WO2012120200A1

WO2012120200A1 - Runnability component and method for improving efficiency of a runnability component of a paper machine

Info

Publication number: WO2012120200A1
Application number: PCT/FI2012/050227
Authority: WO
Inventors: Pekka Saarikivi; Jarkko Nurmi
Original assignee: Metso Paper, Inc.
Priority date: 2011-03-08
Filing date: 2012-03-08
Publication date: 2012-09-13
Also published as: FI20115233A; FI124504B; FI20115233L; DE212012000070U1; FI20115233A0

Abstract

The invention relates to a structural element (1), which is adaptable into a runnability component (2) of a drying section of a paper machine or the like, preferably as retrofitting. The structural element comprises an elongated frame part, a compressed air nozzle (4) arranged in connection with the elongated frame part, and attachment means for attaching the frame part to the runnability component. The runnability component comprises an elongated box- like frame structure, the volume of which is limited by a first and a second side, and upper and lower sides connecting them, and a sealing member ( 3 ) arranged on the first side of the frame structure, i.e. on the entry side of the runnability component. The structural element is arranged on the first side of the frame structure of the runnability component, beneath the sealing member. The invention also relates to a method for improving the efficiency of a runnability component of a paper machine or the like.

Description

RUNNABILITY COMPONENT AND METHOD FOR IMPROVING EFFICIENCY OF A RUNNABILITY COMPONENT OF A PAPER MACHINE

The invention relates to a runnability component and a method for improving the efficiency of a runnability component according to the preambles of the independent claims presented below.

In a typical drying section of a paper or board machine the paper web to be dried is conveyed supported by one or two wires via hot drying cylinders. A drawback is that the web has a tendency to detach from the contact of the drying wire, causing runnability problems. Especially problematic points are so-called opening nips, i.e. points where the web and the wire disengage from the drying cylinder. Up to that point, the web has travelled between the wire and the drying cylinder, and when the wire detaches from the cylinder, the web tends to follow the cylinder surface and thereby to; disengage from the wire. Other problem points are so-called closing nips, where the web and the wire are brought into contact with the cylinder surface. At that point, the web tends to disengage from the wire due to an overpressure forming in the nip. The disengagement of the paper web from the wire easily leads to web breaks or to the formation of bags or folds in the web. The disengagement of the web from the wire generally leads to runnability problems, which are further emphasised when the speed of the paper machine increases. It is known to use different runnability components, such as blow or suction boxes, for improving the runnability of a paper machine. The runnability component often comprises a blow nozzle, producing air blows which are used to create an underpressure zone in a desired location of the so-called pocket space for keeping the web in contact with the wire. In the drying section the underpressure of the pocket space limited by two subsequent drying cylinders and a turn roll can be controlled for example with a blow nozzle on the exit side in addition to the blow nozzle on the entry side of the runnability component. Nozzles are used to eject air away from the pocket space and to prevent air from entering into the pocket space.

Whether a blow or a suction box is used as the runnability component, creating an underpressure with the aid of the runnability component usually consumes a large amount of energy, which may be economically disadvantageous. One problem is also to get the underpressure zone to be sufficiently sealed off from the space remaining outside the underpressure zone. If the formed underpressure zone is not sufficiently sealed off, for example the blow effect of the runnability component must be increased to achieve the necessary underpressure, which further increases the energy consumption and thereto related costs of the runnability component.

When renewing the drying section of a paper machine it is of interest to improve the operation and energy efficiency of already existing runnability components, however without replacing them with new runnability components. If the already existing operational runnability components are replaced with new, more efficient runnability components, the necessary investment costs can be significant. There is thus a clear need for improving the operation of already existing runnability components in a simple and cost efficient manner.

The main object of the present invention is to reduce or even to eliminate the above-described problems appearing in the prior art. An object of the present invention is to improve the operational efficiency of already existing runnability components in an easy and simple manner.

An object of the invention is to provide a cost efficient manner of extending the working life of runnability components of a drying section of a paper machine or the like.

Another object of the invention is to save energy by improving the energy efficiency of existing runnability components. In order to realise the above-mentioned objects, among others, the invention is characterised by what is presented in the characterising parts of the enclosed independent claims.

The embodiments presented in this text and their advantages relate, when applicable, to both the arrangements and methods according to the invention, even if this is not always separately mentioned. A typical structural element according to the invention, which is adaptable into a runnability component of a drying section of a paper machine or the like, preferably as retrofit, comprises

- an elongated frame part,

- a compressed air nozzle arranged in connection with the elongated frame part, - attachment means for attaching the frame part to the runnability component.

A typical runnability component according to the invention for supporting the travel of a web in the drying section of a paper machine or the like comprises

- an elongated box-like frame structure, the volume of which is limited by a first and a second side, and upper and lower sides connecting them,

- a sealing member arranged on the first side of the frame structure, i.e. on the entry side of the runnability component, and

a structural element according to the invention arranged on the first side of the frame structure, beneath the sealing member.

In a typical method according to the invention for improving the efficiency of a runnability component of a paper machine or the like, a structural element according to the invention is retrofitted to an existing runnability component, which comprises an elongated box-like frame structure, the volume of which is limited by a first and a second side, and upper and lower sides connecting them, and a sealing member arranged on the first side of the frame structure, i.e. on the entry side of the runnability component. Now it has surprisingly been found that the operational efficiency of already existing runnability components may be significantly improved by installing a structural element on the entry side of the runnability component, which structural element comprises a compressed air nozzle. Even by using a relatively small amount of compressed air it is possible to intensify the created underpressure, and simultaneously improve the operation of the runnability component. A separate structural element is easy to connect or install in different existing runnability components, the operation efficiency of which may no longer be otherwise improved, or in which an increase in the amount of blown air with the existing blow nozzles would lead to energy-economically disadvantageous solutions. One major advantage of the invention is that in a paper machine or the like the effect of already existing runnability components, such as blow boxes, may be increased with relatively small structural alterations performed as retrofit. Energy may also be saved with the aid of the invention in comparison to the previous situation. The invention is especially suitable for paper machines and the like with single-wire draw.

In one preferred embodiment of the invention the structural element is arranged to the runnability component as retrofit.

The length of the frame part of the structural element may be 0.3-12 m. In case the structural element is arranged in the runnability component only on the edge area of the paper web to be dried, the length of the structural part may typically be 0.45-1.0 m, more typically 0.5-0.75 m. The frame part of the structural element preferably extends over the whole paper web or the like, from the first side or web edge to its second side or edge, i.e. from the first end of the runnability component to the second end. The total length of the structural element may thus typically be 6-12 m, more typically 7-11 m, most typically 8-10 m. The frame part of the structural element is typically manufactured from aluminium or steel, and it may naturally be manufactured from several shorter parts, which are joined together in order to obtain the necessary total length of the frame part. A compressed air nozzle may be arranged in connection with the frame part of the structural element so that the frame part forms a separate piece, to which the compressed air nozzle is attached for example by welding or with mechanical attachment means, such as bolts, rivets or the like. The frame part may also be an inseparable part of the compressed air nozzle itself, whereby it may for example form a feeding chamber of the compressed air nozzle. The frame part of the structural element and the compressed air nozzle preferably are of the same length. The structural element also comprises attachment means for attaching the frame part to the runnability component. The attachment means of the structural element preferably allow movement of the structural element in relation to the frame structure of the runnability component, i.e. turning of the structural element in relation to the longitudinal axis of the frame part of the structural element. The attachment means may be mechanical attachment means, such as bolts, sliders or the like, which may be arranged to move in grooves, slots or the like in the frame structure of the runnability component. In one embodiment the frame structure of the runnability component is thus provided with movement openings, such as grooves or slots, and the structural element comprises mechanical attachment means, such as bolts, sliders or the like, which are arranged in the movement openings, in order to attach the frame part of the structural element in a movable manner to the frame structure of the runnability component.

Compressed air may be fed into the compressed air nozzle arranged in the frame part of the structural element, the pressure of which compressed air may be adjusted in the range of 1-6 bar, preferably 2-4 bar. The compressed air nozzle may be connected for example to a compressed air system in a paper mill. The compressed air nozzle arranged in the structural element may be a slot nozzle or it may comprise a row of nozzle openings. The width of the nozzle gap of the slot nozzle is typically 0.05-0.5 mm, preferably 0.07-0.2 mm. In case the compressed air nozzle comprises a row of nozzle openings, the diameter of an individual nozzle opening may be 1-5 mm, preferably 2-3 mm. The distance between adjacent nozzle openings may be 10-60 mm, preferably 20-40 mm. The nozzle openings may have a round or oval shape. For example, in one embodiment the compressed air nozzle, arranged in the structural element, comprises several round nozzle openings arranged in a row, the diameter of which is 1.5-3.5 mm and which are located at intervals of 20-40 mm from each other. As an example it may be stated that the structural element may comprise nozzle openings, the diameter of which is 1.5-2.5 mm, and the distance between which is about 25-35 mm, over an area, which extends 550-600 mm from both edges of the structural element, which has the width of the whole web, toward the middle part of the web. Thus an estimated consumption of compressed air of the structural element would be about 70 l/s (NTP) for both edges.

According to one embodiment of the invention the structure of the compressed air nozzle of the structural element may vary in the longitudinal direction of the structural element, i.e. in the distance between its first end and second end. For example the size of and/or distance between the nozzle openings of the compressed air nozzle may vary in the longitudinal direction of the structural element, whereby a desired optimal blowing profile of compressed air is obtained in the cross direction of the paper machine. The compressed air nozzle may also comprise a nozzle gap formed of several subsequent individual slot nozzles. The widths of the nozzle gaps of the individual successive slot nozzles may differ from each other. Normally the amount of compressed air blown is smaller in the middle area of the structural element, i.e. there are more and/or larger nozzle openings or nozzle gaps on the edges of the structural element. According to one embodiment of the invention the width of the nozzle gap of the slot nozzle or the diameter of the nozzle holes of the compressed air nozzle is thus larger on the first and/or second edge area of the structural element than in the middle part of the structural element. Typically the amount of compressed air blown is larger on the edge area, which extends at the most 25 %, preferably at the most 20 %, more preferably at the most 15 % from the first and/or second end of the runnability component toward its middle part, calculated from the total width of the paper machine. On this part of the runnability component the structural element may thus be equipped with nozzle openings or nozzle gaps, the diameter or width of which is larger than the diameter or width of the corresponding nozzle openings or gaps in the middle area of the structural element. On the edge area of the structural element the distance between the nozzle openings may also be smaller than in the middle area of the structural element, regardless of the size of the nozzle openings. According to one embodiment the compressed air nozzle of the structural element is arranged to extend 5-20 %, preferably 5-10 %, more preferably 5 % from the first and/or second edge of the runnabiiity component toward the opposite edge of the runnabiiity component, preferably to extend from the first edge of the runnabiiity component to the second edge, over the whole length of the runnabiiity component.

According to one embodiment of the invention the structural element comprises a mechanical sealing element in addition to the compressed air nozzle. The sealing element is preferably arranged to the structural element in the vicinity of the compressed air nozzle, beneath it, whereby the sealing element prevents an airflow on the entry side of the runnabiiity component back into the space between the runnabiiity component and the turn roll. The mechanical sealing element may be for example an elongated sealing strip. According to one embodiment of the invention the mechanical sealing element may also be divided into parts in the longitudinal direction of the structural element. In that case the mechanical sealing element in the structural element may be assembled in the longitudinal direction of structural element from several separate individual sealing element parts, the length of which is shorter than the length of the finished sealing element. The separate individual sealing element parts may also have properties differing from each other, whereby the sealing properties of the sealing element may vary in the longitudinal direction of the structural element, i.e. in the cross direction of the paper machine, i.e. in the longitudinal direction of the pocket space. For example by using sealing element parts made of different materials for obtaining the sealing element, it is possible to carefully control the pressure conditions of the underpressure zone also in the cross direction of the paper machine. The sealing element parts may differ from each other also with regards to their shape and design. The sealing element may thus be formed of several adjacent separate sealing element parts in the longitudinal direction of the structural element, which parts are attached to each other one after the other in order to obtain an elongated sealing element, and which sealing element parts may differ from each other by their design and/or materials. The sealing element or its separate sealing element parts may be manufactured for example from Teflon^®, plastic, rubber, composite or metal, such as steel or aluminium. This makes it possible to divide the structural element into different segments, such as for example a tail threading segment, in which segments the sealing conditions differ from the conditions in adjacent segments. According to one embodiment of the invention the sealing element arranged in the structural element is a labyrinth sealing. The sealing element preferably comprises an at least one-chambered labyrinth sealing, preferably a multi-chambered labyrinth sealing. The used labyrinth sealing typically has two, three, four or five chambers.

The sealing element of the structural element may be arranged to extend 5-30 % from the first and/or second edge of the structural element toward the opposite edge of the structural element, preferably to extend from the first edge of the structural element to the second edge, over the whole length of the structural element, especially when the structural element extends from the first end of the runnability component to the second end.

A runnability component in this application means a device or an arrangement, by means of which the travel of a web in a paper machine and especially in its drying section is stabilised. The runnability component is typically for example a blow box. The runnability component typically comprises an elongated box-like frame structure, which extends in the cross direction of the paper machine or the like substantially over the whole length of the paper web or the like. The first end of the runnability component is typically located at the first edge of the paper web, or close to the first edge, and the second end of the runnability component is located at the second edge of the paper web, or close to the second edge. Typically the runnability component is arranged in the drying section into the pocket space, which is limited by a wire running from the first drying cylinder to the second drying cylinder via a turn element. The turn element arranged on the wire run may be a turn cylinder, a turn roll, a suction roll or the like. The runnability component is arranged in the pocket space for ejecting air from said pocket space and for generating an underpressure zone in at least part of this pocket space. The pocket space here thus means the space in the drying section of the paper machine limited by the rolls, cylinders or the like and the wire conveyed on them, in which space it is desired to generate a pressure, which is lower than in the surroundings of the pocket space. The pocket space is typically limited by two successive or adjacent drying cylinders and a turn element of a wire placed between them and a wire travelling via them.

The entry side of the runnability component in this application means that part or surface of the runnability component, preferably the half, which is on the side of the first drying cylinder in the longitudinal direction of the paper machine or the like. Respectively, the exit side of the runnability component means that part or surface of the box-like runnability component, preferably the half, which is on the side of the second drying cylinder in the longitudinal direction of the paper machine or the like. A sealing member, usually a blow member, preferably a flexible blow nozzle, has been arranged on the first side, i.e. on the entry side, of the frame structure of the runnability component. The purpose of the blow member is to eject air away from the underpressure zone and/or to resist air entering there. The Coanda-effect may be used for forming and directing the air flow in a manner known as such. From the blow nozzle the air flow is directed to a curved sealing surface, where the air flow travels along said surface.

The blow member, such as the blow nozzle, is used to blow air at a blow speed of 30-90 m/s, preferably 50-70 m/s, even more preferably 40-60 m/s. The blow member of the runnability component is typically a high pressure nozzle.

In one embodiment the runnability component may comprise both a first and a second blow nozzle, whereby for example in the pocket space formed by two drying cylinders and a turn element the first blow nozzle may be arranged in the frame structure of the runnability component at the opening nip of the drying cylinder on the so-called entry side, and the second blow nozzle may be arranged at the closing nip of the drying cylinder on the so-called exit side. The first blow nozzle is thus typically arranged to blow air substantially against the travel direction of the wire, and the second blow nozzle is arranged to blow air substantially in the travel direction of the wire. Thus a situation is provided, where both blows are directed out of the pocket space. In one embodiment of the invention the structural element is retrofitted beneath and in the immediate vicinity of a sealing member, such as a blow member, such as a blow nozzle, located on the first side, i.e. the entry side, of the runnability component. The structural element is preferably arranged in the frame structure of the runnability component so that the blow of the compressed air nozzle/nozzles of the structural element is directed into a passage between the sealing member and the drying wire, i.e. into the area between them, preferably diagonally toward the wire or toward the sealing surface of the blow member of the runnability component, for example the Coanda surface of the blow member. The structural element is typically arranged to extend 5-30 % from the first and/or second edge of the frame structure of the runnability component toward the opposite edge of the frame structure, preferably to extend from the first edge of the frame structure to its second edge, over the whole length of the frame structure.

According to one embodiment of the invention the structural element may be arranged to be turnable around the longitudinal axis of the frame structure of the runnability component, i.e. around its own longitudinal axis. The structural element is thus retrofitted to the runnability component so that it is turnable around the longitudinal axis of the frame structure of the runnability component. Turn members may be arranged in either end or both ends of the structural element, with the aid of which turn members the structural element may be moved around the longitudinal axis of its frame part. By moving the structural element by turning it is possible to adjust the direction and distance of the compressed air blow from the web. In one embodiment of the invention at least one mechanical lower sealing element is arranged on the lower side of the frame structure of the runnability component. In other words, a lower sealing element is arranged in the lower part of the runnability component, in a gap between the runnability component and the turn roll, in order to seal said gap and thereby to make the operation of the turn roll more efficient. The lower sealing element may be arranged in the lower part of the runnability component to a desired location, either on the part on the entry side of the runnability component, or on the part of the exit side. There may also be more than one, for example two or three, sometimes even four or five lower sealing elements on the lower side of the runnability component in connection with the gap between the runnability component and the turn roll, whereby the sealing elements may be arranged for example successively in the machine direction and/or graded with respect to their sealing effect and/or different in their dimensions or material. The lower sealing element may to its material and structure be similar to the sealing element arranged in the structural element described earlier in this application.

The lower sealing element may preferably be arranged in the lower part of the runnability component on the entry side of the runnability component or in the middle part of its lower part. Thus an efficient underpressure zone may be better maintained on the side of the closing nip of the turn roll and the adhesion of the web to the wire may be guaranteed. The creation of a sufficient underpressure in the area between and limited by the structural element and the lower sealing element does thus also not require powerful blows, which improves the energy efficiency of the runnability component.

When the lower sealing element is arranged in the lower part of the runnability component, on the exit side of the runnability component, the operation of the turn roll may be made significantly more effective, because due to the lower sealing element the air is after the opening nip of the turn roll directed essentially in the direction of the web away from the pocket space, instead of being directed between the runnability component and the turn roll. At the same time, the flow directed in the direction of the web ejects with it air away from the pocket space, which creates an underpressure also in the gap between the runnability component and the second drying cylinder, and therefore keeps the web attached to the wire. In practice the suction from the turn roll, needed for providing the underpressure, may be decreased, which naturally decreases the energy consumption of the suction members, or the same energy consumption provides a significantly greater suction effect. The air ejection effect provided by the lower sealing element is emphasised as the running speed of the drying section increases.

The lower side of the runnability component here means that part or surface of the runnability component, which is closest to the turn roll, and which lower part comprises a lower surface arranged substantially towards the turn roll. In case a lower sealing element is arranged on the lower side of the runnability component, a possible blow member on the second side, i.e. exit side, of the runnability component may in one embodiment of the invention be completely removed from operation.

In one embodiment of the invention the distance of the lower sealing element from the turn roll is adjustable. Thus, the underpressure in the underpressure zone may be adjusted to be suitable for the running situation. Sometimes it has additionally been observed that the lower sealing element arranged on the lower side of the runnability component provides such an efficient sealing that the underpressure in the underpressure zone rises considerably high. Thus the position of the lower sealing element may be adjusted to be further from the turn roll, whereby the gap between the lower sealing element and the turn roll grows, and air is leaked through the gap into the underpressure zone from the opening nip on the exit side.

In this application a paper machine or the like means for example a paper machine or a board machine. The cross direction of the paper machine or the like means the direction, which is transverse to the main travel direction of the web and wire. The main travel direction of the web and wire is called the machine direction. The wire means a planar fabric generally manufactured from plastic or metal, which is conventional in paper machines or the like, supported by which fabric the paper web is conveyed in the paper machine or the like.

Typically in a paper machine or the like, the ends of the pocket spaces are sealed, for example with end plates according to prior art, such as gap plates. The end plates are arranged in a vertical plane according to machine direction, on both sides on the edges of the machine, and the drying cylinders, the turn roll, the wire and the web are limited in the space between them. The invention is described in more detail below with reference to the enclosed schematic drawing, in which

Figure 1 shows a structural element according to one embodiment of the invention seen from the side, and

Figure 2 shows a structural element according to one embodiment of the invention in connection with a runnability component.

Figure 1 shows a structural element according to one embodiment of the invention. The structural element 1 is arranged on the first side 2' of a frame structure of a runnability component 2. The runnability component 2 also comprises a blow member functioning as a sealing member 3, which in Figure 1 is shown only schematically. For example the blow gaps or blow streams of the blow member functioning as a sealing member 3 are not shown at all in the figures. The structural element 1 comprises a compressed air nozzle 4, the compressed air blow coming from which is illustrated with an arrow A. The compressed air nozzle 4 is formed from a compressed air pipe 6, wherein a blow gap 10 has been arranged, through which the compressed air is led out from the inner part 1 of the compressed air pipe 6. The blow of compressed air A is directed into the area B between the sealing member 3 of the runnability component 2 and the drying wire 9, i.e. into a passage between the blow member 3 and the drying wire 9. The blow of compressed air A is preferably directed diagonally toward the drying wire 9 or toward the sealing member 3 of the runnability component 2. The structural element 1 is also equipped with a mechanical sealing element 5, which is attached to the compressed air nozzle 4, on the side of the compressed air pipe 6. The sealing element 5 comprises a sealing support 8, by means of which the sealing element 5 is attached to the compressed air pipe 6, and a sealing element part 12, preferably a labyrinth sealing, even more preferably a multi-chambered labyrinth sealing. The structural element 1 may be turned by means of a control mechanism or a turn member 7, whereby the compressed air pipe 6 of the compressed air nozzle 4 of the structural part 1 is turned around its longitudinal axis. Thus the direction of the blow A of the compressed air nozzle 4 and the distance of the sealing element part 12 of the sealing element 5 from the drying wire 9 may be altered.

Figure 2 shows a structural element according to one embodiment of the invention in connection with a runnability component. The runnability component 2 is arranged into a pocket space limited by two drying cylinders 21 , 22 and one turn suction roll 23. A blow nozzle, i.e. a sealing member 3, is arranged on the entry side 2' of the frame structure of the runnability component 2, the air jet from which nozzle is directed against the travel direction of the web 24, preferably out from a narrow gap or a row of holes. The flow follows a shaped extension and rises upwards in the direction of the curved surface against the incoming direction of the web.

The structural element 1 corresponds to the structural element shown in Figure 1 with regards to its characteristics and its operation. It is arranged on the entry side of the runnability component 2, on the side 2' of the frame structure. The structural element 1 is arranged beneath the blow nozzle functioning as a sealing member 3 of the runnability component 2, in its immediate vicinity. A lower sealing element 26, such as a sealing strip, is arranged in the lower part 25 of the runnability component 2, in this case the blow box. A first underpressure zone 91 is thus formed in the pocket space, which first underpressure zone is limited by the structural element 1 , the web 24 draw between the entry side drying cylinder 21 and the turn suction roll 23, the upper surface of the turn suction roll, the lower sealing element 26 and the lower part 25 of the blow box and the entry side 2', as well as by the gap plates in the ends of the pocket space.

The invention is not meant to be limited to the embodiments shown as examples above, but the aim is to interpret it extensively within the scope of protection defined by the claims presented hereafter.

Claims

1. A runnability component for supporting a travel of a web in a drying part of a paper machine or the like, which runnability component comprises

- a sealing member arranged on the first side of the frame structure, i.e. on the entry side of the runnability component,

characterised in that

a structural element is arranged on a first side of the frame structure of the runnability component, beneath the sealing member, which structural element comprises

- an elongated frame part,

2. Runnability component according to claim 1 , characterised in that the structural element is arranged to extend 5-30 % from a first and/or second edge of the frame structure toward the opposite edge of the frame structure, preferably to extend from the first edge of the frame structure to its second edge, over the whole length of the frame structure.

3. Runnability component according to claim 1 or 2, characterised in that the sealing member arranged on the first side of the frame structure of the runnability component is a blow member, preferably a flexible blow nozzle.

4. Runnability component according to any of the claims 1-3, characterised in that the compressed air nozzle of the structural element is arranged to extend 5- 20 %, preferably 5-10 %, more preferably 5 % from the first and/or second edge of the runnability component toward the opposite edge of the runnability component, preferably to extend from the first edge of the runnability component to the second edge, over the whole length of the runnability component.

5. Runnability component according to claim 1 , characterised in that the structural element is arranged in the runnability component as a retrofit.

6. Runnability component according to claim 1 , characterised in that the structural element is arranged to turn around the longitudinal axis of the frame structure of the runnability component.

7. Runnability component according to claim 6, characterised in that the frame structure of the runnability component is provided with movement openings, such as grooves or slots, and that the structural element comprises mechanical attachment means, such as bolts, sliders or the like, which are arranged in the movement openings, in order to attach the frame part of the structural element in a movable manner to the frame structure of the runnability component.

8. Runnability component according to any of the claims 1-7, characterised in that the compressed air nozzle of the structural element is a slot nozzle or that it comprises a row of nozzle holes.

9. Runnability component according to claim 8, characterised in that the structure of the compressed air nozzle of the structural element varies in the longitudinal direction of the structural element.

10. Runnability component according to claim 9, characterised in that the size of and/or distance between the nozzle openings of the compressed air nozzle varies in the longitudinal direction of the structural element.

11. Runnability component according to claim 9, characterised in that in the structural element the width of the nozzle gap of the slot nozzle or the diameter of the nozzle holes of the compressed air nozzle is larger on the first and/or second edge area of the structural element than in the middle part of the structural element.

12. Runnability component according to any of the claims 1-11 , characterised in that the structural element further comprises a mechanical sealing element, such as an elongated sealing strip or a labyrinth sealing.

13. Runnability component according to claim 12, characterised in that the mechanical sealing element is arranged to extend 5-30 % from the first and/or second edge of the structural element toward the opposite edge of the structural element, preferably to extend from the first edge of the structural element to the second edge, over the whole length of the structural element.

14. Runnability component according to claim 12 or 13, characterised in that in the structural element the mechanical sealing element is assembled in the longitudinal direction of structural element from several separate individual sealing element parts, the length of which is shorter than the length of the finished sealing element.

15. Runnability component according to claim 14, characterised in that the separate individual sealing element parts have differing properties, whereby the sealing property of the sealing element varies in the longitudinal direction of the structural element.

16. A method for improving the efficiency of a runnability component of a paper machine or the like, characterised in that

a structural element is retrofitted to an existing runnability component, which comprises an elongated box-like frame structure, the volume of which is limited by a first and a second side, and upper and lower sides connecting them, and a sealing member arranged on the first side of the frame structure, i.e. on the entry side of the runnability component, which structural element comprises

- an elongated frame part,

- a compressed air nozzle arranged in connection with the elongated frame part,

- attachment means for attaching the frame part to the runnability component.

17. Method according to claim 16, characterised in that the structural element is retrofitted beneath the sealing member on the first side of the runnability component, i.e. on the entry side, to the immediate vicinity of the sealing member.

18. Method according to claim 16, characterised in that compressed air is fed into the compressed air nozzle arranged in the frame part of the structural element, the pressure of which compressed air is adjusted in the range of 1-6 bar, preferably 2-4 bar.

19. Method according to any of the claims 16-18, characterised in that the compressed air nozzle of the structural element is connected to a compressed air system of a paper mill or the like.

20. Method according to any of the claims 16-19, characterised in that the structural element is retrofitted to the runnability component so that it is turnable around a longitudinal axis of the frame structure of the runnability component.

21. Method according to claim 20, characterised in that by moving the structural element by turning, the direction and distance of the compressed air blow from the web is adjusted.

22. Method according to any of the claims 16-21 , characterised in that at least one mechanical lower sealing element is arranged in the lower side of the runnability component.

23. Method according to claim 22, characterised in that a blow member on the second side of the runnability component, i.e. on the exit side, is removed from operation.