Over the years we have had quite a few customers approach us about measuring their tanks on their trucks. While this unique application presents a variety of challenges, and often requires some fine tuning, you can get a reliable and accurate reading on a tank truck with the right liquid level gauge.
We have found that there is not a single level measurement technology that will work on all tanks on trucks. There are many variables to consider. However, one technology does seem to stand out among the rest.
Before we get to revealing exactly what that technology is, let’s take a quick review of some other popular liquid level gauges used in this application, as well as go over some tricks on how to get them to work at optimal performance.
Ultrasonic sensors have been a popular choice for most liquid level measurements. This is because they are easy to install and they don’t come in contact with the liquid. However, when it comes to measurement on truck tanks, things get a little more challenging.
The main challenge is that the liquid will be moving and sloshing around in the tank as the truck travels. This makes it difficult for the liquid level gauge to get a good reading. This may also cause problems if the liquid splashes on to the transducer face, especially if the liquid is a hazardous chemical.
An effective way to diminish turbulence is to use a stilling well (see "The Art of the Stilling Well"). This will usually calm the liquid inside the pipe so the sensor won’t get splashed and make it easier for the level gauge to get a good reading.
Then there are temperature gradients that may cause concerns. Being outside in the sun, tanks on trucks will often get quite hot. This means that the difference in temperature between the sensor housing and the liquid may fluctuate. This can lead to inaccuracies in the readings.
One way to combat this is to turn off the temperature compensation feature in the liquid level gauge to avoid over compensation, or by installing a shade over the sensor.
Pressure sensors are also susceptible to fluctuating temperatures. Some liquids will expand or contract significantly as temperatures fluctuate. Since pressure sensors rely on the specific gravity of the liquid to remain constant, they will not notice an increase in level due to an expanding fluid.
Due to how the liquid level gauge operates, there is no way to negate this effect unless you use a temperature sensor in conjunction with the pressure sensor, and then use the raw readings to calculate a compensated reading. This is often not worth the effort when other options are available.
In our experience we have found this type to be the best option. Since ball and stick gauges rely on the position of the float on its stem, it is not affected as much by fluctuating temperatures. As long as the specific gravity does not drop below the specific gravity of the float you will still get an accurate reading for the liquid level.
Mechanical float level gauges also tend to handle turbulent fluids better as well. The float will rise up and down with the rolling fluids, therefore, it is still recommended that a stilling well is used with these gauges. This way you will get the best reading possible.
If you have any questions on using liquid level gauges for tanks on trucks feel free to contact us. We will be happy to help you find a solution for your unique application.
