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Of necessity, BOPs require highly efficient hydraulic control systems ca-
pable of operating any of the functions on the stack with precision and dispatch.
For instance, high flow rates are required for the large volumes needed to operate
the ram and annular preventers. These volumes may range from 5 gal for small
rams to 50 gal for a large annular preventer.
The NL (Koomey) system best illustrates redundant hydraulic operation (fig.
6.19). The basis of this hydraulic control system is a male control pod connected to
the control receptacle mounted on the upper frame of the BOP stack. This control
pod houses the SPM valves that direct the hydraulic fluid to operate the various
functions on the stack. The mating surface of the control pod has outlets with
individual seals that match inlets on the conical sealing face of the female control
receptacle. The female receptacle has outlets that usually are connected by flexible
high-pressure hose to the various functions of the BOP stack.
Figure 6.17 – BOP stack with lower marine riser package. (Courtesy Vetco)
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