Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
2003-03-05
2004-11-09
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S557000, C137S596170, C137S625250
Reexamination Certificate
active
06814104
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to control valves. In more specific aspects, the invention relates to: two-way three position type control valves which are particularly useful in remote locations where long signal lines are required, such as is the case with submerged christmas trees used with subsea oil production; and methods for assembling and using the control valves.
DESCRIPTION OF THE RELATED ART
Due to cost, most subsea oil and gas wells are produced to, and controlled from, an available offshore host facility. Rarely are new offshore structures constructed unless they are dedicated to several wells. Each well, in most cases, can be miles away from the facility. Control of the wells on such long offsets has been performed using several different methods: direct hydraulic, piloted hydraulic, direct electric, and multiplex electric, just to name a few. In the direct hydraulic method, valves, such as subsea tree valves, are controlled using individual pressurized conduits from the surface hydraulic power unit (“HPU”). This method can he used over a short offset but is prohibitive over a longer distance due to the slow response time to open or close a subsea valve. It is also typically limited to control only one or two wells due to the number of conduits required to control each tree. In the piloted hydraulic methodology, control valves are placed locally on the subsea tree and then pilot operated from the surface HPU as to direct a main hydraulic supply to the individual tree valve actuators. This method has a shorter response time due to the fact the hydraulic conduits from the host facility only need to actuate the smaller pilot valves and not the larger tree valves. Although operational distance has been increased using the “piloted hydraulic” method operation of more than a few wells, it is still prohibitive by the number and size of the pressure conduits required in the control link umbilical.
In the direct electric methodology, control valves are placed locally on the subsea tree which are then operated selectively using electrical power from the host facility. Individual conductor sets are dedicated to each valve. The subsea control valves can be operated selectively by a simple switch or Program Logic Controller (“PLC”). In addition the PLC can be mounted on and used for control of the HPU, thus increasing the system efficiency. The problem of extended distances are somewhat solved with this method. However, use of the direct electric methodology for more than a few wells is still prohibitive by the number and size of the electrical conductors required in the control link umbilical.
In the multiplex methodology, control valves are placed locally on the subsea tree then operated selectively using an electrical power and signal link from the host facility. The electrical power is sent to the valves, which are then selected for operation by a signal via modem. The number of pressured conduits and electrical conductors are greatly reduced in the control umbilical link to the subsea trees. Many aspects of distance and multi-well control are solved with this method. However, there still exists a need for a control valve system operated over long distances and placed locally, for example, on a subsea tree, operated selectively using electrical power from the host facility and which uses a minimal number of conduits and a minimal amount of power.
The electrically operated control valve may have several configurations depending upon the specific application. The following are a few examples of configurations that may be used. These include a “power on activated” methodology, a pulse activated methodology, and a failsafe methodology. In the power on activated methodology, the valve will remain open or activated as long as electrical power is applied to an electrical power actuator such as a solenoid coil. When the power is removed the valve will close or deactivate. In the pulse activated methodology, an electrical power pulse is applied to the solenoid and the valve remains in the activated position until the solenoid is pulsed again to close or deactivate. Constant electrical power is not required to maintain the valve in the activated position due to a mechanical or hydraulic detent which keeps the valve in the last position. In the fail-safe methodology, the valve is pulse activated and will remain open until the supply pressure drops below a specific value or the solenoid is pulsed again. This type of valve is typically used in conjunction with the pulse activated last position type valve as a fail safe measure. The failsafe portion of the valve is placed upstream of the pulse activating portion of the valve in order to cut off pressure to all functions and block the supply until reactivated. The fail-safe type valve is not usually configured with a coupler outlet interface because it only communicates via the supply line internal the valve module.
The electric power required to operate an electrically-powered actuator for a valve, such as a solenoid valve, is a function of the square of the force required and, therefore, any reduction in the force required to operate the valve will afford significant economics in both the construction and the operation of a solenoid actuated pilot valve. For example, if the force to operate a valve is cut in half, the power consumption is thereby reduced to one-fourth the original amount. A sizable savings by reducing the amount of power required to move a solenoid plunger, both from the standpoint of the cost of the initial installation, subsequent operating cost, and reduced heat build-up which provides for greater reliability. Recognized is the need for a control valve requiring minimal amount of electrical power to be actuated.
The state-of-the-art has found shear-type valves to be highly effective in controlling hydraulic functions such as functions on a sub sea tree. The typical shear-type valve will have at least two opposing shear seals communicating with each other through the gate. One will remain covering the supply port during actuation with the other shuttling from block to covering the function port. This allows the supply pressure to access the function upon actuation. On deactivation the supply pressure is again blocked with the function uncovered and venting inside the valve cavity and vent port. The inherent problem with this configuration is shear seal sliding friction which is induced by the hydraulic pressure. The shear seals must be relatively large in order to cover the supply port in both the actuated and inactivated position. The radial seal around the shear seal encircle a large area which is acted upon by the hydraulic pressure. The net result is high force generated on the shear seal face (multiplied by two) that can require high solenoid force to slide from one position to the other. Several solutions have been derived in the past to combat the result of high seal friction. One solution was to add secondary hydraulic pilots to each valve that move the gate from one position to the other. Another solution was to make the porting in the shear seals very small, so the overall net force on the face is manageable. Yet another solution was to incorporate a very large electrical coil to move the gate. And yet another solution, was a combination of some or all of the above. All of the noted solutions have their own inherent problems which for the most part increase the size and complexity of the whole subsea system, reduce or restrict the flow to the subsea function or both. Thus, there is a need for a compact, less complex, control valve requiring a minimal amount of power to be actuated.
A typical subsea control valve does not contain or have the means to connect directly to the function coupler mounted on a base structure, such as those on a sub sea tree. Typically, this entails using a separate male and female coupler. The associated female coupler is an independent component that is either mounted on the bottom of the removable module or assembled on to the valve using a treaded connec
Hunter Shawn
Michalsky Gerald A.
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