System Changes Pipe Dimensions On-the-fly

Equipment producer Krauss-Maffei, Munich, Germany (U.S. headquarters are in Florence, KY), and pipe processor Egeplast Werner Strumann, Greven, Germany, have jointly created a system that can alter pipe dimensions without stopping an extrusion line. Called QuickSwitch, the system is said to reduce lost production time from an average of 10 h to between 5 and 10 min, decrease waste, and lower personnel costs.

Andreas Türk, pipe product manager for Krauss-Maffei, says that when pipe is ordered in small lots, producers must deal with frequent and costly changes to extrusion equipment. "The line has to be stopped, and the pipehead and downstream equipment have to be dismantled, cleaned, replaced, and readjusted," Türk explains.

He says pipe customers are showing a trend toward buying smaller quantities and expecting just-in-time deliveries in order to eliminate warehousing costs. Processors have had to become more flexible and develop an ability to change pipe dimensions and resins quickly.

Krauss-Maffei was approached by Egeplast on a quick-change system. The machine maker developed the design with input from the processor, which also conducted the equipment trials.

QuickSwitch allows stepless pipe-size changes on-the-fly. Only pipe extruded during size transitions are scrapped, but since size adjustment is quick, waste is reduced.

To do this, the pipehead, calibrating system, suction bell, vacuum tank end-seal, guide rolls, and haul-off all had to be completely reengineered, Türk comments, without revealing details. On the new system, the die gap can be enlarged or reduced by changing the axial position of the cone-shaped mandrel relative to the pipehead.

Wall thickness and diameter of the extruded pipe are controlled by the calibrating basket, which consists of movable segments with inner surfaces that combine to form a smooth, circular inner wall. The inner radius of this cylindrical calibrating basket can be changed steplessly.

The system is available in three versions with single-screw extruders for polyolefin processing. As denoted by their model numbers, KMQS 32-63 covers pipe diameters from 32 to 63 mm; the KMQS 75-160 unit handles 75- to 160-mm diameters; and the largest system produces pipe from 160 to 250 mm. The two smaller units can have an optional 70-mm position.

The average output of a 50-mm-dia line can be from 400 to 600 kg/h, Türk says. "There are no output limitations through the QuickSwitch system. Limitations are as [those] in normal lines: too-short cooling lengths, extruder capacity is too small, haul-off speeds are too low, or some similar problem," he claims.

Although he did not specify costs, Türk says payback of investment, which can cover either a completely new line or modification of an existing Krauss-Maffei extrusion system to include the QuickSwitch elements, is said to be under two years. He points out that the system is targeted at Europe and North America, where high pipe production costs can be reduced by shorter downtime and higher productivity.

So far, Egeplast is the only processor that has the system, which is being used to make water pipe. Türk says Krauss-Maffei is in negotiations with other processors and expects two to begin trials by the end of summer.

Türk says that although the line is suited to all types of polyolefin pipe, Krauss-Maffei recommends stopping the line to clean it when changing from high-density polyethylene to polypropylene. Otherwise, excessive non-spec, mixed-material pipe will have to be shredded.

The supplier will feature the QuickSwitch pipe-change system at NPE 2003 in Chicago next month (June 23-27), at stand 2002.