BG100349A - Method for cleaning the interior surfaces of tubes and a device for its materialization - Google Patents

Abstract

The method is primarily intended for the cleaning of heat exchanger pipes. A working fluid is passed through the purged tube (10) and is operated on its inner surface by a hydraulic shock wave initiated by an electrical discharge created by means (6) for providing a discharge gap which moves into the interior of the pipe according to the degree of its cleansing. The optimal voltage of the electric discharge is chosen according to a certain dependence.

Description

Technical field

The invention relates to a technique for cleaning the surface of contaminated articles and more specifically to a method of cleaning the inner surface of pipes and a device for its implementation.

BACKGROUND OF THE INVENTION

During operation, the inner surfaces of pipes, such as pipes of heat exchangers, are contaminated with various deposits, which impair the performance of the apparatus "in which they are used. Different methods and devices are used to separate the deposits.

In particular, a method for cleaning the inner surface of pipes (SU 1315037 A) is known, wherein the strip of the pipe is filled with working fluid and electrical discharges are created simultaneously at both ends of the pipe. These discharges initiate shock waves in the liquid, destroying the deposits on the inner surface of the pipe.

The apparatus embodying the known method comprises two electric discharge transmitters, each comprising two electrodes, partially coated with insulation, and also pressure sensors connected to the recording apparatus unit.

However, the known method and device are only applicable for the cleaning of short length pipes due to the radiator's limited radius of action. In addition, the device is characterized by low productivity, since in order to carry out the cleaning it is necessary to dismantle the contaminated pipes beforehand and place them in a working fluid bath.

Also known is a method for cleaning internal surfaces (WO 91/01183), which consists in the fact that a working fluid is transported through the pipe, an electric discharge is created inside the pipe, which initiates a shock wave in the liquid, affecting the internal cleaning agent. surface from the wall of the pipe and capable of destroying its deposits.

Electrical discharge is carried out by discharging the capacitor batteries at a discharge interval, whereby the means providing a discharge interval are moved along the length of the tube, depending on the degree of cleaning.

However, in the present method, the optimal voltage of the electric discharge, which depends on many factors, including the material and size of the cleaned pipe, is not determined. If the amplitude of the voltage pulse is chosen less than the optimum, then several pulses need to be produced to clean the tube, which leads to unnecessary energy losses. If the amplitude of the impulse is greater than the optimum, not only the scum and deposits, but also the walls of the pipe can be destroyed.

The apparatus for carrying out the known method comprises a pulsed power source, the poles of which are coupled to the electrodes of the discharge interval means provided with a device for its displacement into the pipe along its length. In this case, one of the electrodes is pulsed in the form of a exposed part of a cable wire inserted into the tube and connected to the positive pole of the current source. The role of the second electrode is fulfilled by the cleaned tube, which is connected to the negative pole of the source and is grounded.

In this method and device, the electrical discharge originates from the wire of the cable on the inner wall of the pipe, which results in intense corrosion of the walls, which, upon cleaning, appear rough. Once the heat exchanger is put into operation, the rough surface of the pipe is quickly covered with scum and other deposits.

Some pipes are coated internally with special coatings, such as fluoroplasts, to reduce roughness or to protect against corrosion. Cleaning such pipes with known devices causes damage to this coating, which is unacceptable.

The technical nature of the invention

It is an object of the present invention to provide such a method for cleaning the inner surface of pipes, which eliminates the destruction and damage of the walls of the pipes during the cleaning process and which does not require major energy losses for its implementation, as well as and creating a device for implementing such a method that is constructively simple and reliable to operate.

This problem is solved by a method for cleaning the inner surface of pipes, which consists in the fact that working fluid is transported through the pipe, carried out inside the pipe.

an electric discharge (discharge), which initiates in the liquid a shock wave affecting the inner surface of the walls of the pipe and capable of destroying the deposits therein, whereby the electric discharge is created by the discharge path of a capacitor battery at a discharge interval and the means of providing the discharge interval is moved down the tube depending on the degree of cleaning. According to the invention, the electric discharge voltage is selected according to the dependence:

Vo <

where

Kg - dynamic coefficient of resistance of the pipe material;

(J - statistical limit of plasticity of the pipe material;

- pipe wall thickness;

d - inner radius of the pipe;

L - inductance of the discharge circuit of the capacitor batteries;

- the length of the discharge interval;

c - capacity of the capacitor batteries;

density of the working fluid.

In order to reduce energy losses, it is appropriate to select the frequency of successive electrical discharges in the range 0.5 - 3 Hz.

The problem is also solved by a device for cleaning the inner surfaces of pipes containing a pulsed power source, the poles of which are connected to electrodes, means for providing a discharge interval equipped with a device for its displacement in the pipe along its length. According to the invention, a two-core cable is used as a means of securing the discharge interval.

For a circular tube, the coaxial construction of the cable is optimal, in which the central core is connected to the positive pole of the power source and the inner core (braid) to the negative pole.

The method of cleaning the inner surface of tubes carried out in accordance with the present invention allows cleaning with a maximum allowable discharge voltage without damaging the tube (no residual deformation).

When using the device to carry out the method, the electrical discharge to generate electro-hydraulic shock occurs not between the electrode and the pipe walls, but between the two strands of the cable, which prevents damage to the pipe walls.

The device according to the invention is characterized by its simplicity of construction and reliability in operation.

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Brief description of the drawing

The invention is illustrated by a description of a specific variant of its implementation and an attached drawing, which schematically depicts a device for cleaning the inner surface of pipes.

The schematic representation of the drawing comprises: a pulse power source 1, in the present example, a pulse current generator comprising a step-up transformer 2 connected to its output coil rectifier 3, connected in turn to the capacitor battery 4, and so also controlled switch 5 plugged into the generator output circuit.

The power source 1 also includes a controllable electric switch 6 connected in series to the primary winding of the boost transformer 2. The control input of the switch 6 is connected to the output of the control unit (not shown).

A means 7 for providing the discharge interval, in this case a section of coaxial cable, is connected to the poles of the impulse power source 1, in which case the cable core 8 acts as one of the electrodes of the means 7 and connected to the positive pole of the source

1. The outer strand 9 (braid) acts as a second electrode and is connected to the negative pole of the source 1.

The means 7 is provided with a device 10 for moving it down the axis of the pipe, for example a flexible drive connected to a clutch, mechanical or manual (not shown in the drawing).

The condenser battery 4 may be made on the basis of one or more pulse capacitors, depending on the diameter of the cleaned tube and the required power of the generator.

As a switch 5, for example, a control trigatron may be used, the control input of which is connected to a pulse monitored sensor, for example a timer (not shown in the drawing).

The electric switch 6 can be executed on the basis of two thyristors, as shown in the drawing.

In the described embodiment of the device, a coaxial cable is used as the means 7 for providing the discharge interval, however, as a means 7, a non-coaxial two-core cable section can be successfully used.

The method for cleaning the inner surface of tubes according to the invention is understood by describing the operation of the device shown in the drawing.

The device works as follows:

A means for securing the discharge interval is disposed in a tube 11 near one of its ends. Through tube 11 it is transported, in the example described on the side of. the opposite end of pipe 11, the working fluid, for example, running water (the direction of the flowing fluid flow is indicated by arrows).

The optimum voltage amplitude and frequency of successive pulses of electrical discharge are pre-determined.

When cleaning the pipe, it is necessary to select such an amplitude of the shock wave occurring at the electrical discharge in the liquid, which would destroy scale and other deposits and would not damage the pipe itself, ie. the amplitude of the impulse pressure in the pipe must not be higher than the dynamic plasticity limit of the material from which the walls of the pipe are made.

The voltage amplitude of the electric discharge is selected according to the dependence:

where

Kg - dynamic coefficient of resistance of the pipe material;

- static ductility limit of the pipe material; - $ - pipe wall thickness; d - inner radius of the pipe;

L - inductance of the discharge circuit of the capacitor battery;

- the length of the discharge interval;

C - capacity of the capacitor battery;

J3 - plasticity of the working fluid (for water = 1 and in the calculation of the voltage value can be omitted). The reduced dependence, based on the geometry of the tube (r,), the material plasticity limit of the tube (Kd, ί) and the parameters of the discharge circuit (C, L, L) allows to determine the maximum allowable voltage of the capacitor battery, whereby the pipe is not damaged (no residual deformation).

In the case of an electric discharge, a pulse pressure is generated in the tube filled with liquid, under which the water is expelled from the discharge zone and forms a strip unfilled with water. If the interval between the discharges is less than the time D t _o of filling the formed strip with water, then the discharge originates in a gas (air) medium and, therefore, the amplitude of the pulse pressure arising is much smaller than

the pressure amplitude in the case of a discharge in a liquid. Therefore, even though the power consumed by the network is increasing, the amplitude of the shock wave is decreasing.

If the same intellectual! is greater than DD t (the time interval required to fill the forming strip), then the purification performance is less than when t = E t _o . Obviously, with the increase in e t> At _{o, the} performance of the eyepiece will decrease.

Therefore, there is a preferred frequency range of sequential pulses at which the pipe cleaning performance is highest. It is experimentally determined that the frequency range f = 0.5-3 Hz is preferred.

Changing the setpoints of the voltage sensor of the control unit sets the magnitude of the signal received at the input of the thyristor control - switch 6, which provides the necessary value of the voltage amplitude of the electric discharge, leaving the timer at a set frequency ζ ~ ££ ^the impulse sequence at which the generator is connected to the network. In this case, electric discharges occur between the cores and 9 of the cable in the discharge interval, initiating (causing) shock waves in the liquid medium, which destroy and crush the scale and other deposits 12. The flow of water directed to pipe 1L. it washes away the crushed scale from it, and the cable, by the degree of destruction of the scale, moves inward into the pipe towards its opposite I end in the direction of flow of liquid. ?

For a better understanding of the nature of the present invention, an example of its implementation is given below.

Example 1

The parameters of the discharge circuit for scaling of brass pipes with outer diameter 16 mm and wall thickness 1 mm were determined. The capacitance of the capacitor battery is C = 20 Mkt, L = 3000 nG, r = 7 mt, L = 2 mt, b * = 0.35.10 'Pa, Kg = 2.3. Then the maximum allowable voltage is obtained by the formula, at which the purification V _o = 3.05 kV should be carried out. Experimental studies on the cleaning of such pipes have shown that at a voltage of V _Q = 3.0 kV, the pipes are cleaned from scum without any residual deformation. At a scale thickness of 1-1.5 mm, the cleaning speed is 2-3 m / min.

Example 2

The parameters of the discharge contour for scaling of stainless steel pipes with outer diameter 38 mm, wall thickness 0 = 1.5 mm, C = 10 Mkf, b = 3000 nG, g = 17.5 mm, 1 = 6 mm, (1 = 0.4.10 'Pa, Kg = 2.3 The maximum allowable voltage defined by the formula is 7.12 kV.

Experiments have shown that the cleaning of the above-mentioned tubes with an internal diameter of 35 mm at V _o = 7 kV was carried out without any residual deformation.

Thus, the proposed method and device for cleaning the inner surface of the pipes allow to prevent the destruction and damage of the surface of the pipe walls during the cleaning process.

Industrial applicability

The present invention is intended primarily for cleaning the inner surface of pipes used in various technological processes in heat exchangers.

Claims (4)

CLAIMS OF CLAIMS 1. A method for cleaning the inner surface of tubes, wherein a working fluid is transported through the tube, an electric discharge is created inside the tube, initiating a shock wave in the fluid affecting the inner surface of the tube to be cleaned, and capable of destroying adjacent deposits, whereby the electric discharge is effected by discharging a capacitor battery at a discharge interval and the means for providing a discharge interval is moved down the tube according to the degree of its purification, characterized in that the voltage of the electric discharge is selected in accordance with the dependence: where Kd - dynamic coefficient of resistance of the pipe material; (j - statistical limit of plasticity of the pipe material [N / t ² }] β - thickness of the pipe wall [t]; d is the inner radius of the pipe [t]; L - inductance of the capacitor battery discharge circuit [Hz]; I is the length of the discharge interval [t]; I C - capacity of the capacitor battery [ф]; J) - density of the working fluid [kg / m ³ ]. A method according to claim 1, characterized in that a series of electrical discharges are generated by the degree of displacement of the means providing the discharge interval in the pipe, whereby the frequency of electrical discharges is selected in the range 0.5-3 Hz. 3. A device for cleaning the inner surface of pipes containing a pulse source (1) for power supply, the poles of which are connected by means (7) providing a discharge interval equipped with a device (10) for moving it into the pipe (11). its length, characterized in that a two-core cable is used as the means of providing the discharge interval. Device according to claim 3, characterized in that the cable is coaxial, wherein its central core (8) is connected to the positive pole of the source (1) for supply and the inner core (9) is connected to the negative pole .