Fluid-activatable device for shut-off under excess flow...

Fluid handling – Line condition change responsive valves – Safety cut-off requiring reset

Reexamination Certificate

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Details

C137S521000

Reexamination Certificate

active

06581629

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a fluid-activatable shut-off device in an embodiment as a shut-off valve or damper for the complete or partial blocking of the flow passage. The shut-off device may generally be used in an embodiment as moveable dampers, profiles or similar installed in pipes, channels or other flow passages with the object of arranging a damper/profile in the fluid flow in the desired position by using energy present in the flow passage. The invention used in an embodiment as a valve, comprises a valve housing formed with a flow passage therethrough and a movably supported valve body, movable between an open valve position, in which the valve body is mainly withdrawn from the flow passage, which is thereby essentially cleared, and a closed valve position, in which the valve body blocks the flow passage and closes the valve.
SUMMARY OF INVENTION
The valve according to the invention is generally meant to be mounted into a pipeline, a channel or similar, which carries a fluid (air, water, oil or other liquid- or gaseous media). The valve body is in contact with the flowing fluid and is subjected to compressive and frictional forces. The valve body is arranged to close the valve whenever said forces exceed predetermined values. The amount of the forces varies with the fluid pressure, fluid density, flow rate and viscosity.
The valve is particularly meant to allow shut-off of a liquid or gas flow which intentionally or erroneously is brought to exceed a predetermined upper rate.
The lifting surface of the valve is generally related to the parameters that are influential, according to the formula:
Shut-off:
The formula for lifting force:
L
=1/2
·C
L
·&rgr;·A·V
2
In which:
L Lifting force
C
L
=Coefficient (empirical, expresses frictional properties of the lifting surface versus fluid rheology)
&rgr;=Fluid density (influenced by pressure, temperature and fluid compressibility)
A=Surface area (effective lifting surface)
V=Fluid flow rate
Abnormal flow conditions of a flowing fluid arise in connection with, among other things, pipeline breaks which may be caused by accidents such as explosions, fires and the like, in which abnormal flow conditions of the fluid may contribute to, among other things, greater amounts of undesired liquid/gas being supplied to a possible fire condition.
Generally, the present invention aims at utilizing a changed flow rate and perhaps also changed viscosity/temperature/pressure by abnormal flow conditions in a flowing fluid.
According to the invention, it is thereby aimed at eliminating the need for external force by utilizing the kinetic (and perhaps the hydraulic, rheologic and thermal) forces which are already present in the pipeline/channel, the valve body being formed to respond to changes in said forces and close the valve by abnormal flow conditions arising.
In the immediate following are defined some applications of the fluid-activatable shut-off device according to the invention. The applications defined only represent non-limiting examples.
Accidents at sea-based oil/gas installations have demonstrated how important it is to have the enormous gas and oil reservoirs present in the transport line network under control. To a certain degree the current technology manages to is control pressure and transport of inflammable gases or liquids in the pipelines, but situations do occur, in which the valves will be of no use, as breaks in pipelines immediately upstream from a valve may release large or small reservoirs present in the pipeline downstream of the preceding valve. Prior to a possible pipe line break, the valves will be open to allow transport of fluid through the pipeline. By closing the valve it will be possible to restrict an oil or gas emission, fire or risk of an emergency situation escalating. This is an operation which will often take a certain amount of time and in some cases such an amount of time that it will be too late for contributing to significantly limiting the damage.
In an accident of fire or other emergency situation at sea-based installations it is important to have the liquid flow in the pipe systems carrying explosive/inflammable liquids, under control.
Today, the liquids in the transport pipe network in the North Sea are mainly controlled by means of so-called subsea valves which are positioned in central intersections in the pipeline network and/or by means of valves placed in the immediate vicinity of the platforms (at arrival or despatch from the platforms). This entails that large reservoirs of gas or liquids may be exposed to explosion, strong heat or other strain which may entail a break in the pipe system aboard the platform. The only alternative known is then to bleed off pressure, but this relieving of pressure may take from a few hours up to days. In processing plants situations corresponding to those described above might occur by a pipeline breaking at a location in which there is no barrier against reservoirs of gas or inflammable liquid.
Subsea valves currently used are based on the use of an actuator and on the latter being shipped out to the valve. Aboard the platform the so-called sea-line valves are connected to the operation shut-down system of the platform, and are closed automatically on alarm signals. In an emergency situation a subsea valve may, for example, not be closed quickly enough to prevent hydrocarbons from being supplied to the accident situation aboard the platform, because it takes too long time to operate the valve. Hydraulics pack and actuator must be shipped across and connected to the subsea valve for this to close. A sea-line valve is normally placed somewhat within the platform edge, which entails that parts of the transport pipeline may be exposed to fire, explosion, falling loads or similar without the possibility of being able to close the valve by breaks on the seaward side. Large reservoirs of hydrocarbons, oil and/or gas may then be released on the platform and contribute to the escalation of the accident.
In the above valve applications a shut-off valve according to the invention may be used with advantage, because it is arranged to respond to abnormal flow conditions occurring in situations of accidents such as major leaks, fire, explosions, in which the valve provides a quick but controlled shut-off.
The constructive features enabling a shut-off valve according to the invention to respond to an abnormal flow condition of the flowing fluid and thereby effecting forced closing, will be explained after the applications having been defined.
Another application in which the method according to the invention may be used with advantage, is in connection with ventilation of residential houses. Strong wind will cause a draught through open valves. By mounting the valve according to the invention in valve slots in windows and/or ordinary rectangular valves, the windward valve will close while the leeward valve opens and stays open. The dominant pressure inside the house will consequently be a negative pressure. This is will have a favourable effect as to the draught conditions in the house and the drying out of the wall material of the house. According to the invention, the valve will also have a favourable effect during the development of a possible fire. The fire will require oxygen in its initial phase. The oxygen is brought to the fire through openings such as doors, windows, valves and other leaks in the house. As the fire inhales, the valve will respond to increased air flow through the valve into the house by closing. By heat developing, the air expands and causes a flow of air and flue gases out of the house.
Another application in which the valve according to the invention may be used with advantage, is in connection with explosion dampers. An explosion erects pressure waves and will increase the air/gas flow through ventilation channels or other openings in the building construction, also where it is desirable to prevent the fire from spreading. According to the invention the valve will instantly resp

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