(1) Field of the Invention
This invention relates to a method of and apparatus for lining pipes. More particularly, the invention relates to such a method and apparatus for lining pipes with settable materials, e.g. pastes, aggregates, jells, settable liquids, and the like.
(2) Description of the Related Art
It is often desirable to line pipes made of metal or plastics with a material that is resistant to attack by products conveyed through the pipes and/or that provides heat or electrical insulation, or the like. For example, pipes are often lined with concrete or refractory ceramic products so that they may convey fluids, such as molten metals, caustic liquids, hot gases and the like, that would destroy unlined pipes. Current lining methods employ fixed forms inserted into the pipes so that concrete or other material that can be chemically or thermally set may be introduced between the interior of the pipes and the forms. After the material has set to produce a solid lining, the forms must be removed. This is a time-consuming operation that is made more difficult if the pipe has a complex geometry. It would therefore be desirable to provide a more simple, rapid and adaptable way of providing pipes with linings of this kind.
U.S. Pat. No. 5,779,948 which issued to Perkins et al. on Jul. 14, 1998 discloses a method of lining a pipeline using a constant extrusion pressure.
U.S. Pat. No. 4,764,237 which issued to Shishkin et al. on Aug. 16, 1988 discloses a method of and apparatus for coating the internal surface of a pipeline with a cement-sand mortar. In
U.S. Pat. No. 5,246,641 which issued to Perkins et al. on Sep. 21, 1993 also refers to a method of lining a pipe with cement mortar. The prior art arrangement shown in
An exemplary embodiment of the invention provides a form for producing a lining in a pipe. The form comprises a body having a leading part and a trailing part, a hole in a leading side of the leading part and a channel in the body communicating with the hole. The body has a diameter at the leading part that is greater than the diameter of the trailing part. The channel has at least one peripheral opening situated rearwardly of the leading part of the form at a position to discharge lining material from the channel around the trailing part of the form, and a supply tube, or an attachment on the leading side for a supply tube, for supplying flowable settable lining material to and through the hole.
Preferably, the leading side of the leading part has an attachment for an elongated pulling element, which may be the same as the attachment for the supply tube when the supply tube is to be used to pull the form through a tube.
The leading part of the form preferably has a concave trailing surface and the trailing part has a convex leading surface. These surfaces are preferably both frusto-conical and are preferably separated by a gap forming the channel in the body, and are preferably partially nested together. The peripheral opening for the lining material may then be formed by the periphery of the gap between the two parts. The leading part and said trailing part may be joined together by one or more rigid struts.
The leading part of the form preferably has a flexible edge region adjacent a radially outer periphery thereof. This edge region contacts the inner surface of a pipe to be coated. The trailing part of the form preferably has a skirt extending rearwardly from a leading surface of this part. This skirt contacts the lining material, shapes it into a layer and forces it against the inner surface of the pipe. The skirt preferably has a region adjacent to the leading surface that slopes away from a central axis of the form in the rearward direction, followed by a region that slopes towards the central axis in the rearward direction. This causes the skirt to compress the layer of lining material as it is applied, and then allows the form to break contact with the lining layer without disturbing the newly formed surface of the layer.
The trailing part of the form preferably has a hollow interior and houses apparatus for modifying lining material. This apparatus may include a manifold for delivering a liquid to a plurality of holes extending from the hollow interior to an exterior of the trailing part, a vibrator for compacting lining material as it is applied to the interior of a pipe, and a heater for heating lining material as it is applied.
The form preferably has guides extending radially from the trailing part positioned to cause the form to be centered within a pipe having an inner diameter corresponding to the diameter of the leading part.
Another exemplary embodiment provides a form for lining an interior of a pipe, comprising a material feeder part and a material applicator part axially aligned and joined together with a gap there-between. The material feeder part has an outer periphery, a leading wall extending to the outer periphery, an opening in the leading wall communicating with the gap. The material feeder part also has a trailing wall adjacent the gap extending from the opening to the outer periphery of the material feeder part. The material applicator part comprises a body having a leading wall terminating at a peripheral edge and a peripheral skirt extending axially of the body rearwardly from the peripheral edge of the leading wall, the leading wall sloping rearwardly and outwardly from a central region to the peripheral edge. The periphery of the material feeder part extends by a greater radial distance than the peripheral edge and peripheral skirt of the material applicator part.
Another exemplary embodiment provides a method of lining a pipe. The method comprises supplying a flowable settable lining material to a leading end of a lining form through a tube passing through the pipe, and pulling the form through the tube by pulling the tube as lining material is supplied thereto. Preferably, the form has the elements as described above.
As noted above, in some exemplary embodiments, the tube used to supply the form with lining material is used to pull the form through the pipe during a lining operation. This is preferred in many cases because it simplifies the design of the form. However, it is alternatively possible to use a separate element, e.g. a string, rope or cable, to pull the form through the pipe so that no tension is exerted onto the tube supplying the lining material. However, the attachment of such an element should preferably be such that the form is pulled through the pipe without causing any tendency of the form to twist or slew under pulling forces imposed by such an element. The element should therefore preferably be attached at several points arranged symmetrically around the central longitudinal axis of the form. The elongated pulling element, whether the supply tube or a separate element, may be wound onto the drum of a winch turned by an engine at a speed appropriate for the lining operation, i.e. a speed that allows the lining to be formed without defects and that allows the lining material to harden, cure or jell sufficiently to hold its shape before losing contact with the form. The speed or pressure at which the lining material is supplied to the form depends on the properties of the lining material. The lining materials are often of high viscosity, so pumps of large capacity capable of producing high pressures (e.g. typical cement pumps) may be required in many cases. If the supply tube is used to pull the form through the pipe by being wound on a drum, it is preferable to avoid forming multiple overlying wraps on the drum to avoid the possibility of constricting the supply tube.
Lined pipes produced by the exemplary embodiments may be used for many and varied applications. For example, without limitation, metal pipes may be provided with ceramic linings so that molten metal or caustic products can be pumped or siphoned therethrough without damage and/or without undue loss of heat. Moreover, furnace exhaust stacks and hot combustion air ducting may be provided with ceramic linings, again to avoid corrosion and to reduce heat losses. Pipes with non-ceramic linings may also be produced, e.g. pneumatic conveying and slurry pipes lined with a rubber compound or a reinforced polymer coating.
It should be noted that terms such as “front”, “leading”, “rear”, etc. as used herein to describe parts of the form refer to the direction in which the form is moved through a pipe during a pipe lining operation. That is to say, a leading or front part or surface is one that leads as the form is pulled through a pipe, etc.
Exemplary embodiments of the invention are described in detail in the following with reference to the accompanying drawings, in which:
A first exemplary embodiment of the present invention is shown in
The leading material feeder part 12 has a central axial hole 20 in leading surface 21 and is made of two nested hollow frusto-conical elements, i.e. an inner element 22 and an outer element 23, that are nested together without any intervening gap or opening between the overlapping parts thereof. These elements are preferably adhered to each other at the overlapping parts with a suitable adhesive, or are otherwise mutually permanently attached. The outer element 23 is preferably made of a rigid material (e.g. metal, ceramics or dense plastics, wood, etc.) and the inner element 22, which extends to a radially outermost periphery 17 of the leading material feeder part 12, is preferably made of a tough but flexible resilient or elastic material that yields when acted on by a force, e.g. leather or a reinforced elastomer such as urethane rubber. If desired, instead of providing two frusto-conical elements 22 and 23 nested together as shown, the material feeder part may be made of just one frusto-conical element 23 provided with an outer edge made of suitably flexible material or that is itself made entirely of suitable flexible (but still quite stiff) material. In such a case, the element 23 is provided with dimensions equivalent to those of the combined elements 22 and 23 of the illustrated embodiment, i.e. extending to the position of outermost periphery 17.
The leading surface 18 of the trailing bullet-shaped material applicator part 14 of the form 10 is frusto-conical (conically convex) in shape and it slopes outwardly from a central flat circular leading end 25 to an outer peripheral edge 26. Extending rearwardly from the peripheral edge 26 is a generally (but preferably not exactly) cylindrical skirt 27. The material applicator part 14 has a hollow interior 28 that is open at a rear end wall 29, although in other embodiments the material applicator part may be solid throughout. Also in other embodiments, the leading surface 18 may come to a sharp or rounded point rather than terminating in the flat disc 25 as shown, provided that flow areas are maintained large enough to prevent poor distribution of lining material and to avoid high pressure drops within the form.
The material applicator part 14 of the form has preferably three pairs of radially projecting rigid guides 30 preferably arranged at equal spacings (i.e. separated by120°) around the circumference of the applicator part. The positions of these guides may be axially aligned with the struts 15 of the spider, or may be offset angularly relative to those struts. The guides 30 extend radially to a distance from the center of the form 10 approximately the same as that of the periphery 17 of the material feeder part 14, and are used to center the form within a pipe, as will be described later. The material applicator part 14, including guides 30, is preferably made of an unyielding material such as metal, ceramics, dense plastics or wood, and may have an outer coating (not shown) that reduces friction with and adhesion to the coating material or, in the case of guides 30, the pipe 11.
As shown in
As shown in
The interior of the applicator part 14 is further provided with a channel member 60 fixed to the inner wall of the applicator part that acts as a manifold to supply a liquid curing agent 61 to a series of small holes 62 (see
The leading material feeder part 12 has an outer diameter at periphery 17 that is the same as, or slightly larger than, the internal diameter of pipe 11 to be lined. The trailing material applicator part 14 has a maximum diameter that is less than the internal diameter of the pipe 11 by an amount corresponding to twice the thickness of a lining 45 to be produced.
As noted, and as shown in
Referring again to
The narrow leading end of the material applicator part 14 of the form forces the lining material 42, as it enters the form 10 from the tube 40, towards the inner surface 43 of the pipe and this flow of material is also guided by the rear surface 19 of the material feeder part 12. The lining material flows around struts 15, but any gap or cut in the layer of lining material caused by the struts is closed by the pressure applied by the leading surface 18 of the material applicator part 14. The periphery 17 of the inner frusto-conical element 22 is dimensioned to bear with slight pressure against the inner surface 43 of the pipe 11 so that lining material cannot pass around the form in the upstream direction. Since this element is flexible, it yields resiliently if it encounters any uneven contours of, or projections from, the inner surface of the pipe. The pressure of the lining material in the form 10 and/or the elastic properties of the element 22, keep the periphery 17 in contact with the inner surface, even after encountering such surface irregularities.
The guides 30 are also dimensioned to lightly contact the interior surface 43 of the pipe 11 to center the form 10 within the pipe. The lining material must also flow around these guides, but any cut or gap thereby formed in the layer of lining material is closed because of the slight outward taper of the circumferential region 32 of the material applicator part 14 (
If necessary, liquid curing agent 61 may be supplied to the lining material 42 via holes 62 formed in the trailing part 14 as the material flows past these holes. The curing agent is fed to the holes under pressure via channel member 60 and tube 63. The lining material may also be compacted by operating the vibrator 51 that slightly shakes the form 10 as the material is being applied. Also, the material may be heated to help it to solidify and cure by operating the electrical heating coils 55 positioned within the material applicator part 14 of the form 10.
The exemplary embodiments, while able to line pipes of almost any diameter, are most useful when used with pipes having diameters that are generally too small for traditional lining methods, e.g. from about 3 inches to about 3 feet (preferably 6 to 12 inches). The thicknesses of the resulting linings may be, for example, from 0.25 to 12 inches, more preferably 1 to 4 inches, and even more preferably 1 to 1.5 inches. Optimally, the cross-sectional area of the tube 40 is made the same as, or similar to, the circumferential cross-sectional area of gap 16 (and thereby the cross-sectional area of the lining layer 45), as there is then no over- or under-supply of lining material to the form that could result in the production of a linings having regions of reduced or uneven thickness. The pipes lined in this way may be of any length, but lengths of 10 to 50 feet are usual.
While the exemplary embodiments are preferably employed for producing pre-lined lengths of pipe for use in subsequent manufacture of equipment, the embodiments may also be used for lining pipes or pipelines in situ, e.g. for sealing cracked or leaking sections of pipe by the application of an internal lining of sealant material.
As noted above, the lining material may be a kind of concrete, e.g. a mixture of aggregates and binders that set thermally or chemically to produce a rigid layer, or any other ceramic refractory material, or any settable paste or semi-solid material. Shotcrete® is an example of a ceramic lining material that may be employed. This consists of a dispersion of metal oxides (e.g. oxides of silica, alumina, titanium and calcium, among others) in an aqueous liquid. Other examples of lining materials include glass-filled polyester resin used with a hardener supplied as the liquid curing agent, or rubber-filled polyester or epoxy resin, again using a hardener supplied as the liquid curing agent.
The apparatus shown in
In this exemplary embodiment, the leading part 12 of the form 10 is in the shape of a flat plate 70 having a peripheral edge 71 made of a flexible material. A lining material supply tube 40 is attached to the leading surface 18 of the leading part 12 in communication with a central hole 20 that communicates with the gap 16 having a peripheral opening 16A immediately adjacent to the trailing side of the flat plate 70. The form 10 is pulled in the direction of arrow A as lining material 42 is forced under pressure in the direction of arrow B. Since the lining material 42 is quite fluid, it readily flows through the tube 40, into and through the gap 16, to the periphery of the second part 14 of the form, and thereby lines the inner surface 43 of the pipe as in the previous embodiment. Although the material 42 is quite fluid, it preferably contains (or is supplied with) a curing agent or hardener so that it is able to support itself as a lining for the pipe before losing contact with the form 10. The axial length of the trailing part 14 may be varied according to the ability of the lining material to become self-supporting. That is to say, of the lining material sets quickly, the trailing part 14 may be quite short, but if the lining material is slow to set, the trailing part 14 may be made longer to provide support for a longer period of time. In general, the trailing part should be kept as short as possible to reduce friction and to allow the form to follow contours within the pipe without causing undue variations in the thickness of the lining and without becoming jammed.
A variant of this alternative embodiment (not shown) has a single piece body very similar to the form of
Other design variations and embodiments are possible within the scope of the following claims.
This application claims the priority right of co-pending U.S. provisional application Ser. No. 61/277,806 filed Sep. 30, 2009 by applicants named herein. The disclosure of U.S. provisional application Ser. No. 61/277,806 is specifically incorporated herein by this reference.
Number | Date | Country | |
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61277806 | Sep 2009 | US |