DE3043246C2 - Method and apparatus for coating the inner surface of a pipe - Google Patents

Description

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The invention relates to a method for coating the inner surface of a pipe ^{by! L} passing a pipe end on a blown mixture of air and ink droplets and an apparatus for performing this method.

Iron or vinyl chloride pipes are used in residential or Office buildings as water pipes or pipes ■ "' used. Iron pipes rust inside) years old. It is therefore advisable to remove the rust and to Rust prevention to provide the inner surface of the pipe with a coating.

The cleaning and the application of a coating, however, takes place in the case of water pipes that have already been laid difficult. Installed pipes have numerous knees and branches. The diameter of the pipe connected pipes is often different at the coupling points.

In the case of the method described at the beginning, which goes back to an older proposal by the applicant Type is, for example, an epoxy resin paint, the viscosity of which changes by changing the concentration of the solvent can vary, sprayed from a nozzle and from the straight directed strong Air flow blown into the tube. As the color in the form of liquid droplets of relatively large diameter is sprayed, the spray distance is only a relatively short distance. Because the paint drops big and are heavy, they fall down at the beginning of the pipe and return to their initial liquid state above. The strong air flow then drives the paint liquid forward in the pipe. The liquid is distributed in the pipe and covers the inner surface. This coating process, which is right in practice has proven to work well, but has the disadvantage that on the one hand it is very time-consuming because it is quite long

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fa5 takes until such a layer of paint through longer pipes has moved through it with several bends In addition, the air and especially the Color consumption with this process is quite high.

A lower paint consumption when coating the inner surface of pipes can be achieved with a Achieve arrangement, as in the German OiTenlegungsschrift 19 41 552 is provided. However, this method has the disadvantage that the pipe at the fixed nozzle arrangement must be moved past, which has the consequence. that the pipe is along a The slot must be open during the coating, since otherwise this bypass transport will not take place at all can be done. But this in turn has the consequence that existing pipe systems after this process at all cannot be lined afterwards.

Correspondingly, the same limitation also applies to one in connection with a cement coating apparatus prescribed device according to the German Offenlegungsschrift 27 09 258, in which the The nozzle head is moved through the pipe. Also this movement of the nozzle head through the pipe prevents use on curved pipes.

The invention is therefore based on the object of designing the method of the type mentioned at the outset in such a way that that a uniform coating of arbitrarily shaped and curved pipes can be achieved quickly and with little air and paint consumption.

To solve this problem, the invention provides that the air to generate a is blown in high-energy spiral air flow tangential in particular in the outer circumferential zone.

The invention is based on the knowledge. that the speed of one through a pipe section Straight air flow is greatest in the middle and lowest on the inner surfaces of the tube. The outer layer of the airflow, which has the lowest speed, drifts at the entrance method described the color liquid on the floor surface forward. The one exerted on the color Force is just a pushing force that exists in a thin boundary layer between the airflow and the paint liquid works. Therefore, only a very small area of the airflow causes the pulling-on process. Of the Most of the compressed air flows uselessly through the pipe. To compensate for these disadvantages requires the process uses a powerful and large compressor, which in turn consumes a lot of energy owns.

In addition, the force of gravity has a disadvantageous effect in the previously known method. While a thick layer of paint on the lower inside of the pipe forms, is due to the force of gravity and the resulting run-down of the paint, the paint layer only very thin on the upper inside of the pipe. The thickness of the paint layer is very uneven. On the An unnecessarily thick layer of paint must always form on the bottom inside, in order to get on the top at all still get a reasonably satisfactory color coating.

Due to the tangential injection of the air according to the invention with the generation of a particularly in the The main part of the kinetic energy lies in the outer peripheral zone of the high-energy spiral air flow Air jet in the outer peripheral zone, d. H. in the area in which the coating is to take place. Of the previous useless bulk of in the middle of the

The compressed air flowing through the pipe is largely switched off. The spiral air flow moves with it high speed around the pipe axis, while the speed is axia! relatively small along the pipe axis is to actually allow the paint to settle sufficiently to achieve on the inner surface of the pipe. The movement in the axial direction also takes place practically only due to the inevitably low pressure difference between the inlet side of the pipe system to be coated and the exhaust side. , " You have, as it were, a rotating air vortex, the main energy of which is in the outer circumferential zone in the area of the The inner surface of the pipe to be coated is concentrated and that due to this pressure difference through the pipe is moved through. ι -,

Particularly suitable devices for performing the method according to the invention are shown in Described subclaims.

The invention is to be explained in more detail below using a _{few exemplary embodiments and using the drawing: ".} It shows

Fig. 1 is a schematic diagram of the entire system of an embodiment of the invention;

Fig ..? enlarged and partly in section that of the first embodiment used nebulization nozzle ^ -,

F i g. 3 is an enlarged longitudinal section of a spiral ejector for mixing air and paint in a other version,

4 shows a perspective view of the ejector _{J (} > and

F i g. 5 shows an enlarged longitudinal section through a spiral ejector of a third embodiment.

According to FIG. 1, a nebulizing nozzle 1 is attached to an opening of a laid water pipe _{J3 that has previously been cleaned in any manner.} The tap and socket have been removed. Both ends of the tube are open.

For the sake of simplicity, the water pipe 2 is shown in FIG. 1 drawn as a straight piece. In fact, it can but several knee bends or branches aufwei- _{1 ()} sen.

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 ₄ -, flow through an A solution line 7 and a B solution line 8 into a mixing device 9. In the mixing device 9 the solutions A and B are mixed. The mixture passes a valve 10, a flow meter 11 and a line 12 and is _{fed to the 5 ()} inlet opening of the nebulizer nozzle 1. In the nebulizer nozzle 1, the paint or the like is broken up by the compressed air into a mist consisting of small liquid droplets.

Remaining compressed air is transferred from the compressor 13 via a valve 16 and a regulator 17 to a spray blower 18 fed. The flowing into the fan 18 through several tangentially arranged inflow openings Air forms a spiral-shaped flow of high-speed air in the fan. , 0

The nebulizer nozzle 1 sprays the mixture, which has been split into extremely fine particles, into the spiral fan 18. The Paint mist is set in strong rotation by the fast spiral air flow in the fan.

From the spiral air flow the color, when carried forward by the tube 2, striking and adhering to the inner surface thereof. Excess paint mist comes out at the other end of the pipe. With the help of a trigger device excess paint can be peeled off there.

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

The inner cylinder 20 is arranged concentrically in the outer cylinder 20. The nozzle body 21 is on Front end of inner cylinder 22 attached. Outer cylinder 20 and inner cylinder 22 are attached to the rear end designed as hexagonal body 23, 24 so that a wrench or other Tools can be attached.

The rear end of the outer cylinder 20 w>: is a Internal screw thread. The inner cylinder 22 is arranged in front of the hexahedral body 24 External thread 26 is provided. A ring 27 sits in front of the screw thread.

The outer cylinder 20 and the inner cylinder 22 are firmly connected by the screw thread 25. No air can escape through the external thread 26 and the ring 27. In the hexahedral End piece 23 of outer cylinder 20 is vertically let into an air inflow opening 28. Between There is therefore an air duct 29 in the outer and inner cylinders 20, 22.

The outside of the front part of the inner cylinder 22 has an external thread 30. Corresponding This external thread 30 is an internal thread 31 at the rear end of the nozzle body 21 The inner cylinder 22 and the nozzle body 21 are attached by the internal thread 31 and the External thread 30 screwed together.

The nozzle body 21, which tapers conically at the front and rear, has a bullet-like shape. In the On the outside 32 of the rear cone, several air outlet grooves are let in in the longitudinal direction. These Version is provided with ten outlet channels; in other embodiments, however, one gutter may be sufficient.

Leading radially outward from the interior 34 of the nozzle body 21 are at right angles to the side surface several color exit openings 35 let in.

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

The outside 36 of the front cone is provided with a step 37 so that a wrench here can be set.

The rear end of the inner cylinder 22 widens to an inflow opening 38 which has an internal thread having. It merges into a paint channel 39 in the cylinder 22.

The function of the nebulizer nozzle 1 is explained below:

The compressed air (from 1 bar to 7 bar per measuring unit) is fed through the air inlet opening 28 into the air duct 29 headed. The air flows through the narrow opening channels between the air discharge grooves 33 and the outer slopes 40 exist. Since the cross-sections of the opening channels are very narrow, form air flows of high speed. With increasing pressure in the air duct 29, the speed decreases of air currents too. In general, however, the speed of an opening through an opening exiting airflow must not be higher than the snap speed, which is a function of temperature and pressure is.

To the air flow from the air outlet grooves 33 with

To let the speed of sound escape, the air pressure must be above a certain critical value lie. Theoretically, this limit is around 1.8 bar absolute. Practically, the air pressure must be due friction losses must be higher than 2 bar. ■ -,

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 case, the air flow in the air discharge grooves 33 increases Supersonic speed. At the narrowest point in (the so-called "neck") the air flow reaches the speed of sound. The gutters widen again, and the air expands suddenly, with the density decreasing and the speed due to the strong Decrease in air density increases. The air flow therefore exits the at supersonic speed funnel-shaped discharge channels 33, and an air pressure of over 1 bar (per measuring unit) is sufficient Generation of a flow of air at supersonic speed. 21)

The nebulizer nozzle 1 according to FIG. 1 can easily generate air flows at supersonic speeds. 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 such of supersonic speed.

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

The described air flow with the speed of sound or supersonic hits almost at right angles on the outflowing paint and generates strong shock waves there.

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

The paint droplets sprayed by the nebulizer nozzle 1 are so small and light that they are affected by the effect of the Gravity is almost unaffected. The paint drops stay in the air for a long period of time.

The extremely low weight of the paint drops is an advantage. The spiral generated in the spiral fan 18 Air flow causes the paint mist to rotate. The paint mist is now from the fast spiral air flow carried forward in the tube.

Since the air flow is spirally guided, the overall speed on which the ability to transport drops of liquid over long distances depends can be increased without the need to increase the air flow. The total speed, the axial speed and the tangential speed of the total air flow are denoted by Vo, Ve and Vt mi

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

In a spiral air flow, the tangential velocity Vt is almost zero in the central axis and is greatest on the inner surface due to the viscosity. In order to keep the viscosity loss as low as possible, the tangential velocity Vt is approximately proportional to a radius R, except for a thin boundary layer on the inner surface.

The drops of paint are created in a spiral air flow for the most part carried by the most energetic area of the airflow.

The force of gravity does not affect the paint drops effectively, so that the tube 2 coated evenly can be. The difference between the thickness of the paint layer on the upper and the lower inside of the pipe is minimal as centrifugal force is much stronger than gravity. If the The paint consumption is reduced considerably when the coating is applied.

With the help of the spiral air flow, the drops of paint can pass through the pipe much faster because the paint droplets float in the air stream and not immediately on the inner surface occur. In the case of the traditional dispute, The straight air flow used, the paint liquid hits the inner surface of the pipe and is propelled forward by the small effect of shear forces between air and liquid.

The force that propels the paint forward in the pipe is small because the shear force is inherently weak and it is precisely the area of the direct air flow that causes the shear force, its most energy-poor part is. The time saving with this coating process is considerable, since it is precisely the most energetic area of the Spiral air flow carries most of the paint drops and directly on the paint drops exerted force is always greater than the shear force.

3 shows a further embodiment of the invention. A spiral ejector 41 is shown, which the Functions of the nebulizer nozzle 1 and the spiral fan 18 of the first embodiment 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 is injected through radially arranged nozzles 46 of the nozzle head 45 into the cylindrical fan 42. Through the Air inflow opening 43 arranged tangentially, compressed air flows in and is generated in the cylindrical housing 42 a spiral flow of air at high speed. The throttle cone 48 is on one in front of the nozzle body 45 attached with a screw-threaded rod 50 is fastened with screw nuts 49. the Nozzle opening 51 between throttle core 48 and housing 42 is adjustable. The adjustable opening 51 throttles the air flow in the housing 42. With their help, a uniform air flow can be maintained.

At a second aiisführur.gsfcrrr; becomes the air not ejected at the speed of sound. The color droplets generated by the air flow are therefore larger and heavier than the first run.

The throttle cone 48 directs the entire rotational energy into a narrow outer area, from which also the drops of paint are carried into the tube. The wide interior area of the spiral airflow is practically hardly usable for the paint transport.

Fig. 5 shows a section through another spiral ejector nozzle 60. This spiral nozzle 60 consists of a cylindrical housing 64 which is provided with a paint inlet opening 62 on the rear wall, furthermore from an air inflow opening 63 arranged tangentially on the side wall of the housing 61. The Liquid enters through the inlet opening 62

Interior 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 and provided with free energy. The drops of paint are carried forward in the pipe by the> spiral air flow. The paint drops are not as light as those produced in the nebulizer nozzle 1 of the first embodiment. The spiral ejector nozzle is simply constructed for this.

It is crucial that the invention is a fine drop of liquid carrying spiral air flow to Coating makes use of the inner surface of pipes. By means of a spiral that overcomes gravity A coating of uniform thickness can be applied by a stream of air. The consumption of time and i> Liquid is less. Because the drops of paint are being carried by the most energetic area of the air flow compressed air can also be saved.

Since the medium used to transport the paint is air, it can also be used for pipes with bends, Knees or branches are lined evenly.

In the present example, epoxy resin is used. However, any type of color can be used in the invention can be used: lacquer paint, vinyl resin paint, melamine resin paint, Phthalic Acid Resin Paint or Methyl Methacrylate Acid Paint. When using these colors only put one paint tank in use, as it was not mixed from two components before use Need to become.

The invention consists of a compressor in which compressed air is generated and stored; further from one or more paint containers for holding paint; also a spiral ejector nozzle, which one with Drops of paint enriched spiral air stream ejects at high speed, eventually out of a Paint feed device that supplies paint to the spiral ejector nozzle. This nozzle of the first execution consists of a nozzle body and a spiral fan.

For this purpose 2 sheets of drawings

Claims (4)

Palent claims: 1. Method of covering the inner surface of a pipe by passing a mixture of air and air blown through it at one end of the pipe Ink droplets, characterized in that the air is used to generate an in particular in the outer circumferential zone high-energy spiral air flow is blown tangentially. 2. Device for coating the inner surface of a pipe, characterized by a compressed air generating and storing compressor (13), one or more containers (3, 4) for receiving of color or the like. Furthermore, a spiral ejector nozzle (41, 60), which enriched one with drops of color ejects a spiral air stream and finally a paint feed device, which is the spiral ejector nozzle (41, € 0) supplied with paint 3 device according to claim 2, characterized in that that the spiral ejector nozzle (41, 60) consists of a nebulizer nozzle (I), which with an air stream fine drops of paint are produced by the speed of sound or supersonic and a spiral fan with consists of several tangentially arranged air outflow openings. 4. Apparatus according to claim 2, characterized in that the spiral ejector nozzle (41, 60) has a Has throttle cone to increase the speed of the air flow in the opening.