Dairy Equipment, Utilities and Plant Maintenance
Domain 7 covers dairy equipment, utilities and maintenance. Expect questions on pumps, heat exchangers, homogenisers, refrigeration, steam and preventive maintenance.
Core rules
- Centrifugal pumps suit low-viscosity milk; positive-displacement pumps suit viscous products.
- Plate heat exchangers transfer heat with regeneration; homogenisers force milk through a valve at high pressure to reduce fat globule size.
- Refrigeration COP = refrigeration effect ÷ work input; boiler steam is used for heating and CIP.
- Preventive maintenance includes calibration, lubrication, gasket inspection, spare-parts planning and safe lockout. CIP flow velocity and temperature matter; dead legs create cleaning shadows.
Worked example
A chiller removes 20 kW of heat and the compressor draws 6 kW. COP = 20 / 6 = 3.33. The reasoning is that COP is useful cooling divided by work input; a higher COP means more cooling per unit of electricity.
Traps
- Cavitation from a blocked suction line damages pumps.
- Running a pump dry overheats seals.
- Ignoring steam traps wastes energy and causes water hammer.
- A homogeniser operated at the wrong pressure gives poor emulsion stability.