Abstract:
An apparatus and method for monitoring valve operation. In one embodiment, an apparatus for monitoring valve operation includes a first acoustic sensor and a monitoring system. The first acoustic sensor is to couple to a valve to detect vibration of the valve. The monitoring system is communicatively coupled to the first acoustic sensor. The monitoring system is configured to receive a signal generated by the first acoustic sensor. The signal is representative of vibration of the valve. The monitoring system is also configured to identify leakage in the valve based on the signal.

Description:
BACKGROUND 
       [0001]    Blowout preventers (BOPs) are used in hydrocarbon drilling and production operations as a safety device that closes, isolates, and seals the wellbore. Blowout preventers are essentially large valves connected to the wellhead and comprise closure members that seal and close the well to prevent the release of high-pressure gas or liquids from the well. One type of blowout preventer used extensively in both low and high-pressure applications is a ram-type blowout preventer. A ram-type blowout preventer uses two opposed closure members, or rams, disposed within a specially designed housing, or body. The blowout preventer body has a bore aligned with the wellbore. Opposed cavities intersect the bore and support the rams as they move into and out of the bore. A bonnet is connected to the body on the outer end of each cavity and supports an operator system that provides the force required to move the rams into and out of the bore. 
         [0002]    Ram-type blowout preventers are often operated using pressurized hydraulic fluid to control the position of the closure members relative to the bore. The flow of hydraulic fluid to the rams is controlled via one or more control pods of the blowout preventer control system. The control pod provides an electrical interface for operation of the blowout preventer from a drilling platform or other surface location. The control pod may be modularized to facilitate pod testing and service by allowing individual replacement and/or testing of each module. The control pod generally includes an electronics package (MUX module) and a hydraulics module (MOD module). The MUX module provides electrical communication with surface systems and electrically activated solenoid valves. The solenoid valves control flow of hydraulic fluid to hydraulic valves of the MOD module. 
       SUMMARY 
       [0003]    An apparatus and method for monitoring valve operation are disclosed herein. In one embodiment, an apparatus for monitoring valve operation includes a first acoustic sensor and a monitoring system. The first acoustic sensor is to couple to a valve to detect vibration of the valve. The monitoring system is communicatively coupled to the first acoustic sensor. The monitoring system is configured to receive a signal generated by the first acoustic sensor. The signal is representative of vibration of the valve and the components therein. The monitoring system is also configured to identify leakage in the valve based on the signal. 
         [0004]    In another embodiment, a well control system includes a blowout preventer, a hydraulics module, and a monitoring system. The hydraulics module includes a first valve and a first acoustic sensor. The first valve is configured to provide hydraulic pressure to the blow out preventer. The first acoustic sensor is coupled to the first valve to detect vibration of the first valve. The monitoring system is communicatively coupled to the first acoustic sensor. The monitoring system is configured to receive a first signal generated by the first acoustic sensor. The first signal is representative of vibration of the first valve. The monitoring system is also configured to identify a condition of the first valve based on the signal. 
         [0005]    In a further embodiment, a fluid control assembly includes a first valve, a second valve, a first acoustic sensor, a second acoustic sensor, a third acoustic sensor, and a monitoring system. The first valve and the second valve are to control flow of fluid. The first acoustic sensor is coupled to the first valve to detect vibration of the first valve. The second acoustic sensor is coupled to the second valve to detect vibration of the second valve. The third acoustic sensor is to detect ambient vibration. The monitoring system is communicatively coupled to the first, second, and third acoustic sensors. The monitoring system is configured to receive signals generated by the first and second acoustic sensors that are representative of vibration of the first and second valves, and to receive signals generated by the third acoustic sensor that are representative of ambient vibration. The monitoring system is also configured to identify a condition of each of the first and second valves based on the signals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    For a detailed description of exemplary embodiments of the invention, reference will now be made to the accompanying drawings in which: 
           [0007]      FIG. 1  shows a drilling system including a blowout preventer in accordance with various embodiments; 
           [0008]      FIG. 2  shows a block diagram of a valve monitoring system in accordance with various embodiments; 
           [0009]      FIG. 3  shows a cross-section of a valve with associated acoustic sensor in accordance with various embodiments; 
           [0010]      FIG. 4  shows an example of an acoustic energy plot generated by a leaking valve in accordance with various embodiments; 
           [0011]      FIG. 5  shows a block diagram of a valve monitoring system in accordance with various embodiments; and 
           [0012]      FIG. 6  shows a block diagram of a valve monitoring system in accordance with various embodiments; 
           [0013]      FIG. 7  shows a block diagram of an acoustic sensor assembly that includes a plurality of acoustic sensing channels in accordance with various embodiments; 
           [0014]      FIG. 8  shows a diagram of an acoustic sensor assembly that includes a plurality of acoustic sensing channels in accordance with various embodiments; 
           [0015]      FIG. 9  shows a block diagram of a valve monitoring system in accordance with various embodiments; and 
           [0016]      FIG. 10  shows a block diagram of a valve monitor in accordance with various embodiments. 
       
    
    
     NOTATION AND NOMENCLATURE 
       [0017]    Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections. The recitation “based on” is intended to mean “based at least in part on.” Therefore, if X is based on Y, X may be based on Y and any number of other factors. 
       DETAILED DESCRIPTION 
       [0018]    The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment. 
         [0019]    Like all mechanical components, the hydraulic valves used to actuate a blowout preventer (BOP) are subject to wear. Unfortunately, using conventional methods the condition of a valve may be difficult to determine until the valve exhibits symptoms clearly indicative of malfunction. Valve malfunction may result in the BOP, or a substantial portion thereof, being removed from service to facilitate valve replacement. Removing a BOP from service can be costly and time consuming. 
         [0020]    Embodiments of the present disclosure include a monitoring system that characterizes valve operation. The monitoring system includes acoustic sensors coupled to the valves. The acoustic sensors acquire signals that are indicative of the state and condition of the valve. The monitoring system processes the signals to characterize the valve. Processing and analysis of the acoustic signals emitted by the valve allow the monitoring system to identify leaks in the valve that may undetectable using conventional methods and to identify degradation of valve components. As a result, embodiments can reduce the expense of BOP maintenance by allowing for replacement or repair of valves via routine maintenance operations rather than unscheduled removal of the BOP stack from service. 
         [0021]      FIG. 1  shows a drilling system  150  in accordance with various embodiments. The drilling system  150  includes a drilling platform and drilling rig  152 , a riser  154 , and a BOP  156 . The BOP  156  is coupled to a wellhead  158 . The riser  154  connects the BOP  156  to the drilling platform  152 . One or more control pods  100  are coupled to the BOP  156  for actuating BOP hydraulics in response to control signals provided from the surface. The control pods  100  include valves that control the flow of hydraulic fluid to the BOP  156 . Failure of one of the valves can cause the BOP  156  to be removed from service for unscheduled replacement of the valve. 
         [0022]    The drilling system  150  includes a valve monitoring system that characterizes the hydraulic valves of the BOP control pod  100  based on vibration generated by the valves. While  FIG. 1  illustrates a marine drilling system  150 , and embodiments of the present disclosure may be described with respect to the marine drilling system  150 , embodiments are also applicable to monitoring valves in a land or surface drilling environment, and to various other applications in which monitoring of valve condition may be beneficial. 
         [0023]      FIG. 2  shows a block diagram of a valve monitoring system  200  suitable for use in the drilling system  150 . The valve monitoring system  200  includes a valve  202 , an acoustic sensor  204 , and a valve monitor  206 . The valve  202  is a valve of the BOP control pod  100 . The valve  202  may be any type of valve suitable for controlling the flow of hydraulic fluid to the BOP  156 . For example, the hydraulic valve  202  may be a ball valve, a needle valve, a gate valve, a butterfly valve, a shuttle valve, or any other type of valve suitable for controlling fluid flow. 
         [0024]    The acoustic sensor  204  is coupled to the valve  202 . In some embodiments, the acoustic sensor  204  may be attached to an exterior surface of the valve  202 . For example, the acoustic sensor  204  may be mechanically affixed to an exterior surface of a housing of the valve  202  by a bolt, an adhesive, a magnet, or other suitable attachment method. In some embodiments, the acoustic sensor  204  may be disposed within the valve  202 . For example, the acoustic sensor  204  may be built into the housing of the valve  202 . 
         [0025]    Embodiments of the valve  202  may be constructed of various materials. For example, the sealing components and surfaces of the valve  202  may be metal, plastic, and/or elastomeric.  FIG. 3  shows a cross-section of an example of a valve  202  with associated acoustic sensor  204  in accordance with various embodiments. The valve  202  includes a piston  302 , an inlet/outlet seal plate  306 , a number of elastomeric seals  304 , a blind seal plate  310 , seal rings  314 , a valve body  308 , end caps  312 , springs, and various other components. As explained above, the acoustic sensor  204  may be attached to an outer surface of the valve body  308  or internally incorporated in the valve body  308  or other component of the valve  202 . Both configurations are shown in  FIG. 3 . The valve monitoring system  200  can identify leaks in metal-to-metal seals (e.g., between inlet/outlet seal plate  306  and seal ring  314 ), elastomeric seals, and other seals of the valve  202 . 
         [0026]    The acoustic sensor  202  may be any of a variety of types of transducers that convert vibration into electrical signals. The acoustic sensor  202  may include an accelerometer (e.g., a micro-electro-mechanical system (MEMS) accelerometer), a piezoelectric element, optical fibers, or other transduction element suitable for detecting vibration of the valve  202 . 
         [0027]    Returning now to  FIG. 2 , signals generated by the acoustic sensor  204  (e.g., electrical signals representative of the vibration of the valve  202  detected by the acoustic sensor  204 ) are provided to the valve monitor  206 . The valve monitor  206  processes the signals received from the acoustic sensor  204  to characterize operation of the acoustic sensor  204 . The valve monitor  206  can identify a variety of operational conditions of the valve  202  based on the signals received from the acoustic sensor  204 . In some embodiments, the valve monitor  206  can identify when the valve  202  is opening or closing based on the acoustic signals generated by the valve  202  while opening or closing. As a result, the valve monitor  206  can measure the time required to open the valve  202  and the time required to close the valve  202 . An increase in the time needed to open or close the valve  202  may indicate degradation in operation of the valve  202 . Significant change in the operation time of the valve  202  may, for example, trigger maintenance operations to replace the valve  202  prior to failure. Similarly, based on the acoustic signals generated by the valve  202  and detected by the acoustic sensor  204 , the valve monitor  206  may be able to detect whether the valve  202  is open or closed. Accordingly, the valve monitor  206  can indicate that valve  202  is in an incorrect state which may trigger action to correct the state of the valve  202 . 
         [0028]    Using the acoustic signals generated by the valve  202  while opening or closing, the valve monitor  206  can identify static friction (stiction) in valve  202 . Generally, stiction is friction between stationary components of the valve  202  that inhibits relative motion between the components when the valve  202  is actuated. For example, stiction between sealing surfaces may inhibit opening or closing of the valve  202 . The valve monitor  206  may identify stiction in the valve  202  as delay from a point in time that valve actuation is initiated until the internal components of the valve  202  move. The valve monitor  206  can measure such actuation delay by monitoring operation of a solenoid valve of the pod  100 , or other control signal (via a valve control system) indicating that the valve  202  is being actuated, and monitoring the acoustic signature of the valve  202 . If the time delay between initiation of valve actuation and initial movement of the valve (as identified via the acoustic signals generated by movement within the valve  202 ) changes over time (most likely to increase) the change in time delay may be indicative of stiction in the valve  202 . The valve monitor  206  may report detected stiction to an authority responsible for operation of the valve  202  to allow scheduling of maintenance. 
         [0029]    The valve monitor  206  may also detect leaks in the valve  202  based on the acoustic signals generated by the valve  202  and detected by the acoustic sensor  204 . In some embodiments of the valve  202 , a leak in the valve  202  may be indicated by acoustic signals generated at a particular frequency.  FIG. 4  shows a plot of acoustic signal energy generated by the valve  202 . To produce the plot of  FIG. 4 , the valve monitor  206  applies a frequency transform (e.g., a fast Fourier transform) to the signals received from the acoustic sensor  204  to generate a frequency domain representation of the signals. The increase in energy at point  402  indicates that the valve  202  is leaking. Accordingly, the valve monitor  206  may identify a particular frequency band that is indicative of a leak in the valve, and identify the valve as leaking if acoustic energy in the particular frequency band rises above a predetermined level or increased by a predetermined amount (e.g., while the valve  202  is closed). 
         [0030]    Some embodiments of the valve monitor  206  may acquire a baseline model of steady-state acoustic data generated by the valve  202  and compare the baseline model to acoustic data generated by the valve  202 . Changes in the steady-state acoustic energy generated by the valve  202  may indicate that a leak or other undesirable condition has arisen in the valve  202 . If the valve monitor  206  determines, based on the signals received from the acoustic sensor  204 , that the valve  202  has degraded, developed a leak, or otherwise undergone a change in operational performance, then the valve monitor  206  may provide an alert indicative of the change in condition of the valve  202 . In response to the alert, maintenance or replacement of the valve  202  may be scheduled. 
         [0031]      FIG. 5  shows a block diagram of a valve monitoring system  500  suitable for use in the drilling system  150 . The valve monitoring system  500  is similar to the system  200  described above, but includes an additional acoustic sensor  508 . As in the system  200 , the acoustic sensor  204  is coupled to the valve  202  for detection of acoustic signals generated by the valve  202 . Unlike, the acoustic sensor  204 , the acoustic sensor  508  is not coupled to the valve  202  for detection of acoustic signals generated by the valve  202 . Rather, the acoustic sensor  508  is positioned to detect acoustic signals present in the environment in which the valve  202  operates. In the BOP  156  and the riser  154  a variety of noise sources generate acoustic signals. For example, motion of a drill string passing through the BOP  156  and the riser  154  generates acoustic noise. Similarly, actuation of solenoids, valves and other devices in the BOP  156  generate acoustic noise. The acoustic sensor  508  detects the ambient acoustical noise proximate the hydraulic valve  202 , generates electrical signals representative of the ambient acoustical noise, and provides the signals to the valve monitor  506 . The valve monitor  506  applies the ambient noise signal received from the acoustic sensor  508  to filter ambient noise from the valve acoustic signals received from the acoustic sensor  204 . For example, the valve monitor  506  may subtract the ambient noise signal, or a portion thereof, from the valve acoustic signals. 
         [0032]    Some embodiments of the valve monitor  506  may filter ambient noise from the acoustic signals received from the acoustic sensor  204  by applying a low cut filter to the valve acoustic signals, in lieu of, or in addition to use of ambient noise signals as described above. For example, if ambient noise is generally at frequencies below 100 Hz, then the valve monitor  506  may apply a low-cut filter having a 100 Hz corner frequency (or other suitable corner frequency) to acoustic signals received from the acoustic sensor  204  to remove the ambient acoustic noise. 
         [0033]    In some embodiments, the valve monitor  506  may reduce the level of ambient noise in the valve acoustic signals using the acoustic signals provided by a plurality of the acoustic sensors  204 . For example, the valve monitor  506  may sum the acoustic signals provided by a plurality of the acoustic sensors  204  over a given time interval to generate a composite acoustic signal in which ambient noise is reinforced and valve specific acoustic signal is attenuated. Subtraction of the composite acoustic signal from the acoustic signal provided by each of the plurality of the acoustic sensors  204  may attenuate the ambient noise present in each of the resultant valve acoustic signals. 
         [0034]    In some embodiments, at least a portion of the signal processing or preconditioning applied to the acoustic sensor output signals, and associated with the valve monitor  506  in some embodiments, may be performed proximate the acoustic sensor  204 .  FIG. 6  shows a block diagram of a valve monitoring system  600  that provides preprocessing proximate the acoustic sensor  204  in accordance with various embodiments. In the valve monitoring system  600 , the acoustic sensor  204  is disposed proximate the valve  202  as explained with regard to the system  200 , and the valve monitor  608  is disposed at the surface (e.g., on the rig  152 ). The signal preprocessing circuitry  602  and telemetry transceiver  604  are disposed proximate the acoustic sensor  204 , and the telemetry transceiver  606  is disposed proximate the valve monitor  608 . The telemetry transceivers  604  and  606  may employ any of a variety of data communication protocols. For example, the telemetry transceivers  604  and  606  may employ Ethernet or Controller Area Network protocols to communicate via cabling that connects the transceivers  604  and  606 . 
         [0035]    The signal preprocessing circuitry  602  receives the signals generated by the acoustic sensor  204  and can apply various preprocessing operations. For example, the signal preprocessing circuitry  602  may include an analog-to-digital converter to digitize the signals, an anti-alias filter, a low-cut filter to reduce ambient noise content, etc. The various operations performed by the signal preprocessing circuitry  602  may be implemented using analog or digital techniques and components in different embodiments. 
         [0036]    The preprocessed signal generated by the signal preprocessing circuitry  602  is provided to the telemetry transceiver  604 . The telemetry transceiver  604  transmits the preprocessed signal to the telemetry transceiver  606 . The telemetry transceiver  606  receives the signal transmitted by the telemetry transceiver  604  and provides the received signal to the valve monitor  608  for further processing and use in characterization of the valve  202  as described herein. 
         [0037]    The preprocessing circuitry  602  may also be configurable via information received from the valve monitor  608  via the telemetry transceiver  604 . In some embodiments, the signal preprocessing circuitry  602  may include field programmable components, such as a field programmable gate array or a digital signal processor, which can be configured by the valve monitor  608  to change the functionality provided by the signal preprocessing circuitry  602 . For example, the valve monitor  608  may change the corner frequency of a filter applied by the signal processing circuitry  602 , or other operational parameters, using a command transmitted via the telemetry transceiver  604 . 
         [0038]    In some embodiments of the control pod  100 , a number of valves  202  may be located in close proximity to one another. To facilitate monitoring of a number of proximate valves  202 , some embodiments of the valve monitoring system disclosed herein may group a number of acoustic sensors  204  and associated signal preprocessing circuits  602  in an assembly that communicates with the valve monitor  608  via a single transceiver  604  that is coupled to all of the signal preprocessing circuits  602 .  FIG. 7  shows a block diagram for a system  700  that includes an acoustic sensor assembly  702 . The acoustic sensor assembly  702  includes a plurality of acoustic sensing channels  704  and a telemetry transceiver  604 . Each acoustic sensing channel  704  includes an acoustic sensor  204  and associated signal preprocessing circuit  602 . The telemetry transceiver  604  manages communication with the valve monitor  608  for all of the acoustic sensing channels included in the assembly  702 . Accordingly, acoustic signal outputs of each of the signal preprocessing circuits  602  are provided to the telemetry transceiver  604  for transmission to the valve monitor  608 . Each of the acoustic sensing channels  704  may be addressable to allow the valve monitor  608  to individually communicate with and control each of the channels  704 . 
         [0039]    In some embodiments of the acoustic sensor assembly  702 , the preprocessing circuitry  602  for multiple acoustic sensing channels  704  may be aggregated in a single device, or a single instance of the preprocessing circuitry  602  may perform preprocessing functions for a plurality of acoustic sensors  204 . Though the acoustic sensor assembly  702  is illustrated as including four acoustic sensing channels  704  as a matter of convenience, in practice the acoustic sensor assembly  702  may include any number of acoustic sensing channels  704   
         [0040]      FIG. 8  shows another diagram of the acoustic sensor assembly  702 . In  FIG. 8 , the acoustic sensors  204 , signal preprocessing circuitry  602 , and telemetry transceiver  804  are attached to a common substrate  802 . The substrate  802  may be a metal plate or housing, or may be a platform of another suitable material. The acoustic sensors  204  are arranged on the substrate  802  such that each of the sensors  204  corresponds to, and is brought into contact with, one of the valves  202  of the control pod  100  when the acoustic sensor assembly is attached to the control pod  100 . Accordingly, by attaching the substrate  802  to the control pod  100 , a plurality of valves  202  may be monitored. In some embodiments, a material that provides acoustic insulation may be disposed between the substrate  802  and each acoustic sensor  204  to reduce cross talk between the sensors  204 . 
         [0041]      FIG. 9  shows a block diagram of a valve monitoring system  900 . The valve monitoring system  900  includes a plurality of acoustic sensor assemblies  702 . The acoustic sensor assemblies  702  are arranged, in conjunction with the telemetry transceiver  906  coupled to the valve monitor  608 , to form a ring topology. The ring topology advantageously provides redundant communication paths to each of the sensor assemblies  702 , thereby enhancing the reliability of communication with sensor assemblies  702  in the relatively harsh environments to which the sensors assemblies are subject when used to monitor the valves  202 . 
         [0042]      FIG. 10  shows a block diagram of a valve monitor  1000  in accordance with various embodiments. The valve monitors  206 ,  506 , and  608  disclosed herein may be implemented as the valve monitor  1000 . The valve monitor  1000  includes a processor  1002  and storage  1004 . The valve monitor  1000  may also include various other components that have been omitted from  FIG. 10  in the interest of clarity. For example, embodiments of the valve monitor  1000  may include a display device, such as a computer monitor, user input devices, network adapters, etc. Some embodiments of the valve monitor  1000  may be implemented as a computer, such as a desktop computer, a laptop computer, a server computer, a mainframe computer, or other suitable computing device. 
         [0043]    The processor  1002  may include, for example, a general-purpose microprocessor, a digital signal processor, a microcontroller or other device capable of executing instructions retrieved from a computer-readable storage medium. Processor architectures generally include execution units (e.g., fixed point, floating point, integer, etc.), storage (e.g., registers, memory, etc.), instruction decoding, peripherals (e.g., interrupt controllers, timers, direct memory access controllers, etc.), input/output systems (e.g., serial ports, parallel ports, etc.) and various other components and sub-systems. 
         [0044]    The storage  1004  is a non-transitory computer-readable storage medium suitable for storing instructions executed by the processor  1002  and data processed by the processor  1002 . The storage  1004  may include volatile storage such as random access memory, non-volatile storage (e.g., a hard drive, an optical storage device (e.g., CD or DVD), FLASH storage, read-only-memory), or combinations thereof. 
         [0045]    The storage  1004  includes valve characterization module  1006 , valve acoustic signal processing module  1008 , valve acoustic signals  1010 , and valve baseline acoustic signals  1012 . The valve baseline acoustic signals  1012  include initialization signals and/or parameters of initialization signals acquired from each valve  202  at a point in time when the valve  202  is operating at an optimal level. For example, the valve baseline acoustic signals  1012  may include valve acoustic signals acquired when the valve  202  is initially put into service, or standardized signals representative of operation of a fully functional valve  202 . The valve acoustic signals  1010  include signals detected by the acoustic sensors  204  coupled to each valve  202 . The valve acoustic signals  1010  may be processed via execution of the valve acoustic signal processing  1008 , and the results analyzed via execution of the valve characterization  1006  to determine the condition of each valve  202 . 
         [0046]    The valve acoustic signal processing  1008  includes instructions executed by the processor  1002  to prepare the valve acoustic signals for analysis. For example, the valve acoustic signal processing  1008  may include instructions to reduce the amplitude of ambient noise present in the valve acoustic signals, to transform the time-domain valve acoustic signals into frequency-domain representations, to filter unwanted frequency content from the valve acoustic signals, and to provide other signal processing functionality disclosed herein. 
         [0047]    The valve characterization  1006  includes instructions executed by the processor  1002  to characterize and evaluate the condition of each valve  202 . For example, the valve characterization  1006  may include instructions to compare valve acoustic signals processed via the valve acoustic signal processing  1008  to the valve baseline acoustic signals  1012 , or to determine whether the valve acoustic signals processed via the valve acoustic signal processing  1008  exhibit a trend of change indicative of valve performance degradation. In some embodiments, the valve characterization  1006  may include instructions that identify a leak in a valve  202  by identifying an increase in amplitude within a particular frequency band determined to indicate a leak. The valve characterization  1006  may also include instructions that measure the time duration of acoustic signal generated by opening or closing the valve  202  and determine whether the duration is increasing over time as an indication of performance degradation. The valve characterization  1006  may further include instructions that determine whether the valve is open or closed based on the valve acoustic signals processed via the valve acoustic signal processing  1008 . Instructions of valve characterization  1006  may cause the processor  1002  to issue an alert indicating that the valve  202  may require attention if a leak or other performance anomaly is detected. The alert may be presented on a display device or otherwise provided to an authority responsible for maintaining the integrity of the valves  202 . 
         [0048]    The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.