Fail safe protective wrapping
Electrically conductive paths are positioned in and extend transversely across the width of the backing of strips of wrapping material. The electrically conductive paths provide means for conducting electrical current through spirally wrapped protective materials from the surrounding earth to voids formed adjacent the overlapped edges of the wrapping material and thus permit cathodic protection for pipe surfaces exposed to voids formed as a result of improper application or bonding failures of the wrapping material.
1. A wrapping material for buried pipe in the form of an elongated strip having a finite width comprising:
(a) a support backing having an inner face and an outer face;
(b) a layer of moisture-impervious material having an inner face and an outer face with its inner face secured to the inner face of said support backing; and
(c) a plurality of conductive paths supported between the outer face of said moisture-impervious layer and the outer face of said support backing and extending the full width of said elongated strip wherein said conductive paths are water-absorbing materials which become electrically conductive when wet.
2. A wrapping material for buried pipe in the form of an elongated strip having a finite width comprising:
(a) a support backing having an inner face and an outer face;
(b) a layer of moisture-impervious material having an inner face and an outer face with its inner face secured to the inner face of said support backing; and
(c) a plurality of conductive paths supported between the outer face of said moisture-impervious layer and the outer face of said support backing and extending the full width of said elongated strip wherein said conductive paths are strips of material which entrap moisture to form continuous electrically conductive paths.
3. A wrapped pipe comprising:
(a) an axially elongated metallic pipe; and
(b) a wrapping material in the form of an elongated strip having a finite width defining opposed edges spirally wrapped around said pipe so that one edge of said strip is adjacent the outer surface of said pipe and the opposite edge is exposed, said wrapping material comprising:
(i) a support backing having an inner face and an outer face;
(ii) a layer of moisture-impervious material having an inner face and an outer face with its inner face secured to the inner face of said support backing; and
(iii) a plurality of conductive paths supported between the outer face of said moisture-impervious layer and the outer face of said support backing and extending the full width of said elongated strip wherein said conductive paths are water-absorbing materials which become electrically conductive when wet.
4. A wrapped pipe comprising:
(a) an axially elongated metallic pipe; and
(b) a wrapping material in the form of an elongated strip having a finite width defining opposed edges spirally wrapped around said pipe so that one edge of said strip is adjacent the outer surface of said pipe and the opposite edge is exposed, said wrapping material comprising:
(i) a support backing having an inner face and an outer face;
(ii) a layer of moisture-impervious material having an inner face and an outer face with its inner face secured to the inner face of said support backing; and
(iii) a plurality of conductive paths supported between the outer face of said moisture-impervious layer and the outer face of said support backing and extending the full width of said elongated strip wherein said conductive paths are strips of material which entrap moisture to form a continuous electrically conductive path along the length of such strips.