Patent Publication Number: US-2021164600-A1

Title: Pig routing insert adapted for installation in a structure, structure and method

Description:
FIELD OF THE INVENTION 
     The object disclosed herein refers to a new design for the manufacture and installation of a pig routing insert at the intersection of at least two holes defined in a body with a block structure. The pig routing insert is used in order that the pig, as used for cleaning and unblocking machined holes or pipes within the structure, may not to be damaged and not enter unwanted pipes or holes. 
     BACKGROUND OF THE INVENTION 
     Fluid flow passage and pipe systems, used in several types of equipment employed in oil and gas industries, are frequently blocked by dross and other undesirable substances generally present in fluid extraction, production and transport processes. For example, hydrates, which are one of the biggest enemies of oil exploration, are formed under conditions of low temperature and high pressure, which are customary in the environment of subsea oil transmission lines. Removing hydrates from fluid flow passages and piping systems is just one of several situations in which pipe cleaning and unblocking systems are very important in this sector. A clogged fluid transport line can interrupt the entire production chain, causing major losses for companies in the field and end consumers. 
     As those skilled in the art know, the current state of the art describes a variety of methods directed to clean and unblock fluid flow passage and pipe systems, such as tools to heat pipe walls, vibrating devices and use of cleaning pigs and, as a last resort, replacing the clogged section of the tube or the flow line. 
     The use of cleaning pigs is one of the preferred methods in the industry, considering that its use, on many occasions, does not completely interrupt the production, which means reduced loss in the production process. Pigs are devices that are generally made of elastomeric materials with a high strain capacity. It is noted that, less frequently, other materials are used, such as metals, although they are less appropriate. In general, the pig has a cylindrical or spherical shape, or it can also consist of several discs connected by a metal or plastic shaft. 
     Cleaning and unblocking process is carried out in a simple way. After being inserted into the tube, a certain pressure is imposed on the pig by means of a gas or liquid, pushing it to its route inside the pipes or fluid lines, removing obstructions and cleaning the pipes. An important factor is to offer mechanisms to make the pig pass through the pipes to be cleaned in a desired route. For equipment, for example, as a manifold composed of welded and angled pipes, it is important that the project includes maintenance by using pigs, which must not deviate from the desired cleaning route to be carried out. For this purpose, pig blocking structures are installed in such welded pipes to ensure that the pig does not enter into unwanted pipes or is lost. In welded pipes, the installation of pig blocking structures is simple, since the pig blocking structure or the pig routing insert or drain can be easily welded at the end of a line. 
     In a machined block manifold, said pig blocking structures cannot be installed, since a block manifold structure is generally manufactured by a single process in which fluid flow passages or perforations or fluid flow holes are perforated (i.e. machined) into the solid body of the machined block manifold. Specifically, in such manifolds in machined blocks, there are no individual exposed pipes or tubes that allow the installation of pig blocking structures at the end of the pipes or tubes, as in conventional ones, which are composed of such welded pipes or tubes. 
     Therefore, the present patent application is addressed to a pig routing insert that is adapted to be positioned at the intersection of at least two holes defined in a body of a structure, such as a machined block manifold. 
     SUMMARY OF THE INVENTION 
     The following is a simplified summary of the object disclosed herein in order to provide a basic understanding of some aspects of the information disclosed herein. This summary is not an exhaustive overview of the revealed object. It is not intended to identify key or critical elements of the described object or to outline the scope of various embodiments disclosed herein. Its only purpose is to provide some concepts in a simplified manner, as a prelude to the more detailed description, which will be discussed further ahead. 
     An illustrative pig routing insert disclosed herein comprises an insert body which is adapted to be positioned at an intersection of at least two fluid flow perforated holes defined in a body of a structure, a substantially unrestricted flow opening defined in the insert body which is adapted to allow a substantially unrestricted fluid flow through the substantially unrestricted flow opening and a partially restricted opening defined in the insert body comprising at least one pig blocking structure positioned within the partially restricted opening, wherein the partially restricted opening is adapted to allow substantially unrestricted fluid flow through the partially restricted opening whilst blocking the passage of a cleaning pig through the partially restricted opening. 
     An illustrative structure disclosed herein comprises a body including at least first and second perforated fluid flow holes or passages that meet at an intersection within the body and a pig routing insert positioned at the intersection in the body. In this example, the pig routing insert comprises an insert body, a substantially unrestricted flow opening extending through the insert body, the substantially unrestricted flow opening being in uninterrupted communication with the first perforated fluid flow hole or passage so as to allow substantially unrestricted fluid flow from the first perforated fluid flow hole through the substantially unrestricted flow opening and a partially restricted opening defined in the insert body comprising at least one pig blocking structure positioned within the partially restricted opening, wherein the partially restricted opening is in uninterrupted communication with the second perforated fluid flow hole so as to allow the substantially unrestricted fluid flow from the second perforated fluid flow hole or passage through the partially restricted opening whilst blocking the passage of a cleaning pig through the partially restricted opening. In this specific example, the structure also comprises a first lining that is formed on an inner surface of the first perforated fluid flow hole or passage and a second lining that is formed on an inner surface of the second perforated fluid flow hole or passage. 
     Also disclosed herein is a new method comprising manufacturing a pig routing insert comprising a substantially unrestricted flow opening defined in the insert body, wherein the substantially unrestricted flow opening is adapted to allow a substantially unrestricted fluid flow through the substantially unrestricted flow opening and a partially restricted opening defined in the insert body comprising at least one pig blocking structure positioned within the partially restricted opening, wherein the partially restricted opening is adapted to allow substantially unrestricted fluid flow through the partially restricted opening whilst blocking the passage of a cleaning pig through the partially restricted opening. In this example, the method also comprises positioning the manufactured pig routing insert at an intersection of the first and second perforated fluid flow holes or passages previously formed in a body of a structure and, subsequently, fastening the manufactured pig routing insert within the intersection in the body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain aspects of the object disclosed herein will be described in reference to the attached drawings, which are representative and schematic and are not intended to be limitative, in any respect, to the scope of the object disclosed herein: 
         FIG. 1  is a detailed view of an illustrative embodiment of a pig routing insert showing illustrative examples of pig blocking bars according to several aspects disclosed herein; 
         FIG. 2  shows two illustrative examples of pig routing inserts disclosed herein and their respective illustrative pig blocking bars; 
         FIG. 3  is a perspective sectional view of an illustrative embodiment of a machined block manifold that shows illustrative examples of the various pig routing inserts installed therein; 
         FIG. 4  is a detailed view of another illustrative embodiment of a pig routing insert disclosed herein, wherein the pig routing insert is positioned at the location where multiple fluid flow holes or passages intersect within the machined block manifold; 
         FIG. 5  shows an illustrative embodiment of a method disclosed herein that can be used to install the pig routing insert in a machined block manifold; 
         FIGS. 6A-6C, 7A-7C, 8A-8C, 9A-9C, 10A-10C, 11A-11C, 12A-12C, 13A-13C, 14A-14C and 15A-15C  are several views that show, further in more detail, an illustrative embodiment of a method disclosed herein that can be used to install a pig routing insert in a machined block manifold; and 
         FIG. 16A-16E  are several views of an illustrative embodiment of a pig routing insert disclosed herein comprising a curved flow path that extends at least partially through the pig routing insert. 
       Although the object revealed herein is liable to several amendments and alternative forms, its specific embodiments were shown by way of example in the drawings and are described in detail herein. It should be understood, however, that the description provided herein of the specific embodiments is not intended to limit the revealed object to the specific forms revealed, but the intention is rather to encompass all amendments, equivalents and alternatives that fall within the spirit and scope of the described object as defined by the attached claims. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Several illustrative embodiments of the revealed object are described below. For the sake of clarity, not all features of an actual embodiment are described in this specification. Naturally, it will be appreciated that, in the development of any actual embodiment, several specific embodiment decisions must be made to achieve the specific objectives of the inventors, such as observing system-related and business-related restrictions, which vary from one embodiment to another. In addition, it will be appreciated that such a development effort can be complex and time consuming, but it would nevertheless be a routine task for those skilled in the art with the advantage of this disclosure. 
     The present object will now be described in reference to the attached figures. Various structures, systems and devices are represented schematically in the drawings for the purpose of explanation and not to obscure the present disclosure with details that are well known to those skilled in the art. However, the accompanying drawings are included to describe and explain illustrative examples of the present disclosure. The words and expressions used herein must be understood and interpreted as having a meaning consistent with the understanding of those words and expressions by those skilled in the relevant art. No special definition of a term or expression, that is, a definition that is different from the common and customary meaning as understood by those skilled in the art, is intended to be implied by the consistent use of the term or expression contained herein. Insofar as a term or expression is intended to have a special meaning, that is, a meaning different from that understood by those skilled in the art, such special definition will be specifically established in the specification in an explanatory manner that directly and unequivocally provides a special definition for the term or expression. 
     The present patent application reveals a new concept used for several illustrative embodiments of a pig routing insert or drain disclosed herein, which are adapted for use in block structures for subsea devices, such as, for example, a machined block manifold  8  comprising a machined block body  7 . Referring to  FIGS. 1 and 2 , in an illustrative embodiment, an illustrative embodiment of a pig routing insert or drain  1  disclosed herein comprises a generally cylindrical body  1 A composed of a plurality of illustrative pig blocking structures or bars  2  positioned in certain openings in the pig routing insert  1  that can be designed to be adapted to various types of designs, to become compatible with the shape of the fluid flow holes or passages defined in the block structure  7  of manifold  8  and its angles. The pig blocking structures or bars  2 , as included in the pig routing insert or drains disclosed herein, prevent the passage of the cleaning pigs to undesirable fluid flow holes machined in block  7  of manifold  8 , which would cause major inconveniences and perhaps the interruption of operations, while still allowing a substantially unrestricted working fluid flow through the openings that make up the pig blocking structures or bars  2 . As will be appreciated by those skilled in the art after a thorough reading of the present patent application, the pig routing insert or drains disclosed herein allow the substantially unrestricted working fluid flow from the fluid flow holes through the pig routing insert or drains, without significant adverse consequences for the system operation as a whole.  FIG. 2  shows the coordinate references x, y and z to embody the pig routing insert or drain  1  shown in  FIG. 1 . 
       FIG. 2  shows the illustrative pig routing insert or drain shown in  FIG. 1 , as well as an alternative pig routing insert or drain  5 . The pig routing insert or drain  1  comprises a plurality of partially restricted openings  3 A,  3 B and a substantially unrestricted flow opening  3 C. Each of the partially restricted openings  3 A,  3 B comprises a plurality of pig blocking structures or bars  2  that allow the working fluid to pass substantially unrestricted in the x, y and z directions, ensuring that the pig can only move in the x direction. The substantially unrestricted flow opening  3 C contains no pig blocking structures or bars  2 . The substantially unrestricted flow opening  3 C is adapted to allow the substantially unrestricted fluid flow through the substantially unrestricted flow opening  3 C whilst allowing a cleaning pig to pass through the substantially unrestricted flow opening  3 C. The partially restricted openings  3 A,  3 B are adapted to allow substantially unrestricted fluid flow through the partially restricted openings  3 A,  3 B whilst blocking the passage of a cleaning pig through the partially restricted openings  3 A,  3 B. The alternative pig routing insert or drain  5  shown in  FIG. 2  comprises a substantially unrestricted flow opening  5 A and a partially restricted opening  5 F. The partially restricted opening  5 F comprises a plurality of pig blocking structures or bars  2 . The pig routing insert  5  allows the fluid to pass in the x and z directions, while ensuring that the pig can only move in the x direction. The substantially unrestricted flow opening  5 A is adapted to allow the substantially unrestricted fluid flow through the substantially unrestricted flow opening  5 A whilst allowing a cleaning pig to pass through the substantially unrestricted flow opening  5 A. The partially restricted opening  5 F is adapted to allow the substantially unrestricted fluid flow through the partially restricted opening  5 F whilst blocking the passage of a cleaning pig through the partially restricted opening  5 F. 
     As shown in  FIG. 3 , the illustrative embodiments of the pig routing insert or drains disclosed herein, such as illustrative inserts  1  and  5 , can be inserted and installed in a subsea system block  7  of a structure, such as example, a subsea manifold  8 . Several methods for inserting the pig routing insert or drains disclosed herein in block  7  of manifold  8  are described in more detail below. 
     Several methods are disclosed herein for installing the pig routing inserts disclosed herein in a body of a structure. For example, the illustrative embodiments of the pig routing insert or drains disclosed herein (such as the illustrative pig routing insert or drain  1 ) can be fully machined and fully prefabricated in their final geometry before being installed in the block or the body  7  of manifold  8 . On the other hand, some of the illustrative embodiments of the pig routing insert or drains disclosed herein (such as the illustrative embodiment of the pig routing insert or drain  5 ) can be partially machined to its final configuration before being inserted in the body  7 . Subsequently, the partially machined insert was initially inserted and installed in the body of the manifold  8 , for example, by welding. More specifically, in one embodiment, the basic structure of the pig routing insert  5  can be machined initially into a structure, for example, a forge which is inserted through a side hole or opening in the manifold  8  and fixed to the block  7  by welding. Subsequently, with the partially machined pig routing insert or drain already fixed to the manifold  8 , one or more final machining processes can be performed in the partially perforated pig routing insert or drain  5  to define a final pig routing insert or drain  5  comprising a fluid flow passage of the desired configuration. In one example, the completed or final pig routing insert or drain  5  can be machined so that it has a smoothly curved fluid flow passage in order to avoid abrupt discontinuities that could jeopardize the ready pig passage. An embodiment of a pig routing insert or drain  5  with such a curved flow passage is illustrated in  FIG. 3 . 
       FIG. 4  illustrates yet another illustrative embodiment of a pig routing insert or drain  21  disclosed herein. The pig routing insert or drain  21  is adapted to be positioned and installed where multiple holes or flow lines defined in the manifold body intersect. 
       FIG. 5  generally describes an illustrative method disclosed herein for manufacturing and installing another alternative embodiment of a pig routing insert or drain  20  in the machined block manifold  8 . As will be appreciated by those skilled in the art, after a thorough reading of the present patent application, the method disclosed herein may be used to install any of the various embodiments of the pig routing insert or drains disclosed herein, regardless of the shape or configuration of the pig routing insert or drain as used in the project. In a particularly illustrative example, the method can be carried out in eight basic steps and will be revealed as an illustration. Obviously, this illustrative method does not intend to be limitative to the scope of the inventions disclosed herein. 
     An illustrative example of a method disclosed herein for manufacturing and installing the illustrative pig routing insert or drain  20  comprises the following basic steps: 
     a) pre-machining the longitudinal  9  and cross-sectional  10  fluid flow passages or holes in the body or block  7  of the manifold  8 ; 
     b) installing a corrosion-resistant material structure  11  (in the form, for example, of a cylindrical block) in the cross-sectional passage  10 , in which the corrosion-resistant material structure  11  can be composed of a material that is different from the material of the body  7  of manifold  8 , for example, the corrosion-resistant material structure  11  can be composed of a corrosion-resistant material such as, for example, an Inconel-type material; 
     c) machining a first opening through the corrosion-resistant material structure  11  which is aligned with the initial passage  9  in order to define a partially machined corrosion-resistant material structure  14 ; 
     d) making, for example, by welding, a corrosion-resistant material or lining  36  which can be, for example, an Inconel-type material, in the longitudinal passage  9 , in order to produce a new lined longitudinal passage  12  covered with the corrosion-resistant material or lining  36  extending through the first opening in the partially machined corrosion-resistant material structure  14 ; 
     e) forming, for example, by welding, a corrosion-resistant material or lining  36 A in the cross-sectional passage  10  on opposite sides of the partially machined corrosion-resistant material structure  14 , so as to produce a new lined passage  13  covered with a corrosion-resistant material lining  36 A which is positioned on opposite sides of the reaches of the partially machined corrosion-resistant material structure  14 ; 
     f) thermally treating the structure to relieve the stresses or pressures induced by welding; 
     g) machining a second opening through the partially machined corrosion-resistant material structure  14  that is aligned with the new initial lined passage  13 ; 
     h) positioning a prefabricated pig routing insert or drain  20  in the manifold  8  through the passage  13  until the moment the prefabricated insert or drain  20  is positioned at the intersection of the passages  12  and  13 ; and 
     i) blocking the prefabricated pig routing insert or drain  20  in position within the intersection, preferably by welding Inconel with Inconel, without the need to relieve stresses. 
     The fluids carried by the fluid flow hole or passage system of the manifold have corrosive characteristics, thus suggesting the use of corrosion-resistant materials to protect the equipment. In an illustrative embodiment, the corrosion-resistant material is, preferably, but without limitations, Inconel. The deposition of the corrosion-resistant material can be carried out by means of welding processes widely known to those skilled in the art, such as coating, and are shown by processes III, IV and V of  FIG. 5 . 
     The pig routing insert or drain  20 , as well as other embodiments of the pig routing insert or drains disclosed herein, can also be manufactured from fluid compatible, corrosion-resistant material, which is different from the material of the body  7  of the manifold  8 , such as Inconel 18, but other corrosion-resistant materials can also be used. 
       FIGS. 6A-6C, 7A-7C, 8A-8C, 9A-9C, 10A-10C, 11A-11C, 12A-12C, 13A-13C, 14A-14C and 15A-15C  are several views that show, further in more detail, an illustrative embodiment of a method disclosed herein (see  FIG. 5 ) that can be used to install an illustrative example of a prefabricated pig routing insert  20  in a machined block manifold  8  at an intersection  30  of two illustrative initial flow passages (or holes)  9 ,  10  defined in the body of the manifold  8 . Passage  9  has a center line  9 A, and the passage  10  has a center line  10 A. In these drawings, drawings “A” are expanded views of portions of the perspective and sectional views shown in  FIG. 5 ; drawings “B” are plan views of passages  9 ,  10 , and the intersection  30 ; and drawings “C” are sectional views taken through the center line  10 A of passage  10  in a plane that is normal to the center line  9 A of passage  9 . 
     Referring to  FIG. 6C , in the illustrative example showed here, the center lines  9 A,  10 A, of the initial passages  9 ,  10 , are respectively vertically offset from one another by a distance  33 . The sectional views in  FIG. 5  and drawings “A” are taken on a plane indicated by reference number  34  in  FIG. 6C , which includes the center line  9 A of the initial passage  9 , where the plane  34  is parallel to the center line  10 A of the initial passage  10 . As shown in  FIG. 6C , the initial passages  9  and  10  only partially intersects. That is, the initial passage  10  only intersects or crosses a lower portion of the initial passage  9 , that is, a partial or segmented circular configuration when looking at the view shown in drawings “C”. On the other hand, the initial passage  9  intersects or crosses an upper portion of the initial passage  10 . Obviously, as will be appreciated by those skilled in the art, after a thorough reading of the present patent application, in some embodiments, the center lines  9 A,  10 A can be positioned on a shared plane. In addition, the size, for example, the diameter, of the passages can be approximately the same (as in the illustrated example, wherein the diameter of the initial passage  9  is approximately the same as the initial diameter of the passage  10 ), or the diameters of the passages  9 ,  10  can be different. In addition, in some embodiments, the size of the initial passages  9 ,  10  and their relative positioning may be such that the passages intersect completely with each other, for example, both initial passages can have the same size, with the center lines of both initial passages located on the same plane. Another example of where the initial passages can completely intersect each other would be the case wherein one of the initial passages can be smaller than the other, so that the longer passage intersects or crosses the entire lesser pass. In a plan view as shown in  FIG. 6B  and/or in the side view as shown in  FIG. 6C , the angle between the center lines of the passages  9 ,  10  can be substantially normal, so as to result in a substantially normal intersection  30 . Alternatively, the center lines of passages  9 ,  10  may be oriented at non-normal angles to each other, thus resulting in a non-normal intersection  30 . Thus, the size, relative positioning and nature and degree of intersection of the flow passages should not be considered as a limitation to the inventions disclosed and claimed herein. 
       FIGS. 6A-6C  illustrate the manifold  8  after the initial passages  9 ,  10  have been machined in the block manifold  8 , thus defining the intersection  30  between the initial passages  9 ,  10 . 
       FIGS. 7A-7C  illustrate the manifold  8  after a corrosion-resistant material structure  11  has been inserted into the manifold  8  through the initial passage  10  and positioned at the intersection  30 . In an illustrative embodiment, the corrosion-resistant material structure  11  may be in the form of a solid circular cylindrical block of corrosion-resistant material. Note that the axial length of the corrosion-resistant material structure  11  is greater than an axial length  30 A of the intersection  30  in a direction parallel to the center line  10 A of the initial passage  10 . As indicated above, in an illustrative embodiment, the corrosion-resistant material structure  11  is a solid material, but this may not occur in all applications. For example, if desired, the corrosion-resistant material structure  11  could have an initial opening or pilot hole (not shown) machined in the body of the corrosion-resistant material structure  11  prior to installation of the corrosion-resistant material structure  11  (the opening of the initial pilot hole being therein) in the body  7 . In one embodiment, the pilot hole or opening would be coaxial with the long axis of the corrosion-resistant material  11 , and this initial opening would have a diameter smaller than the diameter of the final opening that will be formed in the corrosion-resistant material  11  which is aligned with the passage  10 . 
       FIGS. 8A-8C  illustrate the manifold  8  after the corrosion-resistant material structure  11  had been welded in position within the initial passage  10  at intersection  30 , as indicated by the simplistic illustrated weld metal  35  at both ends of the solid block of corrosion-resistant material  11 . 
       FIGS. 9A-9C  represent the manifold  8  after a first perforating process had been carried out through the initial passage  9  in the corrosion-resistant material structure  11  in order to define a first hole  11 A extending through the corrosion-resistant material structure  11 . As mentioned above, this process defines a partially machined corrosion-resistant material structure  14 . In the example shown, and as noted above, the first hole  11 A has a partial or segmented circular configuration when viewed in section (see  FIG. 9C ). The sectional configuration of hole  11 A corresponds to the intersection projected from the sectional area of the initial passage  9  with the initial corrosion-resistant material structure  11 . Note that the hole  11 A has a partial or segmented circular shape due to the vertical shift  33  (see  FIG. 6C ) between the center lines  9 A,  10 A of the initial passages  9 ,  10 , respectively. If the center lines  9 A,  10 A are positioned in the same plane, the hole  11 B through the corrosion-resistant material  11  would have a circular configuration with approximately the same inner diameter as that of the initial passage  9 . 
       FIGS. 10A-10C  illustrate the manifold  8  after a corrosion-resistant coating or lining material  36  had been formed on the inner surface of the initial passage  9  and in hole  11 A within the partially machined corrosion-resistant material structure  14 . As mentioned above, the process operation defines a new coated or lined longitudinal passage  12  extending through the manifold  8 . The corrosion-resistant lining material  36  can be formed by performing a welding process, can be formed to any desired thickness and can include any desired material, for example, an Inconel material, a stainless steel material or any other type of corrosion-resistant material, etc. Note that, in reference to  FIGS. 9B-C  and  FIGS. 10B-C , the corrosion-resistant lining material  36  is formed within the partial circular opening  11 A and in the portion of the passage  12  extending above the opening  11 A. 
       FIGS. 11A-11C  illustrate the manifold  8  after the corrosion-resistant coating or lining material  36 A had been formed on the inner surface of one side of the initial passage  10  to the point where the corrosion-resistant lining material  36 A has reached the partially machined corrosion-resistant material structure  14 . The corrosion-resistant coating or lining material  36 A may be of the same material as the corrosion-resistant coating or lining material  36 . Different reference numbers are used for convenience only. 
       FIGS. 12A-12C  illustrate the manifold  8  after the corrosion-resistant coating or lining material  36 A had been formed on the inner surface across the initial passage  10  to the point where the corrosion-resistant lining material  36 A has reached the partially machined corrosion-resistant material structure  14 . As mentioned above, the process operation defines a new coated or lined longitudinal passage  13  in the manifold  8  to the partially machined corrosion-resistant material structure  14 . 
       FIGS. 13A-13C  represent the manifold  8  after another perforating process had been carried out through the lined passage  13  (and passage  10 ) in the partially machined corrosion-resistant material structure  14  in order to define a second hole  11 B extending through the fully machined corrosion-resistant material structure  14 A. In effect, the fully machined corrosion-resistant material structure  14 A now constitutes a corrosion-resistant material sleeve that is positioned within the passage  13  and covers the entire intersection  30 . At this point, the corrosion-resistant material or sleeve  14 A has a machined inner surface. The final thickness of the fully machined corrosion-resistant material structure or sleeve  14 A may vary according to the specific application, for example, 3 to 6 mm. In the illustrated example, the second hole  11 B has a circular configuration when viewed in section. The sectional configuration of the second hole  11 B corresponds to the intersection projected from the sectional area of the coated or lined passage  13  with the partially machined corrosion-resistant material structure  14 . As illustrated, the second hole  11 B intersects with the first hole  11 A. 
       FIGS. 14A-14C  illustrate the manifold  8  after the prefabricated pig routing insert or drain described above with pig blocking structures or bars  20 X had been inserted into the manifold  8  through the lined passage  13  and positioned through the intersection  30  between the lined passages  12 ,  13 . More specifically, in an illustrative embodiment, the prefabricated pig routing insert or drain was positioned entirely within the second unlined hole  11 B (see  FIG. 13C ) defined in the fully machined corrosion-resistant material structure or sleeve  14 A. It is clear that, if desired, in some applications, the prefabricated pig routing insert or drain  20  may extend beyond the unlined hole  11 B in the sleeve  14 A, i.e. parts of the prefabricated pig routing insert or drain  20  can be positioned in the passage  13  on opposite sides of the sleeve  14 A. However, in both situations, for at least a portion of an axial length of the prefabricated pig routing insert or drain  20  (and, in some cases, the entire axial length of the prefabricated pig routing insert or drain  20 ), an outer surface of the pig routing insert or drain  20  is positioned on and in contact with the inner machined surface of the corrosion-resistant material or sleeve  14 A. Referring to  FIG. 5  and  FIGS. 14A-14C , note that the opening  20 A in the prefabricated pig routing insert or drain  20  is sized and positioned to align or combine with the segmented or partial circular opening corresponding to the first hole  11 A defined in the corrosion-resistant material or sleeve  14 A. Also note that opening  20 A in the prefabricated pig routing insert or drain  20  constitutes a substantially unrestricted flow opening defined in the prefabricated pig routing insert or drain  20  which is adapted to allow substantially unrestricted fluid flow, for example, from passage  12 . The substantially unrestricted flow opening  20 A is also adapted to allow a cleaning pig (not shown) to pass through opening  20 A. Also note that the prefabricated pig routing insert or drain  20  comprises two partially restricted illustrative openings  20 B, each having at least one pig blocking structure  20 X positioned within the partially restricted opening, wherein each of the partially restricted openings  20 B is adapted to allow substantially unrestricted fluid flow whilst blocking the passage of a cleaning pig through the partially restricted openings  20 B. 
       FIGS. 15A-15C  illustrate the manifold  8  after the prefabricated pig routing insert or drain described above  20  had been welded in its final installed position within the corrosion-resistant material or sleeve  14 A at intersection  30 , as indicated by the weld metal  37  simplistically illustrated at both ends of the prefabricated routing insert or drain  20 . Obviously, as noted above, in some embodiments, the axial length of the prefabricated pig routing insert or drain  20  may be greater than the axial length of the sleeve  14 A, such that at least a portion of the prefabricated pig routing insert or drain  20  extends beyond the ends of the sleeve  14 A. 
       FIGS. 16A-16E  are several views of an illustrative embodiment of a pig routing insert  5  disclosed herein which comprises a curved inner flow path  5 A that extends at least partially through the pig routing insert  5 . A  FIG. 16A  is a perspective view of an illustrative embodiment of a machined block manifold  8  comprising a plurality of perforated fluid flow openings or passages formed in the manifold  8 .  FIG. 16B  is the same view as  FIG. 16A , wherein the body of the manifold  8  is faded to show some of the perforated fluid flow openings or fluid flow passages formed within the manifold  8 .  FIG. 16C  is a perspective view in horizontal section of an illustrative embodiment of a manifold  8  disclosed herein with a plurality of pig routing inserts  5  installed therein.  FIG. 16D  is a plan view in horizontal section of an illustrative embodiment of a manifold  8  disclosed herein, in which the section/cut is taken through the fluid flow headers  9 L and  9 R formed within the manifold  8 .  FIG. 16E  is a vertical cut taken through manifold  8  and center line  9 A of fluid flow header  9 L. 
     As shown in  FIGS. 16A-16E , an illustrative embodiment of a machined manifold  8  disclosed herein generally comprises a main body  8 A and two illustrative end portions  8 B,  8 C which are threaded to main body  8 A. As illustrated in these drawings, several perforated or drilled fluid flow passages have been formed in the manifold  8 . More specifically, the manifold  8  comprises a plurality of fluid flow headers  9 L,  9 R referenced in general by using the number  9 , which are positioned substantially parallel to each other. As illustrated, a pig routing insert  5  is positioned adjacent to each of the opposite ends of the headers  9 . As best seen in  FIG. 16D , the manifold comprises a plurality of primary flow inlets/outlets  40 A- 40 D, referenced in general by using the number  40 . More specifically, primary flow inlets/outlets  40 A and  40 D are in uninterrupted communication with header  9 L, while primary flow inlets/outlets  40 B and  40 C are in uninterrupted communication with header  9 R. Depending on the specific application, and the desired fluid path flowing through the manifold, the primary flow inlets/outlets  40  can function as either a fluid inlet or a fluid outlet. A threaded flange  41  and seal  42  are provided at each of the primary flow inlets/outlets  40  to facilitate coupling of the flow lines (not shown) to the manifold  8 . 
     Referring to  FIG. 16D , in an illustrative embodiment, the center lines  40 X of the primary flow inlets/outlets  40  can be oriented at an angle in relation to the center line of its associated header  9 , for example, the center lines  40 X of primary flow inlets/outlets  40 A,  40 D are positioned at an angle to the center line  9 A of header  9 L. In reference to the  FIGS. 16B and 16E , an illustrative fluid flow passage  43  is in uninterrupted communication with the header  9 L through a first downwardly directed fluid flow passage  45  which is poured into the pig routing insert  5  associated with the primary flow inlet/outlet  40 A and a second downwardly directed fluid flow passage  49  which is poured into the pig routing insert  5  associated with the primary flow inlet/outlet  40 D. Several valves positioned within the flow passage  43  can be activated to direct the fluid flow to the header  9 L, as desired. An insert  50  composed of a corrosion-resistant material, such as Inconel, is also shown in  FIG. 16D . Insert  50  can be provided to ensure that there is no space in the corrosion-resistant materials and in the base materials, for example, carbon steel, of the manifold body  8 . 
     As best seen in  FIGS. 16C and 16D , the illustrative pig routing insert  1  (see  FIG. 2 ) is installed at an intersection between the header  9 R, a downward slopped fluid flow passage  47  and a downwardly directed fluid flow passage (not shown) which is located vertically above opening  3 A in the pig routing insert  1 . The fluid flow from the angular fluid flow passage  47  enters the header  9 R passing through the partially restricted opening  3 B with pig blocking structures  2  positioned therein, while the fluid flow from the downwardly directed fluid flow passage (not shown) enters header  9 R passing through the partially restricted opening  3 A. The fluid flowing inside the header  9 R flows through the substantially unrestricted flow opening  3 C formed in the pig routing insert  1 . 
     As best seen in  FIGS. 16C-16E , the pig routing insert  5  comprises a substantially unrestricted inner curved flow opening  5 A with curved surfaces  5 B. The curved opening  5 A provides a smooth transition without any significant gaps, so that a cleaning pig (not shown) flows, for example, from inside the header  9 L and passes out through the primary flow inlet/outlet  40 A. The amount of curvature of the curved opening  5 A may vary depending on the specific application, but the intention is to provide a smooth transition in the overall flow path due to the fact that the primary flow inlets/outlets  40  are positioned at an angle  40 X relative to their associated header  9 . As illustrated in the drawings, as well as in  FIG. 2 , the pig routing insert  5  comprises a partially restricted flow opening  5 F which has a plurality of pig blocking structures  2  positioned therein. The flow opening  5 F in the pig routing insert  5  associated with the primary flow inlet/outlet  40 A is adapted to receive fluid flow from the downwardly directed flow passage  45  which is in uninterrupted communication with the flow passage  43 . The flow opening  5 F in the pig routing insert  5  associated with the primary flow inlet/outlet  40 D is adapted to receive fluid flow from the downwardly directed flow passage  49  which is in uninterrupted communication with the flow passage  43 . Note that the pig routing inserts  5  in header  9 R have only the curved opening  5 A defined therein. Note also that each of the pig routing inserts  5  is positioned within a recess  8 X formed within the body of the manifold  8 . 
     As will be appreciated by those skilled in the art after a thorough reading of the present patent application, the various embodiments of the pig routing insert or drains disclosed herein may have a variety of different configurations depending on the specific application. For example, pig blocking structures or bars positioned within a partially restricted opening of the pig routing insert or drain can be of any desired size, shape, configuration or number, as long as they allow substantially unrestricted fluid flow through the partially restricted opening whilst blocking the passage of a cleaning pig through the partially restricted opening. For example, the pig blocking structures can take the form of the illustrative pig blocking structures  20 X, or they can be structures similar to a cylindrical rod. 
     In an illustrative embodiment, the pig routing structures disclosed herein may comprise at least one substantially unrestricted flow opening and at least one partially restricted flow opening having at least one pig blocking structure positioned within the partially restricted opening. The substantially unrestricted flow opening is adapted to allow the substantially unrestricted fluid flow through the opening and to allow a cleaning pig (not shown) to pass through the substantially unrestricted flow opening. The partially restrict opening is adapted to allow substantially unrestricted fluid flow whilst also blocking the passage of a cleaning pig through the partially restricted opening. In some applications, the pig routing structure may not comprise any partially restricted flow openings. In addition, in some applications, the pig routing structures disclosed herein can be positioned at an intersection between multiple flow lines. For example, referring to  FIG. 4 , the illustrated portion of the manifold  8  comprises five illustrative flow lines  60 - 64  that intersect at a common intersection  70  within the manifold  8 . In this embodiment, the illustrative pig routing structure  21  comprises two substantially unrestricted flow openings  21 A,  21 C which are aligned with flow lines  60  and  62 , respectively. The pig routing structure  21  also comprises partially restricted flow openings  21 B,  21 D and  21 E which are aligned with flow lines  61 ,  63  and  64 , respectively. Note that each of the partially restricted openings  61 ,  63  and  64  comprises a plurality of pig blocking structures  21 X. In this example, the pig routing structure  21  allows a cleaning pig to pass through flow lines  60  and  62  whilst blocking the entrance of the cleaning pig into the flow lines  61 ,  63  and  64 . 
     The specific embodiments described above are illustrative only, since the object described can be modified and practiced in different but equivalent ways, which are evident to those skilled in the art having the benefit of the teachings presented herein. For example, the process steps set out above can be performed in a different order. In addition, no limitation applies to the details of construction or design shown herein, except as described in the claims below. It is, therefore, evident that the specific embodiments revealed above can be altered or modified, and all such variations are considered to be within the spirit and scope of the claimed object. Note that the use of terms such as “first”, “second”, “third” or “fourth” to describe various processes or structures in this specification and in the attached claims is used only as an abbreviated reference for such steps/structures, and does not necessarily imply that these steps/structures are carried out/formed in that ordered sequence. Obviously, depending on the exact claim language, an ordered sequence of such processes may be necessary or not. Therefore, the protection sought herein is as set out in the claims below.