EP0069874B1 - Abrasive blasting method using air under pressure - Google Patents

Abrasive blasting method using air under pressure Download PDF

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Publication number
EP0069874B1
EP0069874B1 EP82105335A EP82105335A EP0069874B1 EP 0069874 B1 EP0069874 B1 EP 0069874B1 EP 82105335 A EP82105335 A EP 82105335A EP 82105335 A EP82105335 A EP 82105335A EP 0069874 B1 EP0069874 B1 EP 0069874B1
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EP
European Patent Office
Prior art keywords
air
jet
additional
blasting
pressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP82105335A
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German (de)
French (fr)
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EP0069874A2 (en
EP0069874A3 (en
Inventor
Karl Christian Glaeser
Gerhard Buhr
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Ernst Peiniger Unternehmen fur Bautenschutz GmbH
Ernst Peiniger GmbH Unternehmen fur Bautenschutz
Original Assignee
Ernst Peiniger Unternehmen fur Bautenschutz GmbH
Ernst Peiniger GmbH Unternehmen fur Bautenschutz
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Priority to AT82105335T priority Critical patent/ATE12196T1/en
Publication of EP0069874A2 publication Critical patent/EP0069874A2/en
Publication of EP0069874A3 publication Critical patent/EP0069874A3/en
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Publication of EP0069874B1 publication Critical patent/EP0069874B1/en
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Classifications

    • 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
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C7/00—Equipment for feeding abrasive material; Controlling the flowability, constitution, or other physical characteristics of abrasive blasts
    • B24C7/0084—Equipment for feeding abrasive material; Controlling the flowability, constitution, or other physical characteristics of abrasive blasts the abrasive material being fed in a mixture of liquid and gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C11/00—Selection of abrasive materials or additives for abrasive blasts
    • B24C11/005—Selection of abrasive materials or additives for abrasive blasts of additives, e.g. anti-corrosive or disinfecting agents in solid, liquid or gaseous form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C7/00—Equipment for feeding abrasive material; Controlling the flowability, constitution, or other physical characteristics of abrasive blasts
    • B24C7/0046—Equipment for feeding abrasive material; Controlling the flowability, constitution, or other physical characteristics of abrasive blasts the abrasive material being fed in a gaseous carrier

Definitions

  • the invention relates to a method for compressed air blasting, in which a granular abrasive is introduced into a carrier air stream and conveyed by the carrier air stream, accelerated and blown against a surface to be treated, and a supplementary air stream loaded with a liquid additive wetting the grains of the blasting agent, in particular water is added with the air stream loaded with the blasting agent, in particular injected into the air stream loaded with the blasting agent.
  • a method for compressed air blasting in which a granular abrasive is introduced into a carrier air stream and conveyed by the carrier air stream, accelerated and blown against a surface to be treated, and a supplementary air stream loaded with a liquid additive wetting the grains of the blasting agent, in particular water is added with the air stream loaded with the blasting agent, in particular injected into the air stream loaded with the blasting agent.
  • wet blasting In the known method for compressed air blasting described above, so-called wet blasting is sought; the individual grains of the blasting medium should be coated with the additive in such a way that the dust which develops when it hits the surface to be treated due to bursting grains of the blasting medium is bound.
  • the aim of the known process is thus a process formerly known as sandblasting and now often known as free blasting, which is neither dry blasting nor wet blasting due to the coating of the grains of the blasting medium with the additive, but rather is to be found in the intermediate area between the two processes.
  • the addition of the additive, in particular water, is carried out in such a way that, on the one hand, the coating of the individual grains of the blasting medium has practically evaporated after impact, so that no additive runs off, but on the other hand the low coating of the grains of the blasting medium is sufficient to prevent dust formation largely suppressed, so that contributes to occupational safety because the risk of the typical occupational disease dust lung is significantly reduced.
  • the known method is characterized by a low water consumption and can therefore be used like the known dry blasting - sandblasting with dry sand - because discharge devices for water or the like are not required.
  • the object of the invention is therefore to design and further develop the known method in such a way that, with the lowest consumption of liquid additive, the most uniform and uniform moistening of all the grains of the blasting agent in the entire jet is achieved.
  • a precisely metered coating of each individual abrasive grain, regardless of its location in the air flow, is aimed for.
  • the method according to the invention in which this object is achieved, is initially characterized in that the back pressure of the additional air flow in the injection region is approximately one and a half to two and a half times, preferably twice as high as the back pressure of the carrying air flow.
  • the above-mentioned dynamic pressure difference between the additional air flow and the air flow ensures that the liquid additive penetrates deep enough into the air flow on the one hand, but on the other hand does not shoot through the air flow and is not only reflected on the inner wall of the blasting device used.
  • a good atomization of the liquid additive is achieved in the specified parameter range; the desired low water consumption is achieved.
  • the dust binding proves to be very cheap.
  • the total pressure of a flowing medium is made up of the static pressure and the dynamic pressure.
  • the back pressure is known to be the measure of the kinetic energy of the flowing medium, i.e. a direct measure of the flow velocity.
  • sufficient mixing of the air flow and the additional air flow is achieved, which leads to the desired takeover of the liquid additive by the grains of the blasting medium.
  • the focus has been on the dynamic pressures and thus indirectly on the speeds of the air flow and the additional air flow, but not on the actual speeds of the grains of the abrasive or the liquid additive.
  • these speeds are always below the speed of the carrying air flow or additional air flow carrying them, so that the desired mixing results.
  • the mass of abrasive supplied to the injection area in the time unit is approximately 1.4 to 2.5 times, in particular 1.7 to 2.2 times, the mass supplied to the injection area in the time unit Air corresponds to.
  • the mass of additive, in particular water, supplied to the injection area in the time unit corresponds to approximately 2 o to 3 o, preferably d 6, of the mass of carrier air supplied to the injection area in the time unit.
  • This mass of additive is sufficient, on the one hand, to be able to moisten the grains of the abrasive sufficiently in the entire cross-section of the air flow, but on the other hand it is not so high that excess, liquid additive is produced, which is either deposited in the blasting device or on the surface to be treated and must be dissipated.
  • the consumption of liquid additive for example water, remains limited.
  • the moistening of the grains of the blasting agent is improved by an additional relative movement between the grains of the blasting agent and the finely divided additive. This can be done by eccentrically introducing the air flow into the additional air flow; the grains of the blasting medium can be set in rotary movements, in particular in helical movements, or can also undergo their own rotation.
  • a device as described in DE-A No. 2724318 is suitable for carrying out the method described above.
  • the disclosure content of this document is expressly made the disclosure content of the present patent application.
  • the grains of the blasting medium are still slow and therefore only move a short distance during the time required for moistening. This enables even moistening to be achieved.
  • the suction effect in the smallest nozzle cross-section is not necessary anyway, because the additional air flow is fed with excess pressure.
  • the dynamic pressure of the additional air flow is typically in the range from 10 to 30 bar. Satisfactory results were achieved with these pressure values.
  • blasting media can only be introduced into a nozzle area if there is at the same time an additional air stream sufficiently loaded with additive.
  • Even in the event of operating errors it is not possible to work without adding the liquid additive, in particular, therefore, to work with dry abrasive.
  • the occupational safety achieved by wet blasting is always set and cannot be switched off due to operating errors.
  • the forced coupling also ensures that the additional air flow is sufficiently loaded with the liquid additive in order to be able to adequately bind the accumulated dust quantities.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Nozzles (AREA)
  • Sorption Type Refrigeration Machines (AREA)
  • Jet Pumps And Other Pumps (AREA)

Abstract

For sand blasting a stream of a suspension of a carrier gas and solid particles under superatmospheric pressure is restricted so that it is accelerated, and a liquid-carrying additive gas is mixed with the stream to moisten the particles. The additive gas is introduced into the stream at a pressure greater than the pressure of the stream at the location by between 1.5 and 2.5 times. Normally the additive-gas pressure is about twice the carrier-gas pressure, that is the additive gas is normally introduced at a pressure of between about 10 bar and 30 bar. This high-pressure introduction ensures that the additive gas enters well into the carrier-gas stream so that the liquid carried by the additive gas contacts and wets the solids carried by the carrier gas without just passing through it and wetting the inside of the sand-blast mix nozzle. The additive gas is introduced into the stream in a unit of time at a rate sufficient to introduce into the stream a quantity of the liquid equal to between about one-twentieth to one-thirtieth, preferably one-twenty-fifth, the mass of the particles passing the location during the unit of time.

Description

Die Erfindung betrifft ein Verfahren zum Druckluftstrahlen, wobei ein körniges Strahlmittel in einen Tragluftstrom eingebracht und durch den Tragluftstrom gefördert, beschleunigt und gegen eine zu behandelnde Oberfläche geblasen wird und ein mit einem flüssigen, die Körner des Strahlmittels benetzenden Zusatzstoff, insbesondere Wasser, beladener Zusatzluftstrom dem mit dem Strahlmittel beladenen Tragluftstrom zugegeben wird, insbesondere in den mit dem Strahlmittel beladenen Tragluftstrom injiziert wird. Ein solches Verfahren ist mit der DE-A Nr. 2724318 bekannt geworden.The invention relates to a method for compressed air blasting, in which a granular abrasive is introduced into a carrier air stream and conveyed by the carrier air stream, accelerated and blown against a surface to be treated, and a supplementary air stream loaded with a liquid additive wetting the grains of the blasting agent, in particular water is added with the air stream loaded with the blasting agent, in particular injected into the air stream loaded with the blasting agent. Such a method is known from DE-A No. 2724318.

Bei dem zuvor beschriebenen bekannten Verfahren zum Druckluftstrahlen wird ein sogenanntes Feuchtstrahlen angestrebt; die einzelnen Körner des Strahlmittels sollen mit dem Zusatzstoff so umhüllt werden, dass der beim Auftreffen auf die zu behandelnde Oberfläche aufgrund zerplatzender Körner des Strahlmittels sich entwickelnde Staub gebunden wird. Abgezielt wird somit bei dem bekannten Verfahren auf ein früher als Sandstrahlen und heute häufig als Freistrahlen bezeichnetes Verfahren, das aufgrund der Umhüllung der Körner des Strahlmittels mit dem Zusatzstoff weder ein Trockenstrahlen noch ein Nassstrahlen ist, sondern vielmehr im Zwischenbereich zwischen beiden Verfahren anzusiedeln ist.In the known method for compressed air blasting described above, so-called wet blasting is sought; the individual grains of the blasting medium should be coated with the additive in such a way that the dust which develops when it hits the surface to be treated due to bursting grains of the blasting medium is bound. The aim of the known process is thus a process formerly known as sandblasting and now often known as free blasting, which is neither dry blasting nor wet blasting due to the coating of the grains of the blasting medium with the additive, but rather is to be found in the intermediate area between the two processes.

Die Zugabe des Zusatzstoffes, insbesondere Wasser, erfolgt dabei so, dass einerseits die Umhüllung der einzelnen Körner des Strahlmittels nach dem Auftreffen praktisch schon verdunstet ist, so dass kein Zusatzstoff abläuft, dass andererseits aber die geringe Umhüllung der Körner des Strahlmittels ausreicht, um eine Staubbildung weitgehend zu unterdrücken, so dass zum Arbeitsschutz beigetragen wird, weil die Gefahr der typischen Berufskrankheit Staublunge deutlich verringert ist. Das bekannte Verfahren zeichnet sich durch einen geringen Wasserverbrauch aus und lässt sich somit wie das bekannte Trockenstrahlen - Sandstrahlen mit trockenem Sand - einsetzen, weil Abführeinrichtungen für anfallendes Wasser od. dgl. nicht erforderlich sind.The addition of the additive, in particular water, is carried out in such a way that, on the one hand, the coating of the individual grains of the blasting medium has practically evaporated after impact, so that no additive runs off, but on the other hand the low coating of the grains of the blasting medium is sufficient to prevent dust formation largely suppressed, so that contributes to occupational safety because the risk of the typical occupational disease dust lung is significantly reduced. The known method is characterized by a low water consumption and can therefore be used like the known dry blasting - sandblasting with dry sand - because discharge devices for water or the like are not required.

Bei der praktischen Durchführung des zuvor beschriebenen bekannten Verfahrens hat sich gezeigt, dass eine gleichmässige Anfeuchtung aller Körner des Strahlmittels im austretenden Strahl nicht immer mit Sicherheit vorliegt. Bei Versuchen haben sich häufig die im Mantelbereich des austretenden Strahls befindlichen Körner als ausreichend angefeuchtet, die innen im Strahl liegenden Körner jedoch als viel zu trocken gezeigt, so dass diese Körner beim Auftreffen auf die zu behandelnde Oberfläche unerwünscht viel Staub hervorriefen. Im übrigen hat sich bei anderen Versuchen gezeigt, dass sich der flüssige Zusatzstoff an den Innenwandungen des benutzten Strahlgeräts niederschlug, also nicht im erwünschten Umfang von den Körnern des Strahlmittels aufgenommen wurde.In the practical implementation of the known method described above, it has been shown that a uniform moistening of all the grains of the blasting medium in the emerging jet is not always certain. In experiments, the grains located in the jacket area of the emerging jet have often been moistened as sufficient, but the grains lying inside in the jet have been shown to be too dry, so that these grains undesirably caused a lot of dust when they hit the surface to be treated. Furthermore, it has been shown in other experiments that the liquid additive was deposited on the inner walls of the blasting device used, ie was not absorbed to the desired extent by the grains of the blasting agent.

Aufgabe der Erfindung ist daher, das bekannte Verfahren dahingehend auszugestalten und weiterzubilden, dass bei geringstem Verbrauch an flüssigem Zusatzstoff eine möglichst gleichartige und gleichmässige Anfeuchtung aller Körner des Strahlmittels im gesamten Strahl erreicht wird. Anders ausgedrückt wird eine genau dosierte Umhüllung jedes einzelnen Strahlmittelkorns, unabhängig von seinem Ort im Tragluftstrom, angestrebt.The object of the invention is therefore to design and further develop the known method in such a way that, with the lowest consumption of liquid additive, the most uniform and uniform moistening of all the grains of the blasting agent in the entire jet is achieved. In other words, a precisely metered coating of each individual abrasive grain, regardless of its location in the air flow, is aimed for.

Das erfindungsgemässe Verfahren, bei dem diese Aufgabe gelöst ist, ist zunächst dadurch gekennzeichnet, dass im Injektionsbereich der Staudruck des Zusatzluftstroms etwa eineinhalbmal bis zweieinhalbmal, vorzugsweise zweimal so hoch ist wie der Staudruck des Tragluftstroms. Der zuvor angegebene Staudruckunterschied zwischen dem Zusatzluftstrom und dem Traglufstrom gewährleistet, dass der flüssige Zusatzstoff einerseits tief genug in den Tragluftstrom eindringt, andererseits aber den Tragluftstrom nicht durchschiesst und sich nicht lediglich an der Innenwand des verwendeten Strahlgerätes niederschlägt. Im angegebenen Parameterbereich wird eine gute Zerstäubung des flüssigen Zusatzstoffes erzielt; es stellt sich der erwünschte geringe Wasserverbrauch ein. Dabei erweist sich die Staubbindung als sehr günstig.The method according to the invention, in which this object is achieved, is initially characterized in that the back pressure of the additional air flow in the injection region is approximately one and a half to two and a half times, preferably twice as high as the back pressure of the carrying air flow. The above-mentioned dynamic pressure difference between the additional air flow and the air flow ensures that the liquid additive penetrates deep enough into the air flow on the one hand, but on the other hand does not shoot through the air flow and is not only reflected on the inner wall of the blasting device used. A good atomization of the liquid additive is achieved in the specified parameter range; the desired low water consumption is achieved. The dust binding proves to be very cheap.

Nach der Bernoulli-Gleichung setzt sich der Gesamtdruck eines strömenden Mediums zusammen aus dem statischen Druck und dem Staudruck. Der Staudruck ist bekanntlich das Mass für die kinetische Energie des strömenden Mediums, also ein direktes Mass für die Strömungsgeschwindigkeit. Bei den angegebenen Staudruckverhältnissen wird eine ausreichende Durchmischung von Tragluftstrom und Zusatzluftstrom erreicht, die zur gewünschten Übernahme des flüssigen Zusatzstoffes durch die Körner des Strahlmittels führt.According to the Bernoulli equation, the total pressure of a flowing medium is made up of the static pressure and the dynamic pressure. The back pressure is known to be the measure of the kinetic energy of the flowing medium, i.e. a direct measure of the flow velocity. At the specified dynamic pressure ratios, sufficient mixing of the air flow and the additional air flow is achieved, which leads to the desired takeover of the liquid additive by the grains of the blasting medium.

Abgestellt wurde bislang auf die Staudrücke und somit indirekt auf die Geschwindigkeiten von Tragluftstrom und Zusatzluftstrom, nicht aber auf die tatsächlichen Geschwindigkeiten der Körner des Strahlmittels bzw. des flüssigen Zusatzstoffes. Diese Geschwindigkeiten liegen jedoch stets unterhalb der Geschwindigkeit des sie tragenden Tragluftstroms bzw. Zusatzluftstroms, so dass sich die gewünschte Durchmischung ergibt. Dabei ist es jedoch besonders vorteilhaft, wenn die in der Zeiteinheit dem Injektionsbereich zugeführte Masse an Strahlmittel etwa dem 1,4- bis 2,5-, insbesondere dem 1,7- bis 2,2fachen, der in der Zeiteinheit dem Injektionsbereich zugeführten Masse an Tragluft entspricht. Bei diesen Massenverhältnissen wird unter Berücksichtigung der angegebenen Staudruckverhältnisse eine optimale Durchmischung beider Luftströme erreicht; weder quetscht ein Luftstrom den anderen ab, noch ist die im Zusatzluftstrom zugeführte Luftmenge so gross, dass sie die Beladung des austretenden Strahls an Strahlmittel und damit die Fähigkeit dieses Strahls, eine Oberfläche effektiv zu behandeln, entscheidend verringert. Weiterhin wird die in . Flugrichtung der Körner des Strahlmittels gemessene Länge des Injektionsbereiches in vernünftigen Grenzen gehalten, falls der Winkel zwischen dem Tragluftstrom und dem Zusatzluftstrom nicht zu klein gewählt wird. Relativ kurze Injektionsbereiche haben den Vorteil, dass die verwendeten Strahlgeräte nicht zu lang werden.So far, the focus has been on the dynamic pressures and thus indirectly on the speeds of the air flow and the additional air flow, but not on the actual speeds of the grains of the abrasive or the liquid additive. However, these speeds are always below the speed of the carrying air flow or additional air flow carrying them, so that the desired mixing results. In this case, however, it is particularly advantageous if the mass of abrasive supplied to the injection area in the time unit is approximately 1.4 to 2.5 times, in particular 1.7 to 2.2 times, the mass supplied to the injection area in the time unit Air corresponds to. With these mass ratios, optimal mixing of both air streams is achieved, taking into account the specified dynamic pressure ratios; neither does one air flow squeeze the other out, nor is the amount of air supplied in the additional air flow so large that it significantly reduces the loading of the emerging jet of abrasive and thus the ability of this jet to effectively treat a surface. Furthermore, the in. Direction of flight of the grains of the blasting medium measured length of the injection area kept within reasonable limits, if the angle between the carrier air flow and the additional air flow is not chosen too small. Relatively short injection area rich have the advantage that the blasting equipment used does not become too long.

Unter den zuvor angegebenen Bedingungen hat es sich als optimal herausgestellt, wenn die in der Zeiteinheit dem Injektionsbereich zugeführte Masse an Zusatzstoff, also insbesondere Wasser, etwa 2o bis 3o vorzugsweise d6 der in der Zeiteinheit dem Injektionsbereich zugeführten Masse an Tragluft entspricht. Diese Masse an Zusatzstoff reicht einerseits aus, um im gesamten Querschnitt des Tragluftstroms die Körner des Strahlmittels ausreichend anfeuchten zu können, ist andererseits aber nicht so hoch, dass überschüssiger, flüssiger Zusatzstoff anfällt, der sich entweder im Strahlgerät oder auf der zu behandelnden Oberfläche niederschlägt und abgeführt werden muss. Somit bleibt der Verbrauch an flüssigem Zusatzstoff, z.B. an Wasser, wie angestrebt, begrenzt.Under the conditions specified above, it has been found to be optimal if the mass of additive, in particular water, supplied to the injection area in the time unit corresponds to approximately 2 o to 3 o, preferably d 6, of the mass of carrier air supplied to the injection area in the time unit. This mass of additive is sufficient, on the one hand, to be able to moisten the grains of the abrasive sufficiently in the entire cross-section of the air flow, but on the other hand it is not so high that excess, liquid additive is produced, which is either deposited in the blasting device or on the surface to be treated and must be dissipated. As a result, the consumption of liquid additive, for example water, remains limited.

Um die Körner des Strahlmittels in der gewünschten Weise, also möglichst dünn und ringsum auf ihrer gesamten Oberfläche anfeuchten zu können, empfiehlt es sich, je nach dem Werkstoff des Strahlmittels, die einzelnen Körner vor der Zugabe des flüssigen Zusatzstoffes mit einem Benetzungsmittel, insbesondere einem hydrophilen Material, zu überziehen. Weiterhin wird die Anfeuchtung der Körner des Strahlmittels durch eine zusätzliche Relativbewegung zwischen den Körnern des Strahlmittels und dem feinverteilten Zusatzstoff verbessert. Dies kann durch aussermittiges Einleiten des Tragluftstroms in den Zusatzluftstrom erfolgen; die Körner des Strahlmittels können in Drehbewegungen, insbesondere in schraubenlinienförmig verlaufende Bewegungen versetzt werden oder auch eine Eigendrehung erhalten. Durch diese Relativbewegungen wird erreicht, dass die gesamte Oberfläche jedes einzelnen Korns des Strahlmittels erreicht wird, obwohl die Zusammenführung von Tragluftstrom und Zusatzluftstrom zwangsläufig in einem gewissen Winkel, zumindest einem Winkelbereich erfolgt und aufgrund dieser Zusammenführung lediglich eine teilweise Benetzung der einzelnen Körner zu erwarten ist.In order to be able to moisten the grains of the blasting medium in the desired way, i.e. as thinly as possible and all around on its entire surface, it is advisable, depending on the material of the blasting medium, to add a wetting agent, especially a hydrophilic one, to the individual grains before adding the liquid additive Material to coat. Furthermore, the moistening of the grains of the blasting agent is improved by an additional relative movement between the grains of the blasting agent and the finely divided additive. This can be done by eccentrically introducing the air flow into the additional air flow; the grains of the blasting medium can be set in rotary movements, in particular in helical movements, or can also undergo their own rotation. Through these relative movements it is achieved that the entire surface of each individual grain of the abrasive is reached, although the combination of the carrier air flow and the additional air flow necessarily takes place at a certain angle, at least one angular range, and due to this combination only partial wetting of the individual grains is to be expected.

Zur Durchführung des oben beschriebenen Verfahrens eignet sich eine Vorrichtung, wie sie in der DE-A Nr. 2724318 beschrieben ist. Der Offenbarungsgehalt dieser Druckschrift wird ausdrücklich zum Offenbarungsgehalt der hier vorliegenden Patentanmeldung gemacht. In Abänderung des bekannten Strahlgeräts wird jedoch zusätzlich vorgeschlagen, die Injektionskanäle für den mit dem flüssigen Zusatzstoff beladenen Zusatzluftstrom nicht im Bereich der Engstelle der VenturiDüse münden zulassen, sondern vielmehr - in Flugrichtung der Körner des Strahlmittels gesehen -vor dieser Engstelle anzuordnen. Vor dem engsten Düsenquerschnitt haben die Körner des Strahlmittels noch eine geringe Geschwindigkeit und bewegen sich deshalb während der für das Anfeuchten benötigten Zeit nur auf einer kurzen Strecke. Dadurch kann eine gleichmässige Anfeuchtung erreicht werden. Die Ansaugwirkung im geringsten Düsenquerschnitt ist ohnehin nicht notwendig, weil der Zusatzluftstrom mit Überdruck eingespeist wird.A device as described in DE-A No. 2724318 is suitable for carrying out the method described above. The disclosure content of this document is expressly made the disclosure content of the present patent application. In a modification of the known blasting device, however, it is additionally proposed not to allow the injection channels for the additional air stream loaded with the liquid additive to open out in the area of the constriction of the Venturi nozzle, but rather - in the direction of flight of the grains of the blasting agent - to be arranged in front of this constriction. Before the narrowest cross-section of the nozzle, the grains of the blasting medium are still slow and therefore only move a short distance during the time required for moistening. This enables even moistening to be achieved. The suction effect in the smallest nozzle cross-section is not necessary anyway, because the additional air flow is fed with excess pressure.

Der Staudruck des Zusatzluftstroms liegt typischerweise im Bereich von 10 bis 30 bar. Mit diesen Straudruckwerten wurden zufriedenstellende Ergebnisse erzielt. Schliesslich ist es bei dem erfindungsgemässen Verfahren noch vorteilhaft, die Zugabe von Strahlmittel mit der Zugabe des mit dem Zusatzstoff beladenen Zusatzluftstroms zwangszukoppeln. Dadurch kann nur dann Strahlmittel in einen Düsenbereich eingeleitet werden, wenn zugleich ein ausreichend mit Zusatzstoff beladener Zusatzluftstrom vorhanden ist. Auch bei Bedienungsfehlern ist es nicht möglich, ohne Zugabe des flüssigen Zusatzstoffs zu arbeiten, insbesondere also mit trockenem Strahlmittel zu arbeiten. Der durch das Feuchtstrahlen erzielte Arbeitsschutz stellt sich also stets ein und ist auch durch Bedienungsfehler nicht auszuschalten. Dabei sorgt die Zwangskopplung zudem für eine ausreichende Beladung des Zusatzluftstroms mit dem flüssigen Zusatzstoff, um die anfallenden Staubmengen stets ausreichend binden zu können.The dynamic pressure of the additional air flow is typically in the range from 10 to 30 bar. Satisfactory results were achieved with these pressure values. Finally, in the method according to the invention, it is also advantageous to forcibly couple the addition of blasting agent with the addition of the additional air stream loaded with the additive. As a result, blasting media can only be introduced into a nozzle area if there is at the same time an additional air stream sufficiently loaded with additive. Even in the event of operating errors, it is not possible to work without adding the liquid additive, in particular, therefore, to work with dry abrasive. The occupational safety achieved by wet blasting is always set and cannot be switched off due to operating errors. The forced coupling also ensures that the additional air flow is sufficiently loaded with the liquid additive in order to be able to adequately bind the accumulated dust quantities.

Claims (9)

1. A process for blowing a jet of compressed air, in which a granular blasting medium is introduced into a conveyor jet of air, carried and accelerated by the conveyor jet of air, and blasted against a surface to be treated, and an additional jet of air loaded with an additional liquid material, particularly water, that wets the grains of the blasting medium is added to the conveyor jet of air loaded with the blasting medium, and especially is injected into the conveyor jet of air loaded with the blasting medium, characterized in that in the injection region the pressure of the additional jet of air is some one and a half to two and a half times, preferably twice, as great as that of the conveyor jet of air.
2. A process according to Claim 1, characterized in that the weight of blasting medium supplied per unit of time into the injection region is some 1.4 to 2.5, especially 1.7 to 2.2 times, that of the weight of conveying air supplied into the injection region in the same unit of time.
3. A process according to Claim 1 or 2, characterized in that the weight of additional material supplied per unit of time into the injection region is some 210 to 30, preferably that of the weight of conveying air supplied into the injection region in the same unit of time.
4. A process according to one of Claims 1 to 3, characterized in that before adding the additional material the granular blasting material is coated with a humidifying medium, e.g. a water-attracting substance.
5. A process according to one of Claims 1 to 4, characterized in that the pressure of the additional jet of air is of the order of 10 to 30 bar.
6. A process according to one of Claims 1 to 5, characterized in that the supply of blasting material is compulsorily linked to the supply of the additional jet of air loaded with the additional material.
7. A process according to one of Claims 1 to 6, characterized in that the additional jet of air loaded with additional material is supplied into the conveyor jet of air off-centre to the conveyor jet of air.
8. A process according to one of Claims 1 to 7, characterized in that the conveyor jet of air loaded with the blasting medium is provided with a rotary movement around its direction of motion when introduced into the injection region.
9. A process according to one of Claims 1 to 8, characterized in that the injection of the additional jet of air loaded with the additional material takes place before a nozzle constriction, as seen in the direction of movement of the conveyor jet of air.
EP82105335A 1981-07-09 1982-06-18 Abrasive blasting method using air under pressure Expired EP0069874B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82105335T ATE12196T1 (en) 1981-07-09 1982-06-18 PROCESS FOR COMPRESSED AIR BLASTING.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3127035 1981-07-09
DE19813127035 DE3127035A1 (en) 1981-07-09 1981-07-09 "PROCESS FOR AIR RADIATION"

Publications (3)

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EP0069874A2 EP0069874A2 (en) 1983-01-19
EP0069874A3 EP0069874A3 (en) 1983-04-13
EP0069874B1 true EP0069874B1 (en) 1985-03-20

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EP82105335A Expired EP0069874B1 (en) 1981-07-09 1982-06-18 Abrasive blasting method using air under pressure

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US (1) US4802312A (en)
EP (1) EP0069874B1 (en)
JP (1) JPS5871065A (en)
KR (1) KR840000284A (en)
AT (1) ATE12196T1 (en)
DE (2) DE3127035A1 (en)
GR (1) GR76183B (en)
PT (1) PT75183B (en)

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Also Published As

Publication number Publication date
KR840000284A (en) 1984-02-18
PT75183A (en) 1982-08-01
JPS5871065A (en) 1983-04-27
US4802312A (en) 1989-02-07
DE3262640D1 (en) 1985-04-25
GR76183B (en) 1984-08-03
DE3127035A1 (en) 1983-01-27
PT75183B (en) 1984-05-28
EP0069874A2 (en) 1983-01-19
EP0069874A3 (en) 1983-04-13
ATE12196T1 (en) 1985-04-15

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