SE439443B - PROCEDURE AND APPARATUS FOR TREATING A CURRENT MATERIAL COAT, EXTRA A METAL PLATE - Google Patents

Description

7901958-4 out the different liquid solutions used in the different containers. However, these rollers are cut, hollowed out or otherwise damaged by the metal sheet to the point where they become ineffective in preventing the running metal sheet from transferring liquid between the containers. Such plants also use carrier rollers located inside the containers to contact the running sheet metal and guide it through the liquid bath used in the treatment of the sheet metal. These support rollers can easily rotate more slowly than the associated linear speed at which the sheet metal moves over the rollers to cause slippage or slippage between the rollers and the sheet metal, with consequent damage to the surface of the sheet metal. Elimination of these rollers and rollers would be a great advantage in the treatment of sheet metal. Spreaders are usually used above and below the running sheet metal to direct liquid towards the adjacent flat surfaces of the sheet metal.

The liquid from these diffusers comes into contact with the metal plate at angles which form substantially 9Û ° with the plane of the running metal plate. It is clear that the use of such diffusers in connection with a horizontally running metal sheet generally entails an uneven treatment of the upper and lower surfaces of the running metal sheet. Thus, for example, a liquid which hits the upper side of the metal plate may form puddles or kisses of liquid which disturb the impact of the liquid coming from the subsequent diffuser.

The top of the metal sheet is generally subject to a bath or wetting or soaking. The opposite applies to the treatment of the treatment of the underside of the running metal sheet, where gravity entails an immediate removal of the liquid directed towards the underside through the diffusers located below the running metal sheet. The opposite sides of the metal sheet are thus subjected to different treatment conditions and thereby a uniform treatment of the opposite sides of the sheet metal is usually produced when the sheet is moved.

U.S. Patent No. 3,328,997 discloses the use of flotation type nozzles to direct a cleaning fluid toward a continuous web of material. The particular apparatus shown in the said patent uses in the liquid bath a number of carrier rollers, which, as already stated, can have a detrimental effect on the treatment of the metal in the bath. The present invention relates to an improved apparatus for treating a continuous web of material in a liquid bath.

According to the invention, there is provided an apparatus for use in treating a continuous web of material, and the same comprises at least one container with a horizontally elongated chamber with an opening at each end for the entry and exit of the web of material, and the characterizing device is that the chamber contains at least one upper and one lower row of nozzles, each of which is elongated in a direction perpendicular to the movement of the web of material and arranged so that in use the web of material can go between the rows, with each of the nozzles provided with an elongate slot, which faces the web of material and has a slot length substantially equal to the width of the web of material, and the nozzle is formed to direct a turbulent liquid flow from the slot to the web of material at an acute angle thereto and in a direction opposite to the direction of movement of the web.

A unique liquid seal in the form of a pair of opposing equal liquid nozzles is used at the inlet and outlet openings of the chamber in combination with air blowers to seal the openings to prevent the escape of liquid from the chamber into the chamber of an adjacent container, where such a liquid would exert a detrimental effect on the process carried out in this particular container.

Another aspect of the invention is the arrangement between adjacent nozzles in the chamber of a turbulator, which is simply a nozzle which directs a high pressure liquid jet directly towards the running metal plate at an angle of substantially 90 ° to collide with it. extremely turbulent liquid flow which the nozzles produce and thereby generate even stronger turbulence adjacent the surfaces of the running metal plate.

The successive liquid streams, when in contact with the metal sheet in an opposite direction at angles considerably less than 900, provide a unique scrubbing effect not normally provided by the spreaders in prior art devices, eliminating the need for auxiliary cleaning equipment, such as scrubbing brushes. and other similar trifles. The result is an improvement in the quality of the treatment in the case of the sheet metal and a consequent reduction in the time required to treat the sheet metal correctly.

The liquid seals and blowing devices eliminate the need for press rolls between adjacent treatment containers and effectively control the transfer of liquid between adjacent containers that normally occurs when the press rolls have been cut, hollowed out or otherwise so damaged that they cannot be repaired.

A consequent contamination or dilution of the liquid in the different treatment containers is reduced to a minimum and eliminates the need for frequent filling of the liquid and periodic draining fššè) fi jïk §2lSIxx 7901958-4. from the containers of spoiled or weakened liquid which may cause contamination of the sewage system where such liquid is emptied.

Furthermore, the need for guide rollers inside the containers is eliminated due to the liquid beds generated inside the containers for supporting the metal plate. Many of the problems which have arisen at previous installations have thus been eliminated or considerably reduced to a point where they are irrelevant.

In the following, the invention will be described with reference to the accompanying drawings. Fig. 1 is a longitudinal section of two cleaning units or containers which are trained in accordance with the invention and schematically shown arranged in tandem. Fig. 2 is a sectional view of one of the cleaning units seen from line 2-2 in Fig. 1, with certain control or guiding devices for the unit shown schematically. Fig. 3 is an enlarged sectional view of the device for sealing the openings through which a continuous web of material enters and exits the chamber in each of the units. Fig. 4 is a sectional view of a portion of the cleaning unit shown in Fig. 1 seen from line 4-4 of Fig. 2.

Figures 1, 2 and 4 show an apparatus 5 used for the treatment, for example cleaning of a running material web 6 in the form of a sheet 6 of metal, for example steel or aluminum. The apparatus 5 in this case comprises at least two adjacent containers 7, 8 in which the running metal plate 6 is washed resp. rinse. The metal plate 6 is removed from an ordinary unwinding device 9 and transported in a substantially horizontal path successively through the washing container 7 and the rinsing container 8, and from there the metal plate 6 is removed to an ordinary winding device 10, which is driven or set in rotation by a suitable drive mechanism M.

The containers 7 and 8 each have a horizontal, elongate and rectangularly shaped chamber 11, which is delimited by longitudinal side walls 12, 13, by opposite end walls 14, 15 and a bottom 16. The chambers 11 are arranged centrally in and separated from the outer surrounding the walls or jacket 17 of each of the containers 7, 8. The chambers 11 in adjacent containers 7, 8 * are separated from each other and arranged end to end or in tandem.

Reagents 18, 19 of the adjacent flotation type similar to elongate flotation-type treatment nozzles 20, 21 are located in each of the chambers 11 and positioned so that the running metal plate 6 passes between them, and the rows 18, 19 of nozzles 20, 21 in adjacent containers 7, 8 are likewise horizontally aligned 79Û1958 ~ 4 in line to maintain the running metal plate 6 in a substantially horizontal path through both containers 7, 8.

The treatment nozzles 20, 21 are, as best seen in Figures 1 and 2 and 4, parallel and perpendicular to the direction in which the metal plate 6 is moved and have at least the same extent as the side width W of the metal plate 6. The nozzles 20, 21 have the same construction and, as best As can be seen from Fig. 4, each comprises a closed compartment 22, an inlet 23, through which liquid enters the compartment 22, a screen 24 for uniform distribution of the liquid into a continuous slot 25, which is arranged in the surface or side of the nozzles 20, 21. 26 in the middle of the running metal plate 6, and a deflector 27 arranged adjacent the slot 25 to conduct a continuous turbulent liquid flow under pressure from the slot 25 at an angle to the running metal plate 6 in a direction upstream or opposite to the direction in which the metal plate 6 travels. past the nozzles 20, 21 with. Successive streams of cleaning or rinsing liquid under pressure are directed from the nozzles 20, 21 towards the running metal plate 6 at angles which are considerably less than 90 ° in relation to the plane of the running metal plate 6, namely at angles which are considerably less than 45 ° and preferably is in the range of 10 ° to 30 °. Sometimes a pair of opposing nozzles 28, 29 (Fig. 4) may be provided which are provided with two parallel continuous slots and deflectors for directing two angularly opposite and intersecting liquid streams towards the metal plate 6 to help stabilize the movement of the metal plate 6. in the horizontal path, but in most cases it is more desirable to direct the flows of liquid in the same directions towards the running metal plate 6 to form a particularly turbulent liquid flow adjacent to and parallel to the metal plate 6 in an upstream or countercurrent direction.

Additional agitation or turbulence for increased cleaning action can be provided by placing a turbulator 30 between each pair of adjacent treatment nozzles 20 or 21. A turbulator 30 is simply a standard simple high pressure, low volume outlet nozzle extending across the sheet metal 6 and constructed directing a jet of pressurized liquid directly and not at an angle to the running metal plate 6, namely at an angle which is substantially 90 DEG to the plane of the running metal plate 6. The liquid jets from the turbulators 30 break or collide with the continuous turbulent liquid stream from the treatment nozzles 20, 21 to generate even greater turbulence adjacent the running metal plate 6.

Additional cleaning effect can be achieved by using an abrasive cleaning material, for example quartz, sand or talc, in the cleaning liquid circulating through the treatment nozzles 20, 21 and the turbulators 30. The use of such abrasive cleaning readings which otherwise eliminates the need for scrubbing brushes normally used during the previous cleaning steps to remove rust and chips from a metal sheet 6, goh reduces the time usually required to properly treat the metal sheet 6. Due to the abrasive nature of such material, it is best to build the treatment nozzles. 20, 21, the turbulators 30 and any other nozzles through which the abrasive cleaning solution is made of a durable and abrasion resistant material which is compatible with the solution. Thus, ordinary steel nozzles can obtain lining of rubber, plastic or other material in question which is not affected by the abrasive action of the cleaning solution. The said nozzles can be composed of any - durable and liquid-resistant materials, in the case of, for example, highly corrosive chemicals, acids or harmful detergents used as a liquid in the treatment of the continuous material web.

The containers 7, 8 are filled with liquid to a level where the treatment nozzles 20, 21 and the turbulators 30 are preferably immersed in the liquid bath in each of the chambers 11, although in certain types of treatment of the metal plate 6 it is more advantageous to maintain the liquid level below the vertically lowest row 19 of the treatment nozzles 21. The treatment nozzles 20, 21 and the turbulators 30 are located close enough to the running metal plate 6 to provide a good scrubbing and cleaning of the metal even though they may be completely immersed in the liquid bath. The liquid streams from the treatment nozzles 20, 21 are used for a dual purpose, namely to provide a turbulent cutting effect of the liquid against the adjacent opposite upper and lower surfaces 31, 32 of the metal plate 6, and they form a liquid bed on which the metal plate 6 is supported as it passes through the treatment chambers 11 of the two containers 7, 8 the end walls 14, 15 of each of the chambers 11 are provided with horizontally and laterally elongate openings 33, 34 which lie horizontally in line and through which the running metal plate 6 enters and exits the chambers 11. A unique liquid seal 35, as best seen in Fig. 3, has been provided to seal each of the openings 33, 34 around the metal plate 6 to prevent the escape of liquid from the containers 7 and 8 through openings. ordinary flap seals 33, 34, ordinary flap seals are insufficient because the running metal plate 6, and in particular the uneven joined ends and edges of two overlapping metal plates, tear and finally destroy them, necessitating a complete shutdown of the process to replace the valve seals with new ones to prevent mass outflow of liquid from the containers 7, 8.

The liquid seals 35 each comprise a pair of parallel oppositely arranged elongate sealing nozzles 36, 37, which in terms of construction are similar to the treatment nozzles 20, 21 used for the washing and rinsing of the running metal plate 6. The sealing nozzles 36, 37 are likewise placed transversely to the running metal plate 6 and lie on opposite sides of the running metal plate 6 at the openings 33, 34. The sealing nozzles 36, 37 each have a longitudinal section 38 with an inlet 39 and a ordinary screen 40 for uniformly distributing pressure fluid from the compartment 38 through a continuous slot 41 located in the surface or side 42 of the nozzles 36, 37 facing the plate. A deflector 43 abuts next to each slot 41 to direct a continuous flow of pressure fluid at an angle to the running metal plate 6 in the chambers: 11 direction. The liquid stream from opposite pairs of sealing nozzles 36, 37 converges towards the running metal plate 6 in the direction of the chambers 11 to form adjacent and parallel to the surfaces 31, 32 of the running metal plate 6 flowing liquid into the chambers 11. The continuous liquid nozzle stream from the sealing nozzle 36 37 has sufficient mass and velocity to block the liquid attempting to escape from the chambers 11 through the openings 33, 34 and to form a liquid bed for supporting the running metal plate 6 adjacent the end walls 14, 15 of the chambers. The liquid seals 35 thus serve a twofold function. purpose and has been specially designed to prevent the transfer of liquid between adjacent treatment containers using different liquids which it is not desirable to mix.

A pair of conventional blowing nozzles 44, 45 are arranged outside and adjacent to each of the openings 33, 34 in the end walls 14, 15 in further separate communication from the chambers 11, and they direct, like the sealing nozzles 36, 37 of the liquid seals 35 during angle to the running metal plate 6, the angles being considerably less than 900 relative to the plane of the running metal plate 6 and going in the direction of the chambers 11 to help prevent the escape of liquid from the chambers 11 and to provide an air cushion for assist with the support of the running metal plate 6 next to the end walls 14, 15.

Any suitable fan can be used to circulate air through the blowing nozzles 44, 45. The liquid that is blown away from the running medium Q ßn 6 QEÜ Éßgšnqps updæä fëä fi ökê fi Git q fi away. as best shown in Fig. 1, by the action of gravity to a reserve or storage compartment 46 located in the lowest part of each of the containers 7, 8 and the trapped liquid can be recirculated to the treatment nozzles 20, 21, the sealing nozzles 36, 37 and the turbulators 30 through a conventional pump 47 (Fig. 2), and this can also be used to circulate new, unused liquid from a supply 48 to the compartment 46 or to the chambers 11 via the nozzles 20, 21, 36, 37 and the turbulators 30 until the treatment nozzles 20, 21 and the turbulators 30 have been submerged and the liquid flows over into the chambers 11 to the lower storage compartments 46. In this way, liquid used in the treatment of the metal plate 6 will continuously circulating between the treatment chambers 11 and the storage compartments 46. Drains 49, 50 are arranged in each of the chambers 11 and the lower compartments 46 to allow liquid to drain away from the containers 7, 8. Circulation of liquid between the chambers 11 and the storage compartments in each of the containers 7, 8 can also be maintained by adjusting the size of the drain 41 from the upper chamber 11 so that there is a constant flow of liquid between the chambers 11 and the storage compartments 46 when the drain 49 is left open.

The liquid seals 35 and the blowing nozzles 44, 45 effectively control the undesirable circulation of liquid between the containers 7, 8 and eliminate the need for ordinary press rolls, which are usually used when ordinary flap seals are used to seal the inlet and outlet openings of the containers 7, 8. . In some cases it may be desirable to provide additional blowing devices, since the blowing nozzles 44, 45 are designed to indicate a comparatively small volume of air with a comparatively high pressure. If so, a pair of flotation-type nozzles 51, 52 may be placed between each of the fluid seals 35 and the adjacent high pressure blow nozzles 44, 45. The flotation type nozzles 51, 52 are designed to deliver a comparatively large volume of air with a comparatively low pressure and, as best seen in Fig. 3, to be formed in the same structure as the liquid sealing nozzles 36, 37 of the liquid seals.

The use of flotation type nozzles 51, 52 in combination with the high pressure blowing nozzles 44, 45 provides significant energy savings due to the fact that the majority of any liquid passing through the liquid seals 35 can be removed from the metal plate 6 by the larger air mass flowing. out of the low pressure and high volume formed flotation type nozzles 51, 52, since the latter require less energy to operate continuously than the high pressure and low volume formed blowing nozzles 44, 45.

Due to their efficiency, the liquid seals 35 alone or in combination with the blowing nozzles 44, 45 and / or the flotation air nozzles 51, 52 can also be used instead of the press rollers in ordinary treatment containers based on the use of ordinary nozzles 7901958-4 or flowing nozzles. for applying liquid to a continuous material web. A plurality of flattening nozzles 53 with one or two continuous slits or with slits spaced between them and with rectangular or eyelid-shaped deflection means can be arranged between adjacent containers 7, 8 to produce an air cushion or other relevant fluid bed for the running metal plate. 6 between the containers 7, 8 if these are at a more considerable distance from each other.

It is clear that other containers or units, for example a drying device, can be located in tandem with the rinsing container 8, and similar flotation nozzles can be used therein to heat and dry the running metal plate 6. In addition, other similar containers or units can be used to successively apply , bake and cool a liquid coating on the running metal plate 6 after it has been properly cleaned and prepared to receive such subsequent treatment before winding on the winding device 10.

Thus, an apparatus has been described here which lacks rollers or rollers and produces successive pressurized fluid flows which touch a continuous web of material at comparatively small angles in relation to the plane of the web and in a direction opposite to that in which the web moves. especially useful for cleaning sheet metal before it is provided with a coating of a protective layer, for example paint. The special flotation nozzles used in the successive containers not only act to support the running metal sheet on a bed of the liquid used to treat the sheet metal but also direct this liquid towards the running sheet metal in such a way that it a thorough scrubbing of the adjacent surfaces of the metal sheet is achieved. It is clear that the cleaning effect is essentially the same on both sides of the running metal sheet, especially when the treatment nozzles are submerged (soaked) in order to achieve a more uniform treatment of the surfaces as a result.

YQOR QUAHT

Claims (3)

1. 7901958-4 10 P a t e n t k r a v 1. Procedure for processing an open material web (6), e.g. a metal surface, characterized by the following steps: advancing the material web (6) through a chamber (11) along a substantially horizontal web without any contact with any rollers or shafts in the chamber, the material web (6) being inserted into and out of, respectively. the chamber through openings (33, 34) in end walls (14, 15) of the chamber (11), insertion into contact with opposite planar surfaces on the opening material web (6) in the chamber (11) between the inlet and outlet openings (33, 34) of successive turbulent streams of liquid under a pressure under pressure (18, 19) for cleaning the opening web of material, the web of material being carried on a bed of liquid formed by said liquid streams, and the liquid streams being introduced at smaller angles. than 90 ° in relation to the plane of the web of material and in directions upstream of and opposite to the direction of travel of the web of material, and to provide a liquid seal (35) with respect to the opposite surface of the web of material (6) or the inlet and outlet openings (33, 34) by introducing sealant turbulent streams (36, 37) of a liquid under pressure, the liquid flow at the inlet opening (33) being directed with the direction of travel of the material web and at the outlet opening (34) towards the direction of travel of the material web (6) and at angles substantially less than 90 °, thereby preventing the passage of liquid from the chamber (11) through the inlet and outlet openings. Method according to claim 1, characterized in that a stream of compressed air (44, 45) is injected against the opposite surface surfaces of the material web (6) outside the chamber (11) and outside the inlet and outlet openings (33, 34) in the end walls (14). , 15). wherein the compressed air currents at the two ends converge towards the running web of material at angles which are considerably less than 90 ° in relation to the web of material, and wherein the compressed air flow at the inlet opening is directed with and at the outlet opening the direction of feed. 3. A method according to claim 1 or 2, characterized in that the opposite flat surfaces of the opening material web (6) are directly affected by jets (30) of liquid under pressure arranged between the said in a row (18, 19) arranged one after the other the liquid streams (20, 21) and at angles which are substantially 90 ° relative to the plane of the web of material. 4. A method according to claim 1, 2 or 3, characterized in that the opposite flat surfaces of the opening web of material are touched by a liquid containing abrasive material to assist in the cleaning of the web of material. 5. A method according to claim 3 or 4, characterized in that the web of material is successively moved through at least two separate, horizontal chambers (7, 8), which lie end to end at some distance from each other, and along a substantially horizontal path between these chambers, and consisting of two horizontally aligned rows (54) of treatment nozzles, the web of material being advanced without contact with any vases or rollers. Apparatus for carrying out the method according to any one of the preceding claims, consisting of at least one container (7, 8) with a horizontal elongate chamber (11) with an opening (33, 34) at each end for feeding and discharging the material web (6). , and wherein the chamber contains at least one upper (18) and a lower (19) row of nozzles (20, 21), each of which is elongate and opens perpendicular to the direction of travel of the web of material (6), and where the rows (18, 19) of nozzles are arranged so that the web of material (6) can pass between the rows, characterized in that each nozzle (20, 21) has an elongated seat (25) which is directed towards the web of material (6) and is substantially as wide as the web of material , and in that each nozzle (20, 21) is connected to means for introducing liquid under pressure against the opposite planar surfaces of the material web and is directed at an acute angle to the surface of the material web in a direction opposite to the direction of travel of the material web, and a The apparatus adjacent each and one of the end openings (33, 34) is formed with a liquid seal (35) to prevent the escape of liquid from the chamber (11) and consisting of a pair of opposite sealing nozzles (36, 37) between which the web of material (6) can pass, and where the sealing nozzles (36, 37) have slits (41) and deflection means (43) arranged to direct converging streams of liquid under pressure towards the flat surfaces of the material web at angles substantially less than 90 "relative to the material web. plane and at the feed opening (33) in the direction of and at the feed opening (34) in the direction of the direction of travel of the material web. Apparatus according to claim 6, characterized in that a pair of blow nozzles (44, 45) are arranged next to each of the liquid seals (35) and outside them, wherein the web of material (6) can pass between the blow nozzles, and wherein each pair of The blowing nozzles are designed to direct converging compressed air currents at an angle to the continuous web of material at angles considerably less than 90 ° relative to the plane of the web of material and in the direction of the adjacent seal and chamber, the blowing nozzles during operation serving to prevent liquid from escaping the container and to assist in supporting the continuous web of material adjacent the end walls of the chamber (14, 15). Apparatus according to claim 7, characterized in that it includes a storage compartment (46) located vertically below the chamber (II) and that means are provided for delivering to the storage compartment liquid removed from the running material web by air from the blowing nozzles ( 44, 45). Apparatus according to claim 7, characterized in that it includes means (49, 50) cooperating with the chamber (II) to remove to the storage compartment liquid flowing into the chamber. Apparatus according to claim 9, characterized in that the liquid flows are directed towards the running material web at angles in relation to the plane of the material web which is less than 45 °. ll. Apparatus according to claim 10, characterized in that liquid in the chamber is maintained at such a level that the treatment nozzles (20, 2l) are immersed in the liquid. Apparatus according to any one of claims 6-11, characterized in that it includes at least one turbulator (30) located between two adjacent nozzles in each row (18, 19) of treatment nozzles (20, 21) and constructed directing a jet of pressure fluid towards the running material web at a substantially right angle, on the other hand, to break the turbulent liquid flow along the running material web caused by the nozzles of the upper and lower rows (20, 21). Apparatus according to any one of claims 6-12, characterized in that at least a majority of the nozzles (20, 21) in the rows (18, 19) have a longitudinal section (22) with an entrance (23) formed therein. ), partly a single continuous slot (formed in the surface of the nozzle facing the running web of material, with the slot in connection with the compartment and with at least the same extent as the width of the web of material measured across the direction of movement of the web of material, and a deflection means ( 27) adjacent to the slot for directing a continuous flow of pressurized liquid from the slot at an angle to the running web of material, with the angle considerably less than 900 relative to the plane of the web of material 14. Apparatus according to any one of claims 6-13, characterized in that it includes at least two adjacent containers (7, 8), one located downstream of the other relative to the web of material, and one constituting a washing container ( 7) and the other a rinsing container (8) and with each provided with rows (18, 19) treatment nozzles (20, 21), and on the other hand means (47) for circulating liquid used in the treatment of the running material web into the nozzles and uniformly out from the slots arranged therein in the direction of the running material web. Apparatus according to any one of claims 6-14, characterized by means (51, 52) for stabilizing the movement of the web of material as it passes through the chambers (11), said means including at least a pair of opposing nozzles each provided with on the one hand a pair of parallel continuous slots (41) running in the longitudinal direction and on the other hand a pair of deflection means (43) adjacent to the slots and converging in the direction of the running material web. Apparatus according to claim 14e11er 15 insofar as these depend on claim 8, characterized in that each of the liquid seals includes on the one hand a pair of sealing nozzles (36, 37) adjacent to each of the openings and located between the running and the material web,: con aiïäi 79o19ssa4 14 as it passes through the opening, with the pair of sealing nozzles having the same extent, when passing through the opening, with the pair of sealing nozzles having the same extent as the opening and with facing sides in which continuous slots (41) are arranged in the longitudinal direction of the sealing nozzle and to the same extent as an adjacent opening, and on the one hand a pair of deflection means (43) adjacent the slots in each pair of sealing nozzles and converging in the direction of the running material web and the chambers for directing continuous pressure fluid flows angle to the continuous web of material and to liquid seeking to escape at angles considerably less than the island 9 0 ° in relation to the plane of the material web. Apparatus according to any one of claims 6-16, characterized in that it includes means for maintaining the liquid in the chambers at such a level that the treatment nozzles are immersed. Apparatus according to any one of claims 6-17, characterized by that there is abrasive material in the liquid used to treat the running web. '} §_ Apparatus according to claim 18, characterized in that the abrasive material consists of one or more of quartz, sand or talc. Apparatus according to any one of claims 5-19, characterized in that the treatment nozzles (20, 21) are lined with elastomeric and abrasion resistant material which is compatible with the abrasive material to protect said nozzles from the abrasive action of the material. Apparatus according to claim 6 or any claim dependent thereon, characterized in that it includes a flotation nozzle (51, 52) located between each liquid seal and blowing nozzle for directing a flow of compressed air at an angle to the running material web at an angle considerably less than 900 ° C. in relation to the plane of the material web, with the flotation nozzles constituting nozzles for high volume and low pressure in relation to the blowing nozzles (44, 45), which consist of nozzles for low volume and high pressure, with each flotation nozzle including a closed compartment with an inlet and an elongate slot facing the running material web, partly screens in the compartment for directing a uniform air flow from the slot, and partly a deflection means adjacent the slot for directing the air flow at an angle to the running material web in the direction of the chamber.