Pressure housing for in-water pressure based systems

Details Pressure housing for in-water pressure based systems Pressure housing for in-water pressure based systems

2001-12-27

2003-05-27

Williams, Hezron (Department: 2856)

Measuring and testing

Instrument casing

C073S001570, C073S001690, C073S031040, C073S031050, C073S292000, C073S299000

Reexamination Certificate

active

06568266

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to pressure housing for in-water pressure based systems. More particularly, this, invention relates to a novel device for (1) improving the life of the transducers and electronics of underwater systems by maintaining a humidity-free and clean environment around them by avoiding the entry of humidity, dust, or any suspended particles in the air during occasional data offloading and battery replacement in a humid and dust-laden field station; (2) improving the ease of closing and opening of the pressure housing by the use of a novel arrangement thereby avoiding the use of conventionally employed cumbersome protruding and corrosion-prone locking devices such as screws, bolts, or clamps; and (3) implementing reliable transmission of water pressure to the pressure port of the transducer, simultaneously minimizing the errors arising from dynamic pressure effects, preventing its chemical corrosion from saline water, and arresting, bio-fouling in the vicinity of the pressure inlet.
BACKGROUND OF THE INVENTION
Hitherto known in-water pressure based systems [V. B. Peshwe, S. G. Diwan, A. Joseph, and E. Desa, “Wave and Tide Gauge”,
Indian Journal of Marine Sciences,
Vol. 9, pp. 73-76 (1980)] describes a Wave and Tide Gauge wherein the underwater electronics and the pressure sensor are placed and secured on a circular brass plate which fits into a brass cylinder. O-rings are used for sealing the underwater unit, which is mounted on a steel base. All steel components are nickel-plated, and the brass components are coated with paint. The pressure sensitive metallic diaphragm of the pressure transducer is protected against chemical corrosion with the use of an oil-filled neoprene nipple attached to a stainless steel coupler located on the flat face of the removable end-plate and hydraulically connected to the pressure port. The end-plate is locked to the flange of the cylindrical housing with the use of four bolts, washers, and nuts that are located in diametrically opposite sense. The disadvantage of this arrangement is the occasional damage to the neoprene rubber nipple arising from fish bites, resulting in the loss of oil that protects the pressure port of the transducer against chemical corrosion. Another drawback is protrusion of bolts and nuts, which provides a poor aesthetic appearance of the housing.
An alternate system, [A. Joseph and E. S. Desa, “A Microprocessor-Based Tide Measuring System”,
Journal of Physics, E. Scientific Instruments,
Vol. 17, pp. 1135-1138 (1984)], describes a tide measuring system that consists of a cylindrical underwater pressure housing made of brass, containing a Paroscientific quartz pressure transducer. The said pressure transducer is located on a circular brass base-plate of the housing, with the pressure inlet exposed t seawater through an O-ring-protected orifice on the base-plate. The entire housing is sealed with another larger O-ring located between the cylindrical housing and its base-plate. The said base-plate is mounted to the circular flange of the cylindrical housing with the use of 6 units of stainless steel bolts, washers, and nuts. A drawback of this methodology of sealing the pressure housing is that special care has to be taken to tighten the diametrically opposite bolts one at a time. Failing to do so can damage the O-ring by exceeding its elastic limit, thereby resulting in the possibility of leakage of the pressure housing and the damage of the transducer. Another drawback observed was that the underwater connector used for the transfer of data to an external readout unit suffered chemical corrosion after extended submergence in seawater. The hydraulic coupling device incorporated with the Paroscientific quartz pressure transducer comprises a silicone-oil-filled flexible plastic capillary tube of internal diameter ~1 mm and length ~200 mm, having one end attached to the pressure port of the transducer and the other end connected to the end-cap of the transducer housing. The drawback observed with this hydraulic coupling device in field studies is a slow leakage of oil over time.
Another system, [A. Joseph and E. Desa, “An Evaluation of Free- and Fixed-Vane Flow Meters with Curved- and Flat-Bladed Savonius Rotors”,
Journal of Atmospheric and Oceanic Technology, American Meteorological Society,
Vol.11, No.2, pp.525-533 (1994)] describe two types of current meters-cum-depth indicators that use in-water pressure housing to locate sensors and electronics printed circuit boards. In these instruments the pressure housing is closed with an end-plate assembly that formed part of the supporting mechanism for the water current sensor. The pressure sensor used for estimation of water depth is located on a horizontal step of the pressure housing. The said pressure housing is attached to the end-plate assembly with the use of four equally spaced bolts. Two disadvantages observed with this arrangement are (1) protruding locking bolts and (2) a protruding pressure inlet that is vulnerable to deterioration in pressure measurement accuracy resulting from the adverse influence of flows, waves, or a combination of flows and waves as discussed by A. Joseph, J. A. E. Desa, P. Foden, K. Taylor, J. McKeown, and E. Desa [in: “Evaluation and performance enhancement of a pressure transducer under flows, waves, and a combination of flows and waves,
Journal of Atmospheric and Oceanic Technology, American Meteorological Society,
Vol. 17, No. 3, pp. 357-365 (2000)].
In yet an other version of in-water pressure devices for measurements of water current, water level, and many other oceanographic parameters, Aanderaa Instruments (Norway) uses a cylindrical metallic housing having a removable end-cap at one end, and a fixed end-cap at the other end, wherein the removable end-cap is locked with the use of two metallic clamps that are hooked into slots that are carved out on the diametrically opposite positions on the periphery of the end-cap and the cylindrical housing. In these devices the pressure transducer's pressure inlet protrudes out and, therefore, suffers from pressure-measurement errors induced by various kinds of water motion in its vicinity.
The principal drawback with all conventional underwater pressure housings that are constructed from metal and whose metallic end-caps are locked with the use of devices such as metallic screws, bolts, or clamps is that they suffer from chemical corrosion after prolonged exposure to seawater, and makes opening of the end-plates usually difficult. Further, the presence of these protruding devices reduces the aesthetic appearance of the pressure housing.
OBJECTS OF THE INVENTION
The main object of the present invention is to improve the life of the transducers and the electronics of any underwater systems by maintaining a humidity-free and clean environment around them by avoiding the entry of humidity, dust, or any suspended particles in the air during occasional data offloading and battery replacement in a humid and dust-laden field station.
Another object of the present invention is to improve the ease of closing and opening of the pressure housing by the use of a novel arrangement thereby avoiding the use of conventionally employed cumbersome protruding and corrosion-prone locking devices such as screws, bolts, or clamps.
Yet another object of the present invention is to implement reliable transmission of water pressure too the pressure port of the transducer, simultaneously minimizing the errors arising from dynamic pressure effects, preventing its chemical corrosion from saline water, and arresting bio-fouling in the vicinity of the pressure inlet.
SUMMARY OF THE INVENTION
The novel pressure housing for in-water pressure based systems of the present invention provides for:
(1) Improving the life of the transducers and the electronics of any underwater systems by maintaining a humidity-free and clean environment around them by avoiding the entry of humidity, dust, or any suspended particles in the air during occasi

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