Plastic pipes are experiencing steady growth worldwide. Primarily, this is due to the performance of plastic pipes and not their cost. The applications range from water to gas to many other industries. It is not the plastic pipes that are competing with other materials. It is now the traditional materials that are competing with plastic pipes. Read on the statistics (Editor). More often than not, developments are triggered as industry encounters issues relating to cost and productivity. The growth of plastic pipes is spurred by innovations in pipe resins, in pipe structures, and in pipe processing technologies.
When pipes are ordered in smaller volumes and in different dimensions, producers face the dilema of cost-intensive dimension changes. The extrusion line is put to a halt, pipe head and downstream units are dismantled, die sets and calibration sleeves are replaced to get the line re-adjusted following new product dimension. Dismantled equipment must be cleaned and stored. It can take hours to get the line to run again into full production per specified dimension. Understandably, multilayer pipe make this problem even more time consuming. Moreover, pipes that are out of specifications made during the set-up period after the dimension change become reject products. Although the rejected pipes gets recycled (adding regrinds to the virgin) most of the time, associated cost of recycling is appreciable. This raises the question - can we not overcome this problem of time consuming changeover? How about having a process technology that would change one pipe dimension to another pipe dimension within a short period of time while having no pipe rejects? In fact, QuickSwitch does exactly that by just pushing a button in a matter of minutes without stopping the line.
How does the Technical Innovation Work
Implementing dimension change 'on the fly' has involved a series of major developments. Many of these were developed and tested in collaboration with the industry partners including a plastic pipe manufacturer.
The pipe head and the calibration system have been revised to accommodate the specific needs of the QuickSwitch
. The key feature of the new pipehead is the adjustable die gap. Shapes of the die and the mandrel are conical. The die gap can be easily enlarged or reduced by changing the axial position of the cone-shaped pin relative to the pipe head. The suction bell is stationed between the pipehead and the calibrating unit. Adjustable calibrating basket consists of hundreds of movable parts and does usual calibration function but uniquely across the line's full diameter range with high precision by turning an external wheel.
|Pipe head movement
Other components such as the suction bell, the vacuum tank end seal, the guide rolls, ultrasonic chamber, the haul-off and the cutting unit have been redesigned for continuous dimension change 'on the fly'. In fact, the operator has to select the next desired pipe dimension and the QuickSwitch control system, the key to the control system does the rest. For instance, the haul-off has its own diameter recognition and adjustment system with a fully automated pressure and counter pressure mechanism. As a result, the diameter is adjusted automatically or the dimension change takes place while the line is running.
Just because line does not stop and quick changeover takes place, benefits are many
- No line shut down. Time of cleaning and maintenance is greatly reduced. In turn, productivity increases
- Flexibility in production or shorter order lead times or just in time production and therefore, reduced inventory
- Less labour intensive. An operator can complete the changeover
- Reject pipe product is virtually eliminated. No headache of regrinds
- Key components are the pipehead, the suction bell, the calibrating basket, the haul off and the saw. The can be retrofitted to an existing extrusion line
Who are involved in this development
Although Krauss-Maffei in Munich has led the QuickSwitch extrusion system development, it has utilized complementary expertise of its partners. Egeplast Werner Strumann GmbH, Greven, has contributed in the process technology development while Atofina and BP Solvay provided the application engineering expertise on raw material polyethylene (PE). Currently, Egeplast has 4 extrusion lines that run with QuickSwitch extrusion technology.
What lies ahead
Currently, QuickSwitch system is able to cover pipe diameter ranges from 1.25” (32 mm) through 2.76” (70 mm) with QuickSwitch #1, 2.76” (70 mm) through 6.3” (160 mm) with QuickSwitch #2 and 6.3” (160 mm) through 9.8” (250 mm) with QuickSwitch #3 having the option of adjusting the diameter up or down. These ranges are being expanded to accomodate larger diameter pipes. Modified design of pipehead and new adapter will add or remove functional layers such as white liner in PE sewage pipe or abrasion resistant polypropylene (PP) in outer layer of PE pipe (trenchless laying). Changing the color code stripes from one to the other can now be done with two adapter system, saving the time on purging operations. Although QuickSwitch system has been developed focusing on PE material - it can be used with other thermoplastic materials such as PP. Developments in all areas (including PVC) are in progress.
1. A. Turk and H. Stieglitz, Proceedings Plastics Pipes XII, Milan, Italy April 19-22, 2004
Olivier Crave, Krauss-Maffei Corporation, 7095 Industrial Road, Florence, KY 41042, USA
Olivier Crave graduated from University of Technology Compiègne (UTC), France as mechanical engineer and received his pre-doctorate Master of Science in Energy from University of Franche-Comté (UFR), France. He has extensive extrusion business knowledge in both Europe and North America. In 1998, Mr. Crave joined Krauss Maffei Corporation as a sales manager in Paris (France). Currently, he is regional sales manager at Krauss Maffei Corporation and is based in Kentucky, USA.