GB2089460A - Protecting a coated metal tube - Google Patents

Abstract

The invention relates to a material for protecting a metal element such as a metal tube to which an anti-corrosive coating e.g. bitumen has been applied during the transportation and storage thereof. According to the invention, the material is constituted by a synthetic material netting e.g. polypropylene or perforated sheet (Fig. 3 not shown). The netting comprises thin threads 1 and thicker threads 2. The sheet (Fig. 3) comprises ribs (6) on one face. The material is less than 3 mm thick. The largest dimension of an unbroken area does not exceed 5 mm. <IMAGE>

Description

SPECIFICATION Material for protecting a coated metal element, application process and metal element protected in this way The present invention relates to a protective material, particularly for the transportation and storage of a metal element such as a tube to which has been applied an anti-corrosive coating.

It is known that an anti-corrosive coating constituted by a coating of bitumen, polyethylene, polyurethane, epoxy resin or the like is applied to certain metal elements, such as for example steel tubes before they are used. During the transportation and storage of the elements, said coating must be protected, because even if they are locally damaged, this could rapidly lead to the corrosion of the protected element.

At present, this protection for transportation and storage purposes is generally in the form either of an asbestos felt or kraft paper. However, these materials have disadvantages.

Thus, it is known that the use of asbestos is forbidden in a certain number of countries and this is likely to be made general in the future.

In turn, kraft paper often makes it difficult to use the so-called "electric brush" inspection process. This inspection is frequently necessary for checking the integrity of the anti-corrosive coating and can only be satisfactorily performed on a dry product. However, kraft paper has the disadvantage of absorbing moisture and consequently making the test results problemmatical.

The present invention aims at obviating these disadvantages by providing a protective material which is reiatively inexpensive, which can be safely and easily used and which makes it possible to control the coating by the electric brush method.

To this end, the invention relates to a material for the protection of a metal element such as a tube to which an anti-corrosive coating is applied, during transportation and storage, wherein it comprises a synthetic material netting.

Preferably, the largest dimension of the continuous or unbroken areas of the netting does not exceed approximately 1 to 5mm.

Thus, as stated hereinbefore, it is desirable that the protective material does not prevent inspection of the coating by the electric brush method. The optimum value can easily be determined as a function of the voltage used for the inspection. For example, in the case of 10,000 V the dimensions of the continuous areas of the netting will be approximately 3 mm.

Advantageously, the thickness of the material according to the invention is less than approximately 3 mm and is preferably below 1.5 mm. The chosen value will essentially depend on the relationship between the desired protective characteristics and the weight and therefore the price of the material.

It should be noted that the protection of a metal element for transportation and storage is different from the anti-rock protection. Thus, a material with a thickness as defined hereinbefore cannot in itself protect a metal element in rocky ground.

However, it assists in the protection, so that the anti-rock protective material used on site, can therefore be of a lower quality and consequently cheaper.

According to a preferred embodiment of the invention on at least one of its faces, the material forms a series of ribs. Such ribs make it possible to use a material having a minimum weight, whilst still having good mechanical characteristics, thereby offering a maximum protection. Moreover, when the ribs are formed on the outer face of the protective material, i.e. on the face opposite to the coating, it makes it possible to prevent the relative sliding of two metal elements placed on top of one another and covered with the protective material.

The inner face, i.e. that in full contact with the coating, is preferably smooth so as to prevent it from being embedded in the coating.

According to an embodiment of the invention, the ribs are formed by threads of the netting and their transverse dimension is larger than that of the other threads. Thus, protection is essentially ensured by the thicker threads, whilst the thinner threads prevent the penetration of the netting into the anti-corrosive coating.

The protective material according to the invention is advantageously made from polypropylene. Other synthetic materials and particularly other polyolefins can be used, but polypropylene is advantageous as a result of its price and the fact that it can be applied to the still hot anti-corrosive coating.

The invention also relates to a process for the protection for transportation and storage purposes of a tube to which is applied anti-corrosive coating, wherein it comprises a stage consisting of helically winding onto the coated tube a strip of a protective material as described hereinbefore.

The invention also relates to a metal element such as a tube covered with a protective material as described hereinbefore.

The invention is described in greater detail hereinafter relative to non-limitative embodiments and the attached drawings, wherein show: Fig 1 a plan view of a protective material accordingtotheinvention.

Fig 2 a section along the line 11II of Fig 1.

Fig 3 a plan view of another embodiment of a material according to the invention.

Fig 4 a section along the line IVIV of Fig 3.

Fig 5 a section along the line VV of Fig 3.

Fig 6 a view of a section of the tube covered with a material according to the invention.

Fig 7 a sectional view of a metal element to which is applied a protective material according to the invention.

The material shown in Figs 1 and 2 is in the form of a synthetic material netting produced, for example, by a process as described in French Patents 1,189,863 and 1,303,014. This netting comprises two groups of threads which intersect at right angles. Each of the groups of threads consists of relatively thin threads 1 and thicker threads 2.

In Fig 2, it can be seen that threads 2 project from the faces 3a, 3b of the netting constituted by the fine threads 1. These projections form ribs giving a greater stability to the netting.

The netting of Figs 1 and 2 is, for example, made from white polypropylene, whilst other materials may also be used. However, polypropylene is relatively inexpensive and its white colour ensures a better light reflection and consequently an effective protection of the bitumen layer, particularly against sun rays.

Another protective material is shown in Figs 3 to 5. This material, which can still be considered as an extruded netting is in the form of a sheet with orifices 4.

One face 5a of the sheet is smooth, whilst its other face 5b has a series of parallel ribs 6. Thus, between the ribs 6 there are either orifices 4 (Fig 5) or planar areas 7 (Fig 4). Areas 7 have, for example, a maximum dimension of approximately 3 mm, which is sufficiently small to permit inspection by the electric brush process of the coating which is to be protected by this material.

As hereinbefore, the sheet of material according to Figs 3 to 5 is advantageously made from white polypropylene.

Fig 7 shows a protective material 8 according to the invention, e.g. according to Figs 1 or 2 or 3 to 5, placed above an anti-corrosive coating 9 positioned on the surface of a metal element 10.

Element 10 is, for example, a steel tube and its coating 9 can be a 3 to 4 mm thick bitumen coating.

Fig 6 shows a tube 11 protected by means of a material according to the invention. A strip 12 is helically wound around tube 1 The strip is made from a protective material according to the invention and as described, for example, with reference to Figs 1 and 2 or 3 to 5.

In the case where the protective material used is in accordance with Figs 3 to 5, its ribs 6 are preferably disposed on the outside, i.e. its face 5a is in contact with the anti-corrosive coating, e.g. in contact with the bitumen coating 9.

It should also be noted that the nettings according to the invention cathodically protect the metal elements due to the perforation thereof.

However, as these perforations are of small size, the protective material according to the invention for protecting said elements during transportation and storage, also provides a certain protection with respect to rocks, so that the materials used for providing protection against rocks can be of a lower quality than that hitherto required.

Although the invention has been described hereinbefore with respect to specific embodiments, numerous variants are possible thereto without passing beyond the scope of the invention.

Claims (11)

1. A material for the protection during transportation and storage of a metal element such as a tube, to which is applied an anticorrosive coating, wherein it is constituted from a synthetic material netting.

2. A protective material according to claim 1, wherein the largest dimension of the continuous or unbroken areas of the netting does not exceed approximately 1 to 5 mm.

3. A protective material according to claims 1 or 2, wherein its thickness is below approximately 3 mm.

4. A protective material according to claim 3, wherein its thickness-is below 1.5 mm.

5. A protective material according to any one of the claims 1 to 4, wherein it forms a series of ribs over at least one of its faces.

6. A protective material according to claim 5, wherein the ribs are formed by the threads of the netting and their transverse dimension exceeds that of the other threads.

7. A protective material according to any of the claims 1 to 6, wherein at least one of its faces is substantially smooth.

8. A protective material according to any one of the claims 1 to 7, wherein it is made from polypropylene.

9. A protective material according to any one of the claims 1 to 8, wherein its colour is white.

10. A process for the protection of a tube to which an anti-corrosive coating has been applied during transportation and storage thereof, wherein it comprises the stage consisting of helically winding onto the coated tube a strip of a protective material according to any one of the claims 1 to 9.

11. A metal element such as a tube, wherein it is covered with a protective material according to any one of claims 1 to 9.