METHODS OF COATING PIPE
United States Patent 3607516
A method is provided for forming an electrically insulative pipe by the steps of assembling an elongated wrapper having an inner band of self-adhering adhesive and an outer band of a mechanically strong material and wrapping said wrapper about a pipe to be protected with one side edge being bent upon itself so as to form an exposed edge of adhesive engaging the adhesive on the opposite edges of the wrap whereby to form an adhesive-to-adhesive bond at the overlap.
US Patent References:
Buoyant, insulated flexible tubing and method of making same
Hamblin - February 1959 - 2874722
Method of forming a pipe covering
Kennedy - March 1962 - 3024153
Laminated protective sheath in sheet form and method of applying same to a pipe
Stokes - May 1962 - 3033724
Method of making a wrapped filter tube of fiberglass and foraminous material
Howard et al. - November 1962 - 3063888
Thin-wall plastic tubing and process of manufacture
Devaney - June 1965 - 3189052
Buoyant, insulated flexible tubing and method of making same
Hamblin - February 1959 - 2874722
Method of forming a pipe covering
Kennedy - March 1962 - 3024153
Laminated protective sheath in sheet form and method of applying same to a pipe
Stokes - May 1962 - 3033724
Method of making a wrapped filter tube of fiberglass and foraminous material
Howard et al. - November 1962 - 3063888
Thin-wall plastic tubing and process of manufacture
Devaney - June 1965 - 3189052
Application Number:
04/881365
Publication Date:
09/21/1971
Filing Date:
12/02/1969
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
156/392, 156/195
International Classes:
F16L58/16; F16L58/02; F16L58/00
Field of Search:
156/184,187,195,392
US Patent References:
Primary Examiner:
Padgett, Benjamin R.
Assistant Examiner:
Solyst, Gary G.
Claims:
I claim
1. A method of forming an electrically insulative wrapped pipe comprising the steps of:
2. A method as claimed in claim 1 wherein the wrapper is applied helically about the pipe and the overlap of each succeeding wrap forms a helical rib from one end of the pipe to the other.
3. A method as claimed in claim 1 wherein the pipe is coated with a primer prior to wrapping.
4. A method as claimed in claim 1 wherein the outer layer is a member from the group consisting of ethylene-vinyl acetate, polypropylene, polyvinyl chloride, polycarbonates, cellulose acetate, cellulose butyrate, polyesters, polystyrene, polyethylene copolymer and polyolefins.
5. A method as claimed in claim 1 wherein the inner layer is a member from the group consisting of natural rubber, styrene butadiene rubber, butyl rubber, neoprene, nitrile rubber, ethylene propylene copolymer or terpolymer, polyvinyl chloride and polysulfide rubber.
1. A method of forming an electrically insulative wrapped pipe comprising the steps of:
2. A method as claimed in claim 1 wherein the wrapper is applied helically about the pipe and the overlap of each succeeding wrap forms a helical rib from one end of the pipe to the other.
3. A method as claimed in claim 1 wherein the pipe is coated with a primer prior to wrapping.
4. A method as claimed in claim 1 wherein the outer layer is a member from the group consisting of ethylene-vinyl acetate, polypropylene, polyvinyl chloride, polycarbonates, cellulose acetate, cellulose butyrate, polyesters, polystyrene, polyethylene copolymer and polyolefins.
5. A method as claimed in claim 1 wherein the inner layer is a member from the group consisting of natural rubber, styrene butadiene rubber, butyl rubber, neoprene, nitrile rubber, ethylene propylene copolymer or terpolymer, polyvinyl chloride and polysulfide rubber.
Description:
This invention relates to methods of coating pipe and particularly to a method of coating pipe using a tape having a self-adhesive, self-sealing or pressure-sensitive layer.
The coating of pipe to provide protection against corrosion particularly by electrolyte process is old and well known. Wrappers of various kinds have been applied over painted coatings of asphalts and like materials for many years. So also have coatings of pressure-sensitive and like tapes been applied directly to the metallic pipe surface. Unfortunately the resultant coatings have not been entirely satisfactory for a variety of reasons. In the application of tape over a painted coating there are problems of maintaining uniformity of coating thickness as well as integrity of the total coating. Moreover such coatings require a two or more stage application of the several layers making up the coating with a variety of specialized equipment for the application. In the case of pressure-sensitive and like tapes, the problem is primarily lack of integrity of the coating and resultant leakage at the overlapped joints. Experience has shown and logic reasons that pressure-sensitive tapes which can be unrolled from their coils by readily unwinding, do not possess sufficient bonding strength between the pressure-sensitive adhesive and the backing of the tape or it would not unroll. A pressure-sensitive tape that can be so easily unrolled will possess no greater ability to bond to its own backing at the overlap when applied to the pipe, and therefore, will not provide a sufficient watertight seal at the overlap area, thus permitting moisture to enter under the insulation at this point.
I have found a method of overcoming these problems of the prior art methods and at the same time providing a raised protective rib which protects the coating from damage while the pipe is being handled and covered.
Preferably I form an electrically insulative wrapped pipe by the steps of assembling an elongated wrapper having an inner band of a self-adhering adhesive material and an outer band of a mechanically strong material, wrapping said elongated wrapper about a pipe to be coated with one side edge being bent back upon itself so as to form an exposed edge of adhesive engaging the adhesive on the opposite edge of the wrap whereby to form an adhesive to adhesive bond at the overlap of such wrap. The tension will be increased at the lap area due to the increased thickness, thus affecting a greater fusion of the pressure-sensitive or self-sealing adhesive within the fold. By turning back the fold the possibility of moisture seeping in at the overlap is eliminated. Preferably the wrap is applied in helical form so as to form a continuous helical rib extending around the pipe from end to end. By actual tests using a Dillon Universal Testing Machine, one typical grade of pressure-sensitive pipeline tape identified as No. 43, manufactured by Minnesota Mining & Manufacturing Company, it can be seen that the bond strength of adhesive to adhesive is three times greater than the bond strength between the adhesive and the backing of this tape. This test was conducted by using 5-inch strips of tape as follows: (1) Place the pressure-sensitive adhesive side of two strips face to face for a total of 3 inches in length, leaving two of the 2-inch ends unattached. Place these 2-inch tabs in the jaws of the Dillon Universal Testing Machine and record the pounds pull required to separate the 3-inch area. (2) Place the pressure-sensitive adhesive side on one strip on the plastic back side of the second strip for a total of 3 inches in length, leaving 2 of the 2-inch ends unattached. Place these 2-inch tabs in the jaws of the Dillon Universal Testing Machine and record the pounds pull required to separate the 3-inch area. When comparing self-sealing tapes manufactured for pipeline use, products such as that manufactured by Plicoflex rely on the softness of their butyl vinyl sealant to squeeze out under pressure to affect a seal at the lap in an area approximately one-sixteenth of an inch as they obtain little or no bond of the adhesive to their PVC backing. But by my invention a product of this type will have the advantage of extending the self-sealing area to as much as one-half inch and the bond between the two self-sealing layers will now be determined by the cohesive strength of the compound. The adhesive may be any of the pressure-sensitive and self-sealing materials used in the present forms of pressure-sensitive and self-sealing wrappers. It may be for example natural rubber, styrene butadiene rubber, butyl rubber, neoprene, nitrile rubber, polysulfide rubber, ethylene propylene copolymer or terpolymer and the like. The outer band or layer is preferably a strong resilient material such as a film of polyvinyl chloride, polypropylene, cellulose acetate, polyolefins, polycarbonates, polyesters and the like material. The band or wrapper may be applied to a pipe or over a wet or dry primer.
In the foregoing general description of my invention I have set out certain purposes, objects and advantages of my invention. Other objects, purposes and advantages of the invention will be apparent from a consideration of the following description and the accompanying drawings in which:
FIG. 1 is an isometric view of a pipe having a coating applied according to my invention,
FIG. 2 is a cross section of a coated pipe according to my invention.
Referring to the drawings I have illustrated a pipe 10 having applied thereto a wrapper made up of a band 11 of polyethylene having a layer 12 of adhesive elastomer on one side thereof. One edge 13 of the wrapper is turned over upon itself as it is applied to the pipe 10 so that an exposed face of adhesive 12 engages the adhesive layer 12 of the opposite edge 14 of the next succeeding wrap of the wrapper on the pipe. As the wrapper is drawn tight the adhesive layers flow together forming a complete seal and at the same time a helical rib 15 which extends from one end of the pipe to the other and on which the pipe will rest, raising the balance of the coating away from the surface on which the pipe rests. This protects the pipe coating from abrasion and damage while eliminating the problem of leakage at the wrap joint which occurred in the past because the pressure sensitive layer contacted the outer wrap to which it was not adhesively bonded leaving a zone of weakness.
In the foregoing specification I have set out a preferred practice of my invention, however, it will be understood that this invention may otherwise be embodied within the scope of the following claims.
The coating of pipe to provide protection against corrosion particularly by electrolyte process is old and well known. Wrappers of various kinds have been applied over painted coatings of asphalts and like materials for many years. So also have coatings of pressure-sensitive and like tapes been applied directly to the metallic pipe surface. Unfortunately the resultant coatings have not been entirely satisfactory for a variety of reasons. In the application of tape over a painted coating there are problems of maintaining uniformity of coating thickness as well as integrity of the total coating. Moreover such coatings require a two or more stage application of the several layers making up the coating with a variety of specialized equipment for the application. In the case of pressure-sensitive and like tapes, the problem is primarily lack of integrity of the coating and resultant leakage at the overlapped joints. Experience has shown and logic reasons that pressure-sensitive tapes which can be unrolled from their coils by readily unwinding, do not possess sufficient bonding strength between the pressure-sensitive adhesive and the backing of the tape or it would not unroll. A pressure-sensitive tape that can be so easily unrolled will possess no greater ability to bond to its own backing at the overlap when applied to the pipe, and therefore, will not provide a sufficient watertight seal at the overlap area, thus permitting moisture to enter under the insulation at this point.
I have found a method of overcoming these problems of the prior art methods and at the same time providing a raised protective rib which protects the coating from damage while the pipe is being handled and covered.
Preferably I form an electrically insulative wrapped pipe by the steps of assembling an elongated wrapper having an inner band of a self-adhering adhesive material and an outer band of a mechanically strong material, wrapping said elongated wrapper about a pipe to be coated with one side edge being bent back upon itself so as to form an exposed edge of adhesive engaging the adhesive on the opposite edge of the wrap whereby to form an adhesive to adhesive bond at the overlap of such wrap. The tension will be increased at the lap area due to the increased thickness, thus affecting a greater fusion of the pressure-sensitive or self-sealing adhesive within the fold. By turning back the fold the possibility of moisture seeping in at the overlap is eliminated. Preferably the wrap is applied in helical form so as to form a continuous helical rib extending around the pipe from end to end. By actual tests using a Dillon Universal Testing Machine, one typical grade of pressure-sensitive pipeline tape identified as No. 43, manufactured by Minnesota Mining & Manufacturing Company, it can be seen that the bond strength of adhesive to adhesive is three times greater than the bond strength between the adhesive and the backing of this tape. This test was conducted by using 5-inch strips of tape as follows: (1) Place the pressure-sensitive adhesive side of two strips face to face for a total of 3 inches in length, leaving two of the 2-inch ends unattached. Place these 2-inch tabs in the jaws of the Dillon Universal Testing Machine and record the pounds pull required to separate the 3-inch area. (2) Place the pressure-sensitive adhesive side on one strip on the plastic back side of the second strip for a total of 3 inches in length, leaving 2 of the 2-inch ends unattached. Place these 2-inch tabs in the jaws of the Dillon Universal Testing Machine and record the pounds pull required to separate the 3-inch area. When comparing self-sealing tapes manufactured for pipeline use, products such as that manufactured by Plicoflex rely on the softness of their butyl vinyl sealant to squeeze out under pressure to affect a seal at the lap in an area approximately one-sixteenth of an inch as they obtain little or no bond of the adhesive to their PVC backing. But by my invention a product of this type will have the advantage of extending the self-sealing area to as much as one-half inch and the bond between the two self-sealing layers will now be determined by the cohesive strength of the compound. The adhesive may be any of the pressure-sensitive and self-sealing materials used in the present forms of pressure-sensitive and self-sealing wrappers. It may be for example natural rubber, styrene butadiene rubber, butyl rubber, neoprene, nitrile rubber, polysulfide rubber, ethylene propylene copolymer or terpolymer and the like. The outer band or layer is preferably a strong resilient material such as a film of polyvinyl chloride, polypropylene, cellulose acetate, polyolefins, polycarbonates, polyesters and the like material. The band or wrapper may be applied to a pipe or over a wet or dry primer.
In the foregoing general description of my invention I have set out certain purposes, objects and advantages of my invention. Other objects, purposes and advantages of the invention will be apparent from a consideration of the following description and the accompanying drawings in which:
FIG. 1 is an isometric view of a pipe having a coating applied according to my invention,
FIG. 2 is a cross section of a coated pipe according to my invention.
Referring to the drawings I have illustrated a pipe 10 having applied thereto a wrapper made up of a band 11 of polyethylene having a layer 12 of adhesive elastomer on one side thereof. One edge 13 of the wrapper is turned over upon itself as it is applied to the pipe 10 so that an exposed face of adhesive 12 engages the adhesive layer 12 of the opposite edge 14 of the next succeeding wrap of the wrapper on the pipe. As the wrapper is drawn tight the adhesive layers flow together forming a complete seal and at the same time a helical rib 15 which extends from one end of the pipe to the other and on which the pipe will rest, raising the balance of the coating away from the surface on which the pipe rests. This protects the pipe coating from abrasion and damage while eliminating the problem of leakage at the wrap joint which occurred in the past because the pressure sensitive layer contacted the outer wrap to which it was not adhesively bonded leaving a zone of weakness.
In the foregoing specification I have set out a preferred practice of my invention, however, it will be understood that this invention may otherwise be embodied within the scope of the following claims.