EP0015894A1 - Process for coating the inside of pipes with plastics material and apparatus for carrying out said process - Google Patents

Process for coating the inside of pipes with plastics material and apparatus for carrying out said process Download PDF

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Publication number
EP0015894A1
EP0015894A1 EP19800890027 EP80890027A EP0015894A1 EP 0015894 A1 EP0015894 A1 EP 0015894A1 EP 19800890027 EP19800890027 EP 19800890027 EP 80890027 A EP80890027 A EP 80890027A EP 0015894 A1 EP0015894 A1 EP 0015894A1
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EP
European Patent Office
Prior art keywords
tube
powder
plastic
connection
filter
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Granted
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EP19800890027
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German (de)
French (fr)
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EP0015894B1 (en
Inventor
Walter Hans
Karl Hirn
Heinz Kohlbacher
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Voestalpine AG
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Voestalpine AG
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Publication of EP0015894A1 publication Critical patent/EP0015894A1/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/22—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to internal surfaces, e.g. of tubes

Definitions

  • the invention relates to a method for internally coating pipes with plastic, and to an apparatus for carrying out this method.
  • Metal pipes in particular steel pipes, are used in many areas for the transport of liquids and gases. The media are often aggressive and this can lead to corrosion, destroying the pipes.
  • the invention relates in particular to a method for the inner coating of pipes with plastic, plastic powder being sucked into the pipe, which possibly rotates about its axis, by means of a carrier gas, and the plastic powder is fritted onto the heated pipe wall, whereupon the amount of powder which has not been fritted is suctioned off again if necessary, the fritted plastic layer is smoothed by further heating and, if necessary, an adhesion promoter is introduced into the tube before the plastic powder is introduced.
  • the suction speed is slowed down when the tube is filled with plastic powder or stopped. This method therefore requires a complicated regulation and can only be carried out with difficulty.
  • plastic powder in an amount of about 1 kg / m 2 to an air stream, and to cause the plastic powder to break onto the inner surface of a tube through which this air stream flows by means of an induction coil.
  • the plastic is then smoothed by further heating by induction coils.
  • the present invention now seeks to provide a particularly simple and economical method for coating pipes of the type mentioned at the outset, with which a uniform layer thickness can be achieved in a simple manner.
  • the method according to the invention essentially consists in filtering the carrier gas after the plastic powder flows through the tube separated and the plastic powder is retained in the tube for the time required for fritting. Because the plastic powder is filtered off from the carrier gas, the powder can be sucked in in a simple manner with conventional gas-producing pumps and the filling of the tube with the plastic powder occurs automatically after a certain time without special measures having to be taken. At the same time, a load on the gas-producing pump with hot plastic particles is avoided.
  • thermoplastic materials preferably polyvinyl chloride, polyvinyl acetate, or the copolymers of these polyvinyl compounds, polyolefins, for example polyethylene, polypropylene and polyamides, are suitable as plastic powder in the context of the present invention.
  • the plastic powder can advantageously be sucked into the tube in a form fluidized by the carrier gas.
  • Plastic powder in fluidized form behaves like a liquid and can be sucked in easily and without difficulty and sucked off again into a storage container.
  • the method according to the invention can be carried out in such a way that the carrier gas is passed through the filter in a circuit and the suction direction is reversed for the purpose of sucking off the plastic which has not been fritted, whereby a particularly economical method of operation is achieved and the pollution of the environment with pollutants is as low as possible is kept possible.
  • the device according to the invention for carrying out this method has a connection for the pipe to be coated and a further connection for the other end of the pipe to be coated which is connected to a storage container for plastic powder via a line.
  • the device according to the invention is characterized in that the further connection for the pipe to be coated is connected via a filter to the suction side of a gas-producing pump.
  • the filter prevents contamination of the gas-producing pump and provides the filling of the Pipe with plastic separated from the carrier gas.
  • An evacuable container is preferably switched on in the suction line between the filter and the pump.
  • the evacuable container should preferably have a volume which is greater than the volume of the tube to be filled with plastic. This container can now be evacuated by the pump.
  • the plastic powder with the carrier gas is sucked into the tube, whereby the plastic powder can be in fluidized form, in which it behaves like a liquid.
  • the carrier gas is now passed through the filter and can be discharged into the atmosphere via the evacuated container and the pump, the plastic powder being retained in the tube by the filter.
  • Air but preferably also gases such as nitrogen, carbon dioxide and other inert gases, which largely prevent oxidative degradation of the plastic used at elevated temperature, are suitable as carrier gas.
  • the plastic powder backed up by the filter fills the heated pipe and partially frits against the pipe wall. The portion of the powder which has not been fritted can be suctioned off by switching a directional control valve, it also being possible to provide a powder collecting vessel which is likewise under vacuum and to which no filter is connected upstream.
  • This further directional valve is expediently arranged between the filter and the connection for the pipe and in one position sets the connection for the pipe with the filter and in a further position with the return line.
  • the plastic powder in the pipe is sucked up to the filter.
  • the excess plastic powder can be sucked off into the powder collecting vessel and thus this plastic powder can be returned.
  • the suction side of the gas-producing pump can also be connected to the filter via a directional valve, or to the powder collection vessel with the interposition of a further filter.
  • the powder collecting vessel can be evacuated and the excess powder can be sucked off quickly.
  • the further filter which is arranged between the suction side of the pump and the powder collection vessel, likewise prevents plastic powder from entering the pump.
  • the directional valve provided between the storage container and the connection for the tube is expediently brought into a position in which the inlet side of the tube is in connection with the atmosphere, so that no further plastic is extracted when the excess plastic is sucked off is sucked up from the reservoir.
  • the storage container for the plastic powder can be sealed tightly, a return line opening into this storage container via a cooler.
  • the plastic powder, which has not been fritted, is returned to the storage container via this return line, the heat absorbed by the plastic powder being able to be dissipated again by the cooler.
  • a screw pump can easily be used as the conveying device for the excess powder from the tube.
  • 1 denotes the storage container for the plastic powder.
  • a connecting line 3 is connected to the pipe 4 via a tap 2.
  • the tube 4 is located in a heating furnace (not shown) and is brought to a temperature which is sufficient for frying the respective plastic powder.
  • the tube 4 is usually passed through a device for applying an adhesion promoter, which is not shown, before it is inserted into the holders 5 and connected to the storage container for the plastic, for example initially by sandblasting, bright annealing, pickling or the like . Cleaned pipe is sprayed with the primer inside in this adhesion promoter station.
  • the volatile constituents contained in the primer are vented in a known manner with compressed air and the tubes are then brought to a stoving temperature corresponding to the primer, for example to a temperature of about 200 to 300 ° C. After leaving the baking oven, not shown, the tubes are cooled to the sintering temperature of the plastic to be applied and are kept at this temperature during the coating, that is to say while they are inserted in the holders 5.
  • a filter 7 is connected to the end of the tube 4 facing away from the storage container 1 via a short line and a multi-way valve 6. Via the vacuum vessel 8, the line leads to the outside via the gas-producing pump.
  • the tube 4 can rotate in the holders 5 about its longitudinal axis, for which devices known per se, which are not shown in the drawing for the sake of clarity, are provided.
  • the vessel 8 is first evacuated with the gas-producing pump. Through the opening of the multi-way valve 6 powder from the container 1 in fluidized form via the line 3 through the Multi-way valve 2 sucked into the pipe 4. The powder column comes to a standstill on the filter 7, while the carrier gas flows further into the container 8 and is finally discharged into the atmosphere by the pump 10. After a period of 30 to 60 seconds, depending on the desired layer thickness, part of the plastic has fritted on the inner wall.
  • the tube 4 can rotate in the holders 5 about its longitudinal axis.
  • a vacuum is generated in the powder collecting vessel 11 by switching over another reusable valve 9 and closing a valve 13 by the pump 10.
  • the powder is sucked out of the tube 4 and collected in the container 11.
  • a filter 12 prevents powder from entering the pump and contaminating it.
  • the plastic powder is conveyed back from the powder collecting vessel 11 into the container 1 with a simple powder conveying device, for example a screw pump 15.
  • a cooler 14 is connected, which is arranged between the powder collecting vessel 11 and the screw pump 15.
  • the plastic powder can be used in the device according to the invention in densities of about 700 to 1000 kg / m.

Abstract

1. Process for internally coating tubes (4) with synthetic plastics material in which pulverulent synthetic plastics material is sucked my means of a carrier gas into the tube (4) optionally rotating around its axis and the pulverulent synthetic plastics material is sintered onto the heated wall of the tube, whereupon the amount of powder not sintered onto the tube wall is again sucked off and the carrier gas is separated by filtering from the powder after having passed the tube to be coated and the layer of synthetic plastics material sintered onto the tube is optionally smoothened by further heating, and an adhesion promotor being optionally introduced into the tube (4) prior to introducing the pulverulent synthetic plastics material, characterized in that the pulverulent synthetic plastics material is retained within the tube (4) during the time required for sintering, the column of pulverulent synthetic plastics material being brought to rest by means of a filter (7).

Description

Die Erfindung bezieht sich auf ein Verfahren zur Innenbeschichtung von Rohren mit Kunststoff, sowie auf eine Vorrichtung zur Durchführung dieses Verfahrens. Für den Transport von Flüssigkeiten und Gasen werden heute in vielen Bereichen Metallrohre, insbesondere Stahlrohre, verwendet. Die Medien sind oft aggressiv und es können dadurch Korrosionen auftreten, wobei die Rohrleitungen zerstört werden.The invention relates to a method for internally coating pipes with plastic, and to an apparatus for carrying out this method. Metal pipes, in particular steel pipes, are used in many areas for the transport of liquids and gases. The media are often aggressive and this can lead to corrosion, destroying the pipes.

Bei Rohren, die für solche Zwecke verwendet werden,ist es daher oft notwendig, vor allem die Innenfläche der Rohre mit einem Korrosionsschutz zu versehen, der gegen den zu transportierenden Stoff beständig ist.For pipes that are used for such purposes, it is therefore often necessary to provide the inner surface of the pipes with a corrosion protection that is resistant to the material to be transported.

Die Erfindung bezieht sich im besonderen auf ein Verfahren zur Innenbeschichtung von Rohren mit Kunststoff, wobei in das gegebenenfalls um seine Achse rotierende Rohr Kunststoffpulver unter Vermittlung eines Trägergases eingesaugt wird und das Kunststoffpulver an die erhitzte Rohrwand angefrittet wird, worauf die nicht angefrittete Pulvermenge wieder abgesaugt und gegebenenfalls die angefrittete Kunststoffschicht durch weiteres Erwärmen geglättet wird und wobei gegebenenfalls vor Einbringen des Kunststoffpulvers ein Haftvermittler in das Rohr eingebracht wird. Bei einem bekannten Verfahren dieser Art wird die Sauggeschwindigkeit am Ende der Anfüllung des Rohres mit Kunststoffpulver verlangsamt bzw. gestoppt. Dieses Verfahren erfordert daher eine komplizierte Regelung und ist nur mit Schwierigkeiten durchführbar. Bei diesem bekannten Verfahren wird ein in einem Wirbelbett aufgewirbeltes Pulver eingesetzt und ohne gleichzeitige Maßnahmen, mit welchen die Rotationsgeschwindigkeit des heißen Rohres verändert wird, erscheint bei diesem bekannten Verfahren ein Überzug mit gleichmäßigen Schichtstärken schwer erzielbar. Es ist weiters bekannt, Kunststoffpulver in stehende Rohre einzufüllen. Derartige Pulverschüttmethoden haben den Nachteil, daß das Hantieren mit den heißen mit Kunststoffpulver gefüllten Rohren umständlich ist, und darüberhinaus in Abhängigkeit von der Einfüllzeit die auf die Innenwand erzeugten Schichten sehr starken Schwankungen unterworfen sind. Die Schichtstärke nimmt bei diesen Verfahren üblicherweise vom unteren Ende zum oberen Ende des Rohres linear ab. Für Rohre mit relativ großem Innendurchmesser war es ohne weiteres möglich, den aufzubringenden Kunststoff durch in das Rohr eingeführte Sprüharme über die Innenoberfläche des Rohres zu verteilen. Derartige Verfahren sind aber für Rohre mit vergleichsweise geringem Durchmesser unbrauchbar.The invention relates in particular to a method for the inner coating of pipes with plastic, plastic powder being sucked into the pipe, which possibly rotates about its axis, by means of a carrier gas, and the plastic powder is fritted onto the heated pipe wall, whereupon the amount of powder which has not been fritted is suctioned off again if necessary, the fritted plastic layer is smoothed by further heating and, if necessary, an adhesion promoter is introduced into the tube before the plastic powder is introduced. In a known method of this type, the suction speed is slowed down when the tube is filled with plastic powder or stopped. This method therefore requires a complicated regulation and can only be carried out with difficulty. In this known method, a powder whirled up in a fluidized bed is used and without simultaneous measures with which the rotational speed of the hot tube is changed, a coating with uniform layer thicknesses appears difficult to achieve in this known method. It is also known to pour plastic powder into standing pipes. Such powder pouring methods have the disadvantage that handling the hot pipes filled with plastic powder is cumbersome and, depending on the filling time, the layers produced on the inner wall are subject to very strong fluctuations. In these processes, the layer thickness usually decreases linearly from the lower end to the upper end of the tube. For pipes with a relatively large inner diameter, it was readily possible to distribute the plastic to be applied over the inner surface of the pipe by spray arms inserted into the pipe. Such methods are unusable for pipes with a comparatively small diameter.

Es ist weiters bereits bekannt, Kunststoffpulver in einer Menge von etwa 1 kg/m einem Luftstrom zuzufügen, und das Anfritten des Kunststoffpulvers an der Innenfläche eines von diesem Luftstrom durchströmten Rohres durch eine Induktionsspule zu bewirken. Durch eine weitere Erhitzung durch Induktionsspulen wird der Kunststoff dann geglättet.It is furthermore already known to add plastic powder in an amount of about 1 kg / m 2 to an air stream, and to cause the plastic powder to break onto the inner surface of a tube through which this air stream flows by means of an induction coil. The plastic is then smoothed by further heating by induction coils.

Die vorliegende Erfindung sucht nun ein besonders einfaches und wirtschaftliches Verfahren zu einer Beschichtung von Rohren der eingangs genannten Art zu schaffen, mit welchem eine gleichmäßige Schichtstärke in einfacher Weise erzielbar wird. Das erfindungsgemäße Verfahren besteht zur Lösung dieser Aufgabe im wesentlichen darin, daß das Trägergas nach Durchströmen des Rohres vom Kunststoffpulver durch Abfiltern getrennt und das Kunststoffpulver im Rohr während der für das Anfritten erforderlichen Zeit zurückgehalten wird. Dadurch, daß das Kunststoffpulver vom Trägergas abgefiltert wird, kann das Einsaugen des Pulvers in einfacher Weise mit gewöhnlichen gasfördernden Pumpen vorgenommen werden und die Füllung des Rohres mit dem Kunststoffpulver tritt automatisch nach einer gewissen Zeit, ohne daß hiefür besondere Maßnahmen ergriffen werden müssen, ein. Gleichzeitig wird eine Belastung der gasfördernden Pumpe mit heißen Kunststoffteilchen vermieden. Insgesamt ergibt sich durch die Verwendung eines Filters als Abschluß der Kunststoffsäule im Rohr eine besonders einfache Verfahrensweise, bei der jede Manipulation am heißen Rohr entbehrlich ist und es ergibt sich daher für jeden Teilbereich der Innenwandung des Rohres eine etwa gleiche Zeitdauer für das Anfritten, so daß eine homogene und gleichmäßige Schichtstärke der Kunststoffbeschichtung erzielbar wird. Als Kunststoffpulver kommen im Rahmen der vorliegenden Erfindung eine Reihe von nahezu allen thermoplastischen Kunststoffen, vorzugsweise Polyvinylchlorid, Polyvinylazetat, bzw. die Copolymere dieser Polyvinylverbindungen, Polyolefine, beispielsweise Polyäthylen, Polypropylen und Polyamide in Frage.The present invention now seeks to provide a particularly simple and economical method for coating pipes of the type mentioned at the outset, with which a uniform layer thickness can be achieved in a simple manner. To achieve this object, the method according to the invention essentially consists in filtering the carrier gas after the plastic powder flows through the tube separated and the plastic powder is retained in the tube for the time required for fritting. Because the plastic powder is filtered off from the carrier gas, the powder can be sucked in in a simple manner with conventional gas-producing pumps and the filling of the tube with the plastic powder occurs automatically after a certain time without special measures having to be taken. At the same time, a load on the gas-producing pump with hot plastic particles is avoided. Overall, the use of a filter as the end of the plastic column in the tube results in a particularly simple procedure in which any manipulation on the hot tube is unnecessary, and therefore there is approximately the same time for the fritting for each section of the inner wall of the tube, so that a homogeneous and uniform layer thickness of the plastic coating can be achieved. A number of almost all thermoplastic materials, preferably polyvinyl chloride, polyvinyl acetate, or the copolymers of these polyvinyl compounds, polyolefins, for example polyethylene, polypropylene and polyamides, are suitable as plastic powder in the context of the present invention.

In vorteilhafter Weise kann beim erfindungsgemäßen Verfahren das Kunststoffpulver in durch das Trägergas fluidisierter Form in das Rohr eingesaugt werden. Kunststoffpulver in fluidisierter Form verhält sich wie eine Flüssigkeit und läßt sich in einfacher Weise und ohne Schwierigkeiten anzusaugen und in einen Vorratsbehälter wieder absaugen. Hiebei kann das erfindungsgemäße Verfahren so durchgeführt werden, daß das Trägergas durch den Filter hindurch im Kreislauf geführt wird und die Saugrichtung zum Zwecke des Absaugens des nicht angefritteten Kunststoffes umgekehrt wird, wodurch eine besonders wirtschaftliche Arbeitsweise erzielt und die Belastung der Umwelt mit Schadstoffen so gering wie möglich gehalten wird.In the method according to the invention, the plastic powder can advantageously be sucked into the tube in a form fluidized by the carrier gas. Plastic powder in fluidized form behaves like a liquid and can be sucked in easily and without difficulty and sucked off again into a storage container. The method according to the invention can be carried out in such a way that the carrier gas is passed through the filter in a circuit and the suction direction is reversed for the purpose of sucking off the plastic which has not been fritted, whereby a particularly economical method of operation is achieved and the pollution of the environment with pollutants is as low as possible is kept possible.

Die erfindungsgemäße Vorrichtung zur Durchführung dieses Verfahrens weist einendichtmit einem Vorratsbehälter für Kunststoffpulver über eine Leitung verbundenen Anschluß für das zu beschichtende Rohr und einen weiteren Anschluß für das andere Ende des zu beschichtenden Rohres auf. Zur einfachen Durchführung des eingangs genannten Verfahrens ist die Vorrichtung erfindungsgemäß dadurch gekennzeichnet, daß der weitere Anschluß für das zu beschichtende Rohr über ein Filter mit der Saugseite einer gasfördernden Pumpe in Verbindung steht.Das Filter verhindert hiebei eine Verunreinigung der gasfördernden Pumpe und stellt die Füllung des Rohres mit vom Trägergas getrenntem Kunststoff sicher. Vorzugsweise ist hiebei in die Saugleitung zwischen Filter und Pumpe ein evakuierbarer Behälter eingeschaltet. Der evakuierbare Behälter soll hiebei vorzugsweise ein Volumen aufweisen, welches größer ist als das Volumen des mit Kunststoff zu füllenden Rohres. Durch die Pumpe kann nun dieser Behälter evakuiert werden. Durch Öffnung eines zwischen dem Rohr und einem Vorratsbehälter für den Kunststoff angeordneten Wegeventils wird das Kunststoffpulver mit dem Trägergas in das Rohr gesaugt, wobei sich das Kunststoffpulver in fluidisierter Form befinden kann, in welcher es sich wie eine Flüssigkeit verhält. Das Trägergas wird nun durch den Filter hindurchgeführt und kann über den evakuierten Behälter und die Pumpe in die Atmosphäre abgeführt werden, wobei das Kunststoffpulver durch den Filter im Rohr zurückgehalten wird. Als Trägergas kommen Luft, vorzugsweise aber auch Gase, wie Stickstoff, Kohlendioxyd und andere inerte Gase in Frage, die einen oxydativen Abbau des verwendeten Kunststoffes bei erhöhter Temperatur weitgehend verhindern. Das durch den Filter zurückgestaute Kunststoffpulver füllt das erwärmte Rohr und frittet teilweise an die Rohrwand an. Das Absaugen des nicht angefritteten Teiles des Pulvers kann durch Umschalten eines Wegeventiles erfolgen, wobei ein gleichfalls unter Unterdruck stehendes Pulversammelgefäß, welchem kein Filter vorgeschaltet ist, vorgesehen sein kann.The device according to the invention for carrying out this method has a connection for the pipe to be coated and a further connection for the other end of the pipe to be coated which is connected to a storage container for plastic powder via a line. For simple implementation of the method mentioned at the outset, the device according to the invention is characterized in that the further connection for the pipe to be coated is connected via a filter to the suction side of a gas-producing pump. The filter prevents contamination of the gas-producing pump and provides the filling of the Pipe with plastic separated from the carrier gas. An evacuable container is preferably switched on in the suction line between the filter and the pump. The evacuable container should preferably have a volume which is greater than the volume of the tube to be filled with plastic. This container can now be evacuated by the pump. By opening a directional valve arranged between the tube and a storage container for the plastic, the plastic powder with the carrier gas is sucked into the tube, whereby the plastic powder can be in fluidized form, in which it behaves like a liquid. The carrier gas is now passed through the filter and can be discharged into the atmosphere via the evacuated container and the pump, the plastic powder being retained in the tube by the filter. Air, but preferably also gases such as nitrogen, carbon dioxide and other inert gases, which largely prevent oxidative degradation of the plastic used at elevated temperature, are suitable as carrier gas. The plastic powder backed up by the filter fills the heated pipe and partially frits against the pipe wall. The portion of the powder which has not been fritted can be suctioned off by switching a directional control valve, it also being possible to provide a powder collecting vessel which is likewise under vacuum and to which no filter is connected upstream.

Dieses weitere Wegeventil ist zweckmäßig zwischen dem Filter und dem Anschluß für das Rohr angeordnet und setzt in einer Stellung den Anschluß für das Rohr mit dem Filter und in einer weiteren Stellung mit der Rückführungsleitung in Verbindung. In der ersten Stellung wird somit das Kunststoffpulver im Rohr bis zum Filter gesaugt. Durch einfaches Umstellen des Wegeventiles kann ein Absaugen des überschüssigen Kunststoffpulvers in das Pulversammelgefäß und damit ein Rückführen dieses Kunststoffpulvers erzielt werden.This further directional valve is expediently arranged between the filter and the connection for the pipe and in one position sets the connection for the pipe with the filter and in a further position with the return line. In the first position, the plastic powder in the pipe is sucked up to the filter. By simply changing the directional control valve, the excess plastic powder can be sucked off into the powder collecting vessel and thus this plastic powder can be returned.

In einfacher Weise kann auch die Saugseite der gasfördernden Pumpe über ein Wegeventil wahlweise mit dem Filter oder unter Zwischenschaltung eines weiteren Filters mit dem Pulversammelgefäß in Verbindung gesetzt werden. Auf diese Weise kann das Pulversammelgefäß evakuiert werden und ein rasches Absaugen des überschüssigen Pulvers erzielt werden. Der weitere Filter, welcher zwischen Saugseite der Pumpe und dem Pulversammelgefäß angeordnet ist, verhindert hier gleichfalls ein Eintreten von Kunststoffpulver in die Pumpe. Während des Absaugens des überschüssigen Kunststoffpulvers aus dem Rohr wird zweckmäßig das zwischen dem Vorratsbehälter und dem Anschluß für das Rohr vorgesehene Wegeventil in eine Stellung gebracht, in welcher die Eingangsseite des Rohres mit der Atmosphäre in Verbindung steht, sodaß beim Absaugen des überschüssigen Kunststoffes kein weiterer Kunststoff aus dem Vorratsbehälter nachgesaugt wird.In a simple manner, the suction side of the gas-producing pump can also be connected to the filter via a directional valve, or to the powder collection vessel with the interposition of a further filter. In this way, the powder collecting vessel can be evacuated and the excess powder can be sucked off quickly. The further filter, which is arranged between the suction side of the pump and the powder collection vessel, likewise prevents plastic powder from entering the pump. During the suction of the excess plastic powder from the tube, the directional valve provided between the storage container and the connection for the tube is expediently brought into a position in which the inlet side of the tube is in connection with the atmosphere, so that no further plastic is extracted when the excess plastic is sucked off is sucked up from the reservoir.

Vorzugsweise ist hiebei der Vorratsbehälter für das Kunststoffpulver dicht abschließbar, wobei eine Rückführungsleitung über einen Kühler in diesen Vorratsbehälter mündet. Über diese Rückführungsleitung wird das nicht angefrittete Kunststoffpulver wieder zum Vorratsbehälter zurückgeführt, wobei die vom Kunststoffpulver aufgenommene Wärme vom Kühler wieder abgeführt werden kann. Als Fördereinrichtung für das überschüssige Pulver aus dem Rohr Kommt in einfacher Weise eine Schneckenpumpe in Betracht.Preferably, the storage container for the plastic powder can be sealed tightly, a return line opening into this storage container via a cooler. The plastic powder, which has not been fritted, is returned to the storage container via this return line, the heat absorbed by the plastic powder being able to be dissipated again by the cooler. A screw pump can easily be used as the conveying device for the excess powder from the tube.

Die Erfindung wird nachfolgend anhand eines in der Zeichnung dargestellten Ausführungsbeispieles näher erläutert.The invention is explained below with reference to an embodiment shown in the drawing.

In der Zeichnung ist mit 1 der Vorratsbehälter für das Kunststoffpulver bezeichnet. Von diesem Vorratsbehälter 1 ausgehend ist eine Verbindungsleitung 3 über einen Hahn 2 an das Rohr 4 angeschlossen. Das Rohr 4. befindet sich in einem nicht dargestellten Wärmeofen und wird auf eine Temperatur, welche für das Anfritten des jeweiligen Kunststoffpulvers ausreicht, gebracht. Das Rohr 4 wird üblicherweise, bevor es in die Halterungen 5 eingesetzt wird und mit dem Vorratsbehälter für den Kunststoff verbunden wird, durch eine Einrichtung zum Aufbringen eines Haftvermittlers geführt, welche nicht dargestellt ist.Ein zunächst beispielsweise durch Sandstrahlen, Blankglühen, Beizen od.dgl. gereinigtes Rohr wird in dieser Haftvermittlerstation mit Haftgrund innen besprüht. Die im Haftgrund enthaltenen flüchtigen Anteile werden in bekannter Weise mit Preßluft abgelüftet und die Rohre werden hierauf auf eine dem Haftvermittler entsprechende Einbrenntemperatur, beispielsweise auf eine Temperatur von etwa 200 bis 300°C, gebracht. Nach Verlassen des nicht dargestellten Einbrennofens werden die Rohre auf die Sintertemperatur des aufzutragenden Kunststoffes gekühlt und auf dieser Temperatur während der Beschichtung, d.h. also während sie in den Halterungen 5 eingesetzt sind, gehalten. An das dem Vorratsbehälter l abgewendete Ende des Rohres 4 ist über eine kurze Leitung und einen Mehrwegehahn 6 ein Filter 7 angeschlossen. Über das Unterdruckgefäß 8 führt die Leitung über die gasfördernde Pumpe ins Freie. Das Rohr 4 kann in den Halterungen 5 um seine Längsachse rotieren, wofür an sich bekannte, der Übersichtlichkeit halber in der Zeichnung nicht dargestellte Einrichtungen vorgesehen sind. Mit der gasfördernden Pumpe wird das Gefäß 8 zunächst evakuiert. Durch die Öffnung des Mehrwegehahnes 6 wird Pulver aus dem Behälter 1 in fluidisierter Form über die Leitung 3 durch den Mehrwegehahn 2 in das Rohr 4 eingesaugt. Die Pulversäule kommt am Filter 7 zum Stillstand, während das Trägergas in den Behälter 8 weiterströmt und schließlich durch die Pumpe 10 in die Atmosphäre abgeführt wird. Nach einer Zeit von 30 bis 60 sec, je nach gewünschter Schichtdicke, ist ein Teil des Kunststoffes an der Innenwand angefrittet. Das Rohr 4 kann in den Halterungen 5 um seine Längsachse rotieren. In dieser Zeit wird durch Umschalten eines weiteren Mehrweghahnes 9 und Schließen eines Ventiles 13 durch die Pumpe 10-im Pulversammelgefäß 11 ein Unterdruck erzeugt. Durch Öffnen des Hahnes 6 in Richtung Pulversammelgefäß 11, bei gleichzeitiger Öffnung des Hahnes 2 nach außen, wird das Pulver aus dem Rohr 4 abgesaugt und im Behälter 11 gesammelt. Ein Filter 12 verhindert, daß Pulver in die Pumpe eindringt und diese verschmutzt. Mit einer einfachen Pulverfördereinrichtung, z.B. einer Schneckenpumpe 15, wird das Kunststoffpulver aus dem Pulversammelgefäß 11 in den Behälter 1 zurückbefördert. In die Rückführungsleitung 16 für das Kunststoffpulver ist ein Kühler 14 eingeschaltet, welcher zwischen Pulversammelgefäß 11 und Schneckenpumpe 15 angeordnet ist.In the drawing, 1 denotes the storage container for the plastic powder. Starting from this reservoir 1, a connecting line 3 is connected to the pipe 4 via a tap 2. The tube 4 is located in a heating furnace (not shown) and is brought to a temperature which is sufficient for frying the respective plastic powder. The tube 4 is usually passed through a device for applying an adhesion promoter, which is not shown, before it is inserted into the holders 5 and connected to the storage container for the plastic, for example initially by sandblasting, bright annealing, pickling or the like . Cleaned pipe is sprayed with the primer inside in this adhesion promoter station. The volatile constituents contained in the primer are vented in a known manner with compressed air and the tubes are then brought to a stoving temperature corresponding to the primer, for example to a temperature of about 200 to 300 ° C. After leaving the baking oven, not shown, the tubes are cooled to the sintering temperature of the plastic to be applied and are kept at this temperature during the coating, that is to say while they are inserted in the holders 5. A filter 7 is connected to the end of the tube 4 facing away from the storage container 1 via a short line and a multi-way valve 6. Via the vacuum vessel 8, the line leads to the outside via the gas-producing pump. The tube 4 can rotate in the holders 5 about its longitudinal axis, for which devices known per se, which are not shown in the drawing for the sake of clarity, are provided. The vessel 8 is first evacuated with the gas-producing pump. Through the opening of the multi-way valve 6 powder from the container 1 in fluidized form via the line 3 through the Multi-way valve 2 sucked into the pipe 4. The powder column comes to a standstill on the filter 7, while the carrier gas flows further into the container 8 and is finally discharged into the atmosphere by the pump 10. After a period of 30 to 60 seconds, depending on the desired layer thickness, part of the plastic has fritted on the inner wall. The tube 4 can rotate in the holders 5 about its longitudinal axis. During this time, a vacuum is generated in the powder collecting vessel 11 by switching over another reusable valve 9 and closing a valve 13 by the pump 10. By opening the tap 6 in the direction of the powder collecting vessel 11, while simultaneously opening the tap 2 to the outside, the powder is sucked out of the tube 4 and collected in the container 11. A filter 12 prevents powder from entering the pump and contaminating it. The plastic powder is conveyed back from the powder collecting vessel 11 into the container 1 with a simple powder conveying device, for example a screw pump 15. In the return line 16 for the plastic powder, a cooler 14 is connected, which is arranged between the powder collecting vessel 11 and the screw pump 15.

Das Kunststoffpulver kann in der erfindungsgemäßen Vorrichtung in Dichten von etwa 700 bis 1000 kg/m eingesetzt werden.The plastic powder can be used in the device according to the invention in densities of about 700 to 1000 kg / m.

Claims (10)

1. Verfahren zur Innenbeschichtung von Rohren mit Kunststoff, wobei in das gegebenenfalls um seine Achse rotierende Rohr Kunststoffpulver unter Vermittlung eines Trägergases eingesaugt wird und das Kunststoffpulver an die erhitzte Rohrwand angefrittet wird, worauf die nicht angefrittete Pulvermenge wieder abgesaugt und gegebenenfalls die angefrittete Kunststoffschicht durch weiteres Erwärmen geglättet wird und wobei gegebenenfalls vor Einbringen des Kunststoffpulvers ein Haftvermittler in das Rohr eingebracht wird, dadurch gekennzeichnet, daß das Trägergas nach Durchströmen des Rohres vom Kunststoffpulver durch Abfiltern getrennt und das Kunststoffpulver im Rohr während der für das Anfritten erforderlichen Zeit zurückgehalten wird.1.Procedure for the inner coating of pipes with plastic, whereby plastic powder is sucked into the pipe, which possibly rotates about its axis, by means of a carrier gas and the plastic powder is seared against the heated pipe wall, whereupon the amount of powder which has not been seared is suctioned off again and, if necessary, the fritted plastic layer by another Heating is smoothed and, if necessary, an adhesion promoter is introduced into the tube before introducing the plastic powder, characterized in that the carrier gas is separated from the plastic powder by filtering after flowing through the tube and the plastic powder is retained in the tube during the time required for frying. 2. Vorrichtung zur Durchführung des Verfahrens nach An-- spruch 1 mit einem dicht an einem Vorratsbehälter für Kunststoffpulver über eine Leitung verbundenen Anschluß für das zu beschichtende Rohr und einem weiteren Anschluß für das andere Ende des zu beschichtenden Rohres, dadurch gekennzeichnet, daß der weitere Anschluß (5) für das zu beschichtende Rohr (4) über ein Filter (7) mit der Saugseite einer gasfördernden Pumpe (10) in Verbindung steht.2.Device for carrying out the method according to claim 1 with a connection connected tightly to a storage container for plastic powder via a line for the pipe to be coated and a further connection for the other end of the pipe to be coated, characterized in that the further Connection (5) for the pipe (4) to be coated is connected via a filter (7) to the suction side of a gas-producing pump (10). 3. Vorrichtung nach Anspruch 2, dadurch gekennzeichnet, daß in die Saugleitung zwischen Filter (7) und Pumpe (10) ein evakuierbarer Behälter (8) eingeschaltet ist.3. Apparatus according to claim 2, characterized in that an evacuable container (8) is switched on in the suction line between the filter (7) and pump (10). 4. Vorrichtung nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß zwischen dem Anschluß (5) für das Rohr (4) und dem Filter (7) ein Wegeventil (6) angeordnet ist, welches in einer Stellung den Anschluß (5) für das Rohr (4) mit dem Filter (7) und in einer weiteren Stellung mit der Rückführungsleitung (16) in Verbindung setzt.4. Apparatus according to claim 2 or 3, characterized in that between the connection (5) for the tube (4) and the filter (7) a directional control valve (6) is arranged, which in one position the connection (5) for the Pipe (4) with the filter (7) and in a further position with the return line (16) in connection. 5. Vorrichtung nach Anspruch 4, dadurch gekennzeichnet, daß zwischen dem dem Anschluß (5) für das Rohr (4) nachgeschaltetem Wegeventil (6) und der Rückführungsleitung (16) ein Pulversammelgefäß (11) angeordnet ist.5. The device according to claim 4, characterized in that between the connection (5) for the tube (4) downstream directional valve (6) and the return line (16), a powder collection vessel (11) is arranged. 6. Vorrichtung nach einem der Ansprüche 2 bis 5, dadurch gekennzeichnet, daß die Saugseite der gasfördernden Pumpe (10) über ein Wegeventil (9) wahlweise mit dem Filter (7) oder unter Zwischenschaltung eines weiteren Filters (12) mit dem Pulversammelgefäß (11) in Verbindung setzbar ist.6. Device according to one of claims 2 to 5, characterized in that the suction side of the gas pump (10) via a directional valve (9) either with the filter (7) or with the interposition of a further filter (12) with the powder collecting vessel (11 ) can be connected. 7. Vorrichtung nach einem der Ansprüche 2 bis 6, dadurch gekennzeichnet, daß zwischen dem Vorratsbehälter (1) und dem Anschluß (5) für das Rohr (4) ein Wegeventil -(2) angeordnet ist, welches in einer Stellung den Anschluß (5) für das Rohr (4) mit dem Vorratsbehälter (1) und in einer weiteren Stellung mit der Atmosphäre in Verbindung setzt.7. Device according to one of claims 2 to 6, characterized in that between the reservoir (1) and the connection (5) for the tube (4) a directional control valve - (2) is arranged, which in one position the connection (5th ) for the pipe (4) with the storage container (1) and in a further position with the atmosphere. 8. Vorrichtung nach einem der Ansprüche 2 bis 7, dadurch gekennzeichnet, daß in die Rückführungsleitung (16) zwischen dem Pulversammelgefäß (11) und dem Vorratsbehälter (1) ein .Absperrventil (13) eingeschaltet ist.8. Device according to one of claims 2 to 7, characterized in that in the return line (16) between the powder collecting vessel (11) and the storage container (1). A shut-off valve (13) is switched on. 9. Vorrichtung nach einem der Ansprüche 2 bis 8, dadurch gekennzeichnet, daß der Vorratsbehälter (1) für das Kunststoffpulver dicht abschließbar ist, und daß die Rückführungsleitung (16) über einen Kühler (14) in diesen Vorratsbehälter (1) mündet.9. Device according to one of claims 2 to 8, characterized in that the storage container (1) for the plastic powder can be sealed, and that the return line (16) via a cooler (14) opens into this storage container (1). 10.Vorrichtung nach einem der Ansprüche 2 bis 9,.dadurch gekennzeichnet, daß in die Rückführungsleitung (16) zwischen dem Vorratsbehälter (1) und dem Rohr (4) eine Schneckenpumpe (15) eingeschaltet ist.10.Device according to one of claims 2 to 9, .d characterized in that in the return line (16) between the reservoir (1) and the tube (4), a screw pump (15) is switched on.
EP19800890027 1979-03-06 1980-03-03 Process for coating the inside of pipes with plastics material and apparatus for carrying out said process Expired EP0015894B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT169779A AT375295B (en) 1979-03-06 1979-03-06 METHOD AND DEVICE FOR THE INTERNAL COATING OF TUBES
AT1697/79 1979-03-06

Publications (2)

Publication Number Publication Date
EP0015894A1 true EP0015894A1 (en) 1980-09-17
EP0015894B1 EP0015894B1 (en) 1983-03-09

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EP19800890027 Expired EP0015894B1 (en) 1979-03-06 1980-03-03 Process for coating the inside of pipes with plastics material and apparatus for carrying out said process

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EP (1) EP0015894B1 (en)
AT (1) AT375295B (en)
CS (1) CS215049B2 (en)
DD (1) DD149315A5 (en)
DE (1) DE3062247D1 (en)
HU (1) HU180332B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992016310A1 (en) * 1991-03-25 1992-10-01 Alfa-Laval Thermal Ab Method of providing heat transfer plates with a layer of a surface protecting material

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1577794A1 (en) * 1962-10-10 1970-04-09 Heilker Johannes Josephus Method and device for lining a metal pipe with a synthetic resin layer
DE1652447A1 (en) * 1968-01-23 1971-03-18 Buettner Schilde Haas Ag Method and device for the internal coating of elongated hollow objects, in particular pipes, with thermoplastics
DE2052314B2 (en) * 1970-10-24 1972-05-25 METHOD OF COATING THE INSIDE OF METAL PIPES WITH PLASTICS
DE2228809A1 (en) * 1971-06-16 1973-01-04 Japan Provac Co Ltd PROCEDURE FOR COVERING THE INNER SURFACE OF STRAIGHT METAL PIPES AND SYSTEM FOR EXECUTING THE PROCESS
US3974306A (en) * 1972-10-06 1976-08-10 Kansai Paint Company, Ltd. Method for coating the inner surface of metal pipes
DE2724031A1 (en) * 1977-05-27 1978-12-14 Metallgesellschaft Ag Metallic tubes coated internally with plastics layer - using double walled lance with radial spigot to blow plastics at heated wall and remove excess

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1577794A1 (en) * 1962-10-10 1970-04-09 Heilker Johannes Josephus Method and device for lining a metal pipe with a synthetic resin layer
DE1652447A1 (en) * 1968-01-23 1971-03-18 Buettner Schilde Haas Ag Method and device for the internal coating of elongated hollow objects, in particular pipes, with thermoplastics
DE2052314B2 (en) * 1970-10-24 1972-05-25 METHOD OF COATING THE INSIDE OF METAL PIPES WITH PLASTICS
DE2228809A1 (en) * 1971-06-16 1973-01-04 Japan Provac Co Ltd PROCEDURE FOR COVERING THE INNER SURFACE OF STRAIGHT METAL PIPES AND SYSTEM FOR EXECUTING THE PROCESS
US3974306A (en) * 1972-10-06 1976-08-10 Kansai Paint Company, Ltd. Method for coating the inner surface of metal pipes
DE2724031A1 (en) * 1977-05-27 1978-12-14 Metallgesellschaft Ag Metallic tubes coated internally with plastics layer - using double walled lance with radial spigot to blow plastics at heated wall and remove excess

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1992016310A1 (en) * 1991-03-25 1992-10-01 Alfa-Laval Thermal Ab Method of providing heat transfer plates with a layer of a surface protecting material

Also Published As

Publication number Publication date
ATA169779A (en) 1983-12-15
AT375295B (en) 1984-07-25
EP0015894B1 (en) 1983-03-09
DE3062247D1 (en) 1983-04-14
CS215049B2 (en) 1982-06-25
DD149315A5 (en) 1981-07-08
HU180332B (en) 1983-02-28

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