Chemical Equipment Update

canal, a major waterway opening through the Western Scheldt into the North Sea and is a major European fertilizer complex. Approximately 70 per cent of ammonia production on site is consumed in the production of finished fertilizer products and produces 1.7million tons each year. Sensornet developed its Halo DTS technology to cope with

the thermal and chemical processes that occur within reactor vessels and columns and which can slowly erode and weaken the structure of the vessel. As this weakening occurs, the skin of the vessel is reduced causing a potential point of weakness/failure. This weak spot has a temperature signature, which differs from the rest of the vessel and can result in a hotspot (or cold spot depending on the process). By detecting this hotspot early on, action can be taken to prevent any accidents and minimise any downtime for the plant. The Halo DTS system allows for continuous monitoring for

up to 4km, responds with update intervals of 10 seconds and can detect a temperature change of less than 0.1˚C. It contains an inbuilt multiplexing module (with either two

or four channels) enabling up to four single ended measurements or two double-ended measurements. User configurable zones

and alarms functionality are also available. The system is packaged in a standalone unit, which contains both the sensing optoelectronics and an onboard PC. It operates with an intuitive software interface and has been tested to some of the industry’s most rigorous standards. By delivering within the tight deadlines imposed by the need

to have the work completed within the down periods, Sensornet was able to complete the monitoring process with the minimal disruption to production. The two ammonia vessels at Yara Sluiskil operate at high

temperatures. The vessels are internally insulated to prevent the shell from overheating. Constant monitoring of the skin temperature (approximately 110 to 150°C) is required to detect the location of any cracks in the internal insulation, allowing any hotspots to be identified and managed from an early stage. The temperature of the vessels can rise up to 350°C when a

hotspot occurs. These hotspots create great stress on the vessel and repairs must be completed during a turn-around. The initial installation of the Halo DTS monitoring cable

on Vessel 1 was conducted during a scheduled maintenance shutdown. The Sensornet team worked around the clock with other service companies to ensure the installation was completed within schedule. The sensing cable on Vessel 2 was installed at the manufacturer’s facility in The Netherlands before the vessel was relocated to the Yara site. Final connection and commissioning was then conducted in a matter of days. Both projects utilised the Halo DTS complete with the integrated multiplexer for bi-directional testing. The former monitoring solution deployed in the vessels,

which used electrical resistivity, was outdated and was not supported by the original supplier. Temperature readings were presented as percentile figures based on maximum and minimum values, which was not ideal. In addition, temperature readings were also taken with infra-red thermometers. Although these provided valuable data they could not be deployed on a permanent basis and would not provide a fully distributed temperature profile of the vessel. Sensornet was required to fill the monitoring gap by

providing a solution that created a complete temperature profile of the reactor vessels with near real-time refresh rates. Monitoring the entire vessels online enables the process to be managed to ensure they performs within their operational tolerances. This results in longer run times between cleaning and maintenance periods. Moreover, the operator can be safe in the knowledge that the vessels are operating safely. The Sensornet solution uses high temperature fibre deployed

in a mesh topology to provide complete coverage of the vessels. This ensures that hotspots as small as 20cm in diameter can be detected. The vessels are divided into a series of zones, each

Fig. 2. The vessel prior to the fibre installation.

10 www.engineerlive.com

containing a minimum of 10m of sensing cable. The Sensornet Halo DTS is positioned within the local control rooms meaning that no active hardware is required in the field. The DTS communicates directly with the site’s supervisory control and data acquisition (SCADA) system via OPC computer process control tags. This illustrates the average and maximum temperatures of each zone on a vessel schematic and refreshes the temperature every 10 seconds. In this instance automated alarms are activated by the SCADA system. If required this can be achieved directly from the DTS via contact relays. Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44