared to a certain standard, and the meter’s deviation from that standard must be determined and corrected.The general rule of thumb is that your standard should be four times more accurate than the unit you are testing. However, this can vary depending on the calibration requirements.Your standard should be traceable. This enables you to prove that your measurements are what your flow meter
depicts, within specific ranges.The flow rate between your unit and the calibration standard must be steady.The system flow rate should not vary with time because the flow rate of the standard and that of the meter are compared in real time duri
ng calibration. All media must be measured by the flow meter at the same time as the calibration standard and there should not be any leaks or temperature changes that could affect the measurement. You should perform the calibration under the same conditions in which you would use the flow meter to get the most accurate results. Flow meter calibration is performed by accredited laboratories that are certified by the National Institute of Standards and Technology. A certificate is provided to certify that the flow meter
is performing to the required standard. One method of calibration involves weighing the amount of fluid that flows through the meter during the procedure. This is typically done with an accurate weigh scale that also needs to be approved by the National Institute of Standards and Technology. This is said to be the most precise way of measuring the volume of flow. There is also a method also known as ‘wet’ calibration. This method is frequently scrutinized, however, because it doesn’t need to be approved by the National Institute of Standards and Technology.
The calibration of gas meters has become vital. There are many ways of performing this type of calibration, including the Bell Prover (which provides a certain volume to the gas meter under test making it easy to monitor its performance), the Gravimetric method (involving an accurate weigh scale that defines the amount of gas flowing through the meter during the procedure and the Test Bench ( a system that uses master meters as reference standards. The same amount of volume flows through the master meter and the gas meter under test, and the two meter readings are compared to each other. This method is widely used by many calibration laboratories all over the world. Depending on the size of the master meters, high flow rates can be achieved and very large gas meters can be calibrated.
The calibration of an ultrasonic flow meter
can be completed with the use of a piston prover. With the piston prover, a certain volume of water is pressed through the flow meter. When the calibration has been done successfully, a calibration certificate is issued. The two critical parts of the piston prover are the diameter of the cylinder and the position of the piston which displaces the water. The movement of the piston is determined by a ruler mounted on the piston rod. The volume displaced through the piston is measured using the internal diameter of the cylinder and the movement of the piston. This volume is then compared with the volume that is measured by the meter being tested. Calibration with a piston prover can be completed up to a diameter of DN 150. Bigger diameters are calibrated on either a master or calibration rig. In general, the accuracy of a calibration rig must be 10 times better than that of the meter being tested. Usually, the performance of the flow meter
is observed at two different flow rates.
So, no matter what type of meter you have, there is always an ideal method of calibration. It’s much better to have your flow meter checked regularly than to leave it until its functions begin to deteriorate. Calibration is always a beneficial procedure – think of it in the same way as an MOT! Always be on step ahead with regards to your flow meter…