Abstract:
The method of improving the brake closing response time on an offshore reel, comprising providing a brake disk, providing a control valve with a pilot on each end, providing a reference signal on one end, providing a control signal on the other end, shifting to a position to supply operating pressure to release brakes from a brake disk when said control signal exceeds said reference signal and venting said operating signal when said control signal is less than said reference signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    N/A 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    N/A 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK 
       [0003]    N/A 
       BACKGROUND OF THE INVENTION 
       [0004]    The field of this invention is that of umbilical reels which store and handle hose and/or electric and/or fiber optic control lines for deepwater offshore service. These reels typically pay out these lines, called umbilicals, and mechanics clamp the umbilical to a drilling riser or other pipe string being run to the seafloor. The actual weight of the umbilical is typically supported once it leaves the reel and in the water by the riser or pipe to which it is clamped. Typically these reel units have to be closely monitored to insure that excessive tension, which can destroy the umbilical, is not encountered as it is being deployed or in the event of unexpected movement of the riser or pipe to which it is clamped . 
         [0005]    When the drilling riser or other pipe string is lowered, an operator will rotate the spool to allow umbilical to be paid off in accordance with the downward movement of the riser or pipe. In some cases, the motor can be left in the take up mode, and the umbilical simply be pulled off the spool against a relatively constant torque provided by the motor power. 
         [0006]    When appropriate the brakes are set to stop the motion of the reel. The brakes are typically of a spring closed or “failsafe” design. Air pressure is used to provide a force against the springs to open or release the brakes. The air pressure is supplied from a control panel mounted locally on the reel or from a remote station. 
         [0007]    When it is desired to set the brakes, the valve at the local or remote station is opened to vent the air pressure from the brakes, allowing them to close. In the case of remote panels, sometimes as much as 200′ from the reel, the length of the lines can cause a delay in the closing of the brakes of up to 12 seconds. 
         [0008]    Quick dump valves have been added to the piping near the brakes, but have been of little benefit as the volume of air in the signal lines is of the same general volume as the volume of air in the brakes. 
         [0009]    Hundreds of reels have been installed on offshore floating drilling system since approximately 1960. In this time numerous reels have been installed at long distances such as 200′ from the control panel. Response times for setting the brakes are frequently as long as 12 seconds, which is an extremely long time in emergency situations. Industry experts have simply accepted this delay as normal as they had no alternatives to improve the response time. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    The object of this invention is to provide a method for reducing the response time for closing brakes on offshore reels. 
         [0011]    A second object of the present invention is to provide a method of providing predictable control of the response time for closing brakes in spite of temporary reductions in the supply pressure. 
     
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    FIG. no.  1  is a view of a reel of this invention on the deck of a deepwater floating vessel, showing the umbilical clamped to a drilling riser. 
           [0013]    FIG. no.  2  is an end view of a reel without this invention. 
           [0014]    FIG. no.  3  is an end view of a reel of this invention. 
           [0015]    FIG. no.  4  is a schematic of the control circuit of this invention when the brakes are activated or opened using a regulated supply to provide the operating pressure. 
           [0016]    FIG. no.  5  is a schematic of the control circuit as in  FIG. 4  when the brakes are deactivated or closed. 
           [0017]    FIG. no.  6  is a schematic of the control circuit of this invention when the brakes are activated or opened using an unregulated supply to provide the operating pressure. 
           [0018]    FIG. no.  7  is a schematic of the control circuit as in  FIG. 6  when the brakes are deactivated or closed. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIG. 1  shows a vessel  1  floating on the ocean  3  and having a drilling riser  5  extending down toward a blowout preventer stack  7 . The blowout preventer stack  7  is landed on a subsea wellhead  9  which is in turn landed on the seafloor  10 . Casing  12  extends into the seafloor below the subsea wellhead  9  for the purpose of drilling an oil or gas well. 
         [0020]    Reel  14  is positioned on the deck  16  of vessel  1  with umbilical  18  extending over pulley or sheave  20  and going down the side of the riser  5 . Riser  5  is a series of jointed pipes and as they are sequentially connected and lowered into the ocean to lower the blowout preventer stack  7 , clamps  22  secure the umbilical  18  to the drilling riser  5 . The riser  5  and blowout preventer stack  7  may weigh as much as 650,000 lbs. When lowered with the umbilical  18  attached, if the rotation of the reel  14  is stopped, the full 650,000 lb. load can be put on the umbilical  18 , destroying it. An even worse consequence is that the pulley or sheave  20  can be pulled down from its mounting and injure personnel on the deck  16 . 
         [0021]    Referring now to  FIG. 2 , reel  14  is shown with a frame  30  and a spool  32 . Main disk  34  is shown mounted to the spool  32  by four slip clutch assemblies  36 . As will be seen later, the slip clutch assemblies  36  provide a preset friction grip on the brake disk  34  to withstand torque as the spool  32  rotates, but will be allowed to slip if the preset friction grip is exceeded when a large tension on the umbilical  18  is encountered. A slip torque controller  37  is located on the side of the spool  32  which automatically adjusts the control pressure to the slip clutch assemblies  36  as the spool  32  rotates allowing the friction grip on the brake disk  34  to vary to maintain a relatively constant slip tension on the umbilical  18  as successive layers of umbilical  18  leave the reel  14  at different distances from the spool  32  centerline. 
         [0022]    Motor  38  is shown with gear  40  (shown through the motor for clarity) engaging the outer gear profile  42  on the perimeter of brake disk  34 . Gear  40  and the outer gear profile  42  are positively engaged such that if the motor  38  does not turn, the brake disk  34  cannot rotate. Alternately, the connection between the motor  38  and the brake disk  34  can be by roller chain and sprocket profiles, as is well understood in the industry. A motor torque controller  43  is located next to the motor  38  which adjusts the air pressure to the motor  38  as the spool  32  rotates to maintain a relatively constant tension on the umbilical  18  as the umbilical  18  leaves the reel  14 . 
         [0023]    Brake assemblies  44  and  46  are caliper or disk brake assemblies which are spring loaded to engage when air pressure is released. If the air pressure is released from these brakes, the brakes will close and the brake disk  34  will not rotate about the centerline of spool  32 . 
         [0024]    Spool  32  rotates on main bearings  48 . Panels  50 ,  52 , and  54  provide valves for remote control functions at the end of the umbilical. Levelwind  56 , as will be seen in  FIG. 3 , has gear  58  to receive motive power from the brake disk  34  and a manual clutch and handle  59  which allows for adjustment of the wrapping position of the umbilical  18 . 
         [0025]    Locking pin  60  is engaged in locking pin socket  61  which is fixed to leg  62  of the reel frame  30 . Locking pockets  63  are provided on the side of spool  32  for engaging locking pin  60  to positively stop the rotation of the spool  32 . When locking pin  60  is an instrumented load pin, it can be engaged and give a positive reading of the torque output of the motor  38 . 
         [0026]    The air actuators  70  and  72  of brake assemblies  44  and  46  are connected by hose sections  74  and  76  respectively, which are in turn connected by hose  78  to control panel  80 . Brake valve  82  on control panel  80  send an air pressure signal to push against a spring to release the brakes  44  and  46  from the brake disk  34 . When the air is vented by brake valve  82 , springs within the brake  44  and  46  cause the brakes to lock onto the brake disk  34  as air pressure is lost. 
         [0027]    In control lines such as 78 of approximately 200′, the time it requires to vent this pressure and allow the brake assemblies to lock onto the brake disk is as much as 12 seconds. This is a long time for setting the brakes, especially on emergency situations. 
         [0028]    Referring now to  FIG. 3 , a pressure brake assist (PBA) valve package  100  is shown installed in the line between the brakes  44  and  46  and the remote control panel  80 . Line  102  is an air supply line which is used to power the control valve within valve package  100 . Line section  104  is the new link between the valve package  100  and lines  74  and  76 . 
         [0029]    Referring now to  FIG. 4 , a pneumatic schematic of valve package  100  is shown with attaching lines as indicated in  FIG. 3 . Control valve  110  receives the control pressure signal from line  78  onto and air pilot  112  and at the valve inlet at  114 . The pressure in signal line  78  will vary from zero to full rig air pressure at about 120 p.s.i. Full rig air pressure comes in line  102 , goes through check valve  116 , through regulator  118 , and to air pilot  122  as a reference pressure. Pressure gauges are shown at  124  and  126 . 
         [0030]    The reference pressure going to air pilot  122  can be set to various pressures, however, testing has indicated about 80 p.s.i. is an optimum pressure. As is shown in  FIG. 4 , the control pressure in line  78  is increased to full rig air pressure of about 120 p.s.i. and the valve is shifted to the position as shown delivering the 120 p.s.i. to the brake actuators at  70  and  72 . When regulator  128  is installed the control pressure in line  78  can be regulated to give an operating pressure to lines  114 ,  104 ,  74 , and  76  and to the brake actuators if desired. 
         [0031]    Referring now to  FIG. 5 , if the control pressure in line  78  is reduced to any pressure below 80 p.s.i. (the reference pressure) the valve shifts to connect line  104  to the vent port  112 . This immediately dumps the pressure in line  78  to the atmosphere. When line  78  is approximately 200′ long as discussed in  FIG. 2 , the closing time for the brakes is reduced to approximately 3 seconds, or four times faster than the lines without the valve package  100 . 
         [0032]    Although the pressure from the brakes goes to zero quickly thru the valve package  100 , the air pressure in the line  78  still declines over a  12  second period as before. Fully shifting valve  110  when the pressure in pilot  122  exceeds the pressure in pilot  112  substantially increases the safety of the unit by reducing the brake response time. 
         [0033]    Referring now to  FIG. 6 , the connection on control valve  110  is moved to the unregulated supply upstream of regulator  118 . In this position, the control pressure on pilot  112  can be regulated and the actuating pressure to operate the brakes will be either 0 p.s.i. or full supply air pressure. 
         [0034]    The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.