COMPRESSED AIR TECHNOLOGY FOR PET BOTTLING SYSTEM

AIRMAX SYSTEM - SOLUTION FOR TOTAL RELIABILITY

AND EFFICIENCY

COMPRESSED AIR TECHNOLOGY FOR PET BOTTLING SYSTEM

Table of Contents 1. Preface 2. Background Information on PET Bottling Technology 3. Compressed Air Requirement for PET Bottling Plants 4. Design Considerations for Compressed Air Station For PET Plant 5. Schematic Diagram of a Typical Compressor Station for PET Plant

equipped with low pressure air dryer 6. High pressure booster and dryer

7. Ready Solutions for Quick Reference

1. PREFACE Compressed air is energy that is being used more and more in various fields of industry. This is due to the higher operational safety, flexibility and ease of operation when using compressed air as opposed to other forms of energy.

The need for compressed air is no exception in the plastic industry, especially in the PET bottling plants. The need for compressed air is in fact unique in the PET industry, so design high efficiency compressed air system to get high quality air is essentially.

PET bottling machines need high-pressure air for the blow molding process. The machines also need high-pressure air for the pneumatic cylinders to actuate the various parts of the machines. With such a diverse requirement, together with other compressed air needs within the plant, it makes the selection of a complete, reliable and energy efficient compressed air system for such users a challenging and unique one. With a glut in PET resin, the resin is getting cheaper and it makes economical sense for more packaging producers to switch to PET bottles as opposed to other forms of packaging. With such a trend in the plastic industry, it is thus important for us to have a good understanding of the industry and prepare ourselves to better serve such users.

2. BACKGROUND INFORMATION ON PET Polyethylene Terephthalat, or more commonly known as PET, is growing in popularity as a resin and its use in the fabrication of packaging containers. Application One big advantage of PET is its recyclable ability. The use of PET increases the strength, allowing light-weighting of the containers and thus provide bottle production of high economy in comparison to other materials.

PET containers feature an array of outstanding properties such as : • Excellent sparkle and transparency • High breakage resistance to avoid risk and injury • Good barrier characteristics against carbon dioxide and oxygen • Dimensionally stable, suitable for all designs • High resistance to internal pressure whilst maintaining stable long-term thermal

performance • Thermally stable, thus suitable for hot filling • High degree of purity, thus suitable for recycling • High chemical compatibility and freedom from taste and odour • Approved as suitable for food contact applications An effective barrier against carbon dioxide is of great importance when bottling carbonated drinks which explains its wide usage and popularity with the soft

drinks bottlers. Similarly, low weight, high strength and pressure resistance are also major importance for such an application. A good oxygen barrier and freedom from taste and odour make PET containers suitable for mineral water, edible oils, vinegar and sauces.

When it comes to avoiding injury, break resistance is important for the food and non-food applications such as cleaning agents and other chemical. Freedom of design is a significant advantage for the many varied PET containers currently in use, which can also be used as wide-necked containers for foods. The technology is available to produce not only round containers but really containers of many varied designs and shapes.

Containers for Hot-fill requirements A few years ago, PET bottles were suitable only for cold filling. At filling temperatures above 60 °C, they would lose shape and shrink uncontrollably. However, recently introduced material treatment methods now allow PET bottling of a wide range of other products for which hot or warm filling is a must. Examples of such hot-filling requirements are fruit juices and preserved foods. This explains the trend of fruit juice producers moving away from the conventional tetrapaks and tin cans, which often account for 75% of the

product cost. PET containers only account for 30% of the product cost, on top of the lists of benefits discussed earlier. Different fills require different temperatures. The general market guideline is : Thermally stable up to 87 °C Partially crystalline up to 92 °C Fully crystalline up to 95 °C

Refillable Bottles The market for reusable PET bottles is growing both in highly environmentally conscious countries and in countries where funds for packaging outlay are limited. The PET bottle stands up to any comparison against glass bottles and has the advantage of being light weight, breakproof, large-volume and recyable with low energy requirements for production and washing.

PET STRETCH BLOW MOULDING MACHINES Typically, PET machines are called Biaxial Stretch Blow Molding Machines. By biaxial, we mean that the so called preforms are being stretched longitudinally as well as latitudinal.

It is this biaxial orientation and capability which give PET the strength over other materials. The selection criteria for such machines are normally based on its production capacity, efficiency and the ability to handle hot-fills. However, one of the major concern is the ability of the machines to blow a wide variety of container in a

range of different mold cavities, using modular mould change.

PET machines are typically set in an in-line orientation. This is provided for easy access for scheduled maintenance, mould changeovers, and bottle processing. The process control allows the operator to monitor each module’s production status thereby increasing the machine’s overall efficiency. The modular arrangement also offer the blow-molder the option to purchase only the required modules to meet the specific business at the point of time and growing with the business, thus keeping the initial investments to a minimum.

Basic Concept PET machines typically comprise the following five modules : Preform Feeder Preform Insert and Bottle Discharge Heating Unit Heating and Preform Transportation Blow Moulding

The complete 2-stage injection and stretch-blow molding process is shown in the process diagram on the next page.

3. COMPRESSED AIR REQUIREMENT

FOR PET BOTTLING PLANTS In PET applications, there are two types of compressed air requirements. These are • control air and • blowing air. The amount of control and blowing air are very well specified by the machine suppliers. However, it is essential to remember that PET machines are highly versatile and can blow a wide range of PET containers with a simple mould change. Thus, it is important to note and specify the maximum amount of high pressure used as the big fluctuation impact not only the selection of the booster compressor but also the basic low pressure compressor as well.

• Control air is used to operate pneumatic cylinders and are normally between 7

to 10 barg, depending on the make of the PET machines. • Blowing air is used for the stretch blow-molding of the heated preforms,

according to the mould. The amount of air required varies according to the capacity of the bottles/containers. The pressure of the blowing air typically vary from as low as 15 barg to as high as 40 barg, depending on the physical characteristics of the bottles/containers to be achieved. Higher pressure is used for harder and thicker containers while lower pressure is used for softer and thinner bottles/containers.

• It is this combination of control and blowing air, of differing pressure, which present us with the opportunity of using unique Hertz Kompressoren PET solution for such application.

The Hertz Kompressoren PET solution is a comprehensive, total solution, which offers thorough efficiency in initial investments and operational costs. Above all,

the total solution is uniquely designed for total reliability and maximizing productivity for the customers. 4. DESIGN CONSIDERATIONS FOR COMPRESSED AIR

STATION FOR PET BOTTLING PLANTS When designing a compressed air station for a PET plant, some salient points must be thoroughly clear: • The most important consideration is the range of bottles being produced. The

company may start on some lower pressure application and then move on to do even higher application or vice-versa. This “problem” is compounded when the plant move also from making smaller bottles/containers to larger bottles or containers. Although such migration and diversification are limited to the maximum capacity of the machine, the plant must be able to handle such migration and diversification all the same. Once these information are available, the maximum amount and the maximum pressure of the high pressure air must be determined.

• The next important item to determine is the amount and minimum pressure of

the low pressure working air. This would help determine the theoretical inlet pressure at which the booster should operate on and the theoretical inlet volume at that pressure. With these information, the total amount of low pressure working air can be determined and the configuration of the booster can be arrived at.

But please note, booster FAD will increase, when pressure on suction side of booster is as high as possible. As control air requirement is not very high, it may be advisable to choose a higher pressure on the low pressure side. • When selecting the booster compressor, it is important that redundancy is

provided for. If this is not possible, because of budget or space constraint, then the booster must be sized to operate at a maximum of 60% to 70% duty cycle only.

• When selecting the low pressure screw compressors, consideration must be

given to the spare capacity available from existing compressors if the working pressure is above the required inlet pressure for the booster selected. Spare capacity can be utilized to make up the required amount of low pressure inlet air for the booster. The make and models of the existing compressors should also be noted and taken into consideration when planning the overall control for the plant.

• In choosing between possible solutions, consideration must be given towards

achieving the lowest possible initial outlay and long term operating cost. Working pressure of screw compressors should be at least 7 bar(g).

HOW TO CALCULATE COMPRESSED AIR REQUIREMENT FOR PET BOTTLING PLANTS In case the PET-machine supplier does not specify the air requirement for blow molding, this value may also be calculated using following formula:

FAD-B = B * V * P * 1,35 / 60 min FAD-B Free Air Delivery of booster compressor in [m³/h] B Number of bottles to be produced in [bottles / hour] V Volume of bottles in [Liter] P Absolute working pressure in [bar(a)] Please note: Factor 1,35 is used to include also the volume of bottle neck,

blow-molding tool and supply lines up to feeder-solenoid valve. The result of this calculation is the minimum FAD of a booster to be installed in this new PET - plant. Now, knowing the minimum pressure of working air, one can select the suitable booster compressor. But note, it is strongly recommended to have the working pressure of screw compressors as high as possible:

DISP-B = FAD-B / (Pmin * X) DISP-B Displacement of booster compressor in [m³/min] FAD-B Free air delivery of booster compressor in [m³/min] Pmin Minimum suction pressure of booster compressor in [bar(a)] X Delivery factor, depending on suction and max. pressure (see diagram on next page) Using this value for booster displacement we can select a booster with a higher displacement from booster - brochure.

0,73

0,74

0,75

0,76

0,77

0,78

0,79

0,80

0,81

0,82

0,83

7,0 7,5 8,0 8,5 9,0 9,5 10,0 10,5 11,0 11,5 12,0 12,5 13,0 13,5

Suction pressure bar(g)

Xf inal pressure 35 bar

f inal pressure 40 bar

• When having selected the booster compressor, the next step is selection of

screw compressor for generation of low pressure compressed air.

FAD-S = W + FAD-B * 1,05 FAD-S Free Air Delivery of screw compressor [m³/min] W Required low pressure working air [m³/min] FAD-B Free Air Delivery of booster compressor [m³/min] • Next step is determination of required air treatment components such as air

dryers and filters. A general rule says, installation of a refrigerated dryer and micro –filter combination will meet customers requirements:

There are several possibilities of installing an air-dryer: + either a refrigerated type air dryer for the total FAD of low pressure compressor: this will give you a PDP of approx. 3°C for working air and approx. > 20°C for blowing air. This solution is suitable in tropical climates and for installations, where

pipe routing is inside of buildings, which always have temperatures >20°C. There are some exceptions from this basic layout: when blow-moulds are constantly cooled by means of chilled water. Then you have to install a high pressure air dryer in any case to avoid condensation in bottles.

+ or separate air dryers for low pressure working air - this will increase

investment cost considerably, but also the air quality will improve. A PDP of approx. 3°C for working air and blowing air ensures best air quality.

5. Typical flow Diagram of Compressor Station for

PET Plant equipped with Air treatment

Booster compressors and air dryer

hertz high pressure booster 10 to 75hp / pressure 15 – 40 bar

hertz high pressure air treatment provide oil-free compressed air

7. SOLUTIONS FOR QUICK REFERENCE Following charts and data tables shall help to choose the correct compressed air package for PET-Application in a very quick way. Compressed air packages with air treatment All these tables are based on following main design data: Compressed air for blowing of PET-bottles will be available with a minimum

pressure of 15 bar(g) and maximum pressure of 40 bar(g). Control air for pneumatic systems will be available with a minimum pressure

of 7 – 10 bar(g).l Ambient temperature in compressor room +3 - +40 °C Design temperature for air dryers:

+ ambient temperature +3 - +30 °C + compressed air inlet temperature +40 °C

Cooling of equipment

+ Screw compressors air cooled or water cooled + Booster compressors air cooled

Power supply 220, 380, 440V / 50, 60Hz

+ Voltage fluctuations +/- 5 % + Protection system Zero-wire

Plant design according CE – regulations Pressure vessels will be designed, manufactured and tested according CE-

rules, German TÜV Compressed air quality on the outlet of

High pressure micro filter combination for blowing air + Rest oil content max 0,003 ppm (Class 1 according ISO 8573.1) + Particle size 0,01 µm (Class 1 according ISO 8573.1) + Pressure dew point ≈ +3 - +5°C (Class 4 according ISO 8573.1)

Compressed air quality on the outlet of

Low pressure micro filter control air

+ Rest oil content max 0,1 ppm (Class 1 according ISO 8573.1) + Particle size 0,1 µm (Class 1 according ISO 8573.1) + Pressure dew point ≈ +3 - +5°C (Class 4 according ISO 8573.1)

Exclusions from scope of supply: Mounting of equipment on site, piping and cabling of loose supplied parts, Start up at site, condensate treatment, cooling system

Screw compressors will be equipped with on/off inlet control Booster compressors will be operated with idling mode Booster compressors will be operated alternatively by means of sequencer

control included in the main control cubicle. Sequencing will take place every 20 - 30 minutes.

For protection of booster compressors a filter separator is installed in the

suction line of booster compressors. This Filter-Separator will prevent boosters from water- oil droplets as well as solid particles > 0.1µm.