GB1573814A - Sheathed pipe - Google Patents

Description

(54) A SHEATHED PIPE (71) We, MANNESMANN AKTIEN GESELLSCHAFT, a German Body Corporate of 2 Mannesmannufer, 4 Düssledorf 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement.

The invention relates to a pipe for natural gas or petroleum having a protective sheath formed of an elastic material.

Accordingly the present invention provides a sheathed pipe for conveying natural gas or petroleum, wherein the sheath is formed from an elastic material which contains powdered iron, so that when placed in water the sheathed pipe has a negative buoyancy and can be laid on a sub-aqueous bed wthout additional weighting.

Powdered iron may be produced by the so-called "RZ process". In this process, scrap iron is melted for example in a cupola furnace, and the iron becomes carburised by contact with the coke which is present. After the liquid iron is teemed from the furnace into a ladle, the melt is atomised by means of compressed air. In practice, the liquid iron runs in a stream from the bottom outlet of the ladle into a nozzle, where it is acted upon by compressed air. In this atomisation process, the pouring speed, the compressed air pressure and the stream diameter are so chosen that an equilibrium is established between the carbon content and the corresponding iron oxide. After cooling, a raw powder which consists of iron grains surrounded by an oxide skin is available which is normally converted subsequently by annealing to pure iron powder. However, in the present invention, the raw powder which is normally regarded as an intermediate product, is used in the sheaths for weighting purposes. Conveniently, the powdered iron is introduced into the elastic material mixture which may be rubber before a band or flexible tube is produced therefrom and the pipe is covered by a sheath so formed using conventional means.

Raw powder produced by the RZ process is substantially cheaper than other forms of powdered iron but at the same time produces the necessary negative bouyancy of the pipe after welding and laying, without prejudicing the elasticity and the bending strength of the sheathing.

The fact that the powdered iron grains are surrounded by oxide skins ensures adequate protection against corrosion. 90 kg of powdered iron per metre are required for producing the necessary negative bouyancy in the case of a conduit of 500 mm +.

In addition to the powdered iron the sheath may contain other powders with a high specific gravity. For example, a powdered ore such as pulverised galena may be added.

In a preferred embodiment, a further sheath which has good resistance properties e.g.

against corrosion and abrasion is applied to the sheath containing the powdered iron.

WHAT WE CLAIM IS: 1. A sheathed pipe for conveying natural gas or petroleum, wherein the sheath is formed from an elastic material which contains powdered iron, so that when placed in water, the sheathed pipe has a negative buoyancy and can be laid on a sub-aqueous bed without additional weighting.

2. A pipe as claimed in Claim 1, wherein the elastic material is a rubber mixture.

3. A pipe as claimed in Claim 1 or 2, wherein the powdered iron is a raw powder obtained by atomisation of an iron melt.

4. A pipe as claimed in any one of the preceding claims, wherein a further sheath which has good corrosion and abrasion resistance properties is applied to the sheath containing the powdered iron.

5. A pipe as claimed in any one of the preceding claims wherein the sheath containing the powdered iron also contains a powdered material of high specific gravity.

6. A pipe as claimed in Claim 5, wherein the powdered material is pulverised galena.

7. A pipe as claimed in Claim 1 substantially as herein described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. (54) A SHEATHED PIPE (71) We, MANNESMANN AKTIEN GESELLSCHAFT, a German Body Corporate of 2 Mannesmannufer, 4 Düssledorf 1, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement. The invention relates to a pipe for natural gas or petroleum having a protective sheath formed of an elastic material. Accordingly the present invention provides a sheathed pipe for conveying natural gas or petroleum, wherein the sheath is formed from an elastic material which contains powdered iron, so that when placed in water the sheathed pipe has a negative buoyancy and can be laid on a sub-aqueous bed wthout additional weighting. Powdered iron may be produced by the so-called "RZ process". In this process, scrap iron is melted for example in a cupola furnace, and the iron becomes carburised by contact with the coke which is present. After the liquid iron is teemed from the furnace into a ladle, the melt is atomised by means of compressed air. In practice, the liquid iron runs in a stream from the bottom outlet of the ladle into a nozzle, where it is acted upon by compressed air. In this atomisation process, the pouring speed, the compressed air pressure and the stream diameter are so chosen that an equilibrium is established between the carbon content and the corresponding iron oxide. After cooling, a raw powder which consists of iron grains surrounded by an oxide skin is available which is normally converted subsequently by annealing to pure iron powder. However, in the present invention, the raw powder which is normally regarded as an intermediate product, is used in the sheaths for weighting purposes. Conveniently, the powdered iron is introduced into the elastic material mixture which may be rubber before a band or flexible tube is produced therefrom and the pipe is covered by a sheath so formed using conventional means. Raw powder produced by the RZ process is substantially cheaper than other forms of powdered iron but at the same time produces the necessary negative bouyancy of the pipe after welding and laying, without prejudicing the elasticity and the bending strength of the sheathing. The fact that the powdered iron grains are surrounded by oxide skins ensures adequate protection against corrosion. 90 kg of powdered iron per metre are required for producing the necessary negative bouyancy in the case of a conduit of 500 mm +. In addition to the powdered iron the sheath may contain other powders with a high specific gravity. For example, a powdered ore such as pulverised galena may be added. In a preferred embodiment, a further sheath which has good resistance properties e.g. against corrosion and abrasion is applied to the sheath containing the powdered iron. WHAT WE CLAIM IS:

1. A sheathed pipe for conveying natural gas or petroleum, wherein the sheath is formed from an elastic material which contains powdered iron, so that when placed in water, the sheathed pipe has a negative buoyancy and can be laid on a sub-aqueous bed without additional weighting.

2. A pipe as claimed in Claim 1, wherein the elastic material is a rubber mixture.

3. A pipe as claimed in Claim 1 or 2, wherein the powdered iron is a raw powder obtained by atomisation of an iron melt.

4. A pipe as claimed in any one of the preceding claims, wherein a further sheath which has good corrosion and abrasion resistance properties is applied to the sheath containing the powdered iron.

5. A pipe as claimed in any one of the preceding claims wherein the sheath containing the powdered iron also contains a powdered material of high specific gravity.

6. A pipe as claimed in Claim 5, wherein the powdered material is pulverised galena.

7. A pipe as claimed in Claim 1 substantially as herein described.