Abstract: An elongated fluid detection device, together with a body of absorbent material, is located between the inner surface of a pipe and an impervious liner spaced from the inner surface thereof, the detection device being operatively connected to an external station. The impervious layer may be of a type normally used for relining defective pipes in situ, and the body of absorbent material, together with the fluid detecting element, preferably substantially filling the cylindrical space between the inner surface of the pipe and the impervious liner.

Abstract: A multi-layer tube suitable for use on motor vehicles composed of a cylindrical wall having an outer surface, and an inner surface essentially parallel to the outer surface. The cylindrical wall has a first region having an essentially uniform cross-sectional diameter and a second region which has a cross-sectional diameter differing from the essentially uniform cross-sectional diameter of the first region. The second region has at least one convolution contiguously adjacent to the cylindrical wall of the first region.

Abstract: A fuel dispensing system and method of making the same are provided, the system comprising a storage tank for the fuel and being disposed in the ground, a dispensing pump disposed above the ground, a first flexible hose construction having an inner surface and being disposed in the ground for conveying fuel from the tank to the pump, and a second flexible hose construction having opposed ends one of which is interconnected to the pump, the second hose construction being disposed above the ground for dispensing fuel from the pump into a fuel container of a transportation vehicle or the like through a nozzle interconnected to the other of the ends thereof, the second hose construction having electrical conductor structure extending therealong for dissipating static electricity from the nozzle to the pump, the first hose construction having leak detection structure for detecting leakage of the fuel therein through the inner surface therof and for providing an electrical conductor structure therealong for dissipa

Abstract: A multiaxial pipe system is provided particularly for use in underground fuel transfer between a fuel storage tank and one or more dispensing pumps. The pipe system includes a primary fuel flow line and a vapor recovery line mounted within a common outer containment conduit. Adapter fittings are provided on the ends of the fuel flow and vapor recovery lines for quick and easy connection to biaxial pipe fittings located respectively at the fuel storage tank and at each dispensing pump.

Abstract: A heat reshapeable rigid conduit and method for forming an elbow or offset having any desired bend radius therefrom. The rigid conduit is formed of a flexible metal tubing with a layer of heat softenable plastic preferably covering the exterior surface thereof. The conduit may be heated using conventional electric heaters on the job site, then shaped into the desired bend radius to form an elbow or offset. The plastic layer provides rigidity to the elbow or offset upon cooling. The flexible metal tubing has interlocking overlapping joined edges that permit flexing of the tubing when the plastic layer is heat softened. The flexible metal tubing resists the sawing action of a pulling line during the installation of an electrical conductor in the conduit. The plastic outer layer permits quick and inexpensive coupling between adjacent conduit sections.

Abstract: A hose (1) includes a main pressure cord layer (5) for holding a fluid, and an auxiliary pressure cord layer (7) formed so as to sheathe the main pressure cord layer (5) and to form a buffering space (9) for retaining the fluid leaking through the main pressure cord layer (5) between the main pressure cord layer (5) and the auxiliary pressure cord layer (7). The auxiliary cord layer (7) includes first and second cord plies in an asymmetrical structural relation capable of being twisted by the pressure of the fluid leaking through the main pressure cord layer (5). Thus, even if its main pressure cord layer and its rubber tube are damaged leakage of the fluid can be prevented.

Abstract: A mobile sewer cleaning apparatus having a rotating drum and a flexible hose wound thereon. Preferably mounted on the sewer cleaning apparatus is a device for measuring the length of hose paid out from the drum. The measuring device may be used, among other things, for measuring the speed of the hose as it is wound or unwound from the drum, and for controlling a safety device intended to stop the flow of water through the hose as the hose is being wound.

Abstract: An early warning system for a material transfer system having an elongated area to be monitored for internal wear caused by erosive flow action of a transfer material. A material transfer conduit has an inner surface forming a flow passageway for the transfer material and an outer wall surface with a wear detection indicator normally visible in situ at an elongate section of the outer wall and being subject to obliteration upon wear-through of an underlying portion. A translucent or transparent outer containment layer surrounds the outer wall surface of the transfer conduit The wear indicator is colored to contrast with the transfer material and indicates wear by an eroded area which can be visually observed through the outer translucent layer.

Abstract: A high-flexibility, noncollapsing, lightweight, large-bore, wire-reinforced hose is inside fiber-reinforced PVC tubing that is flexible, lightweight, and abrasion resistant. It provides a strong, kink- and collapse-free conduit for moving large quantities of dangerous fluids, e.g., removing radioactive waste water or processing chemicals.

Abstract: Described is an inner tube element for use in a double tube device for taking soil samples during drilling operation (coring), the inner tube element comprising distinguishable end parts which are connected by a tube member of fiber reinforced plastic. According to the invention such tube member is provided with an orientation marking over its whole length and at least covered by a thin layer of plastic. An attractive embodiment of such marking are parallel lines of different color. Also is described a method for producing an inner tube element by forming a tube member between two differing end parts by winding fiber material which is impregnated with hardenable synthetic resin and hardening the tube member then formed. According to the invention a material in strip form and bearing an appropriate orientation marking is incorporated during the forming of such tube member.

Abstract: A longitudinally heat shrinkable closure sheet has a hold-down adhesive portion adjacent each longitudinal end for application on the exposed end portions a heat shrinkable wrap-around sleeve applied around a pipe or other article to be covered. Heat is applied to the closure sheet in order to weld the adhesive free portion of the underside of the closure sheet to the end portions of wrap-around sleeve. The initial shrinkage of the closure sheet between the hold-down adhesive portions draws it tightly into contact with the upper side of the end portions. Shearing forces are applied between the closure sheet and the end portions firstly as the closure sheet contracts relative to the end portions, and secondly, as the sleeve shrinks, develops hoop stress and stretches the closure sheet, and a high strength fusion bond is achieved between the closure sheet and sleeve.

Abstract: An elongated fluid detection device, together with a body of absorbent material, is located between the inner surface of a pipe and an impervious liner spaced from the inner surface thereof, the detection device being operatively connected to an external station. The impervious layer may be of a type normally used for relining defective pipes in situ, and the body of absorbent material, together with the fluid detecting element, preferably substantially filling the cylindrical space between the inner surface of the pipe and the impervious liner.

Abstract: A secondary containment system for conduits, pipes and electric cables includes a plurality of separate duct sections connected in end-to-end relation to provide an electrically insulating fluid tight system. Each duct section includes a pair of generally Z-shaped structural members formed from a fiber reinforced plastic material with each structural member including top and bottom flanges for supporting a removable top cover panel and a rigidly joined bottom panel. The structural member top flanges are preferably shaped to deflect the top cover panel to present an outwardly convex top surface to prevent the collection of condensate and other fluids.

Abstract: A hydraulic safety hose with fluid removal conduit is disclosed which protects the operator from injury due to hose rupture as well as preventing environmental damage by containing the flow of escaping hydraulic fluid. The hydraulic hose comprises inner and outer pressure hoses with an annular passageway defined therebetween to receive hydraulic fluid in the event of rupture of the inner hose. A conduit including a shut-off valve fluidly communicates with the annular fluid passageway and extends outwardly and away from the inner and outer hoses so as to drain fluid from the annular passageway to a suitable remote reservoir in the event of rupture of the inner hose. The valve may be closed, as desired, to prevent fluid flow through the conduit and allow for continued emergency use of the safety hose.

Abstract: A heat shrinkable wrap-around sleeve comprises a heat shrinkable sheet with a heat stable strip welded on one end. The free end of the heat stable strip is overlapped on the outer side of the opposite end of the sheet and welded thereto by heating applied directly on the outer side. This allows a good quality welded connection to be formed without requiring the use of hold-down adhesives. The sleeve can be manufactured using induction welding or more preferably by heated wedged welding.

Abstract: A flexible hose construction and method of making the same are provided, the flexible hose construction comprising an inner tube made of polymeric material, an outer sleeve of reinforcing material disposed in telescoping relation on the inner tube from one end thereof to the other end thereof, rib structure disposed between the sleeve of reinforcing material and the inner tube, the rib structure being disposed on the inner tube so as to define alternating coil structure of rib structure and coil structure of non-rib structure serially along the longitudinal axis of the inner tube in a like repeating pattern thereof, the coil structure of non-rib structure comprise coil structure of void space, and an outer tube of polymeric material disposed between the rib structure and the sleeve of reinforcing material so as to extend in a generally straight-line manner from coil structure of the rib structure to coil structure of the rib structure so as to tend to prevent the sleeve of reinforcing material from entering i

Abstract: In a coaxial piping system for the transport of toxic and hazardous gases having an inner conduit wherein hazardouses gases are transported therethrough and having a spacer helically wound about the inner conduit within a volume between the inner conduit and an outer conduit.

Abstract: This coding band, in particular for electric cables, is provided, proximate o its longitudinal edges, with perforations adapted to be engaged by the traction elements of a computer printer and with a plurality of prepunched strips which extend substantially transversely to the longitudinal extension of the band. The strips delimit regions for printing identification codes for the cables to be tagged, can be individually removed from the band and can be inserted in a seat defined in a supporting element which is associable with at least one cable to be tagged. The strip further defines teeth for its retention in the seat.

Abstract: A fuel dispensing system and method of making the same are provided, the system comprising a storage tank for the fuel and being disposed in the ground, a dispensing pump disposed above the ground, a first flexible hose construction having an inner surface and being disposed in the ground for conveying fuel from the tank to the pump, and a second flexible hose construction having opposed ends one of which is interconnected to the pump, the second hose construction being disposed above the ground for dispensing fuel from the pump into a fuel container of a transportation vehicle or the like through a nozzle interconnected to the other of the ends thereof, the second hose construction having electrical conductor structure extending therealong for dissipating static electricity from the nozzle to the pump, the first hole construction having leak detection structure for detecting leakage of the fuel therein through the inner surface thereof and for providing an electrical conductor structure therealong for dissip

Abstract: A magnetically detectable plastic, e.g., polyethylene, polyvinyl, etc., pipe for underground use comprises a hollow tubular plastic pipe having particles of magnetic material embedded in plastic and secured integrally with the wall of the pipe. The magnetic particles are of iron oxide or barium ferrite and of a size, shape, distribution and proportion such that the plastic pipe may be easily detected by magnetic detection apparatus on the surface when the plastic pipe is buried at a selected depth under the ground. The magnetic particles are uniformly distributed throughout the thickness and uniformly distributed around the entire circumference of the plastic pipe or the magnetic particles may be distributed in discrete portions of the plastic pipe, as for example, a uniform outer layer of the pipe or in stripes or strips extending along the pipe.

Abstract: A device consisting of a plug and cap which provides a means of sealing, accounting for, and correct replacement of lines and fittings on the internal combustion engines and their associated components and controls removed, or separated during maintenance and testing.

Abstract: A retaining ring of an eyeball return fitting of the type used in swimming pools and spas is provided with a releasable or breakaway cover cap. The cap closes the end of the return fitting during construction. This permits the finish work for the cement and plaster stages of the pool construction to be effected without the danger of cement or plaster getting into the fitting during construction. After construction has been completed, the cap is released and drops away, carrying with it any cement or plaster which may have hardened on it during construction.

Abstract: A magnetically detectable plastic, e.g., polyethylene, polyvinyl, etc., pipe for underground use comprises a hollow tubular plastic pipe having particles of magnetic material embedded in plastic and secured integrally with the wall of the pipe. The magnetic particles are of iron oxide or barium ferrite and of a size, shape, distribution and proportion such that the plastic pipe may be easily detected by magnetic detection apparatus on the surface when the plastic pipe is buried at a selected depth under the ground. The magnetic particles are uniformly distributed throughout the thickness and uniformly distributed around the entire circumference of the plastic pipe or the magnetic particles may be distributed in discrete portions of the plastic pipe, as for example, a uniform outer layer of the pipe or in stripes or strips extending along the pipe.

Abstract: A device which provides an escape route from a fire. In a first aspect, the present invention provides a directional fire hose which enables a person a person, even in a dark and smoke-filled environment caused by a fire, to follow the fire hose in a direction away from the fire and toward safety. In a second aspect, the invention provides a directional carpet which enables a person, even in a dark and smoke-filled environment, to escape from a burning house or building. The invention is particularly useful for volunteer fire-fighters, inexperienced fire-fighters, and crewmen on a seagoing vessel or platform at sea.

Abstract: A piston type accumulator has a detection device that informs a user about the position of the piston incorporated therein. Abnormalities in the hydraulic system operations e.g., a gas leak from a gas chamber bounded by the piston or the sudden turning on of a fluid-actuated device in the system, can cause an excessive movement of the piston; likewise, clogging of lines or the sudden stoppage of a fluid-actuated device may cause a fluid pressure rise in the system and, consequently, a displacement of the piston to actuate the detection device. In this invention, the position of the piston is detected by use of a permanent magnet that actuates a reed relay or moves a magnetic inductive indicator installed on the outside of a accumulator shell to be readily visible thereat.

Abstract: In order to locate, trace, and identify hidden elongated objects, such as buried fiber optic cables, the objects are provided with elongated permanent magnet identifier devices having magnetic fields that may be detected at a distance from the objects. In one embodiment the identifier device comprises an elongated strip magnetized in the direction of its width and formed into a long-pitch helix, producing a characteristic "magnetic field signature" that enhances detection and identification of the object, as by a portable gradiometer that is moved over the surface of the earth along a line generally parallel to the length of the object. This embodiment may provide a magnetic field that diminishes as the square of the distance from the identifier device (rather than the usual cube of the distance), thereby enabling detection at substantial distances.

Abstract: A flexible, impermeable textile fabric tube is coated with a first polymeric layer which is opaque and to which is applied a second polymeric layer containing metal particles, preferably of good thermal reflectivity. The second layer is clear, or at least translucent, in the absence of metal particles.

Abstract: In order to locate, trace, and identify hidden elongated objects, such as buried fiber optic cables, the objects are provided with elongated permanent magnet identifier devices having magnetic fields that may be detected at a distance from the objects. In one embodiment the identifier device comprises an elongated strip magnetized in the direction of its width and formed into a long-pitch helix, producing a characteristic "magnetic field signature" that enhances detection and identification of the object, as by a portable gradiometer that is moved over the surface of the earth along a line generally parallel to the length of the object. This embodiment may provide a magnetic field that diminishes as the square of the distance from the identifier device (rather than the usual cube of the distance), thereby enabling detection at substantial distances.

Abstract: A device for locating a marker screw threadably engaged with a cover in duct means imbedded in a poured concrete wall construction including resilient fibers that are attached to the marker screw at one end and project beyond the outer wall surface but resiliently yield upon engaging with a finishing tool thus facilitating location of said marker screw after the wall has been poured.

Abstract: The locating of structural members disposed within the interstices of a concrete member can be accomplished by employing at least one indicator capable of showing the position of the structural member. The indicator also can show the directional location of the support members. The indicator of the present invention generally connects to a post member. This post member provides vertical support for the indicator system. A clamping assembly is attached to the post member and connects the structural member to the indicator system for fixing the location of the structural member. The clamping system can also identify the location of the structural member, and the indicator can then be provided to show the directional line of the structural member. Typically, the post member is sized to a predetermined length so that the longitudinal dimension of the indicator system corresponds to the thickness of the concrete member.

Abstract: Mandrel-cured, curved elastomeric hose is provided with an indexing mark that is formed prior to or during curing of the hose on the mandrel. The rigid curved mandrel has an exterior hose-bearing surface and an interior cavity. The cavity and exterior surface are connected by a small passageway or hole which is located where the index mark is to be made on the hose. A sleeve having a wall of uncured elastomeric material is mounted on the mandrel such that a portion of the sleeve covers the passageway. The mandrel having the sleeve mounted thereon is placed in an autoclave and subjected to steam pressure. The steam pressure forces elastomer material into the passageway and thereafter cures the elastomer sleeve into a hose. The pressure inside the cavity is approximately atmospheric at the introduction of the steam pressure. The cavity within the mandrel may be sealed except for the passageway or the cavity and the passageway may be vented to atmospheric pressure.

Abstract: A spirit level assembly attachable to a free end of a pipe section being installed includes a housing block of generally rectangular cross-section in which a series of viewing ports are formed through opposed side walls thereof. Fitted into each of the viewing ports is a spirit level vial or bubble. Integrally formed on the opposed ends of the housing block are cylindrical stubs of predetermined diameter corresponding to commonly encountered pipe sizes. The stubs are threaded in accordance with the National Pipe Thread convention. When the housing is screwed onto the length of pipe being leveled or plumbed, an appropriate bubble vial can be viewed to establish the desired horizontal or vertical orientation of that pipe segment.

Abstract: A blow off cap is provided for use in conjunction with a standard-type vent stack or blow off pipe. This blow off cap structure includes a cap structure fabricated from a plastic material having a top planar portion and a side wall having an upper and lower section, the upper section being a solid portion which extends in underlying relationship to the top surface, while the lower section has a shaped side wall adapted to engage the outer surface of a vent stack. A retention structure fabricated from an elastomeric material connects the cap structure to a clamping structure, which in turn fixedly secures the blow off cap to the pipe.

Abstract: An attachment for an appliance such as a washing machine that is connected to a water or other fluid inlet source that surrounds the hose connections from the fluid source to the appliance in a manner that prevents any leakage from the connector hoses from escaping into the vicinity around the appliance and flooding that area. Any excess fluid is instead directed via a drainage hose into an appropriate drainage site. The hose protector device has sleeves that cover and surround each individual hose connected to the appliance. The sleeves are interconnected to each other by a bridging conduit positioned between the sleeves. A drainage hose is attached to one of the interconnecting means and the sleeves so that any fluid accumulating in the sleeves is transported out of the sleeves through the drainage hose and into the appropriate drainage site, such as a floor drain or standpipe.

Abstract: This conduit locator is designed to indicate the location of an end of a conduit after concrete is poured over the conduit. Primarily, it consists of an adhesive tape having a multiple number of spaced rods adhered so as to extend from an edge of the tape, and the tape is adhered to the open end of the conduit which may be plugged or covered with out interfering with the rods extending upward. The rods are of a springy plastic and protrude upward after the concrete is poured over the conduit enabling the end of the conduit to be located beneath the surface of the concrete.

Abstract: A guide projecting into a bladder is provided on a plug of a vessel body. A cup-shaped sensor is slidably provided on the guide, and an element for actuating a switch is provided on the cup-shaped sensor. The cup-shaped sensor is caused to slide along the guide by the bladder deformable in accordance with change in the pressure of liquid within the accumulator, so as to actuate the switch.

Abstract: Multi-layer compensator with spacers arranged between the layers and with the spacers having the shape of flat strips distributed parallel to the longitudinal axis of the compensator over the circumference, with a gap between spacers.

Abstract: The subject invention is a direction indicating clamp for attachment to fire fighting hoses which indicate direction to exit the building. The invention consists of an elongated band fully or partially encircling the fire fighting hose with attached directional fingers protruding perpendicularly from the band. The clamp is placed upon the hose at prescribed distances thereby allowing the fire fighter to continue feeling along the hose and eventually to exit the building. Various embodiments of the invention encase the flexible clamp with soft rubber or a cloth material. In addition, the directional fingers may have a pointed end or may have raised letters indicating the exiting direction.

Abstract: A flexible hose suitable for use in seawater contains a small amount of copper dust in its elastomeric cover. The copper dust, even though present in a small amount, inhibits marine growth on the hose and prevents marine creatures boring very far into the hose. The hose is particularly suitable for the transportation of corrosive fluid such as crude oil.

Abstract: A bladder is disposed coaxially within a cylindrical container main body, a holder projecting into the bladder is provided on a top wall plate of the container main body, a sensor opposed to a bottom portion of the bladder and positioned within a moving locus region of the bottom portion or a deformable portion of the bladder is disposed at the bottom portion of the holder, and thereby, when the bladder deforms in response to variation of a liquid pressure the bottom portion of the bladder or the deformable portion of the bladder would actuate the sensor.

Abstract: A hose leak detector and a leak detector system for monitoring the leakage of fluid through at least a part of a flexible hose comprises signal generating means operable to generate a warning signal in response to leakage of fluid, test means for actuating the signal generating means, and timer means operable to cause the test means to actuate the signal generating means in a predetermined manner to enable a viability check of the operating capability of the signal generating means to be maintained.

Abstract: A floatable heavy duty hose assembly for conveying fluid entrained materials during dredging and related operations which includes a flexible cylindrical conduit which is reinforced at spaced intervals and wherein a plurality of floats are mounted in surrounding relationship with the conduit at the areas of reinforcement to thereby provide evenly distributed areas of flotation intermediate spaced areas of flexibility with the overall structure permitting the hose assembly to be handled and maneuvered in a uniform manner without undue interference by the floats.

Abstract: An insulated pipe apparatus comprises an inner conduit for carrying fluids, an insulated material surrounding the conduit which extends along substantially the entire length of the inner conduit, a sheet of corrugated material surrounding the insulating material so as to provide a plurality of substantially constant cross-section elongated voids along the length of the insulation, a rigid outer casing surrounding the corrugated sheet, and an end seal covering the end cross-section of the pipe apparatus except for the inner conduit and providing a means to interconnect the elongated voids and to connect them with external equipment. Slots cut into an insulating material may be substituted for the corrugated sheet to provide a plurality of substantially constant cross-section elongated voids. A gel coat may be added to the exterior surface of the outer casing to provide further protection from the environment for the pipe apparatus.

Abstract: Two tubes of thermo-plastic material are joined by a sleeve in an inner portion of which there is an electrical resistance coil, the ends of which are connected to terminals projecting from the outer surface of the sleeve. An electrical circuit supplies electric current to the coil to heat an inner weld zone to welding temperature, while leaving enveloping outer portions at lower temperature. In the sleeve there is provided a radial hole or recess into which the heated material expands upon reaching welding temperature. The material expanding into the hole or recess when welding temperature is reached is sensed by a pressure responsive micro-switch or electro-optically by an optical transmitter and receiver and through a control circuit, shuts off the power to the resistance coil. The parts being thereby fused together, are allowed to cool to complete the weld.

Abstract: A safety hose having a stretchable elastomeric tube and cover that sandwich a twined reinforcement that exhibits a circumferential reinforcement component and a weaker longitudinal reinforcement component that breaks when the hose is stretched.

Abstract: The duct (16) which delivers hot air (F) to the inside surface of the leading edge of a turbo-fan inlet cowl, for de-icing of the leading edge (11), is made double-walled (16,21) in order to safeguard from overheating the materials from which the cowl is constructed in the event of rupture of the duct. Preferably the flow of hot air in the outer duct blows open a hinged door (26) in the skin (10) of the cowl to provide a visual indication of the rupture of the inner duct. The outer duct can be made narrow enough to maintain working pressure in the inner duct after rupture.

Abstract: A kit for forming a secondary confinement installation for protecting earth from contamination due to leakage and spills from pipelines in small installations, such as service stations. The kit includes long trough sections and short connector sections with joints therebetween which maintain a level floor. The connector sections may have various shapes, such as right angle sections, half-right angle sections, T-sections, as well as a few special purpose sections. The special purpose sections include a sump section located at the low point of the installation, a dispenser unit section intended to provide catch basis for fluid dispensers and box sections which protect pipe egress zones at storage tanks.

Abstract: A dual wall safety tube assembly comprises an inner, seamless, stainless steel tube of extended length and an outer, welded stainless steel tube of the same length, in which the inner tube is connected as a process line without any junctions except for end couplings and the outer tube is similarly connected as a monitoring or inerting conduit. The assembly may include further options of electric heating cable, plastic jacketing and thermal insulation of fiberglass or similar material.

Abstract: A self-supporting pipe rupture and whip restraint system (10) for a process fluid pipe (12) of a nuclear reactor steam generator pressure vessel (14) includes a guard pipe (26) concentrically disposed about the process pipe (12) so as to entirely encase the process pipe (12) from the pressure vessel nozzle 18 to a terminal end fitting component (36) disposed exteriorly of the reactor facility building wall (32), the guard pipe (26) being integrally fixed to the process pipe (12) through means of the nozzle (18) and the component (36). Under postulated rupture conditions of the process pipe (12), pipe whipping of the process pipe (12) is restrained by the guard pipe (26), and the process fluid effluent from the process pipe (12) is contained within the guard pipe (26). Leak detection apparatus (50) is operatively associated with the annular space (30) defined between the process pipe (12) and the guard pipe (26) so as to detect ruptures or fractures within either the process pipe (12) or the guard pipe (26).

Abstract: A magnetically detectable plastic, e.g., polyethylene, polyvinyl, etc., pipe for underground use comprises a hollow tubular plastic pipe having particles of magnetic material embedded in plastic and secured integrally with the wall of the pipe. The magnetic particles are of iron oxide or barium ferrite and of a size, shape, distribution and proportion such that the plastic pipe may be easily detected by magnetic detection apparatus on the surface when the plastic pipe is buried at a selected depth under the ground. The magnetic particles are uniformly distributed throughout the thickness and uniformly distributed around the entire circumference of the plastic pipe or the magnetic particles may be distributed in discrete portions of the plastic pipe, as for example, a uniform outer layer of the pipe or in stripes or strips extending along the pipe.