WO2000045010A1

WO2000045010A1 - A method for providing a scaffold for at least one person in a substantially empty tank, and a scaffold

Info

Publication number: WO2000045010A1
Application number: PCT/SE2000/000050
Authority: WO
Inventors: Åke TÖRNQVIST
Original assignee: Toernqvist Aake
Priority date: 1999-01-15
Filing date: 2000-01-13
Publication date: 2000-08-03
Also published as: SE513400C2; SE9900105L; SE9900105D0

Abstract

The invention refers to a scaffold (4) for at least one person. The scaffold is arranged to be provided in a substantially empty tank (1), which is intended to receive a material and which has a significant size in relation to said person. The scaffold includes a chassis (5), which is introduceable into the tank and placeable on a floor of the tank, a mast member (6), which has a longitudinal axis (x) and is mountable on the chassis in such a way that the longitudinal axis extends substantially vertically, and a platform (7), which is arranged to carry said person and to be provided on the mast member (6) to be displaceable in a vertical direction on the mast member along an inner wall of the tank (1). The invention also refers to a method for providing such a scaffold.

Description

A method for providing a scaffold for at least one person in a substantially empty tank, and a scaffold

THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention refers to a method for providing a scaffold for at least one person in a substantially empty tank, which is intended to receive a product and which has a significant size in relation to said person.

Furthermore, the invention also refers to a scaffold for at least one person, which scaffold is arranged to be provided in a substantially empty tank, intended to receive a product and having a significant size in relation to said person.

Tanks of different types, for instance for storing petroleum products, require inner maintenance, such as inspection, cleaning and/or painting of the inner walls of the tank. Such tanks, which usually has a cylindrical shape, has a significant size and may have a diameter of 50 m and a height of 25 m. In connection with such maintenance, it is today known to build fixed scaffolds around the inner wall of the tank, wherein these scaffolds has to cover a significant surface, which in a tank of the above exemplified size amounts to 3,14 x 50 x 25 = 3925 m². Such fixed scaffolds therefore require a lot of material and a relatively long time for being built. The invention refers to tanks located on land as well as ship tanks .

It is also known to use so called hanging scaffolds for the maintenance of tanks . Such a hanging scaffold is suspended in two wires, which extend through the roof of the tank. In order to enable reaching around the whole inner wall of the tank by a scaffold being about 3m long, about 50 holes in the roof of the tank, through which the wires are to extend, are therefore required from the scaffold exemplified above in a tank. Before the maintenance work is started theses holes thus have to be done and after the maintenance work has been terminated the holes are to be welded again, which is a time consuming and difficult work requiring special measures due to the risk of explosions.

Such tanks normally have only one or a few number of openings giving access to the interior of the tank. For instance there may be an openable manhole in the proximity of the ground level and an openable manhole through the roof of the tank. Furthermore, such openings have small dimensions and therefore does not permit introduction of equipment having large dimensions.

A plurality of different scaffolds and masts are known for different purposes. DE 126437 discloses a carriage being displaceable on wheels and having a substantially vertical mast. The mast is of a relatively short length and manufactured in one piece. GB 2 128 958 discloses a conventional working scaffold having a mast which is mounted on a carriage with wheels. The scaffold includes a platform which is displaceable upwardly and downwardly along the substantially vertical mast. The device is intended to be located outdoors and includes no ^' means enabling mounting of a scaffold in a tank. SE 395 741 discloses a method for raising a mast by mounting the mast section from beneath. In order to keep the mast vertical, there are support lines, which are connected to the ground around the mast and which are arranged to be prolonged as the mast is raised. Consequently, the mast is not suitable to be provided in a tank. US 5,423,158 discloses a method and a device for raising a substantially vertical mast on a drill platform. The mast consists of a number of mast sections and the mast is raised by successively introducing mast sections from beneath. The device includes a lifting device by which the mast may be successively lifted upwardly in order to provide space for new mast sections.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method and a scaffold, which facilitate maintenance work in a tank.

This object is obtained by the method initially defined, which is characterised in that the scaffold includes a platform for carrying said person, a mast member and a chassis, wherein the method includes the steps of: introducing the platform, the mast member and the chassis into the tank as separate parts, placing the chassis on a floor in the tank, raising the mast member to extend substantially vertically from the chassis, and providing the platform on the mast member to be displaceable in a vertical direction on the mast member along an inner wall of the tank.

The provision of such a scaffold in a tank involves a significant simplification in relation to the previously provided scaffolds according to the prior art. The scaffold according to the invention may be raised relatively quickly and placed in a position where work is to be performed. Moreover, it is not necessary to make any holes or openings in the tank, but the manholes already provided are sufficient for introducing the material needed for the scaffold.

According to an embodiment of the invention, the mast member is raised by means of an elongated, flexible element, which extends between an upper end of the mast member and an upper part of the tank. By such an elongated flexible element, for instance a line or a wire, the raising of the mast member is substantially facilitated. The tanks normally have a manhole in the top thereof, through which such an elongated element may extend. Thereby, a windlass device may advantageously be provided on top of the roof.

According to a further embodiment of the invention, the mast member includes a number of mast sections, which are introduced as separate parts into the tank. By dividing the mast member into such sections, it may in an easy manner be introduced through present manholes in the tank. Advantageously, the lowest mast section of the mast member is mounted on the chassis in such a way that it extends substantially vertically, whereafter the platform is provided on the lowest mast section. Thereafter, the upper mast sections of the mast member may be mounted together to a mast unit arranged on the chassis, and advantageously on the lowest mast section which is already mounted on the chassis .

According to a further embodiment of the invention, the mast sections are mounted in such a way that a first mast section, forming the upper part of the mast member, is raised, that said first section is lifted by means of the elongated element, that the following mast sections are raised and introduced successively below the closest mast section located thereabove, and that adjacent mast sections are connected to each other in such a way that said mast unit is formed. By such a method, the mast member may be raised in a simple and convenient manner, wherein the mounting work, substantially, may be performed on the floor of the tank.

According to a further embodiment of the invention, the mast sections are positioned after each other on the floor of the tank and thereafter mounted to said mast unit. Also according to this method, the main mounting work may be performed in a convenient manner on the floor of the tank.

The object of the invention is also obtained by the scaffold initially defined, which is characterised by a chassis, which is introduceable into the tank and placeable on a floor of the tank, a mast member having a longitudinal axis and being mountable on the chassis in such a manner that the longitudinal axis extends substantially vertically, and a platform, which is arranged to carry said person and to be provided on said mast member to be displaceable in a vertical direction on the mast member along an inner wall of the tank. By such a scaffold, which is adapted to be introduced through a manhole of a tank, maintenance work in tanks is facilitated in a significant manner. Thereby, the mast member may include a number of mast sections which are introduceable into the cistern and mountable in the cistern in such a way that they form said mast member.

According to an embodiment of the invention, the chassis includes at least three lifting members, by which the chassis is liftable from the floor of the tank and which are individually adjustable in a vertical direction. By such lifting members, the chassis may be adjusted in such a way that the mast member extends substantially vertically. It is to be noted, that the expression "substantially vertically" includes that the mast member may have a small inclination of 0-5° towards the inner wall of the cistern in a mounted state .

According to a further embodiment of the invention, the chassis is provided with wheels, which are arranged to rest on the floor of the tank in order to facilitate the movement of the scaffold on the floor and which are individually adjustable in a vertical direction. Normally, the floor of such tanks is not plane but has a conical shape to incline upwardly towards the centre of the tank. Thanks to the individual adjustability of the wheels, the chassis may be displaced in the tank, at the same time as the substantially vertical extension of the mast member is maintained.

According to a further embodiment of the invention, the mast member includes a substantially horizontal beam element, which is provided in an upper end of the mast member. The beam element may be arranged to permit the mast member to be supported by the inner wall of the tank, which wall extends vertically. By such a beam member, it is advantageous if the mast member is somewhat inclined towards the wall of the tank, which gives the scaffold an improved stability. Furthermore, the beam element may include attachment members for a driving line for the displacement of the platform along the mast member, and a catching line, which is lockable by means of a brake member of the platform. The beam element may also include connection members for at least two pulling lines, which extend between and connect the beam element to the chassis. By such pulling lines, the stability of the mast member may be improved. Furthermore, at least one support member may be arranged to extend between the mast member and the chassis from a position between the upper end of the mast member and the chassis. Such support members also improve the stability of the mast member and may advantageously be designed as pipes. Advantageously, two such support members pass and cross each other in such a way that they permit the platform to pass an attachment device of the mast member to which the support members are connected.

According to a further embodiment of the invention, the platform is rotatable in relation to the chassis about the longitudinal axis. Tanks in ships for petroleum products frequently have a corrugated wall surface. Due to the fact that the platform is rotatable, the person performing the maintenance may always be located close to the inner wall of such a tank irrespective of if he is located in a valley or on a top of the corrugated wall .

Thereby, the mast member may be provided on the chassis by means of a member permitting rotation of the mast member in relation to the chassis about the longitudinal axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now to be explained more closely by means of different embodiments, which are described merely by way of the example, and with reference to the drawings attached.

Fig 1 discloses a tank with a scaffold according to a first embodiment of the invention.

Fig 2 discloses a side view of the scaffold in Fig 1.

Fig 3 discloses another side view of the scaffold in Fig

1. F Fiigg 4 4 discloses a view from above of the scaffold in Fig

1.

Fig 5 discloses a side view of a scaffold according to a second embodiment in a first position.

Fig 6 discloses a view from above of the scaffold in Fig 5.

Fig 7 discloses a side view of the scaffold in Fig 5 in a second position.

Fig 8 discloses a view from above of the scaffold in Fig

7. F Fiigg 9 9 discloses a side view of the scaffold in Fig 5 in the first and second positions, respectively. Figs 10-11 disclose different working operations of a first manner of mounting the scaffold according to the invention. Figs 12-13 disclose different working operations of a second manner of mounting the scaffold according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Fig 1 discloses a tank, which in the example disclosed is intended for products within the petro-chemical industry, for instance oil. Such a tank may have a diameter of about 50 m and a height of above 25 m. The tank 1 includes a first manhole 2, which is provided in the proximity of the ground plane and normally has a diameter of about 600 mm, and a second manhole 3, which is provided on the roof of the tank 1. Both the manholes 2, 3 are provided with doors to be attached by means of screw connections .

In the tank 1 a scaffold 4 according to the present invention is provided. The scaffold 4 includes a chassis 5, which is arranged to bear against the floor of the tank 1, and a mast member 6, which has a longitudinal axis x. The mast member 6 is mounted on the chassis 5 in such a way that the longitudinal axis x extends substantially vertically. According to a preferred embodiment, the mast member may however be somewhat inclined so that the axis x forms an angle v to the vertical inner wall of the tank 1. The angle v may be between 0 and 5°, preferably between 0,2 and 1°, for instance 0,6°. The mast member 6 includes a number of mast sections 6', 6'', <ό' ' ' etc, see Fig 10. Each mast section 6', < ' ' ... has a cross-sectional diameter which is about 400 x 300 mm. Furthermore, the scaffold 4 includes a platform 7, which is arranged to carry one or two persons to perform maintenance work on the inner wall of the tank. The platform 7 includes two platform portions 1 ' and 7'', see Fig 4, which each has a surface which is about 400 x 700 mm. The platform 7 is provided on the mast member 6 and displaceable in a vertical direction on the mast member 6 by means of a driving line 8 and a driving motor 9. The driving motor 9 is provided on the platform 7 and the driving line is connected to a beam element 10 which is provided at the upper end of the mast member 6 and extends substantially horizontally. Furthermore, Fig 1 discloses one of two support members 11, which extend between the chassis and a attachment device 12 which is mounted at about the centre of the mast member 6.

Fig 2-4 discloses more closely the construction of the scaffold 4. As appears from Figs 2 and 4, the chassis includes four wheels 13 by means of which the scaffold 4 may be displaced on the floor of the tank 1. The wheels 13 may be individually adjustable in a vertical direction so that for instance the wheels 13 located close to the wall of the tank are positioned at a lower level than the wheels 13 located more closely to the centre of the tank 1, see Fig 4, whereby the substantially vertical extension of the mast member 6 may be maintained although the floor of the tank 1 has a conical shape and slopes upwardly towards the centre of the tank 1. Furthermore, the chassis disclosed includes five or six lifting members 14, which may be designed as jacks. One lifting member 14 is arranged in each corner of the chassis 5 and two lifting members are provided at the end of a respective bar member 15, which extends substantially horizontally outwardly from the chassis 5.

The tubular support members 11 disclosed in Fig 1 are thus connected to the mast member at said attachment device 12 and extend in such a way that they cross each other and are in the lower end connected to a respective bar member 15, which clearly appears from Fig 4.

The beam element 10 is designed as a telescopic beam and thus the beam element 10 is prolongable. Consequently, the beam element 10 includes a first part which is fixedly provided at the upper end of the mast member 6 and a second part which is telescopically provided in the first part and radially extendible therefrom. The second part includes at its outer end a support wheel 16 which is arranged to abut the inner wall of the cylinder 1, see Fig 4. Moreover, the beam element 10 includes two connecting members 17, see Fig 4, section B-B, which each is arranged to be connected to two pulling lines 18, which extend between the connecting members 17 and a respective attachment 19 on the chassis 5. By pretensioning these pulling lines 18 an improved stability of the mast member 6 is obtained in a lateral direction. Furthermore, the beam element 10 includes an attachment member 20, see Fig 4, section A-A, for the driving line 8 and a catching line 21, which is lockable by means of a brake member provided in the casing which also encloses the driving motor 9 of the platform 7. The platform 7 is provided on a frame 22, which has a lower set of wheels and an upper set of wheels 23, see Fig 4. Each wheel set includes six rolling wheels 24, which are provided in groups of three in such a way that each group abuts three sides of a substantially vertical square profile 25 forming a part of the mast member 6.

Fig 5-9 discloses another embodiment of the scaffold 4. This scaffold 4 differs from the first embodiment in that the mast member 6 is mounted on a member 26 permitting the rotation of the mast member 6 in relation to the chassis 5.

The member 26 may for instance be a so called roller path.

Since the mast member 6 is to be rotatable this scaffold 4 lacks the support members 11 and the pulling lines 18 provided according to the first embodiment. Therefore, the scaffold 4 according to the second embodiment is not suitable to reach the same height as according to the first embodiment. The scaffold 4 according to the second embodiment may be about 15 m high whereas the scaffold according to the first embodiment may be at least 25-30 m high. Whereas the scaffold 4 according to the first embodiment is intended for tanks having substantially smooth inner walls, the scaffold 4 according to the second embodiment is in the first place intended for tanks of ships. Such a tank 27 is disclosed in Fig 9 and it appears from this figure that the side wall of the tank 27 is corrugated. By the scaffold according to the invention, the platform 7 may thus be rotated in such a way that it always is located close to the wall surface irrespective of if the platform 7 is positioned opposite to a valley, compare the position A in Fig 9, or a top, compare the position B in Fig 9.

Fig 10 discloses a manner of raising the mast member 6. In a first step, all components of the scaffold 4 are introduced through the manhole 2 as separate parts. In the next step, the lowest mast section 6' is mounted on the chassis 5, whereafter the platform 7 is moved down on the lowest mast section 6 from above. The uppermost mast section 6'' is attached to an elongated element in the form of a line or wire 30, which is a part of a windlass 31. By means of the windlass 31 the uppermost mast section 6' ' is lifted upwardly, whereafter the second uppermost mast section 6' ' ' is introduced in under the uppermost mast section 6' ' . Thereafter the two uppermost mast sections 6' ' and 6' ' ' are mounted together by means of a screw connection. Thereafter the remaining mast sections are successively introduced in under the two uppermost mast sections 6' ' , 6' ' ' and mounted together in a corresponding manner until a hole mast unit 32 is obtained. As appears from Fig 11, the whole of this mast unit is lifted by means of the windlass device 31, wherein the chassis 5 with the lowermost mast section 6' is introduced in under the mast unit 32. Thereafter the mast unit 32 is lowered down onto the lowest mast section 6' and the parts are mounted together. When the parts in this way have been mounted, the platform 7 may be connected to the driving line 8 and the catching line 21 and be displaced upwardly by means of the driving motor 9. From the platform 7 in its upper position, the line 30 may then be dismounted from the mast member 6 and the scaffold 4 is ready to be used.

Figs 12 and 13 disclose in a corresponding manner another method of mounting the mast . member 6. Thereby, the lowest mast section 6 is mounted, as in the first example on the chassis 5, whereafter the mast sections 6'', <ό' ' ' etc, are mounted together in a horizontal position on ^' the floor of the tank 1 to a hole mast unit 32. The whole mast unit 32 is then raised by means of the windlass device 31 and the line 30, and mounted to the lowest mast section 6' in a corresponding manner as in the first example.

The scaffold 4 according to the invention thus includes components having small dimension so that they may be introduced through the manhole 2. The cross-sectional area of the mast member 6 is thus a limiting factor for how much load the scaffold 4 may carry. Furthermore, also the platform 7 is of such size that its load capacity is limited. According to the invention, a way of raising a scaffold in a tank is offered in spite of these limitations. To raise a mast member in a conventional manner from below, wherein the mast sections are lifted upwardly and mounted successively by means of the platform which is displaced upwardly during the construction of the mast, does not appear to be practically possible in a tank having the limitations mentioned above. Such a construction presumes that the platform is equipped with a gear rack drive, i e the mast sections include a gear rack which is engaged by the driving motor of the platform. A scaffold according to this known manner is both heavier and has larger dimension than what is possible to obtain by the scaffold according to the present invention. The invention is not limited to the embodiments described above but may be varied and modified within the scope of the following claims. For instance, it is to be noted that the invention is applicable also to tanks for storing other products than petro-chemical products, for instance, silos and similar large containers.

Claims

1. A method of providing a scaffold (4) for at least one person in a substantially empty tank (1) , which is intended to receive a product and which has a significant size in relation to said person, characterised in that the scaffold includes a platform (7) for carrying said person, a mast member (6) and a chassis (5) , wherein the method includes the steps of: introducing the platform (7), the mast member and the chassis into the tank (1) as separate parts, placing the chassis (5) on a floor in the tank (1), raising the mast member (6) to extend substantially vertically from the chassis (5) , and providing the platform (7) on the mast member (6) to be displaceable in a vertical direction on the mast member (6) along an inner wall of the tank (1) .

2. A method according to claim 1, characterised in that the mast member (6) is raised by means of an elongated, flexible element (30), which extends between an upper end of the mast member (6) and an upper part of the tank (1) .

3. A method according to claim 2, characterised in that the mast member (6) includes a number of mast sections (6',

6' ' , . . . ) which are introduced as separate parts into the tank (1) .

4. A method according to claim 3, characterised in that the lowest mast section (6') of the mast member (6) is mounted on the chassis (5) in such a manner that it extends substantially vertically and that the platform (7) is provided on the lowest mast section (6') .

5. A method according to any one of claims 3 and 4, characterised in that the upper mast sections (6'', 6'''...) of the mast member (6) are mounted together to a mast unit (32) which is arranged on the chassis (5) .

6. A method according to claims 4 and 5, characterised in that said mast unit (32) is mounted on the lowest mast section (6' ) .

7. A method according to. any one of claims 5 and 6, characterised in that the mast sections (6'', 6' ' ' ) are mounted in such a way that a first mast section (6''), forming the upper part of the mast member (6), is raised, that said first section is lifted by means of the elongated element (30), that the following mast sections (6'''...) are raised and introduced successively below the closest mast section located thereabove, and that adjacent mast sections are connected to each other in such a manner that said mast unit (32) is formed.

8. A method according to any one of claims 5 and 6, characterised in that the mast sections (6'', 6'''...) are positioned after each other on the floor of the tank (1) and thereafter mounted to said mast unit (32) .

9. A method according to any one of claims 2 to 8, characterised in that said mast unit (32) is raised by means of the elongated element (30) which is wound on a windlass device (31) .

10. A method according to claim 9, characterised in that the windlass device (31) is provided on top of a roof of the tank (1) and that the elongated element (30) extends through a hole (2) in the roof.

11. A scaffold for at least one person, which scaffold (4) is arranged to be provided in a substantially empty tank (1) , intended to receive a product and having a significant size in relation to said person, characterised by a chassis (5) , which is introduceable into the tank (1) and placeable on a floor of the tank (1), a mast member (6) having a longitudinal axis (x) and being mountable on the chassis (5) in such a manner that the longitudinal axis (x) extends substantially vertically, and a platform (7), which is arranged to carry said person and to be provided on said mast member (6) to be displaceable in a vertical direction on the mast member (6) along an inner wall of the tank (1) .

12. A scaffold according to claim 11, characterised in that the mast member (6) includes a number of mast sections (6', 6'', . . .), which are introduceable into the tank (1) and mountable in the tank (1) in such manner that they form said mast member ( 6) .

13. A scaffold according to any one of claims 11 and 12, characterised in that the chassis (5) includes at least four lifting members (14), by which the chassis (5) is liftable from the floor of the tank (1) and which are individually adjustable in a vertical direction.

14. A scaffold according to any one of claims 11 to 13, characterised in that the chassis (5) is provided with wheels (13) , which are arranged to rest on the floor of the tank (1) to facilitate the movement of the scaffold (4) on the floor and which are individually adjustable in a vertical direction.

15. A scaffold according to any one of claims 11 to 14, characterised in that the mast member (6) includes a substantially horizontal beam element (10) which is provided in an upper part of the mast member (6) .

16. A scaffold according to claim 15, characterised in that the beam element (10) is arranged to permit the mast member (6) to be supported by the inner wall of the tank (1), which wall extends substantially vertically.

17. A scaffold according to any one of claims 15 and 16, characterised in that the beam element (10) includes attachment members (20) for a driving line (8) for the displacement of the platform (7) along the mast member (6) and a catching line (21) which is lockable by means of a brake member of the platform (7) .

18. A scaffold according to any one of claims 15 to 17, characterised in that the beam element (10) includes connecting members (17) for at least two pulling lines (18), which extend between and connect the beam element (10) to the chassis (5) .

19. A scaffold according to any one of claims 11 to 18, characterised by at least one support member (11) , which is arranged to extend between the mast member (6) and the chassis (5) from a position between the upper end of the mast member (6) and the chassis (5) .

20. A scaffold according to claim 19, characterised by two such support members (11) , which pass and cross each other and permit the platform (7) to pass an attachment device (12) of the mast member (6) to which the support members (11) are connected.

21. A scaffold according to any one of claims 11 and 15, characterised in that the platform (7) is rotatable in relation to the chassis (5) about the longitudinal axis (x) .

22. A scaffold according to claim 22, characterised in that the mast member (6) is provided on the chassis by means of a member, which permits rotation of the mast member (6) in relation to the chassis (5) about the longitudinal axis (x) .

23. A scaffold according to any one of claims 11 to 22, characterised by a windlass device (31) by which the mast member (6) is mountable on the chassis (5) in such a way that the longitudinal axis (x) extends substantially vertically.