You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 U.S.C. §371 national stage application of PCT/US2009/041706 filed Apr. 24, 2009, which claims the benefit of U.S. Provisional Patent Application No. 61/047,624 filed Apr. 24, 2008, both of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     BACKGROUND 
     Deepwater accumulators provide a supply of pressurized working fluid for the control and operation of subsea equipment, such as through hydraulic actuators and motors. Typical subsea equipment may include, but is not limited to, blowout preventers (BOPs) that shut off the well bore to secure an oil or gas well from accidental discharges to the environment, gate valves for the control of flow of oil or gas to the surface or to other subsea locations, or hydraulically actuated connectors and similar devices. Accumulator fluid power may be used to operate underwater process valves and connectors, as well as supply of non-continuous process chemicals into a process stream at the seafloor. Applications may also include management of fluid power and electrical power on subsea drilling BOP stacks, subsea production Christmas trees, workover and control systems (WOCS), and subsea chemical injection systems. 
     Accumulators are typically divided vessels with a gas section and a hydraulic fluid section that operate on a common principle. The principle is to precharge the gas section with pressurized gas to a pressure at or slightly below the anticipated minimum pressure required to operate the subsea equipment. Fluid can be added to the accumulator in the separate hydraulic fluid section, increasing the pressure of the pressurized gas and the hydraulic fluid. The hydraulic fluid introduced into the accumulator is therefore stored at a pressure at least as high as the precharge pressure and is available for doing hydraulic work. 
     Accumulators generally come in three styles—the bladder type having a balloon type bladder to separate the gas from the fluid, the piston type having a piston sliding up and down a seal bore to separate the fluid from the gas, and the float type with a float providing a partial separation of the fluid from the gas and for closing a valve when the float approaches the bottom to prevent the escape of the charging gas. A fourth type of accumulator is pressure compensated for depth and adds the nitrogen precharge pressure plus the ambient seawater pressure to the working fluid. 
     The precharge gas can be said to act as a spring that is compressed when the gas section is at its lowest volume/greatest pressure and released when the gas section is at its greatest volume/lowest pressure. Accumulators are typically precharged in the absence of hydrostatic pressure and the precharge pressure is limited by the pressure containment and structural design limits of the accumulator vessel under surface ambient conditions. Yet, as accumulators are used in deeper water, the efficiency of conventional accumulators decreases as application of hydrostatic pressure causes the gas to compress, leaving a progressively smaller volume of gas to charge the hydraulic fluid. The gas section must consequently be designed such that the gas still provides enough power to operate the subsea equipment under hydrostatic pressure even as the hydraulic fluid approaches discharge and the gas section is at its greatest volume/lowest pressure. 
     For example, accumulators at the surface typically provide 3000 psi working fluid maximum pressure. In 1000 feet of seawater the ambient pressure is approximately 465 psi. For an accumulator to provide a 3000 psi differential at 1000 ft. depth, it must actually be precharged to 3000 psi plus 465 psi, or 3465 psi. 
     At slightly over 4000 ft. water depth, the ambient pressure is almost 2000 psi, so the precharge would be required to be 3000 psi plus 2000 psi, or 5000 psi. This would mean that the precharge would equal the working pressure of the accumulator and any fluid introduced for storage may cause the pressure to exceed the working pressure and accumulator failure. 
     At progressively greater hydrostatic operating pressures, the accumulator thus has greater pressure containment requirements at non-operational (no ambient hydrostatic pressure) conditions. 
     The accumulator design must also take into account human error contingencies. For example, removal of the external ambient hydrostatic pressure without evacuating the fluid section of the accumulator to reestablish the original gas section precharge pressure may result in failure due to gas section pressures exceeding the original precharge pressures. 
     Accumulators may be included, for example, as part of a subsea BOP stack assembly assembled onto a subsea wellhead. The BOP assembly may include a frame, BOPs, and accumulators to provide back up hydraulic fluid pressure for actuating the BOPs. The space available for other BOP package components such as remote operated vehicle (ROV) panels and mounted controls equipment becomes harder to establish due to an increasing number and size of the accumulators required to be considered for operation in deeper water depths. The accumulators are also typically installed in series where the failure of any one accumulator prevents the additional accumulators from functioning. 
     The inefficiency of precharging accumulators under non-operational conditions thus requires large aggregate accumulator volumes that increase the size and weight of the subsea equipment. Yet, offshore rigs are moving further and further offshore to drill in deeper and deeper water. Because of the ever increasing envelope of operation, traditional accumulators have become unmanageable with regards to quantity and location. In some instances, it has even been suggested that in order to accommodate the increasing demands of the conventional accumulator system, a separate subsea skid may have to be run in conjunction with the subsea equipment in order to provide the required volume necessary at the limits of the water depth capability of the equipment. With rigs operators increasingly putting a premium on minimizing size and weight of the drilling equipment to reduce drilling costs, the size and weight of all drilling equipment must be optimized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed description of the embodiments, reference will now be made to the following accompanying drawings: 
         FIG. 1  is a system arrangement layout; 
         FIG. 2  is a table listing examples of typical system operating depths; 
         FIG. 3  is a diagram of a system architecture; 
         FIG. 4  is an intensifier based system state transition diagram; 
         FIG. 5  is a system architecture with fluid recovery; 
         FIG. 6  is an accumulator system configuration; 
         FIG. 7  is a hybrid system configuration; 
         FIG. 8  is an intensifier configuration; 
         FIG. 9  is an intensifier with a recharge pump configuration; 
         FIG. 10  is an intensifier with regenerative electrical power; 
         FIG. 11  is an intensifier with regenerative electrical power and fluid recovery; 
         FIG. 12  is a screen assembly; 
         FIG. 13  is a regulator assembly; 
         FIG. 14  is an exploded view of a regulator; 
         FIG. 15  is a cutaway view of a regulator; 
         FIG. 16  is a reference assembly; 
         FIG. 17  is a schematic of a reference pump; 
         FIG. 18  is a schematic of a reference pump module; 
         FIG. 19  is a schematic of a reference pilot accumulator and reservoir; 
         FIG. 20  is an exploded view of an intensifier; 
         FIG. 21  is a cross section view of an intensifier; 
         FIG. 22  is a comparison of intensifying cylinders; 
         FIG. 23  is a cross section view of an inner barrel instrument package; 
         FIG. 24  is a schematic of an intensifier without fluid recovery; 
         FIG. 25  is a schematic of an intensifier with fluid recovery; 
         FIG. 26  is an exploded view of an accumulator; 
         FIG. 27  is a caged float valve arrangement; 
         FIG. 28  is a schematic of an accumulator; 
         FIG. 29  is a recharge pump assembly; 
         FIG. 30  is an exploded view of a recharge pump; 
         FIG. 31  is a schematic of a recharge pump; 
         FIG. 32  is a power pack assembly; 
         FIG. 33  is a cutaway view of a power pack assembly; 
         FIG. 34  is a schematic of a power pack; 
         FIG. 35  is a regenerator assembly; 
         FIG. 36  is an exploded view of a regenerator assembly; 
         FIG. 37  is an embodiment of an accumulator in a subsea blowout preventer stack; 
         FIG. 38  is a hybrid embodiment in a subsea blowout preventer stack; 
         FIG. 39  is an embodiment of intensifier with no recharge pump in a subsea blowout preventer stack; 
         FIG. 40  is an embodiment of an intensifier with a recharge pump in a subsea blowout preventer stack; 
         FIG. 41  is an embodiment of an intensifier with regeneration in a subsea blowout preventer stack; and 
         FIG. 42  is an embodiment of an intensifier with regeneration on a subsea mudmat. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the drawings and description that follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawing figures are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in the interest of clarity and conciseness. The present invention is susceptible to embodiments of different forms. Specific embodiments are described in detail and are shown in the drawings, with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. Any use of any form of the terms “connect”, “engage,” “couple,” “attach,” or any other term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. The various characteristics mentioned above, as well as other features and characteristics described in more detail below, will be readily apparent to those skilled in the art upon reading the following detailed description of the embodiments, and by referring to the accompanying drawings. 
       FIG. 1  illustrates an embodiment of an apparatus to manage underwater hydraulic and electrical power from fluid source  1900  and electrical source  0015 ; to fluid load  1900  and electrical load  6000 ; under remote hydraulic pilot control and remote electronic control. As shown in  FIGS. 1 and 2 , the accumulator  2000  is used to store fluid energy in water depths above the minimum hydrostatic operating depth. In water depths below the minimum hydrostatic operating depth, the intensifier  1000  is used to generate fluid energy. In water depths above the minimum hydrostatic operating depth, the fluid source  1900  is used to recharge the accumulator  2000 . In water depths below the minimum hydrostatic operating depths and above the hydrostatic recharge depth, fluid source  1900  is used to recharge the intensifier  1000 . In water depths below the hydrostatic recharge depth; fluid source  1900 , the recharge pump  6000 , and power pack  7000  are used to recharge the intensifier. During intensifier  1000  operation (generating fluid power), the regenerator  8000  is used to cogenerate electrical energy that is stored in the power pack  7000  for subsequent use. The power pack  7000  is otherwise charged from electrical source  0015  from a surface supply. The reference pilot accumulator  3200  is used to control the regulator  5000  to achieve desired fluid pressure from the intensifier  1000  when operated below the minimum hydrostatic operating depth. The screen  4000  is used to filter seawater that is used by the regulator  5000 , intensifier  1000 , and recharge pump  6000 . 
       FIGS. 3 and 5  illustrate the system schematic without and with the use of an external delivery fluid recovery system. 
       FIG. 3  shows the arrangement of intensifier  1000 , accumulator  2000 , screen  4000 , regulator  5000 , regenerator  8000 , reference reservoir  3100 , reference pilot accumulator  3200 , reference pump  3300 , recharge pump  6000 , seawater at ambient pressure, and subsea fluid header  1900 . The subsea fluid header  1900  operates at the maximum delivery fluid pressure of the accumulator  2000 . As pressure in the subsea fluid header  1900  drops to below the intensifier  1000  delivery pressure, the regulator  5000  allows seawater to enter the intensifier  1000 , sufficient to generate and maintain the intensifier  1000  delivery pressure as delivery fluid is consumed from the intensifier  1000  by operation of the underwater equipment. 
       FIG. 3  also illustrates interconnections between the equipment. The reservoir  3100  is connected to the reference pump  3300  via instrument tubing run  3133 . The pilot accumulator  3200  is connected to the reference pump  3300  via instrument tubing run  3233 . The reservoir  3100  is connected to the regulator  5000  via instrument tubing run  3320 . The pilot accumulator  3200  is connected to the regulator  5000  via instrument tubing run  3220 . The regulator  5000  is connected to the intensifier  1000  by instrument tubing run  1905  and large diameter tubing run  5010 . The power pack  7000  is connected to the recharge pump  6000  via pressure balanced multiconductor electrical cable  6970 . The recharge pump  6000  is connected to the intensifier  1000  via medium diameter tubing run  1960 . The regenerator  8000  is connected to the power pack  7000  via high current medium voltage pressure balanced electrical power cable  7940 . 
     The regenerator  8000  utilizes the seawater consumed by the intensifier  1000  when developing delivery fluid power, to cogenerate electrical power which is stored by the power pack  7000 . The seawater exhaust of the regenerator  8000  is connected to the screen  4000  input bell flange. 
     The screen  4000  filters seawater that flows from the surrounding ambient environment to flow through the regenerator  8000  and subsequently to the regulator  5000 . 
     The regulator  5000  regulates the flow of seawater  0001  to the intensifier  1000  to maintain intensifier  1000  delivery pressure; utilizing a pilot pressure reference  3220  from the reference pilot accumulator  3200 , feedback  1905  from the intensifier  1000  delivery fluid pressure, and hydrostatic ambient pressure. The regulator  5000  uses, for example, a one-atmosphere reference reservoir  3100  to allow the regulator  5000  to respond to changes in intensifier delivery fluid pressure  1905 . The output pressure from the regulator  5000  is at or below ambient hydrostatic pressure. 
     The reference pilot accumulator  3200  pressure is adjustable through the use of the reference pump  3300 , which allows hydraulic control fluid to be pumped from the reference reservoir  3100  to the reference pilot accumulator  3200  and vice versa via connections  3133  and  3233 ; in order to change the pressure within the gas charged reference pilot accumulator  3200 . The reference pump  3300  is operated by an external underwater control system through hydraulic valve pilot signals Ref Pump Stroke A  3310  and Ref Pump Stroke B  3311 , the direction of pressure increase through hydraulic valve pilot signals pilot accumulator pressure increase/decrease  3312 . 
     The reference pilot accumulator  3200  and reference reservoir  3100  incorporate pressure transducers to allow an external control system to monitor reference pressures via the pilot pressure transducer cable  3210  and the reservoir pressure transducer cable  3110 . 
     The intensifier  1000  is operated as a pressure intensifying pump, where regulated seawater pressure (below ambient hydrostatic pressure) is multiplied to a delivery fluid pressure exceeding ambient hydrostatic pressure. Based on installed geometry constraints, desired minimum hydrostatic operating depth, and volumetric delivery constraints, this embodiment uses an intensification factor of 2.2. However, other intensification factors may be appropriate depending on the operating parameters and environment. The intensifier  1000  may be isolated from the regulator  5000  utilizing the regulator isolation valve pilot line  1920  from an external control system. The intensifier  1000  may be isolated from the delivery fluid output and fill header  1900  utilizing the intensifier isolation valve pilot control from an external control system. The intensifier  1000  may be isolated from the recharge pump  6000  utilizing the recharge pump isolation valve pilot  1930  control from an external control system. The intensifier  1000  delivery pressure and volume measurement is available to an external control system via the intensifier instrument communications and power cable  1910 . 
     The recharge pump  6000  is used to evacuate seawater from the intensifier  1000 , in order to refill the intensifier  1000  from the subsea fluid header  1900 , when the intensifier  1000  is used below the minimum hydrostatic recharge water depth. The recharge pump  6000  utilizes electrical power stored in the power pack  7000 . The recharge pump  6000  operation is controlled via the recharge pump instrument power and communications cable  6910  to an external underwater control system. 
     The power pack  7000  is used to store electrical power from either or both surface electrical supply  0015  and from the regenerator  8000 . The power pack  7000  is controlled via the power pack instrument power and communications cable  7910  to an external underwater control system. 
     Once the intensifier  1000  is depleted of delivery fluid, the regulator  5000  is isolated from the intensifier  1000  via operation of the intensifier isolation pilot hydraulic signal  1950  from an external underwater control system. The recharge pump  6000  is operated via the recharge pump instrument communications and power control interface  6910 , to evacuate seawater from the intensifier  1000  and allowing the intensifier  1000  to withdraw delivery fluid from the subsea fluid header  1900  under pressure from the surface. In water depths below minimum hydrostatic delivery operation and above minimum hydrostatic recharge operation, the use of the recharge pump  6000  is not required, as a sufficient pressure differential exists between the surface supplied delivery fluid output and fill header  1900  and ambient hydrostatic pressure to allow the delivery fluid output and fill header  1900  to push the seawater out of the Intensifier. Below the minimum hydrostatic recharge depth, it is necessary to augment the delivery fluid output and fill header  1900  pressure, through evacuation of seawater from the intensifier  1000  by the recharge pump  6000 . 
       FIG. 4  describes the operation of the intensifier  1000  in the form of a state transition diagram, with the following states: idle full  9101 , idle empty  9102 , idle transit  9103 , hydro discharge  9100 , header overpressure recharge  9104 , and header underpressure recharge  9105 . Idle full  9101  indicates a state where the intensifier  1000  is full of delivery fluid and under pressure control of the regulator  5000  and capable of discharging delivery fluid, but under no delivery fluid demand from the underwater control system. Idle empty  9102  indicates a state where the intensifier  1000  is empty of fluid and under pressure control of the regulator  5000 , but no longer able to discharge delivery fluid to the underwater control system. Idle transit  9103  indicates a state where the intensifier  1000  is discharging delivery fluid under regulator  5000  control to the underwater control system. Overpressure recharge  9104  is a state where the intensifier  1000  is no longer under regulator  5000  control and withdrawing delivery fluid from delivery fluid output and fill header  1900 . Underpressure recharge  9105  is a state where the intensifier  1000  is no longer under regulator  5000  control, and withdrawing delivery fluid from the delivery fluid output and fill header  1900  with assistance from the recharge pump  6000  evacuating seawater from the intensifier  1000 . Transitions between states are described as causes for the transition. Transition  9115  occurs when the intensifier  1000  is not full and the regulator isolation valve pilot  1920  is not active or engaged. Transition  9114  occurs when the intensifier  1000  is full and the regulator isolation valve pilot  1920  is not active or engaged and the recharge pump  6000  is not running. Transition  9117  occurs when the regulator isolation valve pilot  1920  is not active or engaged and the recharge pump  6000  is not running. Transition  9118  occurs when the regulator isolation valve pilot  1920  is active or engaged and the pump isolation valve pilot  1930  is active or engaged and the recharge pump  6000  is not running. Transition  9119  occurs when the regulator isolation valve pilot  1920  is not active or engaged. Transition  9116  occurs when the regulator isolation valve pilot  1920  is active or engaged and the recharge pump  6000  is running. Transition  9120  occurs when no change in intensifier  1000  volume is detected. Transition  9121  occurs when a decrease in intensifier  1000  volume is detected. Transition  9123  occurs when the intensifier  1000  volume is empty. Transition  9124  occurs when the regulator isolation valve pilot  1920  is active or engaged. Transition  9122  occurs when the regulator isolation valve pilot  1920  is not active or engaged. Transition  9112  occurs when the regulator isolation valve pilot  1920  is active or engaged and the recharge pump  6000  is running. Transition  9111  occurs when the intensifier  1000  volume is full and the regulator isolation valve pilot  1920  is not active or engaged. Transition  9113  occurs when the recharge pump  6000  is running. 
       FIG. 5  shows a variation of the system that incorporates the capability of withdrawing delivery fluid from either the delivery fluid output and fill line  1900 , or from an external fluid recovery underwater storage tank line  0020  that feeds from an underwater storage tank (not shown). 
       FIG. 6  illustrates a system configuration to be used exclusively above the minimum hydrostatic operating depth of the system, where the accumulators  2000  are used to store delivery fluid at the operating pressure of the delivery fluid input and fill header  1900 . Hydraulic accumulator isolation valve pilots  1940  are provided from the external underwater control system to allow for individual isolation capabilities. The accumulator instrument communications and power cable  1910  to the external underwater control system allows for communication of individual pressure measurement and individual fluid level measurement within the accumulators  2000 . 
       FIG. 7  illustrates a system configuration to be may used above the minimum hydrostatic recharge depth of the system, where the accumulators  2000  are used to store delivery fluid at the operating pressure of the delivery fluid input and fill header  1900  and intensifiers  1000  are used to generate delivery fluid power below the minimum hydrostatic operating depth. Hydraulic accumulator isolation valve pilot signals  1940  are provided from the external underwater control system to allow for individual accumulator isolation capabilities. Hydraulic regulator isolation valve pilot  1920  signals are provided from the external underwater control system to allow for individual recharge capabilities of the intensifiers  1000 . Hydraulic recharge pump isolation valve pilot  1930  signals are provided from the external underwater control system to allow for individual recharge capabilities of the intensifiers  1000 . Hydraulic intensifier isolation valve pilot  1950  signals are provided from the external underwater control system to allow for individual intensifier isolation capabilities. The intensifier accumulator instrument communications and power cable  1910  to the external underwater control system allows for communication of individual pressure measurement and individual fluid level measurement within the accumulators  2000 , and individual pressure and volume measurement within the intensifiers  1000 . 
       FIG. 8  illustrates a system configuration to be may used exclusively below the minimum hydrostatic operating depth and above the minimum hydrostatic recharge depth of the system, where the intensifiers  1000  are used to generate delivery fluid power. Hydraulic regulator isolation valve pilot  1920  signals are provided from the external underwater control system to allow for individual recharge capabilities of the intensifiers  1000 . Hydraulic recharge pump isolation valve pilot  1930  signals are provided from the external underwater control system to allow for individual recharge capabilities of the intensifiers  1000 . Hydraulic intensifier isolation valve pilot  1950  signals are provided from the external underwater control system to allow for individual intensifier isolation capabilities. The intensifier instrument communications and power cable  1910  to the external underwater control system allows for communication of individual pressure measurement and individual fluid level measurement within the intensifiers  1000 . 
       FIG. 9  illustrates a system configuration to be used below the minimum hydrostatic operating depth, where the intensifiers  1000  are used to generate delivery fluid power and the recharge pump  6000  and power pack  7000  are used to individually recharge the intensifiers  1000 . Hydraulic regulator isolation valve pilot  1920  signals are provided from the external underwater control system to allow for individual recharge capabilities of the intensifiers  1000 . Hydraulic recharge pump isolation valve pilot  1930  signals are provided from the external underwater control system to allow for individual recharge capabilities of the intensifiers  1000 . The hydraulic intensifier isolation valve pilot  1950  signals are provided from the external underwater control system to allow for individual intensifier isolation capabilities. The intensifier instrument communications and power cable  1910  to the external underwater control system allows for communication of individual pressure measurement and volume measurement within the intensifiers  1000 . 
       FIG. 10  illustrates a system configuration to be used below the minimum hydrostatic operating depth, where the intensifiers  1000  are used to generate delivery fluid power and the recharge pump  6000  and power pack  7000  are used to individually recharge the intensifiers  1000 . The regenerator  8000  is used to augment power pack  7000  recharge time and surface electrical supply current demand  0015 . Hydraulic regulator isolation valve pilot  1920  signals are provided from the external underwater control system to allow for individual recharge capabilities of the intensifiers  1000 . Hydraulic recharge pump isolation valve pilot  1930  signals are provided from the external underwater control system to allow for individual recharge capabilities of the Intensifiers. The hydraulic intensifier isolation valve pilot  1950  signals are provided from the external underwater control system to allow for individual intensifier isolation capabilities. The intensifier instrument communications and power cable  1910  to the external underwater control system allows for communication of individual pressure measurement and volume measurement within the Intensifiers. The regenerator instrument communications and power cable  8910  is used to monitor and control the regenerator  8000 . The power pack instrument communications and power cable  7910  is used to monitor and control the power pack  7000 . The recharge pump instrument communications and power cable  6910  is used to monitor and control the recharge pump  6000 . 
       FIG. 11  illustrates a system configuration to be used below the minimum hydrostatic operating depth, where the intensifiers  1000  are used to generate delivery fluid power and the recharge pump  6000  and power pack  7000  are used to individually recharge the intensifiers  1000 . The intensifiers  1000  utilize a replacement subplate mounted valve, in lieu of the hydraulic isolation valve to allow selection of delivery fluid for recharge, from either the subsea fluid header  1900 , or from an external fluid recovery reservoir via the recovery fluid header  1901 . The regenerator  8000  is used to augment power pack  7000  recharge time and surface electrical supply current demand  0015 . Hydraulic regulator isolation valve pilot  1920  signals are provided from the external underwater control system to allow for individual recharge capabilities of the Intensifiers. Hydraulic recharge pump isolation valve pilot  1930  signals are provided from the external underwater control system to allow for individual recharge capabilities of the intensifiers  1000 . Hydraulic intensifier selection valve pilot  1950  signals are provided from the external underwater control system to allow for individual intensifier isolation and recharge capabilities. The intensifier instrument communications and power cable  1910  to the external underwater control system allows for communication of individual pressure measurement and volume measurement within the intensifiers  1000 . 
       FIG. 12  illustrates the arrangement of the screen  4000  comprised of as assembly of coarse housing  4100 , medium housing  4200 , and fine housing  4300 . The coarse housing  4100  and medium housing  4200  are joined by flange  4100 , and the medium housing  4200  and fine housing  4300  are joined by flange  4102 . The inlet to the screen  4000  is indicated by the inlet flange  4003 . The outlet from the screen  4000  is indicated by the outlet flange  4005 . The coarse housing  4100 , medium housing  4200 , and fine housing  4300  have mounting feet  4104  to allow the housings to be permanently mounted to a supporting structure. The housings have maintenance lids  4102 ,  4202 , and  4302  to allow access to replaceable filter media in the respective housings. The coarse housing  4100  contains a replaceable coarse filter  4110 , designed to accommodate a flow rate of 600 gallons per minute, with a volume of 60,000 gallons throughput, and hold 2 lbs of particulate matter, and a Taylor mesh size of 250. The medium housing  4200  contains a replaceable medium filter  4210 , designed to accommodate a flow rate of 600 gallons per minute, with a volume of 60,000 gallons throughput, and hold 3 lbs of particulate matter, and a Taylor mesh size of 28. The fine housing  4300  contains a replaceable fine filter  4310 , designed to accommodate a flow of 600 gallons per minute, with a volume of 60,000 gallons, hold 5 lbs of particulate matter, and a Taylor mesh size of 9. The screen  4000  is designed for a flow rate of 600 gallons per minute, a total volume of 60,000 gallons throughput; hold a total of 10 lbs of seawater particulate contaminants, with a total pressure drop of 100 psi. It should be appreciated that these filter configurations are examples and that other filter configurations may be used as well. 
     The regulator  5000  is a non-relieving, seawater service flow and negative pressure regulator. It is used in conjunction with the Intensifier to supply regulated seawater pressure at or below hydrostatic pressure to cause the Intensifier to deliver hydraulic control fluid at a specific pressure above hydrostatic pressure. The regulator  5000  utilizes hydrostatic pressure, feed forward differential pressure reference, and feed back intensifier  1000  fluid pressure to maintain downstream seawater pressure at or below hydrostatic pressure during low or high flow conditions during delivery fluid consumption by the subsea control system. The regulator  5000  is designed to relieve to ambient (hydrostatic pressure) when the downstream pressure exceeds hydrostatic pressure. The regulator  5000  utilizes the pilot accumulator  3220  pressure reference for its feed forward reference. The regulator  5000  utilizes the hydraulic pressure delivery  1950  of the intensifier  1000  to provide monotonical sum of error and gain associated with reductions of delivery fluid pressure  1900 . 
       FIG. 13  illustrates the field connections of the regulator  5000 . Unregulated ambient pressure seawater enters the regulator  5000  from the screen  4000  at the inlet split flange  5020  and inlet seal sub  5016 . Seawater at regulated pressure at or below ambient pressure conditions exits the regulator  5000  at the outlet split flange  5025  and outlet seal sub  5016 . Gage reference pressure is applied from the pilot accumulator  3200  at tubing port  5220 . Feedback pressure from the intensifier  1000  delivery fluid port is applied at tubing port  5905 . Reservoir  3300  circulation at one atmosphere pressure is applied at tubing port  5320 . 
       FIG. 14  illustrates an exploded view of the regulator  5000 , comprised of an end cylinder cap  5113  with seawater inlet port  5001 ; a cylinder body  5109  internally chambered for end piston  5112  and front piston  5108  with piston rod  5111  through subdividing bulkhead; an end cap seal  5110 ; a front cylinder cap  5107 ; a flow body  5150 ; a flow body cap; an inlet flow body seal sub  5101 ; an inlet regulator split flange port  5020 ; an outlet flow body seal sub  5106 ; and an outlet regulator split flange port  5025 . The internal arrangement of an end piston  5112  connected to piston rod  5111 ; front piston  5108  connected to piston rod  5111  and poppet assembly  5105 . Seawater inlet port  5001  has access to a volume of seawater between the end piston  5112  and end cylinder cap  5113 . Reservoir port  5320  has access to a volume of hydraulic fluid between the subdividing bulkhead of the cylinder body  5109  and the end piston  5112 . Pilot pressure port  5220  has access to a volume of hydraulic fluid between the subdividing bulkhead of the cylinder body  5109  and the front piston  5108 . Feedback port  5905  has access to a volume of hydraulic fluid between the front piston  5108  and the front cylinder cap. The poppet assembly  5105  rod passes through the front cylinder cap. 
       FIG. 15  illustrates a cutaway of the regulator  5000 . End piston  5112 , piston rod  5111 , front piston  5108 , and the poppet assembly  5105  are interconnected. Moving of this assembly towards the seawater inlet port causes the poppet to open and allow seawater to move into the flow body  5150  and vice versa. A constant hydrostatic force F end  is applied to the end piston  5112  via the seawater inlet port  5001  biasing the poppet assembly  5105  to open. A constant gage pressure force F acc  derived from the pilot accumulator  3200  pressure is applied to the front piston  5108  biasing the poppet assembly  5105  to open. A variable absolute pressure force F int  derived from the intensifier delivery pressure  1905  is applied to the front piston  5108  biasing the poppet assembly to close. A variable hydrostatic absolute pressure force F flow  derived from the seawater hydrostatic pressure with dynamic pressure loss due to flow through the flow body  5150  is applied to the poppet assembly  5105 . 
     The force balance equation is (F end +F acc )*Bias−F int −F flow =0. Where the resultant force of F end +F acc  represents the delivery pressure in absolute pressure (gage+hydrostatic), a decrease in F int  will cause the poppet assembly  5105  to open and begin flowing until F int  increases to close the poppet assembly  5105 . During flow through the flow body  5150 , a decrease in the apparent hydrostatic pressure is observed causing a reduction in F flow  causing a further bias to open the poppet assembly  5105  further. As flow through the flow body  5150  is a consequence of delivery fluid demand on the intensifier  1000  on feedback line  1905  causing F int  to reduce, as the intensifier catches up with flow demand, F int  will increase and bias the poppet assembly  5105  to close; further reducing flow through the flow body  5150 , consequently reducing the hydrodynamic reduction of F flow , further biasing the poppet assembly to close. In order to bias the regulator to maintain a constant closing pressure, F acc  is decreased by reducing the pilot accumulator  3200  pressure below the desired gage pressure of the intensifier delivery fluid and output  1900  header. 
       FIG. 16  illustrates the assembly of the reference pump module  3300  and reference reservoir  3100  and pilot accumulator  3200  in reference assembly  3000 . The pilot accumulator  3200 , reference reservoir  3100 , reservoir pressure transmitter  3121 , and pilot accumulator pressure transmitter  3221  are mounted into a manifold block with internal porting to connect to pilot accumulator reference tubing  3220 , reservoir circulation tubing  3120 , reference pump reservoir tubing  3133 , and reference pump accumulator tubing  3233 . The reference pump double acting pump module  3520 ; check valves  3530 ,  3531 ,  3532 ,  3533 ; and subplate mounted 3-way valve  3510  are mounted into a manifold block with internal porting between the mounted components and connections to reference pump reservoir tubing  3133 , reference pump accumulator tubing  3233 , reference pump stroke pilot tubing  3310 , reference pump stroke pilot tubing  3311 , and pilot accumulator increase/decrease selector pilot tubing  3312   
       FIG. 17  illustrates the schematic of the reference pump module where pilot signals  3310  and  3311  cause a double acting axial pump  3520  to back and forth as the respective pilot signals  3310  and  3311  are pressurized and vented in a mutually exclusive manner (e.g. both pilots are not energized at the same time). The check valves cause fluid to be moved through the 3-way valve  3510  resulting in moving fluid between  3133  and  3233 . The direction of movement is governed by the pilot signal  3312  acting on the 3-way valve  3510 . 
       FIG. 18  shows the action of pump  3520 . As hydraulic pilots  3310  and  3311  move the center piston in each direction, fluid at ports  3522  and  3523  is displaced in and out of the center chambers. The differential area between the piston  3511  rod end and piston end results in an intensification of pressure between that exerted at  3310  and an resultant at  3523 , allowing the pump to generate a pressure in excess of the piloting pressure. The swept volume of the pump is approximately 0.25 cubic inches per stroke, allowing pilot accumulator pressure to be adjusted in small increments. 
       FIG. 19  illustrates the schematic of the reference reservoir  3100  and pilot accumulator  3200 . The pilot accumulator  3200  provides a gage pressure reference (relative to the reference reservoir  3100  absolute pressure (one atmosphere)) for the regulator  5000 . The reservoir gross volume is a function of the accumulator net volume. The pressure transducers allow monitoring of the respective reservoir pressures for diagnostic purposes. A maximum of 2.5 gallons gross accumulator volume can satisfy regulator  5000  operation. The reference assembly  3000  is a closed system and does not discharge hydraulic fluid from the reservoir or pilot accumulator. 
     As fluid is pumped into the pilot accumulator  3200  from the reference reservoir  3100 , the precharge gas in the pilot accumulator  3200  is compressed and its hydraulic pressure increases. As fluid is pumped from the pilot accumulator  3200  to the reference reservoir  3100 , the gas expands and the accumulator hydraulic pressure decreases. The use of incremental increase and decrease of pilot accumulator  3200  pressure allows intensifier  1000  pressure delivery  1900  to be increased or decreased in a controlled manner without violent swings. The precharge pressure of the gas when the pilot accumulator  3200  is near half capacity, establishes it&#39;s median. The range of pressure adjustment is a function of the gross volume of the pilot accumulator  3200 . The gross volume of the reference reservoir  3100  is a function of the gross volume of the pilot accumulator  3200 . 
       FIG. 20  illustrates an exploded view of the intensifier  1000 . The intensifier  1000  is comprised of an outer barrel  1010 , elastomer mounting rings  1013 , an inner barrel  1020 , an inner barrel instrument package  1040 , an inner barrel instrument jumper  1058 , two inner barrel proximity sensors  1022 , a piston  1030 , a piston inner diameter seal  1031 , a piston outer diameter seal  1032 , an upper outer barrel flange  1011 , a regulator isolation valve  1053 , a pump isolation valve  1053 , a regulator pressure transducer  1054 , a lower outer barrel flange  1021 , a delivery pressure transducer  1054 , a instrumentation and power connector  1055 , a delivery pressure transducer instrument jumper  1056 , a regulator pressure instrument jumper  1050 , and a pump recharge tubing jumper  1057 . The inner barrel  1020  is attached to the lower outer barrel flange by means of a locking breach  1023 . The outer barrel flanges  1021  and  1011  are attached to the top and bottom of the outer barrel  1010 . The lower outer barrel flange  1021  incorporates a dry-mate subsea bulkhead connector  1055  to provide connection between the inner barrel instrumentation package and the intensifier junction box  1070 . The upper outer barrel flange  1011  incorporates subplate mounted piloted control valves  1053  for isolation of the seawater section of the intensifier  1000  from the regulator  5000  and the recharge pump  6000 . A subplate mounted pressure transducer  1054  is mounted to the upper outer barrel flange  1011  to provide pressure measurement of the internal seawater pressure in the intensifier  1000 . The lower outer barrel flange  1021  incorporates a subplate mounted control valve  1051  for isolating the delivery fluid section of the intensifier  1000  from the delivery fluid output and fill header. An alternative subplate mounted control valve  1059  may be substituted to allow the intensifier  1000  to be filled from either fluid delivery output and fill header  1900  or from an external fluid recovery reservoir  1901 . A subplate mounted pressure transducer  1054  is mounted to the lower outer barrel flange  1021 . The subplate mounted pressure transducers incorporate dry mate connectors, allowing the use of pressure balanced oil filled (PBOF) cables  1056  and  1050  to be interconnected to the intensifier junction box  1070  near the bottom of the intensifier  1000 . The instrument junction box  1070  is comprised of pressure housing with dry mate connections for; the seawater pressure instrument PBOF cable  1058 , the delivery fluid supply pressure instrument PBOF cable  1050 , the intensifier bulkhead PBOF cable  1060 , and the external underwater control system intensifier PBOF cable  1910 . The intensifier bulkhead PBOF cable is comprised of a multiconductor (copper) cable supporting separate conductors for 24 volt DC power and serial communications from the external underwater control system to the inner barrel communications port module  1120 . The external underwater control system intensifier PBOF cable  1910  is comprised of a multiconductor (copper and fiberoptic) cable supporting separate conductors for 24 volt DC power, fiber optic signal lines, and serial communications to the external underwater control system. 
     The geometry of the piston  1030  allows for a seawater annulus between the outer piston  1030  wall above the seal locations of the piston  1030 , and the inner diameter of the outer barrel above the highest position the seals may reach (inches above the seal location with the piston in its highest position). An extraction port  1060  and washout port  1060  are located slightly above these levels to allow the annular volume exposed to seawater to be evacuated or cleaned. The extraction port  1060  and annulus longitudinal cross-sectional area are sized to ensure turbulent flow is realized across the outer piston  1030  walls when seawater is pumped from the recharge port at low extraction flow rates. The turbulent flow provides for a self-cleaning action to the seawater interior of the intensifier  1000  when it is being recharged for subsequent operation. 
     Piston  1030  position is measured within the one-atmosphere conjoined chamber of the inner barrel  1020  and piston  1030  to derive remaining hydraulic volume of the hydraulic annulus. Piston  1030  position is measured relative to the inner barrel instrumentation package  1040 . Piston  1030  position at the full and empty position is measured by inductive proximity sensors  1022 . No sensor for measuring piston  1030  position crosses a pressure boundary, in contrast to prior art intensifier instrumentation. Fluid level in the inner barrel  1020  (as a consequence of unintended leakage across dynamic Piston seals) is measured relative to the inner barrel instrumentation package  1040 . 
       FIG. 21  illustrates the cross section view of the intensifier  1000  showing the piston  1030  in a fully retracted state, full of delivery fluid in  9800 . The intensifier  1000  is an annular piston pressure intensifier axial pump, which provides for pressure multiplication between the seawater supply side of the pump  1054  and the fluid delivery volume  9800 . 
       FIG. 22  illustrates a comparison of pressure intensifiers, intensifier  9814  and intensifier  1000  embodied in this apparatus. Intensifier  9814  uses a rod and piston arrangement  9802  which requires an annular volume  9801  between the piston and rod seal which must be vented to ambient pressure, otherwise leakage into this volume  9801  will cause the intensifier to hydraulically lock in place. Intensifier  9814  used for the generation of hydraulic power require the use of external one-atmosphere chambers  9814  to provide the vent required. 
     The intensifier  1000  of this embodiment uses a rod-less piston design utilizing dynamic seals on the inner and outer diameter of the piston  1030  skirt to provide the intensification area of the delivery fluid supply side  9800  of the intensifier  1000  relative to the piston  1030  head area. The piston skirt/seal travels between the outer barrel  1010  and inner barrel  1030  and over the inner barrel  1030  to define the hydraulic annular volume  9800  in which delivery fluid is pressurized. 
     The internal volume of the inner barrel  1020  and the piston  1030  provide a conjoined volume  9801  that increases and decreases as the piston  1030  moves up and down the outer barrel  1010 . This conjoined volume is a significant multiple of the hydraulic delivery volume, as opposed to a fraction of the volume seen in prior art intensifiers  9814 , and does not require the use of an external accumulator  9814 . Due to the configuration of this rod-less design, the volume of  9814  is utilized to incorporate position sensing instrumentation to measure piston  1030  elevation to derive volumetric measurement of  9800  without requiring the use of sensors operating at pressure within either  9811 ,  9800 , or ambient hydrostatic pressures. 
       FIG. 23  illustrates a cross section view of the inner barrel instrument package  1040 . The package  1040  is comprised of a cage  1042  containing a piston position sensor  1010 , fluid level sensor  1110 , cable and connector  1121  to the inner barrel  1020  piston down position proximity sensor  1022 , connector cable  1121  to the inner barrel  1020  piston up position proximity sensor  1022 , intensifier remote input/output computer node  1120 . The cage  1042  is secured to the top of the inner barrel  1020 . The inner barrel package  1042  is connected to the lower intensifier barrel flange bulkhead connector  1055 , via the inner barrel instrumentation cable  1058 . The interconnection cable  1055  is routed along the inside wall of the inner barrel  1020  to allow sensor  1110  visibility of the bottom for purposes of fluid incursion detection and measurement. 
       FIG. 24  illustrates the schematic view of the intensifier without the option of recharge from an external fluid recovery tank. 
       FIG. 25  illustrates the schematic view of the intensifier with the option of recharge from an external fluid recovery tank via  1910 . 
       FIG. 26  illustrates and exploded view of the accumulator  2000 . The accumulator  2000  is comprised of the same outer barrel  1010  as used in the intensifier  1000 , two elastomer mounting rings  1013 , an upper outer barrel flange  2200 , a lower outer barrel flange  2100 , a delivery pressure transducer  1054 , a delivery pressure transducer instrument jumper  1056 , a liquid level sensor  2110 , an accumulator junction box  2070 , and a caged poppet valve  2120 . The outer barrel flanges  2200  and  2100  are attached to the top and bottom of the outer barrel  1010 . The lower outer barrel flange  2100  incorporates a subplate mounted control valve  2050  for isolating the delivery fluid section of the accumulator  2000  from the delivery fluid output and fill header. A subplate mounted pressure transducer  1054  is mounted to the lower outer barrel flange  2100 . The subplate mounted pressure transducers incorporate dry mate connectors, allowing the use of pressure balanced oil filled (PBOF) cables  1056  and  1050  to be interconnected to the accumulator junction box  2070  near the bottom of the accumulator  2000 . The accumulator junction box  2070  is comprised of pressure housing with dry mate connections for the delivery fluid supply pressure instrument PBOF cable  2061 , the accumulator liquid level sensor PBOF cable  2062 , and the external underwater control system PBOF cable  1910 . The external underwater control system intensifier PBOF cable  1910  is comprised of a multiconductor (copper and fiberoptic) cable supporting separate conductors for 24 volt DC power, fiber optic signal lines, and serial communications to the external underwater control system. The upper outer barrel flange  2200  incorporates a gas charge valve  2210  to allow the accumulator to be precharged with nitrogen at a pressure appropriate to the deployment depth required. 
       FIG. 27  illustrates the caged float valve  2120  used in the accumulator to isolate the delivery fluid output and prevent loss of precharge gas at low liquid levels. The poppet valve  2123  is spring loaded to open without the weight of the float  2121 . When the liquid level rises, the float  2121  rises and allows the poppet valve to open. Use of the cage  2122 , allows the use of this assembly  2120  without the need for mechanical interconnections between the caged float valve  2120  and the upper outer barrel flange  2200 . 
       FIG. 28  illustrates the arrangement of the liquid level sensor  2110 , pressure transducer  1054 , caged poppet valve  2120 , and accumulator isolation valve  2050 . Accumulator junction box  2070  allows interconnection of the accumulator  2000  instrumentation to the external underwater control system via  1910 , allowing for consistency of mechanical interface between use of accumulator  2000  and intensifier  1000 . The liquid level sensor  2110  utilizes a time-of-flight acoustic ranging technique to measure the distance to the liquid free surface in the accumulator. On discharge and recharging of the accumulator  2000 , the delivery fluid may develop foam or froth at the free surface. Ranging upward to the free surface allows an accurate measurement of distance sufficient to derive useable fluid volume in the accumulator. 
       FIG. 29  illustrates the recharge pump  6000  assembly. The recharge pump  6000  is comprised of an electric motor and drive unit  6030 , a positive displacement pump  6003  that exhausts to ambient seawater, a pressure compensation assembly  6010  with sea water inlet  6960 , a dry-mate underwater electrical power connector  6971 , and a dry mate underwater instrument power and communications connector  6911 . The recharge pump  6000  allows seawater to be pumped from equipment that is at or lower than ambient seawater pressure, to exhaust the seawater at ambient seawater pressure. 
       FIG. 30  illustrates an exploded view of the recharge pump  6000 . The recharge pump  6000  comprises a seawater exhaust port  6001 ; seawater suction port  6013 , seawater pump and housing  6003 , pump shroud  6004 , shaft coupler and housing  6005 , lower motor housing and motor  6006 , upper motor housing  6007 , electronics housing  6009 , and suction balance bladder  6010 . The seawater suction port provides fluid communication to the seawater pump  6003  suction as well as pressure communication to the seawater pump  6003  case drain port and lower motor housing  6006 . The electric motor contained in the split housing  6006  is immersed in dielectric lubricant and operates at suction pressure as communicated to the housings by port  6012 . A coupling and housing  6005  mechanically connect the motor and pump through a rotating seal. The seawater pump  6003 , coupler housing  6005  and motor housing  6006  and  6007  operate with a case pressure as communicated through the coupling housing  6005 . 
       FIG. 31  illustrates a schematic view of the recharge pump  6000 . The controller/driver  6930  utilizes DC voltage  6970  to generate 3-phase stator voltage and frequency on  6932  to rotate the motor  6100  with feedback from resolver signals  6933  from the motor  6100 . The motor temperature is monitored through RTD leads  6931  from the motor windings  6100 . The controller/driver  6930  has the capability of controlling speed and torque developed by the motor  6100 , in order to maintain a constant speed and torque with the DC voltage at nominal values. As the DC voltage  6970  level drops, the controller/driver  6930  will reduce motor speed while maintaining torque. This allows the pump  6003  to maintain operation with diminishing DC voltage while pumping seawater suction  6013  to ambient pressure  0001 . The motor  6100  and pump  6003  are mechanically coupled through the coupler housing  6005  that provides a protection from seawater intrusion into the pump  6003  case and motor. Insulating dialectric fluid is used in the motor housing  6006  and  6007 , as well as in the pump  6003  crankcase. The dielectric lubricating fluid is pressure compensated relative to the pump suction pressure at  6013  which is connected to the intensifier recharge connection  1057  through the compensation bladder  6010 . The controller/driver  6930  is located in housing  6009  which is operated at one atmosphere pressure. The connections  6931 ,  6932 ,  6933  are connected through the intervening bulkhead between  6009  and  6007 , through the use of dry-mate electrical bulkhead connectors. The controller/driver  6930  is thermally bonded to the housing  6009  wall to maximize heat transfer to the ambient seawater. The controller/driver  6930  is connected to the external underwater control system via a dry-mate bulkhead connector for  6910 , and dry-mate bulkhead connector for  6970  for connection to the power pack  7000 . 
       FIG. 32  illustrates an assembly view of the power pack  7000 . The power pack  7000  utilizes incoming surface supply voltage at 160-250 volts AC at a 1.6 amps to develop DC voltage for capacitive storage. The capacitive storage is maintained at a level to allow operation of the recharge pump for a limited period of time. The power pack  7000  also utilizes regenerated DC voltage from the regenerator  8000  to charge capacitive storage at a faster rate than surface supplied voltage. The power pack is monitored and controlled by an external underwater control system to allow for isolation of incoming surface supply voltage, isolation of outgoing DC voltage to the recharge pump  6000 , and isolation of incoming regenerator power. The power pack  7000  incorporates an LED which allows for visual confirmation that the capacitive storage of the assembly is null and safe for removal of the upper flange. The electrical components of the power pack are housed in pressure housing with a upper flange to allow the electrical components to be removed as a complete assembly. 
       FIG. 33  illustrates a cutaway view of the power pack  7000 . The power pack  7000  is comprised of a pressure housing  7005 ; an upper flange  7006 , an instrument package hanger  7200 , a power converter/relay  7300 , and an array of ultracapacitor modules  7400 . The upper flange is comprised of a sight glass  7113 , an instrumentation power and communications connector  7111 , a surface power connector  7112 , a DC power input connector  7113 , and a DC power output connector  7114 . The power converter/relay  7300  assembly is comprised of an incoming relay module  7310 , a power controller module  7330 , and an outgoing relay module  7330 . The power converter/relay  7300  assembly incorporates structures  7301  that mechanically fasten  7401  to the instrument package hanger  7200  and mechanically fasten to the uppermost ultracapacitor module  7400  in the ultracapacitor array. The power converter/relay  7300  incorporates a DC voltage connection (power and ground)  7402  to the uppermost ultracapacitor module  7400  in the ultracapacitor array. The power converter/relay incorporates cable connections to the upper flange  7006  connectors  7111 ,  7112 ,  7113 , and  7114 . The power converter/relay assembly incorporates a LED indicator on top of the assembly that is visible through the sight glass  7113 . The ultracapacitor modules  7400  are vertically interconnected mechanically and electrically through mechanical fasteners  7401  and electrical connectors  7402 . The electrical connections  7402  allow for a series connection of modules to form a single capacitive device. The ultracapacitor module  7400  is formed of a plurality of ultracapacitor elements electrically connected in series to form a single capacitive unit. The individual ultracapacitors  7405  are mechanically arranged to fit in a cylindrical form, and mechanically linked to structural elements allowing for mechanical connection to fasteners  7401 . 
       FIG. 34  illustrates a schematic view of the power pack  7000 . Incoming surface AC power  0015  can be isolated through relay  7311 . Incoming DC power from the regenerator  8000  or other power packs  7000  can be isolated through relay  7312 . The LED  7313  provides an indication of stored voltage present in the ultracapacitor array of  7400 . The power controller module  7330  receives instrumentation power and communications on  7910 , and is capable of operating in the absence of DC or AC power to the power pack. The module  7330  controls the incoming and outgoing relays. 
     The power packs can be used in multiple arrangements with parallel input power from  0015 , and parallel output power to  6970  to extend operating times of the recharge pump  6000 . 
       FIG. 35  illustrates an assembly view of the regenerator. The regenerator  8000  utilizes the flow of seawater through impeller inlet and outlets  8014  to the screen, in order to parasitically drive a flywheel alternator  8010  for generation of electrical power in use of recharging the power pack  7000 . The flow rate through the regenerator  8000  is approximately 600 gpm for a period of 2 minutes, generating significant power from a small pressure drop across the regenerator  8000 . Electrical power is made available through connection  8012 , and the regenerator  8000  is connected to the external underwater control system via connector  8013 . 
       FIG. 36  illustrates an exploded view of the regenerator  8000 . The regenerator  8000  is comprised of an Impeller housing  8005  with inlet and outlet ports  8014 ; an impeller transmission housing  8006 ; a flywheel/alternator housing  8007 , and a power converter/controller housing  8009 . The impeller housing  8005  contains an impeller and magnetic coupling to eliminate mechanical losses the pressure seals across the pressure bulkhead of the impeller transmission housing  8006 . The impeller transmission housing  8006  contains a step-up transmission to multiply impeller speed, an overrunning clutch, and a flywheel/alternator to generate three phase AC voltage. The power converter/controller housing  8009  contains a rectifying buck boost DC power supply to provide DC voltage output  6970  to the power pack  7000 . The power converter/controller provides for remote monitoring and control via  8910  to an external underwater control system. 
       FIG. 37  illustrates the apparatus configured for use with only accumulators  2000  (refer to  FIG. 6 ) in water depths less than  6000  feet as used in a subsea blowout preventer stack. The benefit of this configuration is the ability to utilize a BOP stack frame design to accommodate the four accumulators for shallow waters, and extend the operating depth by replacement of the accumulators  2000  with intensifiers  1000 . The ease of replacement is supported by the use of a common outer barrel  1010  with common mounting accessories. 
       FIG. 38  illustrates the apparatus configured for use with accumulators  2000  and intensifiers  1000  (refer to  FIG. 7 ) in water depths less than  9000  feet as used in a subsea blowout prevent stack. This embodiment extends the accumulator  2000  on configuration of  FIG. 37 , through the addition of the screen  4000 , regulator  5000 , reference  3000 , and replacement of two accumulators  2000  with two intensifiers  1000 . 
       FIG. 39  illustrates the apparatus configured for use with intensifiers  1000  (refer to  FIG. 8 ) in water depths less than  9000  feet as used in a subsea blowout prevent stack. This embodiment extends the hybrid configuration of  FIG. 37 , through the replacement of the two remaining accumulators  2000  for two intensifiers  1000 . 
       FIG. 40  illustrates the apparatus configured for use with intensifiers  1000  (refer to  FIG. 9 ) in water depths greater than  9000  feet as used in a subsea blowout prevent stack. This embodiment utilizes the configuration shown in  FIG. 39 , and adds the recharge pump  6000  and power pack  7000  to further extend the operating depth of the stack. 
       FIG. 41  illustrates the apparatus configured for use with intensifiers  1000  (refer to  FIG. 10 ) in water depths greater than  9000  feet as used in a subsea blowout prevent stack. Recharge times are decreased in this embodiment through the addition of the regenerator  8000  to the BOP stack. 
       FIG. 42  illustrates the apparatus configured for use with intensifiers  1000  (refer to  FIG. 10 ) in water depths greater than  6000  feet as used to support subsea BOP stack, subsea production tree, subsea distribution unit, subsea production manifold, and other subsea electro-hydraulic consumers of hydraulic and electric power. This configuration utilizes a mudmat foundation  0100  with protective framework. External access to the configuration is via Remote Operated Vehicle (ROV) utilizing the panel  0110 , and hydraulic flying lead stabplate  0111  and electric flying lead stabplate  0112  to connect between the apparatus and the external subsea equipment. 
     While specific embodiments have been shown and described, modifications can be made by one skilled in the art without departing from the spirit or teaching of this invention. The embodiments as described are exemplary only and are not limiting. Many variations and modifications are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited to the embodiments described, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.

Summary:
A subsea system including a frame including an intensifier, the intensifier providing structural support to the frame and capable of providing pressurized delivery fluid. The intensifier includes an intensifier chamber and a delivery fluid chamber separated by a piston, the intensifier chamber capable of receiving ambient pressure to provide a pressure on the delivery fluid through the piston. Also, a regulation system regulates the amount of ambient pressure communicated to the intensifier chamber to maintain the delivery fluid pressure substantially constant as the delivery fluid is depleted.