1. An electro-hydraulic process control system in a sub-sea production installation, comprising:
a top-side hydraulic power unit driven and controlled to generate and supply hydraulic power to a process control unit of the sub-sea production installation at a steady-state operation mode;
a sub-sea hydraulic power unit driven and controlled to generate and supply hydraulic power to the process control unit of the sub-sea production installation at a transient-state operation mode;
an umbilical comprising small bore tubing feeding hydraulic power from the top-side hydraulic power unit, and cables feeding electric power for operation of the sub-sea hydraulic power unit, and
a control unit configured to control the sub-sea hydraulic power unit between a stand-by mode and an operative mode
wherein the sub-sea hydraulic power unit comprises a pump driven by an electric motor, the pump being operable and controlled in the transient-state operation mode to boost a pressure of hydraulic fluid returning from the process control unit to a pressure required for operating process and safety valves of the process control unit.
2. The control system according to claim 1, further comprising:
a medium pressure accumulator bank configured to accumulate hydraulic fluid at operating pressure, and
a low pressure accumulator bank configured to accumulate hydraulic fluid at return pressure,
wherein the pump is operable to charge the medium pressure accumulator bank with hydraulic fluid from the low pressure accumulator bank.
3. The control system according to claim 2, further comprising:
a check valve configured to return hydraulic fluid supplied through the umbilical through the umbilical to the top-side hydraulic power unit in a fluid circulation mode, in a closed loop system, and at a pressure independent of the control system operating pressure.
4. The control system according to claim 3, further comprising:
a pressure vessel configured to contain components of the sub-sea hydraulic power unit, and
selectively operable directional control valves and a first return flow line and a second return flow line configured to return hydraulic fluid in circulation mode to the top-side hydraulic power unit.
5. The control system according to claim 4, wherein the first return flow line exits the pressure vessel from a bottom region thereof, extracting hydraulic fluid and particulate matter deposited in the pressure vessel, and the second return flow line exits the pressure vessel from a top region thereof, extracting hydraulic fluid and gaseous matter eventually accumulated in the pressure vessel.
6. The control system according to claim 5, further comprising:
an eductor connected to the first return flow line and the second return flow line, wherein the eductor is powered by the hydraulic pressure supplied through the umbilical and is operative to accelerate the hydraulic fluid extracted from a bottom region and a top region of the pressure vessel, respectively.
7. The control system according to claim 1, further comprising:
a bridge circuit emergency shut down system comprising at least two sets of directional control valves connected in series, each set including at least two directional control valves connecting in parallel the supply line and the return line, wherein the directional control valves electrically powered through the umbilical and controlled into a normally closed position.
8. The control system according to claim 7, wherein the directional control valves of the emergency shut down system are controllable individually or in pairs into an open position, enabling operational test of all valves in the system without loss of production in the sub-sea production installation.
9. A method for operating a process control unit of an electro-hydraulic process control system in a sub-sea production installation, the method comprising:
feeding hydraulic power, via an umbilical, from a top-side hydraulic power unit for operating the process control unit in a steady-state operation mode of the process control system;
feeding electric power, via the umbilical, for operating a sub-sea hydraulic power unit,
controlling the sub-sea hydraulic power unit between a stand-by mode and an operative mode for operating the process control unit, in a transition operation mode of the process control system, and
boosting, by said sub-sea hydraulic power unit, the pressure in hydraulic fluid returning from the process control unit into a higher pressure required for operating process and safety valves of the process control system.
10. The method according to claim 9, further comprising:
separating, in a circulation mode, a flow of hydraulic fluid supplied via the umbilical from a flow of hydraulic fluid required to operate the process control unit, and
returning the supplied hydraulic fluid via the umbilical in a closed loop system.
11. The method according to claim 10, further comprising:
extracting contaminants from the hydraulic fluid, at sub-sea level, in the circulation mode.
12. The method according to claim 11, further comprising:
depositing particulate contaminants at a bottom region of a pressure vessel,
accumulating gaseous contaminants in a top region of said pressure vessel, and
selectively extracting hydraulic fluid with particulate or gaseous contaminants from said pressure vessel.
13. The method according to claim 12, further comprising:
accelerating the return flow of hydraulic fluid by utilizing an eductor.
14. The method according to claim 9, further comprising:
providing a redundant emergency shut down system by the introduction of multiple emergency shut down valves, electrically controlled into a normally closed position and individually operable into an open position for test purposes.
15. The method according to claim 9, further comprising:
stepping down the electric power supplied via the umbilical, to a low voltage alternating current suitable for powering an electric motor and pump of the sub-sea hydraulic power unit.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of imaging a tear film layer of an eye, the method comprising:
acquiring a plurality of optical coherence tomographic images of said eye between consecutive blinks of said eye, said tomographic images depicting a cross-section of a full thickness of a cornea and a full thickness of the tear film layer of the eye and further depicting an upper tear meniscus and a lower tear meniscus of the eye;
wherein said plurality of said tomographic images depict said tear film layer as distinct from the cornea of said eye.
2. The method of claim 1, wherein at least one of said tomographic images depicts a contact lens as distinct from said cornea of said eye.
3. The method of claim 2, wherein said at least one of said tomographic images depicts a pre-lens tear film layer as distinct from said contact lens and said cornea of said eye.
4. The method of claim 3, further comprising measuring a thickness of at least one of said contact lens and said pre-lens tear film layer.
5. The method of claim 1, further comprising measuring a thickness of said tear film layer.
6. The method of claim 5, wherein measuring said thickness of said tear film layer comprises measuring said thickness multiple times over time.
7. The method of claim 6, wherein measuring said thickness of said tear film layer comprises:
processing data from a first image of said tomographic images to generate an average reflectivity profile;
determining a distance between a first peak and a second peak of said average reflectivity profile, wherein said first peak corresponds to an interface between air and said tear film layer, and wherein said second peak corresponds to an interface between the tear film layer and said cornea; and
correlating said distance between said first peak and said second peak to a first thickness of said tear film layer.
8. The method of claim 7, further comprising averaging said first thickness obtained from said first image with a second thickness obtained from a second image of said tomographic images.
9. A method of imaging a tear film layer of an eye, the method comprising:
acquiring a plurality of images of said eye between consecutive blinks of said eye;
wherein, the plurality of images depict a full thickness of the tear film layer as distinct from the cornea of said eye, and depict an upper tear film meniscus and a lower tear film meniscus as distinct from the cornea of said eye.
10. A method of imaging an eye, the method comprising:
measuring with an instrument a cross-sectional thickness of a tear film layer of said eye at least twice between consecutive blinks of said eye, wherein said instrument does not physically contact said eye during said measuring.
11. The method of claim 10, further comprising measuring a reflectivity of said tear film layer.
12. A method of imaging an eye, the method comprising:
measuring with an instrument a cross-sectional meniscus height of a tear film of said eye at least twice between consecutive blinks of said eye, wherein said instrument does not physically contact said eye during said measuring.
13. A system for evaluating a tear film layer of an eye, the system comprising:
an optical coherence tomography device configured to acquire at least two images of said tear film layer between consecutive blinks of said eye, said tomographic images depicting a cross-section of a full thickness of a cornea and a full thickness of the tear film layer of the eye, and further depicting an upper tear meniscus and a lower tear meniscus of the eye; and
an executable program configured to process said at least two images acquired by said optical coherence tomography device;
wherein said executable program is further configured to determine a thickness of said tear film layer.
14. The system of claim 13, wherein hardware comprises said executable program.
15. The system of claim 13, wherein software comprises said executable program.
16. A system for evaluating a tear film layer of an eye, the system comprising:
means for acquiring at least two images of said tear film layer between consecutive blinks of said eye, said images depicting a cross-section of a full thickness of a cornea and a full thickness of the tear film layer of the eye, and further depicting an upper tear meniscus and a lower tear meniscus of the eye; and
means for determining a thickness of said tear film layer.
17. A diagnostic device comprising an optical coherence tomography system configured to measure a full cross-sectional thickness of a tear film layer of an eye at least twice between consecutive blinks of said eye.
18. A diagnostic device comprising an optical coherence tomography system configured to measure a cross-sectional thickness of an upper tear film meniscus and a lower tear film meniscus of an eye at least twice between consecutive blinks of said eye.
19. A method of imaging an eye, the method comprising measuring a full cross-sectional thickness of a tear film layer of said eye at least twice between consecutive blinks of said eye.
20. A method of imaging an eye, the method comprising measuring a cross-sectional thickness of an upper tear film meniscus and a lower tear film meniscus of said eye at least twice between consecutive blinks of said eye.