US3769190A - Insulating supporting roller in cathodic protection system - Google Patents

Abstract

An underground gas main which is protected against electrolytic action by connection to a consumable or "sacrificial" anode of higher electric potential, is insulated from bridges or other grounded structures on which it is supported by supporting rollers of dielectric material which allow longitudinal movement but restrict lateral movement, and prevent passag of leakage current to ground.

Description

Oct. 30, 1973 Original Filed Dec. 2 Sheets- Sheet 1 FIG. 3.

mvmwon CHARLES E. DEEM, JR.

BY g, 4M4

ATTORNEY c; E. DEEM, JR 3,769,190 INSULATING SUPPORTING ROLLER IN CATHODIC PROTECTION SYSTEM 13, 1968 I Och 1973 c. E. DEEM, JR 3,769,19

INSULATING SUPPORTING ROLLER IN CATHODIC PROTECTION SYSTEM Original Filed Dec 13, 1968 2 Sheets-Shet 2 I0 42 I mvm'ron 6 CHARLES E. DEEM, JR.

ATTORNEY United States Patent INSULATING SUPPORTING ROLLER IN CATHODIC PROTECTION SYSTEM Charles E. Deem, In, Line Lexington, Pa., assignor to Utility Products Co., Bala-Cynwyd, Pa. Continuation of abandoned application Ser. No. 783,660, Dec. 13,, 1968. This application June 4, 1971, Ser.

Int. Cl. czar 13/00 Uls. c1. god-+191 1 Claim ABSTRACT OF THE DISCLOSURE An underground gas main which is protected against electrolytic action by'connection to a consumable or sacrificial anode of higher electric potential, is insulated from bridges or other grounded structures on which it is supported "by supporting rollers of dielectric material which allow longitudinal movement but restrict lateral movement, and prevent'passage of leakage current to ground. i

- the pipe is unaflected.

The protective current iskept to a minimum by substantially insulating the pipe from ground, but some leakage cannot be avoided. In passing over bridges and such metallic structures, the pipe is supported on rollers to provide for thermal expansion and contraction. These rollers are metal and are grounded through the metal structure so as .to directly ground the pipe, resulting in excessive current drain on the sacrificial anode.

Various means to avoid this leakage current through bridges. and like structures have been tried without success. Insulating bushings and washers are ineffective. They may be broken downby highvoltage surges, such as caused by lightning. They are subject to leakage due to dampness, or. snow and ice, and sometimes from carelessness in painting, and cannot be used on present-day bridge structures with metal corrugated concrete forms.

Insulators in the supports to isolate the pipe from a bridge structure have been used, but these are expensive and'impractical in many places. In modern bridge construction, the mains must be carried between the supporting beams, where space is inadequate for insulators on the supports.

The failure of these methods led to the practice of insulating the entire section of a gas main over a bridge from the protected pipe at opposite ends of the bridge. This-method isquite expensive and destroys the electric continuity of the main, leaving the section over the bridge subject-to corrosion.

Applicant avoids all these cumbersome and expensive and inadequate protective methods by one simple change in'present,systemsusing' insulating supporting rollers en the supporting units to isolate the pipe electrically from the bridge structure. These insulating rollers, which may be made of any dielectric material having the necessary strength to suppor'tthe pipe, are far less expensive than insulating the pipev section, and can be used with any type off pipe hanger where space may not allow the use of insulators. These rollers, may, also be applied in structures now in use by merely substituting the insulating rollers for the metal rollers.

The savings involved. in the use of insulating rollers over the present practice of insulating the pipe section over the bridge from the pipe at opposite ends are substantial. For example, on a typical installation of an 8- inch pipe having a -foot span, the eight rollers required to support the pipe section would be on the order of onethird of the cost of insulating the pipe section at its ends. At the same time, the electrical continuity of the pipe is maintained and the section across the bridge is adequately protected.

FIG. 1 shows a transverse section of a bridge with a gas main suspended below the bridge deck.

FIG. 2 is a section taken on line 2-2 of FIG. 1.

FIG. 3 is a central transverse section of the roller, taken on line 33 of FIG. 2.

FIG. 4 is a view similar to FIG. 2 showing another form of hanger structure.

FIG. 5 is a perspective view of a roller and support for a pipe.

FIG. 6 is a sectional view showing a different type of bridge structure with a modified form of pipe support.

FIGS. 1 to 3 show a pipe 1 supported on a bridge. In this construction, the concrete deck 2 is poured into and supported on a metal corrugated form 3. The pipe is supported on the bridge by supporting units connected to screw inserts 4, which are embedded in the concrete and rest on the corrugated form 3. Hanger rods 5 threaded in these screw inserts 4 carry blocks 6 on the lower ends adjustably held by nuts 7. A rod 8 extends between the blocks 6 and is seated in sockets 9.

A roller 10 is mounted for rotation on rod 9. The body of this roller 10 is molded of a suitable dielectric material such as an epoxy resin mixed with fiber glass, and with its periphery of channel shape curved to conform substantially to the curvature of the pipe. Various epoxy resins may be used. One example is a product sold under the name of Epi-Seal, called Spec. 10-40, manufactured by Bonded Products, Inc., of South Orange, NJ. The body of the roller is molded on the steel sleeve 11, which forms a bearing on rod 8 and also reinforces the roller. The relative thickness of the central sleeve or metal portion and of the dielectric body is not critical, as long as the peripheral portion in contact with the pipe is of dielectric material, or dielectric material is interposed between the pipe 1 and rod 8.

Longitudinal movement of the pipe may take place to allow for thermal expansion and contraction, but any lateral movement is prevented by the circumferential channel shape or curved saddle-shape of the body of the roller. The body of the roller is preferable longer than the diameter of the pipe to reduce the chance of contact with surrounding members. With its substantial area of insulating material and its curved shape to prevent shifting of the pipe, this roller efiectively isolates the pipe from the surrounding structure and the ground.

FIG. 4 shows an example of a hanger 20 in which the rods 21 are fastened as in the hanger of FIG. 1, but carry springs 22 which rest on spring seats 26 held by nuts 27. The same roller 10 may be supported on the blocks 26.

A stationary fixed base 30 is shown in FIG. 5, which may be bolted to a steel structure. A pin 32 rests in sockets in posts 31 on the base and carries a roller 36 which may be similar to roller 10, or may differ in configuration as shown in FIG. 5, but which is substantially complementary to the curvature of the pipe 1. p

A typical example of a bridge construction with the hanger structure and gas main is shown in FIG. 6. The bridge is constructed with pre-stressed concrete box beams 42 on which are supported corrugated metal forms with a concrete deck. The pipe lies between the beams, so that short hangers 40 are carried by the corrugated deck element 41, and the pipe may be as wide as said space except for the supporting element 5. The roller carried by this hanger provides for isolating the pipe electrically, where the space is insuificient for insulators.

The several embodiments of the invention herein described and illustrated are only examples of many possible applications of the invention, which is defined in the appended claim.

I claim:

1. In a fluid distribution pipe line in which a pipe passes through the earth and over a bridge having beams below its deck and is supported between said beams by supporting units fixed to said bridge, each of which has vertical metallic supporting elements between said beams on opposite sides of and spaced from said pipe, said pipe being protected over said bridge against electrolytic decomposition by an anode of higher electric potential connected to said pipe and the earth, and being electrically continuous to assure protection throughout its length against electrolytic action, each supporting unit comprising a rod below said pipe carried by said supporting elements and an insulating roller rotatable on said rod on 4. which said pipe rests and is movable longitudinally, said roller comprising a metal sleeve on said rod to form a bearing and a body of dielectric material having a peripheral portion of channel shape molded on said sleeve to insulate said pipe from said supporting elements and bridge structure, said peripheral portion of said roller being longer than the diameter of the pipe to prevent contact of said pipe with said supporting elements and to space said pipe from said supporting elements, so that a pipe may be carried by the bridge between said beams of a dirneter only slightly less than the distancebetween said beams.

References Cited UNITED STATES PATENTS Newbury 248- TA-HSUNG TUNG, Primary Examiner

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