Case study: processing plants and improvement

Assumed case study: a milk pasteurisation and packaging section of a dairy plant (HTST process: raw milk tank, heat exchanger, steam-heated holding tube, cooling, filling). The existing system uses analog panel indicators, bimetal thermostats, a manual steam valve and operator logging. (If your own visit was to another plant, replace the process names; the structure of the answer stays the same.)

Processing plants studied (in the milk plant)

1. Reception and chilling section: milk is received in cans/tankers, weighed, tested (fat, SNF, acidity), filtered and chilled to below 5 C in a chiller.
2. Pasteurisation plant: HTST heat exchanger heats milk to 72 C for 15 s, then cools it to about 4 C. Steam from a boiler is used.
3. Homogenisation and storage: homogeniser and insulated storage tanks.
4. Packaging (filling) plant: pouch filling machine, date coding and crates.
5. Utilities: boiler, ice-bank/refrigeration, compressed air, effluent treatment.

Further improvement with block diagram

Automate the plant using distributed microcontroller/PLC nodes connected to a central supervisory computer:

 Reception node --+
 Pasteuriser node-+--RS-485/Modbus--> Master PC (SCADA)
 Storage node ----+                    trend, alarm, report
 Filling node ----+
   each node: sensor -> ADC -> MCU -> relay/valve

• Pasteuriser: PT100, PID steam control, flow-diversion valve, data logger.
• Chilling and storage: temperature and level sensors with alarms and automatic agitator/pump control.
• Filling: weight/volume dosing with count and batch totals.
• Central SCADA: set-points, alarms, daily reports and energy monitoring; later link to ERP.
• Benefits: constant quality, lower losses, less manpower, traceability and predictive maintenance.