ABB level transmitter helps Robinson Bros keep the lid on explosive chemical

Thanks to our AT100 magnetostrictive level transmitter, Midlands-based manufacturer of speciality chemicals, Robinson Brothers, are now able to meet strict safety standards regarding the storage of highly reactive carbon disulphide (CS2).

CS2 is so reactive that it has to be stored under a layer of water to prevent it from igniting, and the level of the interface between the water and CS2 requires constant monitoring. Therefore it is essential that any associated measurement devices is safety-critical.

Level measurement was previously achieved using a very simple magnetic float-based device that provided a local indication of the level but didn’t link in to any wider control system. However, an ongoing programme of improvements at the plant called for updated state-of-the-art innovative solution fully enabled for the latest communications.

This [float] principle of measurement had given many years of faultless service in what is a demanding application. In simple terms, magnetostrictive systems can be thought of as a “float on a stick”. The “stick” is actually a sensing tube wrapped around a wire that receives regular electrical pulses. Each current pulse interacts with the magnetic field created by the magnetic float to produce a torsional stress wave in the wire. This stress wave travels at a fixed speed along the wire to a patented piezo-magnetic sensing element in the transmitter assembly. The transmitter measures how long it takes for the wave to reach the sensor, which indicates how far away the float sits as it moves up and down the sensing tube in step with the liquid interface.

As CS2 is so volatile and prone to ignition, it’s one of the few chemicals that requires instrumentation to be certified to the most extreme, ATEX Exd IIC T6, protection standard. It can also be used in safety instrumented systems to meet the tough SIL1 performance ratings.

Thanks to official ABB WirelessHart distributor, instrumentation specialist ICA Services’ partnership with ourselves, ICA was able to recommend our AT100 magnetostrictive level transmitter, which meets both these criteria, providing process signals which output to both our local and site monitoring systems and meeting our own internal requirement of SIL1-capable instrumentation. As such, Robinson Brothers has purchased four additional AT100 transmitters for use on its other CS2 process systems.

AT100 transmitters provide continuous level indication, and transmission of an analog and/or digital signal for monitoring or control. The unique design boosts the resolution of the device to more than 100 times greater than a conventional reed switch-type device.

For more information, email ref. ‘magnetostrictive level’ or visit Alternatively, for more about ICA Services and Robinsons Brothers, please visit or


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