Stainless Steel to reduce corrosion and contamination into the blown film stream.
Longer inlet and outlet reducers to minimize air pressure loss and ensure full coil face area utilization.
What is Plastic Film?
Often when people talk about plastic films—which technically are defined as plastic sold in thicknesses of up to 10 mils – they treat them as one type of material, grouping all flexible plastic packaging into a single category. What they do not realize is that plastic films compose a broad category of materials that can be relatively simple or complex depending on the demands of a particular product or package.
Like plastic bottles and containers, film can be made with different resins, each of which has a unique combination of properties that makes it ideal for certain applications. For example, low density polyethylene ( LDPE ) film acts as a gas barrier, which is necessary for packaging such things as chicken, which would quickly spoil if exposed to oxygen. Polyvinyl chloride( PVC ) film, on the other hand, is gas permeable and necessary for packaging such things as red meat, which require a small amount of oxygen inside the package in order to remain fresh.
Plastic film also can be clear or colored, printed or plain, single- or multilayered and combined with other materials such as aluminum and paper. Thus, the only thing that all plastic film really has in common is that it is flexible in nature, as used in grocery bags.
Blown Film Extrusion
This process is used to produce a wide range of plastic films which include packaging films for food and other products, membranes for land fills, garbage bags, and the backing for various types of adhesive tapes just to name a few.
Blown films can comprise of a simple single layer of material or eight to ten layers of material.
The various layers are used for different properties such as a barrier layers and layers for reclaim plastic or fill.
The films are produced using one or more plastic extruders. Here plastic pellets are fed to the hopper of the extruder, which use a rotary screw in a long steel cylinder (the barrel) to transform the solid pellets to a molten form under high pressure.
The barrel has a number of zones where the temperature is controlled. The molten plastic is forced under high pressure through a die in the shape of a horizontal ring. With conventional air ring systems, the plastic from the ring is drawn upward and expands outward a number of times to produce a film of less than .001” to .1”. As the plastic is pulled vertically (known as the bubble), forced air surrounds the plastic. A high-pressure blower supplies the air ring. The plastic goes from the molten state to a solid material. The point of change is called the frost line.
The rate of production is determined in part by the amount of cooling that the film receives from the air. If outside or ambient air is used for cooling the bubble, the rate of production will increase as the air temperature drops from summer to winter. This variation in temperature forces the operator to increase or decrease the extruder throughput to ensure proper cooling time on the bubble.
The BERGBlown Film Cooler System can simulate winter conditions all year round supplying a constant air temperature to the bubble. This system consists of a Blown Film Cooler and a Package Chiller. With this system, the air from the blower passes through the Blown Film Cooler (BFC).
The BFC removes the ambient heat in the air and heat generated by the blower to deliver air as low as 40 °F. A chilled coolant supplied by the chiller is circulated through the coil in the BFC to remove the heat in the air.
The BERGBlown Film Cooler includes an extra deep heat exchange coil designed for low air velocity through the coil. The design of the coil is such that the leaving air temperature from the coil is within 5 F° (know as the approach temperature) of the entering coolant temperature compared to blown film units supplied by other companies where the approach temperature is 10F°.
This means that for the same leaving air temperature the coolant from the chiller can be warmer by 5 F°. This translates to being able to use a chiller that can be 10% smaller and therefore uses less energy.
In order to maintain close control of the leaving air temperature Berg recommends an automatic three-way valve. In this way the leaving air temperature can be controlled to +/- 1 C°. At the same time the chilled water flow remains constant regardless of the required leaving air temperature.
The use of a BERGBlown Film Cooler System not only increases the rate of production but also reduces plant labour costs and promotes an increase in the film clarity and consistency.
- Heavy gauge stainless steel
- Insulated with 1/2″ armaflex
- Both left hand and right hand configurations
- Automatic temperature control valve
- Industrial dial type
- Air temperature in and out
- Water temperature in and out
Glycol / Water Connections
- bronze gate valve on inlet (shut-off only)
- bronze ball valve on outlet (flow control)
- 3 way automatic valve with electronic controls
- fan assembly
- variable speed drives
- mixing boxes
- Air Flow (SCFM) 500 – 4000
- Capacity (BTU/hr) 69K – 550K
Berg Total Chilling Solutions Brochure
Berg Chilling Solutions Capabilities Overview
Plastics Industry Pocket Brochure