| installing an ultrasonic flow meter the most important | | | | For horizontal pipes a time of flight ultrasonic flow |
| consideration is the medium to be measured. Raw | | | | meter should have the transducers fitted on the side |
| sewage usually requires a Doppler ultrasonic flow | | | | of the pipe. This will allow more accurate flow |
| meter whilst distilled or clean water requires a time of | | | | readings as generally air bubbles are located on the |
| flight ultrasonic flow meter. However, what about | | | | top of a pipe while sediment falls to the bottom. |
| applications that use a combination of liquids or liquids | | | | Doppler transducers are generally installed on the top |
| with small particles? For applications where the media | | | | of the pipe. |
| has particles of 100 PPM or more a Doppler ultrasonic | | | | A typical time of flight ultrasonic flow meter will have |
| flow meter would be the most suitable device to use. | | | | two transducers, one will be specifically for the |
| For media with particles smaller than 100PPM, such as | | | | upstream direction of the flow, while the other for |
| oil, sea water, or even gray water a time of flight | | | | the downstream. If you are unsure if the flow |
| ultrasonic flow meter types are most suitable. | | | | direction, you will normally see a negative flow rate if |
| A time of flight ultrasonic flow meter requires a | | | | you have installed these incorrectly. If the |
| totally full pipe to work. While a typical Doppler | | | | transducers are installed correctly and you are still |
| ultrasonic flow meter is more suited to a completely | | | | having a problem in obtaining a correct figure from |
| full pipe, it is possible under certain conditions to utilise | | | | your ultrasonic flow meter, try different sound path |
| these units on partially full pipes. | | | | settings. This will require you to move your |
| Sensor Installation | | | | transducers up and down the pipe as the ultrasonic |
| In an ideal condition a straight length of horizontal | | | | wave is reflected a different number of times on the |
| pipe that is at least fifteen pipe diameters long is | | | | pipe walls. Generally, the more transit paths, the more |
| required. This should be free of valves, inflow and | | | | accurate your reading. However, the more transit |
| outflow diffusers and should be as far away from | | | | paths can also lead to a weaker signal which can |
| pumps as possible. When using a time of flight | | | | cause setup difficulties; this is why it is recommended |
| ultrasonic flow meter on an installation that has a | | | | that you always start with the simple V |
| pump or T-section, a straight length of up to 50 pipe | | | | method. |
| diameters to obtain an accurate flow reading. | | | | Take care in setting the exact liquid type, sensor |
| Most ultrasonic flow meter models are unable to | | | | spacing and pipe measurements. If you have |
| measure downward flow in a vertical pipe. The pipe | | | | incorrectly programmed any of these variables in |
| surface must also be clean and free from rust or | | | | your ultrasonic flow meter you will get either an |
| paint bubbles. Also the ultrasonic flow meter | | | | incorrect reading, or no flow reading at all. |
| transducers must be clean and have a substantial | | | | Once you have taken the time and accomplished |
| amount of couplant material to make a good acoustic | | | | your first ultrasonic flow meter installation, future |
| connection. | | | | measurements will be much easier. |