US3315017A

US3315017A - Gasproofing leaking gas main

Info

Publication number: US3315017A
Application number: US330464A
Authority: US
Inventors: Woodrow E Kemp
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1963-12-13
Filing date: 1963-12-13
Publication date: 1967-04-18
Anticipated expiration: 1984-04-18

Description

W. E. KEMP April 18, 1%?

GASPROOFING LEAKING GAS MAIN Filed Dec. 13, 1965 I NVENTOR.

KE'MP The weight ratio of the tar-rubber 3,3 15,0l 7 Patented Apr. 18, 1967 3,315,017 GASPROOFHNG LEAKING GAd MAIN Woodrow E. Kemp, Pittsburgh, Pa., assignor to Koppel-s ompauy, Inc., a corporation of Delaware 7 Filed Dec. 13, 1963, Ser. No. 330,464

10 Claims. (Cl. 264-36) been further aggravated by the necessity of increasing line pressures in order to meet increased demands.

One solution to the problem is to excavate at the end pair over extended periods of time. 7

It is, therefore, an object of the present invention to provide a simplified way of sealing bell and spigot joints of cast iron pipes which eliminates the to seal each lasting sealing composition which can be readily applied from inside the pipes.

In accordance with the present invention, I have discovered that bell and spigot joints of cast iron pipes be sealed internally by contacting said joints from the interior surface with a sealing composition at a temperature of ZOO-450 F. and a pressure of 50-200 p.s.1.g. The composition comprises a three to "seven percent of a copolymer of 45-20 parts by weight of acrylonitrileand 55-80 parts by weight of butadiene in coal tar pitch together with an inert filler. solution to the filler is and the composition has F. within the range of 1000- within the range of 19:1 to 3:1 a Brookfield viscosity at 250 14,000 centipoises.

The environment in which the sealing compound is to be used is primarily natural gas with occasional exposure topropane air mixtures or gas produced by thermal cracking of petroleum oil which may contain aromatic oils and heavy unsaturated and aromatic hydrocarbons. In order to be economically feasible, the seal produced between abutting sections of pipe should last for an extended period of at least about years.

The rubber in the tar-rubber solution is a copolymer of acrylonitrile and butadiene, which is comprised of a major portion, 55-80 parts by weight of -butadiene-1,3, and a minor portion, correspondingly 45-20 parts by weight of acrylonitrile. It is a commercially available material having a government synthetic rubber designation of GR-A. The higher the acrylonitrile content the harder it is to dissolve the copolymer in the tar; the lower the acrylonitrile content, the less resistance the film has to solvents, such as paraflinic or naphthenic oils.

To facilitate the solution in the coal tar and reduce the mixer schedule time, the copolymer may be broken down on a rubber mill. A convenient copolymer for use in this invention is a butadiene-acrylonitrile synthetic rubber sold under the trademark Hycar and having a Mooney viscosity of from -100. The Hycar Type 1442 is sold in crumb form and readily goes into solution. The copolymer additionally gives the film elasticity, ductility, and reduced susceptibility to temperature changes. It has been found that if the amount of copolymer be less than three per cent by weight of The coal tar pitch in which the copolymer is dissolved may be of the types conventionally designated as RT-6 to RT-12 which are defined in ASTM Standards D490-47. Such tars have an overall float test, commonly used for testing the viscosity of semi-solid bituminous material, ranging from 20 seconds to 220 seconds as determined by ASTM Test Dl39-49.

The copolymer is readily dissolved in the tar by maintaining the tar under agitation at an elevated temperature while the copolymer is added to the tar. The copolymer does not dissolve well if the temperature of the tar is below 230 F., but if the temperature be greater than 315 F. the breakdown temperature of the copolymer is and the copolymer begins to decompose. The

tar Without separation or sludging.

The filler serves primarily as a viscosity increasing ingredient. Suitable inert fillers useful in my invention include sand, asbestos fibers, fiberglass, talc, and the like which may be used alone or in mixtures thereof. These are generally used in an amount ranging from about 5-25 percent of the total weight which corresponds to a weight ratio of tar-rubber solution to filler within the range of 19:1 to 3:1. When less than five percent is used, the sealing composition tends to flow out of the joints, whereas perature of around 250 F. Alternatively, the fillermay be mixed with the copolymer and the mixture added with agitation to the heated tar.

The above and in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are not intended as a definition of the invention, but are for the purposes of illustration only.

In the drawings wherein like parts are marked alike:

FIGURE 2 is an elevational view with portions broken out of another embodiment of the novel apparatus.

Referring to the drawing, FIGURE 1, it is conventional for sections of cast iron pipe 11 to be joined by a bell and spigot joint E2. The bell is a flared portion and the spigot is a beaded portion such that in the pipe line the spigot end slopes into the bell end forming a. space therebetween.

Conventionally, the cast iron pipe for such environments has a size between 4-48 inches and primarily in the range of 4-12 inches with the space between abutting sections of pipe being up to one-half inch wide and approximately one inch deep. This piping is subject to some movement as a result of settling and traffic vibrations and as a result of the linear expansion of the cast iron. Typically, the pressure in the six inch section of pipe is from 2-60 p.s.i.g. and the ground temperature is between 30-90 F.

The vibration and expansion of the sults after a period of time in leakage. To repair the seal so as to eliminate this leakage has been a difficult and expensive operation. It has involved, for example, digging holes every few feet and mechanically sealing the bell and spigot joints particularly from the outside joint.

In accordance with this invention there is provided a novel and simple manner of sealing the joints by forcing a sealing composition into the space between the joints internally of the pipe, thereby eliminating the need for uncovering the external surface of the pipe so as to seal the joint. In addition, the invention has the advantage that the seal is internal and therefore in the direction of the tendency to leak thereby blocking leakage which would be difiicult to ascertain by visual inspection.

The sealing of the pipe internally is accomplished by a novel apparatus comprising generally a pair of circular cast iron pipe re- -discs and 17 separated by spacer member 19 and in- 21 for the sealing composition along with a heating unit 23 for maintaining the sealing composition 25 at an operative viscosity.

Discs

15 and 17 may be substantially identical. In each disc as illustrated herein, the disc comprises a front portion 15f of rigid material such as metal, a gasket 16 able to withstand internal pressure during operation, and a rear portion 151' of rigid material such as metal. The gasket is thus sandwiched between the front and rear portions and provides a seal so that the assembly has a circumference substantially equal to the inside circumference of the pipe thus maintaining intimate contact therewith. Since these two discs 15 and =17 are held in spaced apart arrangement, a chamber 14 is formed together with the inside walls of the pipe 11 for the sealing composition 25.

As illustrated herein, the spacers 19 are fastened to discs 15 and 17 so as to maintain the discs parallel to each other and normal to the axis of the pipe. The spacers 19 are advantageously a plurality of rods although other shapes of spacers may obviously be used.

Disc 17 has an aperture therein in which is held the member for introducing the composition under pressure into chamber 14. As illustrated herein a flexible hose 21 is secured for example by a lock nut 22 to disc 17. Thus the composition can be introduced into chamber 14 by a suitable source not shown such as a pump and reservoir of the composition.

The composition tends to become less viscous as the temperature increases. Accordingly, the flexible hose 21 is advantageously provided with a means for maintaining the composition flowing through at a predetermined temperature. To this end, a heating element 23, which may be a metallic resistor, is passed through the flexible hose 21 and around a spacer 19.

As an illustration of the invention, a suitable tank steam jacketed is charged with the desired quantity of coal tar pitch, RTl2, having a viscosity of 220 seconds float at 50 C. as determined by ASTM Test Dl39-49. After bringing the temperature of the tar to approximately 300 F. the acrylonitrile-butadiene copolymer known as Hycar 1442 is charged through a chopper while maintaining good agitation with a suitable agitator, e..g., a turbine type. Agitation is continued with frequent sampling for consistency until the rubber is entirely dissolved. This takes approximately 1216 hours. Thereafter, the temperature is allowed to drop to approximately eluding a flexible inlet 250 F. and the fillers, e.g., asbestos fibers and talc, are charged slowly while maintaining agitation. The amount of filler added and the type of filler depends on the end viscosity and the flow characteristics desired for the partioular service.

Typically 72.9 parts by Weight of the coal tar pitch is charged, followed by 4.6 parts of the copolymer rubber which is dissolved to form a rubber-tar solution. There is then charged approximately ten parts by weight of magnesium silicate, 325 mesh, and short fibered asbestos known as 7M grade l2.5 parts to make a total of parts. After all the ingredients are thoroughly dispersed, the mixture is charged into suitable drums or containers which preferably have been lined with a silicon oil or silicon tight release paper to prevent sticking to the metal container and permits easy removal of the solid sealant.

In the field, the composition is charged into a kettle and heated to a temperature of approximately 250- 300 F. The material which had been solid becomes a liquid at this temperature. The kettle is preferably placed near the excavation that is made to uncover a suitable bell hole in the transmission gas main. After opening the gas main, a heated metallic flexible hose is connected to the kettle containing the molten sealant. This short length of hose in turn is connected to a suitable pneumatic pump. From the pump the flexible hose leads to a traveling plug device, of the type shown in the attached drawings, and this in turn is pulled through the pipe from another bell hole which may be 500 -1000 feet distance. The pressurizing pump is started and the traveling pullplug pulled through the pipe until an electromagnetic I locater locates a joint. The pressure is raised to approximately 100 p.s.i.g. The traveling plug kept at that spot for about 60 seconds giving adequate time for the seal ant to flow into the joints and seal the pipes. The pressure is then reduced and the plug hauled along the pipe. If a side tap is located by the electromagnetic locater the pressure is dropped completely and the plug rapidly pulled past the opening so that no sealant will enter the service lines. When the next joint is located, the plug is again stopped, the pressure built up, and the sealant forced into the joint as previously described.

The sealed joint is characterized by the following combination of properties:

(1) Impermeability to natural gas, propane-air mixtures and gas produced by thermal cracking of petroleum oil;

(2) A high degree of elasticity, especially in the required temperature range of 3090 F., to be able to withstand pipe movement as a result of settling, traflic vibrations, and expansion of the cast iron pipe without the sealant becoming brittle;

(3) Formation of an adhesive bond between the sealant and uncleaned cast iron pipe;

(4) A high solvent resistancy, and naphthenic oils;

(5) Flow properties of the sealant being such that the sealant will not flow from the sealed joint;

(6) The joints are pressure sealed with the sealant composition in the same direction as the gas tends to flow therefrom; and

(7) A long service life of at least about 15 years to make the sealing process economically feasible.

FIGURE 2 illustrates another embodimentof the novel apparatus for carrying out the invention. In this embodiment the structure is generally similar to the structure of FIGURE 1, that is, having

discs

15 and 17 and a flexible hose 21. However, in this embodiment spacer 19 is fixed to disc 17 but by a suitable seal spacer 19 is movable relative to disc 15. In addition, through disc 17 extends suitably pressure sealed a shaft 31 of a conventional motor 33 which is secured by conventional means such as, for example, attached to bracket 35. The shaft of this motor terminates as a thread or worm 37. This worm especially to parafiinic ttowardseach other the pressure then threads into nut 39 suitably fixed to disc 15. Thus as the motor turns, shaft 31 threads into 'nut 39 thereby moving disc relative to disc 17.

In accordance with this'invention, the novel composition is flowed into cha-mber 14, thereafter motor 33 is actuated causing thread 37 to turn thereby causing relative movement of

discs

15 and 17. Thus, as the discs move on the composition 25 in chamber 14 becomes greater than the pressure in flexible hose 21 causing the sealant composition, which has not flowed into the bell and spigot joint, to flow back into the reservoir. As the

discs

15 and 17 contact each other, the chamber has decreased or disappeared so that the apparatus may be moved through the pipe without danger of composition flowing into branch lines.

The foregoing has described a novel manner for sealing the joints of cast iron pipe without the heretofore trouble of digging the pipe to determine where the joints are and visually inspecting the joint to determine the leakage. The composition is permanent, is flexible, and is adhesive and the omt 1n the same tra distinction to the usual type of repair of the joint where the joint is repaired from the outside and the pressure building up within the pipe tends to force away the external seal.

I claim:

1. A method for internally sealing the joint between lengths of pipe comprising the steps:

(a) moving a traveling plug through said pipes to the vicinity of said joint, said plug being adapted to straddle said joint and seal otf an environment, within said pipes and on both sides of said joint, from the remainder of said pipes;

(b) flowing into said environment under pressure a sealant comprising a tar-rubber solution containing acrylonitrile and butadiene in coal tar pitch together with an inert filler at a temperature of 200-450 F.;

(c) maintaining said sealant under a pressure in the range of 50-200 p.s.i.g. for a period of time long enough for said sealant to penetrate and seal said joint;

(d) reducing said pressure in said environment to ambient within said pipe; and

(e) moving said traveling plug away from said joint along said pipes.

2. The method of claim 1 including the step:

(a) maintaining the temperature of the sealant in said environment at a temperature in the range of 200- 450 F. t

3. A method for sealing the joint between lengths of pc from the inside of said pipes comprising the steps:

(a) moving a traveling plug through said pipes to the vicinity of said joint, said plug being adapted to straddle said joint and seal off an environment, within said pipes and on both sides of said joint, from the remainder of said pipes;

(b) flowing into said environment under a pressure in the range of 50-200 p.s.i.g. a sealing composition at a temperature in the range of ZOO-450 F. comprising 3 to 7 percent filler, the weight ratio of said tar-rubber solution to said filler being within the range of 19:1 to 3:1;

(d) reducing said pressure in said environment to ambient within said pipe; and

(e) moving said traveling plug along said pipe away from said joint.

4. A method for internally sealing the joint between lengths of pipe adapted for carrying a fluid comprising the steps:

(a) moving a traveling plug through said pipes to the vicinity of said joint, said plug being adapted to straddle said joint and seal oif an environment, within said pipe and on both sides of said joint, from the remainder of said pipes;

(b) flowing into said environment under a pressure in the range of 50-200 p.s.i.g. a sealing composition comprising a tar-rubber solution containing from 3 to 7 percent of a copolymer of to 20 parts by weight of acrylonitrile and 55 to 80 parts by weight of butadiene in coal tar pitch and an inert filler, the weight ratio of said tar-rubber solution to said filler being within the range of 19:1 to 3:1, said composition having a Brookfield viscosity at 250 F. in the range of 1,000-14,000 centipoises whereby said joint is pressure sealed, said composition flowing into said joint in the same direction as the fluid flow in said p (c) maintaining said sealant under a pressure in the range of -200 p.s.i.g. for a period of time long enough for said sealant to penetrate and seal said joint;

(d) reducing said pressure in said environment to ambient within said pipe; and

(e) moving said traveling plug along said pipes away from said joint.

5. The method according to claim 4 wherein:

(a) said filler is selected from the group consisting of sand, asbestos fibers, glass fibers, talc, and mixtures thereof.

6. A method for internally sealing a leaking joint be tween lengths of pipe comprising the steps:

(a) locating leaking joint between adjacent lengths of (b) moving a traveling plug through said pipes to the vicinity of said leaking joint, said plug being adapted to straddle said leaking joint and seal ofl an environmerit within said pipe on both sides of said joint from the remainder of said pipes;

(c) flowing into said environment a sealing composi tion heated to a temperature in the range of 200- 450 F. and comprising a tar-rubber solution containing acrylonitrile and butadiene in coal tar pitch together with an inert filler; and

(d) moving one portion of said plug relative to the remainder of said plug within said pipes so as to exert a pressure on said sealing composition greater than the external pressure around said leaking joint whereby said sealing composition flows into said leaking joint and seals the same.

7. The method according to claim 6 wherein:

(a) said sealing composition comprises a tar-rubber solution containing from 3-7 percent of a copolymer of 49-20 parts by weight range of 19:1 to 3:1.

8. The method according to claim 6 wherein:

composition comprises a tar-rubber 7 percent of a coto 20 parts by weight of acrylonitrile and to parts by weight of butadiene in coal tar pitch and an inert filler, the. weight ratio of said tarrubber solution of said filler being within the range of 19:1 to 3:1; and

(b) said composition has a Brookfield viscosity at 250 F. Within a range of 1000-14,000 centipoises.

9. The method according to claim 8 including the step:

(a) maintaining the temperature of said sealing composition within said environment in the range of ZOO-450 F.

7 8 10. The method according to claim 9 wherein: 3,172,934 3/1965 Krieg 264-263 (a) said filler is a substance selected from the group 3,182,110 4/1965 Balcom et a1. 264-263 consisting of sand, asbestos fibers, glass fibers, talc 3,267,967 8/1966 Guthrie 138-97 and mixtures thereof. 5 FOREIGN PATENTS References Cited by the Examiner 547,821 1942 Great Britain.

UNITED STATES PATENTS OTHER REFERENCES 393,381 11/ 1888 McSWeeney 64- 6 Acrylonitrile, Union Carbide Chemicals Company 694,196 2/1902 Rose 25-38 X Technical Publication, p. 5 (1960). 907,724 12/1908 Boyle 25-38 10 1,736,293 11/ 1929 Van Denberg 264-36 X ROBERT F. WHITE, Primary Examiner. 1,946,619 2/1934 Furman et a1 X L. s. SQUIRE'S, T. J. CARVIS, Assistant Examiners.

3,168,909 2/1965 Zurbrigen et a1. 138-97

Claims

6. A METHOD FOR INTERNALLY SEALING A LEAKING JOINT BETWEEN LENGTHS OF PIPE COMPRISING THE STEPS: (A) LOCATING LEAKING JOINT BETWEEN ADJACENT LENGTHS OF PIPE; (B) MOVING A TRAVELING PLUG THROUGH SAID PIPES TO THE VICINITY OF SAID LEAKING JOINT, SAID PLUG BEING ADAPTED TO STRADDLE SAID LEAKING JOINT AND SEAL OFF AN ENVIRONMENT WITHIN SAID PIPE ON BOTH SIDES OF SAID JOINT FROM THE REMAINDER OF SAID PIPES; (C) FLOWING INTO SAID ENVIRONMENT A SEALING COMPOSITION HEATED TO A TEMPERATURE IN THE RANGE OF 200450*F. AND COMPRISING A TAR-RUBBER SOLUTION CONTAINING ACRYLONITRILE AND BUTADIENE IN COAL TAR PITCH TOGETHER WITH AN INERT FILLER; AND (D) MOVING ONE PORTION OF SAID PLUG RELATIVE TO THE REMAINDER OF SAID PLUG WITHIN SAID PIPES SO AS TO EXERT A PRESSURE ON SAID SEALING COMPOSITION GREATER THAN THE EXTERNAL PRESSURE AROUND SAID LEAKING JOINT WHEREBY SAID SEALING COMPOSITION FLOWS INTO SAID LEAKING JOINT AND SEALS THE SAME.