Patent Description:
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.

Such liquid ring pumps are described in <CIT> which describes a method for selective introduction of liquid to the pump and <CIT> which discloses a cavitation protection device comprising a storage tank and seamless tube.

Liquid ring pumps may be used with a non-return valve at or proximate to the inlet of the liquid ring pump. The non-return valve may be configured to permit gas to be pumped into the liquid ring pump, and to prevent or oppose the flow of gas in the opposite direction, i.e. out of the liquid ring pump inlet.

The present inventors have realised that, on start-up (i.e. when the liquid ring pump begin to pump gas after a period of inactivity), the non-return valve can open only relatively slowly, e.g. over several seconds. The present inventors have further realised that this may lead to cavitation occurring within the liquid ring pump at start-up. Cavitation tends to be a significant cause of wear and failure in certain liquid ring pumps, especially those operating at a low-pressure/high-vacuum condition. Also, start-up cavitation can lead to a disturbing noise. Thus, it tends to be desirable to prevents or oppose start-up cavitation in a liquid ring vacuum pump.

The present inventors have further realised that start-up cavitation can be reduced or eliminated by, during start-up of the liquid ring pump, introducing a flow of air into the inlet manifold of the liquid ring pump, after the non-return valve.

In a first aspect, the present invention provides a system as set forth in claim <NUM>.

The controller is configured to open the valve within a first predetermined time period from activation of the liquid ring pump.

The liquid ring pump may further comprise a shaft upon which the impeller is mounted. The system may further comprise a motor configured to drive the shaft. The controller may be configured to activate the liquid ring pump by controlling the motor to rotate the shaft.

The controller is configured to open the valve at least for some time while the non-return valve is closed. The controller may be configured to close the valve a second predetermined time period after opening the valve. The controller may be configured to close the valve in response to determining that the non-return valve is open.

The non-return valve is disposed on the suction line. The gas line may be coupled to the suction line between the non-return valve and an inlet of the liquid ring pump.

The liquid ring pump may comprise an inlet manifold. The non-return valve may be integrated in the inlet manifold. The gas line may be coupled to the inlet manifold between the chamber and the integrated non-return valve in its closed position. The integrated non-return valve may comprises an annular flange defining an opening, and an object movable between a first position and a second position, wherein in the first position the object is located away from the opening so as to not block the opening, and in the second position the object abuts the annular flange so as to block the opening. The gas line may be coupled to the inlet manifold between the annular flange and the chamber.

The system may further comprise a silencer disposed on the gas line.

Also described herein is a liquid ring pump comprising an inlet manifold and a chamber fluidly connected to the inlet manifold. The inlet manifold comprises an integrated non-return valve, and a gas inlet between the integrated non-return valve in its closed position and the chamber.

The integrated non-return valve may comprise an annular flange defining an opening, and an object movable between a first position and a second position, wherein in the first position the object is located away from the opening so as to not block the opening, and in the second position the object abuts the annular flange so as to block the opening. The gas inlet may be between the annular flange and the chamber.

In a further aspect, the present invention provides a control method according to claim <NUM> for controlling a system according to any of the claims <NUM> to <NUM>.

The system accords to any preceding aspect. The method comprises activating the liquid ring pump, and, after activating the liquid ring pump and while the non-return valve is closed, opening the valve such that a gas flows into the liquid ring pump via the gas line.

The method may further comprise, thereafter, closing the valve and opening the non-return valve.

The gas may be air or an inert gas. The valve may be a solenoid valve.

In any of the above aspects, the system may further comprise a pump configured to pump an 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 separator configured to separate operating liquid from the exhaust fluid of 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.

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

In this embodiment, the vacuum system <NUM> comprises a non-return valve <NUM>, a first valve <NUM>, a silencer <NUM>, a liquid ring pump <NUM>, a motor <NUM>, a separator <NUM>, a pump system <NUM>, a heat exchanger <NUM>, and a controller <NUM>.

The facility <NUM> is connected to a gas inlet of the liquid ring pump <NUM> via a suction or vacuum line or pipe <NUM>.

In this embodiment, the non-return valve <NUM> is disposed on the suction line <NUM>. The non-return valve <NUM> is disposed between the facility <NUM> and the liquid ring pump <NUM>.

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

The gas inlet of the liquid ring pump <NUM> is further connected to an air (or gas) pipe <NUM> (which may also be referred to as an air (or gas) line) via which air can be fed into the gas inlet of the liquid ring pump <NUM>. In this embodiment, the air pipe <NUM> is coupled to the suction line <NUM> between the non-return valve <NUM> and the gas inlet of the liquid ring pump <NUM>.

In this embodiment, the non-return valve <NUM> does not prevent or oppose air flow to the liquid ring pump <NUM> via the air pipe <NUM>. The air pipe <NUM> may be considered to by-pass the non-return valve <NUM>.

The first valve <NUM> is disposed on the air pipe <NUM>. The silencer <NUM> is disposed on the air pipe <NUM>. The first valve <NUM> is disposed between the suction line <NUM> and the silencer <NUM>. The silencer <NUM> is disposed between the first valve <NUM> and an inlet of the suction line <NUM>.

The first valve <NUM> may be a solenoid valve.

The silencer <NUM> may also be referred to as a muffler. The silencer <NUM> is an acoustic device configured to reduce the loudness of the sound pressure within the air pipe <NUM> created by the liquid ring pump <NUM> drawing in air through the air pipe <NUM>.

In this embodiment, the liquid ring pump <NUM> is a single-stage liquid ring pump.

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

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

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

During operation of the liquid ring pump <NUM>, the operating liquid is received in the chamber <NUM> via the first operating liquid pipe <NUM>. In some embodiments, operating liquid may additionally be received via the suction line <NUM> via a spray nozzle. Also, the shaft <NUM> is rotated by the motor <NUM>, thereby rotating the impeller <NUM> within the chamber <NUM>. As the impeller <NUM> rotates, the operating liquid in the chamber <NUM> (not shown in the Figures) is forced against the walls of the chamber <NUM> 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 <NUM> from the suction line <NUM> via the gas inlet <NUM> and the gas intake of the chamber <NUM>. This gas flows into the volumes formed between adjacent vanes of the impeller <NUM>. The rotation of the impeller <NUM> compresses the gas contained within the volume as it is moved from the gas intake of the chamber <NUM> to the gas output of the chamber <NUM>, where the compressed gas exits the chamber <NUM>. Compressed gas exiting the chamber <NUM> then exits the liquid ring pump via the gas outlet and the exhaust line <NUM>.

Returning now to the description of <FIG>, the exhaust line <NUM> is coupled between the gas outlet of the liquid ring pump <NUM> and an inlet of the separator <NUM>. The separator <NUM> is connected to the liquid ring pump <NUM> via the exhaust line <NUM> such that exhaust fluid (i.e. compressed gas, which may include water droplets and/or vapour) is received by the separator <NUM>.

The separator <NUM> is configured to separate the exhaust fluid received from the liquid ring pump <NUM> into gas (e.g. air) and the operating liquid. Thus, the separator <NUM> provides for recycling of the operating liquid.

The gas separated from the received exhaust fluid is expelled from the separator <NUM>, and the vacuum system <NUM>, via a system outlet pipe <NUM>.

In this embodiment, the separator <NUM> comprises a further inlet <NUM> via which the separator <NUM> may receive a supply of additional, or "top-up", operating liquid from an operating liquid source (not shown in the Figures). A second valve <NUM> is disposed along the further inlet <NUM>. The second valve <NUM> is configured to control the flow of the additional operating liquid into the separator <NUM> via the further inlet <NUM>. The second valve <NUM> may be a solenoid valve.

The separator <NUM> comprises three operating liquid outlets. A first operating liquid outlet of the separator <NUM> is coupled to the pump system <NUM> via a second operating liquid pipe <NUM> such that operating liquid may flow from the separator <NUM> to the pump system <NUM>. A second operating liquid outlet of the separator <NUM> is coupled to an overflow pipe <NUM>, which provides an outlet for excess operating liquid. A third operating liquid outlet of the separator <NUM> is coupled to a drain or evacuation pipe <NUM>, which provides a line via which the separator can be drained of operating liquid. A third valve <NUM> is disposed along the evacuation pipe <NUM>. The third valve <NUM> 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 <NUM> via the evacuation pipe <NUM>, respectively. The third valve <NUM> may be a solenoid valve.

The separator <NUM> further comprises a level indicator <NUM> which is configured to provide an indication of the amount of operating liquid in the separator <NUM>, e.g. to a human user of the vacuum system <NUM>. The level indicator <NUM> may include, for example, a transparent window through which a user may view a liquid level within a liquid storage tank of the separator <NUM>.

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

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

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

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

The controller <NUM> is connected to the motor <NUM> via the first VFD <NUM> and via a first connection <NUM> such that a control signal for controlling the motor <NUM> may be sent from the controller <NUM> to the motor <NUM>. The first connection <NUM> 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 <NUM> is configured to operate in accordance with the control signal received by it from the controller <NUM>. Control of the motor <NUM> by the controller <NUM> is described in more detail later below with reference to <FIG>.

The controller <NUM> is connected to the pump system <NUM> via the second VFD <NUM> and via a second connection <NUM> such that a control signal for controlling the pump system <NUM> may be sent from the controller <NUM> to the motor of the pump system <NUM>. The second connection <NUM> 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 <NUM> is configured to operate in accordance with the control signal received by it from the controller <NUM>.

The controller <NUM> is further connected to the first valve <NUM> via a third connection <NUM> such that a control signal for controlling the first valve <NUM> may be sent from the controller <NUM> to the first valve <NUM>. The third connection <NUM> 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 <NUM> is configured to operate in accordance with the control signal received by it from the controller <NUM>. Control of the first valve <NUM> by the controller <NUM> is described in more detail later below with reference to <FIG>.

The controller <NUM> may also be connected to the second valve <NUM> and the third valve <NUM> via respective connections (not shown in the Figures) such that a control signals for controlling the second and third valves <NUM>, <NUM> may be sent from the controller <NUM> to the second and third valves <NUM>, <NUM>.

Thus, an embodiment of the vacuum system <NUM> is provided.

Apparatus, including the controller <NUM>, 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 process performable by the vacuum system <NUM> will now be described with reference to <FIG>. It should be noted that certain of the process steps depicted in the flowchart of <FIG> and described below may be omitted or such process steps may be performed in differing order to that presented below and shown in <FIG>. 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> is a process flow chart showing certain steps of an embodiment of a control process implemented by the vacuum system <NUM>.

At step s2, the vacuum system <NUM> is in an initial state. In this embodiment, in the initial state of the vacuum system <NUM>, the liquid ring pump <NUM> is "off" or inactive (i.e. the motor <NUM> is not driving the liquid ring pump <NUM>), the non-return valve <NUM> is closed, and the first valve <NUM> is closed.

In this embodiment, in the initial state, gas pressure inside the chamber <NUM> of the liquid ring pump <NUM> is higher than the gas pressure within the suction line <NUM> and at the facility <NUM>. Gas from inside the chamber <NUM> of the liquid ring pump <NUM> tends to flow back into the suction line <NUM> as a result of the pressure difference. This gas flow tends to close the non-return valve <NUM>, and the pressure difference across the non-return valve <NUM> tends to hold the non-return valve <NUM> in its closed position. In its closed position, the non-return valve <NUM> prevents gas which is inside the chamber <NUM> from flowing from the chamber <NUM> to the facility <NUM> through the suction line <NUM>. The non-return valve <NUM> in its closed position also prevents operating liquid which is inside the chamber <NUM> from flowing from the chamber <NUM> to the facility <NUM> through the suction line <NUM>.

At step s4, the controller <NUM> activates the liquid ring pump <NUM>, i.e. the liquid ring pump <NUM> is "on". The liquid ring pump <NUM> may be activated to meet a demand of the facility <NUM>, e.g. a demand that gas be pumped from the facility <NUM>.

In this embodiment, the controller <NUM> controls, via the first VFD <NUM> and via the first connection <NUM>, the motor <NUM> to drive the liquid ring pump <NUM>. Thus, the motor <NUM> rotates the shaft <NUM>, thus rotating the impeller <NUM> within the chamber <NUM>. The rotation of the impeller <NUM> tends to cause a reduction of gas pressure within the chamber <NUM>. This reduction of gas pressure within the chamber <NUM> tends to be rapid, for example, for example, without bleeding in air via the air pipe <NUM>, gas pressure within the chamber may drop to its operating state (e.g. vacuum pumping state) within about <NUM> seconds.

Although the reduction of gas pressure within the chamber <NUM> caused by activation of the liquid ring pump <NUM> tends to cause the non-return valve <NUM> to open, the non-return valve <NUM> may nevertheless remain closed for some time (e.g. up to ten seconds, or up to five seconds), or open at a slow speed, after the activation of the liquid ring pump <NUM>. This may be caused by, for example, the still existing pressure difference over the non-return valve <NUM>, or by sticking of the non-return valve <NUM>.

At step s6, the controller <NUM> controls, via the third connection <NUM>, the first valve <NUM> to open.

Preferably, the first valve <NUM> is opened at the same time that the liquid ring pump <NUM> is activated. In other words, preferably, steps s4 and s6 are performed substantially simultaneously. Nevertheless, the first valve <NUM> may be opened either before or after the activation of the liquid ring pump <NUM>, e.g. within a predetermined time period of starting up the liquid ring pump <NUM>.

At step s8, the liquid ring pump <NUM> draws air into the chamber <NUM> via its gas inlet <NUM>. Air is drawn into the liquid ring pump <NUM> through the air pipe <NUM>, via the open first valve <NUM> and the silencer <NUM>. Air tends to be drawn into the liquid ring pump <NUM> through the air pipe <NUM> as a result of the reduced gas pressure within the chamber <NUM> caused by activation of the liquid ring pump <NUM>. The silencer <NUM> tends to reduce noise associated with the liquid ring pump <NUM> drawing in air via the air pipe <NUM>.

A rapid drop in pressure within the chamber <NUM> of the liquid ring pump <NUM>, e.g. upon start-up/activation of the liquid ring pump <NUM>, may result in the occurrence of cavitation within the liquid ring pump <NUM> and/or cause the liquid ring pump to make noise. The introduction of air into the liquid ring pump <NUM> at step s8 advantageously tends to slow the pressure drop within the chamber <NUM> upon activation of the liquid ring pump <NUM>. For example, in some embodiments, the introduction of air into the liquid ring pump <NUM> at step s8 may increase the time taken for the gas pressure within the chamber to drop to its operating state (e.g. vacuum pumping state) by about <NUM> second (e.g. from about <NUM> seconds to about <NUM> seconds). Thus, the likelihood of cavitation occurring and/or noise tends to be reduced.

At step s10, the non-return valve <NUM> opens. In this embodiment, the non-return valve <NUM> opens at some time after the activation of the liquid ring pump <NUM> and the opening of the first valve <NUM>. The delay between the activation of the liquid ring pump <NUM> and the full opening of the non-return valve <NUM> may be a relatively short time, e.g. less than or equal to ten seconds, or less than or equal to five seconds. The delay between the activation of the liquid ring pump <NUM> and the full opening of the non-return valve <NUM> may be caused by the non-return valve <NUM> sticking to a valve seat (i.e. being stuck closed), or by the pressure difference across the non-return valve <NUM>.

In this embodiment, the reduced gas pressure within the chamber <NUM> caused by activation of the liquid ring pump <NUM> tends to cause the non-return valve <NUM> to open. In other words, the pressure difference across the non-return valve <NUM> at step s10 tends to open the non-return valve <NUM>. With the non-return valve <NUM> open, the liquid ring pump <NUM> draws gas into the liquid ring pump <NUM> from the facility <NUM>. This flow of gas tends to maintain the non-return valve <NUM> in its open position.

Thus, at step s10 the vacuum system <NUM> may establish a vacuum or low-pressure environment at the facility <NUM> by the liquid ring pump <NUM> drawing gas from the facility <NUM>.

At step s12, the controller <NUM> controls, via the third connection <NUM>, the first valve <NUM> to close, thereby preventing air from flowing into the gas inlet <NUM> via the air pipe <NUM>.

In some embodiments, the first valve <NUM> is closed a predetermined time period after the first valve <NUM> was opened (at step s6). The predetermined time period may be any appropriate time period for example at time period that is less than or equal to <NUM> seconds, or less than or equal to <NUM> seconds, or less than or equal to <NUM> seconds. For example, the predetermined time period may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. This advantageously tends to reduce noise. In some embodiments, a timer (e.g. a countdown timer) may be implemented to open the first valve <NUM> for the predetermined time period.

In some embodiments, the first valve <NUM> is closed responsive to the controller <NUM> detecting or determining that the non-return valve <NUM> is fully open. The non-return valve <NUM> being fully open may be determined or detected by the controller <NUM> using measurements from a sensor that is configured to measure the position or state of the non-return valve <NUM>.

Thus, an embodiment of an anti-cavitation process implemented by the vacuum system <NUM> is provided.

The above described method may be performed automatically, under control of the controller.

The non-return valve advantageously tends to prevent or oppose undesirable back flow of gas and operating liquid, and tends to be particularly beneficial for the liquid ring pump operated using VFD.

In the above embodiments, the vacuum system comprises the elements described above with reference to <FIG>. 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 non-return valve <NUM>, the first valve <NUM>, and the liquid ring pump <NUM> are separate, individual devices. However, in some embodiments, the liquid ring pump may have an integrated non-return valve, e.g. in the inlet manifold of the liquid ring pump. In some embodiments, the liquid ring pump may have an integrated first valve, e.g. in the inlet manifold of the liquid ring pump. In some embodiments, the liquid ring pump may have both an integrated non-return valve and an integrated first valve, e.g. in the inlet manifold of the liquid ring pump.

What will now be described is an embodiment of a liquid ring pump <NUM> comprising an inlet manifold having an integrated non-return valve <NUM>. The first valve <NUM> is coupled to the inlet manifold. For ease of understanding, like reference numerals refer to like elements. The liquid ring pump <NUM> described below with reference to <FIG> may be controlled using the method of <FIG>, described in more detail earlier above.

<FIG> is a schematic illustration (not to scale) showing a cross section of a liquid ring pump <NUM>. The liquid ring pump <NUM> comprises the housing <NUM>, the chamber <NUM>, the shaft <NUM>, the impeller <NUM>, and the gas inlet <NUM> which are arranged as described in more detail earlier above with reference to <FIG>. The gas inlet is connected to the suction line <NUM> (not shown in <FIG>).

In this embodiment, the liquid ring pump <NUM> comprises an inlet manifold <NUM> in which the non-return valve <NUM> is integrated and to which the air pipe <NUM> is attached.

The non-return valve <NUM> comprises an annular flange <NUM> defining a substantially circular opening, a ball <NUM>, and a holder <NUM>.

In this embodiment, the annular flange <NUM> is disposed on an inner side of a wall of the inlet manifold <NUM> at or proximate to the inlet <NUM>. The annular flange <NUM> comprises a chamfered rim circumscribing the opening. The chamfered ring acts as a valve seat. In this embodiment, the annular flange <NUM> is integrally formed with the wall of the inlet manifold <NUM>.

In this embodiment, the ball <NUM> is a substantially spherical object disposed within the inlet manifold <NUM>. The ball <NUM> is movable between a first position in which it is held by the holder <NUM> and is not blocking the opening (i.e. corresponding to an open position of the non-return valve <NUM>), and a second position in which it is in contact with the annular flange <NUM> and is thus blocking the opening (i.e. corresponding to a closed position of the non-return valve <NUM>). Thus, in the first position the ball <NUM> is configured to permit fluid flow through the opening, and in the second position the ball <NUM> is configured to prevent or oppose fluid flow through the opening. In other words, the ball <NUM> is able to act as a plug for the opening.

The holder <NUM> is configured to hold the ball <NUM> when the ball <NUM> is in the first position. In this embodiment, the holder <NUM> comprises two protrusions (e.g. rods). The protrusions extend from an internal surface of the inlet manifold <NUM> into the interior (i.e. a flow channel) of the inlet manifold <NUM>.

The air pipe <NUM> is coupled to an air inlet of the inlet manifold <NUM> located at a point after the annular flange <NUM>, i.e. between the annular flange <NUM> and the chamber <NUM>. Thus, when the ball <NUM> is in its second position in contact with the annular flange <NUM> and is blocking the opening, air (or other gas) can be introduced into the chamber <NUM> via the air pipe <NUM>. The first valve <NUM> is coupled to the air pipe <NUM> at or proximate to the inlet manifold <NUM>.

<FIG> shows the liquid ring pump <NUM> when the vacuum system <NUM> is its initial state, i.e. at step s2 of the process of <FIG>. The non-return valve <NUM> is closed and the first valve <NUM> is closed. In the initial state, gas pressure inside the chamber <NUM> of the liquid ring pump <NUM> is higher than the gas pressure within the suction line <NUM> and at the facility <NUM>. Gas from inside the chamber <NUM> of the liquid ring pump <NUM> tends to flow back into the suction line <NUM> as a result of the pressure difference. This gas flow is indicated in <FIG> by an arrow and the reference numeral <NUM>. This gas flow <NUM> tends to move the ball <NUM> into its second position in contact with the annular flange <NUM>, and to the pressure difference across the ball <NUM> tends to retain the ball <NUM> against the annular flange <NUM>. Thus, the gas inlet <NUM> is blocked by the ball <NUM>.

<FIG> shows the liquid ring pump <NUM> at step s8 of the process of <FIG>. In <FIG>, the liquid ring pump <NUM> has been activated, the first valve <NUM> is open, and the non-return valve <NUM> remains closed. Also, as indicated in <FIG> by arrows and the reference numerals <NUM>, air is drawn into the liquid ring pump <NUM> through the air pipe <NUM> via the open first valve <NUM>. In this embodiment, air <NUM> flows into the chamber <NUM> after, or downstream, of the closed non-return valve <NUM>, i.e. after the annular flange <NUM> and the ball <NUM> in contact therewith.

<FIG> shows the liquid ring pump <NUM> at step s12 of the process of <FIG>. In <FIG>, the liquid ring pump <NUM> is activated, the non-return valve <NUM> is open, and the first valve <NUM> is closed. Also, as indicated in <FIG> by arrows and the reference numerals <NUM>, the liquid ring pump <NUM> draws gas <NUM> into the liquid ring pump <NUM> from the facility <NUM> via the suction line <NUM>. This flow of gas tends to retain the ball <NUM> against the holder <NUM>. The closed first valve <NUM> prevents air from flowing into the inlet manifold <NUM> via the air pipe <NUM>.

Thus, an embodiment of a liquid ring pump comprising an inlet manifold having an integrated non-return valve is provided.

The inlet manifold of the liquid ring pump having an integral or integrated non-return valve advantageously tends to reduce or eliminate use of a separate section of pipe that contains a non-return valve. This avoidance of a separate non-return valve pipe section tends to mean that fewer connections (e.g. joints) are formed between the liquid ring pump and the source of the gas being pumped by the liquid ring pump. This in turn tends to reduce the overall installation height. Also, the risk of leakage tends to be reduced due to the above-mentioned lower number of connections. Thus, efficiency of the liquid ring pump tends to be improved. Also, the material cost associated with the liquid ring pump tends to be reduced, for example because the use of a separate section of pipe containing a non-return valve is reduced or eliminated. Furthermore, the integration of the non-return valve also tends to safeguard against human error during installation of the liquid ring pump at a location.

In addition, a non-return valve integrated in the inlet manifold advantageously tends to restrict flow of gas to a lesser extent than a non-return valve contained in a separate section of pipe.

In the above embodiments, the system comprises a silencer. However, in other embodiments, the silencer is omitted.

In the above embodiments, the air is bled into the liquid ring pump via the air pipe and the first valve. However, in other embodiments, a different gas is introduced into the liquid ring pump. For example, an inert gas, such as nitrogen, may be used. In some embodiments, the fluid (e.g. air) may be introduced into the liquid ring pump at a different location to that described above.

In the above embodiments, the non-return valve does not prevent or oppose air flow to the liquid ring pump via the air pipe. In some embodiments, the non-return valve does not significantly affect airflow to the liquid ring pump via the air pipe, and this air flow is controlled solely via the first valve. However, in other embodiments, the non-return valve may be configured such that, when the non-return valve is in its closed position, the air pipe is open such that air can flow into the liquid ring pump via the air pipe, and such that, when the non-return valve is in its open position, the air pipe is closed by the non-return valve such that air is prevented from flowing into the liquid ring pump via the air pipe.

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, a separator is implemented to recycle the operating liquid back into the liquid ring pump. However, in other embodiments a different type of recycling technique is implemented. The recycling of the operating liquid advantageously tends to reduce operating costs and water usage. Nevertheless, in some embodiments, recycling of the operating liquid is not performed. For example, the vacuum system may include an open loop operating liquid circulation system in which fresh operating liquid is supplied to the liquid ring pump, and expelled operating liquid may be discarded. Thus, the separator may be omitted.

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, e.g. an oil.

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.

Claim 1:
A system (<NUM>) comprising:
a suction line (<NUM>);
a liquid ring pump (<NUM>) coupled to the suction line (<NUM>), the liquid ring pump (<NUM>) comprising a chamber (<NUM>) and an impeller (<NUM>) mounted within the chamber (<NUM>); and
a non-return valve (<NUM>) disposed on the suction line (<NUM>) to permit fluid to flow into the chamber (<NUM>) via the suction line (<NUM>) and to prevent or oppose fluid flow out of the chamber (<NUM>) to the suction line (<NUM>);
a gas line (<NUM>) coupled to the liquid ring pump (<NUM>) such that a gas may flow into the liquid ring pump (<NUM>) via the gas line (<NUM>), the gas line (<NUM>) coupled to the liquid ring pump (<NUM>) between the non-return valve (<NUM>) and the chamber (<NUM>);
a valve (<NUM>) disposed on the gas line (<NUM>); and
a controller (<NUM>) configured to control the valve (<NUM>),
characterised in that the controller (<NUM>) is configured to open the valve (<NUM>) within a first predetermined time period from activation of the liquid ring pump (<NUM>) at least for some time while the non-return valve (<NUM>) is closed.