Patent Publication Number: US-4220177-A

Title: Offshore loading system with articulated manifolds

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to fluid loading systems and more particularly, to loading systems with articulated tanker manifolds for transferring fluid between an offshore terminal and a marine tanker. 
     2. Description of the Prior Art 
     The production of oil and gas from offshore wells has developed into a major endeavor of the petroleum industry, and this growth has lead to the development of means for transporting petroleum products from offshore wells to shore-based refineries or storage facilities. Many of the wells are being drilled and completed in deepwater locations where the use of marine tankers of very large capacity constitutes the most practical and efficient method of transporting the petroleum products. 
     Some of the prior art loading facilities include a fluid handling means such as a fixed mooring buoy or a floating platform to which a tanker may be moored while loading. The tanker and the floating platform move relative to each other during the loading operation due to winds, tides and the amount of fluid which is loaded into the tanker. The height of the tanker above the waterline changes as the tanker is loaded or unloaded, thus requiring that a flexible or articulated hose be connected between the tanker and the floating platform. When flexible hoses are used a tender is normally required to assist the tanker in picking up the flexible hoses for connection to the tanker&#39;s manifold. Such an arrangement not only requires the use of a tender, but movement of the tanker may cause the flexible hoses to be broken. Also the hoses are bulky, heavy, hard to handle and require a relatively large crew of workers to connect the hose to the tanker. 
     Some of the other prior art loading facilities include a marine loading arm having relatively complex articulated arms that are heavy, bulky, relatively expensive and require complex balancing systems, as the balance of these arms changes as the fluid content of the arm changes. The prior art systems must also provide special restraints to prevent the fluid conduits from swinging rapidly into a vertical position when the system is disconnected from the tanker manifold. 
     SUMMARY OF THE INVENTION 
     The present invention comprises an offshore loading system for transferring fluid from a first fluid handling means to a second handling means, and to provide for relative movement between the two handling means. This invention overcomes some of the disadvantages of the prior art by employing a tower or other suitable vertical support structure that is mounted on a platform or other first fluid handling means, and a generally horizontally-disposed support boom having one end thereof connected to the tower or support structure. A generally horizontal conduit member having an articulated portion at the outboard end is mounted on the support boom. The outboard end of the horizontal conduit member is pivotally connected to the upper end of a vertical conduit member which is slidably connected to the outboard end of the support boom. A support cable means for supporting the weight of the vertical conduit member and the fluid therein is connected so that the vertical conduit member can be raised and lowered in accordance with the relative movement between the support beam and the second fluid handling means. The lower end of the vertical conduit member is pivotally connected to the outboard end of an articulated manifold assembly which is, in turn, connected to the second fluid handling means. The use of the combination of articulated conduits mounted on the floating platform and articulated manifolds on the tanker compensates for both vertical and horizontal movement between the tanker and the floating platform. The articulated manifolds compensate for horizontal movement between the tanker and the platform so that the vertical conduit member can be maintained in a true vertical position. This means that special restraints are not required to prevent the conduit from swinging as the conduit is disconnected from the tanker manifolds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation of an offshore loading system with articulated manifolds according to the present invention, with the vertical conduit member shown connected in operating position to a marine tanker. 
     FIG. 2 is an enlarged side elevation of a portion of the offshore loading system shown in FIG. 1. 
     FIG. 3 is a plan view of the offshore loading system shown in FIG. 2. 
     FIG. 4 is a front elevation of the offshore loading system shown in FIG. 2. 
     FIG. 5 is an isometric drawing of the mechanism used to lock the vertical conduit in working position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An offshore loading system with articulated manifolds according to the present invention comprises a tower or other suitable vertical support structure 10 (FIG. 1) mounted on the top of a platform 11 and having a generally horizontally-disposed support boom 12 pivotally connected at the inboard end thereof to the platform 11. The support boom 12 is retained in a nearly horizontal position by a mast 15, a pair of boom support cables 16a, 16b and a sheave 17. The inboard end of the mast 15 is pivotally connected to the tower 10 at a point slightly above the inboard end of the support boom. The vertical support cable 16a is connected between the outboard end of the support boom 12 and the outboard end of the mast so that the height of the outboard end of the boom is determined by the height of the outboard end of the mast 15. The cable 16b is connected to the outboard end of the mast 15, is threaded over a sheave 17 and connected to the usual counterbalance and winch arrangement (not shown), which is commonly used in the fluid loading art. The details of these commonly used devices are not considered to be a part of this invention. 
     A pipe assembly 20 (FIGS. 2 and 3) includes a pair of sets of pipes with each set comprising a generally horizontal rigid boom conduit member 20b, having the inboard end thereof connected to a U-connector 19 which is connected atop a single vertical conduit member 20a that extends downward through the tower 10 and the platform 11 to a fluid source (not shown). The boom conduit member includes an articulated left end portion (FIG. 2) comprising a jumper assembly 21 having a pair of conduit members 21a, 21b connected by a swivel joint 22. The jumper assembly is connected to the boom conduit member 20b by a swivel joint 26 and is connected to a vertical conduit member 27 by a swivel joint 28. The vertical conduit member includes a pair of conduit pipes 27a, 27b connected by a swivel joint 29 to facilitate movement of the conduit member 27 into the stowed position shown by the phantom lines of FIG. 2. The vertical conduit member carries at its lower end a triple pipe swivel joint assembly 32 (FIGS. 1, 2, 4) comprising first, second and third swivel joints 33, 34 and 35 respectively, a plurality of 90° pipe elbows 39a-39e and a short piece of pipe 40. The joint assembly 32 is connected to the outboard end of an articulated manifold 43 mounted on a tanker T. 
     The tanker T is secured to the platform 11 by one or more mooring lines which allow the tanker to swing freely according to the dictates of wind and current and to retain the tanker a proper distance from the platform while the tanker is loaded through the pipe assembly. Mounted on the deck D of the tanker is a platform P which supports a pair of articulated manifolds 43 and 43&#39;. 
     Each of the articulated manifolds 43, 43&#39; include a pair of swivel joints 44, 45, and a pair of lengths of pipe 49,50 interconnected by a plurality of pipe elbows 52-55. The swivel joint 44 is connected between the elbow 52 and a length of pipe 58 extending upward from below the deck D of the tanker T. The articulated manifold is supported near its midpoint for movement over the platform P by a pair of support wheels 63 which are rotatably connected to the underside of the elbow 54. Since the wheels move directly over the surface of the platform, a safe envelope E (FIG. 3) over which the manifold can be moved without damage to either the manifold or the loading arm, can be painted on the platform. The tanker operator can check to see that the outboard end of the manifold does not extend outside this safe envelope. Also a pressure-sensitive tape (not shown) may be placed around the edges of a zone in which the support wheels may safely move and the tape coupled to an electric alarm system (not shown) to provide an audible alarm signal when the support wheels 63 reach the tape. 
     The upper portion of the vertical conduit pipe 27a is slidably mounted inside a collar 67 which is welded or otherwise connected to the outboard end of the support boom 12. The vertical conduit member 27 is supported, raised and lowered by a cable 68 (FIGS. 2, 4) which is connected to an ear 69 that is welded or otherwise fixed to the lower end of the vertical conduit pipe 27a. The cable is threaded over a pair of sheaves 71, 72 (FIG. 2) and connected to a counterweight 75 and a winch 76. The sheave 71 is rotatably mounted on a pin 73 (FIGS. 2, 4) which is connected to a pair of bearings 66a, 66b which are welded to the outboard end of the boom 12. The sheave 72 is rotatably mounted on the upper portion of the platform 11 by a pin 74. The counterweight 75 supports a major portion of the weight of the vertical conduit member 27 so that a relatively small winch 76 can be used to raise the vertical conduit member and move the jumper pipe assembly 21 into the stowed position shown in the phantom lines of FIG. 2. A tag line 79 is connected between the lower end of the vertical conduit member 27 and a winch 80, with the winch 80 being mounted on the left portion of the boom 12. The winch and tag line are used to pull the lower portion 27b of the conduit member and the triple pipe joint assembly 32 into the stowed position, shown in FIG. 2, where the conduit member 27b rests in the groove 81a (FIG. 4) of a bracket 81. The bracket 81 is mounted on the lower side of the boom 12. 
     When the apparatus is in the working position, as shown by the solid lines of FIGS. 2 and 4, the lower portion 27b of the conduit member is secured in a vertical position by a locking device 84 (FIGS. 4, 5). The locking device 84 includes a bracket 85 having an end plate 86 mounted at one end thereof with a bore 87 extending through the plate 86, and having the other end of the bracket 85 welded or otherwise connected to the lower portion 27b of the conduit member 27. An angle bracket 90 is welded or otherwise connected to the lower end of the upper portion 27a of the conduit member. The free end of the bracket 90 is enclosed by an end plate 91 having a bore 92 therein. A hydraulic cylinder 95 is mounted in the angle bracket 90 with a rod 96 aligned with the bore 92 in the end plate 91. When the upper portion 27a and the lower portion 27b of the conduit member are in the working portion (FIG. 2) the bores 87 and 92 are aligned so that the rod 96 can be extended through both of the bores to lock the upper and lower portions 27a, 27b in a vertical working position. 
     When the apparatus is not in use the rod 96 is retracted and the lower portion 27b is moved into the stowed position (FIG. 2) by the winch 80 and the tag line 79. The rod 96 is extended and retracted by applying hydraulic fluid to the cylinder 95 through a pair of hydraulic lines (not shown), as is well known in the art. 
     Thus, the present invention provides an all-metal offshore loading system having a vertical conduit member which remains in a substantially fixed horizontal position during the fluid transfer operation and having an articulated tanker manifold which follows the relative horizontal movements between the tanker and a platform. The vertical conduit member can be moved up and down to compensate for changes in vertical positions of the tanker and the platform. 
     Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.