FIELD

[0001] The invention relates to a device and a method for coating an impinged concrete coating on a pipe, and a pipe having a coated concrete coating.

BACKGROUND

[0002] Typically, an impingement process is used for offshore concrete coating of a pipe. The process involves continuously mixed material passing through two large rubberized rollers at high speed onto the pipe to build up the required concrete thickness. The impingement process creates a surface which is uneven (non-uniform), rough and undulating due to a number of reasons, including variations in the mass of the feed delivered to the rollers, rebound, surface fall-off, concrete dryness, aggregate particle size, and lack of surface compaction. Typically, the pipe is moved to a curing area (fog or steam) for 12-16 hours, to allow for the concrete to be cured in a controlled environment (to prevent moisture loss and for temperature control), which can otherwise lead to a brittle concrete product, fine cracking on the concrete and lower ultimate compressive strength.

[0003] The non-uniform surface of the concrete appears rough with a lot of loose material which would reduce the accuracy of the outer diameter measurement which may result in a lower density calculation compared to the actual. Decreasing the variation in the surface profile can allow for a more accurate measurement of the outer diameter - either the mass of concrete or the amount of iron ore in the concrete can be decreased to obtain the desired negative buoyancies.

[0004] In addition to the above, the non-uniform surface formed from an impinged concrete coated pipe leads to dust generation during the process of handling and laying the pipe. The impinged concrete surfaces shed a significant amount of fine concrete material because the outer surface is friable. Lay barge operators incur significant and undesirable costs disposing of dust and detritus generated by impinged concrete. It would be desirable to provide a concrete coated pipe that will generate less dust and detritus and reduce disposal costs for the lay barge operators.

[0005] Dust and detritus generated by pipe handling of concrete coated pipes creates a significant inconvenience, cost, and health risks to pipe handlers. Such health risks include eye irritation, dry skin, and other issues. The dust and detritus also increase the wear and tear of expensive

equipment on the pipelaying vessels, which require constant cleaning, and creates significant disposal costs for the pipelay contractors. It is estimated that up to 40 kg of dust and detritus can be generated from a single 12 m long concrete coated pipe during the process of handling and laying the pipe.

[0006] Solutions to reducing dust and detritus on a concrete pipeline are known. The primary option is to use wrap-on or molding process to produce the concrete coated pipes with the smoother surface. The most significant disadvantage of using these methods is the slow production rates (when compared with impinged process) which will ultimately delay the pipe installation process. Also, the handling of pipes will increase significantly in case of molding method which will enhance the HSE concerns. The wrap on process uses an outer polyethylene layer to hold the concrete and protect the moisture from evaporation but, the plastic needs to be removed before the pipes are shipped for installation. The cost and environmental impact, in addition to the slower throughput prompts the use of the impingement process. There are various means known in the art that can be used to reduce the dust production when handling the impingement concrete coated pipes. These include finishing the concrete coating with a vibrating finishing plate technology, as described in PCT/CA2012/050452, incorporated herein by reference, and by utilizing one or more finer aggregates in the concrete mix, to increase the uniformity of the surface of the concrete coating and to reduce the size of the loose material on surface of concrete weight coated pipes. While these methods are excellent at reducing the amount of dust and detritus, further reductions or complete elimination are desirable.

[0007] Hence, there is a need in the art for a process for decreasing the dust and detritus formed from impinged concrete during the handling and laying the pipe.

SUMMARY OF THE INVENTION

[0008] According to one aspect of the present invention is a concrete weight coated pipe, comprising a concrete coating and a thin surface coating overtop of said concrete coating.

[0009] In certain embodiments, the thin surface coating is a polymeric coating.

[0010] In certain embodiments, the surface coating is an epoxy, a polyurea, a primer, a polyurethane, and/or a hybrid polyurea or

polyurethane.

[0011] In certain embodiments, the thin surface coating is between 2 and 40 mils in thickness.

[0012] In certain embodiments, the thin surface coating is thicker than 40 mils.

[0013] In certain embodiments, the concrete coating has been vibrationally or non-vibrationally finished using a finishing plate.

[0014] In certain embodiments, the concrete coating further comprises fine aggregate, for example, with a maximum particle size of 6.3 mm within the concrete coating.

[0015] According to another aspect of the present invention is provided a method of manufacturing a concrete weight coated pipe, comprising :

applying an anti-corrosion coating to a steel pipe; impinging a concrete weight coating overtop of the anti-corrosion coating; applying a thin surface coating overtop of the concrete coating; and allowing the concrete coating to cure.

[0016] In certain embodiments, the thin surface coating is applied by spraying.

[0017] In certain embodiments, the thin surface coating is applied in line with the impinging of the concrete coating.

[0018] In certain embodiments, the step of allowing the concrete coating to cure occurs before spraying the thin surface coating.

[0019] In certain embodiments, the step of allowing the concrete coating to cure occurs after spraying the thin surface coating.

[0020] In certain embodiments, the step of allowing the concrete coating to cure occurs in ambient conditions and not in a fog cure area.

[0021] In certain embodiments, the step of allowing the concrete coating to cure occurs in a fog cure area.

[0022] In certain embodiments, the method comprises vibrationally finishing the concrete coating before application of the thin surface coating.

[0023] In certain embodiments, the thin surface coating is a polymeric coating.

[0024] In certain embodiments, the surface coating is an epoxy, a polyurea, a primer, a polyurethane, and/or a hybrid polyurea/polyurethane.

[0025] In certain embodiments, the surface coating is applied to a thickness of between 2 and 40 mils.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Reference will now be made, by way of example, to the accompanying drawings which show example embodiments of the present application, and in which : [0027] Figure 1 is a schematic longitudinal cross sectional non-scale representation of a concrete coated pipe section of the prior art.

[0028] Figure 2 is a schematic longitudinal cross sectional non-scale representation of a concrete coated pipe section of the present invention.

[0029] Figure 3 shows results of testing of material loss after gouging a lab produced sample emulating a pipe section of the present invention, as compared to prior art pipe section.

[0030] Figure 4 shows photographs of the pipe sections (4A) and material loss (4B) after gouging a lab produced sample emulating a pipe section of the present invention, as compared to prior art pipe section.

[0031] Figure 5 shows results of testing of material loss after multiple runs of gouging a lab produces sample emulating a pipe section of the present invention, as compared to prior art pipe section.

[0032] Figure 6 shows a photograph of a coated pipe of the present invention.

[0033] Similar reference numerals may have been used in different figures to denote similar components.

DESCRIPTION

[0034] The invention relates to a pipe coating process, a pipe coating, and a concrete coated pipe having such a coating.

[0035] It has been found that applying a thin polymeric surface coating overtop of an impinged concrete coating will significantly reduce or completely eliminate the dust and detritus coming off of said pipe during pipe handling and laying. The thin polymeric surface coating can be applied immediately after the impinged concrete coating application, without affecting the concrete coating curing cycle. The thin polymeric surface coating has been also found to aid in concrete coating curing, if it is applied before the concrete has cured, by preventing moisture loss from the concrete. Thus, it has been found that applying a thin polymeric surface coating overtop of the concrete coating can decrease or eliminate the need for a curing area to prevent moisture loss from the freshly applied concrete coating, which can significantly decrease handling and cost during the pipe coating process.

[0036] In short, the thin polymeric surface coating can be added at any step in the pipe manufacturing or shipping process. For example, it can be added to the impinged concrete in-line with the impingement process. It can be added shortly after the impingement process, on a separate line, before moving the pipe to a concrete curing area. It can be applied as a separate step, post-cure. Optionally, the thin polymeric surface coating can be applied to the cured concrete as part of the load-out process, to minimize pipe handling steps.

[0037] Figure 1 shows a schematic, longitudinal cross-sectional view of a typical concrete coated pipe of the prior art. The layers of the pipe, and the dimensions of the pipe, are not shown to scale. It should be noted that this is but one configuration of a concrete weighted pipe; other

configurations, with larger pipe diameter and thicker concrete, are also known; the present invention is applicable to any of these configurations, so long as the pipe segment contains an exposed concrete weight coating.

[0038] Pipe 10 comprises a bare steel pipe 12, which is coated in a thin corrosion resistance coating 14, which is often a fusion bonded epoxy (FBE) or asphalt enamel coating. When the corrosion resistance coating 14 is FBE, it may be a dual layer coating, for example further coated with a gouge resistance coating 16, which is typically a polyolefin coating, for example, polyethylene or polypropylene or a dual layer fusion bond epoxy coating. A tie layer or a concrete weight coating 18 is applied to the gouge resistance coating 16, typically through an impingement process. In the figures, concrete weight coating 18 is denoted in a dashed line, to illustrate that the exterior surface of this coating is typically rough and uneven. [0039] The concrete coated pipe as illustrated in Figure 1 is typically made in a factory and not on site. The fusion bonded epoxy coating

(corrosion resistance coating 14) is typically spray coated onto the bare steel pipe 12, which has been cleaned and typically blasted or acid treated to remove rust immediately prior to coating. The corrosion resistance coating 14 may also be applied by brush or roller. Gouge resistance coating 16 is typically extruded overtop of the corrosion resistance coating 14, with the concrete coating 18 impinged onto the gouge resistance coating 16.

Typically, each layer of coating is allowed to cure or set (as appropriate) before the application of the next layer. Typically, after application of the concrete coating 18, the pipe is moved to a curing area (fog or steam) to prevent moisture loss and for temperature control.

[0040] Optionally, the concrete coated pipe may be finished and/or smoothened, to reduce the surface roughness in order to decrease thickness variability and decrease dust formation during handling and laying. This may be done through various means known in the art, including the vibrating plate technology described in PCT/CA2012/050452, incorporated herein by reference, or by using a finer aggregate in the concrete mix.

[0041] Another example of a concrete weight coated pipe is a two- layer pipe coating. The steel pipe is cleaned and blasted, and an asphalt anti-corrosion layer is applied. The concrete is then impinged directly onto the asphalt.

[0042] Figure 2 shows a schematic longitudinal cross-sectional view of a concrete weight coated pipe of the present invention. Like the prior art pipe, pipe 10 comprises of a bare steel pipe 12, coated in a thin corrosion resistance coating 14, further coated with an gouge resistance coating 16, onto which a concrete weight coating 18 is applied. Each of these layers of pipe are manufactured and applied to the pipe using conventional, prior art means. The concrete coating may be finished and/or smoothed, as previously described. Like Figure 1, the pipe of Figure 2 is not shown to scale. [0043] As shown in Figure 2 (and as a photograph in Figure 6), pipe 10 comprises a thin surface coating 20 overtop of the concrete coating 18. The thin surface coating 20 may be an organic coating. The thin surface coating 20 may be a polymeric coating, for example, an epoxy, epoxy / mortar blend, a polyurea, a primer, a polyurethane, or a hybrid

(polyurea/polyurethane). For example, the surface coating 20 may be a polyuria/polyurethane hybrid such as Elastocoat 95540R BLK, (BASF), an epoxy such as MasterTop GP500 (BASF), a clear polyurea such as Elastocoat S71180, or a primer such as Skytite A-1601 Primer. The surface coating 20 may be, for example, a two part solution, a powder coated single or two part powder, or a single solution. The thin surface coating 20 may also be an inorganic coating.

[0044] It has been found that a surface coating 20 as thin as 5 mil in thickness dramatically and significantly decreases material loss and dust formation from the concrete coating. Surface coating 20 may be from 2 to 40 mils, for example, 5 mils, 10 mils, 15 mils, 20 mils, or 40 mils, with thicker applications providing improved performance.

[0045] It has also been found that the surface coating 20 may be applied on "green" concrete - i.e. concrete that has not yet cured. For example, the surface coating 20 may be applied overtop of the concrete coating 18 immediately or shortly after the impingement process. The surface coating 20 may thus be applied in-line in a factory environment. In certain embodiments, the surface coating 20 has an extremely fast curing time, for example 5-8 seconds, which is extremely advantageous and allows immediate handling of the pipe 10. Where a surface coating 20 has been applied onto a green concrete, due to its rapid curing time and other properties, it has been found to substantially "trap" the moisture within the concrete, allowing for concrete curing to take place in a normal ambient environment, and reducing or eliminating the need for a "fog curing area" i.e. a high humidity controlled environment in which the concrete is left to cure. This may, in many instances, significantly reduces handling

requirements of the pipe (since the pipe does not need to be moved into and out of the fog area for curing) and decrease manufacturing costs, HSE issues and factory size.

[0046] The surface coating 20 may be powder coated or spray coated onto the concrete coating 18 of the pipe 10.

DESCRIPTION OF EXAMPLE EMBODIMENTS

[0047] The application will be described by way of the following, non limiting example.

[0048] A concrete weight coated pipe was made as follows. A 40 foot long, 36 inch outer diameter steel pipe was sand blasted, cleaned, and heated. A 6 mm asphalt corrosion coating was applied to the steel pipe. Plastic spacers (65 mm) positioned the 8 mm rebar cage in the middle third of the 110 mm concrete coating. Eight strands of fibrillated polypropylene twine were wrapped around the pipe to restrain the concrete and prevent disbondment or fall-off. The twine stands are typically positioned within the first 10 mm of the concrete surface and approximately 5 kg of tension was applied on each strand of twine.

[0049] A concrete mixture with a target density of 3040 kg/m ³ was used. The range of moisture content acceptable for coating was 4.5 to 6%.

[0050] For the diameter of pipe and concrete thickness used in this test program, the coating time and surface speed selected were 165 seconds and 72 meters/minute, respectively. The impingement resulted in a 4 inch concrete weight coating.

[0051] A polyurea hybrid (Elastocast 95540R BLK) was spray applied overtop of the green (uncured) concrete, to a thickness of 5 mil. Other identically manufactured pipes, were spray coated overtop of the green (uncured) concrete to a thickness of 10, 20 and 40 mils. The coating cured in approximately 5-6 seconds. The pipe was then set aside for 12-16 hours to allow the concrete to cure. Some pipes were also stored under ambient condition without fog cure to evaluate the effect on compressive strength.

[0052] Coated coupons were tested utilizing a modified Gouge tester, used to determine the gouge resistance as applied on pipelines. A dead load of 40 kg was applied onto a gouging pin, as well as onto a rounded steel tip (to better simulate the action rollers would have on a concrete coated pipe). The coupons were gouged for two inches in the longitudinal direction of the coating, and material loss for each sample type was recorded. The 5 mil coating showed a 94% reduction in material loss, as compared to a control (uncoated, concrete coupon). The 10 mil coating showed a 99% reduction in material loss, whereas the 20 and 40 mil coatings both showed zero material loss. (Figure 3). Photos of the coupons sections after the gouge tests, and bags containing the material loss, are shown in Figure 4A and B,

respectively.

[0053] Results were extrapolated to theoretically approximate the potential weight loss from a 36" pipe on two rollers, assuming a similar force is applied onto the concrete from the pipe. This resulted in a material loss from the bare concrete surface (control) of approximately 2.20 kg, compared to 0.13 kg for the 5 mil coated pipe, 0.02 kg for the 10 mil coated pipe, and 0 material loss from the 20 and 40 mil coated pipes.

[0054] The coupons lengths were further tested for multiple runs of gouging, utilizing the 10 mil coated coupons; the samples were run back and forth 6 times over the same line. Results showed significantly less material loss in the coated samples even after 6 runs (Figure 5).

[0055] Concrete coated pipes with a smoother surface profile, for example, where finer aggregates and/or a vibrating finishing plate step, can also be tested in a similar manner. For example, a 40 foot long, 36 inch outer diameter steel pipe can be sand blasted and cleaned. A 6 mm asphalt corrosion coating can be applied to the steel pipe. Plastic spacers (65 mm) can be positioned the 8 mm rebar cage in the middle third of the 110 mm concrete coating. Eight strands of fibrillated polypropylene twine can be wrapped around the pipe to restrain the concrete and prevent disbondment or fall-off. The twine stands can be positioned within the first 10 mm of the concrete surface and approximately 5 kg of tension can be applied on each strand of twine.

[0056] A concrete mixture with a target density of 3044 kg/m ³ can be used. The range of moisture content acceptable for coating can be 4.5 to 6%.

[0057] The coating time and surface speed selected can be 165 seconds and 72 meters/minute, respectively, and can result in a 4 inch concrete weight coating.

[0058] A vibrating finishing plate of 540 mm wide x 500 mm long can be used. Two Dynapac ER 305 electric vibrators can be used. The vibrators can be mounted parallel to each other on the plate at opposite ends of the plate. The rotors in the vibrators can be operated at a fixed speed of 3000 rpm and the internal weights can be set for the maximum force of 3000 Newtons. The vibrators were electrically connected such that the rotors inside the vibrator were counter rotating with respect to each other - one shaft rotated clockwise and the other anti-clockwise - this produced a reciprocating motion that was predominantly normal to the surface of the concrete. A 100 mm diameter pneumatic cylinder can be used to apply a static pressure to the plate, for example, with a maximum pressure of 101.5 psi and an estimated static thrust force on the plate of 3 psi. The vibrating finishing plate can be mounted just in front of the impingement rollers and in line with the scraper. The scraper and VFP can contact the pipe at approximately 28° before and after top-dead-center, respectively. [0059] A epoxy such as MasterTop GP500 can be spray coated overtop of the green (uncured) concrete, to a thickness of 5, 10, 20 or 40 mil. The coating can be then allowed to cure and the pipe set aside for 12- 16 hours to allow the concrete to cure.

[0060] In this manner, coating was applied onto 2 cured 36 inch, concrete coated pipes, both with and without smoothing with a finishing plate prior to coating. Pipes were cured both in a fog cure area as per standard practice, and with no fog curing applied. The 7-day core results showed that the pipe with no fog curing applied had a compressive strength of 42 MPa, whereas the pipe placed in the fog cure had a strength of 39 MPa, indicating the surface coating was effective in holding moisture inside the concrete.

[0061] In one embodiment, the spray coating of the epoxy occurs "in line" with the concrete impingement process, allowing for minimal additional pipe handling. A coating system as described in WO 2017/214724

(incorporated herein by reference), or a modification thereof, may be used for such in-line coating. Such a spray apparatus system can comprise a carriage which is configured to rotate around the pipe as the pipe is moved laterally through said apparatus. The carriage may comprise two cartridges, each containing one component of a two component epoxy. Alternatively, the coating system may be a spray tip, be connected via two separate heated hoses with the nozzles meeting at the spray tip, to an external source of said two component epoxy, as described for example in

www.araco.com/content/dam/araco/tech documents/manuals/332/332144/ 332144EN-G.pdf (incorporated herein by reference). The apparatus has means to displace the epoxy out of said cartridges (or from said external source through said tubing) into a static mixer, then out of said static mixer and through a spray head or nozzle. In a preferred embodiment, the apparatus is an airless apparatus, meaning that the epoxy is displaced, for example, utilizing motorized pistons or a high pressure pump, rather than pressurized air. The mixed epoxy is sprayed onto the concrete coating of the pipe as the carriage rotates around the pipe, and as the pipe moves laterally, through the apparatus, to form a relatively thin, relatively uniform, coating. Alternatively and in most applications, the spray nozzle is stationary or moves along the length of the pipe, while the pipe rotates (typically at 3-4 rpm) and optionally is displaced laterally with respect to the spray nozzle.

[0062] In certain embodiments, rather than being configured in-line with the impingement process, the spray coating apparatus may be a separate, stand-alone unit, to which the pipe is transported shortly after application of the concrete coating. Or, the spray coating apparatus may be in the fog area, and the coating can be applied at any time, for example, after the concrete coating has cured, in a separate step. In certain embodiments, the pipes can be coated before or after inspection during the loadout, with the coating performed as part of the load-out process. [0063] Certain adaptations and modifications of the described embodiments can be made. Therefore, the above discussed embodiments are considered to be illustrative and not restrictive.