Patent Publication Number: US-9404323-B2

Title: Emergency cylinder lowering circuit with regenerative hydraulics and burst protection

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application No. 61/780,610, filed Mar. 13, 2013, the contents of which are herein incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the invention generally relate to catwalks for conveying pipe to a drill floor from a lower section of a drilling rig or drill site. Specifically, embodiments of the invention relate to an emergency cylinder lowering circuit which allows the catwalk trough to be lowered remotely to its home position in a safe manner in the event of a hydraulic failure. 
     2. Description of the Related Art 
     In a drilling operation or rig work-over operation, whether on a water-based or land-based drilling rig, pipe for the drilling operation, casing, or other tubulars are often stored at or supplied from a level that is lower than the drill floor. Operators typically use a “catwalk” to convey the pipe from the lower level to the drill floor. The pipe is typically mechanically transported (e.g. pushed by a skate and/or pulled in catwalk in a v-shaped trough) from a level below the rig floor to the rig floor. 
     In prior art catwalks, the trough is raised using hydraulic cylinders which raise a leg of the catwalk. Prior art hydraulic cylinders used with catwalks have counter balance valves, one on each end of the cylinder, that maintain pressure within the cylinder in the event that a hose breaks or the hydraulic power unit (HPU) fails. As a result, the counter balance valves prevent the cylinders, and the catwalk, from moving up or down. In order to lower the catwalk, current systems require the counter balance valves to be manually opened so that the hydraulic fluid can flow to the rod end and the tank and the hydraulic cylinders can retract to their home position. 
     Accordingly, it would be useful to have a system that allows catwalk users to control the routing of hydraulic fluid from a remote location so that the catwalk can be slowly and safely returned to its home position. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention provide a safety system for bypassing counter balance valves for a catwalk hydraulic cylinder from a remote location in a safe and controlled manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited aspects of the invention can be understood in detail, a more particular description of embodiments of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1A  shows a catwalk in the position in which pipe is loaded onto the catwalk or unloaded from the catwalk. 
         FIG. 1B  shows the catwalk in an elevated position in which the hydraulic cylinders that raise and lower the catwalk are extended and pipe is being conveyed to or from the drill floor. 
         FIG. 1C  shows the hydraulic cylinders fully extended so that pipe or other tubulars can be conveyed to a drill floor. 
         FIG. 2  shows a detailed view of  FIG. 1C  in which the hydraulic cylinders are fully extended so that a leg of the catwalk has raised one end of the trough adjacent to the drill floor. 
         FIGS. 3A and 3B  show the cylinders with the connections to counter balance valves and velocity fuses that control the flow of hydraulic fluid in and out of the cylinder. 
         FIG. 4  shows an embodiment of the actuated pump and valve package. 
         FIGS. 5A and 5B  are external views of the safety valve package. 
         FIG. 6  is a cut-away of the safety valve package, showing the needle valve, the relief valve, the check valve, and the pump connection. 
         FIG. 7  is a schematic of the valve system of the hydraulic system for the hydraulic cylinders that raise and lower the trough. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  shows a catwalk  1  in the position in which tubulars are loaded onto a trough  2  of the catwalk  1 . The tubulars are moved along the trough  2  by a skate  3 .  FIG. 1B  shows the trough  2  in the process of being raised to the drill floor. The trough  2  is raised from the position shown in  FIG. 1A  to the positions shown in  FIGS. 1B and 1C  using hydraulic cylinders  4 A,  4 B, which raise leg  5  of the catwalk  1 . 
       FIG. 2  is an enlarged, detailed view of  FIG. 1C .  FIG. 2  illustrates the hydraulic cylinders  4 A,  4 B raising the leg  5  to a substantially vertical position. Embodiments of the invention are used when, for example, there is a hydraulic failure and the hydraulic cylinders  4 A,  4 B have locked the trough  2  in the positions shown in  FIGS. 1B or 1C . 
     The embodiments of the invention described herein are configured to route oil from the base end of hydraulic cylinders  4 A,  4 B around one or more counter balance valves and through one or more velocity fuses. The oil flows from the velocity fuse through a needle valve (e.g. needle valve  16  as shown in  FIG. 6 ) and then flows through a check valve (e.g. check valve  17  as shown in  FIG. 6 ) to a tee connected to the rod end of the cylinder  4 A,  4 B (e.g. via rod end connection  15  as shown in  FIG. 6 ) and a pump outlet port (e.g. pump connection  11  as shown in  FIG. 6 ). The check valve prevents pressure from the pump from causing the cylinder  4 A,  4 B to extend (e.g. via cap end connection  14  as shown in  FIG. 6 ). In the event that the cylinder  4 A,  4 B is over center so that gravity cannot be used to lower the catwalk  1 , a manual or air actuated pump can be used to pump fluid into the rod end of the cylinder  4 A,  4 B (e.g. via pump connection  11  and rod end connection  15  as shown in  FIG. 6 ). Once the weight on the cylinder  4 A,  4 B becomes positive on the base end of the cylinder, the oil is allowed to pass from the base end of the cylinder  4 A,  4 B to the rod end and the hydraulic cylinders  4 A,  4 B safely lower the catwalk  1  to its home position. Excess oil that comes from the base end of the cylinder  4 A,  4 B that is not used to fill the rod end of the cylinder  4 A,  4 B is routed through a relief valve (e.g. relieve valve  12  as shown in  FIG. 6 ) back to a hydraulic fluid tank (e.g. via connection  13  as shown in  FIG. 6 ). In the event that a hose ruptures or one of the fittings in the fluid circuit is damaged in such a manner as to cause the cylinder  4 A,  4 B to fall rapidly, the velocity fuse will close, thereby arresting the descent of the main arm and thus the catwalk  1 . 
     One embodiment of the hydraulic cylinders  4 A,  4 B used with the embodiments of the invention is shown in  FIGS. 3A and 3B . The two hydraulic cylinders  4  each have counterbalance valves  6 A and  6 B connected to the rod end and base end respectively that ensure that in the case of a broken hydraulic fluid hose or a failure of the hydraulic power unit (HPU), pressure will be maintained in the hydraulic cylinders  4 A,  4 B and the raised catwalk  1  will not fall suddenly to the ground. The hydraulic cylinders  4 A,  4 B each also include velocity fuses  7 A and  7 B connected to the rod end and base end respectively. In the event that a hydraulic hose breaks while the safety valve package embodiment of the invention is being used, the velocity fuses  7 A,  7 B stop the flow of hydraulic fluid in the event that the flow of fluid exceeds about 4 gallons per minute so that the hydraulic cylinders  4 A,  4 B will lock in place rather than allowing the trough  2  to fall uncontrolled to the base of the catwalk  1 . 
       FIG. 4  shows an embodiment of the actuated pump  8  and the safety valve package  9 . Safety valve package  9  is shown in greater details in  FIGS. 5A and 5B , discussed below. 
       FIG. 5A  shows an embodiment of the safety valve package  9 . The safety valve package  9  allows the counterbalance valves  6 A,  6 B of the hydraulic cylinders  4 A,  4 B to be bypassed so that the raised catwalk  1  may be safely lowered to its home position as illustrated in  FIG. 1A .  FIG. 5A  further shows a needle valve adjustment knob  10 , a pump connection  11 , and a portion of relief valve  12 .  FIG. 5B  shows another angle of the safety valve package  9 . The safety valve package  9  includes a connection  13  for the hydraulic fluid tank, a connection  14  for the base cap end of the hydraulic cylinders  4 A,  4 B, and a connection  15  for the rod end of the hydraulic cylinders  4 A,  4 B. 
       FIG. 6  shows the internal components of a housing of the safety valve package  9 . Relief valve  12  maintains pressure within the circuit and allows for excess oil to be routed back to hydraulic fluid tank via connection  13 . Needle valve  16  allows the user to slowly provide fluid via connection  14  from the base cap end of the hydraulic cylinders  4 A,  4 B to the rod end of the hydraulic cylinders  4 A,  4 B via connection  15  so that the rods may be retracted and the catwalk  1  may be lowered to its home position as illustrated in  FIG. 1 . Check valve  17  prevents back pressure from the pump via pump connection  11  from going to the base cap end of the hydraulic cylinders  4 A,  4 B via connection  14  and routes the pressure to the rod end via connection  15 . The check valve  17  allows a manual or actuated pump attached to pump connection  11  to pump hydraulic fluid to the rod end of the hydraulic cylinders  4 A,  4 B via connection  15  in the event that the catwalk  1  is over center of the catwalk legs  5  and must be lowered to a point where gravity allows the catwalk  1  to be lowered to its home position in a controlled manner using the safety valve package  9 . Once the weight of the hydraulic cylinders  4 A,  4 B becomes positive on the base end of the cylinders, oil is allowed by the relief valve  12  to pass from the base end of the cylinders to the rod end, with the excess oil going to the hydraulic fluid tank. 
       FIG. 7  is a schematic showing the safety valve system and the safety valve package  9 . Pump  8  connects to safety valve package  9  at pump connection  11 . The base cap end of hydraulic cylinders  4 A and  4 B connect to safety valve package  9  at connection  14 . The rod end of hydraulic cylinders  4 A and  4 B connect to safety valve package  9  at connection  15 . Connection  13  is connected to hydraulic fluid tank  20 , which supplies hydraulic fluid to the system through pump  21  and control valve  22 . Relief valve  12 , needle valve  16 , and check valve  17  are used to operate safety valve package  9  as described above with reference to  FIG. 6 . 
     While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.