Modern Control Panels Improve Reliability Of Chemical Process

In 1995, Harlow Chemical (HARCO) spent 13 million pound on new plant to increase its production capacity of polyvinyl alcohol by 40 per cent. The expansion saw the introduction of hydrolysis kettles and solvent extraction equipment similar to those already in place. However the new control panels supplied by Max Wright Limited are considerably more powerful in terms of their ability to monitor process conditions and alarms.

Three local, zone 1 explosion proof panels control the hydrolysis plant, solvent extraction and product dryer respectively, the first incorporating a mimic of the process. They all report via intrinsically safe barriers into a main control panel which houses the pneumatic solenoid valves, bead reactor control and programmable logic controller(PLC).

Said Harco's site engineer, Anthony Colley, 'All the electrical hardware was produced competently by Max Wright but their real forte was the development of the PLC software. As a result, the extension to our polyvinyl alcohol manufacturing facility is more reliable than the original plant, reducing operator involvement and the associated costs.'

A Toshiba PLC, type EX100, performs plant interlocks and sequence control involving dosing various chemicals plus a catalyst into the system to produce polyvinyl alcohol. Marketed under the Alcotex brand name, it is used in the polymers industry, notably as a suspending agent in the manufacture of suspension PVC. Harco, a joint venture company owned by Clariant and Yule Cato, is the only UK manufacturer of this specialised product and the global market leader, exporting to over 40 countries.

One of the main benefits of the new control panels has been the move away from pneumatic to electronic valve actuation. This allows much more parameters such as temperature, pressure and chemical levels in the various tanks to be measured. In addition, staff no longer had to adjsut valves during production to optimise the process.

With manufacturing sites in Ware, Herfordshire and Yaxley, Peterborough, Max Wright Limited is one of the few companies which designs and builds control panels in their entirety from steelwork fabrication, through sourcing of componentry and all electrical wiring, to in-house development of software for controlling complex PLC configurations and linking with operator interfaces. The latter may be anything from a simple text display to a computer running SCADA(supervisory control and data acquisition) software.

The privately owned company, which has been established for 40 years, operates to a quality standard equivalent to ISO 9000 and has a strong track record in the supply of control panels to 'sterile' industries such as water, food and brewing. Projects have also been carried out in petro-chemical, meat, cement and glass manufacture.

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