Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1997-04-11
2003-05-27
Wachsman, Hal (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S182000, C702S183000, C073S168000
Reexamination Certificate
active
06571180
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of monitoring the operations of devices used in fluid systems. More specifically, the present invention applies to the field of monitoring steam trap operation to detect and predict abnormal operation of the steam trap.
2. Description of the Prior Art
Typical steam-containing systems require that condensed fluids and some uncondensed gases be discharged from the steam to prevent system malfunction. To this end, a variety of devices have been employed to automatically discharge undesirable gases and condensate from steam-containing systems. These devices, referred to generally as steam traps, can operate in a variety of ways to perform the basic task of venting undesired gases and condensates from the steam system.
Failure of the steam trap in a steam system can produce serious system damage and loss. It is customary, therefore, to periodically monitor the operation of the various steam traps in the system to detect malfunctions of such devices and to identify abnormal operation that can indicate impending failure of the device.
In larger systems, the number of steam traps can be large, and the steam traps themselves may be difficult to access as well as to locate. Manual monitoring of steam traps can thus be difficult simply from the standpoint of locating a specific steam trap and then obtaining access to the steam trap once it has been located.
One manually operated prior art system used to evaluate steam trap operation, described in U.S. Pat. No. 4,898,022 to Yumoto et al., employs a monitor that must be handheld against the steam trap body to monitor vibration and temperature associated with the steam trap. The detected vibrations are compared with a standard baseline data set of vibrations representative of the type of valve being evaluated. Variations of the monitored characteristics from those in the standard baseline are indicative of abnormal operation of the monitored valve. The system is dependent, in part, upon the interpretive and manipulative skills of the operator, requiring the exercise of judgment as to the validity of the readings as well as requiring intimate and correct contact of the monitor with the valve being evaluated. The monitoring of this prior art system is not designed to be continuous for a particular steam trap and requires the physical presence of an operator at each steam trap during the monitoring.
In addition to the reliance on operator presence and skill, the Yumoto et al. technique suffers from the fact that the specific steam trap being monitored, even when operating properly, will not necessarily adhere to a “standard” operating pattern in a particular environment. Moreover, as the environment of a steam trap changes, the operation of the steam trap may also change. Use of a representative “standard” baseline data set for a particular type or model without proper regard to the steam trap operating environment and the operating history of the steam trap subjects the comparison of current operation data with such a “standard” baseline data set to mistaken analyses.
Other prior art systems have also employed evaluation techniques in which the mechanism being monitored is tested against a baseline data set to provide information about the mechanism's status or condition, or information about the system itself. Such systems are described, for example, in U.S. Pat. No. 5,154,080 to Hill et al., U.S. Pat. No. 5,535,136 to Standifer, and U.S. Pat. No. 5,206,818 to Speranza.
The Hill et al. system compares reflected ultrasonic signals and/or accelerometer signals against baseline data to evaluate check valve operation. Signals picked up by transducers placed externally on the valve are relayed by cables to a personal computer that processes the data to provide information about the valve.
The Hill et al. system employs baselines that are the results of tests and analyses previously performed on the valve assembly being evaluated. In this regard, the system is an improvement over the Yuunoto et al. technique, which uses representative baseline data. Inoperability or signs of wear of the valve using the Hill et al. system are determined by viewing computer results or viewing the data directly. An alarm is generated by the CPU when the values of certain monitored parameters exceed preselected levels. The Hill et al. system is not self-contained and does not provide an alarm or signal at the monitored component that identifies the location and condition of the component. The transducers and processing components required to implement the system are complex and expensive. As with the Yumoto et al. system, the Hill et al. system is not well-suited for continuous automated monitoring of valve operation.
The Standifer patent describes a technique in which an ultrasonic sound detector is used to accumulate data from known test leaks. The data is then compared with similar data from an actual system to quantify the leakage in the actual system. While the technique compares baseline data with on-line data for system evaluation purposes, individual control components in the system are not continuously monitored, and the condition or status of an individual control component is not automatically signalled by a self-contained monitor associated with the control component. The baseline data also is not used as an indication of normal operation, but is rather employed to provide a basis for quantifying the extent of leakage from the component or system.
The Speranza patent describes a system in which a portable monitor is taken to a “fugitive emission” source to identify the source and quantify the emission. The monitor, which may be a single unit that includes a computer, is taken to the component to be monitored to perform a specific test. Results of the test may be stored in the computer, compared with other tests from the same component, and displayed on a computer screen. The Speranza system does not provide continuous monitoring and does not provide automatically generated signals associated with a specific monitored component to show the location of the component and to signal the status or condition of the component.
U.S. Pat. No. 4,945,343 to Rodriguez describes a system for continuously detecting malfunctioning of a steam trap and signalling malfunction of the trap. The system employs thermocouples at the input and output of a steam trap to sense malfunctioning of the steam trap. An alarm light is activated when a malfunction is detected. While the Rodriguez system offers the advantage of continuous monitoring, it provides an indication of component failure rather than an indication of abnormal operation of the monitored component. The alarm of the Rodriguez system is only activated when given preset conditions are met. No baseline comparisons are made in the system to evaluate evolving changes in the steam trap operation over its lifetime in the system.
The concept of “standard” operation as a reference in continuously monitored systems is complicated by the fact that in the operation of a typical system, it is necessary to periodically shut down the system for either maintenance or repair or to modify the system design or operation. The sequence of shutting down and then restarting the system will produce a time-based operating change in the operation of the steam traps within the system. Such changes in system operation, when monitored by a system that employs only on-line operating conditions as the basis for establishing a standard baseline data set, may indicate abnormal operation of a steam trap that is in fact operating properly.
SUMMARY OF THE INVENTION
The system of the present invention employs a self-contained, continuously operating monitor to detect abnormal operation of a monitored component and to permit the taking of remedial action before adverse system operations occur. The monitor of the present invention is preferably adapted to be employed with a single control component in a specific operating environment. The operating characte
Nethers Jan L.
Turner John M.
Browning & Bushman P.C.
Keystone International Holding Corp.
Torres Carlos A.
Wachsman Hal
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