DE3043246A1 - Device for painting interior of pipes - has spiralling air stream to spread spray along length of pipe - Google Patents

Abstract

The device for painting the inside of a pipe (2) has an air-blast atomiser (1) which is supplied with epoxy resin paint from tank (3) and hardener from tank (4). Compressed air is supplied from compressor (13). Additional air is fed via valve (16) and regulator (17) to tangential inlets (18) which set up a rapid spiral air flow pattern in the pipe. The paint is carried forward and deposited on the walls of the pipe. Excess paint leaves at the end of the pipe and can be drawn off by an exhaust device.

Description

Method and device for coating the inner surface

of a pipe The invention relates to a method and an apparatus for covering the inner surface of a water pipe by means of a spiral Air stream of sprayed paint mist.

Iron or vinyl chloride pipes are used in residential or office buildings as Water pipes or pipes used. Iron pipes rust within a few years. It is therefore advisable to remove the rust and the inner surface to prevent rust to provide the pipe with a coating.

However, the cleaning and the application of a coating are made difficult with already laid water pipes.

Installed pipes have numerous knees and branches. Of the The diameter of the pipes connected to the line is common at the coupling points different.

The inventor already has an effective method of coating the Developed inner surface of already laid water pipes. He developed a procedure for cleaning pipes by means of a strong air flow through the pipe sandblasting to remove rust or debris and another process for coating, in which the coating paint is blown by a strong stream of air in the pipe will.

In this process, the paint is sprayed out from a nozzle and blown into the pipe by the strong stream of air that has just been directed. As color can for example an epoxy resin paint can be used. The viscosity of the paint can be varied by changing the concentration of the solvent. Since the Paint is sprayed in the form of drops of liquid with a relatively large diameter, the spray distance is only a very short distance. Because the paint drops big and are heavy, they fall down at the beginning of the pipe and go back in the initial liquid state. The strong air current drives the color liquid on it forward in the pipe. The liquid is distributed in the pipe and coats the inner surface.

However, this coating process is not yet fully satisfactory. It is very time consuming. Air and paint consumption are too high.

The speed of a pipe being passed straight through a section of pipe Airflow is greatest in the center and lowest on the inner surfaces of the tube. The outer layer of the air flow, which has the lowest speed, drifts the color liquid on the floor surface forward.

The force exerted on the paint is merely a pushing force, the acts in a thin boundary layer between the air flow and the color liquid. Just one a very small area of the air flow therefore causes the coating process.

Most of the compressed air flows through the pipe for free.

To compensate for these disadvantages, the method requires a powerful one and a large compressor, which in turn consumes a lot of energy.

In addition, gravity has an adverse effect.

While there is a thick one on the lower inside of the pipe Paint layer forms, the paint layer on the inside of the pipe is due to gravity only very thin The thickness of the paint layer is uneven. On the lower inside an unnecessarily thick layer of paint must always form, because in fact the thickness must the layer of paint on the upper inside of the pipe must always be larger than a calculated one smallest possible layer thickness. The waste of color is too great.

The invention relates to a method and a device for Coating the inner surface of a tube in which the paint droplets are drawn by means of a spiral Air flow can be guided through the tube. With a spiral guide is with a Airflow with a smaller diameter to achieve a higher flow velocity. The tangential velocity Vt is irrelevant to the air flow. The airflow is only determined by the axial speed vl, since the air flow Q is # S Vl is defined, where # stands for the air density and S for the pipe cross-section. The paint in the form of liquid droplets is transported at a speed which is approximately proportional to the total speed Vo. The overall speed Vo is highest with a spiral air flow on the inner surface of the tube. Spiral airflow is therefore more effective for distribution in two ways of paint liquid in pipes as a straight air stream, at which the tangential velocity is practically zero.

A further feature of the invention is a method and an apparatus for coating the inner surface of a pipe, in which the paint liquid from an air stream is broken down into very fine color droplets at the speed of ultrasound. The from which have an extreme speed, namely supersonic speed Fine paint droplets generated by air flow are very stable and can be overcome hover in the air for a long time due to gravity.

Still another feature of the invention is a method and method Device for coating the inner surface of a pipe, in which the cross-section the air flow is significantly narrowed to its speed with the help of a throttle nozzle to increase Further features, details and advantages of the invention result from the following description of some preferred exemplary embodiments and based on the drawing.

1 shows a schematic diagram of the entire system an embodiment of the invention; Fig. 2 is enlarged and partially in section nebulization nozzle used in the first embodiment; 3 shows an enlarged Longitudinal section of a spiral ejector for mixing air and paint in another Execution; FIG. 4 shows a perspective illustration of the ejector and FIG. 5 shows a enlarged longitudinal section through a spiral ejector of a third embodiment.

According to Fig. 1 is at an opening of a relocated, previously to any A nebulization duo 1 attached to the cleaned water pipe. Tap and socket are removed. Both ends of the tube are open.

For the sake of simplicity, the water pipe 2 in Fig. 1 is straight Piece drawn. In fact, there can be multiple knees, bends, or branches exhibit.

Epoxy resin, for example, is used here as the coating liquid. The main solution A and the hardener solution B are in the A solution container 3 and in the B solution container 4.

Solution A and solution B flow through an A solution line 7 and a B solution line 8 in a mixing device 9. In the mixing device 9 the solutions A and B are mixed.

The mixture passes through a valve 10, a flow meter 11 and a Line 12 and is fed to the inflow opening of the nebulizer nozzle 1. In the nebulizer nozzle 1 is the color or the like. from the compressed air into one of small droplets of liquid existing fog.

Remaining compressed air is from the compressor 13 via a valve 16 and a regulator 17 is supplied to a scroll fan 18. The tangentially arranged by several Air flowing into the fan 18 forms a spiral shape in the fan High speed airflow.

The nebulizer nozzle 1 sprays the mixture that has been split into extremely fine particles into the spiral fan 18. The paint mist is created by the rapid spiral air flow set in strong rotation in the fan.

The spiral air flow causes the paint mist through the pipe 2 carried forward, hitting and adhering to its inner surface. Excess paint mist comes out at the other end of the pipe. With the help of a trigger excess paint can be peeled off there.

The nebulizer nozzle 1 according to FIG. 2 consists of an outer cylinder 20, a nozzle body 21 and an inner cylinder 22.

The inner cylinder 22 is arranged concentrically in the outer cylinder 20. The nozzle body 21 is attached to the front end of the inner cylinder 22. Outer Cylinder 20 and inner cylinder 22 are at the rear end as hexahedral bodies 23,24 designed so that wrenches or other tools can be applied can.

The rear end of the outer cylinder 20 has an internal screw thread on. The inner cylinder 22 is arranged in front of the hexahedral body 24 External thread 26 provided.

A ring 27 is seated in front of the screw thread 26.

The outer cylinder 20 and the inner cylinder 22 are screw-threaded 25 firmly connected. No air can escape through the external thread 26 and the ring 27. The hexagonal end piece 23 of the outer cylinder 20 is vertical an air inflow opening 28 let in.

There is therefore an air duct between the outer and inner cylinders 20, 22 29

The outside of the front part of the inner cylinder 22 has a External thread 30 on. Corresponding to this external thread 30 is at the rear end of the nozzle body 21 has an internal thread 31 attached. The inner cylinder 22 and the Nozzle bodies 21 are connected to one another by the internal thread 31 and the external thread 30 screwed.

The nozzle body 21, which tapers conically at the front and rear, has a bullet-like shape. In the outside 32 of the rear cone are in the longitudinal direction several air outlet channels embedded. This version has ten outlet channels Mistake; in other designs, however, a channel can be sufficient.

From the interior 34 of the nozzle body 21 are leading radially outward A plurality of paint outlet openings 35 are let in at right angles to the side surface.

The paint outlet openings 35 are exactly in front of the air discharge channels 33 arranged so that the compressed air breaks the paint into small drops of liquid.

The outside 36 of the front cone is provided with a step 37, so that wrenches can be used here.

The rear end of the inner cylinder 22 expands into one Inflow opening 38 which has an internal thread. It turns into a color channel 39 in cylinder 22.

The function of the nebulizer nozzle 1 is explained below: The compressed air (from 1 kg / cm2 to 7 kg / cm2 per measuring unit) is supplied through the air inlet opening 28 passed into the air duct 29.

The air flows through the narrow opening channels between the air discharge channels 33 and the outer slopes 40 exist.

Since the cross-sections of the opening channels are very narrow, they are formed High speed air currents. With increasing pressure in the air duct 29 increases the speed of the air currents increases. In general, however, the speed an air flow exiting through an opening must not be higher than the speed of sound, which is a function of temperature and pressure.

To the air flow from the air outlet grooves 33 at the speed of sound To allow leakage, the air pressure must be above a certain critical value. Theoretically, this limit is around 1.8 kg / cm2 absolute. In practice it has to Air pressure must be higher than 2 kg / cm2 due to frictional losses.

The air outlet grooves 33 can be funnel-shaped with a narrowest point in the middle and an extension at the outer end. In this In this case, the air flow in the air discharge chutes 33 assumes supersonic speed. At the narrowest point (the so-called "neck") the air flow reaches the speed of sound. The gutters widen again and the air suddenly expands, with the Density decreases and the speed due to the sharp decrease in air density increases. The air flow therefore emerges from the funnel-shaped ones at supersonic speed Discharge chutes 33, and an air pressure of over 1 kg / cm2 (per unit of measurement) is sufficient for generation from a flow of air at supersonic speed.

The nebulizer nozzle 1 according to FIG. 1 can effortlessly flow air flows at supersonic speeds produce. Supersonic speed has a Mach number between 0.8 and 1.

In general, the nebulizer nozzle can both air currents at the speed of sound, as well as those of supersonic speed.

At the same time, paint enters through the paint inflow opening 38 and flows through it the paint channel 39 to the interior 34. The paint is distributed and through the paint outlet openings 35 ejected.

The air flow described at the speed of sound or supersonic speed meets the flowing color almost at a right angle and creates strong colors there Shock waves.

In front of and behind the discontinuity surface of the shock wave are pressure, density and free energy radically different. The strong decrease in free energy leads to Splitting of the color into fine mist. The diameter of a drop of paint in the nebula lies between 20 # m and 30 #m. The drop of paint is five to ten times as small like the drop of paint produced by a conventional nebulizer nozzle.

The paint drops sprayed by the nebulizer nozzle 1 are so small and easy that they are almost unaffected by the action of gravity. The paint drops stay in the air for a long time.

The extremely low weight of the paint drops is an advantage.

the spiral air flow generated in the spiral fan 18 displaces the Color mist in rotational movements. The color mist now turns from the fast spiral Air flow carried forward in the tube.

Since the air flow is spirally guided, the total speed, of which the ability to transport drops of liquid over long distances, is dependent, can be increased without the air flow having to be increased.

The total speed, the axial speed and the tangential speed of the total air flow are denoted by Vo, Ve and Vt.

Vo is the vector sum of Ve and Vt. The total air flow is defined as # SVe, where stands for the density and S for the cross-section of the pipe 2.

In a spiral air flow is the tangential velocity Vt in the central axis almost equal to zero and on the inner surface due to the Viscosity greatest.

In order to keep the viscosity loss as low as possible, the Tangential velocity Vt except for a thin boundary layer on the inner surface approximately proportional to a radius R.

In a spiral air flow, the paint drops become for the most part carried by the most energetic area of the airflow.

Gravity does not affect the paint drops effectively, so the Tube 2 can be coated evenly. The difference between the thickness of the paint layer on the upper resp.

the lower inside of the tube is minimal as the centrifugal force is a lot stronger than gravity. Reduced with uniform thickness of the coating the color consumption increases considerably.

With the help of the spiral air flow, the drops of paint can be guided through the pipe much faster because the paint drops in the air stream float and do not immediately hit the inner surface. In the conventional Method used straight guided airflow hits the Color liquid on the inner surface of the pipe and is influenced by the small effect of the shear forces between Air and liquid propelled forward.

The force that drives the paint forward in the pipe is small because the Shear force is only weak by nature and just the one causing the shear force Area of the directly guided air flow whose part is the lowest in energy. The time saving This coating process is significant because it is the most energetic area of the spirally guided air flow carries most of the color droplets and the the force directly exerted on the drops of paint is always greater than the shear force is.

Fig. 3 shows a further embodiment of the invention. Pictured is a spiral ejector 41 which performs the functions of the nebulizer nozzle 1 and the spiral fan 18 of the first version combined.

The spiral ejector 41 consists of a cylindrical housing 42, a tangentially arranged air inflow opening 43, a paint supply channel 44, a Nozzle head 45 and a throttle cone 48. The liquid flows through the supply channel 44 and wira through radially arranged nozzles 46 of the nozzle head 45 into the cylindrical Blower 42 injected. Flows through the tangentially arranged air inflow opening 43 Compressed air and generates a spiral air flow in the cylindrical housing 42 of high speed. The throttle cone 48 is on one in front of the nozzle body 45 attached with a screw threaded rod 50 with screw nuts 49 attached.

The nozzle opening 51 between the throttle core 48 and the housing 42 is adjustable. The adjustable opening 51 throttles the air flow in the housing 42. With their help a steady flow of air can be maintained.

In the second embodiment, the air does not travel at the speed of sound pushed out. The paint drops generated by the air flow are therefore larger and heavier than that of the first run.

The throttle cone 48 directs the entire rotational energy into a narrow one Outside area, from which the drops of paint are also carried into the pipe. The broad one The interior of the spiral air flow is practically barely used for paint transport usable.

5 shows a section through another spiral ejector nozzle 60. This spiral nozzle 60 consists of a cylindrical housing 64, which is attached to the rear Wall is provided with a paint inlet opening 62, also from one on the side wall of the housing 61 tangentially arranged air inflow opening 63.

The liquid passes through the inlet opening 62 into an interior space 65 a. The compressed air flows into the interior space 65 and creates a spiral air flow. The color liquid is broken down into small drops by the spiral air flow equipped with free energy. The paint drops are in the tube from the spiral Airflow carried forward. The paint drops are not as light as those in the Generated nebulizer nozzle 1 of the first embodiment. The spiral ejector nozzle is for this simply constructed.

It is crucial that the invention is a fine drop of liquid carrying spiral air flow to coat the inner surface of pipes power. By means of a spiral air flow that overcomes the force of gravity apply a coating of uniform thickness. The consumption of time and fluids is less. Because the drops of paint come from the most energetic area of the air flow are worn, compressed air can also be saved.

Since the medium used to transport the paint is air, can with it even pipes with bends, knees or branches are lined evenly will.

In the present example, epoxy resin is used. However, it can any type of paint can be used in the invention: lacquer paint, vinyl resin paint, Melamine Resin Paint, Phthalic Acid Resin Paint, or Methyl Methacrylate Acid Paint. at Using these colors, only a paint tank is put in use, as they are not must be mixed together from two components before use.

The invention consists of a compressor in which compressed air is generated and is saved; also from one or more paint containers for receiving of color; also a spiral ejector nozzle, which is enriched with drops of paint expelling high-speed spiral airflow, ultimately from a paint feeder, which supplies the spiral ejector nozzle with paint. This nozzle consists of the first design from a nozzle body and a spiral fan.

Claims (4)

Claims 1. A method for coating the inner surface of a Tube, characterized in that a spiral which is enriched with drops of color Air flow is blown at high speed into the pipe to be coated (2). 2. Device for coating the inner surface of a pipe, marked by a compressed air generating and storing compressor (13), one or more Container (3, 4) for receiving paint or the like, also a spiral ejector nozzle (41, 60), which emits a spiral air stream enriched with drops of paint and finally a paint supply device which supplies the spiral ejector nozzle (41, 60) with paint. 3. Apparatus according to claim 2, characterized in that the spiral ejector nozzle (41,60) consists of a nebulizer nozzle (1), which with an air stream of sonic or supersonic speed produces fine drops of paint and a spiral fan consists of several tangentially arranged air outflow openings. 4. Apparatus according to claim 2, characterized in that the spiral ejector nozzle (41,60) a throttle cone to increase the speed of the air flow in the Has opening.