WO2023021090A1

WO2023021090A1 - Leak detection of vacuum systems

Info

Publication number: WO2023021090A1
Application number: PCT/EP2022/072960
Authority: WO
Inventors: Simon CANDRIES; Yun SHI
Original assignee: Atlas Copco Airpower Nv Atlas
Priority date: 2021-08-19
Filing date: 2022-08-17
Publication date: 2023-02-23
Also published as: BE1029702A1; TW202319850A; BE1029702B1; GB202111884D0; GB2609962A

Abstract

A vacuum system having a leak detection state for self-detecting a leak of the vacuum system, the vacuum system comprising: a process chamber having a fluid volume to be evacuated; a vacuum pump configured to evacuate the process chamber during normal use of the vacuum system and prior to entering a leak detection state, which leak detection state is different to a normal use configuration; at least one pressure sensor configured to measure the pressure within the process chamber; and a recorder programmed to record the pressure measured within the process chamber; wherein, in the leak detection state, the evacuated process chamber is isolated and the recorder is programmed to record data corresponding to the pressure measured within the evacuated process chamber over time and the vacuum system is configured to identify pressure data indicative of a leak of the process chamber.

Description

Leak Detection of Vacuum Systems

Field

[001 ] The present invention relates to vacuum systems, in particular a vacuum system configured to self-detect a leak of the vacuum system, in particular a leak of a process chamber, and to methods for detecting leaks in vacuum systems.

Background

[002] It is accepted that vacuum systems can never be entirely free from leaks in practice, i.e. absolutely vacuum-tight. A leak may be defined as any fault in a vacuum system through which material can pass from a higher-pressure volume to a lower pressure volume.

[003] Nevertheless, the leak rate (e.g. the size of a leak) of a vacuum system must be kept below a satisfactory level, in order that a vacuum pump can effectively and efficiently produce and maintain a required pressure in the vacuum system.

[004] Leak rate may be defined as the size of a leak in terms of the amount of material that passes through the leak per unit of time at a given pressure difference.

[005] As used herein, the term “leak” refers to the overall leak to or from a vacuum system or other test object. A leak may be comprised of an individual fault in a vacuum system or may be the result of several faults in the vacuum system.

[006] Typically, a fault in a vacuum system results in material passing from the exterior (higher pressure area) of a vacuum system to its interior (lower pressure area). It is essential for many industrial and experimental processes performed under vacuum (including low or partial vacuums) to be free from contamination by leakage into the vacuum system.

[007] Therefore, there exist several approaches to detecting the presence and size of a leak in a vacuum system. [008] For example, distinct leak detection apparatus, often including their own vacuum pump, can be connected to a vacuum system to perform a leak detection test.

[009] In another approach, a tracer gas, such as helium (because it is relatively rare in the atmosphere), can be supplied outside an evacuated apparatus which comprises a mass spectrometer. If a leak is present, the tracer gas will traverse the leak path and will appear and be detected by the mass spectrometer inside the apparatus. Similarly, an apparatus could be pressurised with a tracer gas (at a greater pressure than the external environment) and escape of the tracer gas from the apparatus can be searched for.

[010] Apparatus can also be covered with masking compounds or envelopes to confirm a suspected leak. And, whilst it is not as widely used as it once was, bubble testing by immersing a pressurised apparatus in a clear liquid, water for example, can also show the presence, size, and often location, of a leak.

[011 ] For vacuum systems that must be sealed off, either under vacuum or filled with a fluid which must not be lost or contaminated by in-leakage, very exacting standards are required, and these standards must be regularly checked and maintained throughout the life of the vacuum system.

[012] Existing approaches including those described above, however, are labour and resource intensive, usually requiring dedicated leak detecting apparatus to conduct a leak test, and often requiring a skilled specialist in order to be reliably manually performed.

[013] Thus, the burden of checking high vacuum tightness standards is significant, particularly when an engineer or other testing professional is required to travel to each vacuum system in situ on a regular basis to test its performance. Given that the production of vacuum pumps and vacuum systems is a highly specialised field, a producer of vacuum systems may have a client base which is spread over a vast geographical area, thereby exacerbating that burden. [014] Furthermore, a known phenomenon is the potential presence of a virtual leak in a vacuum system. In other words, a leak - or rather the characteristics thereof - may be detected even though a vacuum system is sufficiently leak free I vacuum tight. A so-called virtual leak may be attributed to outgassing or the release of trapped pockets of gas which slowly escape over time within a vacuum system, possibly at a particular temperature or stage of a process.

[015] Therefore, a rise in pressure may be detected in an isolated vacuum system which is under vacuum and which has no Teal’ leak. An engineer could be called to test a vacuum system and may be misled into thinking a vacuum system comprises a leak when, in fact, it does not. Significant effort, resources, and system downtime can be spent for no useful reason.

[016] The present invention aims to address these and other problems with the prior art.

Summary

[017] Accordingly, in a first aspect, the present invention provides a vacuum system having a leak detection state for self-detecting a leak of the vacuum system. The vacuum system comprises: a process chamber having a fluid volume to be evacuated; a vacuum pump configured to evacuate the process chamber during normal use of the vacuum system and prior to entering a leak detection state, which leak detection state is different to a normal use configuration; at least one pressure sensor configured to measure the pressure within the process chamber; and a recorder programmed to record the pressure measured within the process chamber. In a leak detection state, the evacuated process chamber is isolated and the recorder is programmed to record data corresponding to the pressure measured within the process chamber over time and the vacuum system is configured to identify pressure data indicative of a leak of the process chamber.

[018] This configuration is particularly advantageous because the recorder is configured to automatically record data (i.e. without separate manual, user initiated intervention) corresponding to the pressure measured within the process chamber over time so that the recorded data may be used to determine whether a leak of the process chamber is present and the magnitude of the leak detected. The vacuum system is thus able to identify and quantify leaks of the process chamber itself, e.g. rather than from any objects which might be placed within the process chamber.

[019] Thus, the ease and accuracy with which the presence and magnitude of a leak may be detected is improved. More specifically, a user is not required to actively monitor or manually record data corresponding to the pressure in the process chamber and time elapsed. The vacuum system is autonomous when in the leak detection state and, in particular, is configured to automatically detect whether or not a leak is present by plotting a pressure change within the process chamber over time.

[020] The vacuum system is therefore provided with means for self-detecting the presence of a leak, and particularly means for self-detecting the presence of a leak of the process chamber itself. Separate leak detecting apparatus is not required.

[021 ] Generally, the process chamber may form an integral part of the vacuum system during its normal use.

[022] In embodiments, data indicative of a leak of the process chamber may include data corresponding to an increase in pressure within the process chamber.

[023] Advantageously, the vacuum pump is configured to evacuate the process chamber prior to entering the leak detection state and during normal use of the vacuum system. The leak detection state is different to a normal use configuration of the vacuum system.

[024] As used herein, the term “leak detection state” refers to a state in which the process chamber is evacuated and isolated primarily for the purpose of leak detection.

[025] In embodiments, a leak may be defined as a change in the pressure measured within the process chamber of at least a few millibar, for example 10 mbar or more, per minute. [026] As used herein, the term “normal use” refers to a state or configuration in which the vacuum pump is configured to evacuate, i.e. reduce the pressure within, the process chamber for a purpose which is not primarily leak detection. For example, in normal use, the vacuum pump may evacuate the process chamber for the primary function of the process chamber to be performed.

[027] In other words, the vacuum pump is configured not only to evacuate the process chamber as part of a leak detection test, but is also configured to evacuate the process chamber when leak detection is not the reason the vacuum pump is functioning. Therefore, a vacuum pump distinct from the one operated in normal use is not required in the leak detection state, and the vacuum system is thus configured to conduct an autonomous leak detection test.

[028] As used herein, the term “evacuated” refers to producing a pressure in the process chamber which is lower than ambient (e.g. atmospheric) pressure. For the purposes of the invention, atmospheric pressure shall be taken to be 101 ,325 Pa unless state otherwise.

[029] In embodiments, the vacuum pump may be configured to produce an ultra- high vacuum (UHV), i.e. below 10’⁷ mbar, within the process chamber.

[030] In embodiments, the vacuum pump may be configured to produce a high vacuum (1 O’³ mbar to 10’⁷ mbar), within the process chamber.

[031 ] In embodiments, the vacuum pump may be configured to produce a medium vacuum (from a few mbar, or 1 to 10’³ mbar), within the process chamber.

[032] In embodiments, the vacuum pump may be configured to produce a rough vacuum within the process chamber.

[033] In embodiments, in the leak detection state, the vacuum pump may be configured to produce an ultra-high vacuum (UHV), i.e. below 10’⁷ mbar, within the process chamber. [034] In embodiments, in the leak detection state, the vacuum pump may be configured to produce a high vacuum (10^-3 mbar to 10’⁷ mbar), within the process chamber.

[035] In embodiments, in the leak detection state, the vacuum pump may be configured to produce a medium vacuum (from a few mbar, or 1 to 10’³ mbar), within the process chamber.

[036] In embodiments, the vacuum pump may be configured to evacuate the process chamber in a substantially uninterrupted manner prior to entering the leak detection state. For example, the vacuum system may be configured so that the process chamber is evacuated substantially continuously, without intervals of increasing pressure in the process chamber.

[037] In embodiments, the vacuum pump may be a scroll-type or screw-type vacuum pump. In embodiments, the vacuum pump may be a turbomolecular pump. In embodiments, the vacuum pump may be a multi-stage vacuum pump.

[038] In embodiments, the vacuum system may comprise an auxiliary pump, which may also be referred to as a booster pump.

[039] As used herein, the term “isolated” refers to a configuration in which fluid communication between the interior of process chamber and the exterior of the process chamber, typically including the vacuum pump, is substantially prevented.

[040] In embodiments, in the leak detection state, the process chamber is substantially unoccupied. In other words, objects which might otherwise be placed in the process chamber during normal use are not present in the process chamber when the process chamber is in the leak detection state.

[041 ] Alternatively, in embodiments, the process chamber may occupy one or more distinct objects in the leak detection state. [042] In embodiments, the recorder may be formed as part of the vacuum pump or process chamber. In embodiments, the recorder may be formed as part of a distinct unit, such as a computer or smart device. Generally, the recorder may be configured to record data digitally.

[043] In embodiments, the recorder may be wirelessly connected to one or more parts of the remainder of the vacuum system. For example, the recorder may be wirelessly connected to the or each pressure sensor. In embodiments, the or each pressure sensor may be in wired connection with the recorder. In embodiments, the vacuum system may comprise more than one pressure sensor so that in the event a first pressure sensor fails, a further pressure sensor is present and configured to measure the pressure within the process chamber.

[044] In embodiments, the recorder may be programmed to calculate one or more properties of a detected leak. For example, the presence, magnitude and/or estimated location may be calculated by the recorder based on the recorded data.

[045] In embodiments, the recorder may be programmed to calculate a pressure rise rate based on the recorded pressure change within the process chamber over a given time period.

[046] In embodiments, the recorder may be programmed to calculate a leak rate of the process chamber. A leak rate may be based on the volume of the process chamber (e.g. the internal volume of the evacuated space upstream of the isolation valve) and the recorded data. In embodiments, the recorder may be configured to calculate a leak rate, q_L, based on the following formula:

wherein V is the volume of the process chamber, and Ap is the change in pressure within the process chamber over the elapsed time At. [047] In embodiments, the recorder may be configured to take into account one or more properties of the process chamber, for example the volume of the process chamber or an acceptable leak rate of the process chamber.

[048] In embodiments, the recorder may be configured to take into account one or more properties of a gas, for example atmospheric air, within the process chamber or which will traverse a wall defining the process chamber should a fault in the wall exist. For example, the molar weight, gas constant, and/or temperature of the gas may be recorded and may be taken into account as part of a calculation made by the recorder.

[049] Thus, in embodiments, the recorder may be configured to calculate a leak rate, q_L, of the vacuum system based on the following formula:

wherein M is the Molar mass of the gas, Am is the mass change in g, R is the gas constant, T is gas temperature (in Kelvin) and At is the elapsed time.

[050] For example, for dry air (i.e. air at standard atmospheric pressure containing none or negligible traces of water vapor), the Molar mass of dry air, M, would be approximately 28.9634 g/mol, the gas constant, R, would be approximately 8.314 J-K~¹-mol~¹ and the temperature, T, would be 293 Kelvin.

[051 ] In embodiments, the vacuum system may comprise one or more additional sensors for recording the one or more properties of a gas present inside and/or outside of the process chamber.

[052] In embodiments, the recorder may be programmed to determine whether a pressure change over an elapsed time corresponds to a leak and/or outgassing from the vacuum system. In other words, the recorder may be configured to determine the nature of a pressure change or other leak-indicative data or threshold within the process chamber. For example, if a pressure rise rate is substantially constant and does not stabilise, a real leak may be present. Conversely, if a pressure rise rate tapers off after an initial rise, a virtual leak may be present (or a combination of a real leak and outgassing). Thus, the vacuum system may be configured to differentiate between a Teal’ leak, i.e. a fault in a wall defining the process chamber, and a virtual leak, and/or whether there is a combination of a Teal’ leak and evolution of gas from part of the process chamber.

[053] In embodiments, the recorder may be programmed to record when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded. The recorder may be programmed with a pre-set time period to elapse and/or a predetermined pressure change threshold. In embodiments, the recorder may be programmed to stop recording when at least one of these parameters is recorded. The pre-set pressure change threshold may comprise a pressure value which is greater than the pressure of the evacuated process chamber and which indicates that an unacceptable leak rate is present. For example, a pre-set pressure change threshold of 50 to 100 mbar(a) may indicate a large leak is present in the process chamber.

[054] In embodiments, the recorder may be programmed to record data corresponding to the pressure of the process chamber and the time elapsed until only a pre-set time period has elapsed.

[055] In embodiments, the recorder may be programmed to record data corresponding to the pressure of the process chamber and the time elapsed until only a pre-set pressure change threshold is reached. The pre-set pressure change threshold may be referred to as the ‘Delta P limit’, or ‘Ap limit’.

[056] In embodiments, the recorder may be programmed to cease recording data when either a pre-set time period has elapsed or a pre-set pressure change threshold is reached and the recorder ceases recording data when the first of these parameters is reached. Therefore, the vacuum system may allow a user to set a target pressure (e.g. vacuum level) and maximum allotted time for a leak detection cycle to complete. [057] As described, the recorder may be programmed to record data until either a pre-set time period has elapsed, i.e. a maximum pressure rise time has passed, and/or a pre-set pressure change threshold is reached. Therefore, in embodiments, it may be that the pre-set pressure change threshold is not reached by the time the pre-set time period has elapsed or, alternatively, that the pre-set pressure change threshold is reached before the pre-set time period has elapsed. In either case, the recorder nevertheless ceases the leak detection test and stops recording data.

[058] There exists either or both a pre-set time period and/or a pre-set pressure change threshold because, otherwise, leak detection could theoretically continue indefinitely in a leak free vacuum system.

[059] In embodiments, the vacuum system may further comprise a controller. In embodiments, the controller and the recorder may be separate entities within the vacuum system. In embodiments, the controller and the recorder may be formed as part of a single unit.

[060] In embodiments, the controller may be part of the vacuum pump. In embodiments, the controller may be part of a distinct unit. In embodiments, the controller may be a separate computer, for example a laptop or smart device.

[061 ] In embodiments, the controller may be programmed with a series of pre-set instructions or commands. In embodiments, the controller may comprise readable and/or editable memory. In embodiments, the memory may be configured to store data from one or more completed iterations of the leak detection state (e.g. complete leak detection cycles). In embodiments, the controller may be configured to compare data from the one or more completed iterations of the leak detection state which are stored on the memory.

[062] In embodiments where the vacuum pump is a multistage vacuum pump, the controller may be configured to actuate stages of the multistage vacuum pump in a predetermined order. [063] In embodiments, the controller may be configured to receive instruction from the recorder, and/or the recorder may be configured to receive instruction from the controller.

[064] In embodiments, the controller may be programmed to end the leak detection state when the recorder records that at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded. Thus, the controller may be configured to transition the vacuum system from the leak detection state to a normal use state once a pre-set time period has elapsed or a pre-set pressure change threshold is recorded by the recorder.

[065] In embodiments, the controller may be configured to stop the recorder recording data corresponding to the pressure measured in the process chamber when the recorder records that at least one of a pre-set time period has elapsed and/or a preset pressure change threshold is recorded. Thus, the vacuum system may complete a leak detection test and be automatically transitioned to a normal use state ready for normal use.

[066] In embodiments, the controller may be configured to transition the vacuum system from the leak detection state to a normal use state only if the recorder determines that a leak is not present or that a detected leak is not significant enough to for further action to be taken. For example, if a leak is detected but the leak rate may be sufficiently overcome by the pumping speed of the vacuum pump during normal use, the controller may nevertheless transition the vacuum system from the leak detection state to a normal use state.

[067] In embodiments, the controller may be programmed to prevent a transition from the leak detection state to a normal use state if a sufficiently large leak, or any leak, is detected by the recorder. For example, if a detected leak has a leak rate which is too great to be overcome by the pumping speed of the vacuum pump during normal use, a transition from the leak detection state to the normal use state may be prevented. Therefore, normal use of the vacuum system may be automatically disabled if the recorder considers a detected leak to be too significant for normal use of the vacuum pump to be resumed. A user may be alerted to the presence of a leak, or a leak which is significantly large, in order that further action is taken before the vacuum system is reverted to normal use.

[068] In embodiments, the controller may be programmed to turn the vacuum system OFF after the leak detection state has ended.

[069] In embodiments, the vacuum system may further comprise a valve arranged between the process chamber and the vacuum pump. The valve may be configured to selectively isolate the process chamber. The valve may be operable by the controller. In embodiments, the controller is programmed to close the valve in order to isolate the process chamber in the leak detection state. In embodiments, the valve may be configured such that it does not leak by more than approximately 10 mbar per minute.

[070] In embodiments, a said pressure sensor may be located on the process chamber side of the valve.

[071 ] In embodiments, operation of the valve by the controller may be automated, for example once the recorder records that the process chamber is evacuated (in which case the valve is then closed in order to isolate the process chamber). In other words, operation of the valve may not be via a separate user-initiated action.

[072] In embodiments, the controller may be programmed to launch the leak detection state.

[073] In embodiments, the controller may be programmed to actuate the vacuum pump to evacuate the process chamber and, in the leak detection state, to isolate the process chamber once the process chamber has been evacuated. Therefore, a user is not required to manually actuate the vacuum pump to evacuate the process chamber or manually isolate the process chamber in the leak detection state. Thus, in the present invention, the controller may be programmed to initiate each of the steps of a leak detection test so that no intermediate user-initiated actions are required. The vacuum system may thus be configured to effectively run a program of steps in order to generate and record data corresponding to the pressure of the process chamber over a given time period.

[074] In embodiments, the controller may be programmed with a test schedule for triggering of the leak detection state. Thus, leak detection tests may be automatically periodically carried out without each test having to be manually triggered by a user. For example, the controller may be programmed with instructions to initiate a weekly or monthly leak detection test.

[075] In embodiments, the recorder may be programmed with a test schedule for triggering of the leak detection state, and the recorder is configured to actuate the controller.

[076] In embodiments, the recorder may be configured to calculate one or more properties of a detected leak from two or more iterations of the leak detection state. In other words, the recorder may be configured to calculate whether a leak is worsening or is stabilised over an extended period of time by plotting and comparing the results of several leak detection tests. For example, the recorder may be configured to inform a user that a leak is increasing by so many litres per hour, per month.

[077] In embodiments, the recorder may be configured to indicate an estimated energy and/or financial cost of a detected leak. For example, the recorder may be configured to calculate and indicate that a detected leak is likely to cost an average of 100kWh more power per month.

[078] In embodiments, the vacuum system may be configured to enter the leak detection state only if the vacuum pump evacuates the process chamber within a preset maximum time period. In other words, if the vacuum pump is unable to evacuate the process chamber by a predetermined time limit, the leak detection state is not triggered. Therefore, in the event a leak which is large enough to overcome the vacuum pump speed is present, the vacuum pump is prevented from indefinitely attempting to evacuate the process chamber. Advantageously, therefore, the leak detection state is not triggered if the process chamber cannot be reliably evacuated within a pre-set maximum time period. [079] In embodiments, the vacuum system may be configured to enter the leak detection state only if the vacuum pump reaches one or more minimum operating conditions. In other words, the vacuum system is configured to not enter the leak detection state if one or more minimum operating conditions are not met.

[080] In embodiments, the one or more minimum operating conditions may include a minimum speed and/or temperature of the vacuum pump. For example, the vacuum pump may work most effectively in the leak detection state if all or part of the vacuum pump (e.g. lubricating fluids) is first warmed to a minimum operating temperature. Therefore, the risk of damage to the vacuum pump or another part of the vacuum system is minimised.

[081 ] In embodiments, the valve is configured to open and allow fluid communication between the vacuum pump and process chamber only when the one or more minimum operating conditions is met. In other words, in embodiments the vacuum pump is operated to meet the one or more minimum operating conditions while the valve is closed.

[082] In embodiments, the vacuum system may include one or more additional sensors for monitoring the condition of the vacuum pump or other parts of the vacuum system. For example, the vacuum system may include one or more sensors for monitoring the temperature, motor current and/or electrical supply of the vacuum pump. Therefore, if any abnormal conditions are detected, the function of the vacuum pump may be regulated or disabled.

[083] In embodiments, in the leak detection state the vacuum pump may operate at an idle speed. In embodiments, in the leak detection state the vacuum pump may be substantially at a stop. Therefore, monitoring of the pressure within the process chamber can take place once the vacuum pump has safely returned to an idling speed or has stopped. In embodiments, the speed of the vacuum pump is reduced only once the process chamber is isolated following evacuation of the process chamber. [084] In embodiments, the vacuum system may further comprise a user interface. In embodiments, the user interface may be configured for the input of information into the recorder and/or the controller.

[085] In embodiments, the information may include one or more of the following: properties of the process chamber such as the volume of the process chamber; and/or the pressure to be produced in the process chamber when the process chamber is evacuated; and/or the pre-set time period to elapse; and/or the second pressure corresponding to a pre-set pressure change threshold. Information may therefore be predetermined and programmed into the vacuum system prior to a leak detection test.

[086] In embodiments, the user interface may be configured to display information to a user. In embodiments, the information displayed by the user interface may correspond to the data recorded and/or calculated by the recorder. In embodiments, the user interface may be configured to display information to a user visually and/or audibly.

[087] The user interface thus allows a user to input or receive information from the vacuum system. In embodiments, the controller may include the user interface.

[088] In embodiments, the recorder or the controller may be programmable with a test schedule via the user interface.

[089] In embodiments, the recorder may be configured to transmit recorded or calculated data to a distinct receiver, for example a separate computer or database.

[090] In embodiments, the vacuum system may include at least one sensor for detecting one or more conditions of the vacuum system during normal use of the vacuum system. In embodiments, the recorder may be configured to monitor data corresponding to said condition(s).

[091 ] For example, the recorder may be configured to monitor the work rate, e.g. load or flowrate, of the vacuum pump during normal use and record changes (e.g. increases) over time. The work rate may be determined by flow rate, load, by pump motor speed (e.g. average pump motor speed over time), by pressure, and/or by another metric.

[092] In embodiments, the controller may be configured to prompt a manual or automatic transition to the leak detection state of the vacuum system dependent on the one or more monitored conditions. For example, the controller may be configured to prompt a manual or automatic transition to the leak detection state if the work rate of the vacuum pump during normal use meets or exceeds or crosses a leak-indicative threshold or increases by a set delta. A leak-indicative threshold may include a pressure value of the process chamber, for example.

[093] In other words, the vacuum system may include, in a normal use state (e.g. not a leak detection state), a leak screening function in which the potential need for a transition to the leak detection state is monitored. The leak screening function allows values or behaviour which is indicative of a leak to be identified and automatically acted upon.

[094] For example, the controller may be programmed with a test schedule (e.g. a monthly test schedule), and the leak screening function allows the controller to prompt an unscheduled transition to the leak detection state if the potential presence of a leak is detected during normal use.

[095] This is advantageous because, over time the vacuum pump may have to work progressively harder to achieve a set pressure within the process chamber. This would require more energy, and/or more time. Monitoring the potential need for a leak detection test in a normal use state minimises the risk of excess energy being spent to undertake a vacuum process. It may be that a leak in the vacuum system, e.g. in the process chamber, occurs between scheduled leak detection tests and is not otherwise noticeable. Equally, if a leak is not detected, then investigations into other non-leak related causes for the leak-indicative data may be generated.

[096] In embodiments, the vacuum pump may be a variable speed drive (VSD) vacuum pump and the recorder may be configured to monitor the work rate of the VSD pump to produce / reach a required pressure, e.g. vacuum level, in the process chamber. An increase in work rate of the VSD pump over time to reach that required pressure may indicate the presence of a leak (as the VSD pump has to work harder over time to achieve the same pressure in the process chamber). Thus, the controller may be configured to prompt a transition to the leak detection state if leak-indicative data is recorded during normal use.

[097] For example, the vacuum pump may be configured to reach a pressure of around 50 mbar absolute. Pump motor speed may be controlled, by a proportional integral (PI) controller for example, to reach that pressure at a speed in a range of from around 600 RPM to around 7000 RPM, for example. In this scenario, the pump motor speed required to reach the pressure of around 50 mbar absolute may be monitored, and any changes (e.g. increase) may be detected. Alternatively, the vacuum pump may be controlled to operate at a particular speed, and the pressure reached in the process chamber is a result of that particular speed. In this scenario, changes in the pressure reached at the controlled pump speed may be detected. For example, a change of between around 5% to around 20%, 10% being an example, in the required pump speed or pressure reached may be indicative of a leak. In these scenarios, the controller may be configured to alert the user (e.g. prompt a manual transition to the leak detection state), or automatically transition the vacuum system to the leak detection state. Alternatively, a test schedule may be updated to bring forward the next scheduled transition to the leak detection state.

[098] In embodiments, an automatic transition to the leak detection state may occur only after the normal use process during which the transition requirement is identified has completed.

[099] In embodiments, the vacuum pump may be a fixed speed vacuum pump and the recorder may be configured to monitor and determine whether a required pressure in the process chamber is consistently met over time, or whether the pressure produced by the vacuum pump decreases over time.

[100] A manual transition may take the form of a display to a user via the user interface, in order to cause or encourage the user to actuate a transition to the leak detection state. The display may take the form of a message on a digital display, and/or via an audible alert.

[101 ] An automatic transition may include an algorithm or the like which automatically causes the vacuum system to transition to the leak detection state when one or more said leak-indicative data points are recorded.

[102] In embodiments, the recorder may be configured to calculate the average load of the vacuum pump during normal use over a set period of time. The average load may be calculated using the measured actual speed of the vacuum pump and the maximum speed of the vacuum pump, for example using the following formula:

Actual Speed Maximum Speed

[103] For example, average load may be recorded at set time intervals, e.g. hourly intervals.

[104] In embodiments, the recorder and/or controller may include a moving window array or algorithm. For example, hourly average load measurements may be plotted in a moving window array as a series of ‘y’ data points. In embodiments, the recorder and/or controller may include a first in first out (FIFO) principle. In other words, the moving window array may be configured to discard an oldest recorded data point when a new data point is recorded and included in the moving window array.

[105] In embodiments, the ‘y’ data points may be used to calculate a linear regression curve.

[106] Typically, the linear regression curve is calculated only when the moving window array is substantially entirely filled I complete. Typically, the moving window array length may be between around one week and around four weeks. The said intervals may be between around 1 hourly intervals and around 24 hourly (i.e. one a day) intervals. [107] In embodiments, a calculation as to whether the vacuum pump load is changing, e.g. increasing or decreasing, may be derived from the linear regression curve. For example, a key performance indicator (KPI) may be calculated.

[108] For example, a calculation may be made as to whether coefficient ‘a’ substantially deviates from zero (a dead-band). If it does, the controller may be configured to prompt the manual or automatic transition to the leak detection state. The KPI may be substantially 100% if ‘a’ does not substantially deviate from zero.

[109] If ‘a' does substantially deviate from zero, a key performance indicator may be calculated using the following formula:

KPI = (1 — w x a x y) x 100%

Where ‘w’ is an extra tuning weight,

is the total increase in load divided by the

maximum load as a reference.

[110] In embodiments, the recorder may be configured to calculate, as a threshold, a normal slope increase of, for example, pump load and the dead-band is set to that threshold. For example, a load increase of between around 5% to around 20% over a period of around 1 week to around 4 weeks may be set. Typically, a shorter interval time requires a higher dead-band in order to filter out what are considered normal changes in production set up that require changes in flow demand.

[111 ] In embodiments, if the KPI drops below a set threshold, an alert may be generated via the user interface by the controller to manually or automatically prompt a transition to the leak detection state.

[112] In a further aspect, the present invention provides a computer-readable medium comprising instructions which, when executed by a computer, provides the recording and controlling aspects of the system described above. [113] In embodiments, the instructions may include instructions to monitor the actual speed and/or maximum speed of the vacuum pump during a normal use state of the vacuum system.

[114] In embodiments, the instructions may include instructions to calculate whether the load of the vacuum pump changes over a set time period and to prompt a transition to the leak detection state of the vacuum system if the calculated load change meets a load threshold.

[115] In a further aspect, the invention provides a method of self-determining the extent of a leak of a vacuum system, comprising the steps of: (i) providing a vacuum system in accordance with any preceding aspect and/or embodiment; (ii) evacuating the process chamber of the vacuum system using the vacuum pump; and (iii) subsequently actuating a leak detection state of the vacuum system which is different to a normal use configuration including: (a) isolating the evacuated process chamber; and (b) recording data corresponding to the pressure of the process chamber and identifying data indicative of a leak of the process chamber if it is recorded. The step of recording data corresponding to the pressure of the process chamber is carried out by the recorder of the vacuum system.

[116] In the method of the present invention, data corresponding to the pressure of the process chamber is automatically recorded by the recorder of the vacuum system. Also, the vacuum pump of the vacuum system is configured not only to evacuate the process chamber during a leak detection state of the vacuum system but also during normal use of the vacuum system.

[117] In embodiments, the method may comprise the further step of calculating a leak rate of the process chamber of the vacuum system. This further step may be performed by the recorder of the vacuum system.

[118] In embodiments, the method may comprise the further step of recording when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded. [119] In embodiments, the step of recording data corresponding to the pressure of the process chamber may be automatically stopped when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded.

[120] In embodiments, the step of recording data may stop only when a pre-set time period has elapsed. In embodiments, the step of recording data may cease only when a pre-set pressure change threshold is reached.

[121] In embodiments, the method may comprise the further step of automatically ending the leak detection state when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded.

[122] The present invention therefore provides a method wherein a leak detection test of a vacuum system is automatically ceased once either a pre-set time period has elapsed and/or a pre-set pressure change threshold is reached. Thus, detection of a leak in a vacuum system may be automated. A user is not required to manually monitor the pressure of the process chamber or the time elapsed, or record corresponding data, or manually cease leak detection. The vacuum system may be automatically transitioned from the leak detection state back to normal use once a leak detection test has been completed.

[123] In embodiments, the step of isolating the process chamber may only be carried out if the preceding step of evacuating the process chamber is completed within a preset maximum time period. Thus, if the vacuum system is unable to evacuate the process chamber, for example due to a major leak (i.e. one which cannot be overcome by the pumping speed of the vacuum pump), this step is not carried out indefinitely.

[124] In embodiments, the vacuum system may include a controller and one or both of the steps of evacuating the process chamber and isolating the process chamber may be initiated by the controller of the vacuum system. Therefore, a user is not required to manually carry out one or both of these steps and automation of the method is improved. [125] In embodiments, the method may comprise the further steps of detecting one or more conditions of the vacuum system during normal use of the vacuum system; monitoring data corresponding to the one or more detected conditions; and prompting a transition to the leak detection state dependent on the one or more monitored conditions.

[126] In embodiments, a said condition may be the required load of the vacuum pump to produce a pressure in the process chamber and the method may further comprise the step of prompting a transition to the leak detection state when the required load of the vacuum pump meets a leak-indicative threshold.

[127] In embodiments, the method may comprise the further step of inputting information into the vacuum system. In embodiments, the vacuum system may include a user interface configured to facilitate the input of information into the vacuum system.

[128] In embodiments, the further step of inputting information into the vacuum system may be carried out prior to the step of actuating the leak detection state. In embodiments, the information may be information corresponding to one or more of the following: the volume of the process chamber; the pressure to be produced in the process chamber when the process chamber is evacuated; the pre-set time period to elapse; and/or a pressure corresponding to a pre-set pressure change threshold.

[129] In embodiments, the method may comprise the further step of repeating the step of actuating a leak detection state according to a predetermined schedule. Thus, a leak detection test of the vacuum system may be automatically carried out on a regular basis so that a user is not required to manually actuate a leak detection test. Repeating a leak detection test according to a predetermined schedule also allows a user to alerted to the potentially worsening of a detected leak.

[130] In embodiments, the method may comprise the further step of actuating the vacuum pump to reach one or more minimum operating conditions prior to the step of actuating the leak detection state. [131 ] In embodiments, the one or more minimum operating conditions may include a minimum speed and/or temperature of the vacuum pump. For example, the vacuum pump may work most effectively in the leak detection state if all or part of the vacuum pump (e.g. lubricating fluids) is first warmed to a minimum operating temperature. Therefore, the risk of damage to the vacuum pump or another part of the vacuum system is minimised.

[132] In embodiments, the method may comprise the further step of isolating the process chamber prior to actuating the vacuum pump to reach the one or more minimum operating conditions.

[133] In embodiments, the method may comprise the further step of fluidly connecting the process chamber and the vacuum pump once the vacuum pump has reached the one or more minimum operating conditions.

[134] In embodiments, the vacuum system may include a valve arranged between the vacuum pump and the process chamber, wherein the valve may be configured to selectively isolate the process chamber. In embodiments, the valve may be operable by the controller of the vacuum system.

[135] In embodiments, the method may comprise the further step of bringing the speed of the vacuum pump to a idle speed after the process chamber is isolated. In embodiments, the method may comprise the further step of bringing the speed of the vacuum pump substantially to a stop after the process chamber is isolated.

[136] In embodiments, the method may comprise the further step of displaying the data recorded by the recorder via a user interface of the vacuum system. In embodiments, the method may comprise the further step of displaying the calculated leak rate via a user interface of the vacuum system.

[137] In embodiments, the method may comprise the further step of stopping the leak detection state only if the recorder of the vacuum system determines that a leak is not present or that a detected leak is not significant enough to for further action to be taken. For example, if a leak is detected but the leak rate may be sufficiently overcome by the pumping speed of the vacuum pump in the normal use state, the vacuum system may nevertheless be transitioned from the leak detection state to a normal use state. Conversely, if a sufficiently large leak, or any leak, is detected the step of stopping the leak detection state may not be performed. Thus, the vacuum system may be prevented from returning to a normal use state. A user may therefore be alerted to the presence of a leak, or a leak which is significantly large, in order that further action is taken before the vacuum system is reverted to the normal use state.

[138] In embodiments, the method may comprise the step of turning the vacuum system OFF after the leak detection state has stopped.

[139] In embodiments, the step of recording data corresponding to the pressure of the process chamber may be computer-implemented. In embodiments, one or more of the steps of: actuating the leak detection state; stopping the leak detection state; actuating the vacuum system to meet the one or more minimum operating conditions; operating the valve of the vacuum system; or inputting information into the vacuum system may be computer-implemented.

[140] In embodiments, the method may include the step of detecting one or more conditions of the vacuum system in normal use and monitoring the one or more conditions of the vacuum system in normal use. For example, the method may include the steps of detecting and monitoring the load or flow rate of the vacuum pump during normal use and record changes (e.g. increases) over time.

[141] In embodiments, the method may include the step of prompting a transition to the leak detection state of the vacuum system dependent on said one or more monitored conditions. For example, the method may include the step of prompting a manual or automatic transition to the leak detection state if the load of the vacuum pump during normal use exceeds, meets or crosses a set leak-indicative threshold or increases by a set delta.

[142] In other words, the method may include a number of leak screening steps in which the need for a leak detection cycle (i.e. whether a transition to the leak detection state should be prompted) is monitored. [143] In embodiments, the method may comprise the step of monitoring the required load of the vacuum pump to produce a pressure in the process chamber. In embodiments, the method may comprise the step of prompting a transition to the leak detection state when the required load of the vacuum pump meets a leak-indicative threshold.

[144] In a further aspect, the present invention provides a computer-readable medium comprising instructions which, when executed by a computer, provides the method described above.

[145] In embodiments, the instructions may include instructions to monitor the actual speed and/or maximum speed of the vacuum pump during a normal use state of the vacuum system.

[146] In embodiments, the instructions may include instructions to calculate whether the load of the vacuum pump changes over a set time period and to prompt a transition to the leak detection state of the vacuum system if the calculated load change meets a leak-indicative threshold.

[147] In a further aspect, the present invention provides vacuum system having a leak detection state for self-detecting a leak of the vacuum system, the vacuum system comprising: a process chamber having a fluid volume to be evacuated; a vacuum pump configured to evacuate the process chamber; at least one sensor configured to measure one or more conditions of the vacuum system; a recorder to record the measured conditions; and a controller; and wherein, outside the leak detection state, the controller is configured to prompt a transition to the leak detection state when a recorded conditions meets a leak-indicative threshold.

[148] In embodiments, the recorder may be configured to monitor the work rate, e.g. load and/or flow rate, of the vacuum pump during a normal use state and record changes (e.g. increases) in flowrate over time. In embodiments, the controller may be configuration to prompt a manual or automatic transition to the leak detection state of the vacuum system dependent on the one or more monitored conditions. For example, the controller may be configured to prompt a transition to the leak detection state if the work rate of the vacuum pump during normal use meets a set leak-indicative threshold or increases by a set delta.

[149] In a further aspect, the present invention provides a method of self-detecting a leak of the vacuum system of the preceding aspect, comprising the steps of detecting one or more conditions of the vacuum system during normal use of the vacuum system; monitoring data corresponding to the one or more detected conditions; and prompting a transition to the leak detection state dependent on the one or more monitored conditions.

[150] In embodiments, a said condition may be the required load of the vacuum pump to produce a pressure in the process chamber and the method may further comprise the step of prompting a transition to the leak detection state when the required load of the vacuum pump meets a leak-indicative threshold.

Clauses

The invention is further described in the following clauses.

1 . A vacuum system having a leak detection state, the vacuum system comprising: a process chamber having a fluid volume to be evacuated; a vacuum pump configured to evacuate the process chamber; at least one pressure sensor configured to measure the pressure within the process chamber; and a recorder programmed to record the pressure measured within the process chamber; wherein, in a leak detection state, the evacuated process chamber is isolated and the recorder is programmed to record data corresponding to the pressure measured within the evacuated process chamber over time; and wherein the vacuum pump is configured to evacuate the process chamber prior to the leak detection state and during normal use of the vacuum system. The vacuum system of clause 1 , wherein the recorder is programmed to calculate a leak rate of the process chamber. The vacuum system of clause 1 or clause 2, wherein the recorder is programmed to record when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded. The vacuum system of clause 3, the vacuum system further comprising a controller; wherein the controller is programmed to end the leak detection state when the recorder records that at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded. The vacuum system of any preceding clause, comprising a valve arranged between the process chamber and the vacuum pump and configured to selectively isolate the process chamber; wherein the valve is operable to close in the leak detection state. The vacuum pump of any preceding clause, wherein the vacuum system is configured to enter the leak detection state only if the vacuum pump reaches one or more minimum operating conditions. The vacuum system of any preceding clause, wherein the vacuum system is configured to enter the leak detection state only if the vacuum pump evacuates the process chamber within a pre-set maximum time period. The vacuum system of any preceding clause, wherein in the leak detection state the vacuum pump operates at an idle speed or substantially at a stop. A method of determining the extent of a leak of a vacuum system, comprising the steps of: i. providing a vacuum system in accordance with any of clause 1 to 9; ii. evacuating the process chamber of the vacuum system using the vacuum pump; and

T1 iii. subsequently actuating a leak detection state of the vacuum system including: a. isolating the evacuated process chamber; and b. recording data corresponding to the pressure of the process chamber.

10. The method of clause 9, comprising the further step of calculating a leak rate of the process chamber of the vacuum system.

11. The method of clause 9 or clause 10, comprising the further step of recording when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded.

12. The method of any of clauses 9 to 11 , comprising the further step of automatically ending the leak detection state when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded.

13. The method of any of clauses 9 to 12, wherein the step of isolating the process chamber is only carried out if the vacuum pump reaches one or more minimum operating conditions.

14. The method of any of clauses 9 to 13, wherein the step of isolating the process chamber is only carried out if the preceding step of evacuating the process chamber is completed within a pre-set maximum time period.

15. A computer-readable medium comprising instructions which, when executed by a computer, provides the system of any of clauses 1 to 8, and/or carries out the method of any of clauses 9 to 14.

[151 ] For the avoidance of doubt, features of aspects and/or embodiments described herein may be combined, and still fall within the scope of the present invention.

Brief Description of Figures [152] Preferred features of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[153] Figure 1 shows a flow diagram of steps carried out prior to and throughout a leak detection state of a vacuum system.

[154] Figure 2 shows a graph plotting a series of example leak detection results.

[155] Figure 3 shows a flow diagram of steps carried out prior to and throughout a leak detection state of a vacuum system.

Detailed Description

[156] Figure 1 shows a flow diagram illustrating operation of a vacuum system of the present invention. The vacuum system comprises: a process chamber, i.e. a chamber in which a normal use vacuum process typically takes place; a vacuum pump (for example, a screw-type vacuum pump); and at least one pressure sensors for monitoring the pressure of the process chamber.

[157] The vacuum system has a leak detection state and a normal use state. The vacuum pump of the vacuum system is configured to evacuate the process chamber of the vacuum system both prior to the leak detection state and during the normal use state. In other words, no dedicated leak detection secondary or auxiliary pump is required to evacuate the process chamber prior to the leak detection state.

[158] In the leak detection state, which is discussed in greater detail below, the evacuated process chamber of the vacuum system is isolated and the recorder of the vacuum system subsequently records the pressure measured by the or each pressure sensor over time in order to determine whether a leak is present in the process chamber. If a leak is present, gas will enter the process chamber through the (or each) leak and, as a result, the pressure within the process chamber will rise over time. Conversely, if a leak is not present, the pressure within the process chamber will remain substantially constant over time. [159] Thus, the detection and recording of pressure changes within the pressure chamber over time can indicate whether a leak is present or not, whether a pressure change is the result of outgassing within the pressure chamber, or whether a pressure change is the result of a combination of a leak and outgassing within the process chamber.

[160] The recording and calculation is carried out by the recorder of the vacuum system which is programmed accordingly. Thus, the recording of data corresponding to the pressure within the process chamber over time is automatic. In other words, user-initiated actions are not required to monitor and record data corresponding to the pressure measured within the process chamber over time.

[161 ] Referring still to Figure 1 , when the vacuum system is started 1 , a decision 2 is made as to whether or not a Pre-purge phase 3 is to be carried out. In the Pre-purge phase 3, the vacuum pump is run with the aim of meeting one or more minimum operating conditions of the vacuum pump. For example, the vacuum pump may run most efficiently at a minimum operating temperature or speed. For example, the Prepurge phase is carried out if the temperature of the vacuum system including the vacuum pump, or part of it is at or below 5°C. In another example, the Pre-purge phase is carried out if the process to be carried out under vacuum contains a substantial amount of water vapour.

[162] If a decision 2 is made not to activate the Pre-purge phase 3, the vacuum system progresses immediately to the Vacuum Control phase 5, described below. The decision 2 as to whether or not to enter the Pre-purge phase 3 may be autonomously made by the recorder.

[163] The vacuum system includes a valve configured to isolate the process chamber, including to substantially prevent fluid communication between the vacuum pump and the process chamber.

[164] In the Pre-purge phase 3, the valve is closed to isolate the process chamber. The valve is opened if the one or more minimum operating conditions 4 are met and the vacuum system progresses to the Vacuum Control phase 5. [165] Conversely, if a minimum operating condition is not met 4, the vacuum system does not progress to the Vacuum Control phase 5. A user may be alerted 12 to the outcome of the Pre-purge phase 3, particularly if a minimum operating condition is not met 4.

[166] In the Vacuum Control phase 5, the vacuum pump is actuated to evacuate the process chamber. A full or partial vacuum may be produced within the process chamber, depending on the use of the vacuum system. In this example, the vacuum pump is configured to produce a rough vacuum, i.e. a pressure of 0.1 to 1000 mbar, within the process chamber. The vacuum pump is operated at a maximum allowed speed during the Vacuum Control phase 5 in order to evacuate the process chamber is quickly as possible. However, the maximum allowed speed is dependent on the type of vacuum pump and operating conditions of the vacuum pump. The vacuum system includes a number of sensors configured to detect one or more of temperature of the vacuum pump, motor current and/or electrical supply to the vacuum pump. Therefore, if an abnormal value is measured, the maximum speed of the vacuum pump may be reduced, or the vacuum pump may be disabled until the issue is resolved.

[167] The Vacuum Control phase 5 is actuated for a pre-set maximum period of time so that, in the event a major leak is present in the process chamber, the vacuum pump does not attempt to evacuate the process chamber indefinitely. Manual intervention is thus not required should the vacuum pump fail to evacuate the process chamber.

[168] If a valve is left open in error, for example, the vacuum pump will likely not overcome the resulting leak and so the process chamber will not be evacuated in the pre-set time period If the process chamber is not evacuated within the pre-set maximum period of time, the user may be alerted 13 to this in order that appropriate action may be taken to resolve the issue.

[169] If the process chamber is evacuated 6 during the Vacuum Control phase within the maximum set period, a decision 7 is made as to whether the vacuum system is to enter the Leak Detection state 10, or whether the vacuum system is to progress to a normal use state 8. The decision 7 as to whether or not the enter the Leak Detection state 10 may be made autonomously by the recorder according to a test schedule, for example.

[170] It is envisaged, for example, that the recorder may monitor one or more conditions of the vacuum system and prompt a transition (via decision 7) to the Leak Detection state 10 depending on the monitored conditions. This may be an unscheduled leak detection test. For example, the recorder may be configured to monitor the work rate of the vacuum pump required to achieve a particular pressure in the process chamber during normal use. Over a time period, the recorder may calculate that the work rate to achieve the same pressure in the process chamber increases (meaning the vacuum pump is having to work harder). If that is the case, a transition to the Leak Detection state 10 may be prompted by the controller. Thus, the vacuum system may substantially continuously undertake Decision 7 during normal use, or at relatively frequent intervals, as well as or instead of a scheduled Leak Detection test schedule.

[171 ] If a decision is made to progress to the normal use state 8, a leak detection test is not carried out and the vacuum pump continues to evacuate the process chamber for a normal use process. During the Vacuum Control phase 5, the valve is open so that the vacuum pump may evacuate the process chamber. Should a decision be made 7 to progress to a normal use state 8, the valve remains open so that evacuation of the chamber may continue. Any process or use of the vacuum system which is not primarily directed to the detection of a leak of the process chamber, for example, may be carried out in the normal use state 8.

[172] In the embodiment of Figure 3, the vacuum system comprises a leak screening function 15. In the leak screening function 15 monitors and detects the potential need for a transition to the leak detection state. The leak screening function 15 is active during the normal use state 8 of the vacuum system and allows data indicative of a leak to be identified and automatically acted upon, if necessary.

[173] In the normal use state 8, one or more conditions of the vacuum system are detected and monitored. For example, the required load of the vacuum pump to produce a pressure in the process chamber is detected and monitored. If data corresponding to the one or more monitored conditions is leak-indicative, a transition to the Leak Detection State 10 is prompted. Prompting of the Leak Detection State 10 may be automatic, e.g. the vacuum system stops the normal use process at an earliest juncture and then enters the Leak Detection State 10.

[174] In another example, the vacuum system may end an ongoing normal use process once leak indicative data is collected, and the vacuum system may be restarted 1 and a decision to enter the Leak Detection State 10, with or without a PrePurge Phase 3, may be prompted from that restart. Alternatively, the vacuum system may automatically substantially immediately enter the Leak Detection State 10, via decision 7, from the normal use state 8 when leak indicative data is collected.

[175] Referring back to Figure 1 , in the Leak Detection state 10, if triggered, the valve is first closed so that the evacuated process chamber is isolated from the vacuum pump and from the exterior of the process chamber.

[176] The vacuum pump then enters a Run Down phase wherein the vacuum pump slows to an idle speed or substantially to a stop.

[177] Simultaneously with, or following, the Run Down phase of the vacuum pump the or each pressure sensor measures the pressure within the process chamber. The recorder of the vacuum system records data corresponding to the pressure measured within the process chamber, including the pressure reached when the process chamber was evacuated, and time elapsed since the Leak Detection state 10 began, i.e. since the process chamber was isolated.

[178] The recorder is programmed to record the data corresponding to the pressure measured within the process chamber over time and to calculate, based on that recorded data, one or more properties of a detected leak, if present. The properties of a leak may include the presence, size and/or location of the detected leak.

[179] The recorder is programmed to record when the first of a pre-set time period has elapsed and a pre-set pressure change threshold within the process chamber is reached. The pre-set time period and pre-set pressure change threshold are preprogrammed into the recorder.

[180] For example, the process chamber is evacuated to produce a first pressure (P1 ) in the Vacuum Control phase 5 and the pre-set pressure change threshold corresponds to a second pressure (P2) which is greater (i.e. a higher pressure) than the first pressure (P1 ). If, when the Leak Detection state 10 is triggered and the process chamber is isolated, the pressure within the process chamber rises from the first pressure to the second pressure within the pre-set time period to elapse, the recorder records this event and may determine that a leak is present.

[181 ] Furthermore, the recorder is programmed to stop recording data when the first of these parameters is reached. It may be that the pre-set pressure change threshold is not reached by the time the pre-set time period has elapsed, or that the pre-set pressure change threshold is reached before the pre-set time period has elapsed. In either case, the recorder nevertheless stops recording data and the Leak Detection state 10 ceases.

[182] The recorder is programmed to calculate a pressure rise rate based on the recorded pressure change within the process chamber over time. The recorder is also programmed to calculate a leak rate of the process chamber based on the volume of the process chamber and the recorded data.

[183] The vacuum system includes a controller which is programmed to stop the Leak Detection state when the recorder records that at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded. Thus, the recorder is configured to transition the vacuum system from the Leak Detection state 10.

[184] If, for example, the pre-set time period elapses and a leak is not detected, or a leak is detected which is small enough that it can be sufficiently overcome by the vacuum pump in normal use, the controller transitions the vacuum system from the Leak Detection state 10 back to the normal use state 8 of the flow diagram of Figure 1 . Alternatively, after the Leak Detection state 10 has ended, the vacuum system may be automatically turned OFF.

[185] If, for example, a leak is present and the pre-set pressure change threshold is met (or after the pre-set time period has elapsed a significant leak is recorded), one or more properties of the leak are calculated by the recorder and may be displayed to a user 14. The vacuum system may then transition to the normal use state 8, or may be turned OFF. Therefore, whether or not a leak is detected during the Leak Detection state 10, the vacuum system may be configured to transition back to a normal use state thereafter.

[186] The results of each iteration of the Leak Detection state 10 are stored in a memory of the vacuum system so that the results of each iteration of the Leak Detection state 10 can be compared.

[187] The controller is also programmed with a schedule which dictates when the Leak Detection state 10 is to be triggered so that a user does not have to manually actuate the Leak Detection state 10. The controller is also programmed with instructions as to whether or not the Pre-purge phase 3 is required prior to the Leak Detection state 10. Thus, the decisions 2, 4, 6, 7, 11 of the flow diagram of Figure 1 may be made by the controller which is pre-programmed to make those decisions.

[188] Referring to Figure 2, the results of leak detection tests, i.e. several iterations of the Leak Detection state 10 over time, are plotted so that a user may be informed of the extent of leakage of the process chamber.

[189] The vacuum system includes a user interface for the input of information onto the recorder and/or controller and for the display of information to a user. Information displayed to a user may include: a detected leak rate, optionally calculated as described above; whether or not there is a leak, as may be pre-defined in the vacuum system; and/or the characteristics (e.g. the worsening or improvement thereof) of a detected leak over time / several iterations of the leak detection state. [190] The user interface allows a user to input information corresponding to one or more properties of the process chamber and/or vacuum pump so that calculations made by the recorder are tailored to the hardware of the vacuum system. For example the volume (7) of the process chamber and the pressure to be produced within the process chamber when the process chamber is evacuated may be input so that the leak rate may be calculated by the recorder. In another example, the pre-set pressure change threshold and the pre-set time period to elapse are input so that the recorder is configured to stop recording and/or prompt the stopping of the Leak Detection state when the first of those parameters is met.

Reference Key

1 Start

2 Pre-purge Decision

3 Pre-purge Phase

4 Minimum Operating Condition Decision

5 Vacuum Control Phase

6 Evacuation Decision

7 Leak Detection Decision

8 Normal Use State

9 Off

10 Leak Detection State

11 Leak Detected Decision

12 Minimum Operating Condition Alert

13 Evacuation Alert

14 Leak Detection Alert

15 Leak Screening Function

Claims

1 . A vacuum system having a leak detection state for self-detecting a leak of the vacuum system, the vacuum system comprising: a process chamber having a fluid volume to be evacuated; a vacuum pump configured to evacuate the process chamber during normal use of the vacuum system and prior to entering a leak detection state, which leak-detection state is different to a normal use configuration; at least one pressure sensor configured to measure the pressure within the process chamber; and a recorder programmed to record the pressure measured within the process chamber; wherein, in the leak detection state, the evacuated process chamber is isolated and the recorder is programmed to record data corresponding to the pressure measured within the evacuated process chamber over time and the vacuum system is configured to identify pressure data indicative of a leak of the process chamber.

2. The vacuum system of claim 1 , wherein the recorder is programmed to calculate a leak rate of the process chamber.

3. The vacuum system of claim 1 or claim 2, wherein the recorder is programmed to record when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded; optionally, wherein the vacuum system further comprises a controller; wherein the controller is programmed to end the leak detection state when the recorder records that at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded.

4. The vacuum system of any preceding claim, comprising a valve arranged between the process chamber and the vacuum pump and configured to selectively isolate the process chamber; wherein the valve is operable to close in the leak detection state.

38 The vacuum system of any preceding claim, wherein the vacuum system is configured to enter the leak detection state only if the vacuum pump reaches one or more minimum operating conditions; and/or wherein the vacuum system is configured to enter the leak detection state only if the vacuum pump evacuates the process chamber within a pre-set maximum time period. The vacuum system of any preceding claim, including at least one sensor for detecting one or more conditions of the vacuum system during normal use of the vacuum system; and the recorder is configured to monitor data corresponding to the one or more conditions; and wherein the vacuum system comprises a controller which is configured to prompt a transition to the leak detection state dependent on the one or more monitored conditions; optionally, wherein a said condition is the required load of the vacuum pump to produce a pressure in the process chamber; and wherein the controller is configured to prompt a transition to the leak detection state when the required load of the vacuum pump meets a leak-indicative threshold. A method of determining the extent of a leak of a vacuum system, comprising the steps of: i. providing a vacuum system in accordance with any of claims 1 to 6; ii. evacuating the process chamber of the vacuum system using the vacuum pump; and iii. subsequently actuating a leak detection state which is different to a normal use configuration of the vacuum system including: a. isolating the evacuated process chamber; and b. recording data corresponding to the pressure of the process chamber and identifying data indicative of a leak of the process chamber if it is recorded. The method of claim 7, comprising the further step of calculating a leak rate of the process chamber of the vacuum system.

39 The method of claim 7 or claim 8, comprising the further step of recording when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded. The method of any of claims 7 to 9, comprising the further step of automatically ending the leak detection state when at least one of a pre-set time period has elapsed and/or a pre-set pressure change threshold is recorded. The method of any of claims 7 to 10, wherein the step of isolating the process chamber is only carried out if the vacuum pump reaches one or more minimum operating conditions. The method of any of claims 7 to 11 , wherein the step of isolating the process chamber is only carried out if the preceding step of evacuating the process chamber is completed within a pre-set maximum time period. The method of any of claims 7 to 12, comprising the further steps of detecting one or more conditions of the vacuum system during normal use of the vacuum system; monitoring data corresponding to the one or more detected conditions; and prompting a transition to the leak detection state dependent on the one or more monitored conditions; optionally, wherein a said condition is the required load of the vacuum pump to produce a pressure in the process chamber and the method further comprises the step of prompting a transition to the leak detection state when the required load of the vacuum pump meets a leak-indicative threshold. A computer-readable medium comprising instructions which, when executed by a computer, carries out the method of any of claims 8 to 13. A vacuum system having a leak detection state for self-detecting a leak of the vacuum system, the vacuum system comprising: a process chamber having a fluid volume to be evacuated; a vacuum pump configured to evacuate the process chamber; at least one sensor configured to measure one or more conditions of the vacuum system; a recorder to record the measured conditions; and a controller; and wherein, outside the leak detection state, the controller is configured to prompt

40 a transition to the leak detection state when a recorded condition meets a leakindicative threshold.