US3683061A

US3683061A - Pipe groove formation

Info

Publication number: US3683061A
Application number: US865024A
Authority: US
Inventors: Robert H Gates
Original assignee: Martin Marietta Corp
Current assignee: Lockheed Martin Corp
Priority date: 1969-10-09
Filing date: 1969-10-09
Publication date: 1972-08-08
Anticipated expiration: 1989-08-08

Abstract

Non-metallic, disposable rings are employed in the forming of a groove in the spigot portion of concrete pipe sections. This disposable ring is attached to either the header or the pallet section of a pipe-making form in proper position to form the desired groove in the spigot portion of the concrete pipe section during the making of the concrete pipe section. The ring is made of any rigid, non-metallic disposable material capable of resisting heat, water, alkali and steam. The disposable ring may be left in place when the header and pallet sections of the form are removed from the partially cured pipe. The ring may be removed from the pipe section some time after the pipe section has properly cured, preferably at the time the pipe section is to be used. The possibility of damage to the groove may thus be reduced or eliminated, and the groove may be kept free of dirt and other foreign matter until the pipe section is actually employed during the installation of a line of concrete pipe.

Description

United States Patent Gates 154] PIPE GROOVE FORMATION [72] Inventor: Robert H. Gates, Columbus, Ohio [73] Assignee: Martin Marietta Corporation, New

York, NY.

22 Filed: Oct. 9, 1969 [21] Appl. No.: 865,024

[52] US. Cl. ..264/317, 25/30 C, 25/39, 249/61, 249/100, 264/311, 264/318, 264/336 [51] Int. Cl. ..B28b 7/20, B28b 7/34, B28b 21/30 [58] Field of Search ..264/3l3, 317, 318, 333, 334, 264/336, 311; 249/61, 100; 25/44, 128 R,

39, 127 R, DIG. 24

[56] References Cited UNITED STATES PATENTS 1,363,912 12/1920 Pauly ..264/336 X 2,929,124 3/1960 James ..25/DIG. 24 3,421,551 l/1969 Currier ..249/6l X Primary Examiner-Robert F. White Assistant Examiner-J. H. Silbaugh [151 3,683,061 1 Aug. 8, 1972 Attorney-John A. Crowley, Jr. and Alvin l-l. Fritschler ABSTRACT Non-metallic, disposable rings are employed in the fonning of a groove in the spigot portion of concrete pipe sections. This disposable ring is attached to either the header or the pallet section of a pipe-making form in proper position to form the desired groove in the spigot portion of the concrete pipe section during the making of the concrete pipe section. The ring is made of any rigid, non-metallic disposable material capable of resisting heat, water, alkali and steam. The disposable ring may be left in place when the header and pallet sections of the form are removed from the partially cured pipe. The ring may be removed from the pipe section some time after the pipe section has properly cured, preferably at the time the pipe section is to be used. The possibility of damage to the groove may thus be reduced or eliminated, and the groove may be kept free of dirt and other foreign matter until the pipe section is actually employed during the installation of a line of concrete pipe.

17 Claims, 1 Drawing Figure PIPE GROOVE FORMATION BACKGROUND OF THE. INVENTION 1 Field of the Invention This invention relates to concrete pipe sections. More particularly, it relates to an improved process for the manufacture of such pipe sections and means for preserving such sections prior to use.

2. Description of the Prior Art Large quantities of concrete pipe sections are produced every year by various techniques such as the wet cast, dricast and machine processes. In such processes, concrete mixes are placed in a pipe-making form to produce pipe sections from which the forms are stripped either immediately or at some later time. Newly formed concrete pipe sections are generally passed through a kiln with the header and pallet sections of the pipe-making form in place. After passing through the kiln, the pipe section is generally transferred to a curing yard where the header and pallet are removed from the partially cured pipe. The concrete pipe section at this point is in a relatively green state with curing being fully completed within a period of 3 to 28 days.

Concrete pipe sections produced by the various known methods have grooves formed in the spigot portion thereof by the use of reusable snap rings. These rings, typically made of cold rolled steel, are attached to either the header or the pallet section of the pipemaking form and are positioned so as to form the desired groove in the spigot portion of the concrete pipe section. The size and shape of the steel snap ring is determined by the desired size and shape of the spigot groove. When the pipe section is formed with its bell portion down, the steel snap ring is attached to the upper or header section of the pipe-making form. When the concrete pipe section is made with its bell portion up, on the other hand, the steel snap ring is attached to the lower or pallet section of the pipe-making form, so that the groove may be formed in the spigot portion of the concrete pipe section.

In actual concrete pipe production, it is necessary that each steel snap ring he used continually with a particular header or pallet section of the pipe-making form. As a result, it is conventional practice to remove the steel snap ring at the same general time that the pallet or header are removed from the partially cured pipe section in the curing yard. The steel snap ring is thereafter thoroughly cleaned and transported back from the curing yard to the pipe manufacturing location to be matched up with its associated pallet or header sections for re-use in the manufacture of additional concrete pipe sections. While such steel snap rings are suitable for forming the desired groove in the spigot portion of each concrete pipe sections, the cost of each snap ring and the necessity for cleaning it and for assuring its return for further use with a particular pallet or header constitute objectionable features of present pipe-making practice.

The steel snap rings are recovered in the curing yard by prying the rings apart to free them from newly formed concrete pipe sections. The particular force thus required to pry apart the ring sometimes causes the snap ring to become distorted out of its required shape. This is particularly true with respect to the snap rings employed for small pipe sizes, such as those on the order of from about 6 inches to about 24 inches in diameter. Even in larger pipe sizes, however, steel snap rings require considerable effort for their removal, and the possibility of distortion exists. The reconditioning or replacement of such steel snap rings constitutes an additional item of expense for the producers of concrete pipe sections.

Because of the difficulty in removing such steel snap rings from the pipe and the relatively green state of the concrete pipe sections at the time the rings are removed, an undesirably high incidence of spigot groove damage is normally encountered. Up to about 10 percent of the pipe sections produced by conventional techniques, for example, generally have some form of groove damage occasioned by steel snap ring removal. In some instances, this groove damage may be repaired by special patching methods. An estimated percent to percent of the damaged pipe may thus be repaired and ultimately shipped to its destination. The remaining 20 percent to 30 percent of the damaged pipe, however, are subjected to rejection and, as such, are unusable except as second-grade pipe at a greatly reduced selling price.

To avoid this problem, the groove-forming reusable ring is sometimes made in two semicircular sections for ease of removal. For maintenance of a proper joint configuration, however, this technique requires the use of matched ring section sets. This, again, is difficult to control, and requires further provisions for setting and maintaining alignment where the semicircular sections oin.

The economic and technical necessity for removing the steel snap ring from a partially cured concrete pipe section not only subjects the spigot groove to potential damage during ring removal, but subjects the groove to the risk of further damage in yarding, handling, loading and unloading and shipping to its point of use.

After the spigot groove has thus been exposed by the removal of the steel snap ring, the groove is susceptible to the collection of grit, dirt, grease and other foreign matter that would be damaging to the round rubber gasket subsequently placed in the spigot groove when the pipe sections are joined, spigot to bell, to form a line of pipe. Specifications generally require that the spigot groove shall be clean and free from all grit, dirt, grease and other foreign matter at the time pipe sections are installed. Concrete pipe sections are generally delivered and strung out along the job sometime prior to laying. In sewer jobs and similar applications, all types of dirt and foreign matter can collect in an exposed groove between the time of delivery and installation. The necessity for taking additional preventive action or of efiecting a thorough cleaning of the spigot groove on site represents a further disadvantageous feature of conventional concrete pipe applications.

It is an object of the present invention, therefore, to provide an improved process for the production of concrete pipe sections.

It is another object of the invention to provide an improved process for the forming of the groove in the spigot portion of said concrete pipe sections.

It is another object of the present invention to provide a method for reducing damage to the spigot grooves of concrete pipe sections.

It is a further object of the invention to provide a method for maintaining the spigot grooves of concrete pipe sections clean and free from dirt and other foreign matter prior to use in pipe-laying applications.

With these and other objects in mind, the present invention is hereinafter described in detail, and the novel features thereof are particularly pointed out in the appended claims.

SUMMARY OF THE INVENTION The groove in the spigot portion of a concrete pipe section is formed by the use of a non-metallic disposable ring in conjunction with the conventional header and pallet sections of a pipe-making form. The disposable ring is attached to either the header or the pallet in proper position to form the desired spigot groove. After the heat treatment of the newly formed pipe in a kiln, the header and pallet are removed from the pipe. The disposable ring, however, may be left in place on the pipe until after the pipe has fully cured. Preferably, the pipe may be shipped to its point of use with the disposable ring still in place, so as to protect the groove from possible damage and the accumulation of dirt and other foreign matter.

The disposable ring may be made from any suitable non-metallic material that is rigid and resistent to heat, water, alkali and steam. Because of thy very low cost of such a disposable ring, it may simply be discarded when it is removed from the pipe.

BRIEF DESCRIPTION OF THE DRAWING The invention is hereunder described with reference to the accompanying drawing in which the single FIGURE is a partial sectional view of a concrete pipe section showing the relative positioning of the header and pallet sections of a pipe-making form and the position of the disposable ring in one particular embodiment thereof.

DETAILED DESCRIPTION OF THE INVENTION The disposable groove-forming ring of the present invention may be made of any convenient non-metallic material that is of a rigid nature and is resistant to the types of environment encountered in the production of concrete pipe sections. Thus, the material should be resistant to heat, water, alkali and steam. While the particular material from which the disposable ring is made is not a critical feature of the present invention, the ring can conveniently be made from such materials as paper or cardboard, leather, leather substitutes, hemp, fabric, fiberglass, wood, plastics and rubber. Disposable paper rings made from either reconstituted paper waste or chip board, such as the rings made from either of these materials by the George 0. Jenkins Company, have been found particularly suitable and economical for the purposes of the present invention.

It is also within the scope of the present invention to employ treated materials, such as a resin-impregnated paper or an oil-treated paper in the formation of the disposable rings herein contemplated. Likewise, it is within the scope of the present invention to treat a preformed ring prior to its use in order to enhance its resistance to the above-indicated environments.

As used herein, the term non-metallic disposable ring is meant to include groove-forming rings made of any suitable non-metallic material that permits the economical use of the ring on a single, or one-shot, basis in accordance with the teachings of the present invention. While an economic determination concerning the use of disposable, throw-away rings may conveniently be expressed in terms of the cost of the disposable ring vis-a-vis steel snap rings with relation to the cost of the particular concrete pipe section being produced, it will be appreciated that this determination is made not only on the basis of the cost per se, but also in light of the practical production and operating advantages obtainable in the practice of the present invention. The significance of these advantages tends to greatly enhance the commercial feasibility of employing non-metallic disposable rings in place of conventional steel snap rings.

For purposes of this invention, the cost of such nonmetallic disposable rings will generally range from about 4-5 percent, up to about 25-30 percent, of the product price per foot of the length of the pipe section produced. The cost preferably will be from about 4-5 percent to about 8-10 percent. It is economically feasible to leave each ring in the formed pipe groove in accordance with the present invention to protect the groove from damage and dirt accumulation. The cost of conventional steel snap rings, by contrast, generally ranges from about percent for larger diameters of produced pipe to about 400 percent for the smaller diameter sizes. For the practical technical and economic reasons set forth above, such steel rings cannot be used in the manner disclosed and claimed herein.

The size and shape of the non-metallic, disposable ring will be the same as that of the steel snap rings used in conventional practice. Such rings are usually of circular configuration, with a rectangular or trapezoidal cross-section equal in size to the size of the desired groove in the spigot portion of the concrete pipe. Steel snap rings are commonly provided with a radial split therein for ease of application, and the non-metallic, disposable rings of the present invention may likewise contain a radial split, if desired, although such a split is not necessary to the proper use of the disposable rings. As with conventional steel snap rings, the disposable rings may be attached to either the header or the pallet section of the pipe-making form, depending upon the manner in which the pipe is to be formed. Concrete pipe sections are conventionally formed with the pallet portion of the form on the bottom and the header portion on the top. If the pipe section is formed with its bell portion down, the ring is attached to the inner surface of the header portion of the form in order to form the desired groove in the spigot portion of the pipe. If, on the other hand, the pipe section is formed with its bell portion up, the disposable ring is attached to the pallet portion of the form so as to likewise form the desired groove in the spigot portion of the concrete pipe section.

The disposable ring may be secured to either the header or the pallet section of the pipe-making form by any convenient means. When the material from which the ring is made is of a liquid absorbent nature and tends to swell when wet, the disposable ring may be conveniently attached by soaking the ring in the liquid and thereafter positioning it in its proper location of either the header or the pallet portions of the form. As the wet ring tends to expand, a tight fit between the ring and the pipe-making form is obtained, so as to hold the ring in its proper position during the formation of the pipe. A paper ring may, for example, be soaked in water for this purpose. If the ring has been oil-treated or otherwise made non-water or other liquid absorbent, however, this technique cannot be employed.

In other embodiments of the invention, the disposable ring may be retained in its proper groove-forming position by mechanical means. For example, a mechanical catch, such as a pin or a capscrew, may be passed through either the header or pallet portions of the form so as to protrude very slightly under the disposable ring, so as to catch or hold the disposable ring in its desired position and to prevent its falling therefrom. For this purpose, the mechanical catch need only extend very slightly past the inner surface of either the header or the pallet, for example, on the order of about three thirty-seconds inch.

In conventional pipe section production, the newly formed pipe is passed into a kiln with its pallet and header portions in place on the pipe. After a period of about 12 to 24 hours, the pipe is transferred to a curing yard where the pallet and header are removed from the pipe. The steel snap ring employed in conventional practice is removed at the same time as the pallet and header sections. As discussed above, the risk of damage to the green concrete during the removal of the snap ring is considerable. In addition, the groove in the partially cured pipe is thereafter susceptible to damage, unless other means are taken to protect it from damage while it is in storage in the curing yard and thereafter in the subsequent handling, loading, unloading and transport of the pipe. Since the disposable, non-metallic ring of the present invention need not be returned to the pipe-making location for re-use, there is no necessity, in the practice of the present invention, for removing the ring from the pipe until the concrete in the pipe has fully cured. Advantageously, the disposable ring may be retained in the spigot groove during the entire time the pipe section is in the curing yard and thereafter until it is ready for use in the installation of a line of pipe. As a result, the ring is in effect embedded in the spigot groove, the cross sectional size of the groove being equal, of course, to that of the ring around which the concrete is placed. The small amount of adhesion that will exist between the ring and the concrete in which it is thus embedded provides an inherently tight seal that prevents dirt and other foreign matter from accumulating in the groove, while also preventing inadvertent damage to the groove as a result of chipping and the like.

Referring now to the drawing, the concrete pipe section illustrated therein has a bell portion 1 and a spigot portion 2. In the formation of the pipe with its bell portion down, header section 3 of the pipe-making form is positioned at the spigot end of the pipe section and pallet section 4 is positioned at the bell portion of the pipe section. The inner section of the pipe-making form is not shown in the drawing. The desired groove in spigot portion 2 is formed by means of disposable ring 5 attached to the inner pipe-contacting surface of header section 3. As in conventional practice, the concrete pipe section is fonned with longitudinal steel rods 6 and circumferential steel rods 7 for reinforcement.

In the illustrated embodiment, mechanical means are employed for retaining disposable ring 5 in its proper groove-forming position. Thus, capscrew 8 passes through header 3 and projects slightly into the spigot area so as to prevent disposable ring from dropping out of its pre-determined position. Slight indentations in the concrete in the outer surface of the spigot portion beneath the groove therein will naturally result at the points at which such cap screws are employed.

In the field, a line of pipe is installed by inserting the spigot portion of one pipe section in the bell portion of the adjoining sections. A rubber gasket is set in each spigot groove so as to seal each assembled bell and spigot joint. The disposable ring in the present invention not only is used to form the spigot groove, but also to act as a groove-protecting packing because of its inherently tight fit in the groove portion of the concrete pipe secton.

Highly significant advantages effecting both the production and use of concrete pipe are obtainable by means of the present invention. Elimination of the need for conventional steel snap rings that must be reused for reasons of economy serves to avoid the necessity for cleaning such rings after removal from the pipe and the time and expense involved in transporting the rings back from the curling yard to the production area. The practical necessity for matching a particular steel snap ring with a particular header or pallet throughout the production cycle is avoided. The additional inconvenience and cost of occasional repair of damaged rings is also eliminated. The necessity for replacement of the relatively expensive steel snap rings, due to damage or misplacement, is likewise overcome by the use of very inexpensive, disposable rings that are not intended for reuse.

In addition to such production advantages, the present invention greatly reduces or eliminates the damage to the spigot groove that frequently occurs in conventional operations. A major cause of groove damage is the practical necessity for removing the metallic snap ring while the concrete in the pipe is still in a green state. Since the disposable rings employed in the present invention are to be thrown away after one use, there is no necessity for removing the rings from green concrete. The disposable rings may readily be left in place on the pipe until the concrete has completely cured. This normally requires a period of at least three days.

Leaving a disposable groove-forming ring in place on the concrete pipe also serves to greatly reduce the likelihood of groove damage during subsequent handling, loading, unloading, storage and transporting of the concrete pipe section. The tightly fitting disposable ring tends to assist the concrete in absorbing bumps or blows that might otherwise tend to break off the edge of the groove or otherwise damage it, so that the pipe no longer meets specifications. As much as percent or more of the groove damage of this type can be avoided by retaining the disposable ring in the spigot groove as provided in this application. This represents a major cost saving for pipe producers who would otherwise be required to undertake costly patching operations or to sell rejected pipe as second grade pipe at a greatly reduced price.

The additional major advantage of the present invention is of particular benefit to contractors or pipe installers. Contract specifications generally require that the gasket recess, i.e., the spigot groove, shall be clean and free from dirt, grit, oils and/or other foreign matter at the time the pipe is installed. Concrete pipe sections are ordinarily delivered to a job site and strung out in line sometimes prior to the actual laying of the pipe. Sewer construction and various other applications for concrete pipe are essentially dirty operations, and a considerable amount of dirt and foreign matter tends to collect in the spigot groove between the time of delivery of the pipe to the job site and the time of installation. This generally requires that the groove be thoroughly cleaned prior to installation. With the disposable rings tightly fitting in the spigot grooves, however, the pipe sections may be kept entirely free from the accumulation of dirt and other foreign matter in their spigot grooves until the pipe section is actually installed. This saving of labor and expense in the field further enhances the revolutionary improvement in the concrete pipe art that is achieved by means of this invention.

While the invention has been described herein with respect to particular embodiments thereof, it will be appreciated that various changes and modifications can be made therein without departing from the scope of the invention as set forth in the appended claims.

Therefore, I claim:

1. A process for forming a groove in the spigot portion of a concrete pipe section comprising:

a. attaching a non-metallic disposable ring to the inner, pipe-contacting surface of the header section of a pipe-making form, said ring having a rigid nature and comprising a heat, water, alkali and steam resistant material conforming in size and position on said header to the desired size and position of the groove in the spigot portion of said pipe section;

. forming said concrete pipe section with its spigot end up and in contact with the inner surface of said header section;

c. subjecting said concrete pipe section to heat treatment while in its pipe-making form with the disposable ring in its predetermined position on the inner surface of said header; removing said header and the pallet section of the pipe-making form from said heat-treated concrete pipe section prior to the curing of said pipe section beyond the green state while retaining said disposable ring in groove-defining position on the surface of said pipe section;

e. curing said pipe section beyond the green state and thereafter removing said disposable ring from the spigot portion of said concrete pipe section so as to uncover the desired groove in said pipe section; and

f. discarding said disposable ring thus removed from the cured pipe section, said ring not being employed in the formation of spigot grooves in subsequently produced concrete pipe sections,

whereby the likelihood of groove damage caused by the removal of a metallic snap ring from the pipe section in its relatively green state prior to complete curing is avoided, the necessity for cleaning and transporting such a metallic or other reusable snap ring back from the curing yard to the pipe manufacturing location for reuse with a particular pallet-header combination is entirely obviated, and the groove in the spigot portion of the pipe section may be kept free of grit, dirt, grease and other foreign matter by said disposable ring upto the time said section is used in the installation of a line of concrete pipe.

2. The process of claim 1 in which said pipe section has an internal diameter of from about 6 inches to about 24 inches, said concrete pipe section being completely cured before said disposable ring is removed from the spigot portion thereof.

3. The process of claim 1 in which said non-metallic disposable ring comprises a paper ring.

4. The process of claim 3 in which said paper ring is oil-treated to improve its moisture resistance.

5. The process of claim 1 in which said non-metallic disposable ring comprises a plastic ring.

6. The process of claim 1 in which said non-metallic disposable ring comprises a rubber ring.

7. The process of claim 1 in which said disposable ring is attached to the inner surface of said header section by positioning a mechanical catch on said surface on the underside of said disposable ring to prevent said ring from falling from its pre-determined position on the inner surface of said header.

8. The process of claim 1 in which said disposable ring comprisesa liquid absorbent material and including soaking the ring in said liquid prior to placing the ring in its desired position on the header, the wet ring tending to swell in position so as to provide a tight fit on the inner surface of the header.

9. The process of claim 8 in which said liquid is water.

10. The process of claim 1 in which said disposable ring has a rectangular cross-sectional area.

11. The process of claim 1 in which said disposable ring has a trapezoidal cross-sectional area.

12. A process for forming a groove in the spigot portion of a concrete pipe section comprising:

a. attaching a non-metallic disposable ring to the inner, pipe-contacting surface of the pallet section of a pipe-making form, said ring having a rigid nature and comprising a heat, water, alkali and steam resistant material conforming in size and position on said pallet section to the desired size and portion of the groove in the spigot portion of said concrete pipe section;

b. forming said concrete pipe section with its bell end up, with its spigot end down and in contact with the inner surface of said pallet section;

0. subjecting said concrete pipe section to heat treatment while in its pipe-making form with the disposable ring in its predetermined position on the inner surface of said pallet section;

d. removing the header section and the pallet section of the pipe-making form from said heat-treated concrete pipe section prior to the curing of said pipe section beyond the green state while retaining said disposable ring in groove-defining position on the surface of said pipe section;

f. discarding said disposable ring thus removed from 1 the cured pipe section, said ring not being employed in the formation of spigot grooves in subsequently produced concrete pipe sections,

whereby the likelihood of groove damage caused by the removal of a metallic snap ring from the pipe section while said section is in its relatively green state prior to complete curing is avoided, the necessity for cleaning and transporting such a metallic or other reusable snap ring back from the curing yard to the pipe manufacturing location for reuse with a particular pallet-header combination is entirely obviated, and the groove in the spigot portion of the pipe section may be kept free of grit, dirt, grease and other foreign matter by said disposable ring up to the time said section is used in the installation of a line of concrete pipe.

13. The process of claim 12 in which said ring comprises a paper ring, said concrete pipe section being completely cured before said disposable ring is removed from the spigot portion thereof.

14. The process of claim 12 in which said ring comprises a plastic ring.

15. The process of claim 12 in which said ring comprises a rubber ring.

16. The process of claim 12 in which said disposable ring has a rectangular cross-sectional area.

17. The process of claim 12 in which said ring has a trapezoidal cross-sectional area.

Claims

1. A process for forming a groove in the spigot portion of a concrete pipe section comprising: a. attaching a non-metallic disposable ring to the inner, pipecontacting surface of the header section of a pipe-making form, said ring having a rigid nature and comprising a heat, water, alkali and steam resistant material conforming in size and position on said header to the desired size and position of the groove in the spigot portion of said pipe section; b. forming said concrete pipe section with its spigot end up and in contact with the inner surface of said header section; c. subjecting said concrete pipe section to heat treatment wHile in its pipe-making form with the disposable ring in its predetermined position on the inner surface of said header; d. removing said header and the pallet section of the pipemaking form from said heat-treated concrete pipe section prior to the curing of said pipe section beyond the green state while retaining said disposable ring in groove-defining position on the surface of said pipe section; e. curing said pipe section beyond the green state and thereafter removing said disposable ring from the spigot portion of said concrete pipe section so as to uncover the desired groove in said pipe section; and f. discarding said disposable ring thus removed from the cured pipe section, said ring not being employed in the formation of spigot grooves in subsequently produced concrete pipe sections, whereby the likelihood of groove damage caused by the removal of a metallic snap ring from the pipe section in its relatively green state prior to complete curing is avoided, the necessity for cleaning and transporting such a metallic or other reusable snap ring back from the curing yard to the pipe manufacturing location for reuse with a particular pallet-header combination is entirely obviated, and the groove in the spigot portion of the pipe section may be kept free of grit, dirt, grease and other foreign matter by said disposable ring up to the time said section is used in the installation of a line of concrete pipe.

8. The process of claim 1 in which said disposable ring comprises a liquid absorbent material and including soaking the ring in said liquid prior to placing the ring in its desired position on the header, the wet ring tending to swell in position so as to provide a tight fit on the inner surface of the header.

9. The process of claim 8 in which said liquid is water.

12. A process for forming a groove in the spigot portion of a concrete pipe section comprising: a. attaching a non-metallic disposable ring to the inner, pipe-contacting surface of the pallet section of a pipe-making form, said ring having a rigid nature and comprising a heat, water, alkali and steam resistant material conforming in size and position on said pallet section to the desired size and portion of the groove in the spigot portion of said concrete pipe section; b. forming said concrete pipe section with its bell end up, with its spigot end down and in contact with the inner surface of said pallet section; c. subjecting said concrete pipe section to heat treatment while in its pipe-making form with the disposable ring in its predetermined position on the inner surface of said pallet section; d. removing the header section and the pallet section of the pipe-making form from said heat-treated concrete pipe section prior to the curing of said pipe section beyond the green state while retaining said disposable ring in groove-defininG position on the surface of said pipe section; e. curing said pipe section beyond the green state and thereafter removing said disposable ring from the spigot portion of said concrete pipe section so as to uncover the desired groove in said pipe section; and f. discarding said disposable ring thus removed from the cured pipe section, said ring not being employed in the formation of spigot grooves in subsequently produced concrete pipe sections, whereby the likelihood of groove damage caused by the removal of a metallic snap ring from the pipe section while said section is in its relatively green state prior to complete curing is avoided, the necessity for cleaning and transporting such a metallic or other reusable snap ring back from the curing yard to the pipe manufacturing location for reuse with a particular pallet-header combination is entirely obviated, and the groove in the spigot portion of the pipe section may be kept free of grit, dirt, grease and other foreign matter by said disposable ring up to the time said section is used in the installation of a line of concrete pipe.

14. The process of claim 12 in which said ring comprises a plastic ring.

15. The process of claim 12 in which said ring comprises a rubber ring.