Mannesmann Aktiengesellschaft

Walter Stucke

Helmut Landgraf

Karl-Heinz Glissmann

Walter Meyer

In a method for continuously jacketing steel objects particularly tubing including the steps of cleaning the object by means of blasting its surface; chromatizing the cleaned surface by exposing the surface to a silicate containing watery solution of 3 and/or 6 valued chromium compound or compounds, drying the object at a temperature preferably between 105 degrees C. and 130 degrees C. which is well below the temperature necessary either for an application of a bonding and cover layer and/or for curing of the epoxy resin; a blend being applied prior to conversion of the chromatizing medium and any chromium iron compounds into a thermally stable intermediate layer including a chromium iron silicate oxide layer, the application of epoxy resin curing agent is carried out in two steps to obtain at least two sublayers, the first one of the layer being more reactive than the second one at temperature below 170 degrees C. and the two sublayers are cured together thereafter at a temperature between 170 to 240 degrees C., the first sublayer is applied in the liquidous state and the second layer is applied as a powder.

Jacketing steel objects

A method for making a polyethylene jacket on steel pipes including applying an inner foil upon the preheated steel pipe for purposes of providing adhesion thereto and of an outer, jacketing foil, also to be applied through a duel extrusion head which is to be heated to an operating temperature of approximately 170.degree. C. During extrusion, a gaseous mixture is fed to the space between the surface of the tube to be jacketed and the inner foil, which gaseous mixture consists of air to which a reactive gaseous component, such as ozone, has been added; the inner foils is made from a material so that the gaseous mixture reacts under the formation of groups which provide adhesion, such as carboxylic groups.

Method and device for jacketing a steel pipe with several plastic

The disclosed method is particularly applicable for jacketing pipes of a diameter of between 50 mm and 500 mm and is provided for high jacketing speeds and high throughputs. The pipe is heated initially to a temperature at least sufficient to cause a subsequently applied epoxy resin-curing agent powder blend to melt; a coherent and uniform epoxy coating is desired which may require subsequent heating of the epoxy coating. The epoxy coating will cure at a temperature from 145 degrees Centigrade to 155 degrees Centigrade within 50 to 70 minutes and the layer thickness should be between 30 and 50 micrometers. Prior to applying the jacket, the thermally produced reaction products must escape; this is ensured by an infrared radiation step which raises the temperature to about 200 degrees Centigrade. In the case of a thermo-sensitive interior of the steel pipe, this heating step provides not only for the evaporation of reaction products, but it is the same step which makes sure that the preheated and slightly melted powder obtains sufficient fluidity.

Method of jacketing steel pipes

The twin-nozzle extrusion head in accordance with the invention includes basically three axially spaced but radially overlapping annular housing members, together establishing two nozzle gaps and a first and a middle one of the two members are provided with annular feeder ducts for these nozzles. Each of these ducts has on its exit side a baffle ring wherein one baffle ring is effective on its radially inner surface while the second baffle ring is effective on a radially outer surface of larger diameter. These surfaces are nonround in a particular determined manner to establish nonuniform gap width related directly to the location of feed ducts for the annular channels, generally, the gaps are wider in locations away from a proximity of such feed ducts. The nozzle gaps are both frustoconical of different steepness and terminate in a common plane. The nozzles are particularly provided for disposing an adhesive on top of a steel pipe and a polyethylene coating and envelope on top of the adhesive.

Twin-nozzle extrusion head

A steel pipe is jacketed by concurrent extrusion of an ethylene hose concentric with a copolymer hose serving as an adhesive, the pipe passing through the extruder heat at an approximately 10% higher speed. The copolymer is predried, and the pipe is preferably precoated with heat-curable phenol or epoxy.

Jacketing steel tubes and pipes

Steel pipes pass through an extruder with a low-pressure antechamber for obtaining suction of an extruded hose against the pipe. The entrance to that antechamber is sealed by a combination of rubber elastic and spring steel disks, the latter having tongues being deflected by the pipe entering the chamber, and tongues of one disk sealingly cover the slots of an adjacent disk.

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Ratingen, Germany

Walter Stucke