Apparatus and method for electroless nickel coating of tubular structures

Tubular structures, for example pipes, are coated at least in an interior thereof with a nickel containing coating via at least one distribution manifold with ports which are received in the interior of the tubular structure. An electroless nickel coating solution may be pumped or supplied via gravity feed to the distribution manifold. The tubular structure may concurrently be immersed in electroless nickel coating solution in a tank. A second distribution manifold may deliver electroless nickel coating solution to the interior of the tubular structure in an opposite direction from the first. The two distribution manifolds may be used as part of a support structure to lift or move the tubular structure. Additional tanks may hold other solutions, for instance cleaning solutions, etching solutions and rinses.

BACKGROUND

The present disclosure relates generally to coating metal pipes, and more particularly to applying a uniform coating to the interior of relatively long tubular structures.

2. Description of the Related Art

Electroless Nickel Coating (“ENC”) is a nickel plating process for chemically applying nickel alloy deposits onto metallic substrates using an autocatalytic immersion process without the use of electrical current. ENC is often applied to relatively short tubular components (e.g., 10-foot lengths), by dipping individual lengths of pipe vertically into a sump tank or bath with vertically spaced spargers to inject solution into the long body of the pipe. This conventional coating technology suffers a number of limitations including the depth of the sump bath and correspondingly the height of the ceiling of the workspace into which the treated body must be positioned. Similarly, it is difficult and time consuming, thus inefficient, to secure the tubular substrates in position vertically while changing them and replenishing the solution between batches. A further disadvantage of the conventional vertical dipping process for coating long tubular structures is the limited ability to control the distribution of the nickel solute so as to permit it to plate long curved surfaces uniformly. In many applications it is important that the nickel coating be uniform. Further, for applications in oil-producing regions, it is often necessary to use much longer tubular goods (e.g., 40-foot lengths). Accordingly, it is desirable to find a way to consistently apply uniform electroless nickel coatings over very long curved surfaces.

Typically, ENC is only applied to shorter lengths of pup joints, because existing processes fail to efficiently coat full length tubular joints with consistent results. The prior art in the ENC industry has concentrated on teaching variations on vertically oriented bath tanks and pipes, which disadvantageously requires deep tanks and a tall building to plate long pipes. See, e.g., U.S. Pat. No. 4,262,044 and U.S. Pat. No. 6,245,389.

BRIEF SUMMARY

A system for applying a uniform electroless nickel coating to the interior of a bundle of long pipes, each pipe having an inlet end and an opposing outlet end may be summarized as including at least one distribution manifold, having a number of injection nozzles, for injecting a fluid into one end of each pipe in said bundle, said end in fluid communication with said interior; a reservoir having a supply of electroless nickel coating solution fluidly coupled to a pump that is fluidly coupled to said distribution manifold; and recirculation means for repeatedly returning said coating solution to said reservoir until the desired thickness of coating is reached. The solutes of the chemicals are replenished from time to time to ensure certain levels of concentration.

A method of using ENC to uniformly plate long tubular structures such as full length OCTG (Oil Country Tubular Goods) sections of pipe and well (surface and production) casing uniformly and efficiently may be summarized as including a nickel coating distributing evenly on an inner surface of long tubular structures (e.g., pipes) by generating circulations inside the pipes. According to certain aspects, pipes may be placed in a bath horizontally. According to certain aspects, multiple pipes may be arranged in bundles and the bundles placed in the bath horizontally. According to certain such aspects, multiple pipes may be coated simultaneously. According to at least one aspect, pipes may be coated efficiently and uniformly at decreased cost.

DETAILED DESCRIPTION

Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, which is as “including, but not limited to.”

The term “tubulars” as used herein refers to tubular structures and includes tubing or piping having circular, rectangular, or other cross-sectional shapes and having lengths as appropriate. Lengths may, for example, extend to at least 40 feet or greater. Tubular structures, tubing, tubes, piping or pipes, including singular forms thereof, may be used interchangeably herein and in the claims.

A number of embodiments of apparatus, systems and methods for Electroless Nickel Coating (ENC) are described herein. The ENC apparatus and systems perform ENC on pipes or tubing, particularly oil country pipes or tubing. As disclosed herein, the pipes or tubing may be advantageously positioned horizontally during ENC. Such horizontal positioning may advantageously allow nickel coating of lengths of pipe or tubing substantially greater than is allowed by apparatus, systems and methods commonly used for ENC, during which pipes or tubing are positioned vertically. Further, ENC by the apparatus, systems and methods disclosed herein may provide uniform nickel coating on curved surfaces of the pipes or tubing that is more uniform than can be provided by commonly used approaches to ENC.

FIG. 1shows a system100for Electroless Nickel Coating (ENC) of long tubulars (circular, rectangular or other cross-sectional shapes). System100in the embodiment illustrated inFIG. 1shows a plurality of relatively long tanks105(only one called out in the Figure) positioned proximal one another to form a “tank farm.” Each tank105may have any cross-sectional shape or profile suitable for holding the tubular structures. Into each tank105a substantially horizontally positioned bundle110of full length tubulars112(only one denoted) may be immersed or drained. Due to the length and weight of a number of long metal pipes112, suitably strong straps or other form of clamps111(only one denoted) are used to form the pipes112into bundle110. The position of each tube within the bundle is further secured by any suitable spacers, wedges or similar means for this purpose (not shown).

Movement of bundles110of pipes112throughout the tank farm may be by any suitable means, for example without limitation clamp/strap/hook assembly118. Transport of bundle110of pipes112via assembly118to any location within the tank farm may utilize any available overhead crane or forklift or similar means for moving bundle110. Each tank in a treatment section of a farm contains a solution suitable for a given step in the ENC process. For cost and time efficiency, tubes112are preferably assembled into bundles110as discussed above. In the particular embodiment shown inFIG. 1, there are 7 tubes per bundle. However, size of the bundle may be varied and depends on available equipment and space, as well as production requirements. For example, in processing small orders of large diameter tubes one may choose to treat only 1 or 2 tubes at a time, whereas for large orders of smaller diameter tubes the system100may be used to treat 20 tubes or more at one time. By increasing tank size and lift capacity, even larger bundles may be assembled, then cleaned or coated together.

At least one tank contains a cleaning solution115, for example an acid wash suitable to effect a preliminary macro cleaning of each tube112in bundle110. Bundle110may preferably be dipped into cleaning solution115two or more times.

Another tank contains an appropriate rinse solution120, for example water or a solution of a suitable detergent in water. Once the tubes112are sufficiently acid cleaned in solution115for the particular coating specified, the tubes112are moved to a tank containing the rinse solution120. The tubes112may typically be immersed in the rinse solution120. In certain embodiments the tubes may preferably be immersed therein two or more times, as necessary.

A further tank contains an etching solution125appropriate for the particular coating process to be used in ENC. Once tubes112are sufficiently rinsed, the tubes112are moved to a tank containing the etching solution125in which the tubes112are immersed. Immersion of tubes112into etching solution125may be complete or partial, depending on the degree of etching required for a particular coating.

Yet a further tank may contain a second rinse solution130, for example water or a solution of a suitable detergent in water. Once the tubes112are sufficiently etched for the coating specified, the tubes112may be moved to and immersed in a tank containing an appropriate second rinse solution130. The second rinse solution130may, for example, take the form of water or a solution of a suitable detergent in water. The final rinse may preferably be performed in purified water, such as may be obtained by reverse osmosis treatment. Each of these acts carried out prior to the coating step(s) may typically be completed at room temperature (e.g., 60-70° F.).

The final tank according to the embodiment illustrated inFIG. 1contains coating solution150. The coating solution150may preferably be heated to a temperature suitable for the coating process. Intake lines181for distribution manifold180draw the heated coating solution150from one side of tank105to inject the heated coating solution150into tubes112such that the heated coating solution150passes through each tube112and discharges into the opposing side and/or end of tank105. Such ensures sufficient circulation and precipitative or other form of consumption of solute during the coating process permitting the bath of heated coating solution150to deplete in a manner that facilitates an even thickness of coating.

Cleaned, etched, and rinsed tubes112in bundle110are then ready for electroless nickel coating (ENC), the precise formulation of which coating solution150(preferably heated to a temperature in the range 80 to 99 degrees C.) depends upon the desired coating properties. The formulation of coating solution150depends on the desired properties of the coating to be applied to tubes112. In one embodiment, coating solution150is preferably heated to a temperature ranging between 80° C. and 99° C. In certain embodiments, tubulars need only be coated on their internal surfaces. In preparation for coating, external surfaces of such tubulars may be protected by wrapping in any suitable covering, e.g., a polymer tape or any suitable paint such as epoxy). The covering may prevent the exterior surfaces of the tubulars from reacting to or with the nickel ions in coating solution150.

Once any protective steps have been completed, the tubes112, individually or in bundles110as appropriate, are moved by any suitable means into a tank containing an appropriate nickel alloy coating solution150. The nickel solute concentration in the coating solution150is selected to achieve the desired thickness of coating of the surface area to be plated. In certain embodiments, the nickel alloy coating solution150may have a specific gravity of 1.14 and a viscosity of 0). In certain embodiments, the concentration of nickel solution in the coating solution150is selected to achieve a coating rate of 0.005 mm/hour-0.015 mm/hour on the surfaces of the tube(s) to be coated. In certain embodiments, the temperature of the coating solution150ranges between 80° C. and 95° C. In certain embodiments the concentration of nickel solute in the coating solution150is 30% or less. The temperature and chemical formulation of the coating solution150are established according to the expected end use of tube112and the coating properties required for that use. Prior to immersing tube bundle110into coating solution150, hoses170connected to distribution manifold180are fluidly coupled, by any suitable means, to either end of each tube112in bundle110.

According to one embodiment of the apparatus and system disclosed herein, each hose170is inserted into an end of each tube112. Distribution manifold180is fluidly coupled via input line181to a supply (typically pressurized, however it could be gravitationally fed) of nickel alloy solution corresponding to coating solution150. The supply may be fed gravitationally or further pressurized. The coating solution150may be supplied from or circulated through a reservoir185. The coating solution150may be circulated through the tubes112and tank105by being steadily driven by any suitable pump (not shown) fluidly coupled to reservoir185and operated at a flow rate sufficient to circulate coating solution150through tank105. Circulation through the system may be at a rate of 15 to 30 times per hour, thereby keeping the coating solution150well mixed and sufficiently uniform in concentration, thus helping to provide an even coating on the relatively long curved surfaces of the tubes112being plated. Circulation of the coating solution150within the system may occur by gentle backwash or recirculation. In certain embodiments, flow of coating solution150within the tubes112during coating is preferably laminar flow rather than turbulent flow to more uniformly provide coating solution to the surfaces to be coated. In certain further embodiments, bundle110may be gently rotated, e.g., driven by any suitable rotisserie-like motor means, to more uniformly provide coating solution to the interior surface of each tube112. The particular flow rate selected depends upon the specifications of the coating type and thickness. The deposition rate of a given nickel alloy is influenced by a number of factors including the nozzle pressure at hose170and the related velocity with which the nickel alloy coating solution150passes over the interior surface of each tube112.

Upon completion of coating and depletion of solute from coating solution150, bundle110of the now nickel alloy-coated tubes112is removed from coating solution150and allowed to cool to near room temperature. The bundle110of tubes112is then again rinsed in pure water, typically dipped three times for a few seconds each time. According to one embodiment, the tubes are then exposed to the air at room temperature for approximately 1 minute for passivation. Passivation refers to a process of making the coating “passive” by spontaneous formation of a hard surface film, usually an oxide or nitride, a few atoms thick, on the surface of the coated and rinsed tubes112in bundle110. Passivation seals cracks or pinholes in the coating, which helps maintain surface hardness, improves surface glare, and increases the life span of the surface coating.

According to another embodiment, where additional surface coating hardness is required, bundle110of tubes112, after coating, is subjected to heat treatment via baking. In certain embodiments, baking of the tubes112is performed at a temperature between 300 and 400° C. for 1 to 3 hours. In certain embodiments, the temperature and time may be varied inversely. Upon completion of baking, the bundle110of tubes112is allowed to cool at room temperature (in air) to permit the coating bonds to stabilize and tube surfaces to anneal, thus increasing the hardness of the coating. It is to be understood that a person of ordinary skill in the art of heat treatment would know to set the particular temperature and time in accordance with the specified hardness required in the tubes112in use. The tubes112are typically cleaned (e.g., rinsed) one final time before packing for shipping.

FIG. 2shows an alternative embodiment of distribution manifold180, denoted generally as200, comprising manifold reservoir205, a suitable number of filler nozzles210(only one denoted), end cap220, inlet225, and support member230. Optional collar215slidingly coaxially engages reservoir205with the inner diameter of collar215sized to closely receive and accommodate the outer diameter of reservoir205. Whereas filler nozzles210are provided in sufficient number for supplying each tube112in bundle110and are each externally sized for close reception by the interior of their corresponding tube112. Collar215may advantageously be slidingly moved away from full engagement with reservoir205to be positioned around the exterior of the entire bundle110, thereby permitting apparatus200to also provide mechanical support for holding and lifting bundle110, in addition to or as an alternative to clamps111denoted inFIG. 1.

Reservoir205may be any suitable shape, dimensions and capacity applicable to deliver the specified coating solution to the particular number of tubes112comprising the particular bundle110used in a particular application of embodiments of the system disclosed herein. Similarly, filler nozzles210are provided in sufficient number and of a size that corresponds to the shape and dimensions of the tubulars being coated. Further, filler nozzles210may be constructed from a material and in a manner providing enough strength to permit apparatus200to support an end of bundle110. However, when used with alternate means for supporting the ends of a bundle (e.g. using clamps111), filler nozzles210may be constructed from a light weight material (e.g. stubs of hose170) that directs solution into each tube112without providing means to either maintain or lift a bundle of tubes of any size.

Regardless of the capacity of distribution manifold apparatus200to maintain the relative position of tubes112in a bundle110, according to a preferred embodiment of the apparatus, advantageously there is provided a removable end cap220that is removably fastened (by any suitable means) to the opposing end of reservoir205. Such permits periodic cleaning and allows an operator to leave apparatus200in place while changing the solution being supplied to bundle110. Whether threaded, slip fit and bolted or riveted—or otherwise sealed to one end of reservoir205, end cap220(having any suitable inlet225provided therein) permits the rapid, seamless change out of supply lines both feeding and draining cleaning or treatment solutions to, or from, bundle110.

According to one embodiment of distribution manifold apparatus200that both maintains the shape of bundle110and permits an operator to move that bundle throughout a tank farm, support member230both facilitates the installation of apparatus200into each end of a bundle110and permits that bundle to be secured to any suitable lifting means.

FIG. 3shows a system300, according to an alternative embodiment. In the system300, each distribution manifold200serves more than one purpose and system300. Accordingly to this embodiment, bundle110is assembled with a clamp111and suitable spacer positioned approximately mid-length along the bundle. Then, typically handling one end at a time, a pair of distribution manifolds200are inserted into opposite ends of the bundle110of tubes112. The distribution manifolds200are fastened to support beam310to add rigidity and to obtain control over the bundle. End caps220need not be installed during bundle-to-beam assembly. Once the distribution manifolds, tubes, clamps, and support beam are all connected, bundle110may be processed through the tank farm for: cleaning, etching, rinsing, coating, and rinsing as required for the product sought. Advantageously, whenever only the interior of tubes112is being treated, system300may be configured to complete the process without the need for dipping and immersion into the tanks105. Tanks105may instead act as alternate reservoirs holding the different cleaning, rinsing, etching, coating and other solutions. Such solutions may be pumped only through tubes112, then either recirculated to the same reservoir until the solute is depleted, or to an intermediate reservoir where the concentration of the solution may be monitored and reconditioned or disposed of accordingly.

According to the embodiment illustrated inFIG. 3, one distribution manifold apparatus200is connected to each end of tubes112in bundle110to permit bi-directional flow and the interchangeability of supply tanks185a,185b. As illustrated, lifting support beam310provides a slot315in each end for closely accommodating support member230(denoted inFIG. 2) through which any suitable pin316may be removably inserted so as to releaseably fasten each apparatus200(and bundle110situated between them) to support beam310for movement throughout the tank farm. As shown, solution from supply tank185amay be supplied to bundle110through supply line145aand permitted to flow back into tank105via supply line145b. Supply line145bmay alternately be connected for recirculation to inlet/outlet330of supply tank185band vice versa. Advantageously, system300permits the ENC treatment process to be completed using a smaller tank farm with fewer operations whenever immersion can be avoided. It is contemplated that a siding and hinged configuration of apparatus200could be connected to support beam300together with a center grapple320so as to facilitate more automated processing of bundle110. Such would allow an operator to slide each tube112into place over injection nozzles210on one end and then operate the hinge and slide on the opposing distribution manifold apparatus200, causing all injection nozzles210on that opposing end to simultaneously engage and become fluidly coupled to that end of their respective tubes112. This same embodiment contemplates a reservoir205(together with its injection nozzles210and collar215) that rotates inside a fixed sleeve (not shown) to which the hinged sliding subassembly is coupled for connection to support beam310. This rotating distribution manifold embodiment causes the entire bundle110to rotate gently while solution is being circulated through the interior of each tube112ensuring an even coating.

Although the disclosure describes and illustrates various embodiments, it is to be understood that these particular embodiments are provided without limitation. As a direct result of this disclosure, variations and modifications will now occur to those skilled in the art of Electroless Nickel Coating for longer tubulars. The various embodiments described above can be combined to provide further embodiments. To the extent that they are not inconsistent with the specific teachings and definitions herein, all commonly assigned U.S. patents, U.S. patent application publications, U.S. patent applications, referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary, to employ structures and concepts of the various patents and applications to provide yet further embodiments.