SEPARATOR SYSTEM

TECHNICAL FIELD

The present disclosure relates to separator systems including separators including, but not limited to, separators for use with liquid ring pumps.

BACKGROUND

Liquid ring pumps are a known type of pump which are typically commercially used as vacuum pumps and as gas compressors. Liquid ring pumps typically include a housing with a chamber therein, a shaft extending into the chamber, an impeller mounted to the shaft, and a drive system such as a motor operably connected to the shaft to drive the shaft. The impeller and shaft are positioned eccentrically within the chamber of the liquid ring pump.

In operation, the chamber is partially filled with an operating liquid (also known as a service liquid). When the drive system drives the shaft and the impeller, a liquid ring is formed on the inner wall of the chamber, thereby providing a seal that isolates individual volumes between adjacent impeller vanes. The impeller and shaft are positioned eccentrically to the liquid ring, which results in a cyclic variation of the volumes enclosed between adjacent vanes of the impeller and the liquid ring.

In a portion of the chamber where the liquid ring is further away from the shaft, there is a larger volume between adjacent impeller vanes which results in a smaller pressure therein. This allows the portion where the liquid ring is further away from the shaft to act as a gas intake zone. In a portion of the chamber where the liquid ring is closer to the shaft, there is a smaller volume between adjacent impeller vanes which results in a larger pressure therein. This allows the portion where the liquid ring is closer to the shaft to act as a gas discharge zone.

Examples of liquid ring pumps include single-stage liquid ring pumps and multi-stage liquid ring pumps. Single-stage liquid ring pumps involve the use of only a single chamber and impeller. Multi-stage liquid ring pumps (e.g. two-stage) involve the use of multiple chambers and impellers connected in series.

It is known to use separators with liquid ring pumps. A separator may be connected to the liquid ring pump such that the separator receives exhaust fluid from the liquid ring pump. The separator separates the received exhaust fluid into gas or vapour (that was pumped by the liquid ring pump) and the operating liquid of the liquid ring pump. This allows for the operating liquid to be recycled, i.e. reused by the liquid ring pump.

SUMMARY

Conventional separators typically include a level indicator or gauge to allow a user to easily check the operating liquid level in the separator. The level indicator may include a tube or pipe connected to a tank of the separator and into which operating liquid from the separator may flow. Conventional separators also typically include a liquid make-up line connection via which new, additional operating liquid can be added to the separator, e.g. to maintain the operating liquid level of the separator at a desired level. The operating liquid added through this connection might be regulated manually or automatically.

In some applications, over time, operating liquid becomes contaminated with particulate matter, dirt, residue, organic contamination, and the like. This tends to be the case where the operating liquid of liquid ring pumps is recycled multiple times, e.g. continuously.

The present inventors have realised that the level indicator tends to get contaminated with residue of particles from the dirty operating liquid therein. Eventually the level indicator may become so dirty that the real liquid level is very hard to ascertain by the user. Furthermore, any operating liquid level sensors associated with the level indicator may be adversely affected by heavily contaminated operating liquids.

The present inventors have further realised that new, clean operating liquid can be added to a separator via the level indicator. This is in contrast to conventional liquid separators in which the liquid make-up line connection is entirely separate of any level indicator. Causing clean operating liquid to flow through the level indicator tends to clean the level indicator and force out any contaminated operating liquid within the level indicator. In other words, clean, “make-up” operating liquid may be flushed through the level indicator to dislodge or remove residue and dirt from the level indicator, while at the same time “topping up” the operating liquid level of the separator.

In a first aspect, the present disclosure provides a separator system comprising: a separator for separating a liquid from a mixture comprising the liquid and another substance; a level indicator coupled to the separator, the level indicator being for indicating a level of the liquid in the separator, the level indicator comprising a tubular member fluidly connected to the separator such that the liquid within the separator may flow from the separator into the tubular member; and a liquid line configured to supply liquid to the separator, the liquid line coupled to the level indicator such that the tubular member is fluidly connected between the liquid line and the separator.

The separator may be configured to separate the liquid from a mixture comprising the liquid and a gas or vapour.

The tubular member may be at least partially transparent (i.e. comprise a transparent portion, at least).

The separator system may further comprise a valve disposed on the liquid line. The separator system may further comprise a controller configured to control the valve. The controller may be configured to open the valve for a first predetermined time period.

The separator system may further comprise a liquid level sensor configured to measure a level of the liquid within a part of the system. The liquid level sensor may be located within the separator or within the level indicator. The controller may be configured to control the valve based on a measurement from the liquid level sensor. The controller may be configured to either deactivate the level sensor or disregard measurements taken by the level sensor for a second predetermined time period after opening the valve.

In a further aspect, the present disclosure provides a system comprising: a liquid ring pump configured to pump, using an operating liquid, a gas or vapour and to output a mixture comprising the operating liquid and the gas or vapour; a separator fluidly arranged to receive the mixture from the liquid ring, the separator being configured to separate the operating liquid from the mixture; a level indicator coupled to the separator, the level indicator being for indicating a level of the operating liquid in the separator, the level indicator comprising a tubular member fluidly connected to the separator such that the operating liquid within the separator may flow from the separator into the tubular member; and an operating liquid make-up line configured to supply new operating liquid to the separator, the operating liquid make-up line coupled to the level indicator such that the tubular member is fluidly connected between the operating liquid make-up line and the separator.

In a further aspect, the present disclosure provides a method for operating a separator system. The separator system comprises a separator for separating a liquid from a mixture comprising the liquid and another substance and a level indicator coupled to the separator. The level indicator is for indicating a level of the liquid in the separator. The level indicator comprises a tubular member fluidly connected to the separator such that the liquid within the separator may flow from the separator into the tubular member. The method comprises causing the liquid to flow into the separator via the tubular member of the level indicator.

The method may further comprise determining that a level of the liquid within the separator is below a threshold liquid level. The step of causing may comprise, responsive to determining that a level of the liquid within the separator is below the threshold liquid level, opening a valve, the valve being disposed along a liquid line for supplying liquid to the separator, the liquid line coupled to the level indicator such that the tubular member is fluidly connected between the liquid line and the separator. The step of determining that a level of the liquid within the separator is below a threshold liquid level may comprise processing, by a controller, a measurement taken by a level sensor configured to measure a liquid level. The step of causing may comprise controlling, by the controller, the valve based on the processing of the measurement.

In a further aspect, the present disclosure provides a system comprising a separator for separating a liquid from a mixture comprising the liquid and another substance, a level gauge coupled to the separator, and a liquid make-up line coupled to the level gauge and configured to supply additional liquid to the separator by causing the liquid to flow through the level gauge.

In any of the above aspects, the system may further comprise a pump configured to pump the operating liquid to the liquid ring pump via an operating liquid line. The controller may be a controller selected from the group of controllers consisting of a proportional controller, an integral controller, a derivative controller, a proportional-integral controller, a proportional-integral-derivative controller, a proportional-derivative controller, and a fuzzy logic controller. The system may further comprise an operating liquid recycling system configured to recycle operating liquid in the exhaust fluid of the liquid ring pump back into the liquid ring pump. The operating liquid recycling system may comprise a cooling means configured to cool the recycled operating liquid prior to the recycled operating liquid being received by the liquid ring pump. The system may further comprise a non-return valve disposed on a suction line of the liquid ring pump. The non-return valve may be configured to permit fluid flow into the liquid ring pump and to oppose fluid flow out of the liquid ring pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration (not to scale) showing a vacuum system.

FIG. 2 is a schematic illustration (not to scale) of a liquid ring pump.

FIG. 3 is a schematic illustration (not to scale) of a separator system.

FIG. 4 is a process flow chart showing certain steps of a process performable by the vacuum system.

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration (not to scale) showing a vacuum system 2. The vacuum system 2 is coupled to a facility 4 such that, in operation, the vacuum system 2 establishes a vacuum or low-pressure environment at the facility 4 by drawing gas (for example, air) from the facility 4.

In this embodiment, the vacuum system 2 comprises a non-return valve 6, a liquid ring pump 10, a motor 12, a separator 14, a pump system 16, a heat exchanger 18, and a controller 20.

The facility 4 is connected to an inlet of the liquid ring pump 10 via a suction or vacuum line or pipe 34.

The non-return valve 6 is disposed on the suction line 34. The non-return valve 6 is disposed between the facility 4 and the liquid ring pump 10.

The non-return valve 6 is configured to permit the flow of fluid (e.g. a gas such as air) from the facility 4 to the liquid ring pump 10, and to prevent or oppose the flow of fluid in the reverse direction, i.e. from the liquid ring pump 10 to the facility 4.

In this embodiment, the liquid ring pump 10 is a single-stage liquid ring pump.

A gas inlet of the liquid ring pump 10 is connected to the suction line 34. A gas outlet of the liquid ring pump 10 is connected to an exhaust line or pipe 38. The liquid ring pump 10 is coupled to the heat exchanger 18 via a first operating liquid pipe 40. The liquid ring pump 10 is configured to receive the operating liquid from the heat exchanger 18 via the first operating liquid pipe 40. The liquid ring pump 10 is driven by the motor 12. Thus, the motor 12 is a driver of the liquid ring pump 10.

FIG. 2 is a schematic illustration (not to scale) of a cross section of an example liquid ring pump 10. The remainder of the vacuum system 2 will be described in more detail later below after a description of the liquid ring pump 10 shown in FIG. 2.

In this embodiment, the liquid ring pump 10 comprises a housing 100 that defines a substantially cylindrical chamber 102, a shaft 104 extending into the chamber 102, and an impeller 106 fixedly mounted to the shaft 104. The gas inlet 108 of the liquid ring pump 10 (which is coupled to the suction line 34) is fluidly connected to a gas intake of the chamber 102. The gas outlet (not shown in FIG. 2) of the liquid ring pump 10 is fluidly connected to a gas output of the chamber 102.

During operation of the liquid ring pump 10, the operating liquid is received in the chamber 102 via the first operating liquid pipe 40. In some embodiments, operating liquid may additionally be received via the suction line 34 via a spray nozzle. Also, the shaft 104 is rotated by the motor 12, thereby rotating the impeller 106 within the chamber 102. As the impeller 106 rotates, the operating liquid in the chamber 102 (not shown in the Figures) is forced against the walls of the chamber 102 thereby to form a liquid ring that seals and isolates individual volumes between adjacent impeller vanes. Also, gas (such as air) is drawn into the chamber 102 from the suction line 34 via the gas inlet 108 and the gas intake of the chamber 102. This gas flows into the volumes formed between adjacent vanes of the impeller 106. The rotation of the impeller 106 compresses the gas contained within the volume as it is moved from the gas intake of the chamber 102 to the gas output of the chamber 102, where the compressed gas exits the chamber 102. Compressed gas exiting the chamber 102 then exits the liquid ring pump via the gas outlet and the exhaust line 38.

Returning now to the description of FIG. 1, the exhaust line 38 is coupled between the gas outlet of the liquid ring pump 10 and an inlet of the separator 14.

The separator 14 is connected to the liquid ring pump 10 via the exhaust line 38 such that exhaust fluid (i.e. compressed gas, which may include water droplets and/or vapour) is received by the separator 14.

FIG. 3 is a schematic illustration (not to scale) showing further details of the separator 14 and its connections in the system 2. The remainder of the vacuum system 2 will be described in more detail later below after a description of the separator 14 and its connections shown in FIG. 3.

The separator 14 may be a vapor-liquid separator or a gas-liquid separator. The separator 14 is configured to separate the exhaust fluid received from the liquid ring pump 10 into gas (e.g. air) and the operating liquid. Thus, the separator 14 provides for recycling of the operating liquid.

The gas separated from the received exhaust fluid is expelled from the separator 14, and the vacuum system 2, via a system outlet pipe 42.

In this embodiment, the separator 14 comprises an operating liquid make-up line 44 via which the separator 14 may receive a supply of additional (i.e. “make-up” or “top-up”) operating liquid from an operating liquid source (not shown in the Figures).

A first valve 45, a T-connector 46, a level indicator (or level gauge) 47, a level sensor 48, and a nozzle 49 are fluid coupled to the operating liquid make-up line 44 such that operating liquid from the operating liquid source may flow into the separator 14 via the operating liquid make-up line 44, the first valve 45, the T-connector 46, the level indicator 47, the level sensor 48, and the nozzle 49.

In particular, in this embodiment, an outlet of the operating liquid make-up line 44 is connected to an inlet of the first valve 45 such that operating liquid from the operating liquid make-up line 44 may flow into the first valve 45. An outlet of the first valve 45 is connected to an inlet of the T-connector 46 such that operating liquid from the first valve 45 may flow into the T-connector 46.

The T-connector 46 is a connector comprising an inlet for receiving operating liquid (i.e. from the first valve 45) and two outlets out of which operating liquid may flow. A first outlet of the T-connector 46 is connected to the level indicator 47 such that operating liquid from the T-connector 46 may flow into the level indicator 47. A second outlet of the T-connector 46 is connected to the nozzle 49 such that operating liquid from the T-connector 46 may flow into the nozzle 49.

In this embodiment, the level indicator 47 is configured to provide an indication of the amount of operating liquid in the separator 14, e.g. to a human user of the vacuum system 2. The level indicator 47 comprises a tube or pipe (i.e. a tubular member) that is fluidly connected to the separator 14 at both of its ends, i.e. at a top and bottom of the level indicator 47. Operating liquid within the separator 14 may freely flow into the level indicator 47 such that the operating liquid levels within the separator 14 and the level indicator 47 are substantially equalised. Thus, an operating liquid level in the level indicator 47 is indicative of (e.g. substantially equal to) an operating liquid level in the separator 14. In this embodiment, the tube or pipe of the level indicator 47 is at least partially transparent such that a user may view a liquid level within the level indicator 47, and thereby ascertain the operating liquid level in the separator 14. For example, the level indicator 47 may include a transparent window, or may be a transparent pipe.

A first end of the level indicator 47 is connected to the first outlet of the T-connector 46 such that operating liquid from the T-connector 46 may flow into the level indicator 47. The level indicator 47 is configured to allow operating liquid received from the T-connector 46 at the first end of the level indicator 47 to flow through the level indicator 47 to a second end of the level indicator 47, which is opposite to the first end of the level indicator 47. In this embodiment, the first end of the level indicator 47 is located above (e.g. directly or vertically above) the second end of the level indicator 47. The second end of the level indicator 47 is connected to the separator 14 such that operating liquid flowing from the first end of the level indicator 47 to the second end of the level indicator 47 may flow out of the second end and into the separator 14.

Furthermore, the level indicator 47 is coupled to the separator such that operating liquid within the separator 14 may flow into the level indicator 47 at the second end of the level indicator 47, and may flow from the second end towards the first end of the level indicator 47. This tends to allow for operating liquid levels within the separator 14 and the level indicator 47 to equalise.

In this embodiment, the level sensor 48 is disposed within the level indicator 47. The level sensor 48 may be a capacitive sensor. The level sensor 48 is configured to measure the operating liquid level within the level indicator 47. More specifically, in this embodiment, the level sensor 48 is positioned within the level indicator 47 at a predetermined position or height corresponding to a desired level for operating liquid within the level indicator 47 (and, thus, the separator 14). The level sensor 48 is configured to detect the presence of operating liquid that is in contact with the level sensor 48. The level sensor 48 detecting the presence of operating liquid at its position within the level indicator 47 corresponds to the operating liquid level within the separator 14 being greater than or equal to a desired level. The level sensor 48 not detecting the presence of operating liquid at its position within the level indicator 47 corresponds to the operating liquid level within the separator 14 being less than the desired level.

The nozzle 49 is connected to the second outlet of the T-connector 46 such that operating liquid from the T-connector 46 may flow into the nozzle 49. In this embodiment, the nozzle 49 is located at least partially within the separator 14. The nozzle 49 is connected to the separator 14 such that operating liquid received by the nozzle 49 from the T-connector 46 may flow out of the nozzle 49 and into the separator 14. In this embodiment, the nozzle 49 is located above the point where the second end of the level indicator 47 connects to the separator 14. In this embodiment, the nozzle 49 may include an orifice or opening that has a smaller diameter than that of the level indicator 47. Thus, fluid flow through the nozzle 49 tends to be restricted compared to fluid flow through the level indicator 47. In other words, the nozzle may provide a so-called restricted orifice. This tends to provide that, when additional (i.e. “make-up) operating liquid is introduced into the separator 14 via the operating liquid make-up line 44, a greater proportion of this operating liquid travels along the level indicator 47, while a lesser proportion travels through the nozzle 49.

Connection between the second outlet of the T-connector 46 and the separator 14, which in this embodiment is provided by the nozzle 49, advantageously tends to facilitate equalisation of operating liquid levels within the separator 14 and the level indicator 47.

Returning now to the description of FIG. 1, the separator 14 comprises three operating liquid outlets. A first operating liquid outlet of the separator 14 is coupled to the pump system 16 via a second operating liquid pipe 56 such that operating liquid may flow from the separator 14 to the pump system 16. A second operating liquid outlet of the separator 14 is coupled to an overflow pipe 50, which provides an outlet for excess operating liquid. A third operating liquid outlet of the separator 14 is coupled to a drain or evacuation pipe 52, which provides a line via which the separator can be drained of operating liquid. A second valve 54 is disposed along the evacuation pipe 52. The second valve 54 is configured to be in either an open or closed state thereby to allow or prevent the flow of the operating liquid out of the separator 14 via the evacuation pipe 52, respectively. The second valve 54 may be a solenoid valve.

In this embodiment, in addition to being coupled to the separator 14 via the second operating liquid pipe 56, the pump system 16 is coupled to the heat exchanger 18 via a third operating liquid pipe 58. The pump system 16 comprises a pump (e.g. a centrifugal pump) and a motor configured to drive that pump. The pump system 16 is configured to pump operating liquid out of the separator 14 via the second operating liquid pipe 56, and to pump that operating liquid to the heat exchanger 18 via the third operating liquid pipe 58.

The heat exchanger 18 is configured to receive relatively hot operating liquid from the pump system 16, to cool that relatively hot operating liquid to provide relatively cool operating liquid, and to output that relatively cool operating liquid.

In this embodiment, the heat exchanger 18 is configured to cool the relatively hot operating liquid flowing through the heat exchanger 18 by transferring heat from that relatively hot operating liquid to a fluid coolant also flowing through the heat exchanger 18. The operating liquid and the coolant are separated in the heat exchanger 18 by a solid wall via which heat is transferred, thereby to prevent mixing of the operating liquid with the coolant. The heat exchanger 18 receives the coolant from a coolant source (not shown in the Figures) via a coolant inlet 60. The heat exchanger 18 expels coolant (to which heat has been transferred) via a coolant outlet 62.

The heat exchanger 18 comprises an operating liquid outlet from which the cooled operating liquid flows (i.e. is pumped by the pump system 16). The operating liquid outlet is coupled to the first operating liquid pipe 40. Thus, the heat exchanger 18 is connected to the liquid ring pump 10 via the first operating liquid pipe 40 such that, in operation, the cooled operating liquid is pumped by the pump system 16 from the heat exchanger 18 to the liquid ring pump 10.

The controller 20 may comprise one or more processors. In this embodiment, the controller 20 comprises two variable frequency drives (VFD), namely a first VFD 201 and a second VFD 202. The first VFD 201 is configured to control the speed of the motor 12. The first VFD 201 may comprise an inverter for controlling the motor 12. The second VFD 202 is configured to control the speed of the motor of the pump system 16. The second VFD 202 may comprise an inverter for controlling the motor of the pump system 16.

The controller 20 is connected to the motor 12 via a first of its VFDs and via a first connection 66 such that a control signal for controlling the motor 12 may be sent from the controller 20 to the motor 12. The first connection 66 may be any appropriate type of connection including, but not limited to, an electrical wire or an optical fibre, or a wireless connection. The motor 12 is configured to operate in accordance with the control signal received by it from the controller 20.

The controller 20 is connected to the pump system 16 via a second of its VFDs and via a second connection 68 such that a control signal for controlling the pump system 16 may be sent from the controller 20 to the motor of the pump system 16. The second connection 68 may be any appropriate type of connection including, but not limited to, an electrical wire or an optical fibre, or a wireless connection. The pump system 16 is configured to operate in accordance with the control signal received by it from the controller 20.

The controller 20 is connected to the first valve 45 via a third connection 70 such that a control signal for controlling the first valve 45 may be sent from the controller 20 to the first valve 45. The third connection 70 may be any appropriate type of connection including, but not limited to, an electrical wire or an optical fibre, or a wireless connection. The first valve 45 is configured to switch between its open and closed state (thereby to allow or prevent the flow of the additional operating liquid into the separator 14, respectively) in accordance with the control signal received by it from the controller 20. Control of the first valve 45 by the controller is described in more detail later below with reference to FIG. 4.

The controller 20 is connected to the level sensor 48 via a fourth connection 72 such that measurements taken by the level sensor 48 may be sent from the level sensor 48 to the controller 20. The fourth connection 72 may be any appropriate type of connection including, but not limited to, an electrical wire or an optical fibre, or a wireless connection.

Thus, an embodiment of the vacuum system 2 is provided.

Apparatus, including the controller 20, for implementing the above arrangement, and performing the method steps to be described later below, may be provided by configuring or adapting any suitable apparatus, for example one or more computers or other processing apparatus or processors, and/or providing additional modules. The apparatus may comprise a computer, a network of computers, or one or more processors, for implementing instructions and using data, including instructions and data in the form of a computer program or plurality of computer programs stored in or on a machine-readable storage medium such as computer memory, a computer disk, ROM, PROM etc., or any combination of these or other storage media.

An embodiment of a control processes performable by the vacuum system 2 will now be described with reference to FIG. 4. It should be noted that certain of the process steps depicted in the flowchart of FIG. 4 and described below may be omitted or such process steps may be performed in differing order to that presented below and shown in FIG. 4. Furthermore, although all the process steps have, for convenience and ease of understanding, been depicted as discrete temporally-sequential steps, nevertheless some of the process steps may in fact be performed simultaneously or at least overlapping to some extent temporally.

FIG. 4 is a process flow chart showing certain steps of an embodiment of a control process implemented by the vacuum system 2.

At step s2, the level sensor 48 measures whether operating liquid is present at the location of the level sensor 48 within the level indicator 47.

At step s4, the level sensor 48 sends, to the controller 20, a signal comprising the measurement taken at step s2. This signal is sent via the fourth connection 72.

At step s6, using the signal received from the level sensor 48, the controller 20 determines whether the operating liquid level within the separator 14 is greater than or equal to the desired level.

In this embodiment, if the measurement received from the level sensor 48 indicates that operating liquid is present at the location of the level sensor 48 within the level indicator 47, then the controller 20 determines that the operating liquid level within the separator 14 is greater than or equal to the desired level.

Also, if the measurement received from the level sensor 48 indicates that operating liquid is not present at the location of the level sensor 48 within the level indicator 47, then the controller 20 determines that the operating liquid level within the separator 14 is less than the desired level.

If, at step s6, the controller 20 determines that the operating liquid level within the separator 14 is greater than or equal to the desired level, the process of FIG. 4 may restart, i.e. proceed to step s2. Thus, the process may be implemented continually or continuously.

However, if, at step s6, the controller 20 determines that the operating liquid level within the separator 14 is less than the desired level, the process of FIG. 4 proceeds to step s8.

At step s8, the controller 20 controls the first valve 45 to open the first valve 45. In particular, the controller 20 sends a control signal for opening the first valve 45 to the first valve 45 via the third connection 70.

At step s10, clean operating liquid flows into the separator 14 from the operating liquid make-up line 44 via, in turn, the open first valve 45, the T-connector 46, and the level indicator 47. Some operating liquid may also flow into the separator 14 from the operating liquid make-up line 44 via, in turn, the open first valve 45, the T-connector 46, and the nozzle 49.

Thus, additional, or “make-up”, operating liquid is introduced or added into the separator 14. This additional operating liquid tends to be relatively clean compared to the relatively dirty operating liquid present in the separator 14 and the level indicator 47, i.e. the additional operating liquid tends to contain less particulate matter, dirt, residue, and other contaminants. Advantageously, the additional clean operating liquid flowing through the level indicator 47 tends to flush the level indicator 47 and remove residue, dirt, particulate matter, and the like from the inside of the level indicator 47. Also, contaminated operating liquid tends to be removed from the level indicator 47. This cleaning of the level indicator 47 advantageously tends to improve the readability by a user. Also, this cleaning of the level indicator 47 advantageously tends to improve operation of the level sensor 48.

In this embodiment, the controller 20 controls the first valve 45 to open for a first predetermined time period. The first predetermined time period may be any appropriate time. For example, the first predetermined time period may be between 1 second and 10 seconds or, more preferably, between 1 second and 5 seconds or, more preferably, about 3 seconds. For example, the first predetermined time period may be 1 s, 2 s, 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, 9 s, or 10 s. In some embodiments, a timer (e.g. a countdown timer) may be implemented by the controller 20 to open the first valve 45 for the first predetermined time period.

Thus, at step s12, responsive to the first predetermined time period elapsing, the the controller 20 controls the first valve 45 to close the first valve 45. In particular, the controller 20 sends a control signal for closing the first valve 45 to the first valve 45 via the third connection 70. Thus, the flow of fresh operating liquid into the separator 14 from the operating liquid make-up line 44 is stopped.

At step s14, the controller 20 disregards measurements received from the level sensor 48 for a second predetermined time period.

The second predetermined time period may be any appropriate time. For example, the second predetermined time period may be between 1 second and 20 seconds or, more preferably, between 5 second and 15 seconds or, more preferably, about 10 seconds. For example, the second predetermined time period may be 1 s, 2 s, 3 s, 4 s, 5 s, 6 s, 7 s, 8 s, 9 s, 10 s, 11 s, 12 s, 13 s, 14 s, 15 s, 16 s, 17 s, 18 s, 19 s, or 20 s. In some embodiments, a timer (e.g. a countdown timer) may be implemented by the controller 20 to disregard measurements received from the level sensor 48 for the second predetermined time period.

The second predetermined time period may start at any appropriate point in time during steps s2 to s12. For example, the second time period may start substantially simultaneously with the opening of the first valve 45 at step s8, or substantially simultaneously with the closing of the first valve 45 at step s12.

The controller 20 disregarding measurements received from the level sensor 48 for the second predetermined time period tends to provide that the controller 20 does not open the first valve 45 during the second predetermined time period. Thus, during the second predetermined time period, the first valve 45 tends to remain closed. Thus, new or “make-up” operating liquid tends not to be introduced into the separator 14 during the second predetermined time period. This tends to allow for operating liquid levels within the separator 14 and the level indicator 47 to properly equalise so that, once the second predetermined time period has elapsed, measurements taken by the level sensor 48 give a true indication of whether the operating liquid level within the separator 14 is greater than or equal to the desired level.

Responsive to the second predetermined time period elapsing, the controller 20 once again begins to process measurements received from the level sensor 48 to determine whether the operating liquid level within the separator 14 is greater than or equal to the desired level. Thus, after step s14, the process of FIG. 4 returns back to step s2 where new operating liquid level measurements are taken and processed, and the first valve 45 is controlled accordingly.

Thus, an embodiment of method of controlling a liquid level is provided. The process of FIG. 4 may be performed continually or continuously during operation of the vacuum system 2.

Advantageously, the above described system and methods tend to provide for automatic cleaning of the level indicator. Also, the above described system and methods tend to provide for automatic topping up of the separator with operating liquid.

The above described system and methods may be performed automatically, under control of the controller.

In the above embodiments, the first valve is automatically controlled by the controller. However, in other embodiments, the first valve is not automatically controlled by the controller. For example, in some embodiments, the first valve is a manual valve which may be controlled by a user. For example, the user may manually control the first valve based on his or her reading of the level indicator.

In the above embodiments, a single level sensor is used. However, in other embodiments, multiple level sensors are used. In some embodiments, the level sensor may be omitted. For example, in some embodiments, a user determines the operating liquid level within the separator using the level indicator and may manually control the first valve based on this determination.

In the above embodiments, the level sensor is located within the level indicator. However, in other embodiments, one or more level sensors are located at a different location instead of or in addition to within the level indicator. For example, one or more level sensors may be located within the separator, e.g. within a tank of the separator. The use of level sensors within the tank of the separator may advantageously tend to facilitate for continuous measurement of the operating liquid level within the tank.

In the above embodiments, the level sensor is configured to detect the presence or otherwise of operating liquid that is in contact with it. However, in other embodiments a different type of level sensor is implemented. In some embodiments, one or more point level sensors are implemented. In some embodiments, one or more continuous level sensors are implemented. Examples of level sensors include, but are not limited to, magnetic and mechanical float sensors, pneumatic sensors, conductive sensors, state dependent frequency monitors, ultrasonic sensors, capacitive sensors, optical interface sensors, microwave sensors, magnetostrictive sensors, resistive chain sensors, magnetoresistive sensors, hydrostatic pressure sensors, air bubblers, and gamma ray sensors.

In the above embodiments, the first valve is opened for the first predetermined time period. Also, in the above embodiments, the controller disregards level measurements for the second time period. However, in other embodiments, the first valve is not opened for the first predetermined time period, and instead the time period for which the first valve is opened may vary. For example, the first valve may be opened until the operating liquid level within the separator is substantially equal to the desired level, e.g. as indicated by the level indicator and/or as measured by the level sensor. Also, in some embodiments, the controller does not disregard level measurements taken by the level sensor.

In the above embodiments, the controller disregards measurements received from the level sensor for the second predetermined time period e.g. after the opening of the valve. However, in other embodiments, the controller does not disregard measurements received from the level sensor. In some embodiments, the controller deactivates the level sensor (i.e. so that no measurements are taken by the level sensor) for the second predetermined time period e.g. after the opening of the valve.

In the above embodiments, a nozzle is connected to the operating liquid make-up line. However, in other embodiments, the nozzle is omitted.

In the above embodiments, the vacuum system comprises the elements described above with reference to FIG. 1. However, in other embodiments the vacuum system comprises other elements instead of or in addition to those described above. Also, in other embodiments, some or all of the elements of the vacuum system may be connected together in a different appropriate way to that described above. For example, in some embodiments, multiple liquid ring pumps may be implemented.

In the above embodiments, the heat exchanger cools the operating liquid flowing therethrough. However, in other embodiments other cooling means are implemented to cool the operating liquid prior to it being received by the liquid ring pump, instead of or in addition to the heat exchanger.

In the above embodiments, the liquid ring pump is a single-stage liquid ring pump. However, in other embodiments the liquid ring pump is a different type of liquid ring pump, for example a multi-stage liquid ring pump.

In the above embodiments, the operating liquid is water. However, in other embodiments, the operating liquid is a different type of operating liquid.

The controller may be a proportional-integral (PI) controller, a proportional (P) controller, an integral (I) controller, a derivative (D) controller, a proportional-derivative (PD) controller, a proportional-integral-derivative controller (PID) controller, a fuzzy logic controller, or any other type of controller.

In the above embodiments, a single controller controls operation of multiple system elements (e.g. the motor). However, in other embodiments multiple controllers may be used, each controlling a respective subset of the group of elements.

In the above embodiments, the pump is controlled to regulate or modulate flow of the operating liquid into the liquid ring pump. However, in other embodiments, one or more different type of regulating device is implemented instead of or in addition to the pump, for example one or more valves for controlling a flow of operating liquid. The controller may be configured to control operation of the one or more regulating devices.

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