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Redundant Level Measurement for Chemical Overfill Prevention

In the chemical industry, level instrumentation is required to measure continuous liquid levels in flammable tanks and to prevent potential overfill. Chemical plants stringently enforce environment, health, and safety (EH&S or HS&E) management practices with the expectation that their suppliers have a similar culture. One way of achieving a high level of reliability in instrumentation is to provide redundant level measurement using separate technologies—in many cases, one technology for continuous measurement and the other as a high level switch for overfill prevention.

Case Study: Chemical Overfill Prevention

Magnetrol® was able to assist a chemical manufacturer in making their plants safer through the usage of two technologies for redundant level measurement. “KMCO is one of the world’s largest tolling facilities and our customer base reaches all over the world,” said Daniel Charles, an engineering manager for KMCO in Crosby, Texas. “Because of the turnover of multiple products in tanks, finding the right fit for a level transmitter was difficult. We went through several vendors and couldn’t quite get what we needed. After meeting MAGNETROL, we knew we were going on the right path.”

Redundant Technology for Reliable Measurement

Guided wave radar (GWR) technology was chosen for continuous level measurement in the facility. GWR is the fastest growing level measurement technology in the market, with MAGNETROL pioneering the first of its kind in the late 90s. The MAGNETROL GWR transmitter, Eclipse 706®, is a two-wire, 24 VDC loop-powered transmitter based upon the technology of time domain reflectometry (TDR). TDR utilizes pulses of electromagnetic energy transmitted down a wave guide (probe). When a pulse reaches a surface that has a higher dielectric constant than air, a portion of the pulse is reflected. The transmit time of the pulse is then measured.

For redundancy and greater safety, MAGNETROL also recommended ultrasonic gap switches, a popular technology for high level indication. The ultrasonic transducers can be supplied in single or dual-gap design, and with relay or two-wire current shift outputs from the electronics. The MAGNETROL Echotel® ultrasonic contact switches utilize ultrasonic energy to detect the presence or absence of liquid. They are available for single point (Model 961) or dual point (Model 962) level detection. Both GWR and ultrasonic gap switches are suitable for use in Safety Integrity Level (SIL) 2 loops.

Due to space limitations and the added expense of having multiple process connections, KMCO requested to have both technologies installed on the same process connection—a single 3″ flange. Open communication and accurate feedback allowed for the special design to be accommodated. Wireless communication was also desired, and the level devices were seamlessly integrated into the third-party wireless transmitter.

The Results

KMCO was impressed with the ease of installation and reliability of the MAGNETROL transmitters. “By using MAGNETROL products, we are able to make the operator more productive and make the process safer,” Charles said. “Using MAGNETROL has streamlined our tank level indication installation, allowing us to install more for less cost than the competitors. We have over 1,000 tanks at our facility and with the customer service and quality products we receive from MAGNETROL, it will just be a matter of time before all of them have MAGNETROL devices to depend on."