PVC Foam Core Pipes are increasingly favoured for non-pressure applications. Its lower weight, savings in material costs and durability is making it popular. It also meets specific requirements of mechanical properties, compressive strength etc.

Advantages
Lower density with similar volumes i.e much lower weight. Easier to handle and install with lower shipping, installation costs as compared to compact PVC pipes
Much lower costs per unit of volume
Better insulating effect due to lower thermal conductivity
High temperature resistant
Higher productivity as against the compact pipe
Good chemical and abrasive resistant
Completely recyclable, low input of resources makes it very eco-friendly

3 - Layer PVC Foam Core Pipes
The outer and inside layers are rigid PVC with the middle “Sandwich” layer of foamed PVC. The very fine bubble

structure of the foamed layer is made out of either virgin PVC or PVC re-grind powder. This results in saving in weight of upto 30% as against compact PVC pipes. During production, care is taken to meet all specifications of mechanical properties, compressive strength, tolerance / dimensions for non-pressure pipe applications. They are manufactured to meet the universally accepted but stringent DIN Standards. Normally the layer thickness distribution would be - Outer Layer 10 - 15%, Middle Layer 60 - 80% and Inner Layer 10 -25% of the total pipe wall thickness.

Applications
For non-pressure applications like:
Drainage and Sewerage pipes.
Ventilation pipes.
Cable protection pipes

The Foaming Process
For this process chemical blowing agents or additives in micro-pelletized or powdered form are used. The endothermic and exothermic reactions of these agents, under heating, give off gases like C02 , N2, NH3 which produce the cellular structures in polymer matrixes.

Some critical factors which have a bearing on cellular structure quality of foam layer are:

Design of the screws and dies
Temperature control in the extruder and die
Charge volume and composition of the agent, as well as its distribution in the melt.
Cooling and haul-off after leaving the die.

A combined dosing and horizontal feeding unit is used to add the agent. for good control of the foaming process, the melt temperature should be between 175C-180C.

The Extrusion Line

This line normally containes two Extruders. A Main-Extruder is used tp produce the middle foam core layer and a Co-Extruder to produce the inner and outer skin layers.Standard Twin Screw configuration are used with internal temerature control. The main extruder is static, being anchored to the shop floor with the feed block being operated with one co-extruder, movable in the direction of the extrusion. This is cost effective and operationally easy. The thickness of the inner and outer layers in relation to the central layer is controlled via the extruder output during the functioning of the co-extruder.

It is also possible to retro-fit extruder lines of compact PVC pipes, for the production of 3 - layer pipes.

Foam Core Pipe Adapter

The sophisticated concept of the Co-extrusion adapterpermists the production of weight - reduced foam core pipes as well as pipes with a compact center layer made of low-cost reclaim. The pipes are shaped by a specially designed PVC Spider Die. the design of the adapter permits optional operation with two extruders for the compact inner and outer layer.

Better Return on Investment

The productiovitty of the foam Core pipe Line is much higher than that of a compact pipe line for simmilar dia, with same output rates. Line speed is higher, with lower production time and much lower usage of costly raw material. therefore, the additional initial cost for a foam core pipe extrusion line is quickly recovered after a short production time i.e. Better Return on Investment.

Conclusion

These 3layer foam core pipes have proven their excellent durability in rough everyday usage. This coupled with cost savings for both processors and users have ensured increasing growth rates, with promise of a lion's share of the market for non-pressure pipes.