Design of double-coated optical fibers to minimize long-term hydrostatic-pressure-induced microbending losses

2001 ◽  
Vol 26 (3) ◽  
pp. 128 ◽  
Author(s):  
Sham-Tsong Shiue
Keyword(s):  
Hydrostatic Pressure ◽  
Optical Fibers

A Deep-Ocean Mass Spectrometer to Monitor Hydrocarbon Seeps and Pipelines

2005 ◽  
Author(s):  
Gary M. McMurtry ◽  
John C. Wiltshire ◽  
Arnaud Bossuyt
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
Mass Spectrometer ◽  
Deep Ocean ◽  
Rechargeable Batteries ◽  
Vacuum System ◽  
Power Cable ◽  
Electron Multiplier ◽  
Trace Contaminant

New developments in instrumentation for ocean environmental engineering are allowing unprecedented levels of trace contaminant measurement in the deep ocean. With funding from the U.S. National Science Foundation (NSF), our engineering design team constructed a new mass spectrometer-based in situ analysis system for work in the deep ocean environment over prolonged deployment periods. Our design goals were a depth capability of up to 4,000 m water depth (400 bars hydrostatic pressure) and autonomous operation for periods of up to six months to a year, depending upon the type of external battery system used or other deployment circumstances, e.g., availability of a power cable or fuel cell power source. We chose a membrane introduction mass spectrometry (MIMS) sampling approach, which allows for dissolved gases and volatile organics introduction into the mass spectrometer vacuum system. The MIMS approach and the hydrophobic, silicon-coated membrane chosen both draw upon our previous experience with this technology in the deep ocean. The membrane has been tested to 400 bars in a series of long-term hydrostatic pressure tests, which extend the 200-bar working depth rating of this membrane by a factor of 2. Long-term deployment capability of the moderately powered, approximately 100 W system, was accomplished by power management of the embedded computer system and custom electronics with Windows-based and custom software now fully-developed and bench tested. The entire system fits within a 6.5-inch outside diameter pressure housing that is approximately five feet long. It consists of a 1 to 200 amu range quadrupole mass spectrometer equipped with Faraday and electron multiplier detectors, compact turbo-molecular and backing diaphragm vacuum pumps, internal rechargeable batteries, and internal waste vacuum chamber. Sample routing past the MIMS is accomplished by computer-controlled solenoid valves. We designed the pressure housings of both 6AL4V and type 2 titanium alloys that are rated to working depths of >4,000 m and are essentially corrosion proof over long-term deployments. We designed and integrated a fail-safe valving system for both rapid response to high-pressure MIMS failure and a pressure-switch circuit and high-pressure solenoid valve to detect and protect against slow leaks of the MIMS. To route sample waters to the MIMS-based instrument, we also designed and built a rugged plastic plenum that couples to the face of the sampler head, the latter of which consists of the MIMS inlet and a full-ocean rated thermister temperature probe with an operational range from −5 to 50°C. These instrumentation innovations will be described in the paper.

Integration of Hydrostatic Pressure Information by Identified Interneurones in the Crab Carcinus maenas (L.); Long-Term Recordings

2001 ◽  
Vol 54 (1) ◽  
pp. 71-79 ◽  
Author(s):  
P. J. Fraser ◽  
A. G. Macdonald ◽  
S. F. Cruickshank ◽  
M. P. Schraner
Keyword(s):  
Hydrostatic Pressure ◽  
Gas Phase ◽  
Progress Monitoring ◽  
Carcinus Maenas ◽  
Shore Crab ◽  
Pressure Sensitive ◽  
Animal Navigation ◽  
Tidal Changes ◽  
Pressure Changes

This paper was first presented at the RIN97 Conference held in Oxford under the auspices of the Animal Navigation Special Interest Group, April 1997.Migrating species may utilise hydrostatic pressure. In the aquatic environment, hydrostatic pressure changes much more rapidly than in air. In shallow water, tidal changes will impose larger percentage changes on organisms than those experienced in deep water. Small changes in pressure often cause locomotion (barokinesis) accompanied by orientation to light or gravity, often partially compensating for the equivalent depth change. Until recently, identification of hydrostatic pressure receptors without a gas phase has proved elusive, but it is now known that thread hair receptors in the statocyst of the shore crab Carcinus maenas respond to small changes in hydrostatic pressure. Using a tide machine, the responses of thread hairs to sinusoidally changing pressure cycles have been examined, and this paper reports progress monitoring this receptor and making long-term recordings from hydrostatic pressure sensitive pathways in the crab's nervous system.

Conical Acrylic Windows Under Long-Term Hydrostatic Pressure of 5000 psi

1972 ◽  
Vol 94 (3) ◽  
pp. 843-848
Author(s):  
J. D. Stachiw
Keyword(s):  
Hydrostatic Pressure ◽  
Diameter Ratio ◽  
Axial Displacement ◽  
Included Angle ◽  
Temperature Range ◽  
Hydrostatic Loading ◽  
General Service

Conical acrylic windows with included angle 30 deg ≤ α ≤ 150 deg and thickness to minor diameter ratio of 0.375 ≤ t/D ≤ 1.00 have been subjected to 5,000 psi sustained hydrostatic loading of 1,000 hr duration in 65–75 deg F temperature range while the axial displacement of the windows through the flange has been monitored. The magnitude of axial displacement was found to be a function of α, t/D, temperature and duration of loading. Only windows with t/D ratios ≥1.000, 0.625, 0.500, 0.500, and 0.500 for 30, 60, 90, 120, and 150 deg conical angles, respectively, were found to be free of cracks. It is recommended that only windows with included angle α ≥ 60 deg be utilized for general service (long-term and cyclic) under 5,000 psi maximum hydrostatic pressure. The corresponding t/D ratios recommended for general service are 0.750 for α = 60 deg, and 0.625 for α ≥ 90 deg.

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