EP1536062B1 - Twin wire former for a machine for producing a fibrous web and corresponding method - Google Patents

Abstract

The machine for the production of a paper or cardboard web (2) has a twin-fourdrinier section (1) to take the pulp (3) from the stock inlet (7), with two continuous fourdriniers (4,5). Water is extracted from the pulp through the fourdriniers by a suction unit (10). At least one suction unit (20.1-20.5) is in the path of each fourdrinier to extract clouds (22) of steam and the like.

Description

The invention relates to a twin-wire former for a machine for producing a fibrous web, in particular a paper or board web, from at least one pulp suspension, with two continuous endless screens, which converge to form a wedge-shaped Stoffeinlaufspalts which receives the pulp suspension directly from a headbox, and then form a Doppelpsiebstrecke, in which-seen in Sieblaufrichtung- the two screens at least one, in the direction of wire direction successively arranged forming unit and dewatering unit, each remove at least by means of negative pressure water from the introduced between the two sieves pulp suspension through the respective sieve, and then from each other are separated, wherein the forming fibrous web remains on a sieve, according to the preamble of claim 1.

The invention further relates to a process for producing a fibrous web, in particular a paper or board web, from at least one fibrous suspension according to the preamble of claim 19.

Such a twin-wire former is, for example, the two German Offenlegungsschriften DE 198 03 591 ( PB10656 EN ) and DE 196 51 493 A1 ( PB10449 DE ) of the applicant. It is now used in the manufacture of paperboard and packaging papers at low production speeds, and in the future these grades are also to be produced at higher production speeds. Thus, drastically increases the problem of contamination of the twin wire former and adjacent assemblies due to the increased entrainment of steam, such as water vapor mist and the same. This entrainment of windrows is particularly important in the coarser screen types used for the production of cardboard and packaging papers, since they carry much larger amounts of steam than, for example, the narrower screen types for high-speed paper machines, in particular for newspaper printing. The entrained amounts of steam lead predominantly to deposits in the area of the twin-wire former, possibly also in adjacent assemblies. Now dissolve such deposits from their deposition sites, in particular moving or stationary machine parts, and get them on one of the two screens or even between the two screens, it is certain to a web break, which makes a new listing of the fibrous web necessary and thus leads to production losses and cost disadvantages.

It is therefore an object of the invention to provide a Doppelsiebformer and a method of the aforementioned types, with which on the one hand, a deposition of deposits in the field of Doppelsiebformers and adjacent assemblies is considerably reduced or completely prevented and on the other hand, no technological disadvantages due to an altered construction in the field of Twin-wire former must be accepted.

This object is achieved in a twin-wire former according to the invention in that at least one suction device is provided with at least one suction opening for discharging swaths in the respective course of at least one of the two screens. This extraction device according to the invention causes a fast and efficient extraction of swaths, moreover as close as possible to the place of their formation.

The suction device is designed as at least a two-chamber system, the first larger, preferably top-mounted chamber for collecting and discharging the water and the second smaller, preferably mounted on the underside chamber for collecting and discharging the air is designed, the first chamber preferably in the discharge direction aligned guide system, in particular vanes, and wherein the supply of air into the second chamber by means of laterally above the first chamber beginning and opening into the second chamber channels.
So that the smallest possible amount of ambient air is extracted, the clear distance between the suction opening and the adjacent sieve is minimized, preferably less than 300 mm.

The suction device is preferably provided in a region of the course of the corresponding screen, in which the screen is not in direct contact with the fibrous web to be produced. This completely avoids a possible influence of the suction device on the fibrous web to be produced.

Moreover, the efficiency of the suction device is not imperceptibly increased thereby.

Furthermore, the suction device, which is preferably designed as a slot suction device, as a hood suction device or as a space suction device, be arranged inside or outside the loop of the endless screen. The slot extraction is conveniently arranged in the region of a free run of the corresponding screen, whereas the hood extraction is preferably arranged in the region of a deflection of the corresponding screen, wherein in the region of the deflection preferably at least one HD spray tube for acting on the screen with a cleaning medium , in particular cleaning liquid, is attached.

The suction device extends ideally over the entire width of the fibrous web to be produced, wherein the suction opening and / or a plurality of suction openings, which are preferably designed as suction nozzles, can extend over the entire width of the fibrous web to be produced.

Moreover, in a preferred embodiment, the suction openings or the suction nozzles are combined into two or more sections with at least two suction openings or suction nozzles per section, wherein preferably each section of suction openings or suction nozzles can be assigned throttle valves or the like. This allows adjustability of the sectional suction.

With regard to the most efficient extraction possible, it is provided that the suction openings or suction nozzles preferably have polygonal suction contours. The polygonal suction contours of the suction openings or suction nozzles may be rectangles and / or squares and / or rhombuses and / or ellipses and / or ovals and / or circles.

Furthermore, the suction device has at least one controllable suction pump. In particular, the suction device has two controllable suction pumps, two controllable exhaust fans or the like, which suck on the driver's or drive side half of the plurality of suction openings, and / or each section of suction or extraction nozzles has a suction pump, an exhaust fan or similar with controllable / preferably and preferably single drive on and / or each suction opening or each suction nozzle has a suction pump, an exhaust fan or the like with controllable / controllable and preferably single drive.

Thus, a sufficient suction of swaths is possible, the suction pump, the exhaust fan or the like a controllable / controllable extraction volume in the range of 1 to 40 m ³ / h per m working width per m / min screen speed, preferably from 1.4 to 25 m ³ / h per meter working width per m / min screen speed, up. The suction pump, the exhaust fan or the like in this case generates a controllable / suction speed in the range of 10 to 25 m / s, preferably from 12 to 20 m / s.

The inventive output is procedurally achieved in that at least one of the two screens in the respective course is acted upon by at least one suction device with at least one suction opening for the removal of steam. The suction device is again designed as a two-chamber system. This inventive method causes a quick and efficient extraction of windrows, moreover as close as possible to the place of their formation.

Further advantageous embodiments of the invention will become apparent from the procedural subclaims.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the drawings.

Figur 1:

eine schematisierte Seitenansicht eines Doppelsiebformers mit erfindungsgemäßen Absaugeinrichtungen; und

Figuren 2 bis 4:

schematisierte Ansichten von verschiedenen Absaugeinrichtungen.

Figur 5:

schematisierte Ansicht einer erfindungsgemäßen Absaugeinrichtung.

Show it

FIG. 1:

a schematic side view of a Doppelsiebformers with suction devices according to the invention; and

FIGS. 2 to 4:

Schematic views of various suction devices.

FIG. 5:

schematic view of a suction device according to the invention.

The FIG. 1 shows a schematic side view of a twin-wire former 1 of a machine for producing a fibrous web 2, in particular a paper or board web, from at least one pulp suspension 3, with two continuous endless sieves (bottom wire 4, top wire 5), forming a wedge-shaped Stoffeinlaufspalts 6, the directly from a headbox 7 receives the pulp suspension 3, converge and then form a Doppelsiebstrecke 8, in which -in Sieblaufrichtung S (arrow) seen- the two wires 4, 5 at least one, in the direction of wire direction S (arrow) successively arranged forming unit 9 and Dewatering unit 10, each of which at least by means of negative pressure water from the introduced between the two sieves 4, 5 pulp suspension 3 through the respective sieve 4, 5, pass and then separated from each other, wherein the forming fibrous web 2 remains on the wire 4.
The headbox 7 can also be used as a multi-layer headbox and / or as a headbox with sectioned dilution water technology ("Module Jet" system). DE 40 19 593 A1 ( PA04598 EN ) of the applicant).

In the area of the wedge-shaped Stoffeinlaufspalts 6, the lower wire 4 passes over a peripheral portion 11 of a preferably evacuated forming roller 12 with indicated vacuum device and the top wire 5 passes over a peripheral portion 13 of a breast roll 14. The formed by the two wires 4, 5 Doppeltelsiebstrecke 8 runs after the expiry of the forming roller 12 at an angle α from -50 ° to + 50 ° to an imaginary vertical plane V down. At the end of a deflection device 15, in particular a guide roller 15.1 is arranged, which deflects the two wires 4, 5 in a preferably substantially horizontal direction L (arrow). After the diversion and at the end of the double-wire section 8, the two wires 4, 5 run over a separating device 16 which separates the top wire 5 from the fibrous web 2 formed and the bottom wire 4. The top wire 5 runs over guide rollers 17 back to the breast roller 14, whereas the bottom wire 4 is guided with the fibrous web 2 thereon via an optional Siebsaugwalze 18 to a pickup roller 19, before then it also runs over guide rollers 17 back to the forming roller 12.

The twin-wire former 1 shown here according to the embodiment of the already mentioned German Offenlegungsschrift DE 198 03 591 A1 ( PB10656 EN ) of the applicant can in a further embodiment according to the embodiment of German patent application DE 196 51 493 A1 ( PB10449 DE ) of the applicant. In other words, the possible execution of the twin-wire former is not intended to be based on the embodiment according to the FIG. 1 be limited, the execution according to the FIG. 1 is intended to be merely exemplary in nature of a variety of possible embodiments for the twin-wire former.

In the respective course of at least one of the two screens 4, 5 is now at least one schematically indicated suction device 20 with at least one suction opening 21 for the removal of windrows 22 is provided. It is provided that the suction device 20.1 to 20.5 is provided in a region of the course of the corresponding screen 4, 5, in which the screen 4, 5 is not in direct contact with the fibrous web 2 to be produced. The in the FIG. 1 schematically indicated suction 20.1 to 20.5 are purely exemplary, both in terms of their number and their locations.

In the execution according to the FIG. 1 are three suction 20.1, 20.2 and 20.4 within the two loops of the endless screens 4, 5 and two suction devices 20.3, 20.5 outside the two loops of the endless screens 4, 5 are arranged.

The suction device 20.5 is formed as a Schlitzabsaugung and arranged in the region of a free run of the screen 5, whereas the suction device 20.3 is designed as a hood suction and is arranged in the region of a deflection of the sieve 4, wherein in the region of the deflecting element 17 (guide roller) preferably at least one known HD spray tube 23 for applying the sieve 4 with a cleaning medium 24, in particular cleaning liquid attached. The suction device may be formed in a further embodiment as a specially designed Raumabsaugungseinrichtung.

Furthermore, the clear distance A between the suction opening 21 and the adjacent wire 4 is minimized, preferably less than 300 mm, and each suction device 20.1 to 20.5 extends over the entire width B of the fibrous web 2 to be produced.

The FIGS. 2 to 5 show schematic views of various suction devices 20.

In the FIG. 2 shown suction device 20 has, by way of example, two, preferably a plurality of suction openings 21, which extend ideally over the entire width B of the fibrous web 2 to be produced with a screen direction S (arrow), wherein the screen 4 (5) is guided over a guide roller 17 , The illustrated suction device 20 is a slot suction with polygonal suction openings 21 and suction nozzle 25 in the form of rectangles. The size and the distance between the rectangles are selectable. Furthermore, the suction device 20 has two controllable and controllable and schematically illustrated suction pumps 26, the leader or drive side, the half of the plurality of suction holes 21; the suction channel 27 of the suction device 20 is in this case advantageously divided in the middle (dash-dot line). With the reference numeral can also be schematically illustrated an exhaust fan or the like; this applies to everyone FIGS. 2 to 5 ,

In the FIG. 3 shown suction device 20 is as a over the entire width B of the produced fibrous web 2 of time away extending hood extraction is formed and it is arranged in the region of a deflection of the screen 4 (5), wherein in the region of the deflecting element 17 (guide roller) an HD spray tube 23 for applying the sieve 4 (5) with a cleaning medium 24, in particular cleaning liquid attached. The suction device may be formed in a further embodiment as a specially designed Raumabsaugungseinrichtung. The suction device 20 has in FIG. 3 two, preferably a plurality of exhaust ports 21 designed as suction. Each suction opening 21 or each suction nozzle 25 has a suction pump 26 with controllable / controllable and preferably single drive 27, the in FIG. 4 are shown in detailed form. Furthermore, the clear distance A between the suction openings 21 and the adjacent wire 4 (5) is minimized, preferably less than 300 mm.

Also in FIG. 4 shown suction device 20 is designed as a "slot suction", which has a plurality of extending over the entire width B of the fibrous web 2 to be produced suction openings 21 with corresponding suction nozzle 25 and a common suction channel 27. The "Schlitzabsaugung" can be performed in a further embodiment with only a single slot (dashed line). The suction openings 21 and the suction nozzle 25 have polygonal suction contours, in FIG. 4 these are circles. Furthermore, the polygonal suction contours of the suction openings 21 or suction nozzles 25 can also be rectangles and / or squares and / or rhombuses and / or ellipses and / or ovals, this list of suction contours having merely exemplary character. The suction device 20 of the FIG. 4 has a controllable / suction pump 26 with controllable / controllable single drive 27, such as an electric motor, on.

In continuation, the suction openings 21 and the suction nozzle 25 of the suction device 20 of the FIG. 4 also be combined into two or more sections with at least two suction openings 21 and exhaust port 25 per section. There are preferably associated with each section of suction openings 21 or suction 25 throttle valves 28 or the like, in turn, each section of suction openings 21 and suction nozzle 25 may have a suction pump 26 with controllable / controllable and preferably single drive 27. In the FIG. 4 By way of example, the two left-hand suction openings 21 and / or suction connection 25 are designed to form such a section N with a corresponding configuration.

In the FIG. 5 illustrated and extending over the entire width B of the fibrous web 2 to be produced away suction device 20 is inventively designed as at least a two-chamber system 29, the first larger, preferably upper-side chamber 29.1 for collecting and discharging the water 32 (arrow) and the second smaller, preferably The first chamber 29.1 preferably has a guide system 30 oriented in the discharge direction R (arrow), in particular guide vanes 30.1 known to the person skilled in the art, and wherein the supply of air 33 (FIG. Arrow) into the second chamber 29.2 by means of laterally above the first chamber 29.1 beginning and opening into the second chamber 29.2 channels 31 takes place.

Common to all the suction devices 20, 20.1 to 20.5 set out is that the at least one suction pump 26 has a controllable suction volume in the range from 1 to 40 m ³ / h per m working width per m / min wire speed, preferably from 1.4 to 25 m ³ / h per meter working width per m / min screen speed, and that the respective at least one suction pump 26 generates a controllable extraction speed in the range of 10 to 25 m / s, preferably 12 to 20 m / s.

The described twin-wire former 1 with a suction device 20 according to the invention is also particularly suitable for carrying out the method according to the invention, wherein at least one of the two wires 4, 5 in the respective Course is acted upon by means of at least one suction device 20 with at least one suction opening 21 for the removal of swaths 22.

In summary, it should be noted that the invention provides an improved twin-wire former and an improved method of the aforementioned types, with which on the one hand, deposition of deposits in the area of the twin-wire former and adjacent assemblies is considerably reduced or completely prevented and, on the other hand, no technological disadvantages due to a change Construction in the field of twin wire must be taken into account.

LIST OF REFERENCE NUMBERS

1

twin

2

Fibrous web

3

Fibrous suspension

4

Sieve (lower sieve)

5

Sieve (upper sieve)

6

Stock inlet gap

7

headbox

8th

twin-wire

9

forming unit

10

dewatering unit

11

Peripheral area (forming roller)

12

forming roll

13

Peripheral area (breast roll)

14

breast roll

15

deflecting

15.1

deflecting

16

separator

17

Guide roller (guide roller)

18

Suction roll

19

Pickup roll

20, 20.1 to 20.5

suction

21

suction

22

swath

23

HD spray pipe

24

cleaning media

25

suction

26

Suction pump, exhaust fan or similar

27

individual drive

28

throttle valve

29

Bicameral

29.1

First chamber

29.2

Second Chamber

30

Control System

30.1

vane

31

channel

32

Water (arrow)

33

Air (arrow)

A

distance

B

Width (fibrous web)

L

Running direction (arrow)

N

section

R

Discharge direction (arrow)

S

Sieblaufrichtung (arrow)

V

vertical plane

α

angle

Claims (35)

1. Twin wire former (1) for a machine for producing a fibrous web (2), in particular a paper or board web, from at least one fibrous suspension (3), having two circulating endless wires (4, 5) which, forming a wedge-shaped stock inlet gap (6) which accepts the fibrous suspension (3) directly from a headbox (7), run together and then form a twin wire section (8), in which - seen in the wire running direction (S) - the two wires (4, 5) each pass at least one forming unit (9) and dewatering unit (10) arranged one after the other in the wire running direction (S), which in each case, at least by means of negative pressure, remove water from the fibrous suspension (3) introduced between the two wires (4, 5) through the respective wire (4, 5) and after that are separated from each other, the fibrous web (2) forming remaining on one wire (4),
   characterized
   in that, in the respective course of at least one of the two wires (4, 5), at least one suction device (20, 20.1 to 20.5) having at least one suction opening (21) for extracting clouds of vapour (22) is provided, and
   in that the at least one suction device (20, 20.1 to 20.5) is designed as at least one two-chamber system (29), of which the first, larger chamber (29.1), preferably fitted on the top side, is designed to collect and extract the water (32) (arrow), and of which the second, smaller chamber (29.2), preferably fitted on the underside, is designed to collect and extract the air (33) (arrow), the first chamber (29.1) preferably having a guide system (30), in particular guide vanes (30.1), aligned in the extraction direction (R), and the air (33) being fed (arrow) into the second chamber (29.2) by means of channels (31) beginning laterally above the first chamber (29.1) and opening into the second chamber (29.2).
2. Twin wire former (1) according to Claim 1, characterized in that the suction device (20, 20.1 to 20.5) is provided in a region of the course of the corresponding wire (4, 5) in which the wire (4, 5) is not in direct contact with the fibrous web (2) to be produced.
3. Twin wire former (1) according to Claim 1 or 2, characterized in that the suction device (20, 20.1, 20.2, 20.4) is arranged inside the loop of the endless wire (4, 5).
4. Twin wire former (1) according to Claim 1 or 2, characterized in that the suction device (20, 20.3, 20.5) is arranged outside the loop of the endless wire (4, 5).
5. Twin wire former (1) according to one of the preceding claims, characterized in that the clear distance between the suction opening (21) and the adjacent wire (4, 5) is minimized, preferably less than 300 mm.
6. Twin wire former (1) according to one of the preceding claims, characterized in that the suction device (20, 20.1 to 20.5) extends over the entire width (B) of the fibrous web (2) to be produced.
7. Twin wire former (1) according to one of the preceding claims, characterized in that the suction opening (21) extends over the entire width (B) of the fibrous web (2) to be produced.
8. Twin wire former (1) according to one of Claims 1 to 6, characterized in that a plurality of suction openings (21) extends over the entire width (B) of the fibrous web (2) to be produced.
9. Twin wire former (1) according to Claim 8, characterized in that the suction openings (21) are combined into two or more sections having at least two suction openings (21) per section.
10. Twin wire former (1) according to Claim 9, characterized in that each section of suction openings (21) is preferably assigned throttle valves.
11. Twin wire former (1) according to Claim 10, characterized in that the suction openings (21) have polygonal suction contours.
12. Twin wire former (1) according to Claim 11, characterized in that the polygonal suction contours of the suction openings (21) are rectangles and/or squares and/or diamonds and/or ellipses and/or ovals and/or circles.
13. Twin wire former (1) according to one of the preceding claims, characterized in that the suction device (20, 20.1 to 20.5) has at least one suction pump that can be controlled/regulated, a suction fan that can be controlled/regulated or the like.
14. Twin wire former (1) according to Claim 13, characterized in that the suction device (20, 20.1 to 20.5) has two suction pumps, suction fans or the like that can be controlled/regulated, which, on the operators' side or drive side, apply suction to half of the plurality of suction openings (21).
15. Twin wire former (1) according to Claim 9, characterized in that each section of suction openings (21) has a suction pump, a suction fan or the like having a drive that can be controlled/regulated and is preferably individual.
16. Twin wire former (1) according to Claim 13, characterized in that each suction opening (21) has a suction pump, a suction fan or the like having a drive that can be controlled/regulated and is preferably individual.
17. Twin wire former (1) according to one of Claims 13 to 16, characterized in that the suction pump, the suction fan or the like has a suction volume that can be controlled/regulated in the range from 1 to 40 m³/h per m working width per m/min wire speed, preferably of 1.4 to 25 m³/h per metre working width per m/min wire speed.
18. Twin wire former (1) according to one of Claims 13 to 17, characterized in that the suction pump, the suction fan or the like produces a suction velocity that can be controlled/regulated in the range from 10 to 25 m/s, preferably from 12 to 20 m/s.
19. Method for producing a fibrous web (2), in particular a paper or board web, from at least one fibrous suspension (3), having two circulating endless wires (4, 5) which, forming a wedge-shaped stock inlet gap (6) which accepts the fibrous suspension (3) directly from a headbox (7), are led together and then form a twin wire section (8), in which - seen in the wire running direction (S) - the two wires (4, 5) are each led over at least one forming unit (9) and dewatering unit (10) arranged one after the other in the wire running direction (S), which in each case, at least by means of negative pressure, remove water from the fibrous suspension (3) introduced between the two wires (4, 5) through the respective wire (4, 5) and after that are separated from each other, the fibrous web (2) forming remaining on one wire (4),
    characterized
    in that at least one of the two wires (4, 5), in the respective course, is acted on by at least one suction device (20, 20.1 to 20.5) having at least one suction opening (21) for extracting clouds of vapour (22), and
    in that the action is provided by means of at least one suction device (20, 20.1 to 20.5) designed as at least one two-chamber system (29), of which the first, larger chamber (29.1), preferably fitted on the top side, is designed to collect and extract the water (32) (arrow), and of which the second, smaller chamber (29.2), preferably fitted on the underside, is designed to collect and extract the air (33) (arrow), the first chamber (29.1) preferably having a guide system (30), in particular guide vanes (30.1), aligned in the extraction direction, and the air (33) being fed (arrow) into the second chamber (29.2) by means of channels (31) beginning laterally above the first chamber (29.1) and opening into the second chamber (29.2).
20. Method according to Claim 19, characterized in that the action is carried out in a region of the course of the corresponding wire (4, 5) in which the wire (4, 5) is not in direct contact with the fibrous suspension (3).
21. Method according to Claim 19 or 20, characterized in that the action is carried out by a suction device (20, 20.1, 20.2, 20.4) arranged inside the loop of the endless wire (4, 5).
22. Method according to Claim 19 or 20, characterized in that the action is carried out by a suction device (20, 20.3, 20.5) arranged outside the loop of the endless wire (4, 5).
23. Method according to one of Claims 19 to 22, characterized in that the action on the wire (4, 5) is carried out in the region of its deflection.
24. Method according to one of Claims 19 to 23, characterized in that the clear distance between the suction opening (21) and the adjacent wire (4, 5) is minimized, preferably set to be less than 300 mm.
25. Method according to one of Claims 19 to 24, characterized in that the action on the fibrous web (2) to be produced is preferably carried out over the entire width (B).
26. Method according to one of Claims 19 to 25, characterized in that the action on the fibrous web (2) to be produced is preferably carried out over the entire width (B) by means of a suction opening (21).
27. Method according to one of Claims 19 to 25, characterized in that the action on the fibrous web (2) to be produced is preferably carried out over the entire width (B) by means of a plurality of suction openings (21), which are preferably combined into sections (N).
28. Method according to Claim 27, characterized in that the action on the fibrous web (2) to be produced is carried out by suction openings (21), which are combined into two or more sections having at least two suction openings (21) per section.
29. Method according to Claim 28, characterized in that each section of suction openings (21) is preferably assigned throttle valves or the like.
30. Method according to one of Claims 19 to 29, characterized in that the action on the suction device (20, 20.1 to 20.5) is carried out by at least one suction pump that can be controlled/regulated, a suction fan that can be controlled/regulated or the like.
31. Method according to Claim 30, characterized in that the action on the suction device (20, 20.1 to 20.5) is carried out by two suction pumps that can be controlled/regulated, two suction fans that can be controlled/regulated or the like, which, on the operators' side or drive side, apply suction to half of the plurality of suction openings (21).
32. Method according to Claim 28, characterized in that the action on each section of suction openings (21) is carried out by a suction pump, a suction fan or the like having a drive that can be controlled/regulated and is preferably individual.
33. Method according to Claim 30, characterized in that the action on each suction opening (21) is carried out by a suction pump, a suction fan or the like having a drive that can be controlled/regulated and is preferably individual.
34. Method according to one of Claims 19 to 33, characterized in that the suction pump, the suction fan or the like is operated with a suction volume that can be controlled/regulated in the range from 1 to 40 m³/h per m working width per m/min wire speed, preferably of 1.4 to 25 m³/h per metre working width per m/min wire speed.
35. Method according to one of Claims 30 to 34, characterized in that the suction pump, the suction fan or the like is operated with a suction velocity that can be controlled/regulated in the range from 10 to 25 m/s, preferably from 12 to 20 m/s.

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