Process automation specialist, ABM Limited were faced with a major challenge when asked to bring it's specialist experience to the Project of upgrading an existing control system at Harlow Chemicals' Alcotex Plant in Essex.

To maintain its market leadership in the manufacture of this U-PVC intermediate, Harlow Chemicals have made a major investment in new plant and technology to enhance control of the Alcotex manufacturing process to meet the demands of increased Production, Quality and Safety.

The brief for the ABM Project team consisted of :

• The development of a secure HMI / PLC Automation System using the latest software package and techniques
• The proposal of a solution to enhance the existing manufacturing process
• To provide a safe and secure working environment for each of the many Zone 1 areas, by use of intrinsically safe (IS), and Exd rated equipment.
• To allow the plant to fall back to the existing control operations during commissioning, if required.

Following an external review of the future automation requirements, the solution provided by ABM including the following innovations:

• The system architecture was developed between ABM and Rockwell Automation to provide a secure Dual Redundant Server, this included two RS ADS servers and three RS ADS clients running Rockwell Automation RSView32 SCADA Development software.
• To improve system response, two Ethernet networks were utilised, a 100MHz Ethernet LAN for SCADA communications and a 10Mhz Ethernet LAN for PLC communications, both of which are supported remotely via a modem link.
• The plant control system consisted of three Rockwell Automation SLC 5/05 PLCs connected on an Ethernet LAN. The software for the three SLC 5/05 PLC's used was developed on RS Logix 500.
• Each PLC has its own set of local Input / Output cards for Analogue and Digital signals, complete with Galvanic Isolation provided by barriers mounted within the same control panel.
• To significantly reduce cabling costs, Two of the above PLCs operated valves via a newly installed Device-net Fieldbus.

The application software was developed by ABM Limited for both the SCADA and PLC functions.
A detailed FDS was developed into code, design and testing was carried out at each stage with engineers and operators from the existing Alcotex plant.
There are over 35 pages of process mimics, 50 Trends with additional plant tags which can be allocated on site and a global alarm facility.

The key factors which led to this project being a great success were: matching our Process Automation skills with the best SCADA Software, effective project management skills to co-ordinate the wide variety of tasks within a very tight time schedules and providing assistance during the commissioning periods.