Currently available and well known plastic lined piping products comprise a family of pipes, fittings, and valves especially designed for handling corrosive or high purity liquids. Such products generally comprise steel lined with a polymeric material, e.g., polyvinylidene chloride, polypropylene, polyvinylidene fluoride, and polytetrafluoroethylene. Such products enjoy both the structural integrity of steel and the high chemical resistance characteristic of the selected polymeric liner. The external surface of such products often bears a thin coating of paint to protect the steel from corrosive substances found in the operating environment.
Each pipe, fitting, and valve will contain a flange at or substantially near each end thereof. Adjacent pipes, fittings, and valves, within a given pipeline, may be joined one to the other by the fastening together of such flanges, e.g., by bolting. Such bolts may be coated with a polymer, e.g., polytetrafluoroethylene, to inhibit the corrosion thereof.
To secure the polymeric liner within a given pipe, fitting, or valve, such liner is provided with a length greater than that of the bore through which it extends. Upon the application of heat and pressure, the liner is flared over the pipe end, which in some cases will be the anterior flange face. In such cases, the flaring will preferably not cause an extension of the liner to the circumferential edge of the flange. Thus, when adjacent flanges are secured together, e.g., by bolting, a gap remains between adjacent opposing anterior flange faces equal to at least the thicknesses of the flared polymeric liners. The presence of this gap precludes the conductivity of electricity between adjacent components when non-conductive bolts, e.g. polytetrafluoroethylene coated bolts, are used.
Methods of establishing electrical conductivity between adjacent components are known in the art. For instance, external lock tooth washers may be compressed between the bolt head and posterior flange face of a first component, and between the nut and flange of the adjacent component. Such washers bear teeth which serve to remove the paint from the outer surface of the posterior flange faces and the non-conductive coating from the bolts, thereby providing points of conductivity. While providing improved conductivity along a given pipeline, external lock tooth washers present undesirable complications. First, the installation of such washers or the replacement of a corroded washer after the assembly of the pipeline is impossible without dismantling at least the effected portion of the pipeline. This often involves clearing the pipeline of chemical substances contained therein, removing the connecting bolts, installing the washer(s), and retorquing the bolts. Second, the presence of external lock tooth washers causes torquing problems. Such washers cause an increase in friction between the nut and the posterior flange face. This increased friction is added torque, causing an inaccurate torque reading by the torque wrench. Thus, such washers may lead to insufficiently tight bolts, which may in turn lead to leaks at the pipe joint.
It is further known to provide conductivity clamps on adjacent components which bite into the paint and provide points of conductivity. A conductive wire connects the clamps located on adjacent pipes, providing a conductive path therebetween. Such clamps tend to be relatively expensive.
Those in the industry would find great advantage in a means for providing electrical contact between the opposing anterior faces of adjacent metal pipe flanges which is both cost effective and practical. Such means should be easy replaceable and should not result in torquing problems. The loss or corrosion of such means should likewise be easily detectable. Such means should preferably permit the establishment of electrical conductivity between relatively widely spaced anterior flange faces, e.g., anterior flange faces spaced approximately one inch apart.