Patent Description:
The present disclosure relates generally to mechanical seals. More particularly, this disclosure relates to mechanical seals that include sensor and/or monitoring systems configured to monitor seal operating conditions.

Seals, such as dry gas seals, are used in a wide variety of applications including, for example, gas compressors and other rotating equipment such as gas and steam turbines, turbo expanders, centrifugal pumps, and the like. Such seals are used to seal a rotating interface between a shaft and a housing of a compressor and/or other rotating equipment. The principle of dry gas seal technology is that the sealing faces are non-contacting and a clean and dry gas is allowed to pass through the seal interface. During operation, a portion of the flow of the gas being processed may be diverted from the operating flow and filtered to remove particulate and liquid mist that may be present in the operating flow. This diverted gas flow may be further processed, for example, superheated to a temperature above its dew point, and provided to the dry gas seal as an operating fluid.

JPH08254402A describes a rotary shaft monitoring device to measure the run-out and movement quantities of a rotary shaft without any contact with the rotary shaft. It is constituted by a rotary shaft monitoring device is composed of a rotary shaft, a magnetic field, a sensor, a sleeve, a magnetic field protection box, and a sensor position adjuster. A magnetic substance (for example, a permanent magnet) is mounted on a part which is provided on the rotary shaft or the outer circumference of the rotary shaft, the magnet is detected by the magnetic sensor so that the run-out quantity of the rotary shaft and the axial movement quantity are detected and an abnormal diagnosis such as a low speed rotor can be easily measured.

<CIT> describes a method for monitoring the condition of a mechanical seal in an apparatus provided with a rotating part, in particular in a pump which has a rotating shaft for the forwarding of a fluid. In this method the sound emission of the seal is continually measured at discrete times in the operating state of the apparatus and at least one statistical characteristic value is won from the acoustic signals. The analog acoustic signals are converted prior to the determination of the statistical characteristic value into analog demodulated signals, the maximum frequency of which is less than about <NUM>.

The present disclosure relates generally to dry gas seals, and more particularly, devices, systems, and methods for establishing and monitoring lift off and touch down speeds of a dry gas seal to provide an assessment of seal operating conditions and/or degradation of dry gas seal faces. The invention concerns a seal monitoring system for a dry gas seal assembly as defined in claim <NUM>, and a method of operating a dry gas seal monitoring system as defined in claim <NUM>.

In one example, a seal monitoring system for a dry gas seal assembly is disclosed. The seal monitoring system may include a dry gas seal, an acoustic emissions sensor, a speed sensor, and a processor. The dry gas seal may have a stator portion with a first seal face and a rotor portion with a second seal face, wherein the dry gas seal may be positioned between a stationary housing and a rotatable shaft, and the rotor portion may be configured to rotate with the rotatable shaft. The acoustic emissions sensor may be configured to sense when the first seal face and the second seal face are in an operational condition relative to one another and output a signal indicative of the operational condition. The speed sensor may sense the speed of the rotatable shaft at speeds below one thousand (<NUM>,<NUM>) rotations per minute (RPMs) and may be configured to output a signal indicative of a rotational speed of the rotatable shaft. The processor may be configured to receive the signal from the speed sensor and the signal from the acoustic emissions sensor, and may establish an operating condition of the dry gas seal based on the signal from the speed sensor when the first seal face and the second seal face reach the operational condition relative to one another.

Alternatively or additionally to any of the embodiments above, the operational condition of the first seal face relative to the second seal face may be a lift-off operational condition of the dry gas seal.

Alternatively or additionally to any of the embodiments above, the operational condition of the first seal face relative to the second seal face may be a touch-down operational condition of the dry gas seal.

Alternatively or additionally to any of the embodiments above, the operational condition of the first seal face relative to the second seal face may include a lift-off operational condition of the dry gas seal and a touch-down operational condition of the dry gas seal.

Alternatively or additionally to any of the embodiments above, the processor may be configured to establish the operating condition of the dry gas seal based on the signal received from the speed sensor when the dry gas seal reaches the lift-off operational condition and the signal received from the speed sensor when the dry gas seal reaches the touch-down operational condition.

Alternatively or additionally to any of the embodiments above, the speed sensor may be a Hall-effect sensor.

Alternatively or additionally to any of the embodiments above, the speed sensor may sense speeds of the rotatable shaft at speeds below five hundred (<NUM>) rotations per minute (RPMs).

Alternatively or additionally to any of the embodiments above, the speed sensor may be configured to sense speeds of the rotatable shaft at speeds below one thousand (<NUM>,<NUM>) RPMs based on sensing two or more sense elements configured to rotate with the rotatable shaft.

Alternatively or additionally to any of the embodiments above, the two or more sense elements may include slots disposed on the rotor portion of the dry gas seal.

Alternatively or additionally to any of the embodiments above, the seal monitoring system may further comprise a ring configured to rotate with the rotatable shaft, wherein the ring includes the two or more sense elements.

Alternatively or additionally to any of the embodiments above, one or more of the two or more sense elements may include an indicator element configured to allow the processor to determine a rotational direction of the rotatable shaft based on the signal output from the speed sensor.

Alternatively or additionally to any of the embodiments above, the processor may be configured to determine an axial position of the rotor portion relative to the stator portion based on the signal output from the speed sensor.

In another example, a method of operating a dry gas seal monitoring system having a dry gas seal forming a seal between a housing and a rotatable shaft is provided. The illustrative method may include determining when one of a separation of a first seal face from a second seal face of the dry gas seal and a contact of the first seal face with the second seal face occurs. The illustrative method may further include, determining a rotational speed indicative of a speed of the rotatable shaft, associating the rotational speed with an occurrence of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face, and determining an operating condition of the dry gas seal based on the association of the rotational speed with an occurrence of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above, determining an operating condition of the dry gas seal may include monitoring, over time, rotational speeds associated with occurrences of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above, the method may further comprise establishing a first baseline speed for the separation of the first seal face from the second seal face during run-up and establishing a second baseline speed for the contact of the first seal face with the second seal face during run-down; and wherein monitoring, over time, the rotational speeds associated with occurrences of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face may include one of comparing the first baseline speed with the rotational speeds associated with subsequent occurrences of the separation of the first seal face from the second seal face and comparing the second baseline speed with the rotational speeds associated with subsequent occurrences of the contact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above, determining an operating condition of the dry gas seal may include monitoring, over time, the rotational speeds associated with occurrences of both of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above, the method may further comprise establishing a first baseline speed for the separation of the first seal face from the second seal face and establishing a second baseline speed for the contact of the first seal face with the second seal face; and wherein determining an operating condition of the dry gas seal may include one of comparing the first baseline speed with rotational speeds associated with occurrences of the separation of the first seal face from the second seal face and comparing the second baseline speed with the rotational speeds associated with occurrences of the contact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above, determining an operating condition of the dry gas seal may be based on the association of rotational speeds with occurrences of both of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face.

Alternatively or additionally to any of the embodiments above, determining an operating condition of the dry gas seal may include one of comparing rotational speeds associated with occurrences of the separation of the first seal face from the second seal face to a lift-off speed threshold and comparing rotational speeds associated with occurrences of the contact of the first seal face with the second seal face to a touch-down threshold.

Alternatively or additionally to any of the embodiments above, determining when one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face occurs may be based on a signal from an acoustic emissions sensor of the dry gas seal system.

A dry gas seal is also described herein. The dry gas seal may include a rotor portion, a stator portion, a plurality of sense elements, and a speed sensor. The stator portion may have a first seal face and the rotor portion may have a second seal face, where the first seal face and the second seal face may be positioned between a rotatable shaft and a stationary housing to form a seal. The plurality of sense elements may be configured to rotate in response to the rotation of the rotatable shaft. The speed sensor may be at least partially secured relative to the stator portion and may be configured to sense the plurality of sense elements. The speed sensor may be further configured to sense a rotational speed of the rotatable shaft at speeds below one thousand (<NUM>,<NUM>) rotations per minute (RPMs) based on sensing the plurality of sense elements.

Alternatively or additionally to any of the embodiments above, the plurality of sense elements may include a plurality of slots.

Alternatively or additionally to any of the embodiments above, one or more of the plurality of slots may include a notch configured to be sensed by the speed sensor to indicate a direction of rotation of the rotatable shaft.

Alternatively or additionally to any of the embodiments above, one or more of the plurality of slots may include an axially extending taper.

Alternatively or additionally to any of the embodiments above, the axially extending taper may taper at fifty-five (<NUM>) degrees relative to a plane perpendicular to an axis of rotation of the rotatable shaft.

Alternatively or additionally to any of the embodiments above, the plurality of sense elements may be disposed on the rotor portion.

Alternatively or additionally to any of the embodiments above, the dry gas seal may further comprise a collar coupled to the rotatable shaft and configured to rotate with the rotatable shaft; and wherein the plurality of sense elements may be disposed on the collar.

Alternatively or additionally to any of the embodiments above, the dry gas seal may further comprise a processor configured to receive an output from the speed sensor; and wherein the processor is configured to use the output from the speed sensor to determine an axial position of the rotor portion relative to the stator portion.

Alternatively or additionally to any of the embodiments above, the dry gas seal may further comprise an acoustic emissions sensor at least partially secured relative to the stator portion; and wherein the acoustic emissions sensor may be configured to sense a sound indicative of an operational condition of the first seal face relative to the second seal face.

In another example, a dry gas seal monitoring system is disclosed. The dry gas seal monitoring system may include a dry gas seal, a collar, a plurality of sense elements, a speed sensor, an acoustic emissions sensor, and a processor. The dry gas seal may have a first seal face and a second seal face, wherein the dry gas seal is positionable to form a seal between a stationary housing and a rotatable shaft. The collar may be configured to rotate with the rotatable shaft and the plurality of sense elements may be disposed on the collar. The speed sensor may be configured to sense the plurality of sense elements disposed on the collar as the plurality of sense elements rotate in response to rotation of the rotatable shaft. The acoustic emissions sensor may be configured to monitor an operational condition of the first seal face relative to the second seal face. The processor may be configured to receive a first signal from the speed sensor and a second signal from the acoustic emissions sensor and establish a baseline speed for the operational condition based on the first signal and the second signal.

Alternatively or additionally to any of the embodiments above, the processor may be configured to monitor changes over time in a speed sensed by the speed sensor by comparing the first signal at occurrences of the second signal to the baseline speed.

Alternatively or additionally to any of the embodiments above, the second signal from the acoustic emissions sensor may be indicative of one of a separation of the first seal face from the second seal face and a contact of the first seal face with the second seal face. Alternatively or additionally to any of the embodiments above, the speed sensor may be configured to sense the plurality of sense elements and sense speeds of the rotatable shaft at speeds below one thousand (<NUM>,<NUM>) RPMs based on sensing the plurality of sense elements.

Alternatively or additionally to any of the embodiments above, the speed sensor may be configured to sense the plurality of sense elements and sense speeds of the rotatable shaft at speeds below five hundred (<NUM>) RPMs based on sensing the plurality of sense elements.

Alternatively or additionally to any of the embodiments above, the processor may be configured to determine the direction of rotation of the rotatable shaft based on the first signal received from the speed sensor.

Alternatively or additionally to any of the embodiments above, the processor may be configured to determine an axial position of the rotatable shaft relative to the stationary housing based on the first signal received from the speed sensor.

According to the invention, a seal monitoring system for a dry gas seal assembly is disclosed. The seal monitoring system includes a dry gas seal having a stator portion with a first seal face and a rotor portion with a second seal face, the dry gas seal is configured to be positioned between a stationary housing and a rotatable shaft with the rotor portion configured to rotate with the rotatable shaft, a sense element configured to rotate with the rotatable shaft, a sensor sensing the sense element as the sense element rotates with the rotatable shaft, the sensor configured to output a signal based on the sensing of the sense element, a processor configured to receive the signal from the sensor, and the processor may be configured to determine an axial position of the rotor portion relative to the stator portion based on the signal output from the sensor.

Additionally to any of the embodiments above, the processor may be configured to determine the axial position of the rotor portion relative to the stator portion based on an amplitude of the signal output from the sensor.

Additionally to any of the embodiments above, the signal output from the sensor may include one or more pulses and the processor is configured to determine the axial position of the rotor portion relative to the stator portion based on the one or more pulses in the signal output from the sensor.

Additionally to any of the embodiments above, the seal monitoring system may include two or more sense elements, the two or more sense elements include the sense element, and the processor may be configured to determine the axial position of the rotor portion relative to the stator portion based on one or more of an amplitude of the one or more pulses in the signal, a pulse width of the one or more pulses in the signal, and a width between consecutive pulses in the signal.

Additionally to any of the embodiments above, the seal monitoring system may include two or more sense elements, the two or more sense elements include the sense element, and the two or more sense elements may be configured to be radially spaced circumferentially around the rotatable shaft.

Additionally to any of the embodiments above, the two or more sense elements may be equally radially spaced circumferentially around the rotatable shaft.

Additionally to any of the embodiments above, one or more of the two or more sense elements may be configured to be axially spaced from at least one other sense element of the two or more sense elements.

Additionally to any of the embodiments above, the sense element may have a cross-sectional shape that changes along an axial length of the sense element.

Additionally to any of the embodiments above, the cross-sectional shape that changes along the axial length of the sense element may be a circular shape.

Additionally to any of the embodiments above, the cross-sectional shape that changes along the axial length of the sense element may be a trapezoidal shape.

Additionally to any of the embodiments above, the sense element may have a surface with a depth relative to the sensor that changes over an axial length of the sense element.

Additionally to any of the embodiments above, the depth relative to the sensor that changes over an axial length of the sense element may be an axial taper in the surface.

Additionally to any of the embodiments above, the sense element may be disposed on the rotor portion.

Additionally to any of the embodiments above, the sense element may be disposed on a sleeve of the rotor portion.

Additionally to any of the embodiments above, the seal monitoring system may include a collar configured to be coupled to the rotatable shaft and rotate with the rotatable shaft, and the sense element may be disposed on the collar.

According to the invention, a method of operating a dry gas seal monitoring system having a dry gas seal forming a seal between a housing and a rotatable shaft is disclosed. The method may include sensing a sense element rotating with the rotatable shaft, obtaining a signal based on the sensing of the sense element rotating with the rotatable shaft, and determining an axial position of a rotor portion relative to a stator portion based on the signal obtained, the rotor portion and the stator portion form a seal interface of the dry gas seal between the rotatable shaft with which the rotor portion is configured to rotate and a stationary housing.

Additionally to any of the embodiments above, determining the axial position of the rotor portion relative to the stator portion may be based on an amplitude of the signal obtained.

Additionally to any of the embodiments above, determining the axial position of the rotor portion relative to the stator portion may comprise comparing the amplitude of the signal obtained to a threshold value.

Additionally to any of the embodiments above, determining the axial position of the rotor portion relative to the stator portion may comprise comparing the amplitude of the signal obtained at a time to amplitudes of the signal obtained at one or more other times during operation of the dry gas seal.

Additionally to any of the embodiments above, the signal obtained may include one or more pulses and determining the axial position of the rotor portion relative to the stator portion is based on the one or more pulses.

Additionally to any of the embodiments above, the method may further include sensing two or more sense elements rotating with the rotatable shaft, the two or more sense elements include the sense element, and wherein determining the axial position of the rotor portion relative to the stator portion is based on one or more of an amplitude of the one or more pulses in the signal, a pulse width of the one or more pulses in the signal, and a width between consecutive pulses in the signal.

According to the invention, the method further includes sensing two or more sense elements rotating with the rotatable shaft, the two or more sense elements include the sense element, and determining a rotational speed indicative of a speed of the rotatable shaft at speeds below one thousand (<NUM>,<NUM>) RPMs based on sensing the two or more sense elements rotating with the rotatable shaft.

According to the invention, the method further includes determining when one of a separation of a first seal face and a second seal face and a contact of the first seal face with the second seal face occurs, associating the rotational speed with an occurrence of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face, and determining an operating condition of the dry gas seal based on the rotational speed associated with the occurrence of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face.

In another example, a dry gas seal is disclosed. The dry gas seal may include a stator portion having a first seal face, a rotor portion having a second seal face, wherein the first seal face and the second seal face are configured to form a seal between a rotatable shaft and a stationary housing, a plurality of sense elements configured to rotate in response to rotation of the rotatable shaft, a speed sensor at least partially secured relative to the stator portion, the speed sensor is configured to sense the plurality of sense elements, and wherein the speed sensor is configured to sense a rotational speed of the rotatable shaft at speeds below one thousand (<NUM>,<NUM>) rotations per minute (RPMs) based on sensing the plurality of sense elements and output a signal indicative of an axial position of the rotor portion relative to the stator portion.

Alternatively or additionally to any of the embodiments above, the plurality of sense elements may be configured to be radially spaced circumferentially around the rotatable shaft.

Alternatively or additionally to any of the embodiments above, the plurality of sense elements are configured to be equally radially spaced circumferentially around the rotatable shaft.

Alternatively or additionally to any of the embodiments above, one or more of the plurality of sense elements may be configured to be axially spaced from at least one other sense element of the plurality of sense elements.

Alternatively or additionally to any of the embodiments above, a sense element of the plurality of sense elements may have a cross-sectional shape that changes along an axial length of the sense element.

Alternatively or additionally to any of the embodiments above, the cross-sectional shape that changes along the axial length of the sense element may be a circular shape.

Alternatively or additionally to any of the embodiments above, the cross-sectional shape that changes along the axial length of the sense element may be a trapezoidal shape.

Alternatively or additionally to any of the embodiments above, a sense element of the plurality of sense elements may include an axially extending taper.

Alternatively or additionally to any of the embodiments above, the plurality of sense elements may be disposed on a sleeve of the rotor portion.

Alternatively or additionally to any of the embodiments above, the dry gas seal may include a collar configured to be coupled to the rotatable shaft and rotate with the rotatable shaft, and the plurality of sense elements may be disposed on the collar.

Alternatively or additionally to any of the embodiments above, the dry gas seal may include a processor configured to receive the signal output from the speed sensor, and the processor is configured to use the signal output from the speed sensor to determine the axial position of the rotor portion relative to the stator portion. The preceding summary is provided to facilitate an understanding of some of the innovative features unique to the present disclosure and is not intended to be a full description. A full appreciation of the disclosure can be gained by taking the entire specification, claims, drawings, and abstract as a whole.

The disclosure may be more completely understood in consideration of the following description of various illustrative embodiments in connection with the accompanying drawings, in which:.

It should be understood, however, that the intention is not to limit aspect of the disclosure to the particular illustrative embodiments described. On the contrary, the intention is to cover all modifications, the scope of the invention being determined by the appended claims only.

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in the specification.

As used in this specification and the appended claims, and although the term "and/or" is sometimes expressly recited herein, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

Additionally, when particular features, structures, and/or characteristics are described in connection with one embodiment, it should be understood that such features, structures, and/or characteristics may also be used in connection with other embodiments whether or not explicitly described unless clearly stated to the contrary.

Seals are used in a wide variety of applications and/or machines including, for example, gas compressors and other rotating equipment such as gas and steam turbines, turbo expanders, centrifugal pumps and the like. Such seals are used to seal a rotating interface between a shaft and a housing of a compressor and/or other rotating equipment. Although dry gas seals are primarily discussed herein, it is contemplated that the disclosed concepts may be applied to other seals configured to seal a rotating interface between a rotating component and a stationary component.

A dry gas seal may include an inboard (IB) seal and an outboard (OB) seal, which may be known as a tandem seal configuration. In such a configuration, the IB seal may be generally pressurized to the process suction pressure, and this process suction pressure may be sufficient to lift the IB seal off statically. The OB seal may be provided as a backup to the IB seal and is designed to withstand a full pressure if the IB seal fails. If there is an issue with either or both of the IB seal or the OB seals, rubbing of the seal faces may occur and may result in abrasive wear, which is a degenerative process. As the seal wears, damage to the seal faces occurs, the lift off speed increases, and the touch down speed increases.

In some cases, seal leakage and/or outboard (OB) seal pressure may be monitored to assess a condition and seal integrity of a dry gas seal. Such monitoring, however, may only be capable of determining when a serious problem or condition with the seal occurs and urgent shut down of the associated equipment is required. As a machine may be required to be stopped, often immediately with little or no notice of an impending issue, when a serious problem or condition with the seal occurs, there is a need to be able to monitor degeneration of a dry gas seal over time to prevent or mitigate issues resulting in machine down time. By monitoring lift off and touch down speed and their variation over time, a good indication of degeneration of sealing faces can be provided, which in turn may give an indication of progressive seal failure such that the progressive seal failure can be addressed prior to actual seal failure and mitigate downtime of the machine. Typical speed monitoring systems configured to sense operating speeds of a rotatable shaft, however, are not configured to sense the relatively low speeds at which lift off and touch down occur. Additionally or alternatively, sensing an axial position and/or axial movement of the dry gas seal over time (e.g., dry gas seals may be configured to move plus or minus three (<NUM>) millimeters (mm) or other suitable distance during operation of a machine to which the dry gas seal is applied and such axial movement and/or positioning may be monitored) may be used to avoid, or facilitate avoiding, excessive axial movement in a dry gas seal, where excessive axial movement can lead to catastrophic seal failure.

<FIG> depicts a schematic block diagram of an illustrative seal monitoring system <NUM> that may facilitate establishing and/or determining seal conditions for dry gas seals and/or other suitable seal systems (e.g., operating conditions for a seal, operational conditions for a seal interface, etc.). The seal monitoring system <NUM> may include and/or may be configured to monitor a seal interface of a dry gas seal disposed between a rotatable shaft <NUM> and a stationary housing (not shown in <FIG>). The seal monitoring system <NUM> may include a controller <NUM>, a sensing module <NUM>, and one or more sense elements <NUM> configured to rotate in response to rotation of the rotatable shaft <NUM>. The sensing module <NUM> may be configured to sense one or more parameters related to an operation of the dry gas seal and output one or more signals to the controller <NUM>. In some cases, the sensing module <NUM> may include a speed sensor <NUM>, an acoustic emissions sensor <NUM>, and/or one or more other suitable sensors.

In some cases, the sensing module <NUM> may be secured relative to and/or otherwise stationary relative to a stator portion of the dry gas seal and, in some cases, may be formed as part of the stator portion of the dry gas seal. Alternatively or in addition, at least a portion of the sensing module <NUM> may be secured relative to a housing component of a system to which the dry gas seal is applied and/or may be remote from the dry gas seal and/or the system to which the dry gas seal is applied.

The sensing module <NUM> may include the speed sensor <NUM> to facilitate monitoring a speed of a rotor portion of the dry gas seal and/or a speed of the rotor portion and/or the rotatable shaft <NUM>. The speed sensor <NUM> may be configured to sense the rotational speed of the rotor portion and/or the rotatable shaft <NUM> by sensing one or more of the sense elements <NUM> configured to rotate in response to rotation of the rotatable shaft <NUM>. As the one or more sense elements <NUM> rotate in response to rotation of the rotatable shaft <NUM> and rotate past a location of the speed sensor <NUM>, the speed sensor <NUM> may detect the sense elements <NUM> and output a signal indicative of the speed of the rotor portion of the dry gas seal and/or the speed of the rotor portion and/or the rotatable shaft <NUM>. The signal from the speed sensor <NUM> may be provided to the controller <NUM> or other component for further processing.

In some embodiments, the signal indicative of the speed of the rotor portion and/or the rotatable shaft <NUM> may also be indicative of an axial position of the rotor portion and/or the rotatable shaft <NUM>, as discussed in greater detail below. In some cases, the signal may be a pulsed signal with a pulse sequence indicating an axial position of the rotor portion and/or the rotatable shaft <NUM>. Alternatively or in addition, the signal indicative of an axial position of the rotor portion and/or the rotatable shaft <NUM> may be a continuous signal including pulses or other components indicative of a particular axial position or location of the rotor portion and/or the rotatable shaft <NUM>.

The speed sensor <NUM> may be any suitable sensor type that is capable of sensing a speed of the rotatable shaft <NUM>. For example, the speed sensor <NUM> may include a field sensor, an optical sensor, shaft encoder (e.g., at an end of the rotatable shaft <NUM> or other suitable location relative to the rotatable shaft <NUM>) and/or other suitable type of sensor. Example field sensors include, but are not limited to, a magnetic field sensor, a linear variable differential transformer (LVDT), a Hall Effect sensor, and/or other suitable field sensors. In one example, the speed sensor <NUM> may be a Hall Effect sensor, but this is not required.

The acoustic emissions sensor <NUM>, which may be incorporated into the sensing module <NUM>, may be configured to output a signal (e.g., to the controller <NUM> or other component) indicative of an operational condition of a seal interface of the dry gas seal (e.g., an operational condition of a first seal face relative to a second seal face). In one example, as a seal face of the dry gas seal rotates with respect to at least one other seal face of the dry gas seal, the dry gas seal may emit a sound and the sound may change over time as the seal faces separate from one another (e.g., during run-up of the seal and/or the system to which the seal is applied) and/or come into contact with one another (e.g., during run-down of the seal and/or the system to which the seal is applied), and the acoustic emissions sensor <NUM> may be configured to sense the emitted sound and provide an indication of when a lift off (e.g., initial separation of the first seal face and the second seal face after the seal faces have been touching) occurs and/or when a touch down (e.g., initial contact between the first seal face and the second seal face as the relative rotation of the seal faces of the dry gas seal slows down) occurs. The acoustic emissions sensor <NUM> may output a signal indicative of its measurements to the controller <NUM> for processing (e.g., for processing by a processor <NUM> and/or other computing component).

The controller <NUM> may be provided as part of the seal monitoring system <NUM> and may be separate from the sensing module <NUM>, as depicted in <FIG>, or part of the sensing module <NUM>. Alternatively, at least part of the controller <NUM> may be separate from the seal monitoring system <NUM> and may be in communication with the sensing module <NUM>. Further, in some cases, at least part of the controller <NUM> may be located with and/or otherwise be incorporated in the sensing module <NUM>.

The controller <NUM> may comprise, among other features, the processor <NUM>, memory <NUM> (e.g. a non-transitory medium configured to store instructions for execution by the processor, data, and/or other information), and/or an input/output (I/O) <NUM>. The I/O <NUM> may include one or more I/O interfaces and may receive signals from the sensing module <NUM> and the received signals may be sent to the memory <NUM> for storage and/or the processor <NUM> for processing. In some cases, the signal generated by the speed sensor <NUM> may be received by I/O <NUM> and sent to the processor <NUM>. The processor <NUM> may use that signal to establish an operating condition of the dry gas seal and/or determine one or more other parameter values related to the dry gas seal based at least in part on the received signal. In some cases, based at least in part on the signal(s) received from the speed sensor <NUM>, the processor <NUM> may be configured to determine parameter values relating to the dry gas seal including, but not limited to, a speed of the rotatable shaft <NUM>, an axial position of the rotatable shaft <NUM>, a lift off at the seal interface, a lift off speed, a touch down at the seal interface, a touch down speed, when maintenance is needed, an operating condition of the seal interface, and/or other suitable parameter values related to operation of the dry gas seal.

The controller <NUM> may determine an operational condition of the seal interface of the dry gas seal based on signals from the acoustic emissions sensor <NUM>. In some cases, the controller <NUM> may associate the speed of the rotor portion of the dry gas seal or the speed of the rotatable shaft <NUM> at a time the signal indicating the operational condition of the seal interface occurs. The controller <NUM> may save the association in the memory <NUM>, output the association via the I/O <NUM> to a user interface, output a control signal (e.g., to the system to which the dry gas seal is applied and/or to one or more other suitable controllable components), and/or take one or more other suitable actions. In some cases, the outputs from the controller <NUM> may be based on a change in speeds associated with the operational condition over time, speeds associated with the operational condition reaching and/or exceeding a threshold, and/or one or more other factors. In some cases, the operational conditions of the seal interface may be one or both of a lift-off occurrence of a first seal face separating from a second seal face during run-up of the dry gas seal and/or the system to which the dry gas seal is applied and a touch-down occurrence of the first seal face touching the second seal face during run-down of the dry gas seal and/or the system to which the dry gas seal is applied.

<FIG> depicts a schematic perspective view of an illustrative dry gas seal <NUM> (e.g., in cartridge form). The dry gas seal <NUM> may be configured to form a fluid tight seal between a housing and a rotating shaft. In some cases, a stator portion 22a of the dry gas seal <NUM> (e.g., an outer portion of the dry gas seal <NUM> depicted in <FIG>) may be coupled to and/or fixed relative to a housing of a system to which the dry gas seal <NUM> is applied. A rotor portion 22b of the dry gas seal <NUM> (e.g., an inner portion of the dry gas seal <NUM> depicted in <FIG>) may define an opening <NUM> for receiving a rotatable shaft (e.g., the rotatable shaft <NUM> depicted in <FIG>) and may be coupled to the received rotatable shaft and/or otherwise configured to rotate in response to the received rotatable shaft when in use as a seal between a stationary housing and the rotatable shaft.

The dry gas seal <NUM> may include a collar <NUM> (e.g., a reluctor ring and/or other suitable collar) having one or more sense elements <NUM>, as depicted in <FIG>. Alternatively or in addition, the dry gas seal <NUM> may include one or more other suitable components (e.g., a sleeve or other suitable component) configured to include (e.g., carry, define, etc.) one or more sense elements <NUM>. When included, the collar <NUM> may be configured to connect to one or both of the rotor portion 22b of the dry gas seal <NUM> and the rotatable shaft, such that the collar <NUM> may rotate in response to rotation of the rotatable shaft. In one example, as depicted in <FIG>, the collar <NUM> may be coupled to and/or made integral with the rotor portion 22b via one or more screws <NUM> and/or other suitable connectors.

The one or more sense elements <NUM> may be sensed by the speed sensor <NUM> and signals based on the sensed sense elements <NUM> may be utilized to indicate an axial position of the rotor portion 22b and/or the rotatable shaft <NUM> and/or a rotational speed of the rotor portion 22b and/or the rotatable shaft <NUM>, as discussed in further detail below. The one or more sense elements <NUM> may be configured as slots (as depicted in <FIG>), protrusions, notches, and/or other configurations suitable for being sensed by the sensing module <NUM>. The sense elements <NUM> may be made from any suitable material including, but not limited to, a metal material, a polymer material, a combination of a metal material and a polymer material, and/or other suitable material. In some cases, one or more of the sense elements <NUM> may be similar to one or more other sense elements <NUM> and/or one or more of the sense elements <NUM> may be different than one or more other sense elements <NUM>. In one example of the sense elements <NUM>, the sense elements <NUM> may be formed into the rotor portion 22b (e.g., via the collar <NUM> or other suitable component), as shown in <FIG>. In another example of the sense elements <NUM>, the sense elements <NUM> may be coupled to the rotor portion 22b via a suitable coupling technique including, but not limited to, a screw, a bolt, an adhesive, a weld, a solder connection, a magnetic bond, etc..

As depicted in <FIG>, the dry gas seal <NUM> may include a sensor housing <NUM>. In some cases, the sensing module <NUM> may be entirely or at least partially coupled to components of the dry gas seal <NUM> within the sensor housing <NUM>. Alternatively or in addition, at least part of the sensing module <NUM> may be coupled to other components of the dry gas seal <NUM> without the sensor housing <NUM>. The sensor housing <NUM> may be coupled to and/or secured relative to the stator portion 22a of the dry gas seal <NUM>, such that the components of the sensing module <NUM> (e.g., the speed sensor <NUM>) may sense the sense elements <NUM> rotating in response to rotation of the rotatable shaft. The acoustic emissions sensor <NUM> may be coupled to or relative to the stator portion 22a of the dry gas seal <NUM> such that the acoustic emissions sensor <NUM> may be configured to sense operational conditions of the seal interface. When the sensor housing <NUM> is not included, components of the sensing module <NUM> may be coupled directly to the stator portion 22a of the dry gas seal <NUM>.

Dry gas seals, such as those commonly applied to gas compressors, may include a single, tandem, or double seal arrangement. Although not required, the dry gas seal <NUM> may have a tandem seal assembly, as depicted in <FIG>.

<FIG> is a cross-section view taken along line <NUM>-<NUM> of the illustrative dry gas seal <NUM> shown in <FIG> and having a tandem seal assembly, with the rotatable shaft <NUM> inserted into the opening <NUM>. During operation, gas present in the process cavity <NUM>, may be sealed from a bearing cavity (not shown) and from the environment by two seals, a first seal <NUM> (e.g., an inboard (IB) seal) and a second seal <NUM> (e.g., an outboard (OB) seal) arranged in tandem. The components of the first seal <NUM> and the second seal <NUM> may be preassembled into a cartridge, as shown for example in <FIG>. When positioned to create a seal between a stationary housing and the rotatable shaft <NUM>, the cartridge may include the stator portion 22a (e.g., a stator) associated with the stationary housing <NUM> and the rotor portion 22b (e.g., a rotor) associated with the rotatable shaft <NUM>.

In some cases, the rotor portion 22b may include a sleeve <NUM> having one or more portions that are coupled to the rotatable shaft <NUM> and/or otherwise configured to rotate in response to rotation of the rotatable shaft <NUM>. The sleeve <NUM> may take on one or more of a variety of configurations and may extend axially beyond the second seal <NUM>, but this is not required. In some cases, the sleeve <NUM> may be a single sleeve component. In other cases, the sleeve <NUM> may have a plurality of components or portions. For example, as depicted in <FIG>, the sleeve <NUM> may have a main sleeve 32a, a spacer sleeve 32b, and a locking sleeve 32c.

The first seal <NUM> may form a first seal interface <NUM> (e.g., an IB seal interface) defined between a first mating ring <NUM> (e.g., an IB mating ring) connected to the sleeve <NUM> (e.g., connected to the main sleeve 32a) disposed around the rotatable shaft <NUM> and having a first seal face, and a first primary ring <NUM> (e.g., an IB primary ring) connected to the housing <NUM> by the stator portion 22a and having a second seal face forming the first seal interface <NUM> with the first seal face of the first mating ring <NUM>. The second seal <NUM> may form a second seal interface <NUM> (e.g., an OB seal interface) defined between a second mating ring <NUM> (e.g., an OB mating ring) connected to the sleeve <NUM> (e.g., connected to the spacer sleeve 32b and the locking sleeve 32c) disposed around the rotatable shaft <NUM> and having a first seal face and a second primary ring <NUM> (e.g., an OB primary ring) connected to the housing <NUM> by the stator portion 22a and having a second seal face forming the second seal interface <NUM> with the first seal face of the second mating ring <NUM>.

Each of the first primary ring <NUM> and the second primary ring <NUM> may be axially movable along a direction substantially coaxial or parallel to an axis of rotation of the rotatable shaft <NUM> such that a controlled distance may be maintained along each of the first seal <NUM> and the second seal <NUM>. A spring force may be applied to the first primary ring <NUM> by a first spring <NUM> (e.g., an IB spring). In some cases, the first spring <NUM> may be supported between a first spring carrier <NUM> (e.g., an IB spring carrier) and a first retainer <NUM> (e.g., an IB retainer) of the stator portion 22a of the dry gas seal <NUM>. A spring force may be applied to the second primary ring <NUM> by a second spring (<NUM>) e.g., an OB spring). In some cases, the second spring <NUM> may be supported between a second spring carrier <NUM> (e.g., an OB spring carrier) and a second retainer <NUM> (e.g., an OB retainer) of the stator portion 22a of the dry gas seal <NUM>. Although the first retainer <NUM> and the second retainer <NUM> are depicted in <FIG> as separate components, the first retainer <NUM> and the second retainer <NUM> may be a single component (e.g., a single retainer) that performs the functions of the first retainer <NUM> and the second retainer <NUM>.

As depicted in <FIG>, the first mating ring <NUM> and the second mating ring <NUM> may be configured to rotate with the rotatable shaft <NUM>. The first primary ring <NUM> and the second primary ring <NUM> may be axially adjustable within the stator portion 22a, while also being rotationally fixed relative to the stationary housing <NUM>. The mating rings <NUM> and <NUM>, and the primary rings <NUM> and <NUM>, however, may be configured in different relative configurations including, but not limited to, the primary rings <NUM> and <NUM> rotating with the rotatable shaft <NUM> and the mating rings <NUM> and <NUM> remaining rotationally fixed relative to the primary rings <NUM> and <NUM>. Further, in alternative configurations the dry gas seal <NUM> may have a single seal configuration or a double seal configuration, rather than the tandem seal configuration depicted in the Figures. Further, although the first seal <NUM> refers to the IB seal and the second seal <NUM> refers to the OB seal as described herein, the terms first and second are used for descriptive purposes only and the OB seal may be a first seal and the IB seal may be a second seal.

The arrangement and materials used for these seals can be optimized based on the application, for example, the operating pressures of the gas, as well as the chemical composition of the gas and/or the operating environment of the machine. The radial seals may include O-rings, other composite seal arrangements, such as advanced polymer seals surrounding seal carrier members, or other suitable types of materials for seals.

The dry gas seal <NUM> may further include the sensing module <NUM>, as depicted in <FIG>. As discussed above, in reference to <FIG>, the sensing module <NUM> may be configured to sense one or more parameters related to the dry gas seal <NUM> and/or the rotatable shaft <NUM> via one or more sensors (e.g., the speed sensor <NUM>, the acoustic emissions sensor <NUM> (not depicted in <FIG>), and/or one or more other sensors or other communication components). The sensing module <NUM> may be coupled to and/or coupled relative to the stator portion 22a of the dry gas seal <NUM> and, in some cases, at least a portion of the sensing module <NUM> may be formed as part of the housing of the dry gas seal <NUM>. Alternatively or in addition, it is contemplated that at least part of the sensing module <NUM> may be a separate component in communication with the housing of the dry gas seal and/or may be mounted at a location independent of the housing of the dry gas seal <NUM>. In some cases, the housing <NUM> of the sensing module <NUM> may be secured relative to the housing of the dry gas seal <NUM>.

As discussed with reference to <FIG>, the sensing module <NUM> may include the speed sensor <NUM> to facilitate monitoring the dry gas seal <NUM>. The speed sensor <NUM> may be configured to sense a rotational speed of the rotatable shaft <NUM> by sensing one or more sense elements <NUM> configured to rotate in response to rotation of the rotatable shaft <NUM>. As the one or more sense elements <NUM> rotate past a location of the speed sensor <NUM>, the speed sensor <NUM> may sense each sense element <NUM>, and the sensing module <NUM> may generate a signal, which may be indicative of a speed of the rotatable shaft <NUM> and/or the rotor portion 22b of the dry gas seal <NUM>. When connected to the controller <NUM>, the sensing module <NUM> may output the signal to the controller <NUM>.

When the speed sensor <NUM> includes a Hall Effect sensor, the Hall Effect sensor may be a transducer that varies its output voltage in response to a magnetic field. The Hall Effect sensor depicted in <FIG> may include a magnet <NUM> and a sensor integrated circuit (IC) <NUM> in communication with one or more components on a printed wiring board or printed circuit board (PCB) <NUM> connected to one or more connectors <NUM>. In operation, the Hall Effect sensor may function by providing a voltage across the sensor IC <NUM> and applying a magnetic field to the sensor IC <NUM> with the magnet <NUM>, such that a voltage output from the sensor IC <NUM> depends on the magnetic field. Then, as the sense elements <NUM> pass the speed sensor <NUM>, the magnetic field produced by the magnet <NUM> may be modified and the output voltage of the sensor IC <NUM> may change from an output voltage when a sense element <NUM> is not being sensed. The output voltage from the sensor IC <NUM> may be provided to the PCB <NUM> and the signal may be output from the PCB <NUM> and sent through the connector(s) <NUM> to the controller <NUM> and/or other computing component. Although the Hall Effect sensor of <FIG> is depicted and described, other configurations of Hall Effect sensors and speed sensors <NUM> are contemplated.

Although the controller <NUM> is depicted in <FIG> as being spaced from the housing <NUM> of the sensing module <NUM> by the connectors <NUM>, the controller <NUM> may be incorporated into the sensing module <NUM> and/or connected to the sensing module <NUM> by one or more connectors other than the connectors <NUM>. The connectors <NUM> depicted in <FIG> are schematically depicted and, when included, may be any suitable type of electrical and/or mechanical connectors. Example electrical and/or mechanical connectors include wired connectors, wireless connectors, Bluetooth connectors, USB connectors, USB-c connectors, two-prong connectors, three-prong connectors, HDMIconnectors, and/or other suitable connectors.

As depicted in <FIG>, the speed sensor <NUM>, a portion of the sensing module <NUM>, and the sense elements <NUM> may be mounted adjacent an ambient side of the dry gas seal <NUM> (e.g., as opposed to the process side of the dry gas seal <NUM> adjacent the process cavity <NUM>). Alternatively or in addition, at least a portion of the sensing module <NUM> and/or the sense elements <NUM> may be located at one or more other suitable locations. In one example, the sensing module <NUM> or at least a portion of the sensing module <NUM> and the sense elements <NUM> may be mounted or otherwise positioned at any suitable location relative to one another such that the sensing module <NUM> may be capable of sensing the sense elements <NUM> as the sense elements <NUM> rotate relative to rotation of the rotatable shaft <NUM>. Further, when the sensing module <NUM> includes the acoustic emissions sensor <NUM>, the sensing module <NUM> may be mounted or otherwise positioned at a suitable location for sensing acoustic emissions from the dry gas seal <NUM>. The speed sensor <NUM> and the acoustic emissions sensor <NUM> may be located within the housing <NUM> of the sensing module <NUM> at a single location or within the housing <NUM> of the sensing module <NUM> at spaced apart locations, where the housing <NUM> may comprise a plurality of sub-components spaced from one another and configured to house components of the sensing module <NUM>.

As discussed above, the sensing module <NUM> may comprise the acoustic emissions sensor <NUM>. The acoustic emissions sensor <NUM> may be configured to output a signal to the processor <NUM> indicating an operational condition of the first seal face relative to the second seal face (e.g., an operational condition of the dry gas seal <NUM>). For example, the acoustic emissions sensor <NUM> may be configured to sense sounds made by the dry gas seal <NUM> as the dry gas seal <NUM> changes operational conditions and output a signal that changes as detected sound changes. The operational conditions of the dry gas seal <NUM> may be a lift off of the seal faces (e.g., separation of the seal faces) of the mating rings <NUM>, <NUM> and the primary rings <NUM>, <NUM> during run up of the dry gas seal <NUM> or system to which the dry gas seal <NUM> is applied and/or a touchdown of the seal faces (e.g., contact between the seal faces) of the mating rings <NUM>, <NUM> and the primary rings <NUM>, <NUM> during run down of the dry gas seal <NUM> or system to which the dry gas seal <NUM> is applied. In some cases, the acoustic emissions sensor <NUM> may output a signal indicative of its measurements to the controller <NUM> (e.g., to the processor <NUM> of the controller <NUM> or other suitable processor) for processing.

The acoustic emissions sensor <NUM> may be any suitable type of acoustic emissions sensor that is capable of sensing sound from a seal interface (e.g., the seal interfaces <NUM> and <NUM>) and outputting a signal indicative of a sensed sound. In some cases, the acoustic emissions sensor <NUM> may be configured to output the same signal independent from which seal interface a detected sound is coming from when the dry gas seal <NUM> includes more than one seal interface, such as the first seal interface <NUM> and the second seal interface <NUM>, and/or one or more other suitable seal interfaces. Alternatively or in addition, the acoustic emissions sensor <NUM> may be configured to output different signal values for each seal interface or a group of seal interfaces when the dry gas seal <NUM> includes more than one seal interface. Based, at least in part, on outputs from the acoustic emissions sensor <NUM>, the acoustic emissions sensor <NUM> and/or the controller <NUM> may be utilized to determine the operational conditions of each seal interface <NUM>, <NUM> of the dry gas seal <NUM>.

The controller <NUM> may determine the operational condition of the dry gas seal <NUM> (e.g., the first seal face relative to a second seal face of a seal interface <NUM>, <NUM>) based on the signal from the acoustic emissions sensor <NUM>. Alternatively or in addition, the acoustic emissions sensor <NUM> may be configured to determine the operational condition of the dry gas seal <NUM>. In some cases, the operational condition of the rotatable shaft <NUM> and/or the dry gas seal <NUM> may be determined by comparing an acoustic emissions signal to one or more threshold values. In one example, when the operational conditions of the dry gas seal <NUM> to be determined are a lift off operational condition and a touch down operational condition, the acoustic emissions signal may be compared to a lift off threshold value and a touch down threshold value. If the acoustic emissions signal reaches or goes beyond the lift off threshold value, the controller <NUM> or the acoustic emissions sensor <NUM> may indicate the dry gas seal <NUM> has reached a lift off operational condition (e.g., a first seal face and a second seal face of at least one of the seal interfaces <NUM>, <NUM> have separated). If the acoustic emission signal reaches or goes beyond the touch down threshold value, the controller <NUM> or the acoustic emissions sensor <NUM> may indicate the dry gas seal <NUM> has reached a touch down operational condition (e.g., a first seal face and a second seal face of at least one of the seal interfaces <NUM>, <NUM> have touched).

As discussed in greater detail below, the controller <NUM> may be configured to associate a speed of the rotor portion 22b of the dry gas seal <NUM> or a speed of the rotatable shaft <NUM> with an occurrence of an operational condition of the dry gas seal <NUM>. Further, the controller <NUM> may be configured to store the speed as associated with the occurrence of the operational condition in memory <NUM> and/or other suitable memory. In some cases, the controller <NUM> may be configured to output the speed as associated with the occurrence of the operational condition to one or more other computing systems including, but not limited to, a remote server, a user interface and/or other suitable computing system. Additionally or alternatively, the controller <NUM> may be configured to monitor the speeds associated with occurrences of the operational conditions of the dry gas seal <NUM> to determine an operating condition of the dry gas seal that may be used to monitor a health of the dry gas seal <NUM>, diagnose conditions of the dry gas seal <NUM>, detect anomalous seal operating conditions that may lead to failure or damage of components of the dry gas seal <NUM>, etc..

<FIG> depicts a schematic end view of the collar <NUM> having a plurality of sense elements <NUM> along an outer axial surface of the collar <NUM> and a plurality of holes <NUM> for receiving bolts or screws <NUM> (see <FIG>). The sense elements <NUM> may be disposed on the collar <NUM> such that the sense elements <NUM> are configured to be radially spaced (e.g., with equal spacing between each sense element <NUM> and another sense element <NUM> or non-equal spacing between two consecutive sense elements <NUM> and at least one other set of two sense elements) circumferentially around the rotatable shaft <NUM> when the collar <NUM> is positioned around the rotatable shaft <NUM>. The term "disposed on" an element as used herein may include on top of an element, in an element, formed monolithically with, in, or on the element, and/or coupled with or to the element so as to be in, on, or of the element.

As depicted, the sense elements <NUM> may be slots <NUM> which have a consistent shape along its axial length (e.g., where the axial length is parallel to a center axis of the collar <NUM>). However, the sense elements <NUM> may be protrusions, indents, and/or have one or more other suitable shapes including, but not limited to, hole configurations, circle shapes, trapezoidal shapes, shapes that have a cross-sectional shape having a surface with a depth relative to a sensor (e.g., the speed sensor <NUM> or other suitable sensor) that changes over an axial length of the sense element (e.g., where the depth relative to the sensor that changes may be an axial taper in the surface or other change in depth between the surface and the sensor), shapes with one or more tapered surfaces, etc. Although the sense elements <NUM> in <FIG> are depicted as having a same shape as all other sense elements <NUM>, one or more of the sense elements <NUM> may have a different shape or configuration than at least one other sense element <NUM>.

The dry gas seal <NUM> may include a suitable number of sense elements <NUM> to facilitate sensing accurate rotational speeds of the rotatable shaft <NUM> and/or the rotor portion 22b of the dry gas seal <NUM> at low speeds at which a separation or contact of seal faces forming the seal interfaces <NUM>, <NUM> occurs. Such low speeds of the rotatable shaft <NUM> and/or the rotor portion 22b of the dry gas seal <NUM> may include speeds less than about one thousand (<NUM>,<NUM>) RPMs, lest than about five hundred (<NUM>) RPMs, and/or other suitable similarly low speeds.

Although it may be known to sense speeds of rotatable shafts used in compressors and/or other equipment using a single sense element, such speeds to be sensed are much faster than speeds at which changes in operational conditions of first and second seal faces relative to one another occur. Thus, it has been found that in order to provide accurate speeds measurements at low speeds, a plurality of sense elements may be used to achieve a desired resolution in the speed sensed by the speed sensor <NUM>. For example, when a single sense element is used to sense speeds from about ten thousand (<NUM>,<NUM>) RPMs to about forty thousand (<NUM>,<NUM>) RPMs or higher, which is a typical range of operating speeds of the rotatable shaft <NUM>, the single sense element is sensed within a range of about every <NUM> seconds to about <NUM> seconds over the provided range of sensed speeds. Thus, to achieve a desired latency period between sensed sense elements at low speeds, more than a single sense element is needed. It has been found that two or more sense elements <NUM> that are sensed by the speed sensor <NUM> may provide a speed signal with desirable latency period between sensed sense elements <NUM>. In one example, as depicted in <FIG>, eighteen (<NUM>) sense elements <NUM> are provided. When eighteen (<NUM>) sense elements <NUM> are provided and speed is to be sensed at low speeds within a range from about ten (<NUM>) RPMs to about one thousand (<NUM>,<NUM>) RPMs, there may be a latency period between sensed sense elements <NUM> from about <NUM> seconds to about <NUM> seconds. Although eighteen (<NUM>) sense elements <NUM> are used in the example of <FIG>, other suitable number of sense elements <NUM> may be utilized including, but not limited to, two (<NUM>) sense elements, four (<NUM>) sense elements, six (<NUM>) sense elements, eight (<NUM>) sense elements, ten (<NUM>) sense elements, twelve (<NUM>) sense elements, fifteen (<NUM>) sense elements, eighteen (<NUM>) sense elements, twenty five (<NUM>) sense elements, thirty (<NUM>) sense elements and/or other suitable sense elements. In some cases, a number of sense elements may be selected based, at least in part, on balancing a desire to have a shorter latency period between sensed sense elements <NUM> and a size (e.g., circumference, etc.) of the collar, sleeve, or other component at which the sense elements <NUM> may be positioned.

<FIG> depict various schematic views of sense elements <NUM> disposed on an illustrative collar <NUM>, where the sense elements <NUM> taper in an axial direction. <FIG> is a schematic perspective view of the collar <NUM> with sense elements <NUM> formed from a slot <NUM> and having an axially tapered cross-section (e.g., a cross-sectional shape that changes along an axial length of the sense element <NUM>). <FIG> is an end view of the collar <NUM> depicted in <FIG>. As shown in <FIG> and <FIG>, the collar <NUM> may include fifteen (<NUM>) sense elements <NUM> formed from slots <NUM> with an axially tapered cross-section, but more than fifteen (<NUM>) sense elements <NUM> or less than fifteen (<NUM>) sense elements may be used, as desired. Although the sense elements are shown as being equally radially spaced about a circumference of the collar <NUM> and configured to be similarly disposed around the rotatable shaft <NUM>, this is not required in all cases.

As depicted in <FIG>, one or more of the sense elements <NUM> may include a notch <NUM> or other suitable marking that may be sensed by the speed sensor <NUM>. In some cases, the notch <NUM> may be positioned radially off-centered on the sense element <NUM> (e.g., the notch <NUM> may be at one edge of the slot <NUM> of the sense element <NUM>, as depicted in <FIG>), such that the speed sensor <NUM> may sense the notch <NUM> of the sense element <NUM> and a resulting signal in response to sensing the sense elements <NUM> may be indicative of a direction of rotation (e.g., clockwise or counter clockwise) of the rotatable shaft <NUM> and/or the rotor portion 22b of the dry gas seal <NUM>. For example, when the rotatable shaft <NUM> and/or the rotor portion 22b of the dry gas seal <NUM> is rotating in a first direction, the sensed notch <NUM> may be represented in a signal of speed sensor <NUM> immediately before a represented slot <NUM> of the sense element <NUM> and the sensed notch <NUM> may be represented in a signal of the speed sensor <NUM> immediately after a represented slot <NUM> of the sense element <NUM> when rotating in a second direction that is opposite the first direction.

To facilitate identifying the notch <NUM> within a signal from the speed sensor <NUM> and/or for other suitable purposes, the notch <NUM> may be included in less than all of the sense elements <NUM>. For example, the notch <NUM> may be located in one and only one sense element <NUM>, every other sense element <NUM>, every third sense element <NUM>, ever fourth sense element <NUM>, every fifth sense element <NUM>, every sixth sense element <NUM>, and/or at other suitable intervals or arrangements. As depicted in <FIG>, the notch <NUM> may be located in every fifth sense element <NUM>. In some cases, the notch <NUM> may be located in all of the sense elements <NUM>.

The notch <NUM> may have any suitable size for detection by the speed sensor <NUM> and/or identification within a signal from the speed sensor <NUM>. In some cases, the notch <NUM> may extend a radial distance (e.g., a width) between two adjacent sense elements <NUM> any suitable distance as long as the notch <NUM> is not symmetrical (e.g., is assymetrical) about a radial midway point between the two adjacent sense elements <NUM>. In one example, the notch <NUM> may have a radial distance that is greater than half of a radial distance between the two adjacent sense elements <NUM>, less than half of the radial distance between the two adjacent sense elements <NUM>, or equal to the radial distance between the two adjacent sense elements <NUM>. In one example, the notch <NUM> may extend a radial distance of about six (<NUM>) radial degrees, but this is not required and other radial distances are contemplated. The notch <NUM> may have any suitable depth. In some cases, a depth of the notch <NUM> may be greater than, less than, or equal to a depth of an adjacent (e.g., nearest) sense element <NUM>. The depth of the notch <NUM> may be consistent or vary along a length and/or height of the notch <NUM>.

An ability to detect a direction of rotation of the rotatable shaft <NUM> and/or the rotor portion 22b may facilitate preventing premature seal failure. Typical speed monitors that are used to detect speeds of rotating parts (e.g., rotating parts of turbomachines or other suitable rotating parts) cannot determine if a shaft rotates backwards, particularly at low speeds. With the disclosed system being capable of detecting low speeds and a direction of rotation of the rotatable shaft <NUM> and/or the rotor portion 22b, low speed reverse rotation (e.g., which may be caused by valve or seal leakage) may be detected and identified to prevent or to facilitate preventing premature seal failure by allowing users to address any valve or seal leakage before seal failure.

<FIG> is a schematic cross-sectional view of the collar <NUM> taken along line <NUM>-<NUM> in <FIG>. As depicted in <FIG>, the slot <NUM> of the sense element <NUM> may be axially tapered (e.g., the slot <NUM> may taper in an axial direction). The taper of the slot <NUM> may be tapered at any suitable angle A (e.g., any suitable angle A relative to a plane extending perpendicular to an axis of rotation of the rotor portion 22b, the collar <NUM>, and/or the rotatable shaft <NUM>). In some cases, the taper of the slot <NUM> may be tapered at an angle that facilitates the speed sensor <NUM> outputting a different signal value (e.g., a different voltage amplitude or other suitable signal value type) based on an axial position of the sense element, which in turn may be indicative of a relative axial position of the seal faces forming the seal interfaces <NUM>, <NUM>, as discussed in greater detail below. Example angles for the angle A of the axially tapered slot <NUM> may be an angle from about five (<NUM>) degrees to about eighty five (<NUM>) degrees, from about fifteen (<NUM>) degrees to about seventy five (<NUM>) degrees, from about thirty five (<NUM>) degrees to about sixty five degrees (<NUM>), from about forty five (<NUM>) degrees to about fifty five (<NUM>) degrees, and/or at one or more other suitable angles. In one example, the angle A of the axially tapered slot <NUM> may be at about fifty five (<NUM>) degrees.

<FIG> schematically depicts an enlargement of a portion of the illustrative collar <NUM> that is within circle <NUM> depicted in <FIG>. The enlarged portion of the collar <NUM> in <FIG> provides an example configuration of the notch <NUM>. In the example depicted and as discussed above, the notch <NUM> of the sense element <NUM> may be positioned at the outer most axial and/or radial edge of the slot <NUM>. The notch <NUM> may be sensed by the speed sensor <NUM>, and due at least in part to the position of the notch <NUM>, a direction the rotatable shaft <NUM> and/or the rotor portion 22b of the dry gas seal is rotating may be determined (e.g., by the controller <NUM>) from the signal that is output by the speed sensor <NUM>.

The notch <NUM> may take on any suitable <NUM>-dimensional and/or <NUM>-dimensional shape. As shown in <FIG>, from an end view, the notch <NUM> may have a generally rectangular shape, but this is not required and the notch <NUM>, from an end view, may take on one or more other shapes configured to facilitate detection by the speed sensor <NUM>, facilitate determining a direction of rotation of the rotatable shaft <NUM> and/or the rotor portion 22b of the dry gas seal, facilitate forming the notch <NUM>, and/or facilitate one or more other suitable functions. In some cases, the notch <NUM> may have a different profile and/or configuration than the slots <NUM> of the sense element <NUM> to facilitate identifying sensed notches <NUM> in the signal from the speed sensor <NUM>.

<FIG> is a schematic cross-sectional view of the collar <NUM>, taken along line <NUM>-<NUM> of <FIG>. As depicted in <FIG>, the notch <NUM> of the sense element <NUM> may be axially tapered. The taper of the notch <NUM> may be tapered at any suitable angle B and may have a depth that is offset from a surface of the taper of the slot <NUM> such that the notch <NUM> may be distinguishable from the slot <NUM> based on the signal from the speed sensor <NUM>. The taper of the notch <NUM> may be tapered such that the tapered portion of the notch <NUM> may run generally parallel to the tapered portion of the slot <NUM> (e.g., such that angle A may be about equal to angle B), but this is not required. In some cases, the angle B of the axially tapered notch <NUM> may be an angle from about five (<NUM>) degrees to about eighty five (<NUM>) degrees, from about fifteen (<NUM>) degrees to about seventy five (<NUM>) degrees, from about thirty five (<NUM>) degrees to about sixty five degrees (<NUM>), from forty five (<NUM>) degrees to about fifty five (<NUM>) degrees, and/or at one or more other suitable angles. In one example, the angle B of the axially tapered slot <NUM> may be at about fifty five (<NUM>) degrees.

<FIG> depicts a cross-sectional view of the dry gas seal <NUM> with the rotatable shaft <NUM> inserted within the opening <NUM> of the dry gas seal <NUM> that is similar to the view depicted in <FIG>, but with the sense elements <NUM> located on the sleeve <NUM> (e.g., the locking sleeve 32C, as depicted in <FIG>, but this is not required) of the rotor portion 22b of the dry gas seal <NUM> and with the collar <NUM> omitted. Although the collar <NUM> is omitted from the dry gas seal <NUM> of <FIG>, the collar <NUM> may be included even when the sleeve <NUM> includes one or more sense elements <NUM>.

As depicted in <FIG>, the sleeve <NUM> may extend outward toward an ambient space or away from the process cavity <NUM> such that a portion of the sleeve <NUM> faces the sensing module <NUM> (e.g., faces the sensor IC <NUM>). The sense elements <NUM> in the sleeve <NUM> of the dry gas seal <NUM> may be located at an end of the sleeve <NUM>, similar to how the sense elements <NUM> are depicted in <FIG> as being at a top end of the collar <NUM>, or spaced from the end of the sleeve <NUM> as depicted in <FIG>. Further, the sense elements <NUM> may be formed by the slot <NUM> and/or take on one or more other suitable shapes or configurations. In some cases, the sense element <NUM> within the sleeve <NUM> may take on configurations similar to or different than the configurations of other sense elements <NUM> described herein.

As referred to above, it may be possible to determine an axial position of a portion of the dry gas seal <NUM> (e.g., an axial position of the rotor portion 22b and/or other suitable portion of the dry gas seal <NUM>) and/or axial movement of the dry gas seal <NUM> (e.g., axial movement of the rotor portion 22b relative to the stator portion 22a, and/or movement of one or more other portions of the dry gas seal <NUM>) based, at least in part, on a signal <NUM> from the speed sensor <NUM>. <FIG> depicts a schematic illustrative graph of a signal <NUM> output from the speed sensor <NUM> (e.g., as depicted in schematic form in <FIG>) sensing sense elements <NUM> (e.g., sense elements 44a-44d) with an axial taper similar to the sense elements <NUM> in <FIG>. The graph depicts time on the x-axis and amplitude in voltage (e.g., an amplitude of the signal <NUM> from the speed sensor <NUM>) on the y-axis, from which an axial position and/or movement of the dry gas seal <NUM>, or portions thereof, may be determined (e.g., determined by the speed sensor <NUM>, the controller <NUM>, and/or other computing device). Although an amplitude in voltage of the signal <NUM> is depicted in <FIG>, other measurements of the signal <NUM> may be monitored over time to determine axial positions and/or axial movement of the dry gas seal <NUM>. Such signals <NUM> from the speed sensor <NUM> used to and/or monitoring of the signals <NUM> to determine axial positions and/or movement of the dry gas seal <NUM> (or portions thereof) may be utilized to identify thermal distortion at the seal interface(s) of the dry gas seal <NUM>, lift off and touch down at the seal interface(s) of the dry gas seal <NUM> (assuming movement can be detected at a desired resolution), expected leakage of the dry gas seal <NUM>, when to perform maintenance on the dry gas seal <NUM>, and/or determine one or more other suitable conditions of the dry gas seal <NUM>. It is contemplated that while still capable of being used for the functional purposes discussed herein, graphs of the signal <NUM> may take on one or more other forms based on particular configurations and/or arrangements of the sense elements <NUM> and/or based on possible types of measurements of the signal <NUM>.

In <FIG>, the sense elements <NUM> are depicted as being disposed on, for an example, the collar <NUM> and the collar <NUM> is depicted in two different axial positions representing axial positions of the dry gas seal <NUM> and axial movement of the dry gas seal <NUM>. At a first axial position of the collar <NUM> depicted in <FIG>, the speed sensor <NUM> senses a top or top portion of the tapered slot <NUM> (e.g., at a distance D1 from the speed sensor <NUM>), which is a portion of the sense element <NUM> that is farther away from the speed sensor <NUM> than the bottom of the tapered slot <NUM>. At a second axial position of the collar <NUM> depicted in <FIG>, the speed sensor <NUM> senses a bottom or bottom portion of the tapered slot <NUM> (e.g., at a distance D2 from the speed sensor <NUM>, where the distance D2 is less than the distance D1), which is a portion of the sense element <NUM> that is closer to the speed sensor <NUM> than the top of the tapered slot <NUM>. The tapered nature of the sense element <NUM> (e.g., the tapered slot <NUM>) is shown in a broken line indicating the tapered sense element <NUM> may not actually be viewable from the angle depicted in <FIG>. Additionally, the broken line extending from the speed sensor <NUM> to the sense element <NUM> is shown for illustrative purposes only and a viewable line may or may not actually be used by the speed sensor <NUM> to determine a distance from the speed sensor <NUM> to the sense element <NUM>.

As the speed sensor <NUM> senses the sense elements <NUM> of the collar <NUM> over time, the speed sensor <NUM> outputs the signal <NUM> with amplitudes varying over time based on an axial position of the dry gas seal <NUM>. The signal <NUM> may have an amplitude, A1, as depicted schematically in <FIG> with spikes or pulses 44a' and 44b' in the graph of the signal <NUM>, when the sensor <NUM> senses the sense elements <NUM> (e.g., sense elements 44a, 44b) with the collar <NUM> at the first axial position. When the speed sensor <NUM> senses the sense elements <NUM> (e.g., sense elements 44c, 44d) with the collar <NUM> at the second axial position in <FIG>, the speed sensor <NUM> may output signals <NUM> having an amplitude, A2, as depicted schematically in Figure 11A with spikes or pulses 44c', 44d' in the graph of the signal <NUM>. As depicted in <FIG>, the amplitude, A1, of the signal <NUM> when the sense elements <NUM> (e.g., the sense elements 44a, 44b) are sensed with the collar <NUM> at the first axial position is greater than the amplitude, A2, of the signal <NUM> when the sense elements <NUM> (e.g., the sense elements 44c, 44d) are sensed with the collar <NUM> at the second axial position, where the change in amplitude may be determined to be indicative of an axial position of the rotor portion 22b of the dry gas seal <NUM> (e.g., a position relative to the stator portion 22a or relative to a position of one or more other components of the dry gas seal <NUM>) and/or an amount of axial movement of the rotor portion 22b. Although amplitudes of the signal <NUM> are only depicted in <FIG> for sensed positions of the collar <NUM> at two axial positions, the speed sensor <NUM> may output signals <NUM> with amplitudes at levels less than, greater than, and/or between those depicted in <FIG> for axial positions of the collar <NUM> outside of and/or between the axial positions of the collar <NUM> depicted in <FIG>.

Based, at least in part, on the signals <NUM> from the speed sensor <NUM>, the controller <NUM> (e.g., via the processor <NUM> thereof, program code stored in the memory <NUM>, and/or other suitable computing components) may be able to determine a status or condition of the dry gas seal <NUM> (e.g., the operational condition at a seal interface of the dry gas seal <NUM>, the operating condition of the dry gas seal <NUM>, etc.). In one example, the controller <NUM> may associate speeds of the rotor portion 22a of the dry gas seal <NUM> as sensed by the speed sensor <NUM> or other suitable speed sensor with sensed amplitudes of the signal and compare changes in, trends in, and/or other analyses of amplitudes and/or speeds at various amplitudes of the signal <NUM> over time to determine and/or identify a status or condition of the dry gas seal <NUM>. Alternatively or additionally, the signal 72indicative of sensing the sense elements <NUM> (e.g., the sense elements 44a, 44b, 44c, 44d, etc.) may be considered to be or to include spikes or pulses (e.g., spikes or pulses 44a', 44b', 44c', 44d', etc.) in the signal <NUM> and the controller <NUM> may compare values related to the pulses (e.g., amplitudes of the pulses, widths of the pulses, width of spaces between pulses (e.g., a width of spaces between consecutive pulses), speeds associated with the pulses, etc.) in the signal <NUM> to threshold values or a look up table or enter the values related to the pulses into an algorithm to determine an axial position or an amount of axial movement of the collar <NUM>, the dry gas seal <NUM>, the rotor portion 22a relative to the stator portion 22b, and/or the rotatable shaft <NUM>.

Although the example of determining an axial position and/or axial movement of the dry gas seal <NUM> and/or an operational condition of a first seal face relative to a second seal based at least in part on the output signal <NUM> from the speed sensor <NUM> is provided using the tapered slots <NUM> depicted in <FIG>, an axial position and/or movement of the dry gas seal <NUM> (e.g., the rotor portion 22b relative to the stator portion 22a), or portions thereof, may be determined using any suitable slot configuration that varies vertically and results in the speed sensor <NUM> outputting different signals <NUM> (e.g., signals with different amplitudes, different pulse widths, and/or other suitable differences) as portions of the dry gas seal <NUM> move axially. In one example, an axial position of the dry gas seal <NUM>, or portions thereof, may be determined using a slot <NUM> for a sense element <NUM> that has a curved cross-section, a sense element <NUM> with a circular cross-section, a sense element <NUM> with a trapezoidal cross-section, a sense element <NUM> configured to extend an extended portion or an entirety of a circumference around a rotatable shaft with varying depth at varying axial positions, and/or sense elements <NUM> with other suitable configurations and/or cross-sections.

<FIG> depict additional or alternative configurations of the sense elements <NUM> disposed on a collar <NUM>, along with graphs of the signal <NUM> output at various axial positions of the collar <NUM>. Although <FIG> depict example configurations of sense elements <NUM>, other configurations are contemplated. Although the sense elements <NUM> in <FIG> are disposed on the collar <NUM>, similar or alternative sense elements <NUM> may be disposed on other portions of the rotor portion 22b of the dry gas seal 22and/or may be otherwise disposed to rotate around an axis of rotation of the rotatable shaft <NUM>.

<FIG> depict sense elements <NUM> having circle shapes or configurations (e.g., a shape or configuration having a cross-sectional shape that changes along an axial length of the sense element <NUM>), where some of the sense elements <NUM> have different diameters than other sense elements <NUM>, some of the sense elements <NUM> are axially spaced and/or offset from other sense elements <NUM>, some of the sense elements <NUM> are radially spaced and/or offset from other sense elements <NUM>, some of the sense elements <NUM> are axially and radially spaced and/or offset from other sense elements <NUM>, and all of the sense elements <NUM> have a constant and same depth. <FIG> depicts the speed sensor <NUM> (shown in schematic form in <FIG>) sensing the sense elements <NUM> disposed on the collar <NUM>, where the collar <NUM> is at a first axial position relative to the speed sensor <NUM>. The speed sensor <NUM> may output the signal <NUM> and the pulses depicted in the graph of <FIG> may be indicative of sensing the sense elements <NUM>. As depicted in <FIG>, the pulses in the signal <NUM> take on a pattern that is aligned with the pattern of the sensed sense elements <NUM>, where the pulses have a consistent width that is aligned with a width of the sensed sense elements <NUM>, a consistent width or spacing between pulses that is aligned with a width or spacing of the sensed sense elements <NUM>, and a consistent amplitude, A, (e.g., where the consistent amplitude may be due to the constant and consistent depth of the sense elements <NUM> that are sensed).

<FIG> depicts the speed sensor <NUM> sensing the sense elements <NUM> disposed on the collar <NUM>, where the collar <NUM> is at a second axial position relative to the speed sensor <NUM> and the sense elements <NUM> have a different pattern than the pattern of the sense elements <NUM> at the first axial position of the collar <NUM> relative to the speed sensor <NUM>. The speed sensor <NUM> may output the signal <NUM> and the pulses depicted in the graph of <FIG> may be indicative of sensing an axial position of the sense elements <NUM> at the second axial position of the collar <NUM>. As depicted in <FIG>, the pulses in the signal <NUM> take on a pattern that is aligned with the pattern of the sensed sense elements <NUM>, where the pulses have a consistent width that is aligned with a portion of the sensed sense elements <NUM>, a consistent width or spacing between pulses that is aligned with a width or spacing between the sensed sense elements <NUM>, and a consistent amplitude, A, (e.g., where the consistent amplitude may be due to the constant and consistent depth of the sense elements <NUM> that are sensed).

<FIG> depicts the speed sensor <NUM> sensing the sense elements <NUM> disposed on the collar <NUM>, where the collar <NUM> is at a third vertical position relative to the speed sensor <NUM> and the sense elements <NUM> have a different pattern than the pattern of the sense elements <NUM> at the first axial position and the second axial position of the collar <NUM> relative to the speed sensor <NUM>. The speed sensor <NUM> may output the signal <NUM> and the pulses depicted in the graph of <FIG> may be indicative of sensing an axial position of the sense elements <NUM> at the third axial position of the collar <NUM>. As depicted in <FIG>, the pulses in the signal <NUM> take on a pattern that is consistent with the pattern of the sensed sense elements <NUM>, where the pulses have a width consistent with a portion of the sensed sense elements <NUM> (e.g., where the width of the pulses vary with a width or diameter of the sense elements <NUM>), a consistent width or spacing between pulses that is consistent with a width or spacing between the sensed sense elements <NUM>, and have a consistent amplitude, A, (e.g., where the consistent amplitude may be due to the constant and consistent depth of the sense elements <NUM> that are sensed).

<FIG> and <FIG> depict sense elements <NUM> having a trapezoidal shape or configuration (e.g., a shape or configuration having a cross-sectional shape that changes along an axial length of the sense element <NUM>), where each sense element <NUM> has the same or similar dimensions as the other sense elements <NUM>. <FIG> depicts the speed sensor <NUM> (shown in schematic form in <FIG> and <FIG>) sensing the sense elements <NUM> disposed on the collar <NUM>, where the collar <NUM> is at a first axial position relative to the speed sensor <NUM>. The speed sensor <NUM> may output the signal <NUM> and the pulses (e.g., increases in amplitude of the signal <NUM>) depicted in the graph of <FIG> may be indicative of sensing an axial position of the sense elements <NUM> at the first axial position of the collar <NUM>. As depicted in <FIG>, the pulses in the signal take on a pattern than is consistent with the pattern of the sensed sense elements <NUM>, where the pulses have a consistent width that is aligned with a width of the sensed sense elements <NUM>, a consistent width or spacing between pulses that is aligned with a width or spacing of the sensed sense elements <NUM>, and a consistent amplitude, A, (e.g., the consistent amplitude may be due to the constant and consistent depth of the sense elements <NUM> that are sensed).

<FIG> depicts the speed sensor <NUM> sensing the sense element <NUM> disposed on the collar <NUM>, where the collar <NUM> is at a second axial position relative to the speed sensor <NUM> and the sense elements <NUM> have a different pattern than the pattern of the sense elements <NUM> at the first axial position of the collar <NUM> relative to the speed sensor <NUM>. The speed sensor <NUM> may output the signal <NUM> and the pulses (e.g., increases in amplitude of the signal <NUM>) depicted in the graph of <FIG> may be indicative of sensing an axial position of the sense elements <NUM> at the second axial position of the collar <NUM>. As depicted in <FIG>, the pulses in the signal <NUM> take on a pattern that is consistent with the pattern of the sensed sense elements <NUM>, where the pulses have a consistent width that is aligned with a portion of the sensed sense elements <NUM>, a consistent width or spacing between pulses that is aligned with a width or spacing between the sensed sense elements <NUM>, and a consistent amplitude, A, (e.g., where the consistent amplitude may be due to the constant and consistent depth of the sense elements <NUM> that are sensed).

Similar to as discussed above with respect to <FIG>, the controller <NUM> may monitor the signal <NUM> over time and based on the pattern of the signal <NUM> over time (e.g., as depicted in <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, and/or other pattern of the signal <NUM>), determine an axial position of the sense elements <NUM>, the collar <NUM>, and/or the rotor portion 22b. Based on the axial position of the collar <NUM> (or other portions of the dry gas seal <NUM> on which the sense elements <NUM> are disposed) and/or predetermined associations between an axial position of the collar <NUM> and associated positions of the rotor portion 22b relative to the stator portion 22a, the controller <NUM> may be able to determine a current axial position of the rotor portion 22b relative to the stator portion 22a, determine relative movements of the rotor portion 22b, and/or asses a status or condition of the dry gas seal <NUM>. In one example, the controller <NUM> may compare changes in, trends in, and/or other suitable analyses of pulses or other features of the signal <NUM> over time to determine and/or identify a status or condition of the dry gas seal <NUM>. Alternatively or additionally, the controller <NUM> may compare values of the signal <NUM> (e.g., values related to pulses in or other features of the signal <NUM> including, but not limited to, amplitudes of the pulses, widths of the pulses, width of spaces between pulses, etc.) to predetermined values (e.g., threshold values, values in a look up table, etc.) or may enter the values of the signal <NUM> into an algorithm to determine an axial position or an amount of axial movement of the collar <NUM>, the dry gas seal <NUM>, the rotor portion 22a, and/or the stator portion 22b. The threshold values, the look up tables, and/or the algorithm may be developed or determined off-line during testing of the dry gas seal <NUM> and/or developed, determined, and/or updated in real-time while the dry gas seal <NUM> is on-line and in operation.

<FIG> illustrates an example method <NUM> of operating a dry gas seal monitoring system having a dry gas seal (e.g., the dry gas seal <NUM> and/or other suitable dry gas seal) forming a seal between a housing (e.g., the housing <NUM> and/or other suitable housing) and a rotatable shaft (e.g., the rotatable shaft <NUM> and/or other suitable rotatable shaft). The method <NUM> may include determining <NUM> when one of a separation of a first seal face from a second seal face of the dry gas seal and a contact of the first seal face with the second seal face occurs (e.g., determining an occurrence of an operational condition) and determining <NUM> a rotational speed indicative of a speed of the rotatable shaft. Determining an occurrence of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face may be based, at least in part, on a signal of an acoustic emissions sensor (e.g., the acoustic emissions sensor <NUM> and/or other suitable acoustic emissions sensor), a signal from a speed sensor (e.g., the speed sensor <NUM> and/or other suitable speed sensor sensing a sense element (e.g., the sense element <NUM> or other suitable sense element) rotating with the rotatable shaft), and/or on one or more other suitable signals or parameters. Determining a rotational speed indicative of a speed of the rotatable shaft may be determined based, at least in part, on a signal from the speed sensor and/or other suitable signals or parameters. The signal from the speed sensor may be obtained by sensing a plurality of sense elements rotating with the rotatable shaft.

The method <NUM> may further include associating <NUM> the rotational speed that is determined when there is an occurrence of the operational condition with the respective occurrence of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face, and determining <NUM> an operational condition of the dry gas seal based, at least in part, on the association of the rotational speed with the occurrence of one of or both of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face. Further, in instances when the dry gas seal includes multiple seal interfaces, the operational condition of the dry gas seal may be determined based, at least in part, on an association of the rotational speed with the occurrence of one of or both of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face for one or more of the multiple seal interfaces.

The determined operating condition of the dry gas seal may be any suitable operating condition of the dry gas seal. For example, the determined operating condition may be an indication that the dry gas seal is healthy, unhealthy, needs real-time maintenance, will need maintenance in N units of time, will need maintenance in N cycles of use, needs to be shut down, and/or other suitable conditions relating to the operation of the dry gas seal. Such determining of the operating condition of the dry gas seal may facilitate planning for maintenance and/or down time of a machine or system using the dry gas seal, which will mitigate unexpected shutdown of systems and/or machines.

In some cases, determining an operating condition of the dry gas seal may include monitoring, over time, rotational speeds associated with occurrences of one of or both of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face. To facilitate monitoring speeds over time, a first baseline speed for the separation of the first seal face from the second seal face during run-up may be established and a second baseline speed for the contact of the first seal face with the second seal face during run down may be established. Then, once the baseline values are established the first baseline speed may be compared with the rotational speeds associated with occurrences of the separation of the first seal face from the second seal face and the second baseline speed may be compared with the rotational speeds associated with occurrences of the contact of the first seal face with the second seal face to determine the operating condition of the dry gas seal.

Although baselines may be established and utilized, other methods of monitoring and/or determining operating conditions of the dry gas seal are contemplated. In some cases, monitoring and/or determining operating conditions of the dry gas seal may include comparing speeds at current occurrences of an operational condition of one seal face relative to another seal face to a predetermined threshold value, a rolling average of speeds associated with the N previous occurrences of an operational condition of one seal face relative to another seal face, comparing a delta change in speed between a speed at a current occurrence of an operational condition of one seal face relative to another seal face and a speed at one or more previous occurrences of an operational condition of one seal face relative to another seal face to a threshold value, and/or compare the speeds at occurrences of an operational condition of one seal face relative to another seal face to one or more other suitable value.

As discussed above, occurrences of the separation of the first seal face from the second seal face and/or the contact of the first seal face with the second seal face at seal interfaces (e.g., the first seal interface <NUM>, the second seal interface <NUM>, and/or other suitable seal interfaces) of the dry gas seal occur at low speeds (e.g., speeds of less than one thousand (<NUM>,<NUM>) RPMs) relative to operating speeds of a system (e.g., compressor or other suitable system) to which the dry gas seal may be applied (e.g., speeds within a range from about ten thousand (<NUM>,<NUM>) RPMs to about forty thousand (<NUM>,<NUM>) RPMs or greater). With existing speed sensors configured to sense speeds of the rotatable shaft at operating speeds, it is not possible to obtain an accurate speed of the rotatable shaft and/or a rotor portion (e.g., the rotor portion 22b or other suitable rotor portion) of the dry gas seal at the low speeds at which seal faces of a seal interface initially separate from one another (e.g., lift off) or initially come into contact with one another (e.g., touch down), which typically occur at speeds less than about one thousand (<NUM>,<NUM>) RPMs, and more typically at speeds less than about five hundred (<NUM>) RPMs. As such, existing speed sensors used for sensing operating speeds of rotatable shafts cannot be used to accurately determine speeds that are to be associated with lift off or touch down operational conditions of the seal faces in a manner that allows for adequate monitoring of operating conditions of dry gas seals. The improved dry gas seal monitoring systems and methods discussed herein, however, may facilitate accurately determining speeds to be associated with lift off or touch down operational conditions of the seal faces and thus, facilitate accurately determining an operating condition of the dry gas seal based on the associated speeds in a manner that allows for adequate monitoring of operating conditions of dry gas seals.

Claim 1:
A seal monitoring system (<NUM>) for a dry gas seal assembly, comprising:
a dry gas seal (<NUM>) having a stator portion (22a) with a first seal face and a rotor portion (22b) with a second seal face, the dry gas seal is configured to be positioned between a stationary housing (<NUM>) and a rotatable shaft (<NUM>) with the rotor portion (22b) configured to rotate with the rotatable shaft (<NUM>);
two or more sense elements (<NUM>) configured to rotate with the rotatable shaft (<NUM>);
a sensor (<NUM>) sensing the sense elements (<NUM>) as the sense elements (<NUM>) rotate with the rotatable shaft (<NUM>), the sensor (<NUM>) configured to output a signal based on the sensing of the sense elements (<NUM>);
a processor (<NUM>) configured to receive the signal from the sensor (<NUM>); and
wherein the processor (<NUM>) is configured to determine an axial position of the rotor portion (22b) relative to the stator portion (22a) based on the signal output from the sensor (<NUM>), and wherein the processor (<NUM>) is configured to: determine a rotational speed indicative of a speed of the rotatable shaft (<NUM>) at speeds below one thousand (<NUM>,<NUM>) RPMs based on sensing the two or more sense elements (<NUM>) rotating with the rotatable shaft (<NUM>);
determine when one of a separation of a first seal face and a second seal face and a contact of the first seal face with the second seal face occurs;
associate the rotational speed with an occurrence of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face; and
determine an operating condition of the dry gas seal (<NUM>) based on the rotational speed associated with the occurrence of one of the separation of the first seal face from the second seal face and the contact of the first seal face with the second seal face.