Improved Interface Measurement Monitors Low Dielectric Constant in Polyolefin Plant

One of the largest polyolefin producers in Germany faced a complex interface measurement challenge. They had a vessel with a mixture of benzene and water.

Benzene, an aromatic hydrocarbon that is an important constituent in gasoline, has a very low dielectric constant (low conductivity), which can be problematic for certain measurement technologies.

The level technology used in this case was a guided wave radar (GWR) transmitter mounted in a chamber on the side of the vessel. The chamber had the potential to fill completely and there was a tendency for the GWR to lose signal near the top of the probe due to the low amplitude signal produced by the benzene.

This blog post, part of a Magnetrol® series on interface based on our new white paper, tells the story of how this facility solved this complicated issue of measuring a low dielectric constant.

The Cost

Outside of a sight glass, the GWR was the only level technology in the vessel. The existing GWR signal was being lost at different times of the day, including in the middle of the night, allowing zero remote visibility into the process and causing safety concerns due to potential overfill. Sometimes the signal was lost for hours and the only method of reacquiring signal was to disconnect the power supply and restart.

During these periods of lost signal, it was required to send a technician out to the vessel, no matter the time of day or night, in order to physically view the sight glass.

This occurred many times over an 18-month span, as the GWR manufacturer could not resolve their issues related to the top of probe impedance mismatch, adding substantially to the total cost of ownership of the device.

The Solution

Because of the failed GWR, this user considered moving to a displacer transmitter due to the historical reliability of the technology. However, one last opportunity was given to GWR by installing the MAGNETROL Eclipse® Model 706.

The Model 706, with its specifically designed impedance matched chamber probe, has been performing flawlessly. The impedance matching allows for level measurement up past the process connection (100% level point), providing overfill prevention and measurement in full chambers.

It has eliminated maintenance and service time at the vessel and those inconvenient times when signal was lost. Supporting proof of reliability can also be provided through Safety Integrity Level (SIL) documentation, such as certificates and FMEDA reports.

More Information

For more information on reducing lost signal due to low dielectric constant and other measurement challenges related to interface, download the interface white paper.