US 2828798 A
Description (OCR text may contain errors)
April 1, 1958 .1. R. HOPKlNS ET 2,823,798
METHOD OF APPLYING A PROTECTIVE WRAPPING TO A PIPE Filed March 9, 1955 A T TOR/V5) "genous covering for the surface.
United States Patent O METHOD OF APPLYING A PROTECTIVE WRAPPENG TO A PIPE John R. Hopkins, Denver, Colo., and Frank E. McNulty, Tulsa, Okla.
Application March 9, 1955, Serial No. 493,244
2 Claims. (Cl. 154-41) This invention relates to a new method of applic tion of a protective wrapping to a pipe or conduit. More particularly the invention relates to a protective sheet comprising commercial coal tar enamel, asphalt or micro-crystalline wax reinforced by a glass fabric and applying said sheet to a metallic surface such as that of a pipe without the application of heat and at normal atmospheric temperatures.
The primary object of the invention is to provide a cold method of applying the material described to a metallic pipe or conduit without the necessity of heating the material.
A further object of the invention is to provide a cold bonding of the type described at normal atmospheric temperatures including the step of first applying to the conduit a special solvent release primer.
Other objects and advantages will become apparent upon considering the following detailed description in conjunction with the drawings wherein like numerals represent similar elements throughout and wherein:
Figure l is a side elevational view of a roll of pliable wrapping material;
Figure 2 is an enlarged fragmentary view of a portion of the roll of Figure 1;
Figure 3 is a perspective view illustrating cold application to a pipe of the material of Figure l; and
Figure 4 is a perspective view illustrating hot application to a pipe of the material of Figure 1.
This application is a continuation-impart of John R. Hopkins U. S. application S. No. 210,437 entitled, Pack of Materials for Wrapping Pipes and the Like and filed February 12, 1951, now abandoned.
Broadly, this invention is directed to providing a wrapping material for pipes and the like and to a coldmethd of application of the material on the pipe whereby the material protects the wrapped area of the pipe against several factors or elements. Preferably, the wrapping material consists of a sheet of woven glass cloth saturated and coated on both sides thereof with an appreciable amount of a .high melting bituminous substance or special wax and when stored, a considerable supply of such sheet preferably is wound about aspool or the like and each convolution of the sheet is separated by a layer of paper or the like which is non. adherent to the said sheet, the. paper having been treated to have adhesive qualities. In applying such wrapping material by-a. hot coating process, a cold bituminous liquid-like primer is spread, by brushing or the like, over the area of the pipe or other metallic surface that it. is desired to coat, thereafter the wrapping material is helically or spirally wound about the surfacewith each convolution as it. is wound overlapping in part theprevious convolution and during the wrapping: and thereafter heat, by means of a torch or. the like, is. applied to the convolutions to soften, melt and. bond the coating to the surface, Actually the primer and coating material are chemically compatible'and, after heating, both form and provide a homo in connection with the cold coating process of this invention, a cold grease-like b1tuminous primer is applied by hand or the like and then while the primer is wet the wrapping is cigarette wrapped about the surface on the primer in single thickness, except for a longitudinal lapping at the edges, and thereafter additional cold'primer of a similar bituminous nature may be applied at the longitudinal lap to permit sealing the entire wrapping and primer and bonding of same to the surface. In actuality, the primer contains a solvent which is absorbed by the wrapping and then dissipate and the residue of the primer and the wrapping solidify to provide a homogeneous covering. The cold coating is accomplished without the necessity of any heat and the solvent is volatile at normal atmospheric temperatures.
The application of protective coatings or wrappings of coal tar and the like to the exterior of metallic surfaces, such as pipes and other structures, is known and taught by the prior art, especially the application of heated protective substances in liquid form. However, the method of applying such wrappings to metallic surfaces involves cumbersome equipment such as tar pots, pouring buckets, slings, chopping platforms and various special handling apparatus. Also, prior wrappings often contain reinforcing means such as cloth of cotton or'othef organic material and, of course, the wrapping When cooled becomes sealed to the covered area of the metallic surface. The coal tar used is derived from'coal and is a product which is made from coal tar pitch, so treated as to have its carbon in suspension and to which has been added other stablilizing substances such as talc and ash.
The present invention employs, in one form thereof, this coal tar product which in commerce is known as coal tar enamel but Which will be referred to hereinafter as merely coal tar. Preferably, the'coal tar eniployed has the same ductility and viscosity over wide temperature ranges and is of the type that when subjected to temperatures above substantially degrees F. it begins to become tacky with increasing tackiness as the temperatures increase. When it is cold it has little tackiness, but does have an adhesiven'ess to itself over periods of time and has sticky characteristics. Of course, when employed in the summer time in a hot climate, the penetration would be lowered and the softening point increased and, in cold temperatures, the penetration would be slightly increased and the softening point slightly decreased. Examples of suitable coal tar are those sold under the name of cold tar enamel and manufactured by Reilly Tar and Chemical Company of Indianapolis,- Indiana; Koppers Company and Pittsburgh Coke and Chemical Company of Pittsburgh, Pennsylvania and Barretts Company of New York, New York.
instead of coal tar, another high melting bituminous product, namely asphalt which is derived from petroleum, may be used as a major constituent of the wrapping or protective coating. The asphalt should have a softening point of about 200 degrees F. and contain a desired' p'efcentage of stabilizing and filler substances such as talc and ash. Of course, as explained in connection with coal tar, the softening point and penetration should be varied slightly, depending'upon the climate. Pa'bco Products, Inc. of California, Lion Oil Company of Arkansas and Huskey Oil Company of Wyoming supply fasphalt of suitable type, Pabco identifying the asphalt as Pabco floatline enamel pipe coatingcommodity No. 239.
As a substitute for the normally non-tacky, high melting bituminous material such as coal tar and asphalt, micro-crystalline wax may be used. The wax is a paraffin derived from petroleum crude oil and con-taihir'igquite a few of the hydrocarbons present in the above described asphalt. Preferably, such wax has a specific gravity of -of woven glass cloth or glass fabric.
separation from such surfaces difiicult.
about .90, a melting point of between 160 degrees F. to .170 degrees F., a viscosity at 325 degrees F. of 85-90 S. V. and at 225 degrees F. of 260-280 S. V. and a flash point of 550 degrees F. When used in hot climates, the wax material is sometimes hardened by adding not more than percent by weight of asphalt of a lower penetration and higher softening point than the melting point of the wax. Suppliers of the wax are the Dearborn Chemical Company of Chicago, Illinois, and the Trenton Corp. of Ann Arbor, Michigan, the latter identifying the product as Trenton Mummy Wrap Protective Coatings.
Preferably, the coal tar, asphalt and micro-crystalline Wax should be of the type having low moisture absorbency, high dielectric characteristics, resistance to soil stress and softening and penetration points that will prevent at ground temperatures cracking on the one hand and rocks and the like from penetrating therethrough on the other hand.
As stated, the present invention relates to a cold method of applying to a pipe a coating or wrapping of high bituminous material or micro-crystalline wax of the types described having imbedded therein a reinforcing material Reinforcing with woven glass cloth is desirable as glass fibers are strong and durable, withstand heat and last indefinitely besides having superior reinforcing qualities. Such wrapping or coating must be packaged for use so that sheets may be stored and readily applied in the field.
The fiberglass product preferably consists of a 28 by 32 weave construction and is woven from 1-150s yarn. The suppliers of this material are Hess, Goldsmith and Company, New York, New York, Industrial Merchants Fabrics, New York, New York, and United Fabrics Merchants, New York, New York. Although materials of other weave construction and other yarn specifications can be used, we have found that the 28 by 32 weave construction is the most desirable for our use. A Weave construction consisting of fewer strands of yarn per square inch makes it impossible to retain an even thickness of coating material on each side of the glass. A closer weave than 28 by 32 eliminates the possibility of having the coating sheath on each side of the glass keyed together through the voids between the pieces of yarn. This results in the bituminous material or wax often cracking and chipping off of the glass fabric when flexed or handled roughly, at extremely low temperatures. The 28 by 32 weave construction provides extremely strong reinforcement to the coating, facilitates production so .that there can be maintained an even distribution of coating on each side of the glass fabric, and still is of an open enough weave to allow the sheath of coating on each side of the glass to be keyed together through the voids between the pieces of yarn. The bituminous material or wax is applied to the fabric by dipping or the like in a is controlled by the temperature of the bath and the duration of the fabric in the bath while it travels through the bath.
In the past, considerable difficulty has been encountered in providing a roll or package of such a coating or wrapping since the characteristics of such causes it to ad here to almost any known substance if allowed to contact such substance for any period of time, and once stuck to a surface, its pliable cold-flow characteristics makes the In other words, the coating is normally self-adhering if heated or allowed to be in contact for some period of time, because of the affinity of the layers of material to each other. Further,
'in a 'roll or other superposed relation the adjacent layjers will adhere together unless separated in some manner. Heretofore, there has been no known substance which .was satisfactory as a'separator and one practice has been period of two or three weeks.
to use parting mediums such as talc and mica sprinkled upon the surfaces to reduce surface adherence and permit separation of the layers of coating. However, such parting mediums have disadvantages, such as leaving the bituminous material or wax less sticky and less adherent to the pipe. There are available other types of separating mediums such as a sheet of cellulose acetate or the like as a strip sheet, but it is ditficult to remove such a sheet from the coating layer. It has been found that parchment paper treated with a liquid silicone has excellent characteristics as a separating medium. The silicone treated parchment paper which is preferred is one made from vegetable fibers and this then is coated with silicone in liquid form and permitted to dry. It is sold on the market as silicone treated parchment paper and has no afiinity for or is adhesive to the bituminous material or wax and clean separation will always occur. Regardless of the period of time of contact of this parchment paper and the coating, no undesirable characteristics are imparted to the coating and the latter always remains in a state of purity. This is not true of parchment paper which has been treated with other substances and attempted to be used with high melting bituminous material or microcrystalline wax.
Extensive tests have shown that this material is not only repellent to the coating but that the treated paper is of a hardness and density which permits the surfaces of the coating to retain the vapors and lighter constituents which render the coating pliable and of the desired stickiness when the material is to be used at temperatures producing the tacky conditions. Also, through the use of this type of separating medium, the roll can be stored for an indefinite length of time without affecting the sticky surface which is desired for ready application to a metallic surface, such as a pipe. The preferred type of liquid silicone used to render the parchment paper non-adherent is methyl hydrogen polysiloxane. Dow Corning Corporation of Midland, Michigan, is a manufacturer and identifies the liquid or fluid silicone as Dow Corning 1107. Essentially, it is a percent silicone material, liquid in the uncured state, dry when cured and virtually odorless, colorless, and inert to such materials as metals, glass, organic plastics, paper and industrial fabrics.
All of the coating materials used and described above have cold flow characteristics and inherent qualities that would cause one layer to flow in and become part of the next if they were subjected to high temperatures, or to storage for long periods of time. The longer the period of contact of one layer to another, the greater the adhesion between the two. Actually, in summer temperatures that would be considered normal, a roll for example will become solid and cannot be unrolled without damaging and rendering the material worthless, within a The silicone treated parchment paper has excellent non-adhering qualities and allows the roll of coating or wrapping to be unrolled easily regardless of temperature.
intermediate thereof with woven glass cloth or fiber glass fabric 3,. Each sheet 2 may be formed by dipping the fabric 3 into molten coal .tar, asphalt or the said wax to bathe and saturate same, and the degree of thickness may be regulated in the manner explained. The glass fabric reinforcement assures that the strips 2 will have great tensile strength and thus during application to a pipe or the like strong pulling forces are possible, which provides for a better'wrap. The separating medium is shown at 4, such consisting of the described parchment paper treated with liquid silicone. The sheets 2 are packaged in roll form as shown in Figure l with the convolutions of sheet 2 wound on the spool 1 and separated by medium 4 and although the roll package is preferred, the sheets 2 and medium 4 may be alternately arranged in stacked form.
In connection with the cold application method, it is desirable to apply a primer directly onto the metallic surface, such as the pipe 5 illustrated in Figure 3. As mentioned, one of the primary purposes of the wrapping is to protect underground pipe and cable and other metallic structures from corrosion and deterioration from electrolysis. The grease-like primer preferably comprises a coal tar paint obtained principally from oven processed coke and comprising coal tar pitch, coal tar naphtha and an inert inorganic filler such as ash, all suitably processed and blended to produce a smooth, heavy-bodied liquid. The paint shall be free from lumps which cannot be dispersed readily by hand stirring and of such consistency and characteristics as will permit easy application by brushing, on a clean metal surface when the air and metal temperatures are as low as 45 degrees F. When so applied, the dried film shall be free from pinholes and conspicuous brushmarks and shall be not more than slightly seedy, granular, or fibrous in appearance. The paint shall be free from water, ammonia, pyridine, pyridine bases, oil gas tar, asphalt and petroleum derivatives, and shall conform to the following detail requirements. Suitable suppliers of such primer, which is known as CA-50 cold applied coal tar paint, are Reilly Tar and Chemical Company, Indianapolis, Indiana; Koppers Company and Pittsburgh Coke and Chemical Company of Pittsburgh, Pennsylvania; and Barretts Company of New York, New York. As an example, the paint may contain 50% pitch, 25% naphtha, and 25% filler.
Instead of coal tar paint, an asphalt primer may be,
employed, such preferably being essentially the same as the coal tar paint in that it includes a filter and naphtha but, of course, asphalt is substituted for the coal tar. The Standard Oil Company of California supplies such a primer and identifies same as Standard Priming Solution.
The known hot method application comprises the steps of applying a suitable primer such as a cold liquid-like bituminous primer 6 to the pipe area that it is desired to coat, thereafter wrapping spirally about the pipe sheet 2 and heating while wrapping and thereafter to bond the same to the pipe. For example, material 2 may be spirally or helically wrapped around the pipe as shown in Figure 4 with each convolution over-lapping the previous convolution at least in part. The sheet 4 is cast off as it is not needed or it may be used as a shield upon which pressure may be exerted by hand or any suitable tool to cause adherence of the strip 2 to the pipe 2. of a torch 7 which causes melting of the convolutions of sheet 2 and fusing together of the convolutions and primer whereby, when cooled, a solid wrapping or covering surrounds the selected area of the pipe. It might be mentioned that the glass fabric is not materially affected by high heat and such permits the use of a higher melting point material than would be the case if the strips 2 were reinforced with cotton or other organic elements.
In connection with the new cold method of application to a pipe joint, elbow or area, reference is made to Figure 3 wherein it is illustrated that the strip or sheet 2 is wrapped in cigarette fashion to provide the longitudinal lapping 8. The coating may be put up in roll form in the manner described in widths from 2 inches to 36 inches and lengths from 6 inches to 65 feet as this is desirable for cold coating application. The protective wrap cold coating, regardless of its base material (coal tar, asphalt or wax type) is applied by first applying a heavy bodied greasedike solvent release coal tar or asphalt paint primer The necessary heat may be applied by means of the type described in detail and indicated at 6 to the pipe 5 or metallic surface to be coated. Coating 2 is then unrolled and wrapped tightly around the pipe or object to be coated in the manner shown to provide lap 8. It is important that the coating procedure follow closely behind the priming operation so that the cold coating is wrapped or applied while the primer is still wet so that there will be proper bonding of the coating to primer. Additional primer 6 is applied at the lap 8 where the coating is joined to itself and the pipe is then ready to be lowered into the ditch and covered with earth as the primer and wrapping solidify. With this unique technique, there has been completely eliminated the necessity of having men and equipment waiting for the coating to cool enough so that it can be lowered into the ditch without damage to the coating. The coated object can remain exposed to the atmosphere indefinitely without any damage to the coating or can be buried immediately after the coating and in applying the wrapping and primer the pipe is preferably supported on skids or the like. After the wrapping has been applied, the solvent in the primer 6 is absorbed by the coating and then dissipated out into the soil or atmosphere since it is volatile at ordinary atmospheric temperatures, leaving the coating hard and well bonded to the pipe. An evenly distributed coating, properly reinforced, is obtained and the pipe can immediately be buried.
The residue of the primer used is chemically compatible with the coating of the wrapping as in practice preferably coal tar primer is employed if the coating is essentially coal tar enamel and asphalt primer is employed if the coating is primarily asphalt or wax, the latter being clearly compatible with the asphalt primer due to the common derivatives.
A good example of how cold coating proved itself in one instance, is where a company engaged in the transportation of oil products and crude oil, had uncovered 212 feet of 6 inch pipe to repair the leaks and recondition the pipe. After repairing the leaks there was applied a greaselike solvent release primer 6 by hand or the like, and then cold coating 2 was applied on top of the primer, it being possible to cigarette wrap 50 lineal feet of pipe at one time. Of course, sheet 2 could be spirally or helically wrapped as in Figure 4. After wrapping the coating tightly around the pipe, additional primer 6 was applied at the longitudinal lap 8, thus sealing the entire coating together. It took three inexperienced field hands one hour and five minutes to coat the entire 212 feet of 6 inch pipe. If they had used other materials and methods, they would have first had to cold prime the pipe, then wait for the primer to dry, and then carry hot enamel in from some distance, pour the hot enamel and give the entire coated job ample time to cool and solidify before they could lower it into the ditch. With such a hot method or the hot method explained in connection with Figure 4, it would have taken at least several men, considerable time to coat this pipe.
In order to compare the known hot coating with the cold coating, it must first be brought out that both the hot and cold applied coatings or wrappings may be produced in the identical manner and the only difference between them is found in the thickness of the sheath of coating. The hot coating is manufactured at a thickness of .050 of an inch and the cold coating is manufactured in a thickness of .060 of an inch. The reason for this is that the hot coating is applied by heating the sheath of coating with a torch, and spirally wrapping, over-lapping half of the width of the coating, thus producing a protective coating of approximately .100 of an inch thick. The cold coating is preferably cigarette wrapped and is almost always applied at a single thickness. The hot applied coating depends upon the torch to soften and melt the sheath of coating enough to cause it to bond to the metallic surface and seal the laps together. The cold coating eliminates the torch, but depends upon the solvents in 7 the primer to wet and soften the coating surface, enough to cause the coating to bond to the metallic surface and to itself.
The hot coating is used for the most part, by natural gas distribution companies for coating field joints and irregular shaped fittings. This end use is confined, for the most part, to small diameter pipe fittings and conplings. The larger the pipe, the more difficult it is to coat with hot coating, since such a large surface of coating must be heated at one time.
Cold coating has opened a completely new category and type of end uses since extremely large areas can be coated with case at one time, and it not only worksfine for field joints, regardless of their size, but has also proven to be an excellent coating for reconditioning used pipe, for pipe that was in the ground and had been uncovered for repair purposes, and for pipe and other metallic structures in areas where open flames cannot be employed due to fire restrictions and dangers. There are many instances where a pipe line company has a small job, usually maintenance or repair work where there are just a comparatively few square feet of area to be coated. The cold coating method provides a coating that can be applied quickly and easily and overcomes the cost that heretofore made these small coating jobs extremely expensive. Cold coating has also proven to be very successful as a coating for tank bottoms, and many other unusual applications that hot coating has not been practical for due to working conditions, type of work or has just proven itself to be economically prohibitive.
It might be mentioned in connection with the cold coating method that, referring to Figure 3, occasionally it is desirable to apply a second cold primer 6 over the first sheet or wrapping 2 and a second wrapping 2 thereover and this would be accomplished in the same manner as described.
From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure and process. The scope of the invention is to be limited in accordance with the appended claims.
What is claimed is: r e
1. A method of. cold bonding and applying a protective Wrapping to the exterior surface of a metallic conduit at normal atmospheric temperatures, said wrapping comprising a cold preformed sheet of reinforcing fabric saturated and coated on both sides with a non-adhesive substance selected from the group consisting of coal tar, asphalt and microcrystalline wax, said sheet being of at least a size to be wrapped about the conduit, comprising the steps of first applying a cold bituminous primer of grease-like consistency to the surface of the conduit that is to be wrapped, said primer including a residue con- .stituent that is chemically compatible with said coating and selected from the group consisting of asphalt and coal tar, and said primer further including a solvent of the type active to temporarily soften said coating and render the same adhesive, said solvent being volatile at ordinary atmospheric temperatures, thereafter wrapping the sheet tightly around the conduit and over the cold primer while the latter is still wet, the solvent and coating coacting in situ to form an adhesive bonding of the sheet to the conduit, the solvent being absorbed by said sheet and dissipated out of said sheet to form a homogeneous wrapping between the primer residue and sheet.
The method of cold bonding and applying a protective wrapping to the exterior surface of a metallic conduit at normal atmospheric temperatures, said wrapping comprising a cold preformed sheet of reinforcing fabric saturated and coated on both sides with a non-adhesive layer selected from the group consisting of coal tar, asphalt and microcrystalline wax, said sheet being of at least a size to be wrapped about the conduit, comprising the steps of first coating the surface of the conduit with a primer of grease-like consistency which includes a residual constituent selected from the group consisting of coal tar and asphalt and a volatile solvent of a type active to soften the non-adhesive layer of the sheet and render the same adhesive, thereafter wrapping the sheet tightly around the primer-coated conduit before the solvent evaporates, said solvent impregnating the sheet and coacting with the layer in situ to form an adhesive, and finally drying the sheet and'primer at atmospheric temperatures until the solventevaporates leaving the residual constituent and layer formed into a cold dry homogeneous interface bonding the coated and saturated fabric to the conduit.
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