Co-extrusion of foamed PVC pipes

The use of foam core pipes for low-pressure applications, such as sewage, drain pipes and cable ducts has seen tremendous growth over the past years. Currently pipe diameters of 32 mm to 630 mm are on the market.

• weight and cost savings
• higher productivity because the same output yields higher pipe footage
• usage of regrind possible
• existing lines can easily be adapted at low investment
• production process is very similar to that of solid pipes
• same couplings used as for solid pipes so no changes needed at processors plants
• Cincinnati Extrusion offers cost and weight saving calculations using a special software

• Cincinnati Extrusion offers both, conical and parallel twin-screw extruders for the produc-
  tion of foamed PVC pipes, even though conical extruders are recommended because of:
  • reduced back pressure forces due to the small cross-section at the screw tip
  • reduced bearing failure because of the larger center distance at the driven
    end of the screws
  • shorter than comparable parallel
    screw designs
• Cincinnati Extrusion twin-screw extruders guarantee exact temperature control,
  constant pressure and efficient homogeni-
  zation of the stock to ensure the even
  expansion of the material
• the blowing agent is added in-line to the dry
  blend using a small dosing unit with mixer

For foamed PVC pipes, Cincinnati Extrusion offers a feedblock system with decisive advantages:

• trouble-free operation throughout the entire process
• easy dismantling and cleaning
• standard pipe heads can be used (only the torpedo tip needs to be extended)
• reduced pressure build-up
• feedblock can be used for a wide range of pipe diameters, therefore lower investment costs
• small footprint

• downstream equipment very much corresponds to that of a pipe extrusion line for solid pipes, except of a longer cooling section, esp. a longer vacuum bath
• retroffiting of existing lines for solid PVC pipes is possible