EP1035947A1

EP1035947A1 - Blasting method for cleaning pipes

Info

Publication number: EP1035947A1
Application number: EP98964479A
Authority: EP
Inventors: Jens-Werner Kipp
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-12-05
Filing date: 1998-12-02
Publication date: 2000-09-20
Anticipated expiration: 2018-12-02
Also published as: ES2169934T3; WO1999029470A1; US6315639B1; ATE211957T1; EP1035947B1; PL187959B1; PL340883A1; JP2001525261A; DE59802675D1; JP3623164B2

Abstract

A method and apparatus for cleaning pipes with the aid of a blasting medium in which a deflecting member surrounding a nozzle is blown through a pipe by the blasting medium blowing through the nozzle. The movement of the deflecting member and nozzle can be controlled with either a draw-rope from the upstream end of the pipe or a rod from the downstream end. Dry ice, sugar, or chemical agents may be added to the blasting medium as an blasting means.

Description

BLASTING METHOD FOR CLEANING TUBES

The invention relates to a blasting method for cleaning pipes and devices which are suitable for carrying out this method.

Blasting devices generally serve to clean surfaces with the aid of a mostly gaseous blasting medium, to which an abrasive blasting agent such as sand or the like can be added. It is also known to use dry ice or dry snow as a blasting agent. The use of dry ice has the advantage that the substances to be cleaned and subsequently disposed of are not increased by additional blasting agents, since dry ice evaporates after use.

The dry ice has a cleaning effect by:

1. Thermal shock embrittlement of the material to be cleaned with cracking (thermal stress)

2. Penetration of particles into the cracks in the materials to be cleaned, caused by thermal stresses, followed by an abrupt increase in the volume of the particles during the transition to the gaseous state (sublimation), which leads to a "detachment" of the materials to be cleaned

3. Kinetic energy when the particles hit the materials to be cleaned at high speed.

In view of a quick and efficient cleaning of larger areas, it is desirable that the jet generated by the jet nozzle is fanned out as far as possible. For this purpose, flat nozzles are known which generate a fan-like widened jet. When using abrasive blasting media, however, there is a disadvantage in that the particles of the blasting media impinge on the tapered walls of the nozzle, so that there is either increased wear on the nozzle or, in the case of dry ice, the particles of the blasting media are finer Particles are broken up that no longer have any significant abrasive effect. The object of the invention is to provide a blasting method and blasting devices which enable an efficient and thorough cleaning of the inner surfaces of pipes or other hollow bodies, in particular with dry ice.

This object is achieved with the features specified in the independent patent claims. Advantageous refinements of the invention result from the subclaims.

The basic idea of the method according to the invention is that one moves a deflection body around which the blasting medium flows through the pipe to be cleaned. The deflecting body gently deflects the blasting medium and possibly the blasting medium carried in it, for example pellets made of dry ice, onto the pipe wall in the radial direction and at the same time accelerates it, so that a uniform, intensive cleaning action is achieved over the entire inner circumference of the pipe.

The flow of the blasting medium can be generated either with the aid of a blasting nozzle moved through the pipe together with the deflection body or with the aid of a pressure or suction blower arranged at one end of the pipe to be cleaned.

The subject of claim 6 is a blasting device with a blasting nozzle moved through the tube, which tapers continuously to a constriction in an upstream section and continues to widen downstream from the constriction and that a deflection cone is arranged downstream of the constriction and coaxial to the blasting nozzle is.

With the help of this jet nozzle, a conically fanned jet is generated, so that a correspondingly large working width of the jet device is achieved, which is therefore also suitable for other applications. Such a jet nozzle can, however, be used particularly advantageously for cleaning the inner surfaces of pipes, for example in tubular heat exchangers. The blasting nozzle is then simply moved coaxially through the tube, so that the entire inner surface of the tube can be blasted uniformly with the aid of the conically widened jet. If a blasting medium is added to the blasting medium, it has surprisingly been found that the particles of the blasting medium hardly strike the deflecting cone. The reason for this should be the special flow and pressure conditions that result from the nozzle shape according to the invention.

The pressure and volume output of the pressure source is preferably matched to the blasting nozzle in such a way that the blasting medium reaches the speed of sound at the constriction of the nozzle. Because of the Laval effect, the blasting medium can then be accelerated to supersonic speed in the downstream part of the nozzle, so that a particularly intensive cleaning effect is achieved. A stationary shock wave in the shape of a Mach cone forms at the tip of the deflection cone. This shock wave presumably helps to keep the abrasive away from the surface of the deflection cone.

The deflection cone can be connected to the jet nozzle via a plurality of retaining webs distributed over the circumference of the jet nozzle, so that the tip of the deflection cone is always held at a defined distance from the constriction of the jet nozzle. Provided that a certain degree of bendability of the device is desired when cleaning pipes, the retaining webs and a lance carrying the jet nozzle can be elastically flexible. Especially with dry ice as a blasting agent, it is advantageous that the suspension of the deflector is not in the middle, but on the circumference of the nozzle, so that the shock-sensitive pallets are not broken prematurely.

In a modified embodiment, the deflection cone is a separate component that is not connected to the jet nozzle. In this case the deflection cone is blown through the pipe to be cleaned with the aid of the jet generated by the jet nozzle. The jet nozzle is then only inserted a short distance into the pipe end or pressed against the pipe end and, if necessary, sealed with a gasket on the pipe. The pressure of the blasting medium is regulated so that the deflection cone is driven through the pipe. The centering of the deflection cone on the pipe axis can either be achieved purely aerodynamically or with the aid of at least three flexible guide rods or runners, which form a guide for the deflection cone as it moves through the pipe. The deflection cone itself can also be flexible with regard to the ability to bend. Optional For example, a spherical deflecting body can also be provided instead of the deflecting cone.

The guide rods can also be fixedly attached to the jet nozzle and form a stop for the deflecting cone at the free end, so that it can be moved in the axial direction within a limited range relative to the jet nozzle. The jet nozzle is then pushed or pulled through the pipe during the cleaning process.

Skids or other centering devices can be provided for centering the jet nozzle in the tube. If the jet nozzle is pulled through the tube, aerodynamic self-centering effects can also be used to center the jet nozzle.

In the device according to claim 8, the outside diameter of the nozzle itself does not have to be larger than the outside diameter of the deflecting body, so that a slim design, also suitable for pipes with a small inside diameter, is achieved.

When the baffle is connected to the nozzle. So this connection must be tensile, but it can also be relatively unstable or flexible, since the deflector centers itself in the tube due to dynamic effects. This can also improve the guidance of the nozzle in the tube.

Since the deflection of the blasting medium and the blasting medium is effected by the deflecting body, there is a high degree of design freedom with regard to the design of the actual nozzle. In particular, the nozzle can be designed as a Laval nozzle, with which high flow velocities of the blasting medium, possibly even supersonic flow, can be achieved.

If the deflecting body moves through the tube alone, that is to say without the nozzle, the movement of the deflecting body must be braked so that its speed is always lower than the flow rate of the blasting medium and the desired deflecting effect is achieved. In the exemplary embodiments, there are various options for delaying the Movement of the deflector shown.

The use of dry ice has so far been ineffective in cleaning materials or coatings in which shock cooling (approx. -80 ° C) does not or only to a small extent leads to brittleness of the material with subsequent crack formation, e.g. with hardened limescale deposits, hard deposits of organic substances or gypsum deposits. Since the shock cooling does not lead to thermal stresses or cracks, the dry ice particles cannot penetrate into the material or between the material to be cleaned and the workpiece surface and therefore cannot lead to blasting by sudden sublimation. The kinetic impact energy of the relatively soft dry ice then has only a minor effect.

The flow rate in the entire tubular body must be so high that the abrasives used are initially guided up to a few times in the deflecting body - here the flow rate can be greatly increased by the narrowing caused by the deflecting body - and then discharged from the tubular body.

By adding an additional, slightly to strongly abrasive blasting agent to the dry ice, an improvement in effectiveness is achieved which also enables the cleaning of materials that cannot be removed with dry ice alone.

The additional blasting agent can be a slightly abrasive blasting agent. Optionally, a highly abrasive blasting agent such as blasting granulate can be added. The addition of chemical agents, e.g. descaling agent possible. To stabilize the dry ice pellets, it may also be expedient to add a cold gas, e.g. to add cooled N2 or the like.

The additional blasting media should be designed / dosed in such a way that they bring no or only as little waste increase as possible and do not cause any damage - eg due to subsequent corrosion - to the surfaces to be cleaned. It is therefore particularly advantageous to add additional abrasives that are water-soluble, are contractually agreed for water and clearing systems due to the small amounts of residues and do not cause any after-effects of corrosion. The additives should also be cold-resistant or the abrasiveness should be increased by the low temperatures Additional blasting media do not affect the mode of operation of the dry ice as a blasting media. For example, sugar in crystalline or powdered form is suitable

The ZLisatz blasting agent can be added by mixing with dry ice. The mixing ratio can be selected as required

The additional blasting medium can also be sucked in (by the dynamic pressure of the blasting medium) (injection nozzle). This suction can take place through a branching line in the nozzle or in the line feed between the dry ice input device and the blasting nozzle

When cleaning pipelines using a cone nozzle or a blasting adapter attached to the pipe end, backpressure of the blasting medium can occur in the blasting nozzle, for example, due to contamination. In this case, it is advantageous to also add pressure to the blasting medium of the blasting medium In this case, the additional blasting medium can also be supplied at the blasting nozzle or the blasting adapter or in the line feed between the dry ice input device and the blasting nozzle or the blasting adapter

The pressure of the blasting medium, with the aid of which the additional blasting medium is fed, should be similar to the pressure of the main stream or in any case so high that a back pressure of the additional blasting medium caused by back pressure is avoided and a uniform jet of the combined blasting media and blasting medium is achieved

Above certain nominal pipe sizes, the blasting medium required for the method according to the invention can become so great that a pressure source such as a compressor or an evaporator for producing the high ones Flow speed is no longer sufficient or can no longer be used for economic reasons.

The invention therefore also includes a method for cleaning pipelines with the aid of a gaseous blasting medium with or without the addition of solid or liquid blasting media, in which the blasting medium is conveyed through the pipeline with the aid of at least one suction device.

This process also allows pipes with larger pipe cross-sections to be cleaned by blasting.

In this method a flow of the medium e.g. an air flow is generated with the aid of suction devices. Several suction devices can be coupled to one another or used simultaneously.

The tube body is closed at one end. The closure is provided with one or more connection options for suction lines and corresponding suction devices.

At the opposite open pipe end, the deflector is introduced, which is guided by a rope and / or by pressing one or more parts against the inner wall of the pipe. The deflection body is transported through the pipe by the suction effect generated by the suction devices.

At the beginning of the suction, the air flow is preferably mixed with a blasting agent of your choice. The blasting agent can be introduced into the pipeline under pressure or sucked in by the speed of the air flow, is then guided to the deflecting body and is directed here against the inner wall of the pipe at a greatly accelerated rate. The abrasive and the materials detached from the surface are then discharged by the air flow and can be separated from the air flow by means of separators / filters.

If the deflection body is not transported through the pipe body solely by the air flow - especially with bendable lines, the transport of the deflection body can also be supported by a pull rope attached at the front. Preferred exemplary embodiments are explained in more detail below with reference to the drawing.

Show it:

Figure 1 is a schematic longitudinal section through a section of a tube and a blasting device according to the invention.

Figure 2 is a schematic longitudinal section through a blasting device according to a modified embodiment.

FIG. 3 shows an axial section of a blasting device according to a further exemplary embodiment;

Figure 4 is a partially broken side view of the essential

Elements of a blasting device according to another embodiment;

FIG. 5 shows a schematic longitudinal section through a section of a blasting nozzle with a feed line for an additional blasting agent; and

Figure 6 is a schematic diagram of a blasting device according to another embodiment.

The blasting device shown in FIG. 1 has, in a manner known per se, a pressure source 10, for example a compressed air compressor, which is connected to a blasting nozzle 14 via a flexible pressure hose 12. A metering device 16, also known per se, for metering a blasting agent, for example dry ice, into the compressed air stream can be provided in the compressed air line between the compressor and the blasting nozzle.

In the example shown, the blasting nozzle 14 is part of a blasting head 18 which can be pulled or pushed axially through the interior of a pipe 20 to be cleaned. The pressure hose 12, a lance or a pull rope attached to the opposite end of the blasting head is used to push or pull the blasting head. The jet nozzle 14 is designed as a Laval nozzle and accordingly has an upstream section 22 which tapers from a coupling piece 24 for the pressure finally, approximately conically, to a constriction 26. A downstream section closes the upstream section 22 28, which expands again and again from the constriction 26 Due to the tapering of the upstream section 22, the flow rate of the compressed air increases towards the constriction 26. With sufficient pressure and volume output of the pressure source 10, the compressed air at the constriction 26 reaches the speed of sound while the pressure there decreases to the Laval pressure. The gradual expansion of the downstream section 28 of the jet nozzle has the result that the compressed air behind the constriction 26 is accelerated further and thus reaches a multiple of the speed of sound

The probe 18 also includes a deflection cone 30, which is aligned coaxially with the jet nozzle 14 and whose tip protrudes into the gas jet emerging from the jet nozzle. The approximately conical deflection surface 32 of the deflection cone 30 is slightly concavely rounded in longitudinal section in the example shown the tip is about 12 ° in the example shown

The sections 22 and 28 of the jet nozzle have approximately the same length, and the opening cross section at the mouth 34 is in the example shown twice the cross section at the constriction 26

In the embodiment shown, the tip of the deflection cone 30 lies exactly at the level of the mouth 34 of the jet nozzle 14. The tip of the deflection cone can also protrude somewhat into the jet nozzle. In this case, the design of the downstream section 28 of the Laval nozzle is that of the deflection cone account for the omitted cross-section

The supersonic jet emerging from the jet nozzle 14 is deflected radially uniformly in all directions by the deflecting cone 30, so that it takes the form of a conical jacket and in this form strikes the inner wall of the tube 20 uniformly Effects are also deflected radially outwards and thus develop their abrasive effect on the wall of the pipe 20, while only a negligible part of the entrained particles comes into contact with the deflection cone 30.

In the exemplary embodiment according to FIG. 1, the deflection cone 30 is held on the jet nozzle 14 with the aid of three rods 36 arranged at angular intervals of 120 °. This ensures that the tip of the deflection cone 30 is always precisely centered on the axis of the jet nozzle 14. The rods 36 can have a triangular or lenticular cross section and form a kind of cutting edge on the inside, so that they do not form any significant obstacle for the emerging blasting medium.

The opposite ends of the rods 36 are embedded in corresponding longitudinal grooves in the outer surfaces of the jet nozzle 14 and the deflection cone 30 and fastened by welding or in some other way. In this way, a particularly small design of the probe 18 is achieved, which is also suitable for cleaning tubes 20 with a narrow cross section.

FIG. 2 shows an embodiment of the blasting head 18 which is suitable for pipes with a larger cross section or for blasting freely accessible surfaces. The tip of the deflection cone 30 protrudes somewhat into the mouth of the jet nozzle 14. The downstream section 28 of the jet nozzle is widened somewhat more towards the mouth than in the exemplary embodiment according to FIG. 1, so that the cross-sectional ratio between the free exit surface at the mouth and the cross-sectional area at the constriction 26 is again approximately 2: 1.

The rods 36 are designed here as round rods, which engage with thinner end sections 38 in corresponding axial bores 40 of the deflection cone 30 and the jet nozzle 14. The end sections 38 and the bores 40 can be provided with right and left hand threads so that the rods can be screwed to the jet nozzle and the deflection cone. The bores 40 of the deflecting cone 30 are widened step-wise at the end facing the jet nozzle 14 and take up the thicker central section of the round rods 36, so that a clean connection of the round rods to the deflecting surface of the cone is achieved.

In the example shown, the thicker middle sections of the round bars 36 meet butt against the end face of the jet nozzle 14, so that a defined distance between the jet nozzle and the deflection cone 30 is maintained. Optionally, however, the arrangement can also be such that the round rods also engage in enlarged bores in the jet nozzle 14. In this case, the axial distance between the deflection cone 30 and the jet nozzle 14 can be varied continuously within certain limits, so that the jet characteristic can be optimized.

The blasting device shown in FIG. 3 is used to clean the inner surfaces of a pipe 110 using a solid or liquid blasting medium with or without a blasting medium.

A nozzle 112 in the form of an adapter that can be coupled to the pipe end serves to introduce the blasting medium into the pipe under high pressure. In the example shown, the nozzle 1 12 simply has an outer cone 1 14 at the front end, which engages in the pipe end and lies tightly against the inner wall of the pipe when the nozzle is held by hand with slight pressure against the pipe end. A pressure hose, not shown, can be coupled to the opposite end of the nozzle, via which the blasting medium is supplied.

ZLI also belongs to the blasting device, a deflecting body 1 16 formed separately from the nozzle 1 12. In the example shown, the deflecting body 1 16 has an elongated, boat-like shape with a conically shaped upstream end 1 18. The cross-sectional shape of the deflecting body 1 16 is similar to that Cross-sectional shape of the tube 1 10 adapted and is accordingly circular in the case of round tubes. The outer diameter of the deflector is slightly smaller than the inner diameter of the tube 110.

In an axial bore 120 of the deflector 1 16, a traction cable 122 is fastened, which runs through the pipe 1 10 and through the mouth of the nozzle 1 12 and exits the pipe 1 10 through an oblique lateral opening 124 from the nozzle 1 12. The free end of the pull cable 122 is held by hand, unwound from a winding device, not shown, or gradually reduced with the aid of a lever-operated self-locking locking mechanism, as is known, for example, from cartridges for pressing out pasty masses. The blasting medium emitted by the nozzle 112 flows through the pipe 1 10 at high speed and strikes the conical end 1 18 of the deflecting body 1 16 and is thereby deflected radially outward so that it hits the pipe wall at an angle and cleans the inner surface of the pipe . A blasting medium with a moderately abrasive effect, for example dry ice, can be added to the blasting medium. To supply the blasting agent, the nozzle 1 12 can be provided with openings corresponding to the opening 124. These additives can also be used to add other additives to the blasting medium, for example in order to chemically treat the pipe wall or to "coat" it so that it is limescale or dirt-repellent.

The blasting medium is deflected by the deflecting body 116 as well as the blasting medium, so that intensive cleaning of the tube wall is achieved. It has been shown that the particles of the abrasive hardly hit the surface of the deflecting body due to fluid dynamic effects, but are deflected by the flow in such a way that they hit the pipe wall directly. The blasting medium and the blasting medium as well as any material removed from the tube wall pass through the annular space between the deflecting body and the tube wall and are discharged via the tube end opposite the nozzle 112.

When the traction cable 122 is gradually released, the deflector 116 moves self-centered through the pipe, so that the pipe 10 can be gradually cleaned over its entire length.

Figure 4 shows an embodiment of the deflector 116, which is suitable for even smaller pipe diameters.

The deflecting body according to FIG. 4 has a boat-shaped upstream part 126 and a conical downstream part 128 which is designed as a separate component. The two parts 126, 128 can be screwed together or otherwise secured to one another. The upstream part has a conically widening section 130, a shorter cylindrical section 132 and a conically tapering section 134, which follow one another in the specified sequence in the direction of flow. Together with the cylindrical tube wall, part 126 forms an annular nozzle, the cross section of which is like a Laval nozzle first narrowed and then expanded again. In this way, a very high flow velocity, possibly supersonic velocity, can be achieved by the Laval effect downstream of the part 126. The conical part 128 forms the actual deflection body, which then directs the blasting medium and the particles of the blasting medium onto the tube wall at high speed. However, the blasting medium can also be directed to the pipe wall for the first time through section 130.

The deflecting body 116 according to FIG. 4 has the axial bore 20 and also has in its cylindrical section 132 a cross bore 136 which is provided with an internal thread and which allows the traction cable 122 to be fixed with a grub screw.

If a highly abrasive abrasive is used, the pull rope can be damaged and tear. In this case, it is expedient to delay the movement of the deflecting body 116 with the aid of a rod 138 which is inserted into the tube 110 from the opposite end and guided by hand or by machine. The section 134 and the conical part 128 of the deflecting body have an axial bore 140 with a larger diameter a if, into which the rod 138 can be inserted or screwed.

Finally, the deflecting body 116 can also have a friction body or scratch 142, which is shown in dash-dot lines in FIG. The scraper 142, with its blades, rests against the inner wall of the tube, preferably with elastic pretension, and thus produces a braking effect which delays the movement of the deflecting body 116. For example, the rod 138 or the pull cable 122 can be dispensed with. At the same time, dirt adhering to the pipe wall is loosened by the scratch 142. In the example shown, the scratch 142 serves for pre-cleaning, which loosens the contaminants before they are completely removed with the jet deflected by the deflecting body. Optionally or additionally, however, a dragged scratch can also be provided on the deflecting body for cleaning the emitted surface. The blades of the scraper 142 can be slightly helical, so that the deflector rotates about its longitudinal axis as it moves through the tube. 5 shows a blasting nozzle 210 which is attached with its tip to one end of a pipe 212 to be cleaned and which is supplied via a line 214 with a gaseous blasting medium (air) which has already been mixed with dry ice Introducing the blasting medium and the blasting medium into the tube 212 Since a nozzle effect is not absolutely necessary, the blasting nozzle is also more appropriately referred to as a blasting adapter however, everything also takes place according to the jet pump principle due to the negative pressure generated in a conical part 218 of the jet nozzle. A secondary channel 222 running obliquely into the main channel is formed in a head part 220 of the jet nozzle which adjoins downstream

6 schematically shows a dry ice input device 224 which is connected via line 214 to the jet nozzle 210 attached to one end of tube 212. An end piece 226 is connected to the opposite tube end, which in the example shown is connected to two suction blowers 228

A traction cable 230 enters the pipe 212 through the secondary duct 222 of the jet nozzle 210 and exits again at the opposite end of the pipe through an opening in the end piece 226. With the aid of this traction cable, a deflector 232 can be pulled through the pipe 212 in the longitudinal direction

The two suction blowers 228 working in parallel have a significantly higher delivery capacity than can be generated with conventional compressors or evaporators and thus allow a high flow rate to be maintained inside the pipe even with pipes 212 with a relatively large diameter.The ambient air is sucked in via the nozzle 210 and in the dry ice dispenser 224 mixed with dry ice. Optionally, the additional blasting agent can be supplied via the inlet 216. Inside the tube 212, the air mixed with the blasting agents is accelerated again at the deflector 222 and deflected onto the tube wall, so that an intensive cleaning effect is achieved 226 contains a separating device or a filter for the discharged material and, if necessary, the solid additional blasting agent. The separating device, for example in the form of a cyclone, can also be integrated into the suction blower 228

Claims

PATENT CLAIMS

1. blasting method for cleaning pipes with the aid of a blasting medium, characterized in that a deflecting body (30; 1 16; 232) is moved through the pipe (20; 1 10; 212) and the blasting medium flows around it.

2. The method according to claim 1, characterized in that the gaseous blasting medium is added dry ice as the blasting agent.

3. The method according to claim 2, characterized in that in addition to the dry ice, another blasting agent, for example sugar, or a chemical agent is added.

4. The method according to any one of claims 1 to 3, characterized in that the blasting medium is blown into the tube (1 12; 212) at one end.

5. The method according to any one of claims 1 to 4, characterized in that the blasting medium is sucked in at one end of the tube (212).

6. blasting device with a blasting nozzle (14) and a pressure source (10) for supplying a blasting medium under pressure to the blasting nozzle, characterized in that the blasting nozzle (14) is continuously in a upstream section (22) to a constriction (26 ) tapers and expands again downstream from the constriction and that a deflector (30) is arranged downstream of the constriction (26).

7. Blasting device according to claim 6, characterized in that the jet nozzle (14) and the deflector (30) by at least three on the

Distributed axial rods (36) are connected to one another around the circumference of the jet nozzle and the deflecting body.

8. blasting device for blasting the inner surfaces of pipes (1 10), characterized by a coaxially aligned to the pipe, the blasting medium emitting nozzle (1 12) and a deflector (1 16), which directs the blasting medium onto the pipe wall and with the largest Part of its length lies axially behind the mouth of the nozzle (12) and can be moved through the tube alone or together with the nozzle.

9. The device according to claim 8, characterized in that the nozzle (1 12) is designed as a couplable to the tube end adapter for introducing the blasting medium into the tube and that the deflector (16) is movable relative to the nozzle through the tube.

10. The device according to claim 8 or 9, characterized in that the deflector (1 16) at the upstream end has a widening section (130) and further downstream a tapered section (134) to which a part downstream (128 ) which widens in the direction of flow.

11. Device according to one of claims 8 to 10, characterized in that the deflecting body (1 16) or optionally the unit consisting of deflecting body and nozzle has a friction body (142) which is in frictional contact with the inner wall of the tube (10).