Patent Description:
Pressurized liquid circulating systems are normally designed to operate at a specific operating pressure. Replenishing may be required on a regular basis in order to maintain the operating pressure within a predetermined range, and compensate for any pressure losses that may occur over time. For replenishing the pressurized liquid circulating system, it may be temporarily connected to a pressurized liquid supply. Liquid may then flow from the pressurized liquid supply into the pressurized liquid circulating system to raise a pressure of the liquid contained therein.

Although a pressurized liquid circulating system is not limited to systems using water as a liquid, the present invention is especially suitable for - and described in relation to - heating and cooling systems using water as a heat-transfer medium, also called hydronic systems. The water of a hydronic system may be liquid water, gaseous water (steam) or a water solution (usually glycol with water).

Also, most hydronic systems are designed to operate at a specific operating pressure, which especially applies to hydronic systems that use liquid water or a water solution as a heat transfer medium. Consequently, replenishing may be required on a regular basis in order to maintain the desired operating pressure, and compensate for any pressure losses that may occur over time, e.g. due to small leaks or evaporation.

A disadvantage of many prior art replenishing systems is the undesirable introduction of gas into the pressurized liquid circulating system when replenishing the system with liquid. This introduction of gas may be caused by a column of gas being pushed into the pressurized liquid circulating system, or alternatively by the introduction of gas-rich fluid, typically gas-rich water, especially if a turbulent flow prevents degassing prior to the introduction into the system.

Introduction of a column of gas may be clarified based on the steps performed when replenishing a central heating system. During such a replenishing, a hose is temporarily arranged between the water mains system, that defines the pressurized liquid supply, and the central heating system, that defines the pressurized liquid circulating system. At first, this hose is empty, and consequently it will contain ambient air. Once closed off from the environment, a valve of the water mains system may be opened, now partially filling the hose with water due to the water pressure in the water mains system, and also compressing the air trapped inside said hose. After opening a further valve between the hose and the central heating system, the pressure in the water mains system will force water to flow from the water mains system into the central heating system. The air that was trapped in the hose when it was connected between the water mains system and the central heating system is now also forced into the central heating system along with the replenishing water.

Although it may be undesirable to introduce a column of air into the central heating system, said same column of air also fulfills a very important - and potentially legally required - function. After all, since a hydronic system is a closed system, any system water contained therein will be unsafe for human consumption. Serious health risks may arise when water from the central heating system would come into contact with the potable water in the water mains system. For this reason, European regulation requires a free distance, also known as air gap, to be present between the liquid in the pressurized liquid supply and the liquid in the pressurized liquid circulating system.

<CIT>, which is directed to a filling means for a pressurized fluid system such as a central heating system, is considered the closest prior art. An intermediate section may be interpreted as a collector that is arranged between the input and the replenishing output. An air vent permits the expulsion of air from the intermediate section whilst preventing the passage of fluid. Consequently, this air vent that is arranged on an upper side of said intermediate section may be considered a gas extractor of the collector.

<CIT>, <CIT>, <CIT>, <CIT> and the international patent application <CIT>, are acknowledged as further prior art.

An objective of the present invention is to provide a replenishing system and replenishment method, that is improved relative to the prior art and wherein at least one of the above stated problems is obviated or alleviated.

Said objective is achieved with the replenishing system according to the present invention, comprising:.

Using the gas extractor, gas present in the liquid contained in the replenishing system, in particular in the collector thereof, may be extracted out of the liquid before said liquid is successively introduced into the pressurized liquid circulating system. The replenishing system according to the invention thereby allows a replenishing of a pressurized liquid circulating system with a significantly reduced introduction of gas. Especially gas present to provide an initial air gap, may be effectively extracted. It is however remarked that the liquid itself may also contain gas, e.g. in the case of water, and consequently liquid flowing from the pressurized liquid supply into the pressurized liquid circulating system may still introduce some gas into the pressurized liquid circulating system.

Preferred embodiments are the subject of the dependent claims. According to a first preferred embodiment, the collector is an upward extending conduit or vessel, and the gas extractor comprises a gas accumulator that is arranged at an upper end of the collector. It is remarked that upward extending may be slanted and comprising at least an upward component, whereas - even more preferably - the upward extending conduit is an upright extending conduit or vessel, wherein upright is interpreted as substantially vertical. An upward, or even more preferably an upright, extending collector facilitates the natural of process of gas rising inside the liquid, and thereby promotes the extraction of gas out of said liquid. In this way the gas accumulator of the gas extractor that is arranged at the upper end of the collector may extract the gas that will have a tendency to rise in the liquid. By arranging the the gas accumulator at an upper end of the collector, gas present in the liquid may accumulate in the gas accumulator above a liquid level inside the collector. A gas accumulator may provide an air gap in a very fast and reliable manner. After all, the gas that is accumulated in the gas accumulator may easily flow downward and back into the collector when liquid flows out of said collector (e.g. towards a drain) and thereby creates an underpressure in said collector. The gas in the accumulator will normally even have an overpressure that forces the draining of liquid via a drainage output, speeding up the draining and the creation of the air gap. It is especially mentioned here that such a gas accumulator is faster and more reliable than only relying on an aerator, that will only open if the underpressure has passed a certain threshold level, and than still often only allows a limited flow rate, causing the air gap to build relatively slowly, and considerable slower than the speed of air gap creation obtainable with a gas accumulator. Moreover, a gas accumulator is very reliable, since it requires no moving parts, contrary to an aerator. Also, contrary to the filling means for a pressurized fluid system disclosed in <CIT>, the gas accumulator prevents any air in the air gap to become trapped and flushed into the pressurized fluid system.

According to an even further preferred embodiment, the replenishing system may further comprise a drainage output that is configured to be arranged in liquid connection with a drain and a drain valve configured to selectively open or close off said drainage output. By draining the replenishing system, in particular the collector thereof, gas present therein may be forced out of the replenishing system. Although effective, using liquid provided by the pressurized liquid supply to force gas out of the replenishing system by draining thereof, inevitably requires liquid to be wasted during the replenishing action.

In order to facilitate draining of the collector, the gas extractor may comprise, according to an even further preferred embodiment, an aerator configured to allow ambient air to enter the collector and thereby prevent an underpressure to occur during draining of the collector.

According to an even further preferred embodiment, the replenishing system further comprises a safety conduit that is extending in a sloping direction away from the collector. This safety conduit is arranged between the collector and the replenishing output. A sloping direction of said safety conduit is guarantees that a liquid connection between the liquid in the pressurized liquid circulating system and the liquid in the pressurized liquid supply, e.g. a mains water supply, is physically broken. In this way a liquid connection is prevented, even in the unlikely situation of a failure of a valve.

According to an even further preferred embodiment, the safety conduit is extending in a downward sloping direction away from the collector. In this way, any gas present in liquid in the safety conduit will be able to rise inside said safety conduit towards the collector and flow back into the collector. When the collector is drained and the liquid level in the collector drops to a level below a connection of the safety conduit to the collector, any liquid that may be still present in the collector will be physically disconnected from any water in the safety conduit.

According to an even further preferred embodiment, the safety conduit is extending in an upward sloping direction away from the collector. This arrangement will cause liquid to automatically drain from said safety conduit if a drain valve, which is normally open, is in an open state. It is even conceivable that the safety conduit is tapered to provide a downward slope away from the collector to effectively allow any gas present in the liquid in the safety conduit to rise and flow back into the collector, while also providing an upward slope away from the collector for draining any liquid from said safety conduit if a drain valve is opened. The safety conduit will be tapered in a direction away from the collector, and thus exhibit a larger cross section near the collector than at a remote end from the collector.

According to the invention, the replenishing system further comprises a water hammer arrestor, and optionally a shock absorber, e.g. for noise reduction that comprises:.

The pressurized liquid supply may be a water mains system, and the pressurized liquid circulating system may be a hydronic system.

Although the replenishing system may be an assembly of different parts, a very user-friendly embodiment is obtained if features of the replenishing system as described in this application are comprised in a housing of a replenishment device, wherein the input is configured to be arranged in liquid connection with the pressurized liquid supply, and wherein the replenishing output is configured to be arranged in liquid connection with the pressurized liquid circulating system.

The objective is also achieved with the method of replenishing a liquid into a pressurized liquid circulating system using the replenishing device according to the present invention, comprising the steps of:.

According to a preferred embodiment of the method, the collector is an upward extending conduit or vessel, the step of extracting gas out of said liquid comprises the step of accumulating said extracted gas in a gas accumulator that is arranged at an upper end of the collector, and the step of draining liquid via the drainage output of the replenishing system comprises the step of forcing the draining of said liquid by an overpressure of the gas in the gas accumulator. In this way, the gas accumulator contributes to provide an air gap in a very fast and reliable manner.

According to a further preferred embodiment of the method, the step of extracting gas out of said liquid comprises the step of allowing gas to rise in a safety conduit that is extending in a downward sloping direction away from the collector and allowing said gas to flow from the safety conduit back into the collector. In this way, it is effectively prevented that gas, in particular air, becomes trapped in the safety conduit, and may be pushed into the pressurized liquid circulating system during replenishing thereof.

According to an even further preferred embodiment of the method, the step of extracting gas out of said liquid comprises extracting substantially all gas originating from an initial air gap between the liquid of the pressurized liquid supply and the liquid of the pressurized liquid circulating system out of said liquid to provide a liquid connection between the liquid of the pressurized liquid supply and the liquid of the pressurized liquid circulating system. The initial air gap is an air gap present between the liquid of the pressurized liquid circulating system and the liquid of the pressurized liquid supply prior to the replenishing action, as also required by (European) regulations. The invention proposes to extract the gas present in said initial air gap to thereby significantly reduce the amount of gas introduced into the pressurized liquid circulating system during a replenishing thereof.

The replenishing system according to the invention may be installed one time, after which it may be maintained in a connected state. However, at least for the first time use, the method of replenishing may be preceded by the steps of:.

According to an even further preferred embodiment of the method, it further comprises the step of stopping liquid to flow from the pressurized liquid supply through the replenishing system and into the pressurized liquid circulating system after a pre-determined operating pressure in the pressurized liquid circulating system is set. Replenishing is stopped when the desired operating pressure is reached, and may be repeated over time if the pressure drops to below a pre-determined threshold.

As already mentioned above, the liquid itself may also contain gas, e.g. in the case of water, and consequently liquid flowing from the pressurized liquid supply into the pressurized liquid circulating system may still introduce some gas into the pressurized liquid circulating system. In order to extract also gasses out of gas-rich water, it is proposed to replenish the pressurized liquid circulating system step-by-step, in each step allowing gas to be extracted out of the liquid. The method therefore may comprise, according to an even further preferred embodiment, replenishing of the pressurized liquid circulating system in at least two stages by alternating the steps of:.

According to an even further preferred embodiment of the method, it further comprises the step of draining liquid via a drainage output of the replenishing system, thereby at least partially emptying the upward extending conduit of the collector.

According to an even further preferred embodiment of the method, it further comprises the step of lowering a liquid level in said upward extending conduit till below a connection to a safety conduit that is extending away from the upward extending conduit in a sloping direction. If the liquid level in the collector drops to a level below the connection of the safety conduit to the collector, any liquid that may be still present in the collector will be physically disconnected from any water in the safety conduit. In this way, safety is guaranteed, even in the unlikely situation of a valve failure. Prefereably the safety conduit is extending in a downward sloping direction away from the collector and allowing said gas to flow from the safety conduit back into the collector.

According to an even further preferred embodiment of the method, it further comprises the step of aerating the replenishing system to promote draining of liquid out of the collector.

According to an even further preferred embodiment of the method, the step of extracting gas out of said liquid comprises the step of accumulating said extracted gas in a gas accumulator, and the step of draining liquid via a drainage output of the replenishing system comprises the step of forcing the draining of said liquid by an overpressure of the gas in the gas accumulator. If the collector is an upward or upright extending conduit or vessel, it will already drain due to gravity. As described above, an aerator may allow air into the system to prevent any underpressure (or vacuum) to prevent this draining. However, an even more preferred embodiment is obtained if the extracted gas is accumulated in the collector, in particular in the gas accumulator, under pressure. This pressure may promote draining by forcing the liquid out of the collector once a drainage valve is opened.

According to an even further preferred embodiment of the method, it comprises the step of using a replenishing system according to the present invention.

The replenishing system may further comprises a controller, and the invention may further relate to a non-transitory computer-readable medium comprising computer readable instructions that, when executed, cause a controller to perform the method of the method according to the invention.

These individual aspects, and in particular the aspects and features described in the attached dependent claims, such as the water hammer arrestor having a housing and a spring, may be an invention in its own right that is related to a different problem relative to the prior art. This also applies to the safety conduit that is exgtending in a downward sloping direction away from the collector to thereby allow gas in the safety conduit to rise and flow back into the collector, preventing gas to become trapped in the replenishing system.

In the following description preferred embodiments of the present invention are further elucidated with reference to the drawing, in which:.

The Figures show three main concepts of replenishing systems according to the invention. The main principle is however the same for all concepts and consequently similar reference numbers apply to the similar features of the different embodiments.

All embodiments show a replenishing system <NUM> that comprises an input <NUM> that is configured to be arranged in liquid connection with a pressurized liquid supply <NUM>, and a replenishing output <NUM> that is configured to be arranged in liquid connection with a pressurized liquid circulating system <NUM>. The replenishing system <NUM> further comprises a collector <NUM> that is arranged between the input <NUM> and the replenishing output <NUM>, wherein the collector <NUM> comprises a gas extractor <NUM>. The collector <NUM> is preferably an upward extending, and more preferably an upright extending, conduit or vessel, as shown in the Figures.

Although not limited thereto, the pressurized liquid supply <NUM> may be a water mains system, and the pressurized liquid circulating system <NUM> may be a hydronic system.

The gas extractor <NUM> may be arranged at an upper end <NUM> of the collector <NUM>, in this way making optimal use of the natural tendency of a gas to rise in a liquid. The replenishing system <NUM> may comprises an aerator <NUM> configured to allow ambient air to enter the collector <NUM> and thereby prevent an underpressure to occur during draining of the collector <NUM>. Such an aerator <NUM> is shown in the first and the second preferred embodiments, shown in <FIG>, <FIG> and in <FIG>, <FIG>, respectively. Alternatively, or additionally, the gas extractor <NUM> may comprise a gas accumulator <NUM>, as shown in the second and third preferred embodiments, shown in <FIG>, <FIG> and in <FIG>, <FIG>, respectively.

The replenishing system <NUM> may further comprise a drainage output <NUM> that is configured to be arranged in liquid connection with a drain <NUM>. A drain valve <NUM>, which is normally open, may be temporarily closed during a replenishing action, as will be further discussed below.

In the shown embodiments, a safety conduit <NUM> is extending in a sloping direction away from the collector <NUM>. In the first three embodiments shown in <FIG>, the safety conduit <NUM> is extending in a downward sloping direction away from the collector <NUM>. A downward sloping arrangement of the safety conduit <NUM> allows gas to rise in a liquid, and thus flow upward and upstream in the safety conduit <NUM> and via the safety conduit <NUM> back into the collector <NUM>. Thus, in a hydronic system, air may rise in water that is present in the safety conduit <NUM> an flow back into the collector <NUM>, resulting in the safety conduit <NUM> being free from air. <FIG> however proposes an alternative arrangement, wherein the safety conduit <NUM> is extending in an upward sloping direction away from the collector <NUM>. An additional advantage of the upward sloping safety conduit of <FIG> is that it will automatically drain liquid after a replenishing action, when the drain valve is opened <NUM>, and preferably is left open. During filling of the safety conduit <NUM> of <FIG>, a small amount of gas may be trapped inside the safety conduit <NUM>. This may be prevented if the safety conduit <NUM> is tapered, on the one hand providing a slope along which liquid may flow out of the safety conduit <NUM>, while on the other hand allowing any gas in safety conduit <NUM> to be directed along the upper wall upstream towards the collector <NUM>.

All embodiments shown in the Figures show an optional water hammer arrestor <NUM> of an improved type, that comprises:.

Although the preferred embodiment shown in <FIG> comprise two non-return valves <NUM>, only one non-return valve <NUM> may be enough under normal circumstances. If only one non-return valve <NUM> is applied, a body of said single non-return valve <NUM> defines the housing <NUM> and the non-return valve <NUM> may be directly arranged inside a conduit of the replenishing system <NUM> with the spring <NUM> restricting the movement of the body of the non-return valve <NUM> relative to said conduit.

Restrictors <NUM> may be arranged to guarantee sufficient pressure between shutoff valve <NUM>, the drain valve <NUM> and the further backflow preventer <NUM>. In this way, a reliable operation of drain valve <NUM> is guaranteed, even if a pressure in the pressurized liquid circulating system <NUM> would be very low, e.g. when filling the pressurized liquid circulating system <NUM> for the first time with liquid from the pressurized liquid supply <NUM>.

In order to allow a controller <NUM> to automatically replenish the pressurized liquid circulating system <NUM>, and allow the controller <NUM> to perform checks, a further pressure sensor <NUM> may be arranged near the replenishing output <NUM>.

In a preferred embodiment, a liquid sensor <NUM> that is configured to detect a flow or a presence of liquid is arranged downstream of drain valve <NUM>, preferably near drainage output <NUM>. This liquid sensor <NUM> allows safety checks to be performed by the controller <NUM>. After all, if the shutoff valve <NUM> would malfunction and start to leak, liquid will flow from the pressurized liquid supply <NUM> via collector <NUM> and the drain valve <NUM>, which is normally open, towards the drain <NUM>. Likewise, if the further backflow preventer <NUM> would start to leak, liquid will flow from the pressurized liquid circulating system <NUM> via the safety conduit <NUM> and the drain valve <NUM>, which is normally open, towards the drain <NUM>. In this way, a single liquid sensor <NUM> arranged downstream of the drain valve <NUM> may be used to detect a leakage in one or both of the shutoff valve <NUM> and the further backflow preventer <NUM>, and thereby further increase the safety of the replenishing system <NUM>.

The replenishing system <NUM> may be arranged in a housing <NUM>, providing an easy-to-use and an easy-to-install replenishing device <NUM>.

The configurations of the main three embodiments are shown in <FIG>, <FIG> and <FIG>, that all comprise all relevant reference numbers. The operation of the three embodiments is now described in more detail, wherein <FIG> defines the starting state for the successive steps of a replenishing action that are shown in <FIG>. Likewise, <FIG> and <FIG> define the starting state for the successive steps of a replenishing action that are shown in <FIG>, and <FIG>, respectively, that only comprise the relevant references for explaining the operation.

The starting states of <FIG>, <FIG> and <FIG> is identical, although the configuration of the replenishing system <NUM> differs. In all embodiments, the starting state comprises a (normally) closed shutoff valve <NUM> that shuts off the liquid inside the pressurized liquid supply <NUM>. The drain valve <NUM> is (normally) open, and the liquid inside the pressurized liquid circulating system <NUM> is below the replenishing output <NUM>, more in particular downstream the further backflow preventer <NUM>.

The next step for the first embodiment is shown in <FIG>, and comprises opening of the shutoff valve <NUM> to allow liquid to flow through the collector <NUM> of the replenishing system <NUM>. Drain valve <NUM> is still open and therefore liquid flows through collector <NUM> towards drain <NUM>, also pushing any gas present in the initial air gap between the liquid in the pressurized liquid circulating system <NUM> and the pressurized liquid supply <NUM> out of the replenishing system <NUM>. The extraction of gas in the step shown in <FIG> is however at the expense of some loss of liquid that is flushed directly towards the drain <NUM>.

Once the gas has been removed from the replenishing system <NUM>, the drain valve <NUM> is closed, and pressure will build up inside the replenishing system <NUM>. Once the pressure inside the replenishing system <NUM> is higher than the pressure of the pressurized liquid circulating system <NUM>, the liquid will flow through the further backflow preventer <NUM>, via the replenishing output <NUM> into the pressurized liquid circulating system <NUM> (<FIG>).

In the next step that is shown in <FIG>, the shutoff valve <NUM> is closed and the drain valve <NUM> is opened. Ambient air can enter the replenishing system <NUM> via the aerator <NUM> that is arranged at the upper end <NUM> of the collector <NUM>, thereby preventing an underpressure to occur and thus facilitate draining of the collector <NUM>. <FIG> shows that the liquid level inside collector <NUM> drops to a level at least below the connection of the safety conduit <NUM> to the collector <NUM>. By lowering of the liquid level in the collector <NUM> till below this branching off of the safety conduit <NUM>, it is guaranteed that any liquid left in the collector <NUM> is physically disconnected from the liquid inside the safety conduit <NUM>.

Once the collector <NUM> is fully drained, the end state shown in <FIG> is obtained. Please note that the end state shown in <FIG> discloses some liquid inside the safety conduit <NUM>. Because the drain valve <NUM> is normally open, this liquid may evaporate over time and consequently the starting state of <FIG> differs from the end state of <FIG>, in that liquid is absent in the safety conduit <NUM>.

The second embodiment is very closely related to the first embodiment, but comprises an additional gas accumulator <NUM> wherein gas may accumulate in the step shown in <FIG>. The operation of the second embodiment is now explained in more detail, with special attention for the differences relative to the first embodiment.

In the step shown in <FIG>, the shutoff valve <NUM> is opened to allow liquid to flow out of the pressurized liquid supply <NUM> into the replenishing system <NUM>, and shortly thereafter shutoff valve <NUM> is closed again. However, contrary to the step shown in <FIG> of the first embodiment, the drain valve <NUM> is now closed. Consequently, no liquid is lost in the drain <NUM> anymore. By opening the shutoff valve <NUM> to fill the collector <NUM> with liquid, and immediately closing the shutoff valve <NUM> after collector <NUM> has been filled, the pressure inside the replenishing system <NUM>, more in particular in the collector <NUM>, is preferably kept lower than the pressure level of the liquid inside the pressurized liquid supply <NUM>. As long as the pressure inside collector <NUM> is lower than the pressure inside the pressurized liquid supply <NUM>, there will be no flow of liquid from the collector <NUM> via the further backflow preventer <NUM> and the replenishing output <NUM> into the pressurized liquid circulating system <NUM>. In this way, the gas present in the initial air gap between the liquid in the pressurized liquid circulating system <NUM> and the pressurized liquid supply <NUM> can be given sufficient time, e.g. in the order of a few minutes, to rise inside the collector <NUM> and consequently accumulate in the gas accumulator <NUM> that is arranged at the top end <NUM> of the collector <NUM>. In this way, the gas is effectively extracted out of the liquid before said liquid is allowed to flow into the pressurized liquid circulating system <NUM> for replenishing thereof. It is also conceivable that, instead of opening the shutoff valve <NUM> once and only closing it after the collector <NUM> has been completely filled with liquid, the collector <NUM> may be filled by opening and closing the shutoff valve <NUM> in a pulsating manner to obtain a step-by-step filling of the collector <NUM> that may facilitate formation and rising of microbubbles.

Once the gas is accumulated in the gas accumulator <NUM>, the shutoff valve <NUM> will be opened again and pressure will build up in the replenishing system <NUM>. When the pressure inside the replenishing system <NUM> becomes higher than the pressure of the pressurized liquid circulating system <NUM>, the liquid will flow through the further backflow preventer <NUM>, via the replenishing output <NUM> into the pressurized liquid circulating system <NUM> (<FIG>).

In the next step that is shown in <FIG>, the shutoff valve <NUM> is closed and the drain valve <NUM> is opened. The pressure that has been build up by the gas that has accumulated in the gas accumulator <NUM> will exert a downward directed force that promotes draining of remaining liquid out of the collector <NUM> that also results from gravity. This pressure reduces the chance that any underpressure occurs. However, ambient air can also enter the replenishing system <NUM> via the aerator <NUM> that is arranged at the upper end <NUM> of the collector <NUM>, thereby additionally preventing an underpressure to occur and thus facilitate draining of the collector <NUM>. <FIG> shows that the liquid level inside collector <NUM> drops to a level at least below the connection of the safety conduit <NUM> to the collector <NUM> to guarantee that any liquid left in the collector <NUM> is physically disconnected from the liquid inside the safety conduit <NUM>. Once the collector <NUM> is fully drained, the end state shown in <FIG> is obtained.

The third preferred embodiment shown in <FIG> is closely related to the second embodiment, but an aerator <NUM> is now absent because the pressure builds up inside the gas accumulator <NUM> due to the extraction of gas out of the liquid may be enough to facilitate a draining of the collector <NUM>. If an aerator <NUM> is absent, the replenishing system <NUM> is further simplified and reliability is further improved.

Since no liquid is drained in the steps shown in <FIG> and <FIG>, both the second and the third embodiment may be used in a method of replenishing of the pressurized liquid circulating system <NUM> in at least two stages by alternating the steps of: allowing liquid to enter the replenishing system <NUM>, thereby filling the collector <NUM> that is arranged between the input and a replenishing output <NUM> of the replenishing system <NUM>; and extracting gas out of said liquid in said collector <NUM>, thereby effectively repeating the steps shown in <FIG> and <FIG> multiple times. In this way, in addition to the gas present in the initial air gap, also gas present in the liquid, such as gas present in gas-rich water, can be extracted out of the liquid before it is introduced into the pressurized liquid circulating system <NUM>.

Claim 1:
Replenishing system (<NUM>), comprising:
- an input (<NUM>) that is configured to be arranged in liquid connection with a pressurized liquid supply (<NUM>);
- a replenishing output (<NUM>) that is configured to be arranged in liquid connection with a pressurized liquid circulating system (<NUM>); and
- a collector (<NUM>) that is arranged between the input (<NUM>) and the replenishing output (<NUM>) and that comprises a gas extractor (<NUM>); and characterized in that
the system further comprising a water hammer arrestor (<NUM>) that comprises:
- a housing (<NUM>) supporting one or more than one non-return valve (<NUM>) configured to prevent a backflow from the pressurized liquid circulating system (<NUM>) through the water hammer arrestor (<NUM>) towards the pressurized liquid supply (<NUM>);
- wherein said housing (<NUM>) is configured to move upstream over a limited range when the one or more than one non-return valve (<NUM>) is exposed to the backflow; and
- wherein a spring (<NUM>) is configured to restrict and absorb the movement of the housing (<NUM>).