PASTEURIZATION

PASTEURIZATION

The heating of every particle of milk or milk product to a specific temperature for a specified period of time without allowing recontamination of that milk or milk product during the heat treatment process.

Pasteurized plant is intended for the production of pasteurized milk.Raw milk stored in silos is passed through pasteurizer .There it is heated to 72 degree Celsius for 15sec .The time 15sec is adjusted by making the tube longer.Most of the pathogenic organisms are eliminated during this time.The next step is to cool this milk suddenly to about 4 degree.Milk having 60 degree Celsius goes to homogeniser and 40 goes to cream seperator.Due to the high pressure applied the milk goes through very narrow nozzle and the fat globules are broken down into smaller particles and equally mixes with the milk,resulting in the production of homogenised milk.The basic principal of cream separator is centrifugal action by which the low density fat is accumulated at the top and the high density milk is obtained as skimmed milk.

BASIC DESIGN OF A PASTEURIZER

It mainly consist of a Product supply,Product Balance Tank, Product Pump, Flow controller, Regenerative section, Bypass for equipment like filters, separators, homogenizers.

Product Balance tank

It consist of a float as a Level controller

· To keep the count level above the product pump inlet

· To damp fluctuations in the flow after the pump

· To get rid of incoming air bubbles in the incoming product

· Flow controller maintains constant flow through the plate heat exchanger.

Adjustable flow Controller

Is designed to control and maintaina constant flow rate.It is equipped with an adjustable setting cone to control any flow within its capacity range.Main parts of this flow controller are

· Nut/clamp

· Outlet pipe

· Setting cone

Actuator

The Pneumatic actuator is designed so that an axial movement of a piston is transformed into 90 degree rotation of the shaft.The torque of the actuator increases at the end of the movement to improve the closing security.

Milk strainer

Particles in the milk flowing through the strainer are caught by the perforated strainer bag or by the filter.The filter consist of two halve body and cover with filter bag or PVC and hold together by clamp.The filter bag is of size 120 mesh.

The milk or bottom outlet .Product enters the ECD filter from the top jet, filtered through the mesh and comes out from the bottom outlet.The temperature sensor PT-100 is a resistant temperature detector RTD.The temperature of the platinum changes as the temperature changes.

ElectroPneumatic positioner

The Electro Pneumatic positioner produces the preselected relationship between valve stem position(controlled variable) and controller output signal(signal output).The Positioner consist of an electropneumatic converter unit and the Pneumatic part with lever shaft measuring spring, the control system with nozzle,flapper and amplifier.The dc control signal is supplied by the controller fed to the coil in the field of permanent magnet.At the beam the force of the coil which is proportional to the current is balanced to the force of the air pressure produced at the flapper.The air pressure supplied to the control system varies proportionally with the current signal.The air pressure inturn produces a positionary force at the measuring diadhragm which is compared to the force of the measuring spring.The motion of the measuring diaphragm is transmitted to the flapper by a pin and the nozzle is activated.Changes in the control signal or in the valve stem position produce a pressure change in the amplifier downstream of the nozzle and the signal pressure supplied by the amplifier causes the plug stem to assume a position corresponding to the input signal.

Regulatory valve

The valve is operated by means of a handwheel which makes it possible to open it gradually.The plug can be fixed in adjusted position with lockscrew.