How to successfully use ultrasonic sensors in the pipeline

- Jun 04, 2019-

The successful operation of the ultrasonic sensor in the pipeline has strict piping requirements. The performance of the ultrasonic sensor is limited by physical principles and can obtain accurate results in the pipeline. However, many factors must be considered in order to be successful.

Many customers who consulted OSENON requested that the ultrasonic sensor be installed in the pipeline. During the testing and development cycle, we found some considerations and requirements that must be met for the success of the application. When all of this is met, the user can reach the level of success required to measure the level of liquid in the pipeline.

ultrasonic in pipe

A common requirement is for the sensor to operate in a 2 to 4 inch diameter pipe. The technical engineer of the work network completed the test to verify such operations. The technician's test found that the sensor could be placed in a seamless tube. The test was carried out in an 8 foot, 40 meter PVC pipe. Below we will follow the work of the small network to learn how to successfully use ultrasonic sensors in the pipeline.

Add a two-foot pipe with a coupling to the test. The result is that the sensor is far from the joint but does not extend beyond the joint. The reason is that when a joint is added to the pipe, typically the joint is not smooth and leaves a gap between the two portions of the pipe, which creates a position where the sound is reflected back to the sensor, resulting in a distance from the joint.

Another important consideration is the condensation of droplets inside the pipe, and the sensor typically reports the extent of these droplets rather than the liquid level. This is because the droplets reflect the sound back to the sensor.

It is common to use sensors in a well, placing the sensor in a larger tank to ensure that the level is “stationary” for measurement. It also prevents external objects or debris from interfering with the sensor's range readings. 

For best results, two conditions should be met.

The first condition that must be met is that there must be no water droplets inside the pipe. This can occur in liquid or condensed water flowing down from the top of the pipe.

The second condition is that any internally accumulated debris or sludge must be removed. This usually occurs at the level where the liquid is usually located. This can be easily corrected by regularly cleaning the pipe. Sometimes this is not a viable requirement for the user.

Other considerations for pipeline operation

Now that you know the types of pipes you can use, there are some things you must pay attention to when operating the sensors in the pipes.
1. Some customers have found sensors that work in pipes that are 6 inches or larger in diameter. Technet technicians recommend that users consider a pipe diameter greater than 8 inches. This allows the liquid surface to become a larger target with respect to many considerations of pipe operation.

2. When operating in a pipe with defects, dents, jingles and breaks, the defect may produce the largest ultrasonic reflection, causing the range to be reported as imperfect. Engineering around these types of problems is limited while still providing usable range data.

3. Multipath reflections (eg, paths that directly reach the surface and other paths that bounce off the sides of the pipe and then strike the surface and bounce back to the sensor). When the temperature in the pipe changes, these reflections may cause the target to look closer and further. In some cases this may be between 5-10 cm, but usually 1-2 cm.

4. Phase cancellation may occur, which causes the acoustic reflection from the liquid surface to disappear. This can happen at some distance or temperature in the pipe. When this happens, the sensor does not see the liquid level.

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