The following article was published in Process & Control Today
Posted on 09/13/04
Editor: John Houston

Eurotherm Control Solution Chosen for Purified Water System at Moorfields Hospital

A new 'state-of-the-art' Pharmacy Manufacturing Unit (PMU) at Moorfields Eye Hospital NHS Trust, London, features sophisticated Water for Injection (WFI)and Clean Steam generation systems for cleaning and sterilisation purposes.

The system, designed and engineered by specialist consultants Honeyman Group, uses a Eurotherm T800 (Visual Supervisor) based control solution for all supervisory control functions. The system meets the demanding requirements of FDA 21CFR Part 11 with respect to electronic records. The products of the system are used for a variety of manufacturing, cleaning and sterilizing purposes. WFI is used for production, a number of equipment washing machines and cleaning in place (CIP) tasks, while Clean Steam is used for high temperature autoclaves and steam in place (SIP) purposes.

The complex system consists of three packaged plants, operating independently within an overall supervisory control architecture. In the first plant, raw water is purified by passing it through reverse osmosis filters and de-ionisation processes to produce Purified Water. This is stored as feed water for two additional processes, clean steam generation and distillation for WFI, and distributed throughout the building to points of use. The entire process is predominantly automated and thus requires minimal operator intervention.

The three individual packaged plants are self contained modules with integral on-skid local control systems, hand shaking locally and communicating with the central control panel through hard wired connections. A number of independent local control panels are also provided for control of dispensing at WFI & Clean Steam points-of-use. The central control panel is also hard wired into the Building Management System (BMS) for soliciting an operator response to alarm conditions.

The Eurotherm T800 at the central control panel provides the operator with a graphical process interface, and is used to execute across-network control operations. Also known as Visual Supervisor, the T800 is a powerful multifunction controller with integrated touch screen display and data logging facilities. It provides all the features required to control and monitor complex processes like this one. It is operated here in conjunction with five eight-way Eurotherm 2500 I/O controllers.

The five panel-mounted 2500 controllers are used primarily for data acquisition purposes, and interconnect with the T800 Visual Supervisor via an open 'Profibus DP' network. 2500 configuration is achieved using proprietary Eurotherm 'iTools' software. Three of the 2500s are mounted with the central control panel, the remaining two operating remotely at local control panels. Some of the I/O controllers execute discrete logic functions, while Eurotherm 'LinTools' software is used to open and close vessel filling valves via the T800. All valves throughout the process also have hard-wired interlock arrangements, giving a failsafe function on conductivity alarms.

Standard features of the T800 controller include a clear touch screen display for screen navigation and execution of operator commands, batch management to ISA-S88 with batch log, recipe & setpoint programmer, accurate continuous and sequential control, support for Modbus and Profibus, as well as time synchronisation. In this particular application, the controller provides process mimics, bar-graph displays, historic trends, alarm and event logs, keeping the operator fully informed of system status.

A key issue in specifying the T800 solution for this WFI /CS system was Honeyman's clear requirement for creating detailed tamper-proof records of key parameters within the essentially analogue processes. At the same time, the processes required continuous control to fine tolerances.

Process data is logged continuously by the T800 Visual Supervisor. This uses flash memory for short-term data-storage, with an integral 3.5" 1.44MB diskette for long-term storage. Data is recorded in a proprietary tamper proof binary format, while preview software allows restricted read-only access to the data stored on diskette via any standard PC.

In this system, each diskette can contain at least 10 days worth of data. Process values and trending data are logged once every minute, with events and alarms being logged as they happen. Diskette status is checked daily by the operator. An operator alarm, activated through the Building Management System, is raised if the diskette reaches 95% capacity.

In terms of access control, the T800 provides four levels of password protected access to authorised personnel only. A time lock facility ensures that access is cancelled and locked after 15 minutes of operator inactivity. The entire system was designed and commissioned by Honeyman Group Ltd. This specialist consultancy provided initial consultancy to MEH, design, supervisory implementation, writing of protocols, validation and final commissioning. System software was designed, tested and commissioned in accordance with the GAMP3 Guide For Validation of Automated Systems in Pharmaceutical Manufacture.

Roger Newton, Honeyman Project Manager for the MEH System, believes that the T800 based control solution was the best possible. He commented: "Visual Supervisor offers a number of powerful hardware capabilities, supported by a proven suite of configuration and operation software tools designed for both analogue and digital parameters. We have therefore been able get exceptional functionality into compact, cost-effective package. This amounts almost to DCS performance without the high cost." "That, together with the high level of support provided by Eurotherm's technical people, made this an obvious choice. And the solution not only meets the current needs of the system but has the flexibility to meet future needs as well."