Many liquids used in processing applications will separate from each other when allowed to settle. They do this either because they are completely immiscible, or they simply have different densities. When a liquid level of each is required, you need a dual level, or an interface level sensor.
Walt Boyes, Editor in Chief at Control and Control Global magazines said that, “interface level measurement is the hardest level measurement application I know of.”
He’s not kidding. Single liquid level sensing applications can be difficult enough. One of the biggest problems is that many interface level sensors rely on too many variables, limiting their application in the real world. So when one of our customers asked for a solution for condensate and water, we decided to design a more widely applicable sensor.
We came up with the MPX magnetostrictive level probe. We went with magnetostrictive technology because of its high degree of accuracy (0.1 inch resolution), and the fact that it relies only on specific gravity for its float. As an added bonus, it’s generally less expensive than popular methods such as guided wave radar. In the end, we were able to pull two level measurements (and a temperature reading) out of a single probe at a lower price point.
Our customer required a few additional things from us. First, it needed hazardous location certification. The MPX level sensor is explosion proof with a CSA Class 1, Div. 1 rating. Second, though several mounting options were needed, the customer needed the entire probe to fit through a standard 2” NPT hole. We did this with smaller floats that match the specific gravity of either liquid.
Finally, we had to tackle high turbulence and high temperature variations. These tanks live in some of the hottest and coldest locations in North America. The MPX level probe had to work in any environment. Additionally, the tanks are serviced by high power pump trucks, which move a lot of liquid really fast. The result is an often-turbulent environment that can bend a long probe if not properly engineered.
With the success of our MPX liquid level sensor, the customer now sells a full-featured bulk liquid inventory tracking system. The system takes an accurate inventory, communicates level data remotely, and tracks the movement of liquid inventory from one location to the next.
The MPX level probe works well in most interface level measurement applications. Limitations are very few and include chemical compatibility and the large physical size of the sensor.