Storage

Introduction

Modern milk plants hold both raw and pasteurized milks for a much longer period than before. Normally the milk storage capacity is equal to one day’s intake. This allows a more nearly uniform work-day for processing and bottling operations with less dependence on the time for receiving raw milk. Storage tanks are used in Milk Plants for the storage of raw, pasteurized, or processed products, often in very large volumes. Because of the longer periods of holding, storage tanks are among the most important items of equipment. They must be designed for ease in sanitation, preferably by the circulation-cleaning method. In addition, the tanks should be insulated or refrigerated, so that they can maintain the required temperature throughout the holding period. Agitation should be adequate for homogeneous mixing, but gentle enough to prevent churning and incorporation of air.

Objectives

1. To maintain milk at a low temperature so as to prevent any deterioration in quality prior to processing/product manufacture;
2. to facilitate bulking of the raw milk supply, which will ensure uniform composition;
3. to allow for uninterrupted operation during processing and bottling;
4. to facilitate standardization of the milk.

Types of Storage

1. Insulated or Refrigerated

In the former, there are 5 to 7.5 cm. of insulating material between the inner and outer linings; in the latter, the space between the two linings is used for circulation of the cooling medium. Another variation of the refrigerated type is the cold-wall tank.

2. Horizontal or Vertical

While the former requires more floor space and less headspace, the latter requires less floor space and more headspace. Modern circulation cleaning methods have made very large vertical storage tanks practical.

3. Rectangular, Cylindrical or Oval

Of these, the first suffers from the disadvantage of having dead corners during agitation, while the other two do not.

4. Built for gravity flow, air-pressure or vacuum operation

The first is the most common. However, air pressure is sometimes used to evacuate the product. This requires special construction of the storage tank for greater strength than necessary for normally operations under gravity flow.

5. Location

In one system, the storage tanks are located on an upper floor. The milk is pumped from the receiving room to the floor above. It then flows by gravity to the pre-heater, filter or clarifier, pasteurizer, cooler and bottling machine. In another system, the milk is pumped from the storage tanks through a pre heater and filter into the pasteurizer. Hence it may flow by gravity to the cooler, or it may be pumped to the cooler while hot.

6. Parts of a Storage Tank

1. Sight glass;
2. light glass and lamp;
3. ladder;
4. manhole;
5. agitator;
6. outlet valve;
7. inlet;
8. air vent;
9. safety valve;
10. legs;
11. indicating thermometer;
12. volume-meter.

Ag.
Technologies
(Dairy)