State of Technology Report for Force Main Rehabilitation, Final ...

Table 3-3. Properties of Hunting Polyurea Spray-on Linings
Tensile (ASTM D638) Flexural (ASTM D790)
Strength Modulus Elongation Strength Modulus Shrinkage
Type
psi psi %
psi psi
%
Flexible HE800 1,700 1,200 800 1,400 22,500 0
Semi-Structural
SS100
3,400 41,200 100 4,300 93,000 0.5
Fully Structural
FS250
12,000 160,000 20 9,300 250,000 1
3M
3M Water Infrastructure has announced a new product, Scotchkote Spray In Place Pipe (SIPP) 269
Coating, which is a patent pending-polyurea blend. The Scotchkote SIPP 269 Coating just received
certification against NSF 61 for use in potable water applications. The reference to a coating is
misleading as the material is actually intended to be used as a liner. Little technical data were available at
the time of this report. It is understood that the Trenchless Technology Center (TTC) will be conducting
some long-term performance tests on this polyurea material.
Nano-Enhanced Polyurea
The TTC at Louisiana Tech University is working with one vendor of polyurea resins to develop a nanoenhanced
version of polyurea, which would have even higher flexural modulus, well above the 250,000 to
375,000 psi (17,241 to 25,862 bar) achievable with today’s standard technology. The trade off with the
higher modulus is a lower elongation, but 5% elongation should be adequate for most pipe rehabilitation
projects.
3.4.3 Close-Fit Lining Systems. The use of close-fit liners is often called modified sliplining. It
involves the use of a thin walled PE liner with an outside diameter that is similar to the inside diameter of
the host pipe. The key to installing the liner is to temporarily reduce the liner diameter to facilitate its
insertion into the host pipe. Once the liner is in place, it is reverted back to its original outside diameter
forming a close-fit to the host pipe. The reinstatement of connections and fittings often requires special
techniques and fittings.
As shown in Figure 3-9, close-fit liners can be classified into two broad categories including those that
achieve temporary diameter reduction through: (1) a symmetrical reduction process; and (2) a fold-andform
process. In the case of the symmetrical diameter reduction process, these can rely upon either axial
tension or radial compression to reduce the diameter. Fold-and-form liners, depending on diameter, can
be pre-folded and coiled into spools at the factory or deformed on site.
Close-fit liners are usually thin walled (standard dimension ratio [SDR] > 33) so they maximize the
retention of flow cross-section. There are a range of products from which to choose including thin semistructural
liners to thicker fully structural liners. On the other hand, most liners are “non-standard” PE
diameters and require special fittings. Many of the early technologies came from the UK and were
subject to licensing and other commercial arrangements with international companies.
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