Methods applied today to repair pipelines include: determination of a damaged section; pipeline uncovering in the disclosed damaged area; coating removal; defect type classification; defect localization through trimming; production of a flexible strip spiral blank on a mandrel together with a separating fluoroplastic film; film uncoiling and removal; formation of a multilayer protection coating from the said strip spiral on a damaged pipeline wall.

According to newly-designed technology, the following strip forming procedure, allowing to simultaneously prevent development of pipeline cracks and corrosion defects appearing along pipe wall forming line and its axis, improve quality and operational reliability of pipeline repair and rehabilitation procedures, cut costs incurred during strip spiral production process, is proposed. Preliminary impregnated armoring filler is coiled on a rolling mandrel rod; binder is melted from opposite sides with the help of heating rollers rotating at a speed of 0.007 to 0.03 mps, tension of 250 to 700 kgf and heating temperatures of 120-150° C. Armoring filler is packed in 2 to 10 layers. Each layer is a combination of a linen, satin or serge interweaving of two types of fibers and is similar to fiber glass fabric in which duck-like fibers are positioned in axial direction while base fibers - in its spiral direction. Volumetric ratio of interweave fibers and polymeric binder which typically consists of epoxy tar, 70%, and phenolformaldehyde varnish, 30%, ranges from 1:0.37 to 1:0.57. Process of hardening the blank and mandrel goes simultaneously under the following thermal conditions: increase of strip spiral blank up to 100° C within 3 to 4 hours, up to 130° C within 2 to 2.5 hours, and from 130° C to 160° C within 6 to 6.5 hours. Then the strip spiral blank is cooled down to 60° C within 5 to 6 hours.

The procedure of forming a multilayer protection coating the flexible strip spiral blank passes several stages: unwinding of the strip spiral blank coils from the mandrel rod with consequent separation of anti-adhesion fluoroplastic film; blank surface conditioning to get a lusterless color; rewinding of the strip spiral coils in original (the position coils had on the mandrel rod) or reverse (reverse position of coils, as compared with those they had on the mandrel rod) direction for further uncoiling of the spiral on a pipeline damaged section to repair it. Cold hardening adhesive is applied both on the uncoiled part of the strip spiral blank and on a damaged pipeline section in the amount of 200 to 300 grs per sq. meter of the gluing surface. The strip spiral and pipeline surfaces prepared for gluing are left in the open air for 10 to 30 minutes at the temperature of 15 to 35° C. The strip spiral coils are glued layer-by-layer with a pipeline wall and with each other; specific gluing pressure applied is 0.5 to 0.03 MPa (0.5 to 2 kg*s/cm²). The process of the adhesive hardening lasts from 2 to 24 hours for each layer of a multilayer protection coating. To glue the first layer of the multilayer protection coating made from the flexible strip spiral, adhesive of the following compound is used (vol., %):

To paste all the rest layers of the multilayer protection coating as well as to fill in the holes, grooves, cuts and recesses, adhesive of the following compound is used (vol., %):

The newly-proposed technology has some modifications; the difference is in process parameters and applied materials.

I.A.Yegorenkov

The state enterprise “Proizvodstvennoye obyedineniye Avangard”

141350, the Moscow obl. (region), Khotkovo, ul. Chernyahovskogo 9 kv. 53 To: I.A. Yegorenkov

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