WO2008089525A1

WO2008089525A1 - Water separator for a water-injected screw compressor and a compressor installation provided with such a water separator

Info

Publication number: WO2008089525A1
Application number: PCT/BE2008/000003
Authority: WO
Inventors: Ann Valerie Van Der Heggen; Jan Paul Herman Heremans
Original assignee: Atlas Copco Airpower, Naamloze Vennootschap
Priority date: 2007-01-26
Filing date: 2008-01-22
Publication date: 2008-07-31
Also published as: BE1017444A3

Abstract

Water separator (1) for a water-injected compressor, comprising a reservoir (2), which is provided with an inlet (5) for a mixture of compressed gas and water, with an outlet (6) for compressed gas and with an outlet opening (13) for separated water, characterised in that this reservoir (2) is predominantly L-shaped with an upwardly- directed leg (3) on which the above-mentioned inlet and the outlet for compressed gas are provided and a diagonally directed leg (4) in which the above-mentioned outlet opening (13) is provided.

Description

Water separator for a water-injected screw compressor and a compressor installation provided with such a water separator.

The present invention concerns a water separator for a water-injected compressor.

Water separators made in the shape of what is called a cyclone separator are already known, consisting of a barrel-shaped reservoir, which is provided with a tangentially placed inlet for a mixture of compressed gas and water, with an outlet for compressed gas and with an outlet opening for separated water.

Such water separators are applied for example in the compressed air line of water-injected screw compressors, whereby the water that has been injected in the compression chamber is recycled from the compressed air so as to be used again for injection in the compressor, in order to lubricate and cool the rotors in the compression chamber.

Moreover, problems related to the presence of water in the compressed gas are avoided with such a water separator, such as for example corrosion, water hammer in compressed air lines and the like.

A disadvantage of the known water separators is that they are very sizeable, as a result of which they occupy a lot of space in a production room, during transport and during their assembly, and as a result of which the water separator is often very expensive. An additional disadvantage of the known water separators is that, because of their often very large dimensions, they must always be approved, as prescribed for example in the ASME standards (American Society of Mechanical Engineers) .

Another disadvantage of the known water separators is that, when the compressor installation is started up, because of the relatively large amount of gas in this water separator, the water injection pressure in the water separator will be built up relatively slowly, as a result of which the rotors and the bearings of the compressor are not immediately provided with a required amount of water for cooling and lubrication, which has a negative effect on the life and efficiency of the compressor element.

The present invention aims to remedy one or several of the above-mentioned and other disadvantages.

To this end, the present invention concerns a water separator for a water-injected compressor comprising a reservoir, which is provided with an inlet for a mixture of compressed gas and water, with an outlet for compressed gas and with an outlet opening for separated water, whereby this reservoir is predominantly L-shaped with an upward directed leg, onto which the above-mentioned inlet and the outlet for compressed gas are provided, and a crosswise directed leg in which the above-mentioned outlet opening is provided.

Thanks to the L-shape of the reservoir, the water separator only occupies a very limited space in height, which is advantageous during the storage, transport and assembly, and as a result of which the water separator is relatively cheap.

Another advantage of such a water separator according to the invention is that, thanks to the restricted dimensions, it becomes possible to couple the water separator directly to, or to combine it with a compressed air source such as a compressor or the like, without any adapters or couplings being required.

Another advantage of a water separator according to the invention is that the water separator can be made with a restricted inside diameter and a restricted inside volume, such that it may be exempt from any approval or may be ranged under a less stringent category of approval.

Another advantage of a water separator according to the invention is that it becomes possible to work with a low gas/water volume ratio, as a result of which the water injection pressure can be built up considerably faster when starting up than with conventional water separators, such that the rotors and the bearings can be provided very quickly with a sufficient amount of water for an efficient cooling and lubrication.

The present invention also concerns a compressor installation which is provided with a water-injected compressor with an air inlet and a compressed air outlet, whereby this compressor installation is further provided with a water separator as described above, and whereby the above-mentioned compressed air outlet of the compressor is connected to the inlet of this water separator.

In order to better explain the characteristics of a water separator according to the invention, the following preferred embodiments of a water separator according to the invention for a compressor and a compressor installation provided with such a water separator are described as an example only without being limitative in any way, with reference to the accompanying drawings, in which:

figure 1 schematically represents a section of a water separator according to the invention for a water- injected compressor; figure 2 represents a section according to line II-II in figure 1; figure 3 schematically represents a compressor installation provided with a water separator according to figure 1; figure 4 represents the part indicated by F4 in figure

3 to a larger scale; figure 5 represents the part indicated by F5 in figure

4 to a larger scale; figures 6 and 7 represent variants according to figures 2 and 4 respectively; figure 8 represents a variant according to figure 1.

Figure 1 represents a water separator 1 according to the invention which mainly consists of a predominantly L-shaped reservoir 2 with an upwardly directed, in this case vertical leg 3, and a transversely directed leg 4, which in this case includes an angle with the upwardly directed leg 3, but which may also be placed at right angles to this upwardly directed leg 3.

In the given example, the legs 3 and 4 are formed of round pipes which are mitred at the connection between both pipes and which are welded together on site, for example, and whereby the free ends are sealed.

The inner diameter of the respective legs 3 and 4 is preferably smaller than or equal to 15.24 cm (6 inch), such that the water separator 1 may be exempt from any approval according to the ASME standards, or even smaller, such that the water separator 1 ends up within a less stringent category of approval according to the PED standard (Pressure Equipment Directive) .

The total height H of the upwardly directed leg 3 amounts to 470 millimetres in this example, whereas the total length L of the diagonal leg amounts to 800 millimetres.

On the above-mentioned upwardly directed leg 3 is provided a crosswise inlet 5, preferably placed tangentially, for a mixture of compressed gas and water, coming from the outlet of a compressor, whereas on the top free end of this upwardly directed leg 3 is also provided a compressed air outlet 6 onto which is connected a minimum pressure valve 7.

At the inlet 5 for the mixture of compressed gas and water is provided a central, in this case conical tube 8 in the upwardly directed leg 3, surrounded by a row of inlet guide vanes 9, also called "swirls", as is represented in more detail in figure 4.

In the upwardly directed leg 3 is further provided a drip system 10, which in this case is made in the shape of what is called an "impinger", which, as is known, consists of a conical ring 11, provided against the outer wall of the above-mentioned tube 8, and which widens according to the direction of flow of the gas, and whereby the free end of the above-mentioned conical ring narrows again over a short length, as is represented in more detail in figure 5.

At the bottom, the upwardly directed leg 3 is provided with a branching point 12 for water.

Also the diagonal leg 4 is provided with an outlet opening 13 for the separated water, preferably near its free end.

In this case, but not necessarily, the water separator 1 is further also provided with reversing means 14 for gas, which reversing means 14 are in this case made in the shape of a small plate 15, provided in the above-mentioned reservoir 2 for example by means of welding.

In this case, the above-mentioned plate 15 is provided at the connection between the upwardly directed leg 3 and the diagonal leg 4. s is represented in more detail in figure 2, the plate 15 is in this case perforated, and said plate 15 has radial outside dimensions corresponding to the radial inside dimensions of the reservoir 2 at the connection between the upwardly directed leg 3 and the bottom leg 4 of said reservoir 2.

The plate 15 must not necessarily be mounted at the connection between the upwardly directed leg 3 and the diagonal leg 4, but it may also be entirely provided in the diagonal leg 4 or in the upwardly directed leg 3, at different angles in relation to the legs 3 and 4 concerned.

According to a preferred characteristic, the water separator is finally also provided with a level controller 16 for the water level in the water separator 1, whereby this level controller 16 is connected to measuring means for the water level in the water separator 1, which measuring means comprise a minimum and a maximum level sensor 17, 18 respectively, and whereby these measuring means in this case are made in the shape of a measuring probe which, as is represented in figure 1, is placed vertically via the diagonal leg 4 in the upwardly directed leg 3.

Figure 3 represents a compressor installation comprising a water-injected compressor 19, which in this case is made in the shape of a screw compressor, and which is driven by driving means, for example in the shape of an electric motor 20 with a variable rotational speed.

The air inlet 21 of the compressor 19 is in this case connected via an inlet pipe 22 to an air inlet filter 23 which can be made for example in the form of a wet filter with water supply.

The air inlet filter 23 mainly consists of a housing 24 with an air inlet 25 and an air outlet 26 onto which the above-mentioned inlet pipe 22 is connected. In said housing 24 is provided a substrate 27 through which the sucked-in air is sent through.

Preferably, the above-mentioned air inlet filter 23 is also provided with an element 28, or what is called a "demister", to stop water drops in the gas flow, and with a water drain 29 for polluted water.

The above-mentioned substrate 27 and the element 28 are preferably both made in the form of a material with an open cell structure, such as for example in the form of polyurethane foam, polyethylene or the like.

The above-mentioned water supply of the air inlet filter 23 comprises a supply line 30 on the one hand, which is connected to the above-mentioned branching point 12 of the water separator 1, and in which has been provided a first controlled valve 31, and a supply device 32 for additional water on the other hand, which in this case mainly consists of a supply line 33 of for example tap water, in which have been provided a second controlled valve 34 and a water filter 35.

Both supply lines 30 and 33 are connected to the air inlet filter 23 via a nozzle 36, 37 respectively, whereby both nozzles 36 and 37 preferably open in the housing 24, in particular between the substrate 27 and the element 28, and both are preferably made of rustproof nonferrous metal. Said nozzles 36. and 37 preferably both have an inner filter as well so as to prevent any obstruction of the very fine nozzle.

At least one of the above-mentioned controlled valves 31 and 34, and in this case both valves 31 and 34, are connected to the above-mentioned level controller 16.

The above-mentioned water filter 35 in the line 33 is preferably, but not necessarily, made in the shape of an absolute water filter with a filter fineness of for example five micrometer, and whose so-called β-value is equal to 1000 or, in other words, whose output is equal to 99.9%.

By the term β-value is meant here, as is known, the ratio between the number of particles with a certain size that are found in the water flow before the filtering, and the number of particles of the same size that are found in the water flow after the filtering.

The compressed air outlet 38 of the compressor 19 is connected to the inlet 5 of the water separator 1 via a compressed air line 39 according to the invention.

Moreover, to the above-mentioned outlet opening 13 of the water separator 1 is connected an injection line 40, which is connected to the compression room of the compressor 19. According to a special characteristic of the invention, a water filter which is not represented in the drawings may be provided in the above-mentioned injection line 40, which can be integrated in the compressor 19, for example.

However, it is not excluded according to the invention for this water filter to be integrated in the water separator 1.

To the minimum pressure valve 7 at the compressed air outlet 6 of the water separator 1 is connected a line 41 for supplying compressed gas to a network of consumers.

The lines 40 and 41 are in this case provided with a common heat exchanger 42 which is in this case air-cooled by means of a fan 43. Naturally, in these lines can also be provided separate heat exchangers, and these heat exchangers may be of any type whatsoever, such as on the basis of a liquid cooling agent, air-cooled or the like.

In the line 41, downstream of the above-mentioned heat exchanger 42, is provided an additional water separator 44, which in this case is made in the shape of a rustproof cyclone separator, provided with a condensate drain at the bottom, which is connected to the compression room of the compressor 19 via a line 45.

It is clear that this additional water separator 44 can also be made as another type of water separator or dryer, for example in the form of a lyophilizer, which is also advantageous in that a feedback can be provided, for example to the inlet of the compressor 19.

The working of a compressor installation which is provided with a water separator 1 according to the invention is very simple and as follows.

While the compressor 19 is being driven by the motor 20, ambient air or another gas or mixture of gases is sucked in through the air inlet filter 23 and via the inlet pipe 22, which is compressed by the compressor 19 and guided to the water separator 1 via the compressed air line 39.

In the air inlet filter 23, depending on the control algorithm used by the level controller, which will be further discussed hereafter, water is sprayed inside the housing 24 via at least one of the nozzles 36 and 37.

Water drops splashing down moisten the cellular substrate 27 and go down through said substrate 27 to the water outlet 29, as a result of which the substrate 27 gets entirely wet. Water drops splashing up are stopped by the element 28 which also has a cellular structure, such that only the bottom side of this element 28 is moistened, thus preventing water drops from entering the inlet pipe 22.

The sucked-in air which ends up in the air inlet filter 23 via the air inlet 25 flows counterflow with the descending drops in the substrate 27, as a result of which this air is purified and moistened by these water drops.

The major part of these drops will be discharged, together with the dust particles that have been gathered in the substrate 27, via the water outlet 29, while part of the drops evaporate and end up in the gas flow.

The filtered and moistened gas flows through the element 28 to the air outlet 26 of the air inlet filter 23 and is then sucked in via the inlet pipe 22 through the compressor 19 in which the gas is compressed.

Since water is injected into the compression room of the compressor 19 for the lubrication, cooling and sealing of the moving parts, the compressed gas leaving the compressor 19 will contain an amount of water in the shape of drops, spray and mist.

As is represented by arrow A in figure 4, the mixture of compressed gas and water enters the reservoir 2 of the water separator 1 via the tangential inlet 5.

Thanks to the presence of the inlet guide vanes 9, as is known, a downward helical motion is provided to the gas and water mixture, as a result of which the relatively heavy water drops, under the influence of the centrifugal force, are flung against the inner wall of the reservoir 2 and descend towards the lower, diagonal leg 4 under the influence of gravitation.

Water drops sticking to the outer wall of the tube 8 go down in the direction of the drip system under the influence of gravitation, which system forms a shelter as if it were along which the drops drip down, such that these drops are prevented from being carried along via the compressed air outlet 6 through the gas flow leaving the water separator 1 via the minimum pressure valve 7.

Because of the restricted amount of gas in the reservoir 2, a pressure is built up fast in the water separator 1 when the compressor 19 is started up, such that the water injection pressure will be built up fast and the water which has been gathered at the bottom in the diagonal leg 4 of the reservoir will be injected via the injection line 40 in the compression room 15 of the compressor 19, after having been cooled in the heat exchanger 42.

A major advantage thereof is that no pump must be provided to pump the separated water back from the water separator to the compressor 19.

The water which leaves the water separator 1 via the outlet opening 13 contains a minimum of air bells of for example less than 0.4 percent of air.

The presence of the above-mentioned reversing means 14 in the water separator 1 prevents gas bells from entering in the diagonal leg 4 of the reservoir 2, as a result of which they could be carried along via the injection line 40 to the compressor 19.

As the legs 3 and 4 of the reservoir 2 enclose an angle which is larger than 90°, this prevents any possible gas bells which might still end up in the diagonal leg 4 from gathering against the upper wall of said diagonal leg 4 and from moving to the upwardly directed leg 3 thanks to their rising power.

The compressed gas which leaves the water separator 1 via the minimum pressure valve 7 contains a minimum of water particles of for example less than 0.5 litre per hour, and it is carried to the additional water separator 44 via the heat exchanger 42 through the line 41, where any possible condensation drops that have been created as a result of the cooling in the heat exchanger 42 are separated by the cyclone operation and are subsequently carried back to the compressor 19 via the line 45 so as to be injected in the compression room.

The compressed gas which leaves the additional water separator 44 is ready for use and may for example be used for all sorts of compressed air applications.

If required, use can further be made of a level control for the water level in the water separator 1, whereby, according to a preferred characteristic of the invention, the water level in the water separator 1 which is adjusted, is larger than the diameter of the diagonal leg 4 and, in this case, is at least 10 millimetres larger than the diameter of the diagonal leg 4.

According to a preferred characteristic, the above- mentioned level control is carried out such that the water separator 1 is always filled for at least 2/3 of its volume with water, as a result of which the above-mentioned advantage of the water injection pressure being built up fast is optimal.

If the water level is situated at a certain level which is measured by the above-mentioned maximum level sensor 18, the level controller 16 will respond to it by opening the first valve 31, such that, under the influence of the pressure increase in the water separator 1, water will be pressed to the nozzle 36 via the supply line 30 and it will be injected in the air inlet filter 23.

When more water vapour is carried off together with the compressed air via the line 41 than enters with the sucked- in gas via the inlet pipe 22, and, in other words, water is being consumed, the water level in the water separator 1 will drop.

This is for example the case in winter, when the absolute humidity of the ambient air is smaller than or equal to 2g/kg.

In this case, as soon as a certain minimum water level is reached in the water separator, the supply device 32 for additional water will be activated, as the level controller 16 opens the second valve 34, whereas the first valve 31 in the supply line 30 between the water separator 1 and the air inlet filter 23 is closed.

The additional water which is supplied via the supply line 33 is initially sent through the water filter 35, such that any possible pollution that may be present in this additional water can be filtered. The additional water is subsequently injected in the air inlet filter 23 by the nozzle 37, where the substrate 27 is moistened, in a .manner analogous to the one described above, and the air is purified and moistened by the water drops.

Thanks to the supply of additional water via the second valve 34, the water level in the water separator 1 will rise until the maximum water level is reached, upon which the valve 34 in the supply device 32 is closed again and the first valve 31 is opened again.

Figure 6 represents a variant of a plate 15 according to figure 2, whereby the radial outside dimensions of this plate 15 are considerably smaller in this case than the radial inside dimensions of the reservoir 2, and whereby this plate 15 is fixed to the inner wall of the reservoir 2 by means of legs.

Figure 7 represents a variant according to figure 4, whereby in this case the inlet 5 is provided axially on the upwardly directed leg 3, such that the incoming mixture of compressed gas and water flows axially in the upwardly directed leg 3.

According to a preferred characteristic which is not represented in the drawings, the inlet 5 of the water separator 1 is connected directly, without any coupling, pipe or the like, to the compressed air outlet 38 of the compressor 19. Thus can be obtained an even more compact and simple compressor installation.

Figure 8 represents a variant of a water separator according to figure 1, whereby in this case the above- mentioned measuring means for the water level in the water separator 1 comprise an external line 46, connected at two different heights to the upwardly directed leg 3 and whereby, in this external line 46, the minimum and maximum level sensors 17, 18 respectively have been provided, and whereby these level sensors 17 and 18 are connected to the above-mentioned level controller 16.

According to an embodiment which is not represented in the drawings, the above-mentioned reversing means 14 can be made in the form of a substrate which has been provided in the reservoir 2.

In the given example, the upwardly directed leg 3 of the water separator 1 is provided with a branching point 12, whereas the diagonal leg 4 is provided with an outlet opening 13.

Naturally, these openings can also be replaced by a single opening onto which is connected one common line, with a first branch which is connected to the compressor 19, and a second branch forming a supply line for the air inlet filter 23. or is it necessary, according to the invention, for the air inlet filter 23 to be made as a wet filter; on the contrary, this air inlet filter 23 can also be made as any other type of filter.

It is clear that, instead of a motor 20 with a variable rotational speed, also other types of drives may be provided.

The advantage of driving the compressor 19 at a variable rotational speed consists in that no inlet valve, or what is called an "unloader", should be provided on the air inlet 21 of the compressor 19.

The present invention is by no means restricted to the embodiments described as an example and represented in the accompanying drawings; on the contrary, such a water separator according to the invention for a water-injected compressor and a compressor installation comprising such a water separator can be made in all sorts of shapes and dimensions while still remaining within the scope of the invention.

Claims

Claims .

1.- Water separator (1) for a water-injected compressor, comprising a reservoir (2), which is provided with an inlet (5) for a mixture of compressed gas and water, with an outlet (6) for compressed gas and with an outlet opening

(13) for separated water, characterised in that this reservoir (2) is predominantly L-shaped with an upwardly directed leg (3) on which the above-mentioned inlet and the outlet for compressed gas are provided and a transversely directed leg (4) in which the above-mentioned outlet opening (13) is provided.

2.- Water separator according to any one of the preceding claims, characterised in that the—inside diameter of the respective legs (3 and 4) of the reservoir (2) is smaller than or equal to 15.24 centimetres (6 inch).

3.- Water separator according to any one of the preceding claims, characterised in that it is provided in the upwardly directed leg (3) of a central tube (8) , surrounded by a row of inlet guide vanes (9), downstream of the inlet.

4.- Water separator according to any one of the preceding claims, characterised in that it is provided with a drip system (10) .

5.- Water separator according to claim 3 and 4, characterised in that the above-mentioned drip system (10) is made in the shape of a conical ring (11) provided on the outer wall of the above-mentioned tube (8) and which widens in the direction of the gas flow, and whereby the free end of the above-mentioned conical ring (11) narrows again over a short length.

6.- Water separator according to any one of the preceding claims, characterised in that the above-mentioned inlet (5) is directed transversely to the above-mentioned upwardly directed leg (3) .

7. - Water separator according to any one of the preceding claims, characterised in that the above-mentioned inlet (5) is axially directed to the above-mentioned upwardly directed leg (3) .

8. - Water separator according to any one of the preceding claims, characterised in that it is provided with reversing means (14) for the gas.

9.- Water separator according to claim 8, characterised in that the above-mentioned reversing means (14) are made as a plate (15) provided in the above-mentioned reservoir (2) .

10.- Water separator according to claim 9, characterised in that the above-mentioned plate (15) is made in the shape of a perforated plate.

11.- Water separator according to claim 9 or 10, characterised in that the radial outside dimensions of the above-mentioned plate (15) are smaller than the radial inside dimensions of the above-mentioned reservoir (2).

12.- Water separator according to claim 8, characterised in that the above-mentioned reversing means (14) are made as a substrate provided in the reservoir (2).

13.- Water separator according to any one of claims 8 to 12, characterised in that the above-mentioned reversing means (14) are provided in the reservoir (2) at the connection between the above-mentioned legs (3 and 4).

14.- Water separator according to any one of claims 8 to 12, characterised in that the above-mentioned reversing means (14) are provided in the upwardly directed leg (3) or in the transversely directed leg (4), either or not at a certain angle to the respective legs (3 and 4) .

15.- Water separator according to any one of the preceding claims, characterised in that it is provided with a level controller (16) for the water level in the water separator (1).

16.- Water separator according to claim 15, characterised in that the above-mentioned level controller (16) is connected to measuring means for the water level in the water separator (1), whereby the measuring means comprise a measuring probe erected vertically in the upwardly directed leg (3) .

17.- Water separator according to claim 15, characterised in that the level controller (16) is connected to measuring means for the water level in the water separator (1), whereby these measuring means comprise an external line which is connected at two different heights to the upwardly directed leg (3) and in which are provided a minimum and a maximum level sensor (17, 18 respectively) .

18.- Water separator according to any one of claims 15 to 17, characterised in that the level which is adjusted is larger than the diameter of the diagonal leg (4) .

19.- Water separator according to any one of claims 15 to 18, characterised in that the level is adjusted such that the water separator (1) is always filled with water for at least 2/3 of its volume.

20.- Water separator according to any one of claims 15 to 19, characterised in that the above-mentioned level controller (16) is connected to a minimum and maximum level sensor (17, 18 respectively) in the water separator (1) on the one hand, and to controlled valves (31, 34 respectively) on the other hand which are provided in water supply lines (30, 33 respectively) .

21.- Water separator according to any one of the preceding claims, characterised in that it is provided with an integrated water filter.

22,- Compressor installation which is provided with a compressor (19) with an air inlet (21) and a compressed air outlet (38), characterised in that the compressor installation is further provided with a water separator (1) according to any one of the preceding claims, and in that the above-mentioned compressed air outlet (38) of the compressor (19) is connected to the inlet (5) of this water separator (1) .

23.- Compressor installation according to claim 22, characterised in that it is provided with an air inlet filter (23) , provided in an inlet pipe (22) which is connected to the air inlet (25) of the compressor (19) ; and in that the above-mentioned air inlet filter (23) is made as a wet filter, provided with a water supply, which comprises a supply line (30) .

24.- Compressor installation according to claim 23, characterised in that the above-mentioned supply line (30) is connected to a branching point (12) of the water separator (1) .

25.- Compressor installation according to claim 23, characterised in that the above-mentioned supply line (30) forms a branch of a line which is connected to an outlet opening (13) of the water separator.

26.- Compressor installation according to any one of claims 23 to 25, characterised in that the above-mentioned water supply further comprises a supply device (33) for additional water.

27.- Compressor installation according to any one of claims 22 to 26, characterised in that it is provided with a level controller (16) for the water level in the water separator (1).

28.- Compressor installation according to claims 26 and 27, characterised in that the above-mentioned level controller (16) is connected to a minimum and maximum level sensor (17, 18 respectively) in the water separator (1) on the one hand, and to two controlled valves on the other hand, namely a first controlled valve (31) provided in the above- mentioned supply line (30) between the water separator (1) and the air inlet filter (23) , and a second controlled valve (34) which is provided in the above-mentioned supply device (33) for additional water respectively.

29.- Compressor installation according to any one of claims 22 to 28, characterised in that the inlet (5) of the water separator (1) is connected directly, without any coupling, line or the like, to the compressed air outlet (38) of the compressor (19).

30,- Compressor installation according to any one of claims 22 to 29, characterised in that it is provided with an injection line (40) which connects the above-mentioned water separator (1) to the compressor (19) for the injection of water in the compression room, and in that in the above-mentioned injection line (40) has been provided a water filter which is integrated in the compressor (19) .

31.- Compressor installation according to any one of claims 22 to 30, characterised in that the above-mentioned compressor (19) is driven by means of a motor at a variable rotational speed, and in that there is no inlet valve on the air inlet (21) of the compressor , (19) .

32.- Compressor installation according to claim 22, characterised in that it is provided with an air inlet filter (23), provided in an inlet pipe (22) which is connected to the air inlet (25) of the compressor (19) ; and in that the above-mentioned air inlet filter (23) is made as another type of filter than a wet filter.