How to control a steam sterilization system

Abstract

To provide a method of controlling a steam sterilizer system.SOLUTION: The present disclosure relates to a method of controlling a steam sterilizer system comprising a boiler in which liquid water is turned into steam. Water is pumped from a container and the pumped water is passed through a degassing filter located upstream of the boiler in order to remove non-condensable gases (NCGs) dissolved in the water. The water is recirculated through the degassing filter for additional removal of NCGs, while water is prevented from flowing from the degassing filter to the boiler. Subsequently to recirculating the water through the degassing filter, at least a portion of the water is sent to the boiler. The present disclosure also relates to a control unit for performing the steps of the method, and to a steam sterilizing system comprising such a control unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for controlling a steam sterilization system. The disclosure also relates to a control unit configured to perform the steps of such a method. The disclosure further relates to a steam sterilization system comprising such a control unit. The steam sterilization system may be used, for example, in a Central Sterile Services Department (CSSD) of a hospital for processing used medical tools. [Background technology]

[0002] Microbial inactivation by steam sterilization process involves the presence of steam (moist heat) and high temperature for a period of time. During such steam sterilization process, the equipment to be sterilized must be in contact with steam and its condensate for that period of time. However, a problem with such steam sterilization process is that non-condensable gases (NCGs) may accumulate and block and hinder the complete penetration of steam into lumens such as long hoses, textile packages, and crevices on objects, thus compromising the ability of microbial inactivation at such locations. To achieve an efficient steam sterilization process, it is desirable to remove the non-condensable gases (NCGs).

[0003] NCG is primarily dissolved O2, N2, and CO2 absorbed from the atmosphere into lakes, rivers, and wells. Seasonal variations in NCG levels can occur due to different temperatures and increased stirring of the lakes as temperatures change during the spring and fall seasons.

[0004] A common method of removing NCG from water for sterilization processes is high-temperature well degassing. This involves the use of heated tanks that keep the feed water at high temperatures. As the temperature increases, the saturation of dissolved gases decreases. However, degassing does not work well if the water is not allowed enough time to heat up and allow the gases to flow out, or if the temperature is too low. Additionally, the temperature needs to be kept well below the boiling point to avoid damaging the pumps, or to even be able to pump the water out at all.

[0005] In view of the above, it should be appreciated that there is still room for improvement with respect to degassing of water used in steam sterilization processes. Summary of the Invention [Means for solving the problem]

[0006] It is an object of the present disclosure to provide a method and system that at least partially alleviates the drawbacks of the prior art. This object, as well as other objects that will become apparent hereinafter, are achieved by the method defined in claim 1. Some non-limiting exemplary embodiments are presented in the dependent claims.

[0007] Applicants have determined that the water should be passed through a degassing filter and then recirculated through the degassing filter so that the NCG content in the water can be significantly reduced before the water is fed to the boiler.

[0008] Thus, in accordance with at least one aspect of the inventive concept, there is provided a method of controlling a steam sterilization system having a boiler for converting liquid water to steam, the method comprising: - pumping the water from the vessel and passing it through a degassing filter located upstream of the boiler in order to remove non-condensable gases (NCGs) dissolved in the water; - after passing the water through the deaeration filter, recirculating the water through the deaeration filter to further remove NCGs while preventing the water from passing from the deaeration filter to the boiler; - sending at least a portion of the water to a boiler after recirculating the water through a deaeration filter; Includes.

[0009] By recirculating the water through a degassing filter, the NCG content is gradually reduced, allowing water with low or virtually no NCG content to be sent to a boiler to produce improved steam for a steam sterilizer.

[0010] The steam sterilization system may suitably comprise a valve disposed downstream of the degassing filter and upstream of the boiler. In at least some exemplary embodiments of the method, the step of sending at least a portion of the water to the boiler may include opening the valve. In other words, while recirculating the water through the degassing filter, a valve disposed in the supply line between the filter and the boiler may be controlled to close in order to prevent the water from flowing prematurely (i.e. before a sufficient amount of NCG has been removed) to the boiler. The opening and closing of the valve may be strategically controlled by a control unit of the steam sterilization system. Such a control unit provides further advantages and will be discussed in more detail later in this disclosure.

[0011] The valve in the supply line between the filter and the boiler may be conveniently referred to as the first valve. The steam sterilization system may also have other valves. For example, a recirculation line is suitably provided extending from a point downstream of the degassing filter to the container to recirculate the water. Such a recirculation line may be provided with a valve, which may be conveniently referred to as the second valve. To allow recirculation of the water through the degassing filter, the second valve may be controlled to open when the first valve is closed. When the time comes to open the first valve to send at least a portion of the water to the boiler, the second valve may be closed. However, it should be understood that the second valve need not be closed. In fact, some recirculation may be permitted at the same time as sending the water to the boiler. For example, instead of a controllable second valve, a small orifice may be provided in the recirculation line that is always open for recirculation. From the above, it should be appreciated that, according to at least one exemplary embodiment of the method, the method may include continuing to recirculate a small amount of the water that has passed through the degassing filter simultaneously with the step of sending at least a portion of the water to the boiler.

[0012] It should be understood that the concept of recirculating water through the degassing filter while preventing the water from flowing from the degassing filter to the boiler can be implemented in various ways. For example, in some exemplary embodiments, a relatively short recirculation loop can be envisaged, with or without a separate pump, in which case the water leaving the degassing filter can be returned to the filter without passing through the container. In other words, in at least some exemplary embodiments, the recirculation of water can bypass the container. However, as already indicated above, in at least some exemplary embodiments, the recirculation can be advantageously performed via the container. Thus, according to at least some exemplary embodiments, the step of recirculating water through the degassing filter can include returning the water to the container and then pumping it again to the degassing filter.

[0013] According to at least one exemplary embodiment, the step of recirculating the water through a degassing filter comprises: - recirculating the water through the filter such that the total amount of water passing through the deaeration filter before said at least a portion of the water is sent to the boiler is at least twice the amount of water that was initially present in the vessel prior to said step of pumping water from the vessel; Thus, the water is suitably recirculated "multiple times" so that all water in the container passes through the degassing filter at least twice on average. The more times the water is recirculated, the greater the amount of NCG removed from the water. Of course, the actual control of the recirculation may be based on the water volume, for example using a flow meter. However, suitably the recirculation may be time-based, i.e. a certain period of recirculation is performed, which may correspond to a certain amount of water passing through the degassing filter.

[0014] According to at least one exemplary embodiment, the step of recirculating water through the degassing filter continues until it is determined that either (i) at least a minimum period T1 of water has been circulated through the degassing filter, or (ii) at least a minimum number of cycles of water has been circulated through the degassing filter. The minimum period T1 may be determined, for example, empirically or through a look-up table, or may be calculated based on known or estimated NCG content, flow rate, water volume, etc. The minimum period T1 is appropriately selected such that a satisfactory reduction of NCG in the circulating water is achieved before the water is allowed to be sent to the boiler. If time permits, and if there is no urgent or pending request to supply water to the boiler, the recirculation may be suitably continued for a period longer than the minimum period T1 to further reduce the NCG content. If the control of the recirculation is not time-based, but instead requires the completion of a minimum number of cycles, the control of the recirculation may be performed by measuring the amount of water that has passed through the degassing filter using a flow meter. Thus, one cycle may suitably correspond to passing a volume of water through the degassing filter equivalent to the volume of water originally present in the vessel before water begins to be pumped from the vessel. In some embodiments, the volume of water passing through the degassing filter before the water is sent to the boiler is at least twice the volume of water originally present in the vessel or at least twice the volume of water originally present in the degassing circulation loop.

[0015] In addition to the above time-based and cycle-based alternatives for controlling the duration of recirculation, another possible alternative is pressure-based control, which may be suitably implemented in connection with the vacuum tank used to draw the NCG from the degassing filter, as will be described in more detail below.

[0016] According to at least one exemplary embodiment, the method includes applying a vacuum to the degassing filter with a vacuum tank to draw NCG from the water passing through the degassing filter.

[0017] Applying a vacuum to the degassing filter increases the gas removal efficiency of the degassing filter. The vacuum tank may be connected, for example, to a central vacuum structure of the sterilization system, or alternatively to a separate eductor or additional vacuum pump.

[0018] As indicated above, pressure-based control of continued recirculation may be suitably implemented. Thus, according to at least one exemplary embodiment, recirculating water through the degassing filter continues until it is determined that the rate of pressure change in the vacuum tank falls below a predetermined threshold.

[0019] Since vacuum tanks are typically provided with pressure sensors, the use of such pressure sensors may be useful to monitor changes in gas content during recirculation of the water. In particular, it will be appreciated that at the start of the degassing process, the water will initially have a high NCG content, and a fairly rapid pressure rise in the tank can be expected early in the degassing (recirculation) process. However, if the water is fully degassed, continued recirculation should not result in a pressure rise. Thus, by monitoring the rate of pressure change, the control unit may identify when the recirculated water is sufficiently degassed.

[0020] It should be understood that while it may be convenient to measure the rate of pressure change in a vacuum tank as described above, such a rate of pressure change may alternatively or additionally be measured elsewhere. Indeed, regardless of whether a vacuum tank or some other device for creating a vacuum is used, the rate of pressure change may be measured in any suitable closable volume that may be placed in gas communication with the degassing filter. Thus, in general, according to at least one exemplary embodiment, the step of recirculating water through the degassing filter continues until it is determined that the rate of pressure change in the closable volume in fluid communication with the degassing filter falls below a predetermined threshold.

[0021] A pressure sensor may be provided in any such volume in fluid communication with the degassing filter, whether it is the aforementioned vacuum tank or another volume. By fluidly connecting the volume to the dry side of the filter and then closing the volume during measurement, a pressure value may be obtained from the pressure sensor. As gas molecules pass through the degassing filter, the pressure in the volume increases. If there is already pressure in the volume (e.g., no vacuum or low vacuum), there will be no or little transport of gas molecules.

[0022] It should be understood that while the above time-based, cycle-based, and pressure-based control strategies have been presented as various possible alternatives, combinations of these are also possible. For example, another possibility is to control recirculation based on a combination of the rate of pressure change and a minimum period T1, which would provide a more robust control strategy.

[0023] Some further discussion now follows regarding the use of vacuum tanks. Specifically, various tests may be performed in connection with such vacuum tanks. One such test may be a leak test to ensure that the vacuum provided functions satisfactorily. Another such test is a performance test.

[0024] Thus, in accordance with at least one exemplary embodiment, a method includes: - performing a vacuum leak test after recirculating the water through the deaeration filter but before sending said portion of the water to the boiler; The vacuum leak test includes: - during a first duration, stabilizing the water, and then - determining the pressure in the vacuum tank during a second duration, and then determining that the leak test has passed if any pressure increase in the vacuum tank during the second duration is less than the first predetermined pressure change; This is executed by:

[0025] Further, in accordance with at least one exemplary embodiment, the method further comprises: - upon determining that the leak test has been passed, performing a performance test after or while sending said at least a portion of the water to the boiler; The performance test includes: - supplying the container with fresh water that has not been previously deaerated, and then - recording the starting pressure in the vacuum tank and then - recirculating the fresh water supply through a degassing filter and then - recording the stop pressure in the vacuum tank and then - determining that the degassing performance is satisfactory if the difference between the stop pressure and the start pressure exceeds a second predetermined pressure change; This is executed by:

[0026] The above leak and performance tests are clearly beneficial in reducing the risk of erroneous control and degassing. The leak and / or performance tests may form part of a separate maintenance cycle or may be integrated into the production cycle. Any leaks may make degassing more difficult and require additional vacuum support, so that the above pressure-based recirculation control may become ineffective. The failure of the pressure to rise in the vacuum tank during the first degassing of previously undegassed water may indicate that the filter has failed, worn out or become clogged and needs to be replaced.

[0027] As an alternative or complement to the aforementioned control strategies (time-based, water volume-based, and / or pressure-based), another control strategy may be to monitor the actual NCG content in the vessel. Thus, according to at least one exemplary embodiment, the method includes: - monitoring the NCG content in the container; - when the NCG content falls below a predefined threshold value, proceeding from said step of recirculating the water through the degassing filter to said step of sending at least a portion of the water to a boiler; Thus, another method is provided to avoid premature filling of the boiler with water (water with high NCG content). Monitoring the NCG content of the water in the vessel can be achieved, for example, by using a Total Dissolved Gas (TDG) in-situ sensor in the outlet path from the vessel to the degassing filter. Such a TDG sensor can be suitably placed in the outlet path between the circulation pump and the degassing filter. Another possibility is to use a single gas sensor, for example an oxygen gas (O2) sensor. Since in fresh water it can be expected that there is a certain relationship between the amounts of O2, N2, CO2, a sensor measuring the amount of only one of these gases may be sufficient for the estimation / calculation of the total NCG content.

[0028] As explained above, various control strategies may exist to mitigate the risk of prematurely delivering water to the boiler, and in particular to mitigate the risk of filling the boiler with water that has too high an NCG content. However, there may be other considerations for determining when it is OK to let water into the boiler. This is reflected in at least one exemplary embodiment, according to which a method includes: - monitoring the liquid level in the boiler; - when the liquid water level in the boiler reaches or falls below a predetermined level, proceeding from said step of recirculating the water through the deaeration filter to said step of sending at least a portion of the water to the boiler; Thus, by monitoring the liquid level in the boiler, the control unit can determine whether sufficient water remains to generate steam for future sterilization of items to be sterilized in a sterilizer downstream of the boiler. Thus, the boiler may be suitably provided with a water level control system including a water level sensor that detects when the water level in the boiler becomes low, for example as a result of water in the boiler being converted to steam by a heating element.

[0029] According to at least one exemplary embodiment, a method includes: - determining whether the water level in the boiler reaches or falls below said predetermined water level within a predetermined time period T2; - preventing fresh water from being fed to the vessel until said predetermined water level in the boiler is reached and sending deaerated water from the vessel to the boiler to refill it; - supplying fresh water to the container after said step of preventing fresh water from being supplied; Supplying fresh water to the vessel will result in an increase in NCG content when mixed with any deaerated water already present in the vessel. Therefore, if there is a need to refill the boiler in the near future, it is advantageous to prevent fresh water from being supplied to the vessel. The predetermined period T2 may be suitably calculated based on the current situation and may vary from time to time. If the predetermined period T2 is short, this may indicate that refilling of the boiler is required soon, and it may be advantageous to suspend supplying fresh water to the vessel until refilling of the boiler is completed, thus using only the deaerated water already present in the vessel. This may be particularly relevant if the volume of the vessel is significantly larger than the amount of refill water normally sent to the boiler, and the water in the vessel can be used for multiple batches of refill and steam generation operations. Conversely, it will be appreciated that if the predetermined period T2 is relatively long, there may be enough time to fill the vessel with fresh water and recirculate the water through a deaerated filter to sufficiently reduce the NCG content before it is expected that refilling of the boiler is required. For example, when using time-based control, fresh water may be adequately supplied to the container if the period T2 is longer than the sum of the time it takes to fill the container and the minimum period T1 for recirculating the water through the degassing filter. Of course, the control unit may be configured to calculate the amount of fresh water that may be supplied to the container based on the period T2 and the period T1 and the fresh water supply rate, so that the supplied amount of fresh water can be degassed in a timely manner within the period T2 (if it takes too long to fill completely).

[0030] It should be understood that the supply of fresh water to the container may be directly from the fresh water conduit to the container. However, another possible option is to add fresh water upstream or downstream of the container in the degassing structure. For example, fresh water may be added to the above-mentioned recirculation path interconnecting the downstream point of the degassing filter and the container, or fresh water may be added to the outlet path interconnecting the outlet of the container and the degassing filter. If a pump is provided in the outlet path, fresh water may be added to the outlet path upstream or downstream of the pump. It should therefore be understood that fresh water may be supplied to the container by putting it in the water recirculation path in the degassing structure at any suitable place where the water reaches the container during the degassing cycle.

[0031] Similar to the above-mentioned timing for preventing fresh water from being provided to the vessel, in accordance with at least one exemplary embodiment, the method further comprises: - determining whether the boiler requires additional water within a given period of time, in particular based on at least one of the water level in the boiler and the process stage of the steam sterilization system; - preventing fresh water from being supplied to the vessel if the boiler requires additional water within a given period of time; The predetermined period of time may correspond to the above-mentioned predetermined period of time T2, for example.

[0032] The idea regarding the timing of the supply of fresh water to the container is also reflected in the following. Thus, according to at least one exemplary embodiment, the method further comprises: - preventing fresh water from being fed to the container while the water is recirculated through the degassing filter, and then - sending at least a portion of said water to a boiler, and then - providing the container with fresh water; If the vessel is filled with approximately the same amount of water that will later be fed to the boiler, the above steps may be suitably repeated each time a new batch of water is evaporated in the boiler.

[0033] According to at least one exemplary embodiment, a method includes: - monitoring the water level in the vessel; - controlling the supply of fresh water to the vessel based on the current water level in the vessel; Specifically, controlling the supply of fresh water to the vessel is based on whether the current water level in the vessel is expected to be sufficient for the next batch of water to be supplied to the steam generator. By monitoring the water level in the vessel, unnecessary dilution can be avoided. The control unit can be suitably configured to determine whether the current water level is sufficient for another batch of steam generation in the boiler, and if so, the supply of fresh water to the vessel can be prevented. In other words, since fresh water increases the NCG content in the vessel and further requires circulating the water through a degassing filter, it may be better to utilize already degassed water available in the vessel before supplying fresh water to the vessel.

[0034] According to at least one exemplary embodiment, the step of controlling the supply of fresh water to the vessel based on a current water level in the vessel comprises: - supplying fresh water to the container when the water level falls below a certain level; As will be appreciated from the above, supplying water to the vessel when the water level is low is advantageous as it prevents the dissolved gas levels from building up.

[0035] Preventing fresh water from being supplied to the vessel may suitably be accomplished by a further valve, a vessel fill valve that can be opened or closed. Such a vessel fill valve may be controlled by the control unit based on a water level sensor input (e.g., input from one or more sensors monitoring the water level in the vessel). However, in at least some alternative exemplary embodiments, the vessel may be provided with a float valve in place of the vessel fill valve and water level sensor.

[0036] According to at least one exemplary embodiment, the method further comprises: - supplying fresh water to the vessel in response to a decision not to supply deaerated water to the boiler during at least a first time period T3; - preventing fresh water from being supplied to the vessel in response to a determination that there is a need to supply water to the boiler within a second time period T4; In embodiments where the method also employs the time-based control and the predetermined period T1 described above, the first period T3 will typically be longer than the period T1 since, in addition to the recirculation period (T1), time also elapses during the actual supply of fresh water to the vessel. However, in at least some exemplary embodiments, the second period T4 may correspond to the predetermined period T2 described above, i.e., the predicted period for the water to fall below a predetermined water level in the boiler.

[0037] According to at least one exemplary embodiment, a method includes: - after said step of sending at least a part of the water to the boiler, blocking the sending of water to the boiler; - Supplying the container with fresh water and then repeating said steps of pumping and recirculating water through the deaeration filter while preventing water from flowing from the deaeration filter to the boiler; In other words, according to this exemplary embodiment, control of the fresh water supply may advantageously be based on completion / end of filling of the boiler, for example immediately after (within a short period of time after) filling the boiler.

[0038] In other exemplary embodiments, the vessel may be associated with a predefined low water level and a predefined high water level. In such an embodiment, if the NCG level is assumed to be low due to degassing, then fresh water is not typically added to the vessel when the current water level is between said predefined low water level and said predefined high water level. Instead, water already present in the vessel is used to fill the boiler with degassed water if the boiler may require it. This may be done as long as there is no risk of running out of degassed water in the vessel. When the current water level falls below said predefined low water level, fresh water may again be supplied to the vessel. This will increase the NCG content in the vessel and a new degassing / circulation phase will be initiated. This is at least partially reflected in the following exemplary embodiments. According to at least one exemplary embodiment, the method comprises: - after said step of sending at least a portion of the water to the boiler, operating the boiler to generate steam; - monitoring the water level in the vessel; - preventing fresh water from being supplied to the container as long as the water level in the container is equal to or greater than a predetermined water level; - after said step of operating the boiler to generate steam, as long as the water level in the vessel is equal to or greater than said predetermined water level, sending a further portion or portions of water to the boiler and operating the boiler to generate steam; Includes.

[0039] Although having a clear threshold for supplying fresh water to the vessel in the form of said predetermined low water level may be advantageous and convenient, the control unit may be suitably configured to handle other scenarios as well. For example, the control unit may suitably determine that water may be supplied even if the current water level has not yet fallen to said predetermined low water level, i.e. if the current water level is still between said predetermined low water level and said predetermined high water level. However, this is done proactively if the control unit determines that there is sufficient time to degas the supplied fresh water before the water has to be sent to the boiler.

[0040] According to at least another aspect of the present disclosure, there is provided a control unit configured to perform the steps of any of the aforementioned methods (including any exemplary embodiments thereof), the control unit comprising: - controlling the pumping of the steam sterilization system by controlling the pumping of the water from the container; - controlling a first valve of the steam sterilization system to selectively block or enable the water from the degassing filter to the boiler; - optionally controlling further valves of the steam sterilization system to selectively block or enable the supply of fresh water to the container; The apparatus is configured to execute the following steps:

[0041] The advantages provided by the control unit are largely similar to those provided by the method disclosed hereinbefore (including its exemplary embodiments).

[0042] The control unit may include a microprocessor, a microcontroller, a programmable digital signal processor, or another programmable device. The control unit may additionally or alternatively include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the control unit includes a programmable device such as a microprocessor, microcontroller, or programmable digital signal processor as described above, the processor may further include computer executable code for controlling the operation of the programmable device. The control unit is preferably configured for use with a steam sterilization system and is provided with electronic instructions for performing and controlling any of the methods described herein.

[0043] According to at least yet another aspect of the inventive concept, there is provided a steam sterilization system comprising a control unit according to the above aspect (including any exemplary embodiment thereof) and further comprising a boiler and a sterilization chamber, the advantages provided by said steam sterilization system being largely similar to those provided by the control unit and method disclosed hereinbefore (including exemplary embodiments thereof) disclosed hereinbefore.

[0044] Below, several additional aspects of the disclosure are presented.

[0045] Aspect 1: 1. A method for controlling a steam sterilization system having a boiler that converts liquid water to steam, the method comprising: - pumping water from the vessel and passing it through a degassing filter located upstream of the boiler in order to remove non-condensable gases (NCGs) dissolved in the water before the water reaches the boiler; - monitoring the NCG content and / or water level in the container; - controlling the supply of fresh water to the vessel based on the current NCG content and / or the current water level in the vessel, respectively; Includes.

[0046] Aspect 2: 2. The method of embodiment 1, comprising: - supplying fresh water to the container if the NCG content is equal to or greater than a predefined threshold and preventing the supply of fresh water if the NCG content is below a predefined threshold, and / or - supplying fresh water to the container when the water level is below a predetermined level and preventing the supply of fresh water to the container when the water level is above a predetermined level; Includes.

[0047] Aspect 3: 3. The method according to any one of aspects 1 or 2, comprising: - after passing the water through the deaeration filter, recirculating the water through the deaeration filter to further remove NCGs while preventing the water from passing from the deaeration filter to the boiler; - sending at least a portion of the water to a boiler after recirculating the water through a deaeration filter; Includes.

[0048] Aspect 4: 5. The method of claim 4, wherein the step of recirculating water through a degassing filter comprises: - recirculating the water through the filter such that the total amount of water passing through the deaeration filter before said at least a portion of the water is sent to the boiler is at least twice the amount of water that was initially present in the vessel prior to said step of pumping water from the vessel; Includes.

[0049] Aspect 5: A method according to any one of aspects 3 to 4, comprising: - monitoring the NCG content in the container; - when the NCG content falls below a first predetermined threshold, proceeding from said step of recirculating the water through the degassing filter to said step of sending at least a portion of the water to a boiler; Includes.

[0050] Aspect 6: A method according to any one of aspects 3 to 5, comprising: - monitoring the liquid level in the boiler; - when the liquid water level in the boiler reaches or falls below a predetermined level, proceeding from said step of recirculating the water through the deaeration filter to said step of sending at least a portion of the water to the boiler; Includes.

[0051] Aspect 7: 7. The method of embodiment 6, comprising the steps of: - determining when the water level in the boiler reaches or falls below said predetermined water level within a predetermined period of time; - preventing fresh water from being fed to the vessel until said predetermined water level in the boiler is reached and sending deaerated water from the vessel to the boiler to refill it; - supplying fresh water to the container after said step of preventing fresh water from being supplied to the container; Includes.

[0052] Aspect 8: A method according to any one of aspects 3 to 7, comprising: - after said step of sending water to the boiler, preventing water from being sent to the boiler; - providing the container with fresh water; repeating said steps of pumping and recirculating water through the deaeration filter while preventing water from flowing from the deaeration filter to the boiler; Includes.

[0053] Aspect 9: A method according to any one of aspects 1 to 8, wherein the steam sterilization system includes a valve positioned downstream of the degassing filter and upstream of the boiler, and sending the at least a portion of the water to the boiler includes opening the valve.

[0054] Aspect 10: The method according to any one of aspects 3 to 9, wherein the step of recirculating water through a degassing filter comprises: - pumping the water back into the container and then again through the degassing filter; Includes.

[0055] Aspect 11: The method according to any one of aspects 3 to 10, further comprising continuously recirculating a small amount of the degassing filtered water simultaneously with the sending of water to the boiler.

[0056] Aspect 12: A method according to any one of aspects 1 to 11, comprising: - applying a vacuum to the degassing filter by means of a vacuum tank to draw out the NCG from the water passing through the degassing filter; Includes.

[0057] Aspect 13: The method of embodiment 12 according to embodiment 3, wherein the step of recirculating the water through the degassing filter is continued until it is determined that the rate of pressure change in the vacuum tank is below a predetermined threshold.

[0058] Aspect 14: The method of any one of aspects 3-13, wherein the step of recirculating the water through the degassing filter is continued until determining either: (i) that the water has been circulated through the degassing filter for at least a minimum period of time T1; or (ii) that the water has been circulated through the degassing filter for at least a minimum number of cycles.

[0059] Aspect 15: A control unit configured to perform the steps of the method according to any one of aspects 1 to 14, the control unit comprising: - controlling the pumping of the steam sterilization system by controlling the pumping of the water from the container; - optionally controlling a first valve of the steam sterilization system to selectively block or enable water from the degassing filter to the boiler; - controlling a second valve of the steam sterilization system to selectively block or enable the supply of fresh water to the container; The apparatus is configured to execute the following steps:

[0060] Aspect 16: The steam sterilization system comprises the control unit of embodiment 15, and further comprises a boiler and a sterilization chamber.

[0061] In general, all terms used in the claims shall be interpreted according to their ordinary meaning in the art, unless expressly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." shall be openly interpreted as referring to at least one instance of the element, apparatus, component, means, step, etc., unless expressly stated otherwise. The steps of any method disclosed herein need not be performed in the exact order disclosed, unless expressly stated. Further features and advantages of the present invention will become apparent upon review of the appended claims and the following description. Those skilled in the art will recognize that different features of the present invention may be combined to create embodiments other than those described below, without departing from the scope of the inventive concept. The present invention provides, for example, the following items. (Item 1) 1. A method for controlling a steam sterilization system having a boiler that converts liquid water to steam, comprising: pumping water from a vessel and passing the water through a degassing filter located upstream of the boiler to remove non-condensable gases (NCGs) dissolved in the water; recirculating the water through the degassing filter after the water has passed through the degassing filter to further remove NCG while preventing water from passing from the degassing filter to the boiler; sending at least a portion of the water to the boiler after recirculating the water through the degassing filter; The method includes: (Item 2) The step of recirculating the water through the degassing filter comprises: recirculating the water through the degassing filter such that a total amount of water passing through the degassing filter before the at least a portion of the water is sent to the boiler is at least twice the amount of water that was originally in the vessel prior to the step of pumping water from the vessel; The method according to the above item, comprising: (Item 3) The method of any one of the preceding claims, wherein the step of recirculating the water through the degassing filter is continued until determining either: (i) that the circulation of the water through the degassing filter has occurred for at least a minimum period of time T1; or (ii) that the circulation of the water through the degassing filter has been completed for at least a minimum number of cycles. (Item 4) monitoring the liquid water level in the boiler; proceeding from the step of recirculating the water through the degassing filter to the step of directing at least a portion of the water to the boiler when the liquid water level in the boiler reaches or falls below a predetermined level; The method according to any one of the above items, comprising: (Item 5) Determining that the water level in the boiler has reached or fallen below the predetermined water level within a predetermined period T2; preventing fresh water from being supplied to said vessel until said predetermined water level in said boiler is reached and delivering degassed water from said vessel to said boiler to refill said boiler; supplying fresh water to the container after the step of preventing fresh water from being supplied; and The method according to any one of the above items, comprising: (Item 6) preventing fresh water from being supplied to said container while water is recirculated through said degassing filter; and thereafter directing at least a portion of said water to said boiler; and thereafter providing fresh water to said vessel; The method according to any one of the preceding items, further comprising: (Item 7) monitoring the water level in the vessel; controlling the supply of fresh water to the vessel based on the current water level in the vessel; The method according to any one of the above items, comprising: (Item 8) 4. The method of claim 3, further comprising: providing fresh water to the vessel when the water level falls below a predetermined level; The method according to any one of the above items, comprising: (Item 9) supplying fresh water to the vessel in response to a determination not to supply deaerated water to the boiler during at least a first time period T3; In response to determining that there is a need to supply water to the boiler within a second time period T4, preventing fresh water from being supplied to the vessel; and The method of any one of the preceding claims, further comprising at least one of the following: (Item 10) preventing water from being delivered to the boiler after the step of delivering at least a portion of the water to the boiler; providing fresh water to said vessel; and thereafter repeating the steps of pumping and recirculating water through the degassing filter while preventing water from flowing from the degassing filter to the boiler; The method according to any one of the above items, comprising: (Item 11) after the step of directing at least a portion of the water to the boiler, operating the boiler to generate steam; monitoring the water level in the vessel; preventing fresh water from being supplied to the container as long as the water level in the container is equal to or greater than a predetermined water level; after the step of operating the boiler to generate steam, directing further portions or portions of the water to the boiler and operating the boiler to generate steam so long as the water level in the vessel is equal to or greater than the predetermined water level; The method according to any one of the above items, comprising: (Item 12) applying a vacuum to the degassing filter with a vacuum tank to draw out NCG from the water passing through the degassing filter; The method according to any one of the above items, comprising: (Item 13) 2. The method of claim 1, wherein the step of recirculating the water through the degassing filter is continued until it is determined that a rate of pressure change within a closable volume in gaseous communication with the degassing filter falls below a predetermined threshold. (Item 14) A control unit configured to carry out the steps of the method according to any one of the preceding items, controlling the pumping of water from the container by controlling a pump of the steam sterilization system; controlling a first valve of the steam sterilization system to selectively block or enable water from being passed from the degassing filter to the boiler; Optionally, controlling a further valve of the steam sterilization system to selectively block or enable the supply of fresh water to the container; A control unit configured to execute the following: (Item 15) A steam sterilization system comprising the control unit according to any one of the preceding items, and further comprising a boiler and a sterilization chamber. (Summary) The present disclosure relates to a method for controlling a steam sterilization system with a boiler for converting liquid water to steam. Water is pumped from a container and passed through a degassing filter located upstream of the boiler to remove non-condensable gases (NCGs) dissolved in the water. The water is recirculated through the degassing filter to further remove NCGs while preventing the water from flowing from the degassing filter to the boiler. After recirculating the water through the degassing filter, at least a portion of the water is sent to the boiler. The present disclosure also relates to a control unit for carrying out the steps of the method, and a steam sterilization system comprising such a control unit. [Brief description of the drawings]

[0062] [Figure 1] FIG. 1 is a schematic diagram of a steam sterilization system in accordance with at least one exemplary embodiment of the present disclosure. [Diagram 2] 1 generally discloses method steps in accordance with at least one exemplary embodiment of the present disclosure. [Diagram 3] FIG. 1 is a schematic diagram of a steam sterilizer that can be used with the disclosed system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] The present disclosure will now be described more fully with reference to the accompanying drawings, in which certain aspects of the system are shown. However, the system may be embodied in many different forms and should not be construed as being limited to the embodiments and aspects set forth herein, but rather, the present embodiments are provided as examples so that the disclosure will be thorough and complete, and will fully convey the scope of the system to those skilled in the art. Thus, it should be understood that the present disclosure is not limited to the embodiments described herein and illustrated in the drawings, but rather, those skilled in the art will recognize that many changes and modifications may be made within the scope of the appended claims. Like reference numerals refer to like elements throughout this description.

[0064] FIG. 1 is a schematic diagram of a steam sterilization system 1 according to at least one exemplary embodiment. At a general level, the steam sterilization system 1 includes a container 2, a boiler 4, and a steam sterilizer 6. Water from the container 2 may be delivered to the boiler 4, which converts the delivered water into steam. The steam is then sent from the boiler 4 to the steam sterilizer 6. The steam sterilizer 6 is depicted diagrammatically as a dashed rectangle, it being understood that the present approach is not limited to the use of any particular type of steam sterilizer, but may be implemented with any suitable steam sterilizer having a sterilization chamber capable of exposing articles to be sterilized, such as medical instruments, to steam generated by the boiler 4. Examples of steam sterilizers that may be used are described below in connection with FIG. 3.

[0065] Continuing with Figure 1, the boiler 4 may be provided with any suitable means for converting water to steam. For example, the boiler 4 may be provided with one or more heating elements 8 therein. Additionally, the boiler 4 may be provided with one or more water level switches 10 for interrupting the filling of the boiler 4 with water.

[0066] Water may be supplied from the vessel 2 to the boiler 4 by operating a pump 12 to pump water from the vessel 2. The vessel 2 may have an inlet 14 for supplying fresh water to the vessel 2 and an outlet 16 for allowing fresh water to flow out of the vessel 2. The outlet 16 of the vessel 2 opens into an outlet 18 (conduit), which may be a pipe, tube, hose, or similar structure. The pump 12 is suitably provided in said outlet 18. As previously explained in this disclosure, if the water supplied to the boiler 4 contains non-condensable gases (NCGs), these NCGs will be sent to the sterilization chamber of the steam sterilizer 6 together with the steam generated by the boiler 4. The presence of NCGs reduces the likelihood of achieving complete penetration of the steam into all parts of the article to be sterilized throughout the entire sterilization cycle. It is therefore desirable to remove most of the NCGs from the water before it is supplied to the boiler 4. To achieve this effect, the steam sterilization system 1 includes a degassing filter 20.

[0067] The outlet 18 extends from the outlet 16 of the vessel 2 to the degassing filter 20. The degassing filter 20 may be of the standard type used for vacuum or sweep gas degassing in various technical fields where water treatment takes place. The degassing filter 20 may have a shell side, through which the water passes along a hydrophobic membrane, and a lumen side (dry side) opposite the membrane. The lumen side may be connected to a vacuum tank 22, which is kept at low pressure. The degassing filter 20 works by striving for equilibrium of gases on both sides of the membrane, so that gases dissolved in the water are transferred through the membrane to the vacuum side, where they are removed by connection to the vacuum tank 22. However, water does not pass through the membrane of the degassing filter 20.

[0068] The vacuum, which may be generated by a vacuum pump that may be part of a dedicated vacuum system or a shared vacuum system (e.g., shared with steam sterilizer 6), may be maintained using vacuum tank 22. Alternatively, the vacuum may be provided by a vacuum pump or system without vacuum tank 22.

[0069] The water leaving the degassing filter 20 may continue to flow downstream of the degassing filter 20 along a supply line 24 for supplying water to the boiler 4. A first valve 26 may be provided in the supply line 24 to control the flow of water through the supply line 24. Specifically, when the pump 4 is pumping water from the container, the first valve 26 may be controlled to a closed state to prevent water from flowing from the degassing filter 20 to the boiler 4.

[0070] A recirculation line 28 extends from a point 30 in the supply line 24 upstream of the first valve 26 and downstream of the degassing filter 20. The recirculation line 28 is used to recirculate the water that has passed through the degassing filter 20 back to the vessel 2, so that at least a portion of the circulating water may be permitted to be fed to the boiler 4 after the same water has been passed through the degassing filter 20 multiple times. The vessel 2, the outlet line 18, and the recirculation line 28 may thus be considered to form part of a circulation loop.

[0071] The steam sterilization system 1 also includes a control unit 40, which is configured to communicate with the various components of the steam sterilization system 1 and to control the operation of certain components and receive input signals from the various components. The control unit 40 may be configured to communicate, send / receive instructions, etc., wirelessly or by wire. Thus, the control unit 40 is configured to perform the steps of the methods disclosed herein. The control unit 40 may be present in the same physical housing as the steam sterilizer 6, but in principle could be present elsewhere. The control unit may include electronics, a processor, memory, electronic instructions, and other elements useful for controlling any of the systems and methods described in this disclosure.

[0072] Figure 2 generally discloses a method 100 in accordance with at least one exemplary embodiment of the inventive concept. Specifically, Figure 2 discloses a method 100 for controlling a steam sterilization system that includes a boiler that converts liquid water to steam. The steam sterilization system may be, for example, the steam sterilization system 1 shown in Figure 1, or it may be different.

[0073] Method 100 is - in a first step S1, pumping water from the vessel and passing it through a degassing filter arranged upstream of the boiler in order to remove non-condensable gases (NCG) dissolved in the water; - in step S2, after passing the water through the deaeration filter, recirculating the water through the deaeration filter to further remove NCG while preventing the water from passing from the deaeration filter to the boiler; - in step S3, sending at least a portion of the water to a boiler after having recirculated the water through a degassing filter; Includes.

[0074] When the method 100 is implemented in the steam sterilization system 1 of FIG. 1 , the control unit 40 may be suitably configured to control the pump 12 such that water is pumped from the container 2 through the outlet 16, along the outlet path 18, and through the degassing filter 20, whereby dissolved NCGs in the water are removed. This reduces the NCG content of the water. The control unit 40 may also control the first valve 26 to be actuated or maintained in a closed state, thereby blocking the supply path 24, thereby preventing water from flowing from the degassing filter 20 to the boiler 4. Instead, the water is directed to the recirculation path 28 back to the container 2, in order to recirculate the water through the degassing filter 20 to further remove NCGs. Once sufficient degassing is achieved, the control unit 40 may then control the first valve 26 to be actuated to an open state, such that at least a portion of the water in the circulation loop may be delivered to the boiler 4.

[0075] 1, in at least some exemplary embodiments, a second valve may be provided in the recirculation line 28 to prevent recirculation, for example, when the water is being fed to the boiler 4. However, in other exemplary embodiments, the recirculation line 28 may be always open, thus allowing some amount of water to be recirculated even when the water is being sent to the boiler 4. In such cases, a flow reduction orifice may be appropriately provided in the recirculation line 28 so that the flow to the boiler 4 is greater than the flow back to the vessel 2.

[0076] When performing the method steps disclosed herein, the control unit 40 may suitably perform the step (S2) of recirculating water through the degassing filter 20 in such a manner that the total amount of water passing through the degassing filter 20 before at least that portion of the water is sent to the boiler 4 is at least twice the amount of water that was initially present in the vessel 2 or in the circulation loop before water began to be pumped from the vessel 2.

[0077] Specifically, the control unit 40 may continue to control the recirculation of the water through the degassing filter 20 by keeping the first valve 26 closed and continuing to operate the pump 12 so that the water circulates in the circulation loop until a satisfactory degassing is achieved. The control unit 40 may continue the recirculation, for example, until it determines that the water has circulated through the circulation loop and thus through the degassing filter 20 for at least a minimum period T1. Such a minimum period T1 may be available, for example, from a look-up table, or may be calculated by the control unit 40, for example, based on the amount of water available in the circulation loop. A larger amount of water may require a longer period T1 for the water to have a desired low or zero NCG content than a smaller amount of water. Instead of or as a complement to such a time-based recirculation control, the control unit 40 may instead perform a water volume-based recirculation control. In the latter case, the control unit 40 controls the circulation of the water (activating the pump 12 and closing the first valve 26) until at least a minimum number of cycles have been completed through the degassing filter 20, i.e. until the amount of water present in the circulation loop has necessarily passed through the degassing filter 20 a minimum number of times. For this purpose, a flow meter may be suitably provided in the circulation loop.

[0078] In another exemplary embodiment, the control unit 40 may alternatively or supplementarily perform pressure-based recirculation control. As shown in FIG. 1, a pressure sensor 42 may be provided to monitor, for example, the pressure in the vacuum tank 22. As previously described in this disclosure, the control unit 40 may determine when the recirculated water has been sufficiently degassed by monitoring the rate of pressure change. FIG. 1 also shows that, in at least some exemplary embodiments, the steam sterilization system 1 may be provided with a total dissolved gas (TDG) sensor 44, for example, located in the outlet path 18 between the pump 12 and the degassing filter 20. The control unit 40 may then control the duration of recirculation based on the NCG content measured by the TDG sensor 44.

[0079] In addition to controlling the duration of recirculation to be sufficient to provide adequate deaeration, the control unit 40 may also suitably receive input from the boiler's water level sensor or switch 10 to determine when the liquid level in the boiler 4 has dropped below a predetermined level and that a new batch of water may be charged to the boiler 4 for steam generation. Thus, the control unit 40 may monitor the liquid level in the boiler 4 and proceed from the step of recirculating the water through the deaeration filter 20 (S2) to the step of directing at least a portion of the water to the boiler 4 (S3) when the liquid level in the boiler 4 reaches or falls below said predetermined level.

[0080] The control unit 40 may also execute control actions based on predictions. For example, the control unit may predict that the water level in the boiler 4 will fall below a predetermined water level within a predetermined period T2 based on various input signals, including a signal indicative of the water level in the boiler 4. In such a case, the control unit 40 may, for example, close the inlet 14 of the vessel 2 or close a further valve 46 at the inlet 14 of the vessel 2 to prevent fresh water (high NCG content) from being supplied to the vessel 2 until the predetermined water level in the boiler 4 is reached and degassed water from the vessel 2 is sent to the boiler 4 to refill the boiler 4. Once the boiler 4 is refilled, the control unit 40 may again enable fresh water to be supplied to the vessel 2. As previously described in this disclosure, in another exemplary embodiment, fresh water may be supplied to the vessel 2 in other ways, for example to a location along the circulation loop upstream or downstream of the vessel 2. In such a case, the inflow of fresh water to the circulation loop may be closed as well to prevent fresh water from being supplied to the vessel 2.

[0081] As will be appreciated from the above, the control unit 40 may be configured to prevent fresh water from being supplied to the vessel 2 (e.g. by closing the further valve 46) while the water is recirculated through the degassing filter 20, and then send at least a portion of the water to the boiler 4 and then supply fresh water to the vessel 2.

[0082] In addition to receiving inputs regarding the water level in the boiler 4, the control unit 40 may also receive inputs regarding the water level in the vessel 2 (e.g., from one or more water level sensors or water level switches 48) and may determine whether it is suitable to supply fresh water to the vessel 2. In other words, the control unit 40 may monitor the water level in the vessel 2 and control the supply of fresh water to the vessel 2 based on the current water level in the vessel 2. Typically, if the current water level in the vessel 2 falls below a predetermined water level, the control unit 40 may decide to supply fresh water to the vessel 2. Of course, the control unit 40 may also take into account other considerations before deciding to supply fresh water to the vessel 2, such as whether the boiler 4 is currently being supplied with water or is expected to be supplied to the boiler within a certain (short) period of time, in which case the risk of fresh water with a high NCG content mixing with deaerated water already present in the circulation loop should be appropriately avoided.

[0083] If the control unit 40 predicts that refilling of the boiler 4 is not required immediately, fresh water may be appropriately supplied to the vessel 2. Conversely, if the control unit 40 determines that water needs to be supplied to the boiler 4 within a certain (short) period of time, the control unit 40 may prevent fresh water from being supplied to the vessel 2.

[0084] It should be understood that after the vessel 2 is supplied with fresh water, the water therein needs to be circulated and degassed. Thus, the control unit 40 is configured to repeatedly pump and recirculate water through the degassing filter 20 (i.e., in the embodiment shown in FIG. 1, operate the pump 12 while keeping the first valve 26 closed) while preventing water from flowing from the degassing filter 20 to the boiler 4.

[0085] After filling the boiler 4 with water, if the control unit 40 appropriately determines that there is still enough water remaining in the vessel 2 (or in the circulation loop) for the next batch for which water is again required for the boiler 4, the control unit 40 may appropriately postpone the supply of fresh water to the vessel 2. For example, the control unit 40 may be configured to monitor the water level in the vessel 2 and prevent fresh water from being supplied to the vessel 2 as long as the water level in the vessel 2 is at or above a predetermined water level (indicating that there is at least a sufficient amount of water remaining in the vessel for another batch of water to be delivered to the boiler 4). After operating the boiler 4 to generate steam (and as long as the water level in the vessel 2 is at or above the predetermined water level), the control unit 40 may control a further portion or portions of water to be sent to the boiler 4 and operate the boiler 4 to convert the further portion or portions of water into steam.

[0086] It should be understood that degassing typically takes longer than filling the vessel 2 with fresh water. Thus, the control unit 40 may be programmed to optimize filling and / or degassing based on current needs and requirements, for example, from the boiler 4. For example, the control unit 40 may decide to only half-fill the vessel 2. Degassing half the amount of water is expected to take approximately half the time compared to degassing the full amount of water separately. This may be a strategy if the control unit 40 determines that the boiler 4 needs to be refilled soon.

[0087] Thus, from the above, it should be appreciated that the general practice of recirculating water through a degassing filter 20 (i.e., passing the water through the degassing filter on average two or more times) before allowing at least a portion of the water to be delivered to a boiler (e.g., boiler 4 in FIG. 1) reduces the amount of NCG in the steam supplied to a steam sterilizer (e.g., sterilizer 1 in FIG. 1), thereby improving sterilization of articles such as medical devices. In addition to this concept of recirculating water through a degassing filter, other control actions may be included to further reduce the risk of undesired NCG inclusions carrying the steam to the steam sterilizer. For example, before filling the boiler with water or at start-up, a vacuum may be drawn in the boiler to remove air in the boiler and prevent air residues carrying the steam to the steam sterilizer. Such a vacuum is indicated diagrammatically by the arrow above boiler 4 in FIG. 1.

[0088] Figure 3 is a schematic diagram of a steam sterilizer 60 that can be used with the disclosed system 1 of Figure 1. Thus, the steam sterilizer 60 of Figure 3 may suitably replace the steam sterilizer 6 generally shown in Figure 1. However, other steam sterilizers are contemplated.

[0089] The steam sterilizer 60 comprises a sterilization chamber 62. Steam from the boiler 4 is directed into the sterilization chamber 62 through an inlet 64. A drain system 66 is provided to control the drainage of fluids from the sterilization chamber 62 via an outlet 68. A vacuum system 70 (which may be a separate vacuum system or may be shared with the degassing structure of FIG. 1 ) is connected to the drain system 66 to drain steam from the sterilization chamber 62 and condense the drained steam using a flow of coolant 72. The control unit 40 may be configured to control the flow of steam from the boiler 4 to the sterilization chamber 62 via a controllable valve 74. The control unit 40 may use information received from a temperature sensor 76 in the flow of coolant 72 to determine the amount of steam / condensate flowing from the sterilization chamber 62 to the drain system 66. The control unit 40 may receive other input signals besides temperature signals. For example, the control unit 40 may monitor the pressure in the sterilization chamber 62 by a pressure sensor 78 configured to detect the pressure in the sterilization chamber 62.

[0090] The present disclosure includes a steam sterilization system, specifically for sterilizing articles for medical use. The present disclosure also includes a controller (comprising electronics and instructions) for controlling the components of the steam sterilization system as described herein. The present disclosure further includes a method for operating and controlling the steam sterilization system, a method for efficiently degassing water prior to providing the water to a boiler for steam production, and a method for sterilizing medical instruments. It is to be understood that the various features and methods disclosed herein are contemplated and disclosed in various combinations and subcombinations thereof.

Claims

1. 1. A method of controlling a steam sterilization system having a boiler that converts liquid water to steam, the method comprising: pumping water from a vessel and passing the water through a degassing filter located upstream of the boiler to remove non-condensable gases (NCGs) dissolved in the water; recirculating the water through the degassing filter after the water has passed through the degassing filter to further remove NCG while preventing water from passing from the degassing filter to the boiler; sending at least a portion of the water to the boiler after recirculating the water through the degassing filter; monitoring a liquid level in the boiler; proceeding from the step of recirculating the water through the degassing filter to the step of directing at least a portion of the water to the boiler when the liquid water level in the boiler reaches or falls below a predetermined level; preventing fresh water from being supplied to said vessel when said predetermined water level in said boiler is reached until degassed water from said vessel is sent to said boiler to recharge said boiler; A method comprising:

2. 2. The method of claim 1, wherein the step of recirculating the water through the degassing filter includes recirculating the water through the degassing filter such that a total amount of water passing through the degassing filter before the at least a portion of the water is sent to the boiler is at least twice the amount of water that was originally in the vessel prior to the step of pumping water from the vessel.

3. 2. The method of claim 1, wherein the step of recirculating the water through the degassing filter continues until determining either: (i) the water has been circulated through the degassing filter for at least a predetermined period of time T1; or (ii) the water has completed at least a predetermined number of cycles through the degassing filter.

4. The method comprises: determining a determined time period T2, the determined time period T2 being a time period during which the water level in the boiler will reach or fall below the predetermined water level; supplying fresh water to said container after said step of preventing fresh water from being supplied; The method of claim 1 , comprising:

5. The method comprises: preventing fresh water from being supplied to said container while water is recirculated through said degassing filter; and thereafter directing at least a portion of said water to said boiler; and thereafter providing fresh water to said vessel; The method of claim 1 further comprising:

6. The method comprises: monitoring the water level in the vessel; controlling the supply of fresh water to the vessel based on a current water level in the vessel; The method of claim 1 , comprising:

7. 7. The method of claim 6, wherein controlling the supply of fresh water to the vessel based on the current water level in the vessel includes supplying fresh water to the vessel when the water level falls below a predetermined level.

8. The method comprises: providing fresh water to the vessel in response to determining that deaerated water has not been provided to the boiler for at least a first predetermined period of time T3; preventing fresh water from being provided to said vessel in response to determining that water needs to be provided to said boiler within a second predetermined time period T4; The method of claim 1 , further comprising at least one of:

9. The method comprises: preventing water from being delivered to the boiler after the step of delivering at least a portion of the water to the boiler; providing fresh water to said vessel; and thereafter repeating the steps of pumping and recirculating water through the degassing filter while preventing water from flowing from the degassing filter to the boiler; The method of claim 1 , comprising:

10. The method according to claim 1, generating steam by operating the boiler after the step of passing at least a portion of the water to the boiler; monitoring the water level in the vessel; preventing fresh water from being provided to said container so long as the water level in said container is equal to or greater than a predetermined water level; after the step of generating steam by operating the boiler, sending a further portion of the water to the boiler and generating steam by operating the boiler as long as the water level in the vessel is equal to or greater than the predetermined water level; The method of claim 1 , comprising:

11. The method of claim 1, comprising extracting NCG from water passing through the degassing filter by applying a vacuum to the degassing filter via a vacuum tank.

12. 2. The method of claim 1, wherein the step of recirculating the water through the degassing filter is continued until determining that a rate of pressure change within a closable volume in gaseous communication with the degassing filter falls below a predetermined threshold.

13. A control unit configured to carry out the steps of the method according to any one of claims 1 to 12, said control unit comprising: controlling the pumping of water from the container by controlling a pump of the steam sterilization system; selectively blocking or enabling water from being passed from the degassing filter to the boiler by controlling a first valve of the steam sterilization system; Optionally, selectively blocking or enabling the supply of fresh water to the container by controlling a further valve of the steam sterilization system. The control unit is configured to:

14. A steam sterilization system comprising a control unit as described in claim 13, the steam sterilization system further comprising a boiler and a sterilization chamber.

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