Process and equipment for lining concrete pipes

Abstract: This invention relates to a process and relative equipment for lining concrete pipes (1), particularly pipes for sewer systems. The object of this lining, consisting of bisphenolic, isophthalic or similar resin, which impregnate a layer (2) of single thread glass fibre cloth and antiacidic cloth, is to protect the pipe from corrosive acidic agents, including the socket connections between one section of the pipe and the next.

Description: This invention relates to a process and the relative equipment by which turbocentrifuged or vibrated concrete pipes can be lined with single thread glass fibre and anti-acid cloth impregnated with isophthalic bisphenolic resins and the like, the said pipes being traditionally used for carrying sewage or other highly acid substances and for irrigation and pressurised water pipelines. It is known that pipes and headers in turbocentrifuged radially prestressed concrete or vibrated concrete are used to construct pipelines for sewage or acidic liquids. These pipes are connected to male-female sockets and a layer of tarry material is usually applied on the inside with the aim of protecting the bed on which the sewage flows from the corrosive agents contained in the sewage and, above all, protecting the pipe from the corrosion caused by the highly acidic fumes and vapours which are generated inside the pipes which are generally buried at a certain depth. Obviously, these pipes are irremediably damaged after a certain time and have to be replaced, which is a very expensive operation. Document DE-A- 3 002 231 discloses a concrete pipe comprising a lining of synthetic resins, but this document does not disclose any method or apparatus to make in practice such a pipe. Therefore there is a need of a practical, efficient and reliable process and equipment for producing this type of pipes. These problems are solved by the process of independent Claim 1 and the equipment of independent Claim 4. Further advantageous features are recited in dependent Claims 2-3 and 5-8, respectively. According to this invention each section of pipe is lined in advance with a layer of glass fibre and anti-acid cloth impregnated with bisphenolic resin or a similar substance. In practice, this lining is effected by means of a tubular metal element inserted in the pipe of concrete, having an internal diameter which permits the element to carry a layer of lining of the thickness required for the lining of the pipe. Subsequently, the lining is impregnated by the injection of bisphenolic resins which solidify in the air, leaving a perfectly smooth surface which provides maximum protection against acids and facilitates the flow of the liquid, almost totally eliminating decantation of the liquid. These and other characteristics are explained more clearly in the following detailed description which is a purely non-limiting example of the scope of the invention, and from the various figures of the attached illustrative drawings, in which: Figure 1 shows a side view of a section of concrete pipe traditionally used for the construction of sewage or acid liquid pipelines; Figure 2 shows a highly enlarged cross section of the profile of the two ends of an element of sewer piping, showing the socket coupling between one section and the next; Figure 3 shows a perspective view of the die, showing the elements which compose the anti-acid lining, applied on the outside by binding; Figure 4 shows an enlarged detail of the die, showing the sector which moves on an inclined plane having the function of expanding and contracting the die internally to permit the detachment and uncoupling after the resins which have been injected have dried; Figure 5 shows a complete side view of a pipe prepared for the injection of bisphenolic resin; Figure 6 shows a complete perspective view of a section of piping line according to the process in question; Figure 7 shows a schematic cross section of a coupling of two concrete pipes lined according to this invention; Figure 8 shows a schematic cross section demonstrating a detail of the male flanging used for the lining of the pipe header, according to a variant of the invention; Figure 9 shows a cross sectional view demonstrating a detail of the female flanging used for the lining of the socket header of the pipe, according to a variant of the invention; and Figure 10 shows a view of an assembly in cross section, demonstrating the coupling between two pipes whose headers have been lined by means of the flanging, cited as variants to this invention and shown separately in figures 8 and 9. Referring to the various figures of the attached drawings, the process in question provides for lining in advance of the pipes 1 in turbocentrifuged or vibrated concrete with a layer 2 of glass fibre impregnated with bisphenolic resin or a similar substance. In addition to the inside walls 3, the lining will also extend to an external portion 4 of the male end 5 of the pipe and to the whole of the coupling seat 6 of the female flanging 7, including a small front circumferential portion 8. This also provides protection for the seat 9 of the gasket 10 inside the flanged socket and the surrounding area which is notoriously subject to damage because of leakages of sewage and acidic gases. In practice, a specific equipment 11 is used consisting of a tubular element 12 equipped with a mobile sector 13 operating between two inclined plane shoulders 14, acting as an expander which presses the glass fibre lining 2 uniformly against the internal walls of the concrete pipe 1 before and during the injection of the bisphenolic resins and, subsequently, permits the detachment of the tubular element from the joint and its withdrawal when the lining has dried. The said die comprises two mobile flanging 15, 16 which will butt on the female flanged part 6 and the male end 5 of the concrete pipe. The female flanging 15 also has the connections 17 for the injection of the bisphenolic resins and has an internal profile which is the reverse of the socket seat of the concrete pipe. In operational terms, the die tube is prepared with a layer of binding 18 in anti-acid glass cloth 19, a layer of glass fibre 20, a pad and a final layer of glass cloth 21. When this has been done, the die is inserted in the concrete pipe 1, counterflanged and after being correctly bedded and locked into position, bisphenolic resins or similar substances are injected enbloc. After solidification, the longitudinal mobile sector 13 is released and the male counterflange is disconnected and the die is withdrawn. When the process has been completed, the pipe has been provided with a lining 2 on the inside and on the headers of a given thickness which is extremely compact and smooth and is resistent to any acid agent. According to a variant to this invention and referring to figures 8, 9 and 10, to provide a lining which is even more uniform in thickness and to avoid any leakage of the resin from the headers during injection at high pressure, special male 22 and female 23 flanges are used which reproduce the profile of the headers 5, 6 themselves and which have two circumferential gaskets 24 in order to obtain a perfect seal with the internal tubular die. This also permits an improved profiling of the male and female terminal parts of the pipe lining to be obtained, guaranteeing that they fit together better with the extra aid of a perimetral gasket 10 inserted in a special seat 9 around the circumference of the pipes, as is provided for in the basic solution of this invention. In addition, in this particular case, the tubes for the injection of the bisphenolic resin in the space between the concrete pipe and the die are located in the internal tubular element and not on the flanging of the headers. The preceding detailed description makes it clear that this invention is the right solution to provide long lasting and resistant linings for concrete pipes for the construction of pipelines for sewers or highly acidic liquids.

Claims: Process for lining concrete pipes having a male end and a female flanged part, comprising the steps of: preparing a glass wool lining; applying it around a tubular element; said tubular element acting as a support for said lining and as a die for a subsequent injection of a bisphenolic or isophthalic resin; said tubular element being equipped with a longitudinal mobile sector operating between two inclined plane shoulders acting as an expander which presses the glass wool lining uniformly against the internal wall of the concrete pipe before and during the injection of the resins and subsequently allows the detachment of the tubular element from the pipe and its withdrawal when the lining has dried; said tubular element being also provided with two mobile flangings which will butt on the female flanged part and the male end of the concrete pipe, respectively; the female flanging having connections for the injection of the resins and an internal profile which is the reverse of the socket seat of the concrete pipe; inserting the tubular element into the concrete pipe; counterflanging, correctly positioning and locking the tubular element in the concrete pipe; injecting enbloc the resins; after solidification, releasing the longitudinal mobile sector, disconnecting the flangings and withdrawing the tubular element from the finished pipe. Process according to claim 1, characterised in that the said lining (18) consists of an anti-acid cloth (19), a pad of glass wool (20) and a second anti-acid cloth (21) which can subsequently be impregnated with a bisphenolic or isophthalic resin, in order to form a protective layer which is resistent to any type of acid agent. Process according to claim 1, characterised in that the said tubular die element also has two flanged headers designed to act as counter-rabbets so that the seats of the male-female connections of the pipe can be lined en bloc. Equipment (11) for lining concrete pipes (1) having a male end (5) and a female flanged part (6), with a glass wool lining and a subsequent injection of a bisphenolic or isophthalic resin, comprising a tubular element (12) equipped with a longitudianl mobile sector (13) operating between two inclined plane shoulders (14), acting as an expander which presses the glass wool lining (2) uniformly against the internal wall of the concrete pipe (1) before and during the injection of the resins, and subsequently allows the detachment of the tubular element (12) from the pipe and its withdrawal when the lining has dried; said tubular element (12) being also provided with two-mobile flanges (15, 16) which will butt on the female flanged part (6) and the male end (5) of the concrete pipe (1), respectively; the female flange (15) having connections (17) for the injection of the resins and an internal profile which is the reverse of the socket seat of the concrete pipe. Equipment according to Claim 4, characterised in that the mobile flange (15) allows that also the circumferential seat (9) for the socket connection provided with a gasket (10), be lined with the glass fibre reinforced resin, in order to avoid leakage of acidic liquid. Equipment according to claim 4, characterised in that the header flanges (22, 23) have a profile which enables a frontal rabbet connection with the internal tubular die element (12) in order to obtain a better male-female (5,6) connection profile between the various pipe sections. Equipment according to claim 6, characterised in that the said flanging (22, 23) also comprises two circumferential gaskets (24) which respectively butt in the internal tubular die element (12) and the external part of the pipe (1), in order to obtain maximum seal against the leakage of the resin during injection under high pressure.

Inventors: BOSISIO SERGIO, BOSISIO, SERGIO
Applicants: ASSOTUBI ECOLOGICA SRL, ASSOTUBI ECOLOGICA S.R.L.
Application year: 1990
Main classification: F16L58
IPC codes: F16L58, B28B21