Choke Kill Valves

Hydril Company

All underwater BOP stacks are equipped with valve manifolds to control access to the choke and kill lines attached to the marine riser. All BOP stacks, with the exception of some low pressure 20 inch single annular BOP stacks, are equipped for both choke and kill line operation.

A basic bore size and pressure ratings of 31/» inch, 5,000 psi working pressure and 3-1/16 inch, 10,000 psi working pressure have been standardized by the various manufacturers. There has been discussion, however, of going to 4-1/16 inch, 10,000 psi working pressure components for use with the larger BOP stacks, i.e., 183A inch and 2\% inch, 10,000 psi working pressure sizes.

Valves used are hydraulically operated, fail-safe closed.Hydraulic pressure is required to open the valve only. Closing the valve is accomplished by spring force within the valve operator and by some means of assist from line pressure. An inherent problem of all hydraulic operated fail-safe valves is the reaction force caused by hydrostatic head always present on the opening pressure side of the hydraulic piston in the valve operator.

This pressure would tend to hold the valve open by balancing the spring force on the underside of the piston which is the closing force for the valve. It is necessary then to allow the hydrostatic head to also react on the pressure close side of the hydraulic operator piston. This is accomplished for the various makes of valves by either oil filled seal pots or oil filled bellows chambers. This allows the valves to operate at various depths under water without adverse effects from the hydrostatic head. Figure 3-6 shows a cutaway of a typical hydraulic fail-safe close gate valve.

The major manufacturers of choke/kill valves are: Cameron Iron Works, Hydril Company, Oil Center Tools Division of FMC Corporation, Rockwell-McEvoy, Rucker-Shaffer, and the W-K-M Division of ACF Industries. With the exception of Hydril Company, who uses a ball valve design, the otheT manufacturers all furnish various gate valve designs. All manufacturers now offer an angle or cross type valve body to minimize the number of connections required to install the choke/kill line manifolds on the BOP stacks.

Much discussion centers around the pTopeT placement of the choke/kill line outlets on the BOP stack. Figure 3-7 shows a typical setup for a three ram BOP stack. Two valves are used for each choke/kill line for redundant control. The choke line is located below the bottom rams. This will allow circulation beneath both sets of pipe rams above. The kill line is located between the two lower sets of rams. This allows the fill line to be used for circulation as a choke line if the upper pipe rams are closed. Should it be necessary to cut the drill string with the shear rams, the drill pipe can be hung off and sealed on the bottom rams. Circulation is possible fay pumping down the kWl line and flowing out the choke line.

Figure 3-8 shows the typical setup for a four ram BOP stack. The choke line is located between the two lower sets of rams. The kill line is located between the two top sets of rams. This allows circulation in the same manner as a three ram BOP stack. No circulation is possible beneath the bottom rams. This may seem to be a waste of the bottom rams. However, this is instead a very good safety feature. Should the choke line become washed out or otherwise damaged, the bottom rams may be closed, thereby shutting off pressure to all components above the bottom rams.

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IPfiESSURE SEALING! , CLAMP RING

SEAL RING Ibody

SEAL RING Ibody

Wkm Gate Valve

SEAT SKIRTS

Fig. 3-6 Cutaway of typical hydraulic gate valve.

UPSTREAM AND OÛWNSTOtM SEATS ARE BOTII IN FULL CONTACT WITH GATE IN EITHER OPEN OR CLOSED POSITION

SEAT SKIRTS

Fig. 3-6 Cutaway of typical hydraulic gate valve.

13-5/8"- 5000 and 10000

Chock Line Valves Bop

NOTE- ANNULAR PREVENTERS ARE 5000 PS1 WORKING PRESSURE RATING FOR 18-3/4" 21- 1/4" SIZES

Fig, 3-7 Subsea blowout preventer stack.

13-5/8"- 5000 and 10000 16 - 3/4"- 5000 18-3/4" a 21 1/4" 10000

Bop Valve Drilling
Fig. 3-8 Subsea blowout preventer stack,

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Responses

  • regina
    What are Off Shore Drilling Choke valves?
    7 years ago
  • RITA
    How a Drilling Choke works?
    7 years ago
  • Milena Tesfalem
    Is cameron fc hydraulic valve fail closed?
    7 years ago
  • frank
    Is the check valve on the choke or the kill line?
    5 years ago
  • roy
    What is the failsafe in a bop in subsea?
    3 years ago
  • miranda
    How to make kill line and choke line for bop?
    2 years ago
  • fiyori
    What will enable affect the close of the choke and kill line valves on subsea stack?
    2 years ago
  • Steffen
    How do subsea failsafe valves work?
    11 months ago
  • delores
    Are the choke and kill lines below the annular?
    4 months ago
  • Maddison
    What is the main use for a failsafe valve on a bop?
    3 months ago

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