Patent Application
20210372405
This application claims priority to EPO Application No. EP 20177546.7, filed May 29, 2020, the entire contents of which are incorporated herein by reference.
The present invention relates to a vacuum pumping system having a plurality of positive displacement vacuum pumps, and more particularly a plurality of positive displacement vacuum pumps working in parallel. The present invention also relates to a method for operating a vacuum pumping system having a plurality of positive displacement vacuum pumps, and more particularly a plurality of positive displacement vacuum pumps working in parallel and/or connected to vacuum chambers communicating with one another.
Vacuum pumps are used to achieve vacuum conditions, i.e. for evacuating a chamber (so-called “vacuum chamber”) and establishing sub-atmospheric pressure conditions in said chamber. Many different kinds of vacuum pumps, having different structures and operating principles, are known and each time a specific vacuum pump is to be selected according to the needs of a specific application, namely according to the degree of vacuum that is to be attained in the corresponding vacuum chamber.
Positive displacement vacuum pumps displace gas from sealed areas to the atmosphere or to a downstream pumping stage.
Positive displacement pumps are very efficient and cost-effective in generating low vacuum conditions. For this reason, they may be used as main pumps in vacuum systems, but they often serve as fore pumps to other pumps, such as for instance turbomolecular pumps.
Unfortunately, under some circumstances, positive displacement vacuum pumps, such as rotary vane vacuum pumps or scroll pumps, may contaminate the vacuum system in which they are installed.
Rotary vane vacuum pumps can be considered by way of non-limiting example.
A vacuum pumping device 150 comprising a conventional rotary vane vacuum pump 110 and a motor 140 associated therewith is schematically shown in
As shown in
During operation of the vacuum pump 110, gas flows from a vacuum chamber through an inlet port 124 of the pump and passes, through a suction duct 126, into the pumping chamber 116, where it is pushed and thus compressed by vanes 120, and then it is exhausted through an exhaust duct 128 ending at a corresponding outlet port 130.
A proper amount of oil is introduced from an oil tank (not shown) into the outer casing 112 for acting as coolant and lubricating fluid. In the example shown in
In order to drive the rotor 118 of the vacuum pump, the vacuum pumping device 150 further comprises a motor 140 and the pump rotor 118 is mounted to a rotation shaft which is driven by said motor.
As mentioned above, in rotary vane vacuum pumps oil is used for lubricating and cooling the pump moving parts. In this kind of pump oil also acts as a sealant for providing sealing between zones at different pressures.
The presence of oil vapors at the inlet of the vacuum pump entails the risk of backflow and contamination of the vacuum chamber that is being evacuated by the vacuum pump.
Such risk is much higher in vacuum pumping systems in which two or more rotary vane vacuum pumps work in parallel and/or connecting to vacuum chambers communicating with one another.
Indeed, in such complex vacuum pumping systems, if one of the rotary vane vacuum pumps stops due to a failure, the other rotary vane vacuum pump(s) of the vacuum pumping system can suck the oil vapors at the inlet of the vacuum pumps that has stopped. Therefore, the sucked oil passes through the vacuum chamber(s) to which the vacuum pumps are connected and the final effect is that the vacuum pumping system is contaminated.
In order to prevent contamination of the vacuum chamber, a positive displacement vacuum pump, such as a rotary vane vacuum pump can be equipped, with protection devices so as to avoid pressure rises and/or oil backflow towards the vacuum chamber when the pump is switched off. In this way, the vacuum chamber can be completely isolated form the positive displacement vacuum pump.
In case of a vacuum pumping system having a plurality of positive displacement vacuum pumps working in parallel, each positive displacement vacuum pump is equipped with its own protection device, such as an anti-backflow valve, which prevents backflow towards the vacuum chamber, thus suppressing the risk of contamination of the vacuum chamber.
When two or more positive displacement vacuum pumps are connected in parallel to the same vacuum chamber however, the anti-backflow valves fitted on each single pump may lose effectiveness under some particular operating conditions, so that the vacuum chamber becomes exposed to contamination.
In order to avoid the risk of contamination under all circumstances (both during normal operation conditions and fault conditions), it is possible to provide the vacuum pumping with external systems or devices. For instance, isolation valves could be provided for each positive displacement vacuum pump.
However, such solution is not attractive, since it increases the number of components and the complexity of the vacuum pumping system and involves additional costs.
In previous analytical instruments reliant upon vacuum pumping systems and operated by the Applicant (mass spectrometers), multiple vacuum pumps were in common fluid communication with a vacuum chamber of a vacuum pumping system, for instance through a T-connector in common communication with a vacuum port of the vacuum chamber. Contamination of these systems was not known to occur due to vacuum pump failure. The Applicant's recent development work has led to the need for vacuum pumps in separate communication with the vacuum chamber, such that the vacuum chamber forms a fluid path between the vacuum pumps. The inventors unexpectedly discovered a contamination issue with such a system, though the vacuum pumps were being operated in a conventional manner. Accordingly, the inventors identified a need for a system and method for operating a plurality of vacuum pumps in separate communication with a vacuum chamber that reduces a risk of contaminating the vacuum chamber.
An object of the present disclosure is to provide a vacuum pumping system in which the risk of contamination of the vacuum chamber is suppressed, while avoiding the introduction of additional external devices or system.
Another object of the present disclosure is to provide a method for operating a vacuum pumping system which allows to avoid the risk of contamination of the vacuum chamber without implementing any additional external devices or system.
These and other objects may be achieved by the vacuum pumping system and the method for operating a vacuum pumping system as disclosed herein.
To address the foregoing problems, in whole or in part, and/or other problems that may have been observed by persons skilled in the art, the present disclosure provides methods, processes, systems, apparatus, instruments, and/or devices, as described by way of example in implementations set forth below.
The inventors have discovered a potential for contamination of a vacuum chamber of a vacuum pumping system when two or more vacuum pumps are separately connected to the vacuum chamber, i.e. with separate vacuum ports in fluid communication with the vacuum chamber, each vacuum port separately connecting at least one vacuum pump to the vacuum chamber. Under certain pump operation conditions there is a potential for one vacuum pump of the vacuum pumping system to induce a backflow through another vacuum pump so as to draw contaminated gas into the vacuum chamber and accordingly contaminate the vacuum chamber.
The vacuum pumping system according to the invention comprises a plurality of positive displacement vacuum pumps, working in parallel, i.e. intended to be separately connected to the same vacuum chamber, and/or separately connected to vacuum pumping chambers which are in communication with one another.
The vacuum pumping system further comprises a management unit controlling in a synchronized manner all the positive displacement vacuum pumps of the vacuum pumping system. The synchronized manner adjusts operational parameters of the vacuum pumps to avoid conditions where one or more vacuum pumps may backflow into the common vacuum chamber.
More particularly this management unit is configured for:
In embodiments, the management unit may be configured for:
In some aspects, the synchronizing operation may comprise increasing an operational speed of one or more vacuum pumps that are under-pumping relative to the other one or more vacuum pumps. In some aspects, the synchronizing operation may comprise reducing an operational speed of one or more vacuum pumps that are over-pumping relative to the other one or more vacuum pumps. In some aspects, the one or more operational parameters comprises a measurement of pump speed/frequency.
This management unit is further configured for implementing corrective actions in a synchronized way on several positive displacement pumps of the vacuum pumping system (preferably, all said positive displacement vacuum pumps) in case the detected value of one or more identified parameter(s) exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
More particularly, the management unit is further configured for switching off in a synchronized way several positive displacement pumps of the vacuum pumping system (preferably, all said positive displacement vacuum pumps) in case the detected value of one or more identified parameter(s) exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
The management unit may be further configured for triggering an alarm in case the detected value of one or more identified parameter(s) exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
Advantageously, the invention provides for a synchronized management of several positive displacement vacuum pumps of the vacuum pumping system (preferably, all said positive displacement vacuum pumps), so that failure of a single vacuum pump is immediately taken into account by acting not only on the malfunctioning vacuum pump, but also on the other vacuum pumps of the vacuum pumping system, thus effectively preventing any risk of contamination of the vacuum pumping system itself.
The management unit could control all the positive displacement vacuum pumps of the vacuum pumping system simultaneously.
As an alternative, the management unit could control all the positive displacement vacuum pumps of the vacuum pumping system sequentially or according to a predetermined order.
The management unit could control the positive displacement vacuum pumps of the vacuum pumping system continuously.
As an alternative, the management unit could control the positive displacement vacuum pumps of the vacuum pumping system in a discrete manner, at predetermined time intervals.
Advantageously, the management unit of the vacuum pumping system according to the invention allows to check possible risk of contamination of the vacuum pumping system and carry out, if needed, the necessary corrective actions without requiring any modification to the construction of the vacuum pumping system, namely without requiring any additional components such as sensors, vacuum gauges, isolation valves and the like.
As is known, although positive displacement vacuum pumps may be directly connected to a vacuum chamber, they are more frequently used as backing pumps for a high-vacuum vacuum pump, such as a turbomolecular vacuum pump.
Accordingly, the vacuum pumping system according to the invention may further comprise one or more high-vacuum vacuum pumps (e.g. one or more turbomolecular pumps) and the management unit may be configured for controlling said high-vacuum vacuum pumps, with the aim of improving their working life.
For example, in case of a turbomolecular vacuum pump, by checking parameters such as power, frequency and temperature of the bearings it would be possible to predict a failure of the turbomolecular vacuum pump.
In addition, in case of failure of a positive displacement vacuum pump working as backing pump for a turbomolecular vacuum pump, the turbomolecular vacuum pump itself would work under critical conditions. In this scenario, the management unit, by checking the parameters of all the vacuum pumps of the vacuum pumping system in a synchronized way, would be able to immediately switch off the turbomolecular vacuum pump, thus avoiding damages and increasing working life.
In some embodiments of a vacuum pumping system, a management unit may be operative to initiate a start-up sequence that sequentially verifies operation of the vacuum pumps in a synchronized way to confirm identified operating parameters are maintained within an expected threshold or band before increasing pumping speed to induce an operating vacuum in the vacuum chamber of the vacuum pumping system. In some aspects, the vacuum pumping system may include a plurality of groups of one or more vacuum pumps, each of the plurality of groups of one or more vacuum pumps in separate communication with a vacuum chamber of the vacuum pumping system. An anti-suckback valve may separate each of the groups of one or more vacuum pumps from the vacuum chamber. In operation, the management unit may be operative to activate a first group of one or more pumps to operate at a low start up level while the other group(s) of one or more pumps remain inactive. The inactive pumps do not apply suction to their respective backflow valves which results in the backflow valves remaining closed, preventing backflow. The management unit monitors one or more operating parameters of the first group of pumps to identify that the first group of pumps are operating as expected. After confirming expected operation of the first group of pumps, the management unit activates a next group of one or more pumps. The operating parameters of the next group of pumps are set to synchronize operation of the next group of pumps with the previously activated group of pumps to avoid a backflow condition when the backflow valve opens and places the first group of pumps in communication with the second group of pumps. In some aspects, additional groups of pumps may similarly be activated, monitored, and synchronized to avoid the backflow condition.
In some embodiments of a vacuum pumping system, a management unit may be operative to monitor operation of vacuum pumps to confirm their operation in a synchronized way by monitoring operating parameters of the pumps to confirm they are maintained within an expected threshold or band for a given operational state. In some aspects, the vacuum pumping system may include a plurality of groups of one or more vacuum pumps, each of the plurality of groups of one or more vacuum pumps in separate communication with a vacuum chamber of the vacuum pumping system. An anti-suckback valve may separate each of the groups of one or more vacuum pumps from the vacuum chamber. In operation, the management unit may be operative to monitor one or more operating parameters of the pumps to identify that they are operating as expected. When the management unit detects that a pump is operating outside of expected conditions, for instance by detecting that an operational parameter of the pump meets or deviates from an expected threshold value, the management unit is operative to synchronize operation of the pumps to avoid operating conditions of the other pumps that will lead to backflow through one or more of the pumps of the system.
In some aspects, the vacuum chamber may comprise a plurality of vacuum chambers in communication, with at least two of the plurality of groups of pumps in communication with a separate one of the vacuum chambers. The vacuum chambers may be separated from one another, for instance, by a small orifice, relative to the size of the vacuum chambers. In some aspects, one of the vacuum chambers may further be in communication with atmosphere through an orifice. In these aspects, the vacuum chamber in communication with atmosphere is maintained at a higher pressure than the other vacuum chambers. Accordingly, in these aspects, a pressure differential is maintained between the vacuum chamber connected to the first group of pumps and the vacuum chamber connected to the other group of pumps.
Correspondingly, the method for operating a vacuum pumping system comprising a plurality of positive displacement vacuum pumps according to the invention comprises the steps of:
The method further comprises the step of implementing corrective actions in a synchronized way on several positive displacement pumps of the vacuum pumping system (preferably, all said positive displacement vacuum pumps) in case the detected value of one or more identified parameter(s) exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
More particularly, the method preferably comprises the step of switching off in a synchronized way several positive displacement pumps of the vacuum pumping system (preferably, all said positive displacement vacuum pumps) in case the detected value of one or more identified parameter(s) exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
Moreover, the method may further comprise the step of triggering an alarm in case the detected value of one or more identified parameter(s) exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
The detecting and comparing steps could be carried out simultaneously for all the positive displacement vacuum pumps of the vacuum pumping system.
As an alternative, the detecting and comparing steps could be carried out on the positive displacement vacuum pumps of the vacuum pumping system sequentially or according to a predetermined order.
The detecting and comparing steps could be carried out in a continuous manner.
As an alternative, the detecting and comparing steps could be carried out in a discrete manner, at predetermined time intervals.
In some embodiments, a vacuum pumping system is provided. The vacuum pumping system may include at least one mutually communicating vacuum chamber and a plurality of vacuum pumps each separately connected to the at least one vacuum chamber. A management unit may be configured to control operation of the plurality of vacuum pumps and to monitor one or more operating parameters of the plurality of vacuum pumps. Based on the monitoring the management unit may identify, based on the one or more operating parameters, a mismatch in expected pumping between the one or more of the plurality of vacuum pumps. In some aspects, of the vacuum pumping system at least one mutually communicating vacuum chamber comprises a plurality of mutually communicating vacuum chambers, and wherein one of the plurality of vacuum pumps is in separate communication with a first vacuum chamber of the plurality of vacuum chambers and the other of the plurality of vacuum pumps is in separate communication with the other of the plurality of vacuum chambers. In some aspects, at least one of the vacuum chambers is in communication with atmosphere. In some aspects, the management unit may be further operative to activate the plurality of vacuum pumps by: activating a first vacuum pump of the plurality of vacuum pumps, monitoring one or more operating parameters of the first vacuum pump, confirming from the monitoring, that the first vacuum pump is providing expected pumping, such as by operating within an expected pump speed range, and, based on the confirming, activating a second vacuum pump (of the plurality of vacuum pumps; monitoring one or more operating parameters of the first vacuum pump and the second vacuum pump while synchronizing operation of the first vacuum pump and the second vacuum pump to match the expected pump speed of the first vacuum pump and the expected pump speed of the second vacuum pump to prevent backflow from one of the plurality of vacuum pumps into the at least one mutually communicating vacuum chamber.
In the embodiments of vacuum pumping systems or methods described above the one or more operating parameters may, in some embodiments, be selected from the group including: pump speed or frequency, power, current, voltage, and temperature(s) of pump component(s).
According to another embodiment, a mass spectrometry (MS) system includes: a first vacuum chamber for containing a first ion guide configured to receive a plurality of ions generated by an ion source; a first positive displacement pump configured to maintain the first vacuum chamber at a first operating pressure; a second vacuum chamber for containing a second ion guide configured to receive at least a portion of the ions transmitted from the first ion guide, wherein the second vacuum chamber is fluidly coupled to the first vacuum chamber; a second positive displacement pump configured to maintain the second vacuum chamber at a second operating pressure that is lower than the first operating pressure; and a controller, operably connected to the first and second positive displacement pumps, wherein the controller is configured to: monitor one or more operating parameters of the first and second positive displacement pumps; and identify, based on the one or more operating parameters, a mismatch in expected pumping between the first and second positive displacement vacuum pumps.
In an embodiment, the controller is further configured to: identify one or more operating parameters of the first and second positive displacement vacuum pumps related to a risk of contamination of the first and second vacuum chambers by one or more of the first and second positive displacement vacuum pumps; set a threshold value or condition for each of the identified operating parameters; detect the identified operating parameters for each of the first and second positive displacement vacuum pumps; compare, for each of the first and second positive displacement vacuum pumps, the detected values or conditions of the identified parameters with the corresponding threshold values or conditions; and if the detected value of one or more identified operating parameter(s) of one of the first and second positive displacement vacuum pumps exceeds the corresponding threshold value or the detected condition of one or more identified operating parameter(s) of one of the first and second positive displacement vacuum pumps is not consistent with the corresponding threshold condition, acting in a synchronized way on the other of the first and second positive displacement vacuum pumps.
In an embodiment, the second vacuum chamber is fluidly coupled to the first vacuum chamber via an aperture in an exit lens of the first vacuum chamber.
In an embodiment, the second positive displacement pump is further configured to back a first turbomolecular pump for maintaining a third vacuum chamber at a third operating pressure that is lower than the second operating pressure, the third vacuum chamber for containing at least a third ion guide.
In an embodiment, the second positive displacement pump is further configured to back a second turbomolecular pump for maintaining a fourth vacuum chamber at a fourth operating pressure that is lower than the third operating pressure, the fourth vacuum chamber for containing at least one mass analyzer.
In an embodiment, the first operating pressure is in a range from about 1 Torr to about 100 Torr, and optionally, wherein the second operating pressure is in a range from about 500 mTorr to about 5 Torr, and further optionally, wherein the third operating pressure is less than about 100 mTorr, and further optionally, wherein the fourth operating pressure is less than about 1×10−4 Torr.
According to another embodiment, a method of operating a vacuum system for a mass spectrometry (MS) system includes: monitoring one or more operating parameters of a first positive displacement pump configured to maintain a first vacuum chamber at a first operating pressure, wherein the first vacuum chamber contains a first ion guide configured to receive a plurality of ions generated by an ion source; monitoring one or more operating parameters of a second positive displacement pump configured to maintain a second vacuum chamber at a second operating pressure, wherein the second vacuum chamber contains a second ion guide configured to receive at least a portion of the ions transmitted from the first ion guide; and identifying, based on the one or more operating parameters of the first and second positive displacement pumps, a mismatch in expected pumping between the first and second positive displacement vacuum pumps.
In an embodiment, the method further includes: identifying the one or more operating parameters of the first and second positive displacement vacuum pumps related to a risk of contamination of the first and second vacuum chambers by one or more of the first and second positive displacement vacuum pumps; setting a threshold value or condition for each of the identified parameters; detecting the identified parameters for each of the first and second positive displacement vacuum pumps; comparing, for each of the first and second positive displacement vacuum pumps, the detected values or conditions of the identified parameters with the corresponding threshold values or conditions; and if the detected value of one or more identified parameter(s) of one of the first and second positive displacement vacuum pumps exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) of one of the first and second positive displacement vacuum pumps is not consistent with the corresponding threshold condition, acting in a synchronized way on the other of the first and second positive displacement vacuum pumps.
Other devices, apparatus, systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims.
The invention can be better understood by referring to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.
The invention can be advantageously applied to vacuum pumping systems including two or more positive displacement pumps working in parallel and/or connected to vacuum chambers which are mutually communicating.
Nevertheless, it shall be understood that the invention could be applied to vacuum pumping systems comprising a plurality of positive displacement vacuum pumps of any kind and structure, and possibly further comprising one or more high-vacuum vacuum pumps of any kind and structure.
In the exemplary vacuum pumping systems of
It will be evident to the person skilled in the art that, in all the shown embodiment, a failure of one of the first and second rotary vacuum pumps 20, 30 involves a risk of contamination of the vacuum pumping system.
In all the shown constructions, if, for instance, when starting the vacuum pumping system, the first rotary vane vacuum pump 20 is stopped due to a failure and the second rotary vane vacuum pump 30 is switched ON, the oil vapors at the inlet of first rotary vane vacuum pump 20 will be pumped by the second rotary vane vacuum pump 30 and sucked into the vacuum chamber 60 or vacuum chambers 60, 70, thus contaminating the vacuum pumping system.
In some arrangements, an anti-suckback valve may be introduced between the vacuum pumps 20, 30 and the vacuum chambers 60, 70. The anti-suckback valve is operative to close when the vacuum pumps 20, 30 are inactive to prevent backflow into the vacuum chambers 60, 70. Upon activation of the vacuum pumps 20, 30, the anti-suckback valves open under the vacuum created by the vacuum pumps 20,30. The inventors have determined that in some operating conditions, the anti-suckback valves may open under activation of their associated pump 20, 30 but under certain flow conditions in the vacuum chambers 60, 70 may induce backflow from the pump 20, 30 into the vacuum chambers 60, 70. These operating conditions are typically likely to be present during uncoordinated startup of the vacuum pumps 20, 30, defective operation of the vacuum pumps 20, 30, or uncoordinated shutdown of the vacuum pumps 20, 30. Backflow from the pumps 20, 30 into the vacuum chambers 60, 70 may lead to contamination and inaccurate measurement by an analytical instrument operating within the vacuum system 100.
In some embodiments, one of the vacuum chambers 60, 70 of the vacuum system 100 may be in communication with atmosphere, such as through an aperture. In these embodiments, the vacuum chambers 60, 70 are maintained at different operating pressures during operation and fluid is continually drawn through the aperture by operation of the vacuum pumps 20, 30. Unsynchronized operation of the vacuum pumps 20, 30 when working on these embodiments has been found to create unexpected flow conditions that may lead to backflow from one or more of vacuum pumps 20, 30 into the vacuum chambers 60, 70.
In all the exemplary embodiments shown in
The management unit 90 is configured to control both the rotary vane vacuum pumps 20, 30 in a synchronized manner. By controlling the vacuum pumps 20, 30 in a synchronized manner a backflow condition from at least one of the vacuum pumps 20, 30 into the vacuum chamber 60, 70 is avoided.
In detail, the management unit 90 is intended to check whether a possible risk of contamination arises and, in the affirmative, to carry out the necessary corrective actions for avoiding that such contamination takes place.
To this purpose, the management unit 90:
Preferably, the management unit 90 switches off in a synchronized way both the positive displacement vacuum pumps 20, 30 in case the detected value of one or more identified parameter(s) of one or more of the positive displacement vacuum pumps exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
Preferably, the management unit 90 further triggers an alarm in case the detected value of one or more identified parameter(s) of one or more the positive displacement vacuum pumps exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
By acting in a synchronized way on the positive displacement pumps of the vacuum pumping system, and preferably on all the positive displacement pumps of the vacuum pumping system, the management unit 90 of the vacuum pumping system according to the invention allows to effectively prevent any risk of contamination due to operation of a positive displacement vacuum pump after a failure of another positive displacement vacuum pumps of the vacuum pumping system or to slow and deactivate a positive displacement vacuum pump in a synchronized way with the slowing and deactivation of a malfunctioning pump or a pump operating outside of its expected operational parameters.
And this result is achieved by the invention without the need of introducing any additional safety components.
With reference to the exemplary construction of
More particularly, the management unit 90 may be further configured to implement corrective actions on the turbomolecular vacuum pump 40 in case the detected value of one or more identified parameter(s) of one or more of the positive displacement vacuum pumps exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
For instance, the management unit 90 may be further configured to switch off the turbomolecular vacuum pump 40 in case the detected value of one or more identified parameter(s) of one or more of the positive displacement vacuum pumps exceeds the corresponding threshold value or the detected condition of one or more identified parameter(s) is not consistent with the corresponding threshold condition.
In
In the flow charts of
However, it is evident that this choice has not to be understood as limiting: positive displacement vacuum pumps are complex devices in which different operating parameters are strongly correlated such as power, current, voltage absorbed by the pump, temperatures of pump components, and so on; any of these and other parameters can be used as a control parameter. In some embodiments, the operating parameter may comprise measurement of the environment of the vacuum pumping system, such as a pressure of each of the vacuum chambers 60, 70, a flow rate through the connections between the pumps 20,30 and the vacuum chambers 60,70, or some combination of such factors. Moreover, in more complex control algorithms, several parameters may be used to check the operation of the positive displacement vacuum pumps.
Under this operative condition, the rotary vane vacuum pumps 20, 30 run at nominal frequency, the pressure(s)s in the vacuum chamber(s) 60,70 match the expected operating pressure(s), and the flow into each of the vacuum pumps 20,30.
The management unit 90 identifies two parameters related to a possible risk of contamination of the vacuum pumping system:
The first parameter can assume two conditions, i.e. YES or NO. The management unit 90 sets NO as a condition in which there is no risk of contamination and YES as a condition in which a risk of contamination arises.
The second parameter can assume a range of values and the management unit 90 sets a threshold minimum value, below which a risk of contamination arises.
Therefore, the operation of the management unit 90 under this first operative condition is as follows:
The above control cycle can be carried out continuously or at predetermined time intervals.
Under this operative condition, the rotary vane vacuum pumps 20, 30 will normally stop and the anti-suckback valve (ASBV) will close. This ensures that the vacuum system is not contaminated unless the ASBV malfunctions. Therefore, risk of contamination during the vent phase is relatively low.
In this condition, the management unit 90 identifies a single parameter related to a possible risk of contamination of the vacuum pumping system, i.e. the rotary vacuum pump is still running.
This parameter can assume two conditions, i.e. YES or NO. The management unit 90 sets NO as a condition in which there is no risk of contamination and YES as a condition in which a risk of contamination arises.
Therefore, the operation of the management unit 90 under this second operative condition is as follows:
The starting phase is the most critical phase in view of risks of vacuum pumping system contamination, because at atmospheric pressure the ASBV for pumps 20, 30 are open.
If during the starting phase, one of the pumps 20, 30 achieves the target frequency while the other pump 30, 20 for any reason is stopped, then the running pump is able to suck the oil vapours from the other pump 20 through the vacuum chamber 60. The final effect is the vacuum pumping system is contaminated.
During the starting phase, the pumps are started at their minimum frequency and gradual ramps up to the nominal frequency are performed. During these ramps, the differences in terms of pumping speed of the pumps connected to the same vacuum chamber have to be kept at a minimum. In embodiments where different sized or model pumps are employed the pumping speed of each pump may be different in synchronized operation, however their effective pumping on the vacuum is matched to avoid one pump drawing a backflow through another pump. The pumping speed or effective pumping of a pump may be reflected by one or more operating parameters including, for instance, the pump frequency, power draw, etc.
In this condition, the management unit 90 identifies two parameters related to a possible risk of contamination of the vacuum pumping system:
The management unit 90 sets a maximum threshold value for the aforesaid difference in pump frequency.
Therefore, the operation of the management unit 90 under this third operative condition is as follows:
In this case, only the smaller pump is started at first, and the larger pump is started at a later stage.
Therefore, the flow chart of
Then, the operation of the management unit is the same as described with reference to
It will be evident to the person skilled in the art that the above description has been given by way of non-limiting example only, and many variants and modifications are possible without departing from the scope of the invention as defined in the following claims. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation—the invention being defined by the claims.
For instance, it will be evident that many other operating conditions of the vacuum pumping system and corresponding parameters related to possible risk of contamination can be taken into account.
Moreover, although reference has been made to rotary vane vacuum pumps in the description of certain embodiments of the invention, it will be evident that the invention could be applied to a wide variety of vacuum pumping systems having a plurality of positive displacement vacuum pumps.
By way of example, the invention could be applied to a vacuum pumping system having a plurality of scroll vacuum pumps.
In this case, the risk of contamination would be connected to dust possibly present at the inlet of a scroll vacuum pump: if one of the scroll vacuum pumps stops due to a failure, the other vacuum pump(s) of the vacuum pumping system could suck the dust at the inlet of the scroll vacuum pump that has stopped; therefore, the sucked dust would pass through the vacuum chamber(s) to which the vacuum pumps are connected and the final effect is that the vacuum pumping system is contaminated.
With reference now to
The ion source 802 can be any known or hereafter developed ion source for generating ions and modified in accordance with the present teachings. Non-limiting examples of ion sources suitable for use with the present teachings include an atmospheric pressure chemical ionization (APCI) source, an electrospray ionization (ESI) source, a continuous ion source, a pulsed ion source, an inductively-coupled plasma (ICP) ion source, a matrix-assisted laser desorption/ionization (MALDI) ion source, a glow discharge ion source, an electron impact (EI) ion source, a chemical ionization (CI) source, or a photo-ionization (PI) ion source, among others. Additionally, as shown in
Analytes of interest, which are contained within the sample discharged from the ion source 802, can be ionized within the ionization chamber 850, which is separated from a first vacuum chamber 860 by a curtain plate 804a and an orifice plate 804b (collectively designated 804) having orifices (e.g., aperture 861) providing fluid communication between the ionization chamber 850 and the first vacuum chamber 860. In this embodiment, orifices in the curtain plate 804a and orifice plate 804b are sufficiently large to allow the incoming ions to enter the first vacuum chamber 860. By way of example, the orifices (e.g., aperture 861) can be substantially circular with a diameter in a range of about 0.6 mm to about 10 mm.
Although not shown in the schematic of
In various aspects, the ionization chamber 850 can be maintained at a pressure P0, which can be atmospheric pressure or a substantially atmospheric pressure (e.g., about 760 Torr). However, in some embodiments, the ionization chamber 850 can be evacuated to a pressure lower than atmospheric pressure, for example, via a pump (not shown) coupled to the ionization chamber 850.
Initially, ions generated by the ion source 802 can be successively transmitted in the direction indicated by the arrow in
The upstream ion guides 806, 810, 814 can have a variety of different configurations. By way of non-limiting example, the first ion guide 806 can comprise a set of rods arranged in a dodecapole configuration so as to provide a passageway for the transit of ions through the ion guide 806. An example of such an ion guide is described in U.S. Pat. No. 10,475,633, the teachings of which are incorporated by reference herein in their entirety. More generally, the first ion guide 806 can comprise any number of rods, for example, a plurality of rods maintained in a quadrupole, hexapole, octopole, or dodecapole configuration, or can be formed using a series of stacked rings such that the application of DC and/or RF voltages to one or more of these rods or rings, in a manner known in the art, in combination with gas dynamics can allow the ion guide 806 to focus the ions received through the aperture 861 as they pass through the ion guide 806 for transmission to downstream elements.
As described otherwise herein, operation of the vacuum pumping system can maintain the pressures in the various chambers within a desired range. By way of example, a first positive displacement vacuum pump 820 may be coupled to the first vacuum chamber 860 via an opening or port, for example, so as to apply a negative pressure to the first vacuum chamber 860 to maintain the pressure (P1) in the first vacuum chamber 860 in a range of between about 1 Torr and about 100 Torr, although other pressures can be used for this or for other purposes. In some aspects, the first vacuum chamber 860 may be maintained in a range of about 1 Torr to about 15 Torr, for example, in a range from about 4 Torr to about 8 Torr.
An aperture 871 disposed in an ion lens 808 (also referred to herein as IQ00) that is positioned downstream of the first ion guide 806 allows the passage of ions from the first vacuum chamber 860 into a second downstream vacuum chamber 870 in which another ion guide 810 is positioned. It will be appreciated that the vacuum chambers 860, 870 are therefore in fluid communication through the aperture 871 such that gas may flow therebetween depending, for example, on the differential pressures therebetween. In this embodiment, the aperture 871 in the ion lens 808 is sufficiently large to allow the ions transmitted from the first ion guide 806 to enter the second vacuum chamber 870.
The ion guide 810 can have the same or different configuration as ion guide 808 but may generally be configured to focus the ions received through the aperture 871 to downstream elements, for example, using a combination of electric fields and gas dynamics. As above, a power supply (not shown) can apply RF and/or DC voltage(s) to rods of the ion guide 810 to radially confine and focus the ions as they pass therethrough.
As shown in
An ion lens 812 (also referred to as IQ0) separates the second vacuum chamber 870 from the third vacuum chamber 880a, within which another ion guide 814 may be disposed. An aperture 881 provided within the ion lens 812 allows the passage of the ions transmitted from the ion guide 810 into the third vacuum chamber 880a. It will be appreciated that the vacuum chambers 870, 880a are therefore in fluid communication through the aperture 881 such that gas may flow therebetween depending, for example, on the differential pressures. In this embodiment, the aperture 881 in the ion lens 812 is sufficiently large to allow the ions transmitted from the second ion guide 810 to enter the third vacuum chamber 880a.
The ion guide 814 can have the same or different configuration as ion guide 810 but may generally be configured to further focus the ions received through the aperture 881 as they are transmitted through an intermediate pressure region prior to transmission to the mass spectrometer 818 through an aperture 891 in the ion lens 816 (also referred to herein as “IQ1”). In some embodiments, the ion guide 814 (also referred to herein as “Q0”) can be an RF ion guide and can comprise a quadrupole rod set. As above, a power supply (not shown) can apply RF to rods of the ion guide 814 to radially confine and focus the ions as they pass therethrough.
As shown in
The vacuum pump 840a may be any pump known in the art such as a turbomolecular pump, for example, that is generally able to maintain the chamber 880a at pressures at least below about 100 mTorr. In some embodiments, the third vacuum chamber 880a can be maintained at a pressure between about 3 to 15 mTorr, although other pressures can be used for this or for other purposes. While the positive displacement pumps 820, 830 may not be able to maintain such low pressures alone, the second positive displacement pump 830 may be coupled (e.g., in series) to the pump 840a to serve as a backing pump as shown in
Ions are transmitted from the ion guide 814 into the fourth vacuum chamber 880b containing a mass spectrometer 818, which typically operates at very low pressures (high vacuum) to reduce the chance of ions colliding with other molecules (e.g., gas molecules) within the one or more mass analyzers to enable the ions' characterization according to their mass-to-charge ratios (m/z). By way of non-limiting example, in one embodiment, the mass spectrometer 818 may comprise a detector, as well as two quadrupole mass analyzers (e.g., Q1, Q3) with a collision cell (e.g., q2) located between them. It will be apparent to those skilled in the art that the mass spectrometer 818 employed could take the form of a quadrupole mass spectrometer, triple quadrupole mass spectrometer, time-of-flight mass spectrometer, FT-ICR mass spectrometer, or Orbitrap® mass spectrometer, all by way of non-limiting example.
As shown in
It will be appreciated that not only are adjacent vacuum chambers (e.g., vacuum chambers 870, 880a) fluidly coupled through an aperture (e.g., aperture 881), but each of the vacuum chambers in the example MS system 800 are indirectly coupled to one another. In this manner, depending on the relative pressures between the various chambers, it will be apparent in light of the present teachings that the operation (or failure) of one pump (e.g., pump 820) may affect the pressure within and gas flows into or out of a vacuum chamber even if not directly coupled thereto. By way of non-limiting example, if both pumps 820 and 830 were turned off in an uncoordinated manner, a flow of gas between the downstream chambers could be generated due to the pressure differential between each chamber. The synchronized control of the parallel pumps 820, 830 as discussed otherwise herein (e.g., with reference to
The computer system 900 may be coupled via the bus 922 to a display 930, such as a cathode ray tube (CRT) or liquid crystal display (LCD), for displaying information to a computer user. An input device 932, including alphanumeric and other keys, is coupled to the bus 922 for communicating information and command selections to the processor 920. Another type of user input device is a cursor control 934, such as a mouse, a trackball or cursor direction keys for communicating direction information and command selections to the processor 920 and for controlling cursor movement on the display 930. This input device typically has two degrees of freedom in two axes, a first axis (i.e., x) and a second axis (i.e., y), that allows the device to specify positions in a plane.
A computer system 900 can perform the present teachings. Consistent with certain implementations of the present teachings, results are provided by computer system 900 in response to processor 920 executing one or more sequences of one or more instructions contained in memory 924. Such instructions may be read into memory 924 from another computer-readable medium, such as storage device 928. Execution of the sequences of instructions contained in memory 924 causes processor 920 to perform the process described herein. Alternatively, hard-wired circuitry may be used in place of or in combination with software instructions to implement the present teachings. Thus, implementations of the present teachings are not limited to any specific combination of hardware circuitry and software. For example, the present teachings may be performed by a system that includes one or more distinct software modules for synchronizing the operation of the pumps to prevent a backflow condition in accordance with various embodiments.
In various embodiments, the computer system 900 can be connected to one or more other computer systems, like computer system 900, across a network to form a networked system. The network can include a private network or a public network such as the Internet. In the networked system, one or more computer systems can store and serve the data to other computer systems. The one or more computer systems that store and serve the data can be referred to as servers or the cloud, in a cloud computing scenario. The one or more computer systems can include one or more web servers, for example. The other computer systems that send and receive data to and from the servers or the cloud can be referred to as client or cloud devices, for example.
The term “computer-readable medium” as used herein refers to any media that participates in providing instructions to the processor 920 for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as the storage device 928. Volatile media includes dynamic memory, such as the memory 924. Transmission media includes coaxial cables, copper wire, and fiber optics, including the wires that comprise the bus 922.
Common forms of computer-readable media or computer program products include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, digital video disc (DVD), a Blu-ray Disc, any other optical medium, a thumb drive, a memory card, a RAM, PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, or any other tangible medium from which a computer can read.
Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to the processor 920 for execution. For example, the instructions may initially be carried on the magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to the computer system 900 can receive the data on the telephone line and use an infra-red transmitter to convert the data to an infra-red signal. An infra-red detector coupled to the bus 922 can receive the data carried in the infra-red signal and place the data on the bus 922. The bus 922 carries the data to the memory 924, from which the processor 920 retrieves and executes the instructions. The instructions received by the memory 924 may optionally be stored on the storage device 928 either before or after execution by the processor 920.
The descriptions herein of various implementations of the present teachings have been presented for purposes of illustration and description. It is not exhaustive and does not limit the present teachings to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practicing of the present teachings. Additionally, the described implementation includes software, though the present teachings may be implemented as a combination of hardware and software or in hardware alone. The present teachings may be implemented with both object-oriented and non-object-oriented programming systems.
It will be evident that the foregoing description is for the purpose of illustration only, and not for the purpose of limitation—the invention being defined by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20177546.7 | May 2020 | EP | regional |
