Patent Description:
Separator technology is commonly used in wells worldwide, be it a test separator or a production separator. The separators used in sand control completions, for example, are particularly prone to filling with sand. This issue is particularly problematic in relation to off-shore installations where the shut-down of production to clear out a separator can cause significantly delayed production and related financial losses.

Sand separators are also often to protect test or production equipment when large amounts of sand are anticipated as part of the process at hand (hydraulic fracturing, sand control applications, or oil sand applications for example). Prior warning of sand accumulation in a separator is key to minimizing downtime and delayed production, which is typically accomplished via planning and scheduling of routine separator maintenance.

As an example, exploration for methane, or natural gas, involves injection of high-pressure fluids (mostly water with sand) directly into underground rock formations expected to yield natural gas. In hydraulic fracturing procedures, water pressure fractures the rock strata, whereupon entrapped natural gas escapes into a well bore and is captured at the surface. Hydraulic fracturing fluid is recovered from the exploration wells and disposed of, usually by hauling it off in trucks to a remote disposal site. This fluid contains a considerable amount of fracturing sand. The sand is used to help hold open cracks to maximize escape of natural gas from within the strata. Fracturing sand is also used to clean and etch formations so to promote maximum gas delivery. The sand present in fracturing fluid doesn't all remain lodged in the formation, so some returns to the surface in what is called the "flowback" from the well. The flowback fluid includes a significant quantity of injected fracturing sand, as well as silt and rock debris flushed from the rock strata. Such sand and debris can clog or damage pipes, valves, pumps, and other portions of the system. Sand separators prevent these particulates from clogging and damaging the system, but only to the extent that the sand separator is functional. This is merely provided as an example to illustrate one use for sand separators.

In general, a sand separator is used to separate sand or other solids from a liquid/solid mix, and for continued operation of sand separators, a reliable indication of the level of sand in the separator is required. If the sand level is not correctly calculated, there is a risk the sand separator will over-fill. Once over-filled, the typical remedy is to halt the process at hand and manually empty the sand and debris from the separator. Of course, during such corrective actions neither the sand separator nor the production equipment attached thereto is usable, thus facilities incur production down-time and related financial losses.

There is a need for means to eliminate or reduce sand separator clogging. The embodiments described below overcome these and other problems and an advance in the art is achieved. The embodiments described below provide a sand separator that detects the sand level in the collection chamber having a vibratory meter.

Vibratory meters, such as vibratory densitometers and vibratory viscometers, typically operate by detecting motion of a vibrating element that vibrates in the presence of a fluid material to be measured. Documents <CIT>, <CIT> and <CIT> disclose vibratory meters.

Properties associated with the fluid material, such as density, viscosity, temperature, and the like, can be determined by processing measurement signals received from motion transducers associated with the vibrating element. The vibration modes of the vibrating element system generally are affected by the combined mass, stiffness, and damping characteristics of the vibrating element and the surrounding fluid material.

One example of a vibratory density or viscosity meter operates on the vibrating element principle, wherein the element is a slender tuning fork structure which is immersed in the liquid being measured. A conventional tuning fork consists of two tines, typically of flat or circular cross section, that are attached to a cross beam, which is further attached to a mounting structure. The tuning fork is excited into oscillation by a driver, such as a piezo-electric crystal for example, which is internally secured at the root of the first tine. The frequency of oscillation is detected by a second piezo-electric crystal secured at the root of the second tine. The transducer sensor may be driven at its first natural resonant frequency, as modified by the surrounding fluid, by an amplifier circuit located with the meter electronics.

When the fork is immersed in a fluid and excited at its resonant frequency, the fork will move fluid via the motion of its tines. The resonant frequency of the vibration is strongly affected by the density of the fluid these surfaces push against whilst the fluid viscosity has a significant effect on the bandwidth. As the viscosity of the fluid changes, the overall damping forces change, changing the bandwidth and with it the "Q" or quality factor of the sensor. An electronic circuit may excite the sensor into oscillation alternately at two positions on a frequency response curve, and in doing this, the quality factor (Q) of the resonator may be determined as well as the resonant frequency. By measuring certain periods related to the frequency response curve, the viscosity of a fluid can be calculated.

In particular, the viscosity of a fluid can be measured by generating vibration responses at frequencies ω1 and ω2 that are above and below a resonant frequency ω0 of the combined fluid and vibratory sensor. At the resonance frequency ω0, the phase difference Φ0 may be about <NUM> degrees. The two frequency points ω1 and ω2 are defined as the drive frequencies where the drive signal phase and the vibration signal phase differ by the phase differences Φ1 and Φ2, respectively. The phase difference Φ1 may be defined as the point where the phase difference between the drive signal phase and the vibration signal phase is about <NUM> degrees, for example. The phase difference Φ2 may be defined as the point where the phase difference between the drive signal phase and the vibration signal phase is about <NUM> degrees, for example.

The distance between these two frequency points ω1 and ω2 (i.e., the difference in frequency between ω1 and ω2) is used to determine the term Q, which is proportional to viscosity and can be approximated by the formula: <MAT>.

The resonant frequency ω0 is centered between the two frequency points ω1 and ω2. Therefore, the resonant frequency ω0 can be defined as: <MAT>.

The frequency points, ω1 and ω2, are determined during operation when the sensor element interacts with the fluid to be characterized. In order to properly determine the frequency points ω1 and ω2, the drive system uses a closed loop drive, driving the sensor element to alternate between the two phase difference points (Φ1 and Φ2) and recording the vibration frequencies ω1 and ω2 at these points. By using a closed-loop drive, the prior art drive system ensures that the phase difference measurement is stable when the vibration frequencies ω1 and ω2 are determined. This serves as an example of how phase may be used to calculate viscosity by meter electronics.

By orienting a vibratory meter in a sand collection reservoir of a sand separator, and measuring changes in pickoff sensor signal strength and/or signal phase differences, the liquid/solid interface level in a sand separator is rendered detectable, as is disclosed herein.

A sand separator including a separation chamber and a drain is provided according to an embodiment. According to an embodiment, the sand separator comprises a meter in fluid communication with an interior of the separation chamber, wherein the meter is configured to detect a liquid/solid interface. The sand separator further comprises meter electronics in electrical communication with the meter configured to receive a signal from the meter.

A sand separator including a separation chamber and a drain is provided according to an embodiment. According to an embodiment, the sand separator comprises a vibratory fork densitometer in fluid communication with an interior of the separation chamber that is configured to indicate a liquid/solid interface. The sand separator also comprises a vibratory element of the fork densitometer that is configured to vibrate. Additionally, the sand separator comprises a driver configured to receive a driver signal, wherein the driver is further configured to vibrate the vibratory element, and also a pickoff sensor configured to detect a vibration of the vibratory element and generate a pickoff signal that represents the vibration detected. The sand separator further comprises meter electronics in electrical communication with the fork densitometer is configured to provide the driver signal to the driver and receive the pickoff signal from the fork densitometer.

A method of detecting a liquid/solid interface in a sand separator is provided according to an embodiment. According to an embodiment, the method comprises the steps of: vibrating a vibratory element located in a sand separator; measuring a vibrational response of the vibratory element; comparing the vibrational response to a reference value; and detecting a level of the liquid/solid interface in the sand separator.

A method of detecting a liquid/solid interface in a sand separator is provided according to an embodiment. According to an embodiment, the method comprises the steps of: placing a vibratory meter in a sand separator; vibrating a vibratory element of the vibratory meter at a resonant frequency of the vibratory element and fluid surrounding the vibratory element; receiving a signal from a pickoff sensor of the vibratory meter; and detecting a presence of the liquid/solid interface.

According to an aspect, a sand separator including a separation chamber and a drain, comprises:
a vibratory meter in fluid communication with an interior of the separation chamber, wherein the vibratory meter is configured to detect a liquid/solid interface, wherein the vibratory meter comprises:.

Preferably, the vibratory meter is at least one of a densitometer and viscometer.

Preferably, the signal from the vibratory meter is a signal strength of the pickoff sensor.

Preferably, the signal strength is a voltage.

Preferably, the drain is remotely actuatable.

Preferably, the driver comprises a piezoelectric element, and the pickoff sensor comprises a piezoelectric element.

Preferably, the vibratory meter comprises:
a vibratory fork densitometer.

According to an aspect, a method of detecting a liquid/solid interface in a sand separator comprising the steps of:.

Preferably, the fixed phase difference is approximately <NUM>°.

Preferably, the method further comprises the step of indicating when the phase difference between the drive signal and the pickoff signal fluctuates from the fixed phase difference by greater than a predetermined amount.

Preferably, the method further comprises the step of indicating when the vibratory element ceases to vibrate.

Preferably, the method further comprises the step of indicating the presence of the liquid/solid interface in the sand separator if an intensity of the vibrational response is below a predetermined threshold.

Preferably, the intensity comprises a voltage.

Preferably, the method further comprises the step of emptying solids from the sand separator if the liquid/solid interface is detected.

Preferably, the method further comprises the step of opening a drain of the sand separator.

<FIG> and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of embodiments of a sand separator and related methods. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.

<FIG> illustrates a prior art sand separator <NUM>. An inlet port <NUM> allows a liquid/solid mixture to enter the sand separator <NUM> for the purpose of separating the liquid phase from the solid phase of the mixture. Typically, sand, sediment, and debris (collectively "solids") that is carried in water is separated from the water. However, other liquids and solids are contemplated by the present embodiments, and no example provided herein should be considered as limiting the scope of the fluid that can comprise a liquid. The fluid can comprise a gas. Alternatively, the fluid can comprise a multiphase fluid, such as a liquid that includes entrained gas, entrained solids, multiple liquids, or combinations thereof.

The inlet port <NUM> is positioned proximate a top region <NUM> of the separator <NUM> and is offset from a vertical axis such that the mixture enters the separator <NUM> somewhat tangentially so that a circular flow pattern is created inside the separation chamber <NUM>. This flow pattern, through centrifugal forces, causes heavier solids to travel to an inner surface <NUM> of the separation chamber <NUM>. The solids tend to drop towards a bottom region <NUM> of the separator <NUM> and eventually fall into a solids retention region <NUM>. The solids retention region <NUM> is merely a portion of the bottom region <NUM> of the separator <NUM> in this embodiment. In other embodiments, separate chambers for sand collection are contemplated. Liquid that is substantially free of solids is drawn through a conduit <NUM> and exits the separator <NUM> through an outlet port <NUM>. In order to purge accumulated solids, a drain <NUM> is situated proximate the solids chamber <NUM> that can be opened to release these solids. The drain may comprise a valve. As will be apparent to one skilled in the art, if the solids accumulate past a particular level in a particular separator <NUM>, the separator <NUM> may clog, and solids will need to be manually purged in a fashion not in line with flow processes, thereby disrupting such processes.

To detect the liquid/solid interface in a sand separator <NUM>, an embodiment provided utilizes a vibratory meter <NUM>. <FIG> illustrates a vibratory meter <NUM>. A vibratory element <NUM> (typically having a "fork" or "tine" design) is driven to vibrate at a frequency by a driver <NUM>. A pickoff sensor <NUM> with the vibratory element <NUM> detects vibration of the vibratory element <NUM>. Meter electronics <NUM> are connected to the driver <NUM> and pickoff sensor <NUM>. Vibratory meters without forks or tines are also contemplated.

The meter electronics <NUM> may provide electrical power to the vibratory element <NUM> via the lead or leads <NUM>. The leads <NUM> comprise connections for data, power, and the like from a power supply (not shown), meter electronics <NUM>, or other control or computing devices (not shown). The meter electronics <NUM> may control operation of the meter <NUM> and vibratory element <NUM> via the lead or leads <NUM>. For example, the meter electronics <NUM> may generate a drive signal and supply the drive signal to the driver <NUM>, wherein the vibratory element <NUM> is driven to generate a vibration in one or more vibratory components, such as individual tines, using the drive signal. The drive signal may control the vibrational amplitude and/or may control the vibrational frequency. The drive signal may also control the vibrational duration and/or vibrational timing or phase.

The meter electronics <NUM> receives a vibration signal or signals from the vibratory element <NUM> via the lead or leads <NUM>. The meter electronics <NUM> may process the vibration signal or signals in order to generate a density or viscosity measurement, for example. It should be understood that other or additional measurements may be generated from the vibration signal or signals. In one embodiment, the meter electronics <NUM> process the vibration signal or signals received from the vibratory element <NUM> to determine a frequency of the signal or signals. The frequency may comprise a resonant frequency of the vibratory element/fluid, which may be used to determine a density or viscosity of the fluid. In related embodiments, signals from the meter electronics <NUM> are sent to other computing or process devices for processing.

The meter electronics <NUM> may also process the vibration signal or signals to determine other characteristics of the fluid, such as a viscosity or a phase shift between signals that can be processed to determine a fluid flow rate, for example. Other vibrational response characteristics and/or fluid measurements are contemplated and are within the scope of the description and claims, such as the presence of solids suspended in a liquid and the presences of a liquid/solid interface. The meter electronics <NUM> may be further coupled to an interface <NUM>, and the meter electronics <NUM> may communicate signals via this interface <NUM>. The meter electronics <NUM> may process the received vibration signal to generate a measurement value or values and may communicate a measurement value or values via the interface <NUM>. In addition, the meter electronics <NUM> may receive information over the interface <NUM>, such as commands, updates, operational values or operational value changes, and/or programming updates or changes. In addition, the interface <NUM> can enable communications between the meter electronics <NUM> and a remote processing system (not shown). The interface <NUM> is capable of any manner of electronic, optical, or wireless communication, such as for example <NUM>-20ma, HART, RS-<NUM>, Modbus, Fieldbus, and the like, without limitation.

In an embodiment, the driver <NUM> and pickoff sensor <NUM> each comprise piezo-electric crystal elements. The driver <NUM> and pickoff sensor <NUM> are located adjacent to first 122A and second tines 122B of the vibratory element <NUM>. The driver <NUM> and pickoff sensor <NUM> are configured to contact and mechanically interact with the first and second tines 122A, 122B. In particular, the driver <NUM> may contact at least a portion of the first tine 122A. The driver <NUM> expands and contracts when subjected to a drive signal or reference signal provided by meter electronics <NUM>. As a result, the driver <NUM> alternatingly deforms and therefore displaces the first tine 122A from side to side in a vibratory motion (see dashed lines), disturbing the fluid in a periodic, reciprocating manner. Vibration of the second tine causes a corresponding electrical signal to be generated by the pickoff sensor <NUM>. The pickoff sensor <NUM> transmits the vibration signal to the meter electronics <NUM>. The meter electronics <NUM> processes the vibration signal and may measure the vibration signal amplitude and/or the vibration signal frequency of the vibration signal. The meter electronics <NUM> may also compare the phase of the signal from the pickoff sensor <NUM> to a reference phase signal that is provided by the meter electronics <NUM> to the driver <NUM>. Meter electronics <NUM> may also transmit the vibration signal via the interface <NUM>.

The vibratory meter <NUM> is at least partially immersed into a fluid to be characterized. For example, the vibratory meter <NUM> may be mounted in a pipe or conduit. The vibratory meter <NUM> may be mounted in a tank or container or structure for holding a fluid. The vibratory meter <NUM> may be mounted in a manifold or similar structure for directing a fluid flow. In a preferred embodiment, the vibratory sensory is mounted such that the vibratory element <NUM> projects into an interior of a separation chamber <NUM> of a sand separator <NUM>. Other mounting arrangements are contemplated, however, and are within the scope of the description and claims.

<FIG> illustrates an embodiment of a sand separator <NUM> with a meter <NUM> for indicating a liquid/solid interface level. A meter <NUM> is placed on the separation chamber <NUM> such that the portion thereof required to sense the solid/liquid interface is disposed inside the separation chamber <NUM>. In an embodiment, the meter <NUM> is a vibratory meter. In a related embodiment, the meter <NUM> is a vibratory fork densitometer. In this case, a vibratory element <NUM> projects into the separation chamber <NUM> so that tines 122A, 122B of the vibratory element <NUM> are capable of fluid contact.

Liquid enters the inlet port <NUM> of the separator <NUM> in a tangential orientation so that a circular flow pattern is created inside the separation chamber <NUM>. This flow pattern, through centrifugal forces, forces solids against the inner surface <NUM> of the separation chamber <NUM> where the solids tend to drop towards a bottom region <NUM> of the separator <NUM> and eventually fall into a solids retention region <NUM>. A drain <NUM> on the bottom of the separation chamber <NUM> may be opened so that solids are purged from the separator <NUM>. If the level of solids rises too far, the separator <NUM> will clog and be rendered inoperable. In an embodiment, the meter <NUM> is positioned at a position on the separation chamber <NUM> that corresponds to the maximum desired level of the liquid/solid interface. When the liquid/solid interface rises to this level, the meter <NUM> detects the interface.

In an embodiment, the drain <NUM> is remotely actuatable, so that a signal, such as an electric, electronic, pneumatic, hydraulic, or similar signal causes the drain <NUM> to open. In an embodiment, when the liquid/solid interface reaches a predetermined maximum desired level, the meter <NUM> detects this interface through meter electronics <NUM> and communicates with the drain <NUM> such that the drain <NUM> actuates so that at least a portion of the solids content within the separator <NUM> is purged from therein. In particular, meter electronics <NUM> receive a signal from the meter <NUM> that indicates the presence of the liquid/solid interface, and this is processed by the meter electronics <NUM> which sends a signal to the drain <NUM> to open and purge the separator.

In an embodiment, the meter <NUM> is a densitometer, and in a related embodiment, the meter is a vibratory fork densitometer. The densitometer has a vibratory element <NUM> that projects into the separation chamber <NUM>, wherein the vibratory element <NUM> is driven to vibrate by a driver <NUM> and a pickoff sensor <NUM> detects vibrations. In the case of a vibratory fork densitometer, a first tine 122A is driven to vibrate by a driver <NUM> and a second tine 122B transmits vibrations to a pickoff sensor <NUM>. In either case, the meter electronics <NUM> provides a drive or reference signal to the driver <NUM> and receives a signal from the pickoff sensor <NUM> that represents the vibration detected thereby. It is the signal from the pickoff sensor <NUM> that is analyzed by the meter electronics (or relayed to an interface <NUM>) that may be particularly indicative of a liquid/solid interface.

In an embodiment, the meter electronics <NUM> receives a signal from the pickoff sensor <NUM> that indicates the strength of the signal. In an embodiment, the signal strength is measured by a voltage. When the vibratory element <NUM> is immersed in a predominantly liquid phase, the tines 122A, 122B vibrate, and the pickoff sensor <NUM> outputs a voltage of between about 4mV and 20mV, for example without limitation. Other voltages and voltage ranges are contemplated, and nothing herein shall be construed as limiting the voltages to those exemplified. As the liquid/solid interface rises due to solids accumulating in the sand separator <NUM>, the first tine 122A and second tine 122B will increasingly vibrate at a lower intensity, thus the pickoff sensor <NUM> outputs a lower voltage, such as a voltage that is less than 4mV, for example. As the tines 122A, 122B are covered by more and more solids, the output will lower and approach, if not reach, 0mV. As this happens, besides a lowering of the output voltage, an instability in voltage readings is also detectable. The output may also comprise a digital signal. The output may be modified, such as for example, with a calibration coefficient. Meter electronics <NUM> detect the lowered voltage and/or increased instability and signal the sand separator <NUM> to open the drain <NUM>. The threshold voltage for initiating the opening of the drain <NUM> is saved in meter electronics <NUM>, and may be predetermined and set by the factory during production and/or may be user-adjustable. Once the solids are purged, the meter <NUM> outputs a voltage that indicates the presence of a predominantly liquid phase, and controls the drain <NUM> to close. The amount of time the valve <NUM> remains open may be preset, or based on meter <NUM> parameters, or both. In embodiments without automated drain actuation, the meter <NUM> or meter electronics <NUM> alerts a user that the drain <NUM> should be opened or closed.

In another embodiment, a phase difference is utilized to detect the liquid/solid interface. In particular, the meter electronics <NUM> signal the driver <NUM> to cause the vibratory element <NUM> to vibrate. The vibration is at a resonant frequency of the vibratory element in the surrounding medium. If the density or viscosity of the medium changes, so does the resonant frequency and bandwidth. Therefore, the resonant frequency of the vibratory element <NUM> will change as the liquid/solid interface approaches due the percentage of solids in the medium increases with interface level. As the solids cover the vibratory element <NUM>, the vibratory response is altered, and the vibratory element <NUM> may eventually cease to vibrate altogether as it is buried.

Meter electronics <NUM> signal the driver <NUM> to cause the vibratory element <NUM> to vibrate at a particular frequency. The meter electronics <NUM> then detect the signal from the pickoff sensor <NUM>, and maintain a fixed phase difference between the signal from the pickoff sensor <NUM> and the reference signal sent to the driver <NUM> in a closed-loop fashion. In a preferred embodiment, the fixed phase difference is about <NUM>°. Other degrees of phase difference are contemplated, however. While maintaining the phase difference, at least one drive frequency (ω) is measured, and the meter electronics <NUM> may calculate a fluid density and other fluid properties. As the liquid/solid interface rises to contact the vibratory element, the driver <NUM> is unable to be driven at a frequency that maintains a fixed phase difference between the driver signal and pickoff sensor signal, which is due to the solids interfering with the vibratory element <NUM>. This results in the phase difference between the driver signal and pickoff sensor signal becoming unstable at first and to eventually fluctuate away from the fixed point. As the phase difference drifts, meter electronics construe this as the presence of the liquid/solid interface. In an embodiment, when meter electronics <NUM> detect this phase drift, the sand separator <NUM> is signaled to open the drain <NUM>. The threshold phase difference for initiating the opening of the drain <NUM> is saved in meter electronics <NUM>, and may be predetermined and set by the factory during production and/or may be user-adjustable. Once the solids are substantially purged, the meter <NUM> outputs a restored fixed phase difference that indicates the presence of a predominantly liquid phase, and the drain <NUM> is signaled to close. The amount of time the valve <NUM> remains open may be preset, or based on meter <NUM> parameters, or both. In embodiments without automated drain actuation, the meter <NUM> alerts a user that the drain <NUM> should be opened or closed.

<FIG> shows data for a vibratory meter <NUM> installed in a sand separator <NUM> wherein sharp sand is introduced into the separator <NUM>. The sharp sand is introduced into the separator <NUM> at a first point <NUM>. At a second time point <NUM>, the liquid/solid interface is initially detected by the meter <NUM>. The vibratory element <NUM> at this point is interacting with an increasingly greater proportion of sand as the liquid/solid interface rises. The pickoff sensor output <NUM> reflects this by exhibiting a decreasing output voltage. The meter output <NUM> (measured as density in this example) concurrently decreases as a function of the pickoff sensor output <NUM>. At a third time point <NUM>, the vibratory element <NUM> is substantially buried by the sharp sand, and the vibratory element <NUM> is dampened to a point that the pickoff sensor output <NUM> is effectively about 0mv. This, of course, is reflected by the meter output <NUM>, which also declines.

<FIG> shows similar data for a vibratory meter <NUM> installed in a sand separator <NUM> wherein fine sand is introduced into the separator <NUM>. Fine sand is introduced into the separator <NUM> at a first point <NUM>. At a second time point <NUM>, the addition of sand was paused. The vibratory element <NUM> at this point is interacting with a predominantly liquid phase of the liquid/solid mixture in the separator <NUM>. The pickoff sensor output <NUM> reflects this by exhibiting a stable output voltage. The meter output <NUM> (measured as density in this example) concurrently remains stable as a function of the pickoff sensor output <NUM>. At a third time point <NUM>, the addition of sand is resumed, and the liquid/solid interface is initially detected by the meter <NUM>. The vibratory element <NUM> at this point is interacting with an increasingly greater proportion of sand as liquid/solid interface rises. The pickoff sensor output <NUM> reflects this by exhibiting a decreasing output voltage. The meter output <NUM> concurrently decreases as a function of the pickoff sensor output <NUM>. At a fourth time point <NUM>, the vibratory element <NUM> is substantially buried by the sharp sand, and the vibratory element <NUM> is dampened to a point that the pickoff sensor output <NUM> is effectively about 0mv. This, of course, is reflected by the meter output <NUM>, which also declines and exhibits erratic readings.

The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the invention. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the invention. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the invention.

Claim 1:
A sand separator (<NUM>) including a separation chamber (<NUM>) and a drain (<NUM>), comprising:
a vibratory meter (<NUM>) in fluid communication with an interior of the separation chamber (<NUM>), wherein the vibratory meter (<NUM>) is configured to detect a liquid/solid interface, wherein the vibratory meter comprises:
a vibratory element (<NUM>);
a driver (<NUM>) configured to vibrate the vibratory element (<NUM>); and
a pickoff sensor (<NUM>) configured to detect vibration of the vibratory element (<NUM>); and
meter electronics (<NUM>) in electrical communication with the vibratory meter (<NUM>) configured to receive a signal from the vibratory meter (<NUM>),
characterised in that the signal from the vibratory meter (<NUM>) is a phase difference between a driver signal provided to the driver (<NUM>) and a pickoff signal received from the pickoff sensor (<NUM>), and that meter electronics (<NUM>) are configured to indicate when the vibratory meter is unable to maintain the fixed phase difference between the drive signal and the pickoff signal, and that the vibratory meter (<NUM>) is located proximate a level in the separation chamber (<NUM>) that corresponds to a maximum desired level of the liquid/solid interface.