Ultrasonic liquid caustic level measurement

Pulsar Process Management Level Star 110 non-contacting ultrasonic level measurement has been supplied to a major chemical manufacturer, resolving a problem it had in the effective gauging of sodium hydroxide. The Pulsar equipment replaced ultrasonic equipment previously supplied by a different manufacturer which had not dealt with the multiple echoes from the dome top of the tank. The cost-effective measurement system provides easily-read local display for the plant operators.

The tanks are 3.6 m high, with a deep domed top. The ultrasonic equipment that had been previously in place was failing because of the multiple echoes created by the ultrasonic pulse bouncing around the inside of the vessel. Multiple echoes can be a problem, especially when considering relatively short shot applications on liquids. In this type of application, the multiple echoes are almost as significant as the 'true' echo and can swamp the transducer. The echo-processing software can have difficulty in discriminating the correct echo from the mass of competing signals.

Pulsar non-contacting ultrasonic instruments have the advantage of Datem echo processing software. Datem is able to pick out the correct echo among all the competing 'noise' and, once identified, will maintain its contact, following it as the level rises and falls. On rare occasions, even Datem will not pick out the correct echo automatically. In these cases, it is a simple matter to identify the correct level, after which Datem will take over and continue to follow the correct echo against all competing signals.

In this application, Pulsar supplied Level Star controllers, mounted locally to the tanks to provide local display for the plant operators.

The tanks are cylindrical, and the Level Star uses the measurement of liquid level to automatically calculate the volume present in the tank. In addition, the Level Star provides both high and low level alarms to warn staff of potential problems and to identify re-order points.

The transducers used were flanged dB6, with a PTFE face to protect the transducer from the caustic chemicals.

The Level Stars and transducers are easy to install and simple to set up, and, using Pulsar's menu-driven set-up routines, installation was completed in only a couple of hours. The correct level was accurately identified straight away by the equipment, which has provided accurate measurement now for an extended period, proving that Pulsar equipment has the staying power for tough applications.