DAIRY ENGINEERING

Module 2. Bottle & cans washing and CIP cleaning equipment

Lesson 6
BOTTLE WASHERS, FACTORS AFFECTING WASHING OPERATIONS, POWER REQUIREMENTS OF CAN AND BOTTLE WASHERS

6.1 Introduction

In olden days the retail milk supply was mostly done by glass bottles, which were reuse type and needed washing operations, before refilled and distributed for milk supply. As the bottles were mostly ½ litre capacity, the numbers of bottles were huge, for supply to even a medium size city. Hence, mechanized bottle washing was necessary not only to clean the bottles in large numbers, but also to do so safely, without harm to the personnel. Bottle washers of various types and sizes were in use, and the appropriate one was chosen to match the requirement of the dairy. Most popular among these bottle washers was the soaker type where bottles are soaked and jetted by an apron carrying bottles in various sections. Among the soaker type, there are again two types, one in which the feeding of bottles and the exit of cleaned bottles are at the same end of the bottle washer, and second in which, they are in the opposite ends. The sequence of operations of a typical soaker type bottle washer is given below.

6.2 Soaker Type Bottle Washers

In this type of bottle washer, the bottles are loaded in to a continuous conveyor chain that will be having rows of bottle holders. The conveyor chain passes through various stages of cleaning and sterilizing like: 1) Pre-soaking 2) Jetting 3) Detergent soaking 4) Flushing 5) Rinse water jetting 6) Hot water jetting 7) Warm water jetting 8) Cold water jetting. The bottle washers may be of loading and unloading on same end, or it may be on opposite ends. The figure shows the bottle washer of soaker type with loading and unloading on same side (Make: Stork, Holland).

All the changes in direction of the conveyor chain are guided by chain wheels, which are provided with bearing boxes of plastic material. The shafts are made of stainless steel and all bearings in the machine are self lubricating. The temperature of sections where heating is required is supplied with heating coils having steam flowing in it, with condensate drain through steam traps.

The sections are so arranged that there is a time – temperature treatment by each section. The temperature variations never exceed 25ºC inspite of high cleaning temperatures used in the process. This will avoid any thermal shocks to the bottles, there by reducing breakages. There are no acids involved. The total time taken for the bottle to get cleaned and return after passing through all sections is about 15 to 20 minutes depending on speed of the conveyor chain movement.

6.3 Description of Operation

The bottles are loaded on the loading table, which is a flat chain made of stainless steel. The bottles are loaded by distribution mechanism which guides the bottles in to individual bottle holders of each row. Each row may be having 8, 12 or 16 receptacles, depending on the Bottle washer capacity. The Tipping cradle ensures that the bottles are loaded in inverted position in the receptacles. The Tipping mechanism is also provided with safety switch, which will stop the movement of chain, if any of the bottles gets stuck between the tipping cradle and the conveyor chain. This avoids breakage of bottles when the conveyor moves to receive next set of bottles.

The conveyor chain takes the bottles first in to Pre-soaking section, where the water at 35ºC, wets the bottle and its inner surface and loosens any leftovers sticking to it. Next it moves to jetting section, where hot water is jetted at 55ºC into bottles to dislodge any particles still sticking to its surface. The chain then moves into Detergent soaking section, where hot detergent at 75ºC will dissolve the fat and any greasy substances on the surface of bottle. The bottles are then flushed out of detergent solution, and move to jetting sections, where the detergent solution is jetted into bottles with force. The bottles then move over water jetting sections, designed to progressively remove the detergent remnants and reduce the temperature of bottle. These involve rinse water jet (65ºC), hot water jet, warm water jets (35ºC) and then cold water jet (15ºC).

The bottle is then discharged in vertical position by flat stainless steel belt conveyor to bottle filling section, with a hood on the conveyor to avoid any direct exposure to outside contamination. The conveyor is positioned with an observation point where magnifying glass is provided for visual inspection and eliminating any bottles with minor cracks, chipping at mouths or bottom to avoid damage and breakage during filling operation and further crating, storage and loading operations.

6.4 Maintenance

The maintenance of bottle washer is essential, day to day as well as periodical inspection, repair and replacements. The clogging of jets is a frequent problem and this has to be inspected daily, through leak proof inspection doors provided at the sides of the enclosure. Safe lighting is provided inside the bottle washer for this purpose. The steam pressure, water jet pressures are to be maintained. If the motors or pipelines are forming scale, it has to be removed. Spillage of water jets outside the bottles to which they are directed to must be avoided, due to lack of sufficient pressure or excess pressure. The chain conveyor movement should be ensured for smooth movement, without any excess of friction at various wheels provided for change of direction. Steam condensate traps must be inspected for proper operation and draining of condensate. The strainers provided before jetting rows are to be cleaned time to time.

Fig. 6.1 Bottle washer

(Adopted from Bottle washer manual of Stork company, Holland)