Bottle Washer

Bottle Washer

A bottle washer is an industrial machine designed for cleaning returnable glass bottles in bottling operations. These machines handle containers from mineral water, wine, spirits, soft drinks, fruit juices, and milk production lines, removing labels, residues, and contaminants while ensuring proper sterilization.

Modern bottle washers can process both paper labels and wash-off plastic labels. Plastic labels offer significant advantages including lower washing temperatures, reduced chemical usage, and elimination of label pulping in the water, though at a higher label cost.

Types of Bottle Washing Machines

Single-End Bottle Washers

Single-end bottle washers (also called single-head) feature bottle entry and exit on the same side of the machine. Key characteristics include:

• Production capacity up to 30,000 bottles per hour
• Single large alkaline wash bath followed by rinse stages
• Compact footprint for small to medium operations
• Lower capital investment compared to double-end systems

Double-End Bottle Washers

Double-end bottle washers (or double-head) are structured with bottle entry at one end and exit from the opposite side. These machines offer superior performance:

• Production capacity exceeding 100,000 bottles per hour
• Modular construction with 3 to 5 identical washing modules
• Higher washing performance and quality guarantees
• Multiple alkaline baths for thorough cleaning

Temperature Management

All bottle washers maintain a precise temperature gradient to prevent thermal shock and glass breakage. The process brings containers from ambient temperature (potentially very cold in winter storage conditions) up to approximately 80°C in the caustic baths, then gradually returns them to room temperature before discharge.

An alkalinity gradient runs parallel to the temperature curve, designed to recover caustic soda that would otherwise be lost through carryover. Water from the first rinse returns to the pre-wash tank for reuse, providing both heat recovery and chemical efficiency.

Washing Process Stages

Bottle Inlet System

The most common feeding system uses harpoon loaders with elliptical movement, automatically transferring bottles from the accumulation area to washing baskets. Features include:

• High-density plastic profiles ensuring quiet operation
• Safety mechanisms preventing bottle and basket breakage
• Special auger feeding systems for shaped bottles (rectangular, square, oval)
• Interchangeable baskets accommodating multiple bottle formats

Pre-Wash Section

Upon entering the machine, bottles receive alkaline spray or immersion using warm water from the first rinse. This stage accomplishes two objectives:

• Gradual temperature increase of the glass
• Initial label wetting with alkaline solution

The pre-wash solution contains hardness control additives preventing salt precipitation.

Caustic Washing Baths (Pulp)

The caustic baths perform the primary cleaning function, eliminating internal impurities, detaching labels, removing glue residues, and sterilizing bottles through hot soda exposure. The washing result depends critically on these pulp stages.

Optimal label removal depends on several factors:

• Glue type — modern starch-casein glues dissolve effectively in soda solutions starting from 1% concentration
• Soda concentration — effective range between 1.5% and 3%; above 2% viscosity increases, reducing efficiency
• Temperature — below 60°C labels won't release; optimal removal occurs at 80°C
• Label structure — paper quality, ink composition, and waxy coatings affect detachment

Label Extraction

All bottle washers feature a two-stage label extraction system:

1. First stage — activated after approximately 40% of caustic treatment time, a solution current removes about 30% of labels
2. Second stage — positioned at the end of caustic treatment, high-pressure sprays from removable nozzles remove the remaining 70% of labels

Extracted labels travel to a filtering mat crossing the machine transversely, conveying paper residues outside.

Extraction timing is critical:

• Too fast extraction — causes label pulping, clogging filters and leaving fragments in bottles
• Too slow extraction — results in labels exiting beyond the second module with glue traces remaining on glass

Pre-Rinse Section

Modern bottle washers include a dedicated sector for alkalinity reduction and heat recovery. This section improves rinsing efficiency and controls limestone precipitation from inorganic salts.

Treatment depends on the circuit configuration:

• Static tank (filled morning, emptied evening) — treated as a washing bath with soda additive
• Continuous fresh water replenishment — treated as a rinse with sequestering agent dosed proportionally

Rinsing Section

The rinsing section typically comprises 3 to 4 stages, eliminating soda residues and ensuring bottles exit in potable condition. The final rinse uses the same water destined for bottling.

Critical considerations:

• Water hardness — causes calcium carbonate precipitation; requires sequestering additives if water is not softened
• Microbial control — rinse area favors bacterial growth due to warm temperature and neutral pH
• Biocide treatment — added to second or penultimate rinse to sanitize bottles and maintain bacteriostatic conditions

Nozzle System

Self-cleaning nozzles direct spray radially toward each basket row. The self-cleaning effect eliminates manual disassembly through water flow inversion and continuous particle removal. Spray direction ensures complete coverage:

1. Internal bottle side
2. Bottle bottom
3. Opposite internal side

A synchronization star beside each nozzle row maintains perfect alignment between sprays and bottles, compensating for chain elongation.

Bottle Discharge

The unloading system transfers bottles from baskets to discharge cams with elliptical movement, placing them onto the conveyor belt. Chutes and cams use high-density polyethylene for quiet operation and durability.

The discharge area requires special attention due to humidity, steam, warm environment, and neutral pH creating favorable conditions for microbial development. Daily cleaning and sanitizing treatments of internal and external surfaces prevent contamination of clean bottles.

Optional Systems and Features

Soundproofing

Loading and unloading areas can be equipped with noise reduction devices improving operator safety conditions.

Thermal Insulation

Operating temperatures between 60°C and 80°C make insulation valuable. Polyurethane panel systems with stainless steel edge support can achieve energy savings approaching 20% of total consumption.

Wastewater Filtration

Two systems extend pulp bath life cycle:

• Sedimentation tank — end-of-day solution transfer for medium-low or high-pressure filtration
• Vibrating screen — continuous filtration during operation, retaining glass and paper particles

Acid Washing Sector

Some machines include an acid spray section between caustic wash and final rinse, using nitric acid formulations to eliminate inorganic residues and provide steel surface passivation. Periodic antimicrobial control prevents mold formation in acidic pH environments.

Chemical Products for Bottle Washing

Standard chemical formulations used in bottle washers include:

• Caustic soda additives — facilitate label detachment
• Foam control additives — manage foam from casein-origin glues
• Alkaline formulations — alternative to NaOH + additive systems
• Sequestering additives — control water hardness in rinse baths
• Sanitizing formulations — treat bottles at outlet and maintain bacteriostatic tank conditions

Additional performance-enhancing formulations:

• Enhanced label detachment additives
• Additives for mold and dried residue removal
• Acid additives to reduce first rinse alkalinity

Sequestering Agents

Sequestering (chelating) agents bind dispersed ions and salts, preventing limescale deposition on surfaces. These compounds assist in mold removal and aluminum salt control for improved label detachment.

EDTA forms stable chelates with calcium and magnesium, preventing limestone formation. However, EDTA requires careful dosage calculation and can increase glass corrosion over multiple washing cycles.

Gluconates and gluconic acid offer polyfunctional activity in the 1% to 3% alkalinity range, specifically targeting aluminum and its salts (trivalent metals EDTA cannot bind). Gluconates also assist in rust collar removal caused by crown caps.

Defoamers

Defoamer products control foam generated by mechanical action and starch-casein glue. Foam management prevents pump cavitation, probe interference, and ensures detached labels are properly extracted rather than floating to final machine sections.

Sterilization Parameters

Correct bottle washer operation depends on optimizing three intersected parameters:

• Caustic soda concentration (alkalinity) in washing baths
• Operating temperatures of washing solutions (70°C to 90°C)
• Contact time between caustic solutions and bottles (basket movement speed)

These parameters ensure both excellent washing results and microbial reduction inside bottles, while achieving proper label separation without pulping.

Quality Control: Visual Bottle Evaluation

Bottle appearance at machine exit indicates washing quality and identifies the source of any defects:

Properly washed bottles display a homogeneous water film covering the entire external glass surface. When inverted, only 2-3 drops should exit, indicating correct dripping and proper spray nozzle orientation. After drying, glass should remain bright without streaks, verified by phenolphthalein or litmus paper testing (pink color indicates residual alkalinity).