Selection of Milk Handling and Processing Equipment

It is very important to select the best equipment at a reasonable cost. To do we must know the capacity of dairy plant, each process involved and purpose of this individual equipment. We should also know the period of operation or running of the equipment. The location of plant also affects the selection. In order to determine the capacity, one must know the products to be manufactured and their process of manufacture. We can then develop a product flow line diagram of each product.

This will enable us to know how the milk will be handled at various stages of processing, thus, the capacity of each equipment involved can be determined. An example is given here.

i. A Simple Example

Suppose a dairy unit is to receive 10,000 litres of milk per day, 60% of milk in the morning and 40% in the evening. Normally evening milk is chilled and stored for processing in the morning. Also it is assumed that milk will be received through milk cans, and only butter and standard pasteurized milk will be manufactured. Let us make a product flow line diagram (Figure-1.1) and decide capacities of individual equipment.

Milk Reception: Milk must be received inside the dairy within 3-hours of its arrival at the receiving point, accordingly milk reception rate is decided to be 2000 L/h. Normally 2-3 cans in a minute are to be received by an operator. Hence, a weighing machine of 250 kg is selected. Every two to three minutes the milk will be released into dump tank. In about 20-30 minutes one dump tank will get filled.

Hence, the capacity of 1000 litres is enough. There may or may not be need for the second dump tank, indicated as dotted lines and shown as optional arrangement.Milk Handling: Milk from dump tank must be removed quickly to enable the receiving of fresh raw milk. To do so a high capacity milk pump is needed to unload. Therefore, a 5000 litre/hour capacity is good enough. The empty cans are sent for cleaning through a rotary can washer. The capacity of can washer will be same as that of can reception rate. Milk while pumping is required to be chilled on line. Therefore, a plate chiller of 5,000 L/h is selected. The chilled raw milk will be stored in raw milk storage tank (usually insulated). Only one tank of 5,000 litres is selected.

Milk Processing: As soon as milk reaches raw milk storage tank, the pasteurization through a HTST (High Temperature Short Time, will be explained in Unit-2) is also followed. At this point milk passes through a centrifuge machine to remove excess of milk fat as indicated in the diagram. The standardized and pasteurized milk is stored for subsequent filling through a pouch-filling machine, while the cream is stored in a vat (Ripening Vat cum Batch Pasteurizer). This vat will have about 500kg of Cream; hence, a cream pasteurizer of same size is selected. Cream after ripening is transferred into butter churn for making Table Butter and the butter is  stored in the cold store. Similarly, standard pasteurized milk filled in pouches is stored in crates and are stacked in a separate cold store.

Sizing of Equipment: The size of individual processing equipment is easily determined. The actual capacity will finally be decided looking at the availability of equipment in the market. For example milk-weighing machines are of 250 and 500kg capacity. Selection is to be made accordingly. Dump tank is normally of 1000 and 2000 litres capacity. Likewise all the equipment indicated in the diagram are selected, based on the product flow line diagram and the availability of equipment with the manufacturer i.e. in the market.

ii. Some General Aspects of Equipment Selection

The surface finish of equipment should be No 4. And the thickness of metal used is such that no dents or cracks are formed while working with it. All equipment should have self-draining slopes. The dismantling and assembling type joint and fittings are preferred. No threaded constructions are permitted. All connections made on the equipment are such that no projections are towards product side. All equipment should be at least 10 cms. above the floor level to permit cleaning of floors.

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