GB1564615A - Abrasionresistant lined pipe and method of making it - Google Patents

Description

(54) ABRASION-RESISTANT LINED PIPE AND METHOD OF MAKING IT (71) We, REXNORD INC., a corporation organized and existing under the laws of the State of Wisconsin, United States of America, of 4701 West Greenfield Avenue, Milwaukee, Wisconsin, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention is concerned with a wear-resistant lined pipe which is basically intended to be used for the transmission of an abrasive medium such as coal slurry.

According to the invention, a method of lining the inside of a pipe to increase its resistance to wear includes the steps of disposing the pipe about a generally horizontal axis and in a state to be rotated, providing a cross-linkable thermosetting resin and a separate curing agent for the resin, rotating the pipe about its horizontal axis at a rate of speed that will centrifuge a lining about the inside thereof, transporting the resin and the curing agent separately along the inside of the pipe out of contact therewith towards a zone of initial application within the pipe and adjacent one end of the pipe, mixing the resin and curing agent at a point of mixture inside the pipe to form a base substance, applying the base substance progressively along the inside of the pipe (whilst the pipe is being rotated) commencing at said zone of initial application adjacent one end of the pipe and moving along the piPe towards its other end whereby to progressively form a layer of base substance on the inside of the pipe, adding to the base substance already on the pipe (commencing during application of the base substance) abrasion resistant particles which are applied at a zone spaced behind the zone of application of the base substance to thereby apply a uniform deposit of particles progressively to the base substance on the inner surface thereof, and allowing the mixture of base substance and particles to cure and adhere to the inner surface of the pipe to form a finished lined pipe product.

The invention also extends to a generally circular cross-section pipe with a lining adhering to its inside surface and manufactured by the above method, the lining being resistant to wear by an abrasive medium such as coal slurry and comprising larger abrasion resistant particles of a size between 8 and 36 mesh dispersed in a base substance including a cured cross-linked thermosetting resin, and smaller abrasion resistant particles of a size between 100 and 225 mesh dispersed in the resin among the larger particles.

In one embodiment of pipe according to the invention the smaller abrasion resistant particles are of substantially 180 mesh size, and the larger abrasion resistant particles are substantially 1/16th inch in their largest dimension.

In another embodiment of pipe, the smaller abrasion resistant particles are substantially 100 mesh size, and the larger abrasion resistant particles are substantially 1/16th inch in their largest dimension.

In a further example the smaller abrasion resistant particles are of substantially 180 mesh size, and the larger abrasion resistant particles are substantially 1/32nd inch in their largest dimension.

In another embodiment of pipe, the smaller abrasion resistant particles are of substantially 180 mesh size, and the said abrasion resistant particles are substantially 1/12th inch in their largest dimension.

An example of a pipe in accordance with the invention is shown in the accompanying drawing, in which: Figure 1 is a perspective of the pipe; Figure 2 is an axial section, with parts in full, through the pipe, schematically illustrating the method of making it; Figure 3 is an end view of the pipe, from the left in Figure 2; and Figure 4 is an enlarged section of a segment of the pipe.

The pipe 10 shown in the drawing, has an interior lining 12. The pipe may be of metal, such as steel, aluminium, copper, brass, bronze or cast iron, or it may be of a synthetic plastics material, for example a fibre glass reinforced polymer, or of concrete. The lining 12 comprises a resin substance with wear-resistant particles embedded therein as explained in detail below.

The process of lining the pipe includes disposing the pipe itself, whatever its material or composition, in a generally horizontal plane and rotating it about its longitudinal axis so that lining material is applied or distributed around the inside by centrifugal force, as schematically indicated in Figure 2. In Figure 2 and end caps 14 are shown diagrammatically positioned on the ends of the pipe to provide circumferential dams at each side so that the lining material and its various ingredients will not flow out one end or the other. The lip or dam on these caps or rings can be of any suitable radial extent. A lining-applying instrument is indicated diagrammatically at 16, and its construction will be explained in detail below.

The lining itself is made up of a base substance or bonding agent of a polymer such as, for example, an epoxide polymer, unsaturated polyester (carboxylate-glycol adduct), a polyurethane, a polyamlde or polyimide resin or the like. A particular polymer found to function particularly well as the base substance is an epoxy resin. Polyepoxides having an epoxy equivalent weight of between 140 and 525 e.g. between 170 and 290 are preferred.

Polyepoxides having an average molecular weight below 1,200 (e.g. between 280 and 900) are also preferred. They also have a functionality (i.e. ratio of molecular weight to epoxy equivalency) of at least one, preferably between 1.5 and 3.0. Suitable polyepoxides are polyepoxides formed from an epihalohydrin (for example epichlorhydrin) and a polyhydric compound e.g. bisphenol A (2,2-bis (4-hydroxyphenyl) propane) or glycerol. The preferred polyepoxide prepared by the reaction of an epihalohydrin e.g. epichlorohydrin with diphenylolpropane (bisphenol A) which has an epoxy equivalent weight of between 175 and 210, an average molecular weight of between 350 and 400 and an OH equivalency of about 1250. A thixotropic agent such as asbestos may be included to vary the fluidity or viscosity of the base substance.

The base substance is indicated generally at 18 in Figure 4 and has embedded in it two sizes of particles, i.e. smaller particles 20, and larger particles 22 which peform a primary abrasion resistant function.

The smaller particles 20 are substantially smaller than the larger particles 22. The smaller particles are randomly dispersed in and among the larger particles in the base substance so that they will fill the voids or interstices between the larger particles. Their basic function is to protect the base substance from wear between the adjacent larger particles so that the larger particles will not be undermined by the base substance being eroded between them.

The smaller particles protect the base substance and, in turn, stabilize the larger particles which perform the major or primary wear resisting function.

The smaller particles may comprise silicon carbide of substantially 180 mesh which functions particularly well in the wear-resistant lining for the pipe. Other smaller particles may be used and they should have a hardness at least as hard as the material that is being handled by the pipe. For example, they might be boron carbide, boron nitride, tungsten carbide, alumina ceramic, silica sand. taconite, technical grade or industrial diamond dust.

It has been found that 180 mesh size is desirable, but in certain situations the mesh size can range from 225 to 100 mesh.

The larger abrasion resistant particles 22 can take different forms. For example, they might be alumina oxide, boron carbide, silicon carbide, technical grade or industrial diamond, a metal coated alumina ceramic particles of the type sold by Coors Porcelain Company of Golden, Colorado, United States of America, under the trademark "METLX" which is a high alumina (90% type) ceramic spherical bead which has very fine grain (crystal) boundaries to give good abrasion resistance with a coating of metal on the surface thereof. Broadly, all such particles may be considered to be a ceramic or refractory.

Instead of a bead. it may be in chip form. In any event, the larger abrasion resistant particles should be of a size nominally 1/16" and may be considered to be a 12 mesh chip, but will function properly in certain applications in the range of from 36 to 8 mesh.

The base substance formula may be modified to include CTBN or ATBN rubber or bromine terminated polybutadiene to improve impact.

A specific example of a suitable composition for use in pipe lining may be: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80.00 Asbestos 9.50 Fumed Silica 0.45 180.95 Hardener Component Parts by Weight Polyamine 37-610, Reichhold Chemicals, Inc. 7.82 Polyamine 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2341, Union Camp Corporation 13.81 Titanium Dioxide 1.40 34.04 Larger Particle Component Parts by Weight Aluminium Oxide Chips, 12 mesh 350.2 In the examples shown the formulation is a three-component mixture with the resin component including the smaller particles of silicon carbide being supplied through a tube or pipe 24 and the hardener component through an adjacent tube or pipe 26, both of which lead to a mixing head 28 of any suitable type where the two are thoroughly intermixed inside of the rotating pipe and the mixture discharged, as at 30, in a stream or free fall on the inner surface of the rotating pipe. It will be understood that the tubes and mixing head move axially with respect to the pipe and are supported by rollers 31 so that a smooth even coat is applied along the inner surface of the pipe. The mixing head 28 may move from right to left in Figure 2, as indicated by the arrow at the ends of the tubes 24 and 26, or the pipe 10 may move from left to right. Alternatively, both the head and the pipe may move.

The resin and curing components are thoroughly intermixed so that the smaller particles (included in the resin component) completely permeate the base substance as it is applied along the inner surface of the pipe.

A third tube or conveyor 32 supplies the third component, i.e. the larger particles, and it will be noted that the point of introduction of the larger particles is spaced somewhat from the point where the base substance is deposited. Assuming that the mechanism 16 moves from right to left in Figure 2, the base substance stream 30 will be applied first and, after an interval, the larger particle stream 34 will deposit the large particles on the already curing base substance which will be of a certain viscosity or liquidity such that the larger particles will embed themselves in the base substance in random fashion and under the centrifugal force from the rotating pipe they will arrive at an intermediate position within the layer.

The larger particles, when freed on the inner surface of the already applied base substance, have the ability or characteristic of seeking an open or unoccupied place between other such particles that have already embedded themselves or found their position, so to speak, and the result will be that the dispersion of the larger particles in the wear-resistant base substance will be unusually uniform without any bunching or clustering.

As shown in Figure 4, more than one layer may be applied. for example, a primary layer 36 may be initially applied with the larger particles embedding themselves therein and allowed to fully cure. Thereafter, the process is repeated so that a second or inner layer 38 is applied in the manner shown in Figure 2 and then allowed to cure. In this way, four such layers can be produced as shown in Figure 4, the number of layers that are applied depending upon the particular application or use. In the diagrammatic showing of Figure 2, it Is assumed that a second layer is in the process of being applied. The application of multilayers has many possibilities. For example, the first layer might be plain and function in the manner of a binder or primer, for example where the coefficient of expansion of the pipe is substantially different from that of the second layer. Also, the first layer might have big chips in it which would stick through the surface of the first layer and the small particles would not be included therein. Thereafter, a second layer could be applied with the small particles in it which would fill in around the peaks of the chips. In this case the peak portions of the big chips would be of size 8 to 36 mesh. Thus, when multiple coatings are being applied, they could be formulated for different purposes and the nesting concept mentioned above where the small particles fill in around the peaks of the large particles is merely one example. The said second layer could be applied in one application. A suitable formulation for a one-mixture application of a second layer might be: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80.00 180.00 Hardener Component Parts by Weight Polyamide 37-610, Reichhold Chemicals, Inc. 7.82 Polyamide 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2341, Union Camp Corporation 13.81 32.64 The two components are mixed inside the pipe and applied in one step.

Additional examples of suitable compositions are set forth below. In each it may be assumed that the base substance with the smaller particles mixed in is applied first and the larger particles are applied second, in the general arrangement shown in Figure 2.

One suitable composition for use in this invention is as follows: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80.00 Asbestos 0.50 Fumed Silica 0.45 180.95 Hardener Component Parts by Weight Polyamine 37-610, Reichhold Chemicals, Inc. 7.82 Polyamine 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2341, Union Camp Corporation 13.81 Titanium Dioxide 1.40 34.04 Larger Particles Component Parts by Weight Aluminium Oxide Chips, 32 mesh 350.2 Another example of a suitable composition is as follows: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80.00 Asbestos 0.50 Fumed Silica 0.45 180.95 Hardener Component Parts by Weight Polyamine 37-610, Reichhold Chemicals, Inc. 7.82 Polyamine 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2341, Union Camp Corporation 13.81 32.64 Larger Paticles Component Parts by Weight Aluminium Oxide Beads - 16 mesh 350.2 Another example of a suitable composition is as follows: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80.00 Asbestos 0.50 Fumed Silica 0.45 180.95 Hardener Component Parts by Weight Polyamine 37-610, Reichhold Chemicals, Inc. 7.82 Polyamine 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2341, Union Camp Corporation 13.81 32.64 Larger Particle Component Parts by Weight Aluminium Oxide Chips - 20 mesh 350.2 Another example of a suitable composition is as follows: Resin and Hardener Component Parts by Weight DER 1004 Epoxy, Dow Chemical Co. 100.00 HY 939 Curative, Ciba-Geigy Corporation 29.00 Silicon Carbide - 180 mesh 80.00 Fumed Silica 0.45 Asbestos 0.50 209.95 Larger Particle Component Parts by Weight Aluminium Oxide Chips - 12 mesh 350.2 It will be noted that this last example is not a three-component composition, but rather only two. It might, for example, be applied and cured by heat, for example 2 hours at about 250 F. followed by an additional, say, 6 hours curing at 350C F. A two-component composition of this type would not need necessarily a mixing head, such as at 28 in Figure 2, but might be applied through a single pipe with the larger abrasion resistant particles being applied thereafter in spaced relation to it.

An additional example of a two-part composition is as follows: Resin and Hardener Component Parts by Weight Epon 826, Shell Chemical Corp 100.00 Diamino diphenyl sulfone 33.00 Silicon Carbide 80.00 Fumed Silica 0.60 213.60 Larger Particles Component Parts by Weight Aluminium Oxide 16 mesh beads 350.2 In certain situations it may be advantageous and desirable to secure a more effective bond both between the base substance and the large-particles and between the base substance and the inside of the pipe. In such a situation, a different series of set of compositions might be desirable. One such is as follows: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80.00 Asbestos 0.50 Fumed Silica 0.45 Epoxy Silane Coupling Agent 0.50 181.45 Hardener Component Parts by Weight Polyamine 37-610, Reichhold Chemicals, Inc. 7.82 Polyamine 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2341, Union Camp Corporation 13.81 Titanium Dioxide 1.40 34.04 Larger Particles Component Parts by Weight Aluminium Oxide Chips 350.2 The same is true of the following example: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80.00 Asbestos 0.50 Fumed Silica 0.45 Epoxy Silane Coupling Agent 0.50 181.45 Hardener Component Parts by Weight Polyamine 37-610, Reichhold Chemicals, Inc. 7.82 Polyamine 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2341, Union Camp Corporation 13.81 32.64 Larger Particles Component Parts by Weight Aluminium Oxide Chips - 32 mesh 350.2 The following example is also typical of the additional bonding to be gained between the base substance and both the larger particles and pipe: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80;00 Asbestos 0.50 Fumed Silica 0.45 Epoxy Silane Coupling Agent 0.50 181.45 Hardener Component Parts by Weight Polyamine 37-610, Reichhold Chemicals, Inc. 7.82 Polyamine 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2341, Union Camp Corporation 13.81 32.64 Larger Particles Component Parts by Weight Aluminium Oxide Chips - 16 mesh 350.2 A variation on the above example is as follows: Resin Component Parts by Weight Polyepoxide 100.00 Silicon Carbide 80.00 Epoxy Silane Coupling Agent 0.50 180.50 Hardener Component Parts by Weight Polyamine 37-610, Reichhold Chemicals, Inc. 7.82 Polyamine 37-622, Reichhold Chemicals, Inc. 11.01 Polyamidoamine 2340, Union Camp Corporation 13.81 32.64 Larger Particles Component Parts by Weight Aluminium Dioxide Chips - 20 mesh 350.2 As a further example of a two-component, instead of a three-component formulation, with improved bonding due to the inclusion of a coupling agent, the following is an example: Resin and Hardener Component Parts by Weight DER 1004 Epoxy, Dow Chemical Co. 100.00 HY 939 Curative, Ciba-Geigy Corporation 29.00 Silicon Carbide - 180 mesh 80.00 Fumed Silica 0.45 Asbestos 0.50 Epoxy Silane Coupling Agent 0.50 210.45 Larger Particles Component Parts by Weight Aluminium Oxide Chips - 12 mesh 350.2 As a further variation on a two-component system, the following formulation is an example: Resin and Hardener Component Parts by Weight Epon 286, Shell Chemical Corporation 100.00 Diamino diphenyl sulfone, Ciba-Geigy Corporation 33.00 Silicon Carbide 80.00 Fumed Silica 0.60 Epoxy Silane Coupling Agent 0.50 214.10 Larger Particles Component Parts by Weight Aluminium Oxide 16 mesh beads 350.2 Factors to be taken into consideration in the preparation of any formulation is the desire to acquire uniform flow and a relatively fast gel time, since the application of the resistant composition to the inner surface of the pipe is in essence a film application. In applying multiple layers, each layer may be a nominal 1/16 inch in thickness. If something on the order of a 12 mesh chip or bead is used as the larger particles, it may well protrude out of the coat when it contacts the inner surface of the pipe, but the next coat tends to mesh with it giving a nominal 1/8 inch coating for the two layers.

Where the particles and base substance are applied in one application, this might have advantage where the mass of the particles is not as efficient in centrifugal casting, for example where the larger particles might be something on the order of 36 mesh. The pipe itself may be of an epoxy resin, a polyester, fibre glass, steel, aluminium or a vinyl ester, the pipe being filament wound or pressure cast. Basically, no primer on the inner surface of the pipe is considered necessary or normally desirable and no special treatment should be involved prior to applying the first wearing layer. But with a particular material, for example a vinyl ester pipe, it may be desirable to use a preliminary primer such as a polymeric material. The combination pipe and coating may be cured in the ambient air or, m the event of cold weather or to accelerate the cure time, warm air may be blown down through the middle. At the same time, an infra-red heat. such as a heat lamp or glow bar, may be applied to the inside or outside, or the pipe may be preheated. The particular heating means is not now considered critical and it might be dielectric radio frequency or induction heating, as well as ultraviolet in the case of a polyester matrix, or flash photolysis.

Claims (21)

WHAT WE CLAIM IS:

1. A generally circular cross-section pipe with a lining adhering to its inside surface and manufactured by the method of claim 16, the lining being resistant to wear by an abrasive medium such as coal slurry and comprising larger abrasion resistant particles of a size between 8 and 36 mesh dispersed in a base substance including a cured cross-linked thermosetting resin, and smaller abrasion resistant particles of a size between 100 and 225 mesh dispersed in the resin among the larger particles.

2. A pipe according to claim 1, in which the said larger abrasion resistant particles are metal-coated alumina ceramic particles.

3. A pipe according to claim 2, in which the ceramic particles comprise spherical beads.

4. A pipe according to any one of claims 1-3, in which the smaller abrasion resistant particles comprise silicon carbide.

5. A pipe according to any preceding claim, in which the thermosetting resin is an epoxy resin.

6. A pipe according to any one of claims 1-4, in which the thermosetting resin is an unsaturated polyester resin.

7. A pipe according to any one of claims 14, in which the thermosetting resin is a polyurethane resin.

8. A pipe according to any one of claims 1-4, in which the thermosetting resin is a polyamide resin.

9. A pipe according to any one of claims 1-4, in which the thermosetting resin is a polyimide resin.

10. A pipe according to any one of claims 1-9, in which the smaller abrasion resistant particles are of substantially 180 mesh size, and the larger abrasion resistant particles are substantially 1/16th inch in their largest dimension.

11. A pipe according to any one of claims 1-9, in which the smaller abrasion resistant particles are substantially 100 mesh size, and the larger abrasion resistant particles are substantially 1/16th inch in their largest dimension.

12. A pipe according to any one of claims 1-9, in which the smaller abrasion resistant particles are of substantially 180 mesh size, and the larger abrasion resistant particles are substantially 1/32nd inch in their largest dimension.

13. A pipe according to any one of claims 1-9, in which the smaller abrasion resistant particles are of substantially 180 mesh size, and the said abrasion resistant particles are substantially 1/12th inch in their largest dimension.

14. A pipe according to any preceding claim, in which the pipe is made of a fibre glass reinforced polymer.

15. A pipe according to claim 1, substantially as described herein with reference to the accompanying drawing.

16. A method of lining the inside of a pipe to increase its resistance to wear, the method including the steps of disposing the pipe about a generally horizontal axis and in a state to be rotated, providing a cross-lmkable thermosetting resin and a separate curing agent for the resin, rotating the pipe about its horizontal axis at a rate of speed that will centrifuge a lining about the inside thereof, transporting the resin and the curing agent separately along the inside of the pipe out of contact therewith towards a zone of initial application within the pipe and adjacent one end of the pipe, mixing the resin and curing agent at a point of mixture inside the pipe to form a base substance, applying the base substance progressively along the inside of the pipe (whilst the pipe is being rotated) commencing at said zone of initial application adjacent one end of the pipe and moving along the pipe towards its other end whereby to progressively form a layer of base substance on the inside of the pipe, adding to the base substance already on the pipe (commencing during application of the base substance) abrasion resistant particles which are applied at a zone spaced behind the zone of application of the base substance to thereby apply a uniform deposit of particles progressively to the base substance on the inner surface thereof, and allowing the mixture of base substance and particles to cure and adhere to the inner surface of the pipe to form a finished lined pipe product.

17. A method according to claim 16, in which the particles added to the base substance are larger than other, smaller abrasion-resistant particles added to the base substance before it is applied to the pipe.

18. A method according to claim 16 or claim 17 which includes applying multiple layers of the lining to the inside of the pipe, one on top of the other, each substantially 1/16th inch thick.

19. A method according to any one of claims 16-18 which comprises allowing the lining to cure at room temperature.

20. A method according to any one of claims 16-18 which includes applying a separate source of energy to accelerate the cure of the lining.

21. A pipe made by the method of any of claims 16 to 20.