Patent Description:
Actuators are often used to control the operation of valves and other fluid system components. An actuator may be of any number of different designs including pneumatic, hydraulic, electric and so on. Fluid driven actuators use pressurized fluid, such as air, to move one or more fluid driven actuator members (e.g., pistons, diaphragms, bellows, etc.) in order to move a valve element (e.g., a rotary valve stem, plug, diaphragm, and/or bellows) for control (e.g., shutoff, metering, directional control) of system fluid passing through the valve.

A conventional actuated valve assembly uses a spring biased pneumatic actuator for two-position operation of the valve between an actuated position, in response to pressurization of the actuator inlet port to overcome the biasing spring and move the actuator piston and connected valve member, and a normal or return position, in response to venting of the actuator inlet pressure and spring movement of the actuator piston and valve member.

The cycle life of a valve actuated by a piston-style actuator is often limited by the actuator piston seals (e.g., O-rings or gaskets), which may be subject to frequent cycle movement (and corresponding wear), extreme temperatures, and harsh atmospheric conditions. As a result of these conditions, piston seal wear or loss of lubricant can lead to leakage past the actuator seals and/or increased friction of the piston within the actuator housing. Over time, this increasing leakage or friction may result in incomplete or impeded valve actuation and eventual valve failure, resulting in compromised fluid supplies, unscheduled system downtime, and repair costs.

In other applications, undesirable conditions in the valve (e.g., increased friction, seat damage, system contamination) may result in increased resistance to actuation within the valve, which may result in an impeded or stuck condition of the actuated valve, in addition to potential valve leakage and/or fluid system contamination. In still other applications, undesirable conditions in the valve (e.g., loss of packing load, fractured actuator spring or valve element) may result in reduced resistance to actuation within the valve, which may result in valve leakage.

In still other applications, actuator pressurization forces and/or spring return stroke forces may produce undesirable conditions, including excessive closing force between the valve member and valve seat (which may result in seat/seal wear, deformation, and/or particle generation) or valve actuation that is faster or slower than desired. To provide an adequate seal against the valve element in a shutoff condition, a valve is often provided with a soft (e.g., plastic, elastomer) valve seat against which the valve element seals upon valve closure. In applications involving high cycle frequency, high actuator pressures (in the case of a "normally open" fluid driven actuator) and/or valve seat distorting conditions, such as high temperature, high flow, or chemical reactivity, the closing force between the valve element and the valve seat may generate wear particles, which may contaminate the fluid system and/or result in valve seat leakage.

<CIT> disclose a known method of monitoring performance of a fluid driven actuator for a valve.

The invention provides a method of monitoring performance of a fluid driven actuator for a valve according to claim <NUM>. Further preferred embodiments of the invention are defined in the dependent claims.

The embodiments corresponding to <FIG>, <FIG> and <FIG> are not according to the claimed invention.

While various inventive aspects, concepts and features of the inventions may be described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects, concepts and features may be used in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present inventions. Still further, while various alternative embodiments as to the various aspects, concepts and features of the inventions--such as alternative materials, structures, configurations, methods, circuits, devices and components, alternatives as to form, fit and function, and so on--may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the inventive aspects, concepts or features into additional embodiments and uses within the scope of the present inventions even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present disclosure, however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Parameters identified as "approximate" or "about" a specified value are intended to include both the specified value and values within <NUM>% of the specified value, unless expressly stated otherwise. Further, it is to be understood that the drawings accompanying the present disclosure may, but need not, be to scale, and therefore may be understood as teaching various ratios and proportions evident in the drawings. Moreover, while various aspects, features and concepts may be expressly identified herein as being inventive or forming part of an invention, such identification is not intended to be exclusive, but rather there may be inventive aspects, concepts and features that are fully described herein without being expressly identified as such or as part of a specific invention, the inventions instead being set forth in the appended claims. Descriptions of exemplary methods or processes are not limited to inclusion of all steps as being required in all cases, nor is the order that the steps are presented to be construed as required or necessary unless expressly so stated.

The present disclosure contemplates systems and methods for monitoring and/or controlling performance of a fluid driven (e.g., pneumatic) actuator. For example, performance of a fluid driven actuator may be monitored to identify actuator failure, valve failure, or conditions (e.g., leakage past the fluid driven actuator member, changes in required actuation force) indicating that actuator failure or valve failure is imminent. While exemplary embodiments in the present disclosure relate to spring biased pneumatic actuator assembled with linearly actuated valves (e.g., diaphragm valves), the features and aspects described in the present disclosure may additionally or alternatively be applied to other types of actuators (e.g., hydraulic or other fluid driven actuators, non-spring biased actuators and double acting actuators being not according to the claimed invention) other types of valves (e.g., rotary valves, gate valves, etc.), and other types of pressurized fluid applications.

While sensors installed in or assembled with the valve (e.g., flowmeters, electromechanical switches) may monitor valve conditions and performance characteristics of the valve, extreme or demanding system fluid conditions (e.g., pressure, temperature, corrosive/caustic fluids) may limit the types of sensors that may be used and/or the service life of such sensors.

Valve and actuator performance may be monitored by measuring actuator fluid flow conditions, which may, but need not, provide for measuring or sensing such conditions at a location remote from the valve actuator in the actuator fluid circuit, for example, at or proximate to a pilot valve that selectively supplies pressurized actuator fluid to an actuator supply line connected with an inlet port of the actuator. At this remote location, isolation from any extreme or demanding system fluid or environmental conditions may be accomplished.

Different types of sensors may be provided in fluid communication with a valve actuator. As one non-claimed example, a flow sensor directly or indirectly connected with the actuator may be used to detect flow associated with fluid pressure or spring return movement of an actuator piston (e.g., to confirm actuation of the valve, timing of actuation, duration of actuation, pressure required for actuation, etc.), or flow associated with leakage past the actuator piston (e.g., to identify progressive actuator wear, or impending actuator failure due to gross leakage). As another example according to the claimed invention, a pressure sensor directly or indirectly connected with the actuator is used to detect changes in actuator supply line pressure associated with fluid pressure or spring return movement of the actuator piston (e.g., to confirm actuation of the valve, timing of actuation, duration of actuation, pressure required for actuation, etc.), or with leakage past the actuator piston (e.g., to identify progressive actuator wear, or impending actuator failure due to gross leakage).

<FIG> schematically illustrates an actuated valve system <NUM> including an actuated valve <NUM> having a fluid operated (e.g., pneumatic) actuator <NUM> having an actuator port <NUM> connected to an actuator fluid source <NUM> by an actuator supply line <NUM> and a pilot valve <NUM> (e.g., solenoid operated switching valve) or other supply valve. The actuator supply line <NUM> may be formed from a variety of components and arrangements, including, for example, separate conduit components (e.g., tube, pipe, hose) and porting or passages integrated into either or both of the actuator and pilot valve, such that the pilot valve may be assembled directly to the actuator port.

To actuate the valve <NUM>, the pilot valve <NUM> is operated to open the actuator fluid source <NUM> to the actuator port <NUM>, to supply pressurized actuator fluid to the actuator inlet port to move the actuator piston <NUM>, thereby moving the valve element <NUM>. This results in fluid flow through the actuator supply line and an increase in pressure in the actuator supply line. The pressure and/or flow may be monitored by a sensor <NUM> (e.g., pressure transducer, flowmeter) in fluid communication with the actuator supply line <NUM>. The sensor <NUM> may be provided with control circuitry <NUM>, which may be connected with (e.g., by a wired or wireless connection) a system controller <NUM> (e.g., computer) proximate to or remote from the sensor <NUM>. The system controller <NUM> may include circuitry (e.g., microprocessor) for analyzing the measured changes in the fluid flow conditions to verify normal operating conditions or to identify non-compliant system conditions.

In the above described arrangement, detection of failure of the actuated valve <NUM>, or other non-compliant conditions, for example, based on deviations in actuator fluid flow from expected flow during actuation (e.g., stored predetermined or previously generated parameters), can be used to provide alerts to the user of the failure condition (e.g., through communication with the system controller <NUM>), for example, to prompt system shutdown and valve maintenance or replacement.

Additionally, detection of actuated valve performance deviations in a still functioning valve may be used to provide alerts to the user of conditions likely to progress to valve failure. As one example, a measurable decrease in pressure within the pressurized actuator supply line or a measurable flow through the actuator supply line <NUM> when the actuator <NUM> is pressurized but not being actuated may indicate leakage past the fluid driven actuator member <NUM> (e.g., actuator piston). In a high cycle valve, actuator piston seal wear and/or loss of lubricant can cause increasing actuator piston leakage over the life of the actuator, until the leakage becomes severe enough to limit or prevent valve actuation. By identifying actuator piston leakage before the level of leakage reaches an actuation impeding level, planned maintenance may be performed on the actuator during a scheduled downtime, thereby avoiding emergency shutdowns and/or lost production.

As another non-claimed example, the identification of the occurrence of a valve actuation at a greater than expected actuator inlet pressure, by measuring a change or inflection in the actuator inlet pressure corresponding to actuation, or by measuring the time delay or duration at which a change in inlet pressure or flow rate corresponding to actuator piston movement occurs, may indicate increased valve resistance to actuation, for example, due to valve element wear or galling, loss of lubrication, system contamination, or other factors. Early identification of these potential conditions may allow for timely valve maintenance.

As yet another non-claimed example, the identification of the occurrence of a valve actuation at a lower than expected actuator inlet pressure, by measuring a change or inflection in the actuator inlet pressure corresponding to actuation, or by measuring the time delay or duration at which a change in inlet pressure or flow rate corresponding to actuator piston movement occurs, may indicate reduced valve resistance to actuation, for example, due to loss of packing load, weakening of diaphragm/bellows biasing forces, or other such factors. Early identification of these potential conditions may allow for timely valve maintenance.

By communicating these measured performance conditions to a system controller programmed to diagnose and address problematic valve performance conditions, valve maintenance may be automatically initiated either upon detection of a valve failure, or in anticipation of an impending valve failure. The system controller may be programmed to automatically schedule maintenance procedures, requisition parts from stock, or place orders for replacement system components and assemblies.

In an exemplary embodiment not according to the claimed invention, performance conditions of an actuated valve are determined by measuring the pressure profile of a piston-style actuator before, during, and after valve actuation, using a pressure transducer (or other such pressure sensor) that measures the pressure of a pressurized volume or chamber of actuator fluid (e.g., air, nitrogen) upstream of the actuator. A pressure containment device (e.g., pressurized cylinder or other such chamber, or a backpressure device) may be connected in fluid communication with the actuator supply line to maintain a set pressure in the actuator supply line from which deviations in the set pressure may be measured. In an exemplary arrangement, as schematically shown in <FIG>, an actuated valve system <NUM> includes an actuated valve <NUM> having a pneumatically operated actuator <NUM> with an actuator port <NUM> connected to a pressurized chamber <NUM> (e.g., sample cylinder) by an actuator supply line <NUM> and a pilot valve <NUM> (e.g., solenoid operated switching valve) or other supply valve, with the pressurized chamber <NUM> connected with an actuator fluid source <NUM>. To actuate the valve <NUM>, the pilot valve <NUM> is operated to open the pressurized chamber <NUM> to the actuator port <NUM>, to supply pressurized actuator fluid from the chamber to the actuator inlet port. This results in a temporary decrease in pressure within the chamber <NUM>, until the chamber is refilled by the actuator fluid source <NUM> and the pressure is restored. The pressure within the chamber <NUM> is monitored by a pressure transducer <NUM>, which may be connected with (e.g., by a wired or wireless connection) a system controller <NUM> (e.g., computer) proximate to or remote from the pressure transducer <NUM>.

As shown in the valve cycle pressure profile P of <FIG>, and with reference to the schematic embodiment of <FIG>, when the pressurized actuator fluid is initially supplied to a properly functioning actuator <NUM> (e.g., by opening a pilot valve between the pressurized volume and the actuator), at time t<NUM> (corresponding to actuation of the pilot valve to the open position), the pressure within the pressurized chamber <NUM>, as measured by the pressure transducer, decreases from a set pressure p<NUM> to a first reduced pressure p<NUM>, as the supplied fluid pressure builds on the actuator piston <NUM> to a pressure sufficient to move the piston (e.g., against a biasing spring <NUM> and/or valve element <NUM> resistance). As the actuator piston <NUM> moves to the actuated position and the pressurized fluid fills a cavity <NUM> in the actuator behind the piston, the pressure within the chamber <NUM> further decreases from the first reduced pressure p<NUM> to a second reduced pressure p<NUM>, generally at a shallower or more gradual slope than the pressure change from set pressure p<NUM> to first reduced pressure p<NUM>.

To restore the pressure in the pressurized chamber <NUM>, the actuator fluid source <NUM> supplies pressurized actuator fluid to the pressurized chamber. While the actuator fluid source <NUM> may be selectively opened to the pressurized chamber <NUM> (e.g., by user initiated or programmed opening of a supply valve), in another embodiment, flow between the actuator fluid source and the pressurized chamber is limited using a reduced orifice or other flow restriction <NUM> to delay pressure increases within the chamber <NUM>, such that the changes in chamber pressure resulting from valve actuation may be more easily measured. The result of this restricted flow condition is evident in the slope of the pressure curve between the second reduced pressure p<NUM> and the post-actuation recovered pressure p<NUM>, which shows the gradual increase in pressure within the pressurized chamber after actuation of the valve is completed.

Deviations from the typical pressure profile P of <FIG> may provide an indication of a worn, damaged or defective condition in the valve or actuator. For example, as shown in the valve cycle pressure profile PA, a first reduced pressure p1a that is lower than expected may indicate increased resistance to actuation (requiring higher fluid pressure as supplied by the pressurized chamber), for example, due to increased friction between the actuator piston and housing or between the valve stem (or other valve element) and the valve seat. As another example, as shown in the valve cycle pressure profile PB, a first reduced pressure p1b that is higher than expected may indicate reduced resistance to actuation (requiring lower fluid pressure as supplied by the pressurized chamber), for example, due to reduced valve packing or seat sealing load, a fractured or weakened valve diaphragm or bellows, or a fractured or weakened actuator spring.

As still another example, as shown in the valve cycle pressure profile PC of <FIG>, a second reduced pressure p2c that is higher than expected and/or at an earlier time T than expected (as compared to the pressure point p2b in <FIG>) may indicate an incomplete actuator stroke, while the substantial absence of a second reduced pressure point, as shown in the valve cycle pressure profile PD, with the pressure curve increasing from the first reduced pressure p<NUM> to the post-actuation recovered pressure p<NUM> may indicate a valve or actuator that is stuck.

As yet another example, as shown in the valve cycle pressure profile PE of <FIG>, a post-actuation recovered pressure p3e that is lower than the set pressure p<NUM> may indicate leakage past the actuator piston sufficient to prevent full recovery of the pressure in the pressurized chamber until the pilot valve is closed. In many applications, leakage of pressurized actuator fluid past the actuator, for example, due to worn piston seals, or dried or otherwise lost lubricant, is a precursor to complete actuator failure (e.g., due to gross actuator leakage) resulting in the valve being stuck (e.g., in the spring-biased closed position). Accordingly, initial detection of smaller amounts of leakage may allow for diagnosis of impending gross leakage and actuator failure. This initial leak detection may be relied upon for scheduled maintenance, such as actuator repair or replacement.

When the system controller <NUM> analyzes the measured changes in the valve cycle pressure profile and identifies such deviating pressure conditions, the system controller may generate an output communicating the non-compliant condition, which may be provided in the form of an audible or visual alert, or an alert message (e.g., text or email message).

In applications where a pressure sensor is disposed upstream from the pilot valve, as in the embodiment of <FIG>, characteristics of the valve/actuator performance cannot be measured by the sensor when the pilot valve is in the closed or actuator venting condition. In another arrangement according to the claimed invention, a pressure sensor or pressure transducer is provided downstream from the pilot valve and upstream from the actuator, to allow for detection of changes in actuator inlet pressure regardless of whether the pilot valve is in the actuator pressurizing condition or in the actuator venting condition. In an exemplary embodiment, as schematically shown in <FIG>, an actuated valve system <NUM> includes a valve <NUM> having a pneumatically operated actuator <NUM> with an actuator port <NUM> connected to an actuator fluid source <NUM> by an actuator supply line <NUM> and pilot valve <NUM> (e.g., solenoid operated switching valve) or other supply valve, with a pressure transducer <NUM> or other such pressure sensor disposed in the actuator supply line <NUM> between the pilot valve <NUM> and the actuator port <NUM>, and connected with (e.g., by a wired or wireless connection) a system controller <NUM> (e.g., computer) proximate to or remote from the pressure transducer <NUM>.

To actuate the valve <NUM>, the pilot valve <NUM> is operated to open the actuator fluid source <NUM> to the actuator port <NUM>, to supply pressurized actuator fluid to the actuator inlet port. This results in an initial increase in pressure in the actuator supply line <NUM>, as measured by the pressure transducer <NUM>. When the pressure in the actuator supply line is sufficient to overcome the actuator spring <NUM> biasing force and any resistance to actuation by the valve element <NUM> (e.g., valve stem operating torque, or diaphragm/bellows biasing forces), the actuator piston <NUM> is moved against the actuator spring <NUM> to the actuated position, causing a brief drop in the actuator inlet pressure due to the increased volume below (upstream from) the actuator piston. To return the valve <NUM> to the normal (e.g., biased closed) position, the pilot valve <NUM> is operated to vent or exhaust the pressurized actuator fluid in the actuator supply line <NUM> and below the actuator piston <NUM>. When the pressure in the actuator supply line is reduced by an amount sufficient to allow the compressed actuator spring <NUM> to move the actuator piston <NUM> against the actuator fluid and against any resistance to actuation by the valve element <NUM> (e.g., valve stem operating torque, or diaphragm/bellows biasing forces), the actuator piston <NUM> is moved to the spring-biased position, causing a brief increase in the actuator inlet pressure due to the reduced volume below (upstream from) the actuator piston.

As shown in the valve cycle pressure profile of <FIG>, and with reference to the schematic embodiment of <FIG>, when the pressurized actuator fluid is initially supplied to a properly functioning actuator <NUM> on a properly functioning valve at time t<NUM> (e.g., by opening a pilot valve between the pressurized volume and the actuator), an inflection in the pressure profile or brief reduction in the rate of pressure increase (at px) during pressurization indicates an inlet pressure at which operation of the actuator (against actuator spring biasing and valve element resistance forces) is effected. This pressure inflection point px can identify changes or deviations in actuator performance and/or valve element resistance (e.g., operating torque), for example, to identify conditions such as valve element galling, loss of lubricant, or seat clipping (as identified by an increase in the pressure inflection point px), or insufficient packing torque, actuator spring damage, or damaged diaphragm/bellows (as identified by a decrease in the pressure inflection point px). The time duration of the reduced rate of pressure increase can indicate the valve cycle time, which may provide further indication of actuation difficulties (e.g., due to increased valve actuation torque or gross actuator leakage). Furthermore, the absence of an inflection point px during actuator pressurization may provide an indication that the valve failed to actuate.

As further shown in the valve cycle pressure profile of <FIG>, when the pressurized actuator fluid is vented or exhausted from the valve actuator <NUM> at time t<NUM> (e.g., by switching the pilot valve to an exhaust/vent switching position) through the actuator supply line <NUM>, an inflection in the pressure profile or brief reduction in the rate of pressure drop (at py) during depressurization indicates an inlet pressure at which the actuator spring force overcomes the inlet pressure and valve element resistance to actuation to effect operation of the actuator to the normal or biased position. This pressure inflection point py can identify changes or deviations in actuator performance and/or valve element resistance (e.g., operating torque), for example, to identify conditions such as actuator spring damage, valve element galling, loss of lubricant, or seat clipping (as identified by a decrease in the pressure inflection point py), or insufficient packing torque or damaged diaphragm/bellows (as identified by an increase in the pressure inflection point py). The time duration of the reduced rate of pressure drop can indicate the valve cycle time, which may provide further indication of actuation difficulties (e.g., due to increased valve actuation torque or gross actuator leakage). Furthermore, the absence of an inflection point py during actuator depressurization may provide an indication that the valve failed to actuate.

According to another non-claimed aspect of the present disclosure, a pressure transducer or other such pressure sensor may be configured to measure pressure differential between a pressurized volume or chamber of actuator fluid upstream of a pilot valve and the actuator supply line between the pilot valve and the actuator inlet. In an exemplary arrangement, as schematically shown in <FIG>, an actuated valve system <NUM> includes a valve <NUM> having a pneumatically operated actuator <NUM> with an actuator port <NUM> connected to a pressurized chamber <NUM> (e.g., sample cylinder) by an actuator supply line <NUM> and pilot valve <NUM> (e.g., solenoid operated switching valve) or other supply valve, with the pressurized chamber <NUM> connected with an actuator fluid source <NUM>. Flow between the actuator fluid source <NUM> and the pressurized chamber <NUM> may be limited using a reduced orifice or other flow restriction <NUM> to delay pressure increases within the chamber <NUM>, such that the changes in chamber pressure resulting from valve actuation may be more easily measured. To actuate the valve <NUM>, the pilot valve <NUM> is operated to open the pressurized chamber <NUM> to the actuator port <NUM>, to supply pressurized actuator fluid from the chamber to the actuator inlet port. This results in a temporary decrease in pressure within the chamber <NUM>, until the chamber is refilled by the actuator fluid source <NUM> and the pressure is restored.

The chamber pressure Pinlet, the supply line pressure Pline, and the differential pressure Pdiff between the chamber <NUM> and the actuator supply line <NUM> is monitored by a pressure transducer <NUM>, which may be connected with (e.g., by a wired or wireless connection) a system controller <NUM> (e.g., computer) proximate to or remote from the pressure transducer <NUM>. As shown in the valve cycle pressure profile of <FIG>, and with reference to the schematic embodiment of <FIG>, when the pressurized actuator fluid is initially supplied to a properly functioning actuator <NUM> at time t<NUM>(e.g., by opening the pilot valve <NUM>), the differential pressure Pdiff, as measured by the pressure transducer <NUM>, decreases from a set pressure differential pd<NUM>to a first reduced differential pressure pd<NUM> as the supplied fluid pressure builds on the actuator piston <NUM> to a pressure sufficient to move the piston (e.g., against a biasing spring <NUM> and/or valve element resistance). As the actuator piston <NUM> moves to the actuated position and the pressurized fluid fills a cavity <NUM> in the actuator <NUM> behind the piston, the pressure differential further decreases from the first reduced pressure differential pd<NUM>to a second reduced pressure pd<NUM>, generally at a shallower or more gradual slope than the pressure differential change from set pressure differential pd<NUM> to first reduced pressure differential pd<NUM> until the pressure differential pd<NUM> approaches zero (with the actuator supply line pressure being substantially equal to the chamber pressure). To restore the pressure in the pressurized chamber <NUM>, the actuator fluid source <NUM> supplies pressurized actuator fluid to the pressurized chamber, for example, as described above with regard to the embodiment of <FIG>.

When the pilot valve is closed to return the actuated valve to the normal position at time t<NUM>, the differential pressure pd increases from the second reduced pressure differential pd<NUM> to a third pressure differential pd<NUM> as the actuator <NUM> and actuator supply line <NUM> are vented or exhausted through the pilot valve <NUM> to reduce the actuator inlet pressure to a pressure low enough for the actuator biasing spring <NUM> to overcome (in combination with any valve element resistance). At this third pressure differential pd<NUM>, spring biased movement of the actuator piston <NUM> to the normal or return position causes a slower, more gradual increase in the pressure differential to a fourth pressure differential pd<NUM>, at which the piston has completed its return stroke, and the remainder of the actuator inlet pressure is vented, causing the pressure differential pd to return to the set pressure differential pd<NUM>.

As with the above examples, information regarding the timing, duration, and pressure required for actuation may be determined by identifying the inflection points in the pressure differential curve corresponding to the identified pressure differentials pd<NUM>,pd<NUM>, pd<NUM>, pd<NUM>. Further, the absence of the inflection points, as shown in alternative differential pressure profile Pdiff', provides an indication that the actuator <NUM> has failed to actuate. Additionally, if there is a leak past the actuator piston <NUM> when the pilot valve <NUM> is open, closure of the pilot valve <NUM> will result in an increase in the upstream pressure (as shown at Pinlet'). If there is a leak past the pilot valve when the pilot valve is closed, the set pressure differential will be reduced (as shown at pd<NUM>').

According to another aspect of the present disclosure, an actuated valve may be provided with an actuator fluid supplying/venting pilot valve having a pressure retaining backpressure device (e.g., check valve, relief valve) connected with (e.g., directly or indirectly assembled or integrated with) an exhaust port of the pilot valve to maintain a nominal, non-actuating positive pressure on the actuator inlet when the actuator is in the normal (e.g., spring biased) position, to provide for identification of leakage past the actuator by a pressure transducer or other such pressure sensor disposed between the actuator inlet port and the backpressure device.

In an exemplary arrangement, as schematically shown in <FIG>, an actuated valve system <NUM> includes a valve <NUM> having a pneumatically operated actuator <NUM> with an actuator port <NUM> connected by an actuator supply line <NUM> to a pilot valve <NUM> downstream from an actuator fluid source <NUM>, with a pressure transducer <NUM> connected with the actuator supply line <NUM> and a backpressure device <NUM> connected with (e.g., directly or indirectly assembled or integrated with) the exhaust port <NUM> of the pilot valve <NUM>. When the actuated valve <NUM> is returned to the normal (e.g., biased closed) position, by operating the pilot valve <NUM> to vent or exhaust the pressurized actuator fluid in the actuator supply line <NUM> and below the actuator piston <NUM>, the backpressure device <NUM> retains a nominal, non-actuating positive pressure (e.g., <NUM>-<NUM> KPa (<NUM>-<NUM> psi)) in the actuator supply line <NUM> and against the spring biased actuator piston <NUM>. In such an arrangement, leakage of actuator fluid past the actuator piston <NUM> may be detected by a measured pressure decrease below the pressure setting of the backpressure device <NUM> by the pressure transducer <NUM> below the pressure setting of the backpressure device <NUM> while the pilot valve <NUM> is in the closed/exhaust position. In an exemplary embodiment, the pilot valve <NUM>, pressure transducer <NUM>, and backpressure device <NUM> may be provided together as an integrated assembly <NUM>, for example, for ease of installation, reduction of system footprint, etc. Other system managing and/or monitoring components may also be provided in the integrated assembly, including, for example, a cycle counter, flowmeter, processor/controller, and/or output display (e.g., LED, LCD).

The arrangement of <FIG> additionally provides indication of the timing, duration, and pressure conditions of operation of the valve actuator, by identifying the inflection points in the actuation pressure profile during pressurization and depressurization of the actuator <NUM>, as shown and described above with respect to the embodiment of <FIG>.

In the actuated valve arrangement of <FIG>, in addition to leakage past the actuator <NUM>, a decrease in pressure detected by the pressure transducer <NUM> may additionally or alternatively correspond to leakage past the pilot valve <NUM>, and/or leakage past the backpressure device <NUM>. In another embodiment, a pressure retaining backpressure device may be connected with (e.g., directly or indirectly assembled or integrated with) a supply port of a pilot valve, thereby excluding the effects of any leakage past the pilot valve from the transducer pressure detection. In such an arrangement, the backpressure device may be configured to permit bidirectional or two-way flow--forward flow of actuator fluid from the pilot valve to the actuator inlet during actuator pressurization (i.e., pilot valve open), and backpressure retaining reverse flow from the actuator supply line to the pilot valve during actuator depressurization (i.e., pilot valve closed).

In an exemplary arrangement, as schematically shown in <FIG>, an actuated valve system <NUM> includes a valve <NUM> having a pneumatically operated actuator <NUM> with an actuator port <NUM> connected by an actuator supply line <NUM> to a pilot valve <NUM> downstream from an actuator fluid source <NUM>, with a pressure transducer <NUM> and a bidirectional backpressure device <NUM> connected with (e.g., directly or indirectly assembled or integrated with) the supply port <NUM> of the pilot valve <NUM>. The exemplary backpressure device <NUM> includes a supply passage <NUM> permitting forward or supply flow to the actuator supply line <NUM> but sealing against reverse flow from the actuator supply line (e.g., using a first check valve <NUM>), and an exhaust passage <NUM> in parallel with the supply passage <NUM>, permitting reverse/exhaust flow from the actuator supply line <NUM> while retaining a nominal, non-actuating back pressure (e.g., <NUM>-<NUM> KPa (<NUM>-<NUM> psi)) in the actuator supply line and against the spring biased actuator piston <NUM> (e.g., using a second check valve <NUM>) when the actuated valve <NUM> is returned to the normal (e.g., biased closed) position. In such an arrangement, leakage of actuator fluid past the actuator piston <NUM> may be detected by a measured pressure decrease below the pressure setting of the backpressure device <NUM> by the pressure transducer <NUM> while the pilot valve <NUM> is in the closed/exhaust position. In an exemplary embodiment, any two or more of the pilot valve <NUM>, pressure transducer <NUM>, and backpressure device <NUM> may be provided together as an integrated assembly <NUM>, for example, for ease of installation, reduction of system footprint, etc. Other system managing and/or monitoring components may also be provided in the integrated assembly, including, for example, a cycle counter, flowmeter, processor/controller, and/or output display (e.g., LED, LCD).

In some actuated valve systems, a backpressure device, as described herein, may perform additional functions. For example, the backpressure device may additionally or alternatively retain a non-actuating positive pressure against the actuator inlet port during the actuator return stroke, to apply a dampening force thus reducing the actuator output force in the normal, spring return condition. This reduced return force may, for example, reduce valve seat wear in a normally closed actuated valve. For such an arrangement, the backpressure setting may be greater than the <NUM>-<NUM> KPa (<NUM>-<NUM> psi) nominal setting described above, and may be selected to reduce the return force to a desired amount. However, such an arrangement may still be used in combination with the sensor systems and methods described above, by retaining a pressurized fluid in the actuator supply line to facilitate sensing of pressure changes during or after valve actuation. Exemplary backpressure arrangements for reducing actuator return force are described in the concurrently filed U. Provisional Application entitled "ACTUATED VALVE SYSTEMS WITH REDUCED ACTUATOR RETURN FORCE.

According to another aspect of the present disclosure, an actuated valve system may be provided with a valve control module configured to control actuation fluid supply to, and exhaust from, the valve actuator while monitoring the pressure in the actuator supply line. In one such exemplary arrangement, as schematically illustrated in <FIG>, an actuated valve system <NUM> includes a valve <NUM> having a pneumatic actuator <NUM>, and a valve control module <NUM> having an actuation port <NUM> connected with an actuator inlet port <NUM> of the actuator <NUM>, a pressurization port <NUM> connected with an actuator fluid source <NUM>, and an exhaust port <NUM> for venting pressurized actuation fluid. The valve control module <NUM> includes a pilot valve arrangement <NUM> connecting the actuation port <NUM> with the pressurization port <NUM> and the exhaust port <NUM>, a fluid sensor <NUM> measuring a fluid condition (e.g., pressure) between the pilot valve arrangement <NUM> and the actuator inlet port <NUM>, and a controller <NUM> in circuit communication with the sensor <NUM> and with the pilot valve arrangement <NUM> for operation of the pilot valve arrangement to the first, second and third conditions.

The exemplary pilot valve arrangement <NUM> is operable, by operation of the controller <NUM>, between first, second, and third conditions. In the first condition, the pilot valve arrangement <NUM> permits flow between the pressurization port <NUM> and the actuation port <NUM> and blocks flow between the actuation port and the exhaust port <NUM> to pressurize the actuator inlet port <NUM>, for example, for operation of the actuator <NUM> and movement of the valve element <NUM> to an actuated (e.g., open) position. In the second condition, the pilot valve arrangement <NUM> blocks flow between the pressurization port <NUM> and the actuation port <NUM> and permits flow between the actuation port and the exhaust port <NUM> to vent the actuator inlet port <NUM>. Where the actuator <NUM> is a single acting (e.g., spring biased) actuator, this venting of the pressurized actuator inlet port <NUM> allows the actuator to move the valve element <NUM> to a return (e.g., closed) position. In the third condition, the pilot valve arrangement <NUM> blocks flow between the pressurization port <NUM> and the actuation port <NUM> and blocks flow between the actuation port and the exhaust port <NUM>, to capture pressurized fluid in the actuator inlet port <NUM>.

Many different pilot valve arrangements may be utilized to provide the first, second and third conditions described above. In one exemplary embodiment, as shown in <FIG>, a pilot valve arrangement 745a includes a first shutoff valve 746a connecting the pressurization port <NUM> with the actuation port <NUM>, and a second shutoff valve 748a connecting the exhaust port <NUM> with the actuation port <NUM>. In the first condition, the first shutoff valve 746a is open and the second shutoff valve 748a is closed to pressurize the actuator inlet port <NUM>. In the second condition, both the first and second shutoff valves 746a, 748a are closed to capture pressurized fluid between the pilot valve arrangement 745a and the actuator inlet port <NUM>. In the third condition, the first shutoff valve 746a is closed and the second shutoff valve 748a is open to vent the actuator inlet port <NUM>. In one such embodiment, the first shutoff valve 746a is a normally closed solenoid valve and the second shutoff valve 748a is a normally open solenoid valve, such that in the event of lost power, the first shutoff valve returns to the closed position and the second shutoff valve returns to the open position, allowing the normally closed actuator <NUM> to return the valve element <NUM> to the closed position.

In another exemplary embodiment, as shown in <FIG>, a pilot valve arrangement 745b includes a three-position, three-way switching valve 747b having a first switching position, corresponding to the first condition, opening the pressurization port 742b to the actuation port 741b and blocking flow to the exhaust port 743b, a shutoff position, corresponding to the second condition, blocking flow between the actuation port 741b and both the pressurization and exhaust ports 742b, 743b, and a second switching position, corresponding to the third condition, opening the actuation port 741b to the exhaust port 743b and blocking flow from the pressurization port 742b. In one such embodiment, the switching valve 747b is configured to fail to the second switching position (the position shown in <FIG>), such that in the event of lost power, the normally closed actuator <NUM> returns the valve element <NUM> to the closed position.

According to an aspect of the present disclosure, the pilot valve arrangement <NUM> may be selectively operated between the first, second, and third conditions to increase (using the first condition), decrease (using the second condition), and/or maintain (using the third condition) the actuator inlet pressure, with the sensor <NUM> monitoring the pressure in real time to control such pressure adjustments. In an exemplary application, the pilot valve(s) may be rapidly actuated or pulsed to increase or decrease actuator inlet pressure, with the pressure sensor <NUM> providing instantaneous feedback used by the controller <NUM> to further pulse the pilot valve(s) for further adjustment of the actuator inlet pressure. In one such exemplary embodiment, the pilot valve arrangement 745a, 745b is configured to provide a fill or pressurization pulse duration between approximately <NUM> and approximately <NUM> to begin the actuation cycle, and an exhaust pulse duration between approximately <NUM> and approximately <NUM>, at a cycle time between approximately <NUM> and approximately <NUM>,<NUM>, with the pilot valve arrangement 745a, 745b being maintained in the third (pressure maintaining) condition and the pressure sensor <NUM> monitoring actuator inlet pressure between pulses. Based on feedback to the controller <NUM> (e.g., from the pressure sensor <NUM>), to increase or decrease the rate at which the captured pressure is adjusted, the controller may adjust the pulse duration and pulse frequency of the first (pressurization) and second (exhaust) conditions.

In an exemplary application, a non-actuating positive pressure may be captured, such that the valve control module <NUM> functions as a backpressure device, similar to the embodiments of <FIG> and <FIG>, described in greater detail above. This non-actuating positive pressure may be provided, for example, for monitoring of the captured pressure to detect and/or quantify leakage past the actuator, as described in greater detail above.

As another example, a non-actuating positive pressure may be used to apply a dampening force against the actuator inlet port to reduce the actuator output force in the spring return condition, for example, to minimize deformation and/or wear (and resulting particle generation) of the valve seat during closing actuation of the valve. This reduced closing force may effectively extend the cycle performance of the valve by minimizing seal damage due to repetitive actuation. In applications requiring both frequent cycling and high integrity sealing during shutoff (e.g., non-cycling) conditions, the dampening actuator inlet pressure may be selectively or automatically removed or exhausted to provide for increased actuator closing force as needed.

As yet another example, a non-actuating positive pressure may additionally or alternatively be used to facilitate a quicker forward stroke actuation of the valve, as the positive, non-actuating actuator inlet port pressure can be increased to an actuating pressure more quickly, as compared to increasing the actuator inlet port pressure from atmospheric pressure.

Additionally or alternatively, control and/or monitoring of a captured actuating pressure (i.e., pressure sufficient to at least partially actuate the valve) between the pilot valve arrangement and the actuator inlet port may be used in a variety of applications. Sensor monitoring of the captured actuator inlet port pressure may be used to identify timing and/or duration of valve actuation in non-claimed examples, or, according to the claimed invention, is used to identify the pressure at which the valve actuates, as described in greater detail with respect to the embodiment of <FIG>. This monitoring of the actuator inlet pressure profile over time identifies potential issues such as increases or decreases in required actuation force (e.g., corresponding to changes in actuation torque of a rotary valve or axial movement bellows or diaphragm valve element), actuator leakage, actuator sticking, or other conditions. The controller <NUM> may be programmed to compensate for deviations that are within an acceptable range (e.g., by increasing or decreasing captured actuator inlet port pressure), and/or to provide an alert when the measured actuator inlet pressure profile indicates valve system maintenance is required.

As another example, a captured actuator inlet pressure may be controlled to apply to the actuator a desired actuator inlet pressure that is less than the full fluid pressure of the actuator fluid source <NUM>, but still sufficient to at least partially actuate the valve. This reduced actuation pressure may, for example, provide for slower actuation of the valve (i.e., a "soft start") for example, for controlled opening in applications sensitive to flow surges in a normally closed valve, or to reduce the valve closing force in a normally open valve. As another example, a reduced actuation pressure may provide for quicker return stroke actuation of the valve, as the reduced actuator inlet port pressure exhausts more quickly (and is more quickly overcome by the spring force) than would a fully pressurized actuator inlet port. As still another example, the actuator inlet pressure may be precisely controlled to provide for incomplete or partial actuation of the actuator, for example, to limit or regulate flow through the valve.

According to another aspect of the present disclosure, an actuator may be further adapted to facilitate monitoring and control of the actuated valve system by a captured actuation pressure. As one example, the actuator <NUM> may be provided with high flow capacity actuator porting to increase flow rates during pressurization and/or depressurization/exhaust of the actuator, for example, to facilitate quick forward stroke and/or return stroke actuation, and/or reduced pressurization and/or depressurization/exhaust time (e.g., reduced pulse durations) to allow more time for pressure sensing and feedback and controller analysis and actuation adjustment between pulses.

As another example, the spring return actuator <NUM> may be provided with a biasing spring arrangement having an increased spring rate (e.g., by providing a stiffer spring <NUM> and/or additional springs, in parallel and/or in series) such that one or more partial flow positions may more predictably correspond with one or more predetermined applied actuator inlet pressures. As one example, the spring return actuator <NUM> may be provided with a spring rate (e.g., kg/cm (lbs/in)) that is greater than about five times the spring force (e.g., kg (lbs)) in the closed position, as compared to a conventional valve actuator spring rate of less than three times the spring force in the closed position. This increased spring rate may provide significant, measurable, and predictable differences in actuator pressure required to move the actuator piston <NUM> and valve element <NUM> to one or more incremental positions between the normal position and the actuated (e.g., open) position of the valve. In an exemplary embodiment with a biasing spring that closed the actuator, the spring rate is such that the actuator pressure required to move the actuator piston and valve element from the closed position to the open position is at least <NUM>% greater than the actuator pressure required to begin the actuator stroke from the closed position (the "base actuation pressure"). Accordingly, with a base actuation pressure of X (e.g., <NUM> KPa (<NUM> psi)) incremental actuated positions between the fully closed and fully open valve positions may be calibrated at a range of actuation pressures between X (<NUM> KPa (<NUM> psi)) and at least <NUM>. 5X (<NUM> KPa (<NUM> psi)). In one such example, the actuator pressure required to move the actuator member and valve element to a midpoint position of the valve element between the normal (closed) and actuated (open) positions is at least about <NUM>% greater than the actuator pressure required to begin the actuator stroke from the normal position (e.g., at least about <NUM> KPa (<NUM> psi) in the above example). In embodiments utilizing a biasing spring arrangement having an increased spring rate, a non-actuating backpressure (as described herein) may be applied to the actuator during the return stroke to dampen the return stroke prevent the biasing spring arrangement from applying excessive closing forces to the valve seat.

According to an exemplary aspect of the present disclosure, the actuated valve system <NUM> may be monitored and controlled using the single pressure sensor <NUM> within the valve control module <NUM>. The controller <NUM> may be programmed with a number of known system parameters (e.g., actuator stroke, actuator volume displacement, fluid pressure, fluid temperature, spring rate), such that pressure sensor <NUM> feedback to the controller <NUM>, combined with this programmed system information, may be used to calculate actuation pressure, actuation speed, closing force, and other such operating conditions, and to make suitable adjustments to the pulsing or other such operation of the pilot valve arrangements <NUM> to achieve desired flow control performance.

In other embodiments, additional system sensors may provide data regarding one or more system parameter to the controller to further facilitate desired adjustments to flow control and system performance. For example, a fluid temperature sensor may provide feedback to the controller <NUM> to identify a high fluid temperature condition, and the controller may adjust operation of the valve to reduce valve closing force (e.g., by increasing backpressure against the actuator return stroke, as described above). This arrangement may allow the actuated valve system to be used over a larger temperature range. As another example, a fluid pressure sensor or flowmeter may provide feedback to the controller <NUM> regarding fluid flow conditions, and the controller may adjust operation of the valve to increase or reduce fluid flow accordingly (e.g., by adjusting a partially open condition of the valve, by adjusting durations during which the valve is open, etc.).

The controller <NUM> may be connected with (e.g., by a wired or wireless connection) a system controller <NUM> (e.g., computer) proximate to or remote from the valve control module <NUM>. The system controller <NUM> may include circuitry (e.g., microprocessor) for analyzing the measured changes in the fluid flow conditions to verify normal operating conditions or to identify non-compliant system conditions, and to generate communications (e.g., email, text message, etc.) alerting users of such conditions.

In addition to arrangements in which actuator inlet pressure is controlled to limit the closing force of an actuated valve, the present application also contemplates other systems and methods for providing a reduced force return stroke for an actuated valve assembly, for example to reduce closing forces between a valve element (e.g., diaphragm, poppet) and a valve seat seal. While exemplary embodiments in the application relate to spring biased pneumatic actuator assembled with linearly actuated valves (e.g., diaphragm valves), the features and aspects described in the present application may additionally or alternatively be applied to other types of actuators (e.g., hydraulic or other fluid driven actuators, non-spring biased actuators and double acting actuators being not according to the claimed invention), other types of valves (e.g., rotary valves, gate valves, etc.), and other types of pressurized fluid applications.

<FIG> schematically illustrates an actuated valve system <NUM> including a valve <NUM> having a fluid flow controlling valve element <NUM> (e.g., valve stem, diaphragm) operatively connected with a fluid operated (e.g., pneumatic) actuator <NUM> with an actuator port <NUM> connected to an actuator fluid source <NUM> by an actuator supply line <NUM> and a pilot valve <NUM> (e.g., solenoid operated switching valve) or other supply valve. In other embodiments, the pilot valve may be assembled directly to the actuator port, without use of a separate supply line. To move the valve element <NUM>, the pilot valve <NUM> is moved to a first switching position to open the actuator fluid source <NUM> to the actuator port <NUM>. This results in fluid flow through the actuator supply line and an increase in pressure in the actuator port <NUM>, and against a fluid driven actuator member <NUM> (e.g., one or more pistons) within the actuator. When a minimum actuating pressure is supplied to the actuator port, the resulting actuating force on the actuator member <NUM> overcomes a biasing force applied by a biasing member <NUM> (e.g., one or more springs) within the actuator, and any resistance to actuation of the valve element <NUM> (e.g., friction, valve packing load, valve fluid pressure, etc.) to move the actuator member <NUM> from the first, normal or return position to the second, actuated position. The actuator member <NUM> is directly or indirectly connected with the valve element <NUM> to correspondingly move the valve element from the normal position (e.g., a valve closed or shutoff position) to the actuated position (e.g., valve open or fluid flow position).

To return the valve element <NUM> to the normal position, the pilot valve <NUM> is moved to a second switching position to vent or exhaust the pressurized actuator fluid in the actuator supply line <NUM> and upstream of the actuator member <NUM>. The biasing force applied to the actuator member <NUM> by the biasing member <NUM> moves the actuator member <NUM> against the venting actuator fluid and against any resistance to actuation by the valve element <NUM> to the normal or return position, thereby moving the valve element <NUM> to the corresponding normal position.

According to an exemplary aspect of the present application, to reduce return stroke forces applied by the actuator <NUM>, the actuated valve system <NUM> may be provided with a backpressure arrangement <NUM> (e.g., a spring loaded or otherwise biased check valve, or a relief valve) in fluid communication with the actuator inlet port <NUM> to retain a non-actuating positive pressure (i.e., smaller than the minimum actuating pressure) against the actuator member <NUM> when the pilot valve <NUM> is moved to the second position. The non-actuating positive pressure applies a dampening force against the actuator member <NUM> and counter to the biasing force of the biasing member to produce a net return force smaller than the biasing force, but still sufficient to return the valve element <NUM> from the actuated position to the normal position. The non-actuating positive pressure, and the corresponding net return force, may be selected, for example, to provide a desired actuation speed and closing force for the particular application. In an exemplary embodiment, the non-actuating positive pressure may be about <NUM>% - <NUM>%, or about <NUM>% - <NUM>%, or about <NUM>% of the minimum actuating pressure, and the net return force may be about <NUM>% - <NUM>%, or about <NUM>% - <NUM>%, or about <NUM>% of the spring biasing force. Such an arrangement, maintaining a base, non-actuating positive pressure against the actuator member, may additionally provide for quicker pressurized actuation of the valve actuator, as the pressure in the actuator supply line, actuator inlet, and actuator piston chamber will be pressurized from the non-actuating positive pressure, rather than from a fully vented, atmospheric pressure.

In the illustrated embodiment of <FIG>, the backpressure arrangement includes a backpressure device <NUM> assembled with the pilot valve exhaust port <NUM>. The exemplary backpressure device <NUM>, as shown in <FIG>, includes a check valve or relief valve type arrangement, with a body <NUM> having a passage <NUM> extending from a first port <NUM> to a second port <NUM>, with a seat <NUM> disposed in the passage. A seal member <NUM> (e.g., a ball or plug) is disposed in the passage <NUM> and is biased (e.g., by spring <NUM>) into sealing engagement with the seat <NUM>. The seal member separates from the seat at a set inlet port pressure (or "cracking pressure") to release through the second port <NUM> any excess pressure greater than the set pressure, thereby maintaining the desired non-actuating positive pressure upstream of the backpressure arrangement <NUM> at the actuator inlet port.

In other embodiments, the backpressure arrangement may be provided in a variety of other locations in the actuated valve system <NUM>, including, for example, assembled with the pilot valve supply port <NUM> (schematically in <FIG> at 870a), installed in the actuator supply line <NUM> (schematically at 870b), assembled with the valve actuator inlet port <NUM> (schematically at 870c), integrated with the valve actuator <NUM> (schematically at 870d), and integrated with the pilot valve <NUM> (schematically at 870e).

In some arrangement, as shown at 870a, 870b, 870c, and 870d, the backpressure arrangement receives both pressurizing actuator fluid (during actuator pressurization) and venting actuator fluid (during actuator depressurization). In such an arrangement, the backpressure device <NUM>', as shown in <FIG>, may include both a first, supply passage <NUM>', permitting forward or supply flow to the actuator supply line but sealing against reverse flow from the actuator supply line, and a second, exhaust passage <NUM>' in parallel with the supply passage <NUM>', permitting reverse/exhaust flow from the actuator supply line while retaining a nominal, non-actuating back pressure, as described above. While many different configurations may be utilized, in one embodiment, the backpressure device <NUM>' may include an exhaust flow check/relief valve arrangement, as shown in <FIG> and described above, in parallel with a supply flow check/relief valve having a supply seal member <NUM>' (e.g., a ball or plug) disposed in the supply passage <NUM>' and biased (e.g., by spring <NUM>') into sealing engagement with a supply seat <NUM>', to block reverse flow through the supply passage while permitting forward, pressurizing flow through the supply passage.

According to another exemplary aspect of the present application, a backpressure arrangement for retaining a positive non-actuating pressure against an actuator inlet may be provided with a depressurization mechanism to reduce or eliminate the retained positive non-actuating pressure, such that the net return force of the actuator increases. In "normally closed" actuated valve embodiments, such an arrangement may allow for softer or lighter return stroke valve shutoff during rapid or frequent valve cycling, while allowing for increased valve sealing force during extended shutoff periods where high integrity valve shutoff may be desired (e.g., system shutdown/maintenance). In one embodiment, as shown schematically in <FIG>, a backpressure arrangement may include a vent/purge valve <NUM> directly or indirectly connected with the actuator supply line <NUM> and selectively operable to release the retained pressure in the actuator supply line, thereby increasing the net return force of the actuator.

In another embodiment, the backpressure arrangement may include a controlled or engineered leak path configured to allow the positive pressure to bleed or reduce over time, such that the net return force of the actuator automatically increases when the actuator is maintained in the normal, non-actuated position for a time period greater than a standard valve cycle period during valve cycling. For example, where an actuated valve is typically cycled every <NUM> to <NUM> seconds, an engineered leak path may provide a leak rate sufficient to substantially eliminate the non-actuation positive pressure in about <NUM>-<NUM> seconds. In an exemplary embodiment, an engineered leak path may be sized or configured to provide a leak rate between about <NUM> sccm and <NUM> sccm under pneumatic pressures of about <NUM> KPa (<NUM> psi) to <NUM> KPa (<NUM> psi).

An engineered leak path may be provided in a variety of locations in the actuated valve system, including, for example, any one or more of the pilot valve, the actuator supply line, the actuator, and the backpressure device. In the exemplary backpressure device <NUM> of <FIG>, an engineered leak path may, for example, be provided in one or more of the body <NUM> (e.g., a pinhole leak port intersecting the passage <NUM>, at 809a), the seat <NUM> (e.g., a groove, notch, or other such feature, at 809b), and the seal member <NUM> (e.g., a groove, notch, or other such feature, at 809c). In the exemplary backpressure device 870a of <FIG>, an engineered leak path may, for example, be provided in one or more of the body <NUM>' (e.g., a pinhole leak port intersecting the exhaust passage <NUM>', at 809a', or the supply passage <NUM>', at 809b'), the exhaust valve seat <NUM>' (e.g., a groove, notch, or other such feature, at 809c'), the supply valve seat <NUM>' (e.g., a groove, notch, or other such feature, at 809d'), the exhaust valve seal member <NUM>' (e.g., a groove, notch, or other such feature, at 809e'), and the supply valve seal member <NUM>' (e.g., a groove, notch, or other such feature, at 809f ').

<FIG> illustrates another exemplary embodiment, in which a backpressure arrangement is integrated into an actuator assembly <NUM>. The actuator assembly <NUM> includes a housing <NUM> defining an inlet port <NUM> and first and second piston chambers <NUM>, <NUM> receiving first and second force transmitting pistons <NUM>, <NUM>. The second piston <NUM> is integrated with an output shaft <NUM> for applying an output force to a valve element in a valve (not shown) with which the actuator <NUM> is assembled. The first piston chamber <NUM> also retains a biasing spring <NUM> that engages the first piston <NUM> to force the first and second pistons <NUM>, <NUM> downward. To operate the actuator <NUM>, pressurized actuator fluid (e.g., air) applied to the inlet port <NUM> passes through passages <NUM>, <NUM> in the first and second pistons <NUM>, <NUM> to pressurize lower portions of the piston chambers <NUM>, <NUM>, forcing the pistons upward against the biasing spring <NUM> to move the output shaft <NUM> upward.

In the exemplary embodiment, a backpressure arrangement <NUM> is integrated into the second piston <NUM>, including a seal member <NUM> biased (by spring <NUM>) into sealing engagement with a seat <NUM> disposed in the second piston passage <NUM>. When the actuator inlet port <NUM> is pressurized, the pressurized fluid moves the seal member <NUM> against the spring <NUM> to permit fluid flow into, and pressurization of, the lower portion of the second piston chamber <NUM>. When the actuator <NUM> is depressurized, sealing engagement of the seal member <NUM> with the seat <NUM> retains pressurized fluid in the second piston chamber <NUM> to apply a dampening force against the second piston <NUM> and counter to the biasing force of the spring <NUM>. An engineered leak path, as discussed above, may be provided, for example, in any one or more of the actuator housing, the second piston <NUM>, the seat <NUM>, and the seal member <NUM>, such that over time, fluid pressure in the second piston chamber <NUM> is reduced or eliminated, and the full return force of the biasing spring <NUM> is applied to the second piston <NUM>.

According to another exemplary aspect of the present application, an actuated valve system may be provided with a backpressure arrangement configured to limit the pressure applied to the valve actuator and the resulting "forward stroke" actuator output force, for example, to limit the closing force of a "normally open" valve actuator (e.g., to limit valve seat wear/damage). In such an arrangement, a backpressure device may be assembled with the pilot valve inlet or supply port, the actuator inlet port, or the actuator supply line to choke off the inlet pressure at a desired actuation pressure lower than the inlet or source pressure by a selected sealing differential pressure of the backpressure device. While a number of suitable backpressure devices may be utilized, in one embodiment, the backpressure device <NUM> of <FIG> may be assembled with the pilot valve inlet port in a reverse orientation relative to the embodiment of <FIG>, such that the check/relief valve arrangement permits full pressurizing flow from the actuated valve system pressure source to the pilot valve until the pressure at the actuator inlet port reaches a selected pressure defined by a rated differential pressure at which the seal member <NUM> seals against the seat <NUM>, thereby retaining a reduced actuation pressure against the actuator member. For example, if a source pressure of <NUM> KPa (<NUM> psi) is applied to an actuated valve system including a backpressure device having a differential seating pressure of <NUM> KPa (<NUM> psi), the pressure applied to the pilot valve would be choked off at <NUM> KPa (<NUM> psi), effectively reduce the forward stroke force output of the actuator.

In another embodiment, the backpressure device <NUM>' of <FIG> may be assembled with the pilot valve supply port, the actuator inlet port, or the actuator supply line in a reverse orientation relative to the embodiment of <FIG>, such that the check valve arrangement of the first passage <NUM>' permits full, unrestricted flow in the venting/exhaust direct, while the check valve arrangement of the second passage <NUM>' permits full pressurizing flow from the actuated valve system pressure source to the pilot valve until the pressure at the actuator inlet port reaches a selected pressure defined by a rated differential pressure at which the seal member <NUM>' seals against the seat <NUM>', thereby retaining a reduced actuation pressure against the actuator member.

Claim 1:
A method of monitoring performance of a fluid driven actuator (<NUM>) for a valve (<NUM>), the method comprising:
during a time period, operating a pilot valve (<NUM>) to supply pressurized fluid from an actuator fluid source (<NUM>) through an actuator supply line (<NUM>) to an inlet port (<NUM>) of the actuator to move an actuator piston (<NUM>) against an actuator spring (<NUM>) from a biased position to an actuated position, the pilot valve being operable to supply pressurized fluid to the actuator supply line in a first position, and to exhaust pressurized fluid from the actuator supply line in a second position;
using a pressure sensor (<NUM>) disposed in the actuator supply line between the pilot valve and the actuator inlet port, measuring pressure changes in the actuator supply line during the time period, the measured pressure changes defining a valve cycle pressure profile including a reduction in a rate of pressure increase corresponding to movement of the actuator piston from the biased position to the actuated position;
obtaining, from the reduction in the rate of pressure increase, an inlet pressure at which operation of the actuator is effected; and
analyzing the valve cycle pressure profile to identify a non-compliant condition in at least one of the valve and the actuator based on the inlet pressure at which operation of the actuator is effected; and
generating an output communicating the identified non-compliant condition.