WO1999059730A1 - Method and device for applying a plastic layer to the inner surfaces of hollow bodies - Google Patents

Abstract

The invention relates to a method and a device for applying a plastic layer consisting of at least two components to the inner surface of a hollow body. A coating device which has been introduced into the hollow body travels through the same, providing the hollow body with a coating. After, the components of the plastic have been mixed inside the coating device, the axial speed at which they are conveyed propels them out of a mixer outlet opening (8) inside the centrifuge chamber (3) onto a cone (9) facing said mixer outlet opening (8). The components accelerate considerably, with the result that the plastic is more rapidly distributed on an impact plate (5) and is spun onto the inner surface of the hollow body in a sheet, via a discharge opening (7).

Description

 description

Method and device for applying a plastic layer on the inner surfaces of hollow bodies

description

The invention relates to a method and a device for applying a plastic layer on the inner surface of hollow bodies, which protects against wear and corrosion, in particular in supply and disposal lines, in which the flow behavior of the conveyed medium can thus also be improved. Methods are known in which a plastic is applied to the inner wall of pipes by means of a rotating spray nozzle. These methods have the disadvantage that the pressure loss required to break the jet considerably limits the possible insertion length into the pipe to be coated (DE-OS 2715849). The use of a centrifugal disc, which brings the conveying flow to a high coating energy due to its rotational movement, is cheaper, especially if radially arranged guide plates are attached to the centrifugal disc or radial arms are used (DE-OS 2808903, 2826628, 3518584 A1, DE-GM 150997 ). Furthermore, methods are known which work with centrifugal disks in which the plastic mixture is applied to a centrifugal disc open against the direction of pull. This accelerates the mixture in a spiral on the spin plate, which means that the relatively long stay - when using very highly reactive PUR - can lead to premature curing of the mixture. Furthermore, segregation effects can occur.

The object of the present invention is to improve the above-mentioned methods and devices.

The production of thick layers from 1 to> 20 mm in one pass requires highly reactive plastics such as polyurethanes or polyureas (PUR) that have thixotropic behavior and pot lives of 0.5 to 10 seconds. When processing such plastics, there is a risk that components which may harden prematurely may block the device. It is therefore necessary that Keep PU as short as possible after mixing in the coating device.

According to the invention the object is solved by claims 1 and 9. Advantageous developments of the invention are contained in the respective associated claims.

According to a preferred feature of the invention, the plastic, which is composed of at least 2 components, is applied to the inner surfaces of a hollow body, preferably a tube, by a coating device introduced into the hollow body passing through the hollow body, the components of the plastic being mixed by the coating device within the coating device axial conveying speed via a mixer outlet opening within a centrifugal chamber to one of the

Impact the cone of the mixer outlet on the opposite side and experience increased acceleration, as a result of which the plastic is distributed more quickly on a baffle plate and the plastic is spun onto the inner surface of the hollow body over a discharge opening.

According to a further feature of the invention, the coating device is pulled through the hollow body.

According to another feature of the invention, the plastic can also be accelerated and thrown out via baffles arranged inside the centrifugal chamber.

According to a further feature of the invention, the plastic discharged from the discharge opening of the mixer can additionally be mixed with a granular and / or fibrous filler, these fillers being fed via a feed and distribution device which is arranged in the immediate vicinity of the coating device.

According to a preferred feature of the invention, the introduction length of the coating can be increased by integrating additional feed pumps within the hose package. The present invention further includes a device for applying a plastic layer composed of at least two components to the inner surfaces of hollow bodies, which comprises at least one mixing device and at least one centrifugal disc connected to it. The mixing device is arranged within a rotating hollow shaft of the rotating centrifugal disc, the centrifugal chamber forming a centrifugal disc which is formed from a baffle plate and a carrier disc, the baffle disc and carrier disc being connected to one another by a profiled discharge opening and the baffle disc being one has a cone directed towards the mixer outlet opening.

According to a preferred feature of the invention, the coating device is designed in duplicate, the centrifugal plates being set at an angle to one another and the outlet openings preferably being designed as interlocking radial arms.

According to a further feature of the invention, a feed and distribution device for granular and / or fibrous fillers are arranged on the transport device in addition to the coating device.

The invention will be explained in more detail below using an exemplary embodiment. In the drawings, the

FIG. 1 shows a schematic representation of the coating device in cross section,

Figure 2 shows a schematic representation of the overall system.

The reference symbols are explained on the list of the reference symbols used.

The centrifugal technology consists of a PUR system (material container, pumps, heating, control, etc.), supply hose package, transport device and coating device, as shown in Figure 2, as well as compressed air compressor and electric generator. These are described in more detail below.

The PUR plastics in question have viscosities of up to 15,000 mPas at 20 ° C and, for example, 80 mPas at 70 ° C. PUR are thixotropic fluids. Around To be able to process viscosities, an agitator is required at least in the storage container on the isocyanate side, which keeps the material flowable. The isocyanate component is hydrophilic, which means that at least this storage container must be hermetically sealed and nitrogen must be applied. An alternative to nitrogen is dried air or air which is dried by filters which contain, for example, silica gel.

The storage containers have a content of approx. 100 I. However, the contents of these storage containers are larger for longer insertion lengths, i.e. with DN 500 and 5 mm layer thickness already used up after approx. 24 m. A refill system is therefore required to ensure the ongoing supply. The heating can e.g. consist of a downdraft heater that brings the material to processing temperature. The temperature is then kept up to the mixer by the separately heated material hoses.

Due to the required delivery lengths and the expected high pressure loss, delivery pressures of 300 to 500 bar are required. High-pressure systems are therefore required. These high pressures are achieved with piston pumps that are operated with either compressed air or electrical current. The metering can take place via balance beam systems - which are set manually - or special volume flow devices.

A PLC control makes sense for the use of such volume flow control systems. The entire system control, such as delivery pressure, metering, temperature control, etc. can be programmed or regulated via a PLC (programmable logic controller).

The supply hose package consists at least of the material hoses and the compressed air line for the centrifugal disk drive. The material hoses consist of high pressure hoses, e.g. are common in hydraulics. The heating is done by creating a def. Current that generates heat through the flow resistance of the metal reinforcement.

Depending on the monitoring and control requirements of the coating device, however, signal lines are to be provided which are used to transmit data from e.g. B. volume flow measuring device, temperature monitoring and speed measurement.

Depending on the task, a pull rope can be integrated into the feed hose package, see transport device. The coating in a single pass appears cheap. In this way, the times for the introduction of the coating device or the number of necessary cable runs into the pipe can be kept as low as possible. The insertion length and the feed should be as large as possible. The high performance of the system also increases the effect of any errors that may occur. The occurrence of errors can, for example, lead to the complete PUR system becoming unusable due to premature curing. The prerequisite for high performance is the behavior of the PUR after application: it should have a uniform layer thickness and a smooth surface in the intended layer thickness, which is 10 mm. However, this is only possible if the material loses its flow property after striking the wall. For this purpose, the pot life of the material and / or the thixotropy can be set accordingly short or high. In order to be able to maintain these properties, the mixing ratio as well as the temperature must be strictly observed.

The coating device consists of a transport device on which the mixer, centrifugal disc, motor and monitoring devices as well as any additional devices are mounted.

The dwell time of the reactive mixture should be kept so short that there can be no hardening inside the head.

Mixing must be very thorough.

The energy of application of the material should be as high as possible, since it is assumed that the mixture has reached the "last one" due to high kinetic energy

Roughness "penetrates. Furthermore, the necessary high speed gradient is supported, which only makes thixotropic fluids flowable. The impact energy is necessary to ensure the necessary adhesion of the material to the wall and also to adapt to different diameters (especially in the case of the To support passage of arches).

No pressure loss due to redirecting the flow to the wall. Self-cleaning of the mixer and the disc, therefore less prone to errors. Self-cleaning is urgently required, as stops should be unavoidable, especially with large insertion lengths, and this also enables partial renovation or repairs.

In order to keep the mixing and residence time as short as possible, countercurrent injection mixers can be used. The material is likely to be emitted as a jet, but it scatters. In order to be able to compensate for this scatter, According to the invention, the flow is directed towards the “opposite” disc and there is immediately directed to the circumference by the distribution cone. The advantage of this arrangement is that the mixture flow is completely collected, particularly at high discharge speeds from the mixer.

In this arrangement, the mixture flow is guided centrally onto the centrifugal plate, which leads to an even distribution of the mixture over the circumference of the disc with the shortest possible residence time. The acceleration of the mixture can be increased significantly by using baffles. This leads to the fact that the mixture is "channeled" as soon as it hits the disk and thus immediately reaches the angular velocity of the disk. This also significantly increases the application energy of the mixture, since friction losses due to slippage are hereby excluded. The "channeling" of the Mixture should bring another advantage: The use of further baffles, which extend the path of the mixture significantly, allows further mixing of the mixture. The centrifugal force caused by the rotational acceleration "pushes" the mixture in the direction of the circumference. Static mixers function in the same way, but the necessary delivery energy is generated by the delivery pressure. In this case, the baffles could also be supported by a "ball packing". However, this principle can only work by channeling the mixture on the centrifugal disc; removing the baffles could have the effect of a centrifuge: the mixture segregates again, because the components have approximately the same densities, but a very different flow behavior.

In any case, the high speed of the centrifugal disc should be sufficient to automatically clean the disc - even if further mixing takes place there. The use of the mixture on the centrifugal disc could rel. enable simply designed mixers that manage with fewer moving parts.

"Conventional" counter-current injection mixers spray the components to achieve better wetting. This results in a pressure loss at the expense of the possible hose length, which should be avoided. Furthermore, a flushing device is necessary.

The use of a needle valve would offer several advantages: The valves for separately shutting off the component supply would be replaced by the needle valve, which shuts off both components at the same time. The cleaning is done also through the needle valve, which pushes out a material plug. However, the use of the simultaneous shut-off requires absolutely identical material pressures of the components so that no component can get into the supply of the others. The use of the needle valve thus increases the system's susceptibility to errors and should therefore be thoroughly reconsidered or tried out.

A counter-current injection mixer can also be replaced by a dynamic mixer. However, this should be designed as a "friction mixer" since these are self-cleaning. The components are mixed here by means of a high-speed screw (12000 to 20,000 rpm), which is conical and wall-accessible, due to the high shear stress between the screw and the cylinder wall However, an additional motor is required for this mixer. An alternative to both of the aforementioned mixers is the static mixer, which, however, must then be equipped with a compressed air purge. Only mixers that use compressed air should be taken into account when selecting the mixer In contrast to solvents for driving the centrifugal disc, compressed air is already supplied, whereas the use of solvents requires additional effort, which should be avoided due to costs, environmental and space reasons.

Since the centric application of the mixture to the centrifugal plate is advantageous, the centrifugal plate must be attached to a hollow shaft in any case. The shape of the centrifugal disc should promote the rapid, even discharge of the mixture and ensure the most flat possible application. The flat application is necessary to compensate for uneven feed. The flat discharge can be achieved by a sawtooth profile on the circumference. The mixture is discharged over the entire width of the profile. Another method is to carry out the channeling in such a way that the individual channels e.g. be shaped tubular and offset. The size of the centrifugal disc should be as large as possible to increase the application energy to a maximum. It is important to ensure that different pipe diameters can be coated with as few devices as possible.

It seems sensible to increase the application energy by high speeds, avoiding too fine atomization. "Drops" appear cheap here entrain little air (and thus reduce the void content of the layer), which, however, "bind" more kinetic energy than small "droplets" due to its size.

The transport device serves to receive the coating device.

The adaptation to different pipe diameters can be achieved by using e.g. B. pneumatic actuators. This allows the passage of z. B. Reductions are made. The reduction is recognized by a TV camera carried along or by the sudden stoppage of the coating (whereby the material supply must be stopped immediately (automatically)). Longer insertion distances and 3-D geometries may require the use of a self-drive. While the device can be fed over the feed hose package over a pull rope and winch for shorter distances, the friction of the pull cable and the mass of the feed hose package, which increases in proportion to the insertion length, should no longer be sufficient when traveling through bends and longer distances. The drive can take place via electrical energy or compressed air. A self-propelled with rapid traverse has the main advantage that no rope connection has to be made before coating begins. The coating can be retracted automatically, which only requires opening the tube. The combination of scissors and self-propelled should continue to enable "climbing" in cables. With climbing, 3D geometries can also be climbed uphill in industrial plants, for example. The remotely adjustable scissors in conjunction with friction-increasing wheels enable "clamping". in the tube, which is the prerequisite for climbing.

Since the core of the coating consists of a centrifugal disc, mixer and motor, this is rel. small. It could therefore also be placed on an existing renovation robot.

The more functions spin technology can perform, the more parameters to be monitored and controlled. It is therefore necessary to create a place where all data converge in order to be controlled and controlled. A control center is available for this. A very powerful system in particular has a large number of sources of error which must be quickly identified and eliminated. The control should take place via a PLC. The control center should be housed in a vehicle. Instead of the coating device, a spray gun can be connected, which enables the manual coating of surfaces. If, for example, the transport device is not able to pass through sheets, these must be coated by hand. Furthermore, some plants, for example sewage treatment plants, do not only consist of pipes, but also of basins or containers that cannot be coated with the coating device. In this way, all accessible cross sections can be coated.

The insertion length can be increased if booster pumps are used. These booster pumps are fed into the pipe with the supply hose package. In this way, several kilometers of insertion length can theoretically be achieved. For this, however, it appears necessary to use a source of energy other than compressed air, since the pressure losses over such a long distance should become uncontrollable. Electricity seems cheaper.

The coating device shown in Figure 1 can be equipped with additional components with which fillers can be introduced into the spun material.

These fillers can e.g. consist of fibers or granular parts. The introduction of fibers enables the production of a composite material, which - particularly when spinning hard PUR or synthetic resins - can achieve higher static strengths.

The device for this consists of a fiber feed, which consists of a reel and is located outside the tube. The fibers are bound by a flexible hose that is integrated into the feed hose package. A cutter is then attached to the coating device, which cuts the fibers in such a way that they are conveyed into and onto the centrifugal stream

Be surrounded by the mixture.

If the fibers are long enough, it can be assumed that holes or cracks can also be covered in this way. In contrast to the pure material, the fibers do not penetrate the hole, but stick to the edges, because they are wetted with the mixture before they hit it and are longer than the width of the crack. The fibers thus represent an obstacle that cannot be penetrated for subsequent fibers and material and are therefore covered by further fibers. The use of granular fillers is used in industry so that not only the solid plastic has to be used for cost reasons. Furthermore, fillers - like fibers - are suitable for changing the mechanical properties. However, the system required for this requires pneumatic conveying, in which the solids are first conveyed, for example, into a container which is attached to the coating device and then fed into the material flow by means of a screw or the like. This process takes place in exactly the same way as the introduction of fibers described, so that the pumps and other components are not exposed to wear and tear due to the solid load.

The coating of outlets has the disadvantage when using a centrifugal disc that outlets are only coated in the direction of the centrifuge. This is avoided if two disks are used. The direction of centrifugation of a plate is only able to coat one side of an outlet. If two plates with different directions of rotation are used, both sides can be coated so that there is a transition from coating to tube.

List of the reference symbols used

Spin plate

Mixing device

Spin chamber

Hollow shaft

Baffle plate

Carrier disc

Discharge opening

Mixer outlet opening

cone

storage

Storage container for the components of the coating material

pump

Hose package reel pipe to be coated

Traction rope

Hose package

Coating device coated pipe inner surface

Traction device

Claims

claims 1. A method for applying a plastic layer composed of at least two components to the inner surfaces of a hollow body, a coating device introduced into the hollow body Passes through the hollow body and provides it with a coating, characterized in that the components of the plastic, after their mixing within the coating device (18), through the axial conveying speed via a mixer outlet opening (8) within a centrifugal chamber (3) to one opposite the mixer outlet opening (8) Impact the cone (9) and experience an increased acceleration, as a result of which the plastic is distributed more rapidly on a baffle plate (5) and the plastic is flung onto the inside surface of the hollow body via a discharge opening (7). 2. The method according to claim 1, characterized in that the coating of the inner surface of the hollow body is applied in a thick layer of 1 to 20 mm and the coating is carried out with plastics which are formed from highly reactive components which have a thixotropic behavior and pot lives of 0.5 up to 10 s. 3. The method according to any one of the above claims, characterized in that the coating device is pulled through the hollow body and the plastic is accelerated and ejected via baffles arranged within the centrifugal chamber (3). 4. The method according to any one of the above claims, characterized in that the plastic discharged from the discharge opening (7) is additionally mixed with a granular and / or fibrous filler and is fed via a feed and distribution device which is arranged in the immediate vicinity of the coating device is. 5. The method according to any one of the above claims, characterized in that the introduction length of the coating is increased, additional feed pumps being integrated within the hose package. 6. Apparatus for applying a plastic layer composed of at least two components to the inner surfaces of hollow bodies, which comprises at least one mixing device and at least one centrifugal disc connected thereto, characterized in that the mixing device (2) within a rotating hollow shaft (4) of the revolving centrifugal plate (1) is arranged, with the hollow shaft (4) being followed by a centrifugal chamber (3) forming the centrifugal plate (1), which is formed from a baffle plate (5) and a carrier plate (6), wherein Baffle plate (5) and carrier plate (6) are connected to each other by a profiled discharge opening (7) and the baffle plate (5) has a cone (9) directed towards the mixer outlet opening (8). 7. The device according to claim 6, characterized in that the mixing device (2) is self-cleaning and / or has a rinsing device and inside the centrifugal chamber (3) baffles arranged and additional feed pumps are integrated within the hose package. 8. Device according to one of the above claims, characterized in that the centrifugal chamber (3) is double, the centrifugal disc is set at an angle to each other and the outlet openings are preferably designed as interlocking radial arms. 9. Device according to one of the above claims, characterized in that in addition to the coating device on the carrier and a feed Distributing device for granular and / or fibrous fillers is arranged and the coating device is arranged on a transport device.