In a recent article for Industrial Products Process and Technology Magazine (IPP&T), Magnetrol® Global Product Manager Bob Botwinski discusses how guided wave radar (GWR) and non-contact radar can work together to provide reliable level measurement. A MAGNETROL blog post on March 22 provided an excerpt from this article that focused on the benefits of GWR and non-contact radar level measurement versus traditional instrumentation. Here’s what the article has to say about how to choose the right radar technology for each application:
The Best Applications For Each Technology
Due to the similarity between guided wave radar and non-contact radar with respect to both performance and capability, there will obviously be some overlap in the application set. Experience, comfort level, and plant-specific standards may dictate a user’s decision as which to use. However, we all know that “force-fitting” a technology to any given application can result in post-installation issues. Therefore, there are some basic application questions that, when considered for a specific application, will quickly guide a user to the proper radar technology.
Three basic parameters, considered in this order, can help a user determine the best technology for radar level measurement applications:
1) Measurement Range
Since GWR requires the probe to be as long as the measurement range required, non-contact radar is typically more suitable for large storage tank applications.
Shorter range, quicker moving process control applications, such as those in side-mounted chambers, are typically better suited with GWR.
2) Process Conditions (Temperature and Pressure)
Some GWR probes have probes that can accommodate maximum temperatures up to 850F (450C) and maximum pressures up to 6250 psi (430bar).
Some radar antennas also have a maximum operating temperature of 850F (450C), but are limited in a maximum pressure rating of 2320 psi (160 bar).
Therefore, GWR should be considered for those more difficult high temperature, high pressure applications with pressure above 2320 psi (160 bar).
3) Dielectric constant of the process medium
With both GWR and non-contact radar, the dielectric constant (ε) of the process medium dictates the size (amplitude) of the reflection from the surface of the material. High dielectric media like water (ε = 80) produce large reflections that are easily detected by the transmitter. On the other hand, low dielectric hydrocarbons (ε = 1.7 -3) result in low amplitude signals that may be difficult to detect reliably.
In GWR, with the high frequency signal being focused and transmitted down a waveguide, very little energy is lost as the signal travels down the probe. On the other hand, significant signal attenuation can occur with non-contact radar devices in some applications. Being more efficient, GWR is, in general, the preferred technology for low dielectric applications (ε< ~ 2).
It must be stressed again that there can be other, perhaps non-technical, reasons one may choose the technology not meeting the criteria above, but these three parameters, when considered either separately or together, are a good start in guiding the user to the most robust solution.
The IPP&T article contains more information on GWR and non-contact radar, including what to look for when selecting a radar-based device. In addition, MAGNETROL has created a radar solutions site where you can learn more about our radar level measurement technologies.