Automation

AutomationSystem Investigation

ContentsIntroduction to Process2Specification of Problem3Proposal for solution3System Design Specification4Instrumentation and Control Devices5Temperature Device5PH Device7Level Transmitter8High and Low Level Switches10Flow Meter11Process Control Design13

Introduction to Process

I work in a pharmaceutical plant manufacturing Flu Vaccines for distribution globally. Due to the nature of the business and the live egg waste involved it must be suitably treated. We have classifications of liquid waste and all liquid waste falls into these two classifications. Contaminated and non-contaminated waste. Contaminated waste currently is treated through our waste facility on site and this system is fully automated. Non-contaminated waste can be distributed through the site main water drain. Recently we have had various complaints from the local water board in regards to condition of this waste during routine sampling and they have placed restrictions on the pH and temperature of outgoing waste. Currently our system Pipes all non-contaminated waste into local storage tank outside the plant and when it gets full (typically after a days production) it is discharged throughout the night.

The main cause of the excursion is deemed to be related to the pH. After each production day every product contact line must be cleaned and sanitised. This is first done by caustic in the Clean in place process. The next stage after the chemical mix removes residue left behind by the process is to clean steam sanitise the pipework ensuring all pathogens are killed at a very low level. The pH issues arise from this as all chemical waste must be disposed of and it is very high strength. Initially the discharge tank would just dilute due to the excess water waste from post clean flushes, however since these excursions an automated dilution method is required. The issue we have now is to implement a system that will govern the discharge of waste to drain in regards to temperature and pH value and a suitable control system including automatic valves, PLC control (linked to the site Siemens PCS7 system) and condition monitoring equipment for temperature, level pH etc.

Specification of Problem

As discussed earlier the defined issue is with the Environmental monitoring of the waste water systems to drain. The pH of the waste water can be too far below pH 7 and is drifting out of our agreed limits. The limits are set by local regulations and United Utilities and our limits are as follows

Limit TypeLow LimitHigh Limit

pH6.010.0

Temperaturen/a43.3C

Flow Raten/a12l/s

These are the control limits that the instrumentation I will choose will have to operate within and the control system in place to be robust enough to enable these tolerances to be controlled within and to block any discharge that it outside these limits. Also ensuring maintenance of the equipment in line with our requirements to the Food and Drug Administration (FDA).

The issue in hand has become far more prominent due to the increase in production waste chemicals from the cleaning. Previously the chemical would just mix within the tank and dilute after the flush had completed however this is not currently the case and the pH has been rising and without manual addition of water to dilute there is no control on this par of the process.

Proposal for solution

My proposal for a solution to this issue is to have an automatic dosing of clean water from site to bring down both temperature and pH. The project must conform to these basic standards;

Not allow discharge if process conditions are not met. Dose water to meet process conditions for temperature and pH Circulate/agitate liquid to ensure consistency. Automatically discharge after a hold time at defined process conditions.

For the control system to stop discharge we must have interlock systems in place that will not allow the discharge valve to open until the temperature is < 43 degrees and the pH >6 and