Fluid handling – Processes – Cleaning – repairing – or assembling
Reexamination Certificate
1998-09-17
2001-06-05
Walton, George L. (Department: 3753)
Fluid handling
Processes
Cleaning, repairing, or assembling
C137S015070, C137S240000, C137S242000, C137S625460, C251S185000, C251S314000, C251S315130, C251S368000
Reexamination Certificate
active
06240946
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to switch valves of the type commonly used to divert incoming fluid to a selective one of a plurality of fluid outlets from the valve. More particularly, this invention relates to a highly reliable switch valve suitable for severe service applications.
BACKGROUND OF THE INVENTION
Switch valves have been used for decades in various industrial applications to divert an upstream fluid to one of a plurality of downstream lines extending from the switch valve. Conventional switch valves have generally utilized one of two basic designs: (1) a plug valve element design, or (2) a ball valve element with bellows design.
Switch valves utilizing plug element have not proven to be highly reliable, particularly when the valves are used in severe service automated applications. When the plug element is lifted and rotated to operate the valve, particulate matter frequently becomes trapped between the plug element and the seat, which may damage the seat and thus increase the likelihood of leakage. A typical ported plug valve cannot handle the full flow of the pipe to which it is connected, and is difficult to automate. Accordingly, ball element switch valves are generally preferred over plug element switch valves when used in severe service automated applications. A common severe service application for a switch valve is a coker operation, wherein hydrocarbon is diverted by the switch valve from an upstream source to one of a plurality of downstream lines. Those skilled in the art appreciate that this type of service for a valve requires high reliability since coke formed from the hydrocarbon tends to foul moveable components within the valve. Other types of severe service applications will be apparent to those skilled in the art.
A significant problem with prior art switch valves of the ball variety with bellows relates to the complexity of the valve. Such valves commonly have as many as sixteen internal parts, including a ball assembly and a seat, sleeve, bellows, insert gasket, and insert associated with each of the plurality of outlets. Each bellows seals between the valve body and a respective seat, and biases the seat for sealing engagement with the ball. The large number of parts increases the likelihood of valve failure due to a failure of one or more of these parts. This valve design utilizes a separate bellows loading a seat adjacent to each of the outlets to balance and centralize the ball in the center of the valve body. The bellows assembly conventionally includes a weld between the bellows and the seat, and this assembly depends upon a balanced purge to prevent the bellows from being damaged by system over pressure. If the valve loses purge pressure, the bellows may be distorted and the valve permanently damaged.
Other problems with prior art switch valves of the ball variety relate to the high costs to maintain the valve. To disassemble a conventional switch valve with a ball and multiple bellows, the weld from the sleeve to the bellows must be cut and a new sleeve welded in place. Since various severe service applications commonly use chrome-moly materials for these components, this welding operation is difficult and requires stress relieving to minimize the likelihood of cracking. Moreover, the use of an extremely thin material for the bellows assembly is required, and care must be taken in selecting a material with high tensile and yield properties. The bellows assembly materials are thus expensive, and the thin materials could limit valve testing and full service rating in actual service.
Still another problem with conventional switch valves utilizing a ball element and multiple bellows is that the bellows design allows for the accumulation of material passing through the valve to build up and adversely affect the valve operation. In view of the high number of areas where buildup may occur, a large number of purge ports are provided in conventional ball-type switch valves. A good deal of time and expense is thus required to minimize buildup of solid matter in these areas.
When the ball port of a prior art switch valve moves during rotation of the stem to divert fluid from one outlet to another outlet, the cavity around the ball is exposed to the process stream. In addition, the cavity purge exhausts with the full bore of the ball as the ball rotates, thereby allowing unrestricted flow and high consumption of the steam purge. This loss of steam is costly and the ingress of process material could lead to valve lockup, both of which are significant problems for this type of design.
Those skilled in the art recognize that switch valves having at least two and often three outlet ports present unique problems with respect to their design and operation compared to conventional shut-off or control valves having a single inlet port and a single outlet port. The disadvantages of the prior art are overcome by the present invention, and an improved switch valve utilizing a ball element is hereinafter disclosed. The switch valve of this invention is highly reliable, and is particularly well suited for severe service applications.
SUMMARY OF THE INVENTION
An improved switch valve having a ball member is suitable for severe service applications. In a preferred embodiment, the ball member directs incoming fluid to a selected one of a plurality of outlets, with the ball member being rotatable within the valve body by a valve stem for controlling fluid communication between the body inlet port and the selected one of the plurality of body outlet ports. A suitable actuator is recommended for powering rotation of the valve stem. A valve body defines a valve seat thereon integral with the valve body and spaced circumferentially about each of the plurality of outlet ports. A Belleville spring or other biasing member provided adjacent the body inlet port exerts a biasing force on the ball member for sealing engagement with the valve seat.
It is an object of the present invention to provide an improved switch valve which benefits by a design which is simplistic and has few moving parts. The valve employs a seat which is integral with the valve body to provide a rigid seating surface with few if any behind-the-seat cavities. A Belleville spring or other biasing member biases the ball for continuous sealing engagement with the seating surface, with the biasing member being positioned circumferentially about the fluid inlet port of the valve.
It is a feature of the present invention that the ball valve may utilize outlet ports which each having a central axis angled at from 125° to 155° relative to a central axis of the body inlet port, thereby improving flow capacity compared to conventional ball valves which utilize a 90° angle between the inlet port and each of the outlet ports. This design improves the performance of the valve by reducing the pressure drop through the valve under flowing conditions. By providing a single biasing member rather than a plurality of biasing members each associated with a respective outlet port, the biasing member material may be increased in thickness, thereby allowing the biasing member to be manufactured from more conventional rather than expensive materials. In one embodiment, the switch valve is provided with a ball having a diameter only twice the diameter of each of three outlet ports from the valve body. By utilizing a ball-type switch valve which does not include a bellows, the reliability of the valve is increased. The switch valve of the present invention also reduces the number of cavities within the valve where debris may accumulate compared to a conventional switch valve with bellows, thereby reducing the purging operations required,to allow reliable valve operation. The valve seat formed on the valve body may exert a cleaning force against the ball as it rotates within the valve body to remove debris from the surface of the ball. By providing an integral seat on the valve body, the possibility of damaging the valve during testing or from full service rating in actual service is substantially eliminat
Browning Bushman
Tyco Flow Control, Inc.
Walton George L.
LandOfFree
Switch valve does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Switch valve, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Switch valve will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2469873