Measuring and testing – Dynamometers – Responsive to force
Reexamination Certificate
1999-05-11
2001-06-05
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to force
C073S168000
Reexamination Certificate
active
06240789
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to systems for monitoring and evaluating the forces on a stem or shaft. In particular, the present invention relates to systems for monitoring and evaluating the performance of actuated valve assemblies utilizing sensors mounted to the stems or shafts of the actuated valve assemblies.
BACKGROUND OF THE INVENTION
Actuated valve assemblies are in common use in a variety of industrial applications for the control of the rate of flow of fluid mediums such as steam, water, or other fluids. For purposes of this disclosure, an actuated valve assembly generally will consist of an actuator operatively connected to a valve stem for driving the valve stem, to move a valve element (for example, a gate or plug) within a valve chamber to open and close a valve port. In general, actuated valve assemblies fall within two basic categories which include rising stem valves where the valve stem is axially drawn into and out of the valve body through a gland seal, and rotary or quarter-turn valves where the valve stem is rotated approximately 90° to open or close the value by positioning a rotatable disk or ball having a flow opening formed therein. Rising stem valves further include “rising, non-rotating-stem valves” where the stem is moved axially without rotation, and “rising, rotating-stem valves” where the valve stem is raised and lowered through a rotary or screw type motion.
With respect to the actuation of such actuated valve assemblies, there are two general types of actuated valve assemblies, including: (i) motor-operated valves (“MOV's”) which utilize the electric or hydraulic torque motor to turn a worm on a worm gear, turning a rotating drive sleeve that drives either a power screw or a gearbox input shaft, for driving or powering a valve stem and connected valve element; and (ii) pressure-operated pneumatic or hydraulic actuators (mostly air operated valves or “AOV's”) in which a fluid pressure acting on a diaphragm or piston, and often opposed by a spring, provides a linear force for moving a rising stem valve or operating a drive which moves a rotary or quarter-turn valve.
Examples of MOV's include rising, non-rotating-stem valve assemblies and rising, rotating-stem valve assemblies and rotary or quarter-turn valve assemblies.
Examples of AOV's include rising, non-rotating-stem valve assemblies, and rotary or quarter-turn valve assemblies.
Currently, it is known to include monitoring systems or devices within the valve bodies or housings of conventional actuated valve assemblies for monitoring and evaluating axial and torsional forces being exerted upon the valve during the operation of the valve to provide an indication of the performance of the valve assembly.
There are monitoring instruments, both temporarily and permanently installable, primarily available for motor-operated valves such as Limitorque-driven units such as are found in nuclear power plants. Such devices are shown in patents typically classified in U.S. patent class 73, subclass 168, and an example of which are shown in U.S. Pat. Nos. 4,787,245 and 5,469,737. Additionally, U.S. Pat. No. 5,090,239 teaches a valve sensing instrument mounted within grooves or cutouts formed along the exterior sidewall of the valve stem, typically just above the packing of the valve assembly.
One problem that appears to still exist with known measured valve assemblies is, however, the exposure of the valve sensors or monitoring instruments to the environment of the valve where such sensors are subject to damage and environmental influence.
Accordingly, a need exists for an actuated valve assembly having a system for monitoring and evaluating the forces acting on the valve stem or shaft that can operate efficiently despite the environmental conditions within the valve assembly and which is easy and economical to manufacture and can easily be installed as a replacement for existing load.
SUMMARY OF THE INVENTION
Briefly described, the present invention is directed to a permanently instrumented, actuated valve assembly having a precisely calibrated gauge or monitoring instrument for the measurement of axial force and/or torque exerted on a shaft or stem of the actuated valve assembly, which monitoring instrument is internally received within the stem or shaft. Such monitoring instrument includes strain gauges or similar sensors as are known in the art for measuring various parameters including axial and torsional forces exerted upon a shaft/stem. The monitoring instrument or sensor further is calibrated for the measurement of one or both of the axial force or torsional forces exerted upon a load path component in an actuated valve assembly for the purpose of diagnostics or performance monitoring of the operation of the valve assembly.
The output signals generated by the monitoring instrument provide a feedback or control signal for a valve control system for controlling the operation of the valve assembly or to provide switching, shutoff or alarm functions.
It will be understood that the teachings of this invention are directed to shafts or stems for various types of actuated assemblies, but for purposes of illustration of preferred embodiments, the invention will be disclosed in relation to actuated valve assemblies. Since the terms “stem” and “shaft” may be considered to have specific meaning within the industry, the term “shaft” shall be used herein to refer to any load path component which is capable of being drilled and instrumented in the manner expressed in accordance with the present invention, unless that stem is preceded by modifying terms (for example, “actuator output shaft” or “valve input shaft”), in which case the “shaft” shall mean the specific species of shaft as so defined. It is fundamental to the present invention that the “shaft” which is instrumented in accordance with this invention is a normal load path component (or a replacement for a normal load path component) whose primary function is as an operative component of the actuated valve assembly, and its load sensing function is adjunct or secondary. That is, if no torque or thrust measurements were to be performed, the “shaft” would still be required for normal, proper operation of the valve element moving function of the valve element moving function of the actuated valve assembly.
Accordingly, in preferred embodiments of the present invention, an actuated valve assembly is provided with an internally mounted monitoring system. In accordance with the present invention, an internal bore is formed in a shaft of the actuated valve assembly. The internal bore generally is a longitudinally, preferably axially, drilled bore, and, in alternate embodiments, a transversely extending bore is formed in the shaft in conjunction with the axial bore. In preferred embodiments, the axially drilled bore is a blind center gun drilled axial bore. The axially extending bore preferably extends from a first or upper end of the shaft to an intermediate point along the length of the shaft. In embodiments of the invention including a transversely extending bore, the transverse bore, preferably, extends radially from the shaft periphery into the center of the shaft, and, most preferably, diametrically through the shaft. The transversely extending bore and the longitudinally drilled bore, preferably, intersect. A gauging or monitoring instrument such as a strain gauge or other, similar force sensor is received within one or both of the axial and transverse bores of the shaft and functions to monitor various operational parameters at the shaft including the amount of force or strain (resulting in either thrust or torque) being applied to the shaft. The instrumentation of the present invention preferably measures force exerted parallel to the centerline of the respective bore.
Prior to the insertion of the monitoring instrument(s) into the respective bore, the monitoring instrument(s) generally will have been calibrated, such as in a precision loading frame, for measurement of the desired parameters including measu
Morlan David E.
Smith Christopher P.
Crane Nuclear, Inc.
Noori Max
Womble Carlyle Sandbridge & Rice
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