Solution for PCCP strengthening by prestressed hoops

orevaorevaDuraloop 50 year design life Customized solution

Patented anchorages

Repair during operation

The strengthening is achieved by adding exter-nal prestressed hoops, the number of which is determined to maintain full serviceability, even after complete loss of the initial prestressing force.

Foreva Duraloop is an alternative to the re-placement of defective pipeline elements. It is applicable to any PCCP/PCP with a diameter greater than (48) 1.2m.

Technical principleThe prestressed hoops counteract the bursting forces induced by the fluids inner pressure. Each hoop is made up of a greased and sheathed prestressing strand. The steel strand can slide in-side its plastic duct with a low friction, which en-sures that the tightening force is uniform along the 360 of the hoop.

Customized Design

The number of prestressed hoops is determined so as to provide safe operating conditions of re-paired PCCP/PCP, even under further losses of prestressing wires. Foreva Duraloop offers the

most effective spacing between hoops in highly damaged areas or for high pressure pipelines.

To mitigate border effects, the area reinforced with Foreva Duraloop is extended beyond the damaged zones with a increasing spacing.

In service, repairs are possible with reduced inner pressure. There is no need to drain the pipeline.

50 year design life

The steel strand is protected by four anti-corro-sion barriers. The first 2 barriers (grease and strand HDPE sheath) are applied at strand fabrication stage, then the strand is encapsulated in a plastic duct, injected with a special cement grout, which provide 2 additionnal layers of protection against corrosion.

Foreva Duraloop, exclusive Freyssinet solution, provides a cost effective solution for the rehabilitation of PCCP/PCP pipelines exposed to a risk of potential ruptures resul-ting from corrosion failures of prestressing wires.

Patented AnchoragesThe Freyssinet anchorages 1X15 and 2 X15 are designed to make one or two symmetrical hoops respectively.

The anchorage is specifically designed to avoid local punching forces on the pipe below the an-chor body and there is no need for local bursting reinforcement.

The anchorage has a 50 year design life based on a full encapsulation :

Corrosion-resistant (polyamide coated anchorage, HDPE cap) Perfect sealing against ingress of contaminants (O-ring elastomeric joints) Pressure-tested during cement grout injection to demonstrate integrity (44 psi / 3 bars)

After strand cropping, the protection against corrosion of the anchor is enhanced by careful grease injection.

PT arrangement at manholesA concrete saddle is cast around the manhole, using a Freyssinet designed self compacting concrete.

Easy and fast to installAfter excavation, the pipe surface is sand blasted and superficial damages are repaired with Foreva repair mortars (Foreva M110).

Once threaded inside the duct, the strand is placed around the pipe and the two ends of the cable are fixed in the anchorage.

Stressing is performed after injection and har-dening of the cement grout, which protects the strand sheath. Stressing is performed simulta-neously from both sides and in a symmetrical manner.

Once hoop installation is completed, the reinfor-ced area is back filled under the pipe. The soil is re-compacted by Freyssinet designed equipment to prevent from any settlement of the PCCP/PCP.

Field of applicationThe anchorage spacing is determined in relation to the nominal pipe diameter and the maximum operating pressures.

List of references available upon request.

ServicesFreyssinet provides the following assistance: inspection, monitoring, diagnosis and classifica-tion by priority order of the pipeline sections to be repaired.

Selection of Anchorage and Spacing

0,00 m

0,10 m

0,20 m

0,30 m

0,40 m

0,50 m

0,60 m

0,70 m

1,20 m 2,70 m 4,20 m 5,70 m 7,20 m

Inner Pipe diameters

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6 bars10 bars16 bars20 bars

1X15 2X15

Restricted area of use, studied case by case

Foreva SolutionsExtending life span of structures

Freyssinet 1 bis, rue du Petit Clamart - Bt C - 78140 Vlizy-Villacoublay - France Ph.: +33 1 46 01 84 84 - Fax: +33 1 46 01 85 85 www.foreva.fr

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