CA2121855C - Metallic pipe corrosion and stress resistant coating - Google Patents
Metallic pipe corrosion and stress resistant coating Download PDFInfo
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- CA2121855C CA2121855C CA2121855A CA2121855A CA2121855C CA 2121855 C CA2121855 C CA 2121855C CA 2121855 A CA2121855 A CA 2121855A CA 2121855 A CA2121855 A CA 2121855A CA 2121855 C CA2121855 C CA 2121855C
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- pipe
- coating
- adhesive
- temperature
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
- B29C65/48—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding
- B29C65/52—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding characterised by the way of applying the adhesive
- B29C65/54—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor using adhesives, i.e. using supplementary joining material; solvent bonding characterised by the way of applying the adhesive between pre-assembled parts
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B1/00—Layered products having a general shape other than plane
- B32B1/08—Tubular products
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B15/00—Layered products comprising a layer of metal
- B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
- B32B7/04—Interconnection of layers
- B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
- F16L58/02—Protection of pipes or pipe fittings against corrosion or incrustation by means of internal or external coatings
- F16L58/04—Coatings characterised by the materials used
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
- F16L58/02—Protection of pipes or pipe fittings against corrosion or incrustation by means of internal or external coatings
- F16L58/04—Coatings characterised by the materials used
- F16L58/10—Coatings characterised by the materials used by rubber or plastics
- F16L58/1054—Coatings characterised by the materials used by rubber or plastics the coating being placed outside the pipe
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L58/00—Protection of pipes or pipe fittings against corrosion or incrustation
- F16L58/18—Protection of pipes or pipe fittings against corrosion or incrustation specially adapted for pipe fittings
- F16L58/181—Protection of pipes or pipe fittings against corrosion or incrustation specially adapted for pipe fittings for non-disconnectible pipe joints
Abstract
The present invention provides a coating for metallic pipes having improved corrosion and soil stress resistance, and adapted for both in-the-mill and -over-the-ditch application to said pipes, which coating comprises:a first layer comprising a hot-melt rubberized adhesive applied to the outer surface of a pipe preheated to a temperature of 25°-60°C, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties: Ring and Ball softening temperature : 75°-95°C. Flow Properties, as defined by CSA Z 245.21 Spec: 1-12 mm. Viscosity at 175°C : 10,000 - 100,000 cPs; and a second layer applied over the first layer, said second layer comprising a polyolefin material. Also described herein is a method for applying such coating to a metallic pipe surface. The pipe surface is first cleaned and the pipe is then preheated to a temperature of 25 - 60°C; then hot-melt rubberized adhesive, heated to a temperature above its melting point, is applied to the preheated pipe as a first layer, and immediately thereafter a second layer comprising a polyolef in material, preferably in the form of a tape, is applied over the first layer. The pipeline coating of the present invention is especially suitable for pipeline rehabilitation.
Description
r APPLICATION DISCLOSURE
METALLIC PIPE CORROSION AND STRESS RESISTANT COATING
This invention relates to a corrosion and soil stress resistant coating for metallic pipe surfaces for application to pipes in the field or in the pipe mill and in particular, for use as a coating in pipeline rehabilitation.
Current over-the-ditch coatings for new pipeline construction consist mainly of two groups, cold applied tape, such as polyethylene tape wrap systems and coal tar enamel or asphalt enamel. Both of these coatings are applied to a relatively low degree of pipe cleanliness, typically achieved by a power tool brushing. Many over-the-ditch coatings have failed quite drastically, frequently due to insufficient pipe cleanliness. For coal tar and asphalt coating systems, there are distinct problems, such as those relating to the release of toxic vapours during application and the fact that there is a relatively small temperature range, or window, within which these coatings may be applied, that often lead to pipeline coating failure due to imprecise application of the coating materials.
For polyethylene tape wrap systems, failure is usually due to spiral corrosion and water migration on weld seams, that is corrosion in the area of the overlap where the tape bridges from the steel surface to the other tape it overlaps. This bridging causes water migration, spirally and along all weld seams of the steel pipe.
The above problem is compounded by the fact that some tape coatings are prone to shield the cathodic protection voltage, thus leading to an accelerated corrosion. Some of the coatings have failed to the point where the entire line has to be excavated, the old coating stripped off the pipe, and the new one reapplied in the process called pipe rehabilitation.
The choice of the coatings used in pipeline rehabilitation is at present mostly limited to polyethylene tape, coal tar enamel and to a lesser extent, urethane or coal tar urethane. Urethane coatings require a much higher degree of surface preparation, usually near white or better metal blast, achieved in the field by shot or sandblasting.
Both shot and sandblasting surface preparation methods necessitate use of specialized equipment and are usually much slower than wire brushing. The performance of urethane coatings are in direct proportion to metal cleanliness and therefore, special care and attention are required in the preparation of the pipe surface for their application.
Mill applied coatings, on the other hand, consist of a much wider variety of coatings, the most widely used coatings being fusion bonded epoxy, extruded polyethylene, coal tar enamel and tape.
(1) Shop application Until now, one of the customary methods of coating the pipe in the shop has been by using the rubberized adhesive applied to the body of the pipe, followed by extrusion of the polyethylene outer jacket. The main corrosion protection has been provided by the adhesive, which, thanks to its hydrophobic properties, protects the pipe surface from contact with external environment, such as moisture, air, water, soil and other corrosive agents. The outer extruded jacket has been provided mainly to protect the adhesive from mechanical damage. This process has been known in the industry for over 30 years and some well-known brand names in North America include "Ultrabond" RA and RA-X by Pipe Coating Systems, "Yellow Jacket"*by SHAW and "Extru-coat" by Energy Coatings.
METALLIC PIPE CORROSION AND STRESS RESISTANT COATING
This invention relates to a corrosion and soil stress resistant coating for metallic pipe surfaces for application to pipes in the field or in the pipe mill and in particular, for use as a coating in pipeline rehabilitation.
Current over-the-ditch coatings for new pipeline construction consist mainly of two groups, cold applied tape, such as polyethylene tape wrap systems and coal tar enamel or asphalt enamel. Both of these coatings are applied to a relatively low degree of pipe cleanliness, typically achieved by a power tool brushing. Many over-the-ditch coatings have failed quite drastically, frequently due to insufficient pipe cleanliness. For coal tar and asphalt coating systems, there are distinct problems, such as those relating to the release of toxic vapours during application and the fact that there is a relatively small temperature range, or window, within which these coatings may be applied, that often lead to pipeline coating failure due to imprecise application of the coating materials.
For polyethylene tape wrap systems, failure is usually due to spiral corrosion and water migration on weld seams, that is corrosion in the area of the overlap where the tape bridges from the steel surface to the other tape it overlaps. This bridging causes water migration, spirally and along all weld seams of the steel pipe.
The above problem is compounded by the fact that some tape coatings are prone to shield the cathodic protection voltage, thus leading to an accelerated corrosion. Some of the coatings have failed to the point where the entire line has to be excavated, the old coating stripped off the pipe, and the new one reapplied in the process called pipe rehabilitation.
The choice of the coatings used in pipeline rehabilitation is at present mostly limited to polyethylene tape, coal tar enamel and to a lesser extent, urethane or coal tar urethane. Urethane coatings require a much higher degree of surface preparation, usually near white or better metal blast, achieved in the field by shot or sandblasting.
Both shot and sandblasting surface preparation methods necessitate use of specialized equipment and are usually much slower than wire brushing. The performance of urethane coatings are in direct proportion to metal cleanliness and therefore, special care and attention are required in the preparation of the pipe surface for their application.
Mill applied coatings, on the other hand, consist of a much wider variety of coatings, the most widely used coatings being fusion bonded epoxy, extruded polyethylene, coal tar enamel and tape.
(1) Shop application Until now, one of the customary methods of coating the pipe in the shop has been by using the rubberized adhesive applied to the body of the pipe, followed by extrusion of the polyethylene outer jacket. The main corrosion protection has been provided by the adhesive, which, thanks to its hydrophobic properties, protects the pipe surface from contact with external environment, such as moisture, air, water, soil and other corrosive agents. The outer extruded jacket has been provided mainly to protect the adhesive from mechanical damage. This process has been known in the industry for over 30 years and some well-known brand names in North America include "Ultrabond" RA and RA-X by Pipe Coating Systems, "Yellow Jacket"*by SHAW and "Extru-coat" by Energy Coatings.
(2) Line travel coatings The coatings applied by line travel equipment, or so-*trade-mark - 2 called over-the-ditch coatings, are the coatings applied in the field by specialized equipment.
(2a) Thermoplastic coatings The most widely used over-the-ditch coatings would include hot applied coatings, such as coal tar enamel or asphalt enamel, applied at high temperature (200-250 C) to the pipe by a flooding process and followed by wrapping the pipe with fiberglass and/or asbestos tape. In recent years a lot of valid questions have been raised with regard to this type of coating, since the ingredients have been identified as known carcinogens, and many of these coatings have been banned in Canada and other countries.
(2b) Pipeline tapes Pipeline tapes constitute another group of over-the-ditch coatings. Pipeline tapes belong typically to the polyolefin or PVC group of materials; however some other tapes are used in the industry as well,,such as petrolatum tapes, fiber reinforced tapes, and others. The important fact is that all tapes consist of an adhesive (hot melt, asphaltic or otherwise) and a plastic or cloth reinforced backing.
The tapes are cold applied to the pipe by especially designed tape wrapping machines under tension. The main disadvantage of the coatings is in the fact that they tend to disbond or dislodge from the pipe, tend to lift off in the area of the weld, (spiral, longitudinal or field girth weld), are susceptible to the problems associated with the soil stresses and are subject to the spiral corrosion on the tape overlap, especially in the case of application under too low a tension.
Rubberized adhesive/ polyethylene coatings have been used in North America for over a quarter of a century and the earliest type of this kind of coating, which are still being manufactured to this date, consist of an asphalt-based rubberized adhesive, applied usually by a hard rubber circular wiper, followed by a polyethylene outer jacket, usually applied in a sleeve extrusion process. These types of coatings have exhibited good performance, especially with lines operating at ambient temperature. They have exhibited superior performance to polyethylene tape coatings or coal tar enamel.
Some examples of patented pipe coatings for corrosion and stress resistance are: U.S. Patent No. 4,213,486, which teaches polyolefin/epoxy pipe coating and U.S. Patent No.
(2a) Thermoplastic coatings The most widely used over-the-ditch coatings would include hot applied coatings, such as coal tar enamel or asphalt enamel, applied at high temperature (200-250 C) to the pipe by a flooding process and followed by wrapping the pipe with fiberglass and/or asbestos tape. In recent years a lot of valid questions have been raised with regard to this type of coating, since the ingredients have been identified as known carcinogens, and many of these coatings have been banned in Canada and other countries.
(2b) Pipeline tapes Pipeline tapes constitute another group of over-the-ditch coatings. Pipeline tapes belong typically to the polyolefin or PVC group of materials; however some other tapes are used in the industry as well,,such as petrolatum tapes, fiber reinforced tapes, and others. The important fact is that all tapes consist of an adhesive (hot melt, asphaltic or otherwise) and a plastic or cloth reinforced backing.
The tapes are cold applied to the pipe by especially designed tape wrapping machines under tension. The main disadvantage of the coatings is in the fact that they tend to disbond or dislodge from the pipe, tend to lift off in the area of the weld, (spiral, longitudinal or field girth weld), are susceptible to the problems associated with the soil stresses and are subject to the spiral corrosion on the tape overlap, especially in the case of application under too low a tension.
Rubberized adhesive/ polyethylene coatings have been used in North America for over a quarter of a century and the earliest type of this kind of coating, which are still being manufactured to this date, consist of an asphalt-based rubberized adhesive, applied usually by a hard rubber circular wiper, followed by a polyethylene outer jacket, usually applied in a sleeve extrusion process. These types of coatings have exhibited good performance, especially with lines operating at ambient temperature. They have exhibited superior performance to polyethylene tape coatings or coal tar enamel.
Some examples of patented pipe coatings for corrosion and stress resistance are: U.S. Patent No. 4,213,486, which teaches polyolefin/epoxy pipe coating and U.S. Patent No.
4,472,231 which teaches a polyolefin/adhesive pipe coating.
U.S. Patent No. 4,668,576 teaches a polyethylene tape coating which supports an adhesive layer, while U.S. Patent No. 4,728,532 teaches an in-the-mill pipe coating method utilizing impregnated tape.
There is therefore a need to provide a high performance, economical and easy to apply mill or over-the-ditch pipeline coating with superior corrosion and soil stress resistance able to operate at moderately high temperatures, particularly in respect of pipeline rehabilitation.
It is an object of the present invention to provide a pipeline coating that is especially suitable for pipeline rehabilitation.
It is a further object of the present invention to provide a pipeline coating that is easy to apply, eliminates hazardous smoke and vapour, and can be applied over a relatively wide range of application temperatures.
It is a further object of the present invention to provide a pipeline coating that provides excellent cathodic disbondment resistance, as well as mechanical protection.
It is a further object of the present invention to provide a pipeline coating with improved spiral corrosion, bridging and water migration resistance properties.
It is a still further object of the present invention to provide a pipeline coating that does not require sophisticated surface preparation of the pipe.
The present invention takes the art of coating a ~... pipeline one step further beyond what is known in the art by combining the benefits of the shop applied coatings, based on the adhesive and extruded polyethylene, as described above, with the benefits of over-the-ditch tape coatings, but without the disadvantages- of the field applied tape system, as described above.
The improved metallic pipe corrosion and soil stress resistance coatings of the present invention comprise a first layer applied to the outer surface of a pre-heated pipe comprising a hot-melt rubberized adhesive; and a second layer applied over the first layer comprising a polyolefin material.
The second layer may be a polyolefin material, being a polymer derived from the polymerization of relatively simple olef ins, such as polyethylene. The first layer, coated onto the outer surface of a metallic pipe, is a hot-melt rubberized adhesive, with the term hot-melt adhesive used here in the conventional sense and understood to mean a quick melting, thermoplastic material which sets to a firm bond on cooling.
The present invention, in one aspect, resides in an in-the-mill or over-the-ditch process for coating a metallic pipe to impart improved corrosion and soil stress resistance thereto, which comprises: preheating said pipe to a temperature of 25 -60 C;
applying to said preheated pipe a first layer comprising a hot-melt rubberized adhesive preheated to a temperature above its melting point, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75 -95 C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12mm ~.-- Viscosity at 175 : 10,000 - 100,000 cPs; and then applying over said first layer, for mechanical stress resistance, a second layer comprising a polyolefin material.
In another aspect, the present invention resides in a coating for metallic pipes having improved corrosion and soil stress resistance, and adapted for both in-the-mill and over-the-ditch application to said pipes, which coating comprises:
a first layer comprising a hot-melt rubberized adhesive applied to the outer surface of a pipe preheated to a temperature of 25 -60 C, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75 - 95 C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12 mm Viscosity at 175 C : 10,000 - 100,000 cPs; and a second layer applied over the first layer, said second layer comprising a polyolefin material.
The present invention further provides a coated metallic pipe having an -improved corrosion and soil stress resistance coating, said coating comprising:
a first layer comprising a hot-melt rubberized adhesive, applied to the outer surface of a pipe preheated to a temperature of from 25 to 60 C, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75 - 95 C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12 mm Viscosity at 175 C : 10,000 - 100,000 cPs; and a second layer comprising a polyolefin material applied over the first layer.
The coating system of the present invention consists of rubberized adhesive, applied to the body of the pipe at a thickness of 0.25-0.5 mm, followed by the application of a pipeline tape, instead of an extruded polyethylene jacket. The resultant coatings have most of the properties of the extruded polyethylene jacket over rubberized adhesive, the only difference being that it is applied in the form of a tape and not in the form of an extrudate.
This coating eliminates most of the problems typical for the pipeline tape coatings, such as poor soil stress resistance, poor cathodic disbondment properties and tenting effect over welds and surface imperfections, due to the presence of a relatively thick layer of thermoplastic rubberized asphalt-based adhesive.
The hot-melt rubberized adhesive used in the present invention is a physical blend or mixture of several components, which belong chemically to the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers with or without fillers. The precise chemical make-up of the hot-melt rubberized adhesive is not particularly important for purposes of the present invention. In North America there are several suppliers of this type of adhesive, which may be used in the present invention. For instance a suitable adhesive is that sold by Canusa, a division of SHAW Industries, under such names as 3001, 3003, DB-14, and AT-19. Pipe Coating Systems, a division of Garneau Inc., produces a pipeline adhesive sold under the names of RA and RA-X which is also suitable.
Another suitable pipeline adhesive is supplied by the Farboil Company of Baltimore, Maryland under the name of "Adhesive 5700".
The hot-melt rubberized adhesive has the following physical properties:
Ring and Ball Softening Temperature : 750 - 95 C.
U.S. Patent No. 4,668,576 teaches a polyethylene tape coating which supports an adhesive layer, while U.S. Patent No. 4,728,532 teaches an in-the-mill pipe coating method utilizing impregnated tape.
There is therefore a need to provide a high performance, economical and easy to apply mill or over-the-ditch pipeline coating with superior corrosion and soil stress resistance able to operate at moderately high temperatures, particularly in respect of pipeline rehabilitation.
It is an object of the present invention to provide a pipeline coating that is especially suitable for pipeline rehabilitation.
It is a further object of the present invention to provide a pipeline coating that is easy to apply, eliminates hazardous smoke and vapour, and can be applied over a relatively wide range of application temperatures.
It is a further object of the present invention to provide a pipeline coating that provides excellent cathodic disbondment resistance, as well as mechanical protection.
It is a further object of the present invention to provide a pipeline coating with improved spiral corrosion, bridging and water migration resistance properties.
It is a still further object of the present invention to provide a pipeline coating that does not require sophisticated surface preparation of the pipe.
The present invention takes the art of coating a ~... pipeline one step further beyond what is known in the art by combining the benefits of the shop applied coatings, based on the adhesive and extruded polyethylene, as described above, with the benefits of over-the-ditch tape coatings, but without the disadvantages- of the field applied tape system, as described above.
The improved metallic pipe corrosion and soil stress resistance coatings of the present invention comprise a first layer applied to the outer surface of a pre-heated pipe comprising a hot-melt rubberized adhesive; and a second layer applied over the first layer comprising a polyolefin material.
The second layer may be a polyolefin material, being a polymer derived from the polymerization of relatively simple olef ins, such as polyethylene. The first layer, coated onto the outer surface of a metallic pipe, is a hot-melt rubberized adhesive, with the term hot-melt adhesive used here in the conventional sense and understood to mean a quick melting, thermoplastic material which sets to a firm bond on cooling.
The present invention, in one aspect, resides in an in-the-mill or over-the-ditch process for coating a metallic pipe to impart improved corrosion and soil stress resistance thereto, which comprises: preheating said pipe to a temperature of 25 -60 C;
applying to said preheated pipe a first layer comprising a hot-melt rubberized adhesive preheated to a temperature above its melting point, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75 -95 C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12mm ~.-- Viscosity at 175 : 10,000 - 100,000 cPs; and then applying over said first layer, for mechanical stress resistance, a second layer comprising a polyolefin material.
In another aspect, the present invention resides in a coating for metallic pipes having improved corrosion and soil stress resistance, and adapted for both in-the-mill and over-the-ditch application to said pipes, which coating comprises:
a first layer comprising a hot-melt rubberized adhesive applied to the outer surface of a pipe preheated to a temperature of 25 -60 C, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75 - 95 C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12 mm Viscosity at 175 C : 10,000 - 100,000 cPs; and a second layer applied over the first layer, said second layer comprising a polyolefin material.
The present invention further provides a coated metallic pipe having an -improved corrosion and soil stress resistance coating, said coating comprising:
a first layer comprising a hot-melt rubberized adhesive, applied to the outer surface of a pipe preheated to a temperature of from 25 to 60 C, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75 - 95 C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12 mm Viscosity at 175 C : 10,000 - 100,000 cPs; and a second layer comprising a polyolefin material applied over the first layer.
The coating system of the present invention consists of rubberized adhesive, applied to the body of the pipe at a thickness of 0.25-0.5 mm, followed by the application of a pipeline tape, instead of an extruded polyethylene jacket. The resultant coatings have most of the properties of the extruded polyethylene jacket over rubberized adhesive, the only difference being that it is applied in the form of a tape and not in the form of an extrudate.
This coating eliminates most of the problems typical for the pipeline tape coatings, such as poor soil stress resistance, poor cathodic disbondment properties and tenting effect over welds and surface imperfections, due to the presence of a relatively thick layer of thermoplastic rubberized asphalt-based adhesive.
The hot-melt rubberized adhesive used in the present invention is a physical blend or mixture of several components, which belong chemically to the group of asphaltenes, elastomers, rubbers, resins, polymers and copolymers with or without fillers. The precise chemical make-up of the hot-melt rubberized adhesive is not particularly important for purposes of the present invention. In North America there are several suppliers of this type of adhesive, which may be used in the present invention. For instance a suitable adhesive is that sold by Canusa, a division of SHAW Industries, under such names as 3001, 3003, DB-14, and AT-19. Pipe Coating Systems, a division of Garneau Inc., produces a pipeline adhesive sold under the names of RA and RA-X which is also suitable.
Another suitable pipeline adhesive is supplied by the Farboil Company of Baltimore, Maryland under the name of "Adhesive 5700".
The hot-melt rubberized adhesive has the following physical properties:
Ring and Ball Softening Temperature : 750 - 95 C.
*trade-mark Flow Properties, as defined by CSA Z 245.21 spec.: 1-12 mm.
Viscosity at 175 C 10,000 - 100,000 cPs.
The adhesive is applied to the preheated outer surface of a metallic pipe by any conventional process.
The present invention, in one aspect, comprises a unique, two layer coating process for imparting to metallic pipes, corrosion and soil stress resistance, the coating process involving first preparing the pipe outer surface by cleaning, followed by pipe preheating, both of these by any known conventional means. For instance, mechanical brush abrasive cleaning may be used to prepare the pipe surface.
The pipe is then preheated to a temperature of from 25 to 60 C, and preferably to a temperature in the range of 45 -60 C. The step of heating the pipe is essential for the successful application of the coating. The adhesive itself must be heated to a temperature above its melting point and preferably to a temperature in the range of 150 -175 C. The step of heating the pipe removes the moisture from the pipe surface and brings the temperature of the pipe to the range in which the adhesive wets the pipe surface properly. Of course, exposure of the pipe to warm ambient temperature such as those experienced during the summer or in the sunshine may achieve the same purpose without the necessity of heating the pipe by torches or other conventional man-made heating devices.
Thereafter, the hot-melt rubberized adhesive is applied to the pipe surface, the adhesive having been preheated to a temperature above the melting point of the adhesive.
The temperature of the preheated pipe and of the hot-melt rubberized adhesive must be in a range that will allow the adhesive formulation being used to flow, such that it will flow into the anchor pattern, pits, crevices and weld seams of the pipe, wetting the steel surface and creating a strong, water resistance and corrosion proof bond.
Viscosity at 175 C 10,000 - 100,000 cPs.
The adhesive is applied to the preheated outer surface of a metallic pipe by any conventional process.
The present invention, in one aspect, comprises a unique, two layer coating process for imparting to metallic pipes, corrosion and soil stress resistance, the coating process involving first preparing the pipe outer surface by cleaning, followed by pipe preheating, both of these by any known conventional means. For instance, mechanical brush abrasive cleaning may be used to prepare the pipe surface.
The pipe is then preheated to a temperature of from 25 to 60 C, and preferably to a temperature in the range of 45 -60 C. The step of heating the pipe is essential for the successful application of the coating. The adhesive itself must be heated to a temperature above its melting point and preferably to a temperature in the range of 150 -175 C. The step of heating the pipe removes the moisture from the pipe surface and brings the temperature of the pipe to the range in which the adhesive wets the pipe surface properly. Of course, exposure of the pipe to warm ambient temperature such as those experienced during the summer or in the sunshine may achieve the same purpose without the necessity of heating the pipe by torches or other conventional man-made heating devices.
Thereafter, the hot-melt rubberized adhesive is applied to the pipe surface, the adhesive having been preheated to a temperature above the melting point of the adhesive.
The temperature of the preheated pipe and of the hot-melt rubberized adhesive must be in a range that will allow the adhesive formulation being used to flow, such that it will flow into the anchor pattern, pits, crevices and weld seams of the pipe, wetting the steel surface and creating a strong, water resistance and corrosion proof bond.
`-' A preferred aspect of the present invention is illustrated in the attached drawing, which is a diagram depicting the application of the first coating of hot-melt rubberized adhesive and the second coating of a polyolefin tape, to the surface of a steel pipe.
Following is a more detailed description of a method of practising the present invention.
Process conditions are as follows:
The pipe surface to be coated must be clean of foreign material and warmed up sufficiently to dry it, if necessary and to keep it at least 3 C above the dew point temperature during the process as described hereinafter.
The pipe surface is then prepared abrasively to the commercial cleanliness, also known in the industry as Sa 2, according to the Swedish Standard SIS 05 00 90, SSPC-SP6, according to the Steel Structure Painting Council SSPC-Vis 1 or NACE No. 3, according to National Association of Corrosion Engineers TM 01 70. Alternatively, the pipe surface can be prepared also to a wire brush cleanliness, equivalent to Sa 1 by the Swedish Standard.
The pipe is heated, preferably to a temperature of 45 -60 C, to allow the adhesive to wet the steel.
The adhesive is heated to a temperature above its melting point in order to allow it to flow into the surface imperfections of the pipe surface.
The adhesive is applied to the pipe by allowing it to come into full contact with the pipe for a certain period of time (typically 1 - 10 seconds), during which time it will wet the pipe surface and flow into the surface pits and other imperfections of the pipe, and solidify sufficiently to deposit a thin layer (0.1mm minimum and up to few millimetres over the corrosion pits) on the steel surface. This is done typically by using a heated device equipped with a circular rubber collar wiper, which deposits the adhesive of sufficient thickness onto the pipe and wipes off excessive adhesive. A device of this sort is commonly known in the industry as a Gunk Head.
Immediately after the adhesive application, and typically within 1 to 6 seconds, a polyolefin (preferably polyethylene) tape having a minimum thickness of 0.6 mm. is wrapped onto the still soft and tacky adhesive by a tape wrapping machine. The polyolefin tape contains a thin layer of butyl adhesive, which is compatible with the rubberized adhesive, which is already on the pipe and creates, therefore, an extremely strong bond.
Additional layers of polyolefin (e.g. polyethylene) may if desired be wrapped onto the steel pipe.
The present invention can be carried out under a wide range of environmental conditions including low temperature, down to -40 C, in which case it would be necessary to shield the pipe, so as to retain the heat and temperature, as previously mentioned. The pipe can also be coated during conditions of atmospheric precipitation, in which case a suitable covering such as a tent or a hut would need to be provided so as to keep the pipe dry and to protect the pipe from the elements.
Typical properties of the hot-melt rubberized adhesive/ polyethylene tape coating of the present invention are presented in Table I.
Following is a more detailed description of a method of practising the present invention.
Process conditions are as follows:
The pipe surface to be coated must be clean of foreign material and warmed up sufficiently to dry it, if necessary and to keep it at least 3 C above the dew point temperature during the process as described hereinafter.
The pipe surface is then prepared abrasively to the commercial cleanliness, also known in the industry as Sa 2, according to the Swedish Standard SIS 05 00 90, SSPC-SP6, according to the Steel Structure Painting Council SSPC-Vis 1 or NACE No. 3, according to National Association of Corrosion Engineers TM 01 70. Alternatively, the pipe surface can be prepared also to a wire brush cleanliness, equivalent to Sa 1 by the Swedish Standard.
The pipe is heated, preferably to a temperature of 45 -60 C, to allow the adhesive to wet the steel.
The adhesive is heated to a temperature above its melting point in order to allow it to flow into the surface imperfections of the pipe surface.
The adhesive is applied to the pipe by allowing it to come into full contact with the pipe for a certain period of time (typically 1 - 10 seconds), during which time it will wet the pipe surface and flow into the surface pits and other imperfections of the pipe, and solidify sufficiently to deposit a thin layer (0.1mm minimum and up to few millimetres over the corrosion pits) on the steel surface. This is done typically by using a heated device equipped with a circular rubber collar wiper, which deposits the adhesive of sufficient thickness onto the pipe and wipes off excessive adhesive. A device of this sort is commonly known in the industry as a Gunk Head.
Immediately after the adhesive application, and typically within 1 to 6 seconds, a polyolefin (preferably polyethylene) tape having a minimum thickness of 0.6 mm. is wrapped onto the still soft and tacky adhesive by a tape wrapping machine. The polyolefin tape contains a thin layer of butyl adhesive, which is compatible with the rubberized adhesive, which is already on the pipe and creates, therefore, an extremely strong bond.
Additional layers of polyolefin (e.g. polyethylene) may if desired be wrapped onto the steel pipe.
The present invention can be carried out under a wide range of environmental conditions including low temperature, down to -40 C, in which case it would be necessary to shield the pipe, so as to retain the heat and temperature, as previously mentioned. The pipe can also be coated during conditions of atmospheric precipitation, in which case a suitable covering such as a tent or a hut would need to be provided so as to keep the pipe dry and to protect the pipe from the elements.
Typical properties of the hot-melt rubberized adhesive/ polyethylene tape coating of the present invention are presented in Table I.
TABLE I
TYPICAL COATING PROPERTIES
Adhesive Properties:
Softening Point (ring and ball) 85 C average Adhesive Flow Test (71 C, 1 h) 2 - 8 mm average Coating Properties:
Peel Adhesion at 23 C (Instron) Cross head speed 10 mm/minute 3.5kg/25mm average Peel Adhesion (hanging weight, per CSA Z245.21) 2.0 kg 5mm/min/25mm 2.5 kg 7mm/min/25mm 3.0 kg 10mm/min/25mm 3.5 kg 15mm/min/25mm Cathodic Disbondment (CSA Z.245.21) 28 days, 23 C, 1.5V 10 mm Radius 14 days, 65 C, 1,5V 8 mm Radius 48 hour, 65 C, 1.5V 6 mm Radius Impact Test, 23 C 4.0 J/mm Bend Test, CSA Z.245.21 No cracking Outdoor Exposure (ASTM B-53) 2 years min.
Polyethylene Tensile Strength 12 MPa Polyethylene Tape Elongation 200%
-----------------------------------------------------------Minimum coating thickness in millimetres (ails):
Diameter (in): 3 - 8 10 and up (mm): 89 - 219 273 and up Adhesive: 0.25 (10) 0.30 (12) Polyethylene:
one layer 0.89 (35 mils) 0.89 (35 mils) In order for the coating to provide good adhesion to pipes, as well as excellent cathodic disbondment resistance and mechanical protection in a coating that can be applied to new and rehabilitated pipe using known conventional means and equipment, the coating must have the following properties:
A minimum peel adhesion value of at least 20 N/25 mm strip as a coating with a high peel adhesion will afford a larger degree of protection, provided that all other properties as listed below are met. In general, polyethylene tape coatings have an adhesion ranging from 5 to 10 N/25 mm. In comparison, cold tar enamel and urethane coatings cannot be measured for peel adhesion as they will chip rather than peel off the pipe surface.
High shear adhesion is considered an extremely important property for soil stress resistant purposes.
Under some extreme heavy soil stress conditions, clay can rip the coating off the pipe and/or dislocate the coating entirely, especially at elevated temperatures.
Polyethylene coatings are usually not prone to this kind of damage, especially if their adhesion values are quite high, and especially if they operate at ambient temperatures.
With higher integrity adhesives this problem is greatly reduced or eliminated. -For comparison, the tape coatings have been historically very prone to soil stress damage, resulting sometimes in coatings moving away from or sliding or wrinkling on the pipe. Coal tar enamels have performed poorly in this regard, whereas urethane coatings perform well in soil stress conditions due to their inherent physical properties, provided that they maintain a high level of adhesion to the pipe.
Resistance to impact is a measure of how well the coating will react to forces encountered during pipe loading, transport, stringing, lowering in, backfilling and other construction practices. Impact resistance is a function of many factors, the most important ones being hardness, ambient temperature, coating thickness and quality of the adhesive. A coating with a higher integrity adhesive is more able to withstand transport and construction damage since the outer coating bonds better to the pipe and provides a more integral system, which is harder to dislocate or dislodge from the pipe. In particular, adhesive/polyethylene systems are able to withstand an impact damage of approximately 4 Joules, tape coatings and urethanes of approximately 3 Joules and coal tar enamels of up to 4 Joules. The advantage of adhesive/polyethylene coatings are that they are self healing to a large degree, because adhesive will ooze out of the minor damage area and plug up the damage. In the case of tape systems however, the damage can lead to major problems, as it may cause water migration, which can lead in turn to shielding effects and accelerated corrosion.
Impact damage with coal tar enamel might cause disbondment of the pipe in a large area and might also lead to accelerated corrosion. With urethane coatings the damage is usually localized to the impact area.
Adhesive softening point is a measure of the maximum operating temperature of the entire pipeline. The maximum operating temperature can be conveniently defined as being 20 C below the ring ball softening point, as described in the specification of CAN/CSA-Z.245.21-M92, external polyethylene coating for pipe, Canadian Standards Association, Rexdale, Ontario, 1992. A pipeline utilizing an adhesive with an 85 C softening point can, in theory, be operated at a temperature of up to 65 C. With tape coatings and coal tar enamel, the line can be operated at ambient or slightly elevated temperatures only. An elevated temperature will lead to problems due to soil stresses and resulting accelerated corrosion. A pipeline coated with urethane coatings can be used at operating temperatures varying from ambient to an elevated temperature, depending on the properties of each individual system.
The adhesive flow test is conducted in an oven, at a typical temperature of 710C. A sample of the adhesive is placed inside the flow test fixture at a 450 angle and after one hour the distance of the creep of the adhesive is measured. Well formulated adhesives will move only slightly, whereas poor adhesives will creep as much as several centimetres. Tape, urethane and coal tar enamel coatings are not amenable to this type of testing.
The present invention is applicable to both rehabilitated pipe and to new pipeline construction. An important consideration is the condition of the outer body of the pipe being coated, which is typically full of pits and steel losses due to corrosion. The adhesive is intended to wet the pipe, to flow into the corrosion pits and to fill the sides of the weld seams, so that when the tape is subsequently applied, no tenting is apparent. The adhesive fills all of the surface imperfections of the pipe without any air entrapments, and is subsequently overcoated with polyethylene. It does not really matter, for purposes of the present invention, whether the pipe is stationary and the coating equipment moves along the pipe (as in the over-the-ditch application) or whether the pipe is moving and the equipment is stationary (as in the mill application).
While a particular embodiment of the present invention has been described hereinabove, it will be readily apparent to persons skilled in the art that variations and modifications thereof can be made and/or are possible without departing from the spirit and scope of the invention. It is therefore intended that the present invention not be limited only to what has been specifically described above, but that the invention cover all embodiments as come within the scope of the claims which follow.
TYPICAL COATING PROPERTIES
Adhesive Properties:
Softening Point (ring and ball) 85 C average Adhesive Flow Test (71 C, 1 h) 2 - 8 mm average Coating Properties:
Peel Adhesion at 23 C (Instron) Cross head speed 10 mm/minute 3.5kg/25mm average Peel Adhesion (hanging weight, per CSA Z245.21) 2.0 kg 5mm/min/25mm 2.5 kg 7mm/min/25mm 3.0 kg 10mm/min/25mm 3.5 kg 15mm/min/25mm Cathodic Disbondment (CSA Z.245.21) 28 days, 23 C, 1.5V 10 mm Radius 14 days, 65 C, 1,5V 8 mm Radius 48 hour, 65 C, 1.5V 6 mm Radius Impact Test, 23 C 4.0 J/mm Bend Test, CSA Z.245.21 No cracking Outdoor Exposure (ASTM B-53) 2 years min.
Polyethylene Tensile Strength 12 MPa Polyethylene Tape Elongation 200%
-----------------------------------------------------------Minimum coating thickness in millimetres (ails):
Diameter (in): 3 - 8 10 and up (mm): 89 - 219 273 and up Adhesive: 0.25 (10) 0.30 (12) Polyethylene:
one layer 0.89 (35 mils) 0.89 (35 mils) In order for the coating to provide good adhesion to pipes, as well as excellent cathodic disbondment resistance and mechanical protection in a coating that can be applied to new and rehabilitated pipe using known conventional means and equipment, the coating must have the following properties:
A minimum peel adhesion value of at least 20 N/25 mm strip as a coating with a high peel adhesion will afford a larger degree of protection, provided that all other properties as listed below are met. In general, polyethylene tape coatings have an adhesion ranging from 5 to 10 N/25 mm. In comparison, cold tar enamel and urethane coatings cannot be measured for peel adhesion as they will chip rather than peel off the pipe surface.
High shear adhesion is considered an extremely important property for soil stress resistant purposes.
Under some extreme heavy soil stress conditions, clay can rip the coating off the pipe and/or dislocate the coating entirely, especially at elevated temperatures.
Polyethylene coatings are usually not prone to this kind of damage, especially if their adhesion values are quite high, and especially if they operate at ambient temperatures.
With higher integrity adhesives this problem is greatly reduced or eliminated. -For comparison, the tape coatings have been historically very prone to soil stress damage, resulting sometimes in coatings moving away from or sliding or wrinkling on the pipe. Coal tar enamels have performed poorly in this regard, whereas urethane coatings perform well in soil stress conditions due to their inherent physical properties, provided that they maintain a high level of adhesion to the pipe.
Resistance to impact is a measure of how well the coating will react to forces encountered during pipe loading, transport, stringing, lowering in, backfilling and other construction practices. Impact resistance is a function of many factors, the most important ones being hardness, ambient temperature, coating thickness and quality of the adhesive. A coating with a higher integrity adhesive is more able to withstand transport and construction damage since the outer coating bonds better to the pipe and provides a more integral system, which is harder to dislocate or dislodge from the pipe. In particular, adhesive/polyethylene systems are able to withstand an impact damage of approximately 4 Joules, tape coatings and urethanes of approximately 3 Joules and coal tar enamels of up to 4 Joules. The advantage of adhesive/polyethylene coatings are that they are self healing to a large degree, because adhesive will ooze out of the minor damage area and plug up the damage. In the case of tape systems however, the damage can lead to major problems, as it may cause water migration, which can lead in turn to shielding effects and accelerated corrosion.
Impact damage with coal tar enamel might cause disbondment of the pipe in a large area and might also lead to accelerated corrosion. With urethane coatings the damage is usually localized to the impact area.
Adhesive softening point is a measure of the maximum operating temperature of the entire pipeline. The maximum operating temperature can be conveniently defined as being 20 C below the ring ball softening point, as described in the specification of CAN/CSA-Z.245.21-M92, external polyethylene coating for pipe, Canadian Standards Association, Rexdale, Ontario, 1992. A pipeline utilizing an adhesive with an 85 C softening point can, in theory, be operated at a temperature of up to 65 C. With tape coatings and coal tar enamel, the line can be operated at ambient or slightly elevated temperatures only. An elevated temperature will lead to problems due to soil stresses and resulting accelerated corrosion. A pipeline coated with urethane coatings can be used at operating temperatures varying from ambient to an elevated temperature, depending on the properties of each individual system.
The adhesive flow test is conducted in an oven, at a typical temperature of 710C. A sample of the adhesive is placed inside the flow test fixture at a 450 angle and after one hour the distance of the creep of the adhesive is measured. Well formulated adhesives will move only slightly, whereas poor adhesives will creep as much as several centimetres. Tape, urethane and coal tar enamel coatings are not amenable to this type of testing.
The present invention is applicable to both rehabilitated pipe and to new pipeline construction. An important consideration is the condition of the outer body of the pipe being coated, which is typically full of pits and steel losses due to corrosion. The adhesive is intended to wet the pipe, to flow into the corrosion pits and to fill the sides of the weld seams, so that when the tape is subsequently applied, no tenting is apparent. The adhesive fills all of the surface imperfections of the pipe without any air entrapments, and is subsequently overcoated with polyethylene. It does not really matter, for purposes of the present invention, whether the pipe is stationary and the coating equipment moves along the pipe (as in the over-the-ditch application) or whether the pipe is moving and the equipment is stationary (as in the mill application).
While a particular embodiment of the present invention has been described hereinabove, it will be readily apparent to persons skilled in the art that variations and modifications thereof can be made and/or are possible without departing from the spirit and scope of the invention. It is therefore intended that the present invention not be limited only to what has been specifically described above, but that the invention cover all embodiments as come within the scope of the claims which follow.
Claims (15)
1. An in-the-mill or over-the-ditch method for coating a metallic pipe having an outer surface to impart improved corrosion and soil stress resistance thereto, which comprises the steps of: cleaning said pipe outer surface and, when necessary, preheating said pipe to a temperature of 25°-60°C to dry and maintain said surface at a temperature at least 3°C above the dew point temperature, applying to said pipe surface, when said pipe surface is dry and is at a temperature of 25°C-60°C, a first layer comprising a hot-melt rubberized adhesive preheated to a temperature above its melting point to wet and deposit a bonded layer on said pipe surface at a thickness of 0.25 to 0.55 mm, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group consisting of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature: 75°-95°C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12mm Viscosity at 175°C: 10,000 - 100,000 cPs, the temperature of the preheated pipe and the hot-melt adhesive in a range that allows said adhesive to flow and wet the surface of the pipe; and when said first layer is still soft and tacky applying over said first layer, for mechanical stress resistance, a second layer comprising a polyolefin tape material, having a minimum thickness of 0.6 mm.
Ring and Ball softening temperature: 75°-95°C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12mm Viscosity at 175°C: 10,000 - 100,000 cPs, the temperature of the preheated pipe and the hot-melt adhesive in a range that allows said adhesive to flow and wet the surface of the pipe; and when said first layer is still soft and tacky applying over said first layer, for mechanical stress resistance, a second layer comprising a polyolefin tape material, having a minimum thickness of 0.6 mm.
2. A method according to claim 1 wherein the pipe is preheated to a temperature of 45 -60°C.
3. The method of claim 1, wherein the first layer forms a continuous coating from 0.25 mm to 0.5 mm (10 to 20 mils) in thickness and the second layer forms a coating at least 0.89 mm (35 mils) in thickness.
4. The method of claim 3, wherein the second layer is applied by spirally wrapping the tape of polyolefin material over the first layer.
5. The method of claim 4, wherein the polyolefin material is polyethylene.
6. A coating for the protection of metallic pipe, said coating having improved corrosion and soil stress resistances, and adapted for both in-the-mill and over-the-ditch applications to said pipe, which coating comprises:
a first layer of a thickness of 0.25 to 0.5 mm comprising a hot-melt rubberized adhesive for applying to a dry and precleaned outer surface of the pipe when said surface is at a temperature of 25°-60°C and at least 3°C
above the dew point temperature, the temperature of the preheated pipe and hot-melt adhesive in a range to allow the adhesive to flow and wet, said surface and deposit a bonded layer on said surface, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group consisting of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75° - 95°C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12 mm Viscosity at 175°C: 10,000 - 100,000 cPs; and a second layer for applying over said first layer while said first layer is still soft and tacky, said second layer comprising a polyolefin tape material and of a minimum thickness of 0.6 mm.
a first layer of a thickness of 0.25 to 0.5 mm comprising a hot-melt rubberized adhesive for applying to a dry and precleaned outer surface of the pipe when said surface is at a temperature of 25°-60°C and at least 3°C
above the dew point temperature, the temperature of the preheated pipe and hot-melt adhesive in a range to allow the adhesive to flow and wet, said surface and deposit a bonded layer on said surface, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group consisting of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75° - 95°C
Flow Properties, as defined by CSA Z 245.21 Spec: 1-12 mm Viscosity at 175°C: 10,000 - 100,000 cPs; and a second layer for applying over said first layer while said first layer is still soft and tacky, said second layer comprising a polyolefin tape material and of a minimum thickness of 0.6 mm.
7. The coating of claim 6, wherein the first layer forms a continuous coating from 0.25 mm to 0.5 mm (10 mils to 20 mils) in thickness and the second layer forms a coating at least 0.89 mm (35 mils) in thickness.
8. The coating of claim 7, wherein the second layer is the tape of polyolefin material, spirally wrapped over the first layer.
9. The coating of claim 8, wherein said polyolefin is polyethylene.
10. A coated metallic pipe having an improved corrosion and soil stress resistance coating, said pipe having an outer surface, said coating comprising:
a first layer comprising a hot-melt rubberized adhesive, applied to the precleaned, outer surface of the pipe when said outer surface is dry and at a temperature of 25°-60°C and at least 3°C
above the dew point temperature, the temperature of the preheated pipe and hot-melt adhesive in a range to allow the adhesive to flow and wet said surface and deposit a bonded layer on said pipe surface, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group consisting of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75° - 95°C
Flow properties, as defined by CSA Z 245.21 spec: 1-12 mm Viscosity at 175°C: 10,000 - 100,000 cPs; and a second layer having a minimum thickness of 0.6 mm comprising a polyolefin tape material applied over the first layer while said first surface is still soft and tacky.
a first layer comprising a hot-melt rubberized adhesive, applied to the precleaned, outer surface of the pipe when said outer surface is dry and at a temperature of 25°-60°C and at least 3°C
above the dew point temperature, the temperature of the preheated pipe and hot-melt adhesive in a range to allow the adhesive to flow and wet said surface and deposit a bonded layer on said pipe surface, said hot-melt rubberized adhesive comprising a physical blend or mixture of materials chosen from the group consisting of asphaltenes, elastomers, rubbers, resins, polymers and copolymers, optionally including fillers, said hot-melt rubberized adhesive having the following physical properties:
Ring and Ball softening temperature : 75° - 95°C
Flow properties, as defined by CSA Z 245.21 spec: 1-12 mm Viscosity at 175°C: 10,000 - 100,000 cPs; and a second layer having a minimum thickness of 0.6 mm comprising a polyolefin tape material applied over the first layer while said first surface is still soft and tacky.
11. A coated metallic pipe of claim 10, wherein the first layer forms a continuous coating from 0.25 mm to 0.5 mm (10 mils to 20 mils) in thickness and the second layer forms a coating at least 0.89 mm (35 mils) in thickness.
12. A coated metallic pipe of claim 11, wherein the second layer is the tape of polyolefin material, spirally wrapped over the first layer.
13. A coated metallic pipe of claim 12, wherein said polyolefin is polyethylene.
14. A coating according to claim 6 which has the following properties:
Adhesive Properties:
Softening Point (ring and ball) 85°C average Adhesive Flow Test (71°C, 1 h) 2 - 8 mm average Coating Properties:
Peel Adhesion at 23°C (Instron) Cross head speed 10 mm/minute 3.5kg/25mm average Peel Adhesion (hanging weight, per CSA Z245.21) 2.0 kg 5mm/min/25mm 2.5 kg 7mm/min/25mm 3.0 kg 10mm/min/25mm 3.5 kg 15mm/min/25mm Cathodic Disbondment (CSA Z.245.21) 28 days, 23°C, 1.5V 10 mm Radius 14 days, 65°C, 1.5V 8 mm Radius 48 hour, 65°C, 1.5V 6 mm Radius Impact Test, 23°C 4.0 J/mm Bend Test, CSA 2.245.21 No cracking Outdoor Exposure (ASTM B-53) 2 years min.
Polyethylene Tensile Strength 12 MPa Polyethylene Tape Elongation 200%
-----------------------------------------------------------Minimum coating thickness in millimetres (ails):
Diameter (in): 3 - 8 10 and up (mm): 89 - 219 273 and up Adhesive: 0.25 (10) 0.30 (12) Polyethylene:
one layer 0.89 (35 mils) 0.89 (35 mils)
Adhesive Properties:
Softening Point (ring and ball) 85°C average Adhesive Flow Test (71°C, 1 h) 2 - 8 mm average Coating Properties:
Peel Adhesion at 23°C (Instron) Cross head speed 10 mm/minute 3.5kg/25mm average Peel Adhesion (hanging weight, per CSA Z245.21) 2.0 kg 5mm/min/25mm 2.5 kg 7mm/min/25mm 3.0 kg 10mm/min/25mm 3.5 kg 15mm/min/25mm Cathodic Disbondment (CSA Z.245.21) 28 days, 23°C, 1.5V 10 mm Radius 14 days, 65°C, 1.5V 8 mm Radius 48 hour, 65°C, 1.5V 6 mm Radius Impact Test, 23°C 4.0 J/mm Bend Test, CSA 2.245.21 No cracking Outdoor Exposure (ASTM B-53) 2 years min.
Polyethylene Tensile Strength 12 MPa Polyethylene Tape Elongation 200%
-----------------------------------------------------------Minimum coating thickness in millimetres (ails):
Diameter (in): 3 - 8 10 and up (mm): 89 - 219 273 and up Adhesive: 0.25 (10) 0.30 (12) Polyethylene:
one layer 0.89 (35 mils) 0.89 (35 mils)
15. A method according to claim 1 wherein the hot-melt rubberized adhesive is preheated to a temperature of 150° to 175°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2121855A CA2121855C (en) | 1994-04-21 | 1994-04-21 | Metallic pipe corrosion and stress resistant coating |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA2121855A CA2121855C (en) | 1994-04-21 | 1994-04-21 | Metallic pipe corrosion and stress resistant coating |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2121855A1 CA2121855A1 (en) | 1995-10-22 |
| CA2121855C true CA2121855C (en) | 2010-12-21 |
Family
ID=4153429
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2121855A Expired - Lifetime CA2121855C (en) | 1994-04-21 | 1994-04-21 | Metallic pipe corrosion and stress resistant coating |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2121855C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2743330A1 (en) * | 1996-01-10 | 1997-07-11 | Atochem Elf Sa | COATING OF METAL SURFACES |
-
1994
- 1994-04-21 CA CA2121855A patent/CA2121855C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2121855A1 (en) | 1995-10-22 |
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