Two out of three voting solenoid arrangement

Details Two out of three voting solenoid arrangement Two out of three voting solenoid arrangement

2001-06-25

2002-08-20

Chambers, A. Michael (Department: 3753)

Fluid handling

Processes

C137S557000, C251S026000, C251S030010, C060S403000

Reexamination Certificate

active

06435202

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to solenoid valves, and more particularly to an arrangement of solenoid valves in instrumentation and process control systems of a plant.
2. Background Information
Modern process or manufacturing plants contain innumerable operating components. These components are tied together to form systems controlled by instrumentation and control systems containing sensors and controllers. The instrumentation and control systems on such plants not only serve to control the functions of the various components in order to achieve the desired process conditions, but they also provide the facility to safely modify or discontinue the operation of all or a portion of the plant's systems in order to avoid an unsafe situation or condition.
Safety systems or configurations require routine testing in order to verify that they continue to properly perform the functions for which they were intended. From an operational and economic point of view, they also should not modify or discontinue the operation of the plant system unnecessarily. One of the means by which such safety systems function is by the securing or diverting of the supply of a certain process fluid or the supply of motive power to a plant system or component of a plant system.
One of the means by which these safety functions may be accomplished is through the use of solenoid operated valves. In operation, the solenoid valves of such systems serve to isolate and/or vent off the fluid or pneumatic source from the system when the solenoid valve changes state or position (e.g. when the valve is de-energized by switches or process monitoring sensors coupled thereto). The plant system and any system controlled thereby is then placed in a configuration designated for safety.
In many cases, the operation of individual solenoid valves may not be tested without actually tripping the system and undesirably modifying or discontinuing the operation of the plant system. Moreover, various configurations available for actuating safety shutoff valves generally require a trade-off between competing characteristics of safety and spurious trip rate.
For example, a “1 out of 2” voting solenoid valve arrangement generates a process modification (i.e. shutdown) when at least one of the two solenoids changes state. Such a configuration provides relatively high safety, with an associated relatively high spurious trip rate (i.e., a single faulty valve or sensor may generate a false trip).
A “2 out of 2” voting solenoid valve arrangement requires actuation of two solenoid valves in order to trigger a modification of the plant system. This configuration has a relatively low spurious trip rate, since both solenoids must fail or otherwise change state to generate a spurious trip. However, the solenoid valves of this arrangement must be tested frequently to insure safety, since failure of only a single solenoid valve may effectively prevent the system from shutting down, etc.
Quad voting solenoids provide a balance of safety and reliability, however the quad configuration utilizes four solenoids in a relatively complex arrangement that tends to be difficult to install, test, and maintain.
Thus, there exists a need for a voting solenoid configuration which combines the features of relatively high safety with relatively low spurious trip rate and does not require the plant system to be shut down during testing.
SUMMARY OF THE INVENTION
According to an embodiment of this invention, a binary voting solenoid arrangement adapted to selectively couple a fluid supply with a fluid receiver, the voting solenoid arrangement including first, second and third solenoid valves each having a plurality of ports. A plurality of inlet and outlet pathways each extend from a respective port of one of the solenoid valves to a port of another of the solenoid valves, so that the solenoid valves are disposed in fluid communication with one another. The arrangement includes a by-pass valve having first and second open and closed positions, the by-pass valve being configured to selectively couple the fluid supply with the fluid receiver while bypassing the first, second and third solenoid valves. The by-pass valve includes a five port, four way by-pass valve, with a single port of the bypass valve being the fluid receiver. Each of said first, second, and third solenoid valves and said by-pass valve are alternatively actuatable between first and second open and closed positions, so that actuation of at least any two of the first, second and third solenoid valves alternately couples and de-couples the fluid supply with said fluid receiver.
Another aspect of the present invention includes a method for selectively coupling a fluid supply with a fluid receiver, the method including providing first, second and third solenoid valves each having a plurality of ports, and each being alternately actuatable between open and closed positions; and providing a plurality of inlet and outlet pathways each extending from a respective port of one of the solenoid valves to a port of another of the solenoid valves, so that the solenoid valves are disposed in fluid communication with one another, with the first solenoid valve being in fluid communication with the second solenoid valve and the second solenoid valve being in fluid communication with the third solenoid valve. The method also includes providing a five port, four way by-pass valve, and coupling one port of the by-pass valve to the fluid supply and another port of the bypass valve to the fluid receiver so that actuation of the by-pass valve selectively couples the fluid source with the fluid receiver while bypassing the first, second and third solenoid valves, wherein actuation of any two of the first, second and third solenoid valves alternately couples and de-couples the fluid supply with the fluid receiver.
According to still another aspect, this invention includes a binary voting solenoid arrangement configured to selectively couple a fluid supply with a fluid receiver. The voting solenoid arrangement includes first, second and third solenoid valves each including at least two common ports and three other ports, in which the two common ports are selectively coupled in fluid communication with a distinct two of three other ports. The arrangement also includes a manually operated by-pass valve having first and second open and closed positions, the by-pass valve being configured to selectively couple the fluid source with the fluid receiver while bypassing the first, second and third solenoid valves, the by-pass valve including a five port, four way by-pass valve. A single port of the bypass valve is the fluid receiver, and a single port of the by-pass valve is couplable in fluid communication with the fluid supply. Each of the first and second solenoid valves are coupled with the by-pass valve so that each of the first and second solenoid valves are in fluid communication with the fluid supply when the by-pass valve is in the first position. The second solenoid valve is coupled in fluid communication with the third solenoid valve; and the third solenoid valve is coupled with the by-pass valve so that the third solenoid valve is in fluid communication with the fluid receiver when the by-pass valve is in the first position. Each of the first, second and third solenoid valves are alternatively actuatable between first and second open and closed positions, wherein actuation of at least any two of the first, second and third solenoid valves alternately couples and de-couples the fluid supply with the fluid receiver.
The above and other features and advantages of this invention will be more readily apparent from a reading of the following detailed description of various aspects of the invention taken in conjunction with the accompanying drawings.


REFERENCES:
patent: 4316486 (1982-02-01), Tandrup et al.
patent: 4319609 (1982-03-01), Debrus
patent: 4637587 (1987-01-01), Kuhnlein
patent: 5142483 (1992-08-01), Basham et al.
patent: 5621164 (1997-04-01), Woodbury et al.
patent:

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