Close-fit Lining
Close-fit lining is possible because of the memory properties of PE. PE pipe will change shape when force is applied to the material either through the application of compression or tension but will return to its original shape when the external force is removed or internal pressure is applied. This property allows the PE100 or PE100-RC pipe to be temporarily deformed and pulled into the host pipe. When the new pipe has been pulled to the desired position, tension on the pipe is released or internal pressure is applied and the pipe will return to its original shape. The versatility of PE pipe has spawned the development of a wide range of innovative close-fit lining systems.
There are several different techniques for achieving
close-fit PE lining:
|
Type
|
Modification
Location
|
Modification
Method
|
Modified
Shape
|
Reversion
Method
|
Examples
|
|
Symmetrical
tension |
On
site |
Static
die |
Circular |
Natural
(release of tension) |
Die
drawing |
|
Symmetrical
tension |
On
site |
Roller
die |
Circular |
Natural
(release of tension) |
Titeliner |
|
Symmetrical
compression |
On
site |
Multiple
rollers |
Circular |
Water
pressure |
Rolldown |
|
Fold
& Form |
Factory |
Hot
fold |
U
or C |
Steam
& pressure |
Compact
Pipe |
|
Fold
& Form |
Factory |
Cold
fold |
U
or C |
Air/water
pressure |
Subcoil |
|
Fold
& Form |
On
site |
Cold
fold |
U
or C |
Water
pressure |
|
|
Fold
& Form |
On
site |
Cold
fold |
U
or C |
Air/water
pressure |
Subline |
The tension methods rely on natural reversion due to the memory
properties of PE; when the tension is released the PE reverts to close to its
original diameter. but not to exactly that diameter. In order to attach end
fittings and connections it may be necessary to insert a pipe expander at the
ends to push the pipe to its original standard size.
Non-standard size couplings are available but are bespoke manufactured so may be expensive. Examples of manufacturers of these special fittings are Viking Johnson and Nova Siria.
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