Method and extrusion line for producing peroxide-cross-linked polyethylene pipes

• US 8,641,947 B2
• Filed: 01/24/2011
• Issued: 02/04/2014
• Est. Priority Date: 01/23/2010
• Status: Active Grant

• Current Assignee: iNOEX GmbH (CiTEX Holding GmbH)
• Original Assignee: iNOEX GmbH (CiTEX Holding GmbH)
• Inventors: Deters, Martin, Schmuhl, Jrg
• Primary Examiner(s): HAUTH, GALEN H
• Application Number:
  US13/012,685
• Publication Number:
  US 20110180954A1
• Time in Patent Office: 1,107 Days
• Field of Search: 264/492, 264/495, 264/209.5, 264/209.6
• US Class Current: 264/209.6
• CPC Class Codes: B29C 2035/0822 using IR radiation
• CPC Class Codes: B29C 2948/92123 Diameter or circumference
• CPC Class Codes: B29C 2948/92428 Calibration, after-treatment, or cooling zone
• CPC Class Codes: B29C 2948/92514 Pressure
• CPC Class Codes: B29C 2948/9259 Angular velocity
• CPC Class Codes: B29C 2948/92619 Diameter or circumference
• CPC Class Codes: B29C 2948/92647 Thickness
• CPC Class Codes: B29C 2948/92904 Die; Nozzle zone
• CPC Class Codes: B29C 2948/92923 Calibration, after-treatment or cooling zone
• CPC Class Codes: B29C 35/10 for articles of indefinite length
• CPC Class Codes: B29C 48/00 Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor extrusion blow-moulding B29C49/04
• CPC Class Codes: B29C 48/0017 combined with blow-moulding or thermoforming
• CPC Class Codes: B29C 48/0018 combined with shaping by orienting, stretching or shrinking, e.g. film blowing B29C48/0017 takes precedence
• CPC Class Codes: B29C 48/0022 combined with cutting
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/09 Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• CPC Class Codes: B29C 48/901 of hollow bodies
• CPC Class Codes: B29C 48/908 characterised by calibrator surface, e.g. structure or holes for lubrication, cooling or venting
• CPC Class Codes: B29C 48/91 Heating, e.g. for cross linking
• CPC Class Codes: B29C 48/9105 of hollow articles
• CPC Class Codes: B29C 48/911 : Cooling
• CPC Class Codes: B29C 48/913 : externally
• CPC Class Codes: B29C 48/92 : Measuring, controlling or regulating
• CPC Class Codes: B29C 55/22 : of tubes B29C61/08 takes precedence
• CPC Class Codes: B29K 2023/06 : PE, i.e. polyethylene
• CPC Class Codes: B29K 2105/101 : Oriented
• CPC Class Codes: B29K 2105/24 : crosslinked or vulcanised
• CPC Class Codes: B29K 2105/246 : Uncured, e.g. green
• CPC Class Codes: B29L 2023/00 : Tubular articles B29L2024/00 takes precedence ; catheters B29L2031/7542
• CPC Class Codes: B29L 2023/22 : Tubes or pipes, i.e. rigid bent tubes not for use as pipe couplings B29L2023/004

Abstract

A method and extrusion line for producing peroxide-cross-linked polyethylene pipes in an extrusion line having an extruder, a cross-linking furnace and a flue. The extruded tube is subjected to a stretching process, and the cross-linking furnace has a first heating section that extends from its inlet to an actuated deflection roller and a second heating section from the deflection roller to its outlet. The stretching process in the first heating section and the stretching process in the second heating section are monitored and regulated in such a manner that the necessary stretching of the pipe takes place primarily in the first heating section, and the stretching of the pipe in the second heating section is subjected to zero adjustment. In this case, the height of the deflection roller(s) of the cross-linking furnace and the angle of the heating sections to the horizontal plane can be height-adjustable.

Claims

1. A method of producing peroxide-cross-linked polyethylene pipes in an extrusion line that includes an extruder, a cross-linking oven and a withdrawal mechanism, wherein the cross-linking oven has a first heating section that extends from an inlet to an actuated deflection roller, and a second heating section that extends from the deflection roller to an outlet, the method including the steps of:

extruding a pipe via the extruder;

subjecting the pipe to a stretching process;

monitoring and regulating the stretching process such that stretching of the pipe takes place primarily in the first heating section of the cross-linking oven, wherein stretching of the pipe in the second heating section is controlled to be close to zero; and

withdrawing the pipe from the cross-linking oven via the withdrawal mechanism.

2. A method according to claim 1, wherein the monitoring step in the first heating section of the cross-linking oven includes measuring the respective diameters of the pipe both prior to entry into, and after exit from, the first heating section, and wherein the monitoring step in the second heating section of the cross-linking oven includes measuring the respective diameters of the pipe both prior to entry into, and after exit from, the second heating section.

3. A method according to claim 2, which includes the further step of controlling a rotational speed of the deflection roller such that an optimum stretching process of the pipe takes place in the first heating section.

4. A method according to claim 3, which includes the further step of effecting a sequence control of the speed of the withdrawal mechanism as a constant function of the rotational speed of the deflection roller.

5. A method according to claim 4, which includes the further step of linking a second control system with the sequence control of the withdrawal mechanism for reducing the speed of the withdrawal mechanism to such an extent that the stretching process of the pipe in the second heating section approaches close to zero.