Method for determining value of deposits on inner surface of pipeline and device for its implementation

FIELD: machine building.

SUBSTANCE: pulse heat source with action time of where R - piping radius, d - wall thickness, a -temperature conductivity is installed on pulse heat source piping according to the method for determining the thickness of deposits on inner surface of piping, and temperature change is determined at the distance l=(2.5-3.5)d from the heating source. The device for determining the thickness of deposits on inner surface of piping is equipped with generator of current radio pulses, amplifier, analogue-to-digital converter, computing device, indicator of deposit thickness and indicator of deposit heat conductivity; at that, output of current radio pulse generator is connected to induction coil; amplifier input is connected to temperature sensor output; amplifier output is connected to input of analogue-to-digital converter; output of analogue-to-digital converter is connected to input of computing device; outputs of computing device are connected to indicators.

EFFECT: possibility of monitoring the deposits of small thickness and possibility of monitoring the pipes during performance of preventive actions when the process is stopped and pipes are dehydrated.

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The invention relates to methods of nondestructive testing and can be used on pipelines of oil and gas, chemical and petrochemical plants, thermal and nuclear power plants.

Known methods for determining the thickness of the layer of sediment that occur during operation on internal and external surfaces of pipes, using eddy current devices [1]. The method consists in comparing the signals of the eddy-current sensor for pipes without sediments and sediments, and this comparison is judged on the thickness of the deposits in the pipe.

The disadvantages of this method include the need for a clean tube without sediments, corresponding to its parameters (wall thickness, diameter and specific electrical conductivity of the material) tubes with sediment, which must be monitored.

In addition, there are ways to determine the thickness of the layer on the inner surface of pipelines using ultrasonic equipment. In particular, to such a method include a method of measuring the thickness of the sediment layer on the internal walls of water pipes [2]. The method of determining the thickness of the sediment layer is the measurement of the intensity passed through the pipe ultrasonic vibrations and comparing it with the intensity of ultrasonic vibrations passing through the same pipe, the cover is nnow the same liquid, but not having the sediments, and this comparison is judged on the thickness of the deposits in the pipe and the internal pipe bore pipe. The disadvantages of this method include the complexity of instrumental performance, as well as the need for comparison of the ultrasonic signal passing through the pipe in the presence of sediments, and the signal transmitted through the pipe without deposits. This leads to certain difficulties in the operational implementation of this method. To determine the intensity of the ultrasonic signal through the pipe without deposits to advance to the sedimentation test signal through it or to prepare the same pipe with water, but without the fat.

There are ways [3] determine the thickness reseparating deposits in the pipeline by measuring the magnitude of the convective heat transfer of the transported oil into the environment through the use of two heat-conducting elements (with different coefficients of thermal conductivity)in contact with the surface of the controlled pipeline and calculating the thickness of deposits in the amount of heat flows into the heat-conducting elements. The disadvantages of this method include:

- it is applicable only in the case of filling of the controlled object by the liquid;

- the necessity of using two heat-conducting elements with identical pin chami with the surface of the pipe.

Closest to the proposed technical solution is the method [4] to determine the thickness of deposits on the internal surfaces of piping, including the measurement of the surface temperature of the pipeline, wherein the pipeline coaxially with it installed heat source in the form of a ring, remove the temperature gradient in the direction from the heat source along the pipeline on its surface, which is judged on the size of deposits inside the pipes.

A device that implements the specified method [4], contains a source of heat in the form of a ring mounted coaxially on the pipeline, and temperature sensors located at some distance from the heat source.

The disadvantages of this method of determining the thickness of sediments on the inner surface of the pipe, inside of which there is fluid flow, is the fact that this method is unsuitable:

a) for control of thin-walled pipes with a small thickness of the deposits;

b) for inspection of pipelines that are not liquid or it is fixed, as is the case for some objects.

The objective of the proposed technical solution is the ability to control deposits of small thickness (from 50 microns and above) and control of pipelines during periods of preventive measures when stopping the process design and dehydrated pipelines, as is the case in the nuclear industry.

The problem is solved in that in the known method of determining the thickness of deposits on the internal surface of the pipeline, including the measurement of the surface temperature of the pipe from the heat source in the form of a ring mounted coaxially with the pipeline, determining the change in temperature on its surface, which is judged on the size of deposits inside the pipeline, according to the invention the temperature influence exercised by pulse heating during the timewhere R is the radius of the pipe, d is the wall thickness,andthermal diffusivity of the material of the pipe, and determining the change in temperature is carried out at a distance l=(2,5-3,5)d from the heat source.

In addition, the device for determining the thickness of deposits on the internal surface of the pipeline containing the heat source in the form of a narrow ring, placed on the outer surface of the pipe coaxial with it, the temperature sensor located on the surface of the pipeline, at some distance from the heat source, according to the invention the heat source is made in the form of a coil of the inductor, the width of which m is chosen equal to m=R/10, the distance from the temperature sensor to the extreme spiral inductor is chosen equal to l=(2.5÷3.5)d, where d is the thickness of the pipeline wall, the device SN is Breno generator of radio current amplifier, analog-to-digital Converter, a computing device, an indicator of the thickness of the sediments and indicator of thermal conductivity, while the output of the generator of impulses of current connected to the coil of the inductor, the input of the amplifier connected to the output of the temperature sensor, the output of the amplifier to the input of the analog-to-digital Converter, the output of the analog-to-digital Converter to the input of the computing device, the outputs of the computing device is connected to the indicators.

The essence of the method is illustrated by drawings. Figure 1 - arrangement of narrow rings of heating, temperature sensor, located on the surface of the pipeline at the point at which to measure the temporal process temperature changes, which is judged on the size of deposits inside the pipe. Figure 2 - pulse shape by heat, figure 3 - sample thermogram (the time dependence of the temperature change ΔT(t)) for different values of deposits β. 4 is a structural diagram of a device that implements the proposed method. Figure 5 - the shape of the current pulse. Figure 6 - difference curves for different values of deposits of β with respect to thermogram of the pipeline without deposits. Fig.7. dependence of the maximum value of the temperature differential of the curve δ tmand the interval τMwhere δt reaches the maximum value Delta t mfor different values of the thickness and thermal conductivity.

The method is as follows. Through installed coaxially on the testing pipeline 1 narrow heating ring 2 (figure 1) produce instant (from the point of view of transient thermal processes) the effects of temperature δ tN(heat 2) duration τNmuch less than the characteristic time of the arising of transient thermal processes(R is the radius of the pipe, d is the wall thickness,andthermal diffusivity of the material of the pipeline). Heat wave (heat) is distributed from the narrow annular zone effects in both directions (figure 1). At a distance l=(2.5÷3.5)d from the ring area 2 such that a propagating thermal wave depends on the thickness β deposits 4 (figure 1), a temperature sensor 5. Figure 1-3 shows thermograms (time dependence of temperature changes) δ t(t) at a heating pipe made of stainless steel with an external diameter of 12 mm, a wall thickness of 1.5 mm On the shape of the curve ΔT(t) is judged on the thickness of the deposits inside the pipe. This assessment allows you to quickly determine the presence and thickness of the deposits on the maximum value of the temperature change and the time when this occurs.

Thus, the proposed method can reduce the error ODA is dividing the thickness of sediments of different nature, to expand the realm of possibility of its application and to raise the efficiency of the technical execution. Through installed at a distance l=(2.5÷3.5)d from the ring heating temperature sensor (figure 4) fix a temporary process changes in temperature, which is judged on the amount of deposits inside the pipe.

The structural scheme of the device that implements the proposed method is depicted in figure 4. The device comprises a generator 1 of impulses of current, the inductive coil is the inductor 2, the temperature sensor 3, the amplifier 4, the amplitude-to-digital Converter 5, the computing device 6, the indicators thickness of sediments 7 and thermal conductivity 8. As a working body figure 4 shows the test pipe 9. The device operates as follows.

The device implements pulse heating pipe 9 by means of eddy currents induced in the material of the pipe short lengths(R is the radius of the tube) coil-inductor 2, which circulate powerful radio pulses of current i (figure 5), duration(where R is the radius, d is the thickness of the pipeline wall,andthermal diffusivity of the material of the pipeline), from the generator 1 of the current impulses. The frequency f of the filling of radio figure 5 must be such as to provide a uniform depth of heating of the wall of the pipe is wire (d is the wall thickness, µo- magnetic constant, σ and µrspecific conductivity and relative permeability of the material of the pipeline). The signal of sensor 3 temperature (thermocouple, surface temperature measuring unit on the basis of pyroelectric ceramics and the like)that is installed on the pipeline at a distance of l=(2.5÷3.5)d from extreme wrap coil-inductor, is amplified by pulse amplifier 4 and through an analog-to-digital Converter 5 is supplied to the computing device 6 (a personal computer, a microprocessor). Using obtained experimentally or by using mathematical modeling data in the memory of the computing device 6 stores the captured image (as in figure 3) for pipes without sediment and sediment thickness β with wall thickness equal to the wall thickness of the controlled pipeline. Using dependency (figure 3) it is possible to determine the presence and thickness of sediments. To more accurately determine the thickness of β in the memory of the computing device 6 stores the differential curves δ t=δ t(t, β=0)-ΔT(t, β) (6). With increasing thickness of the deposits of β increases the maximum value of δ tmand the interval τMwhere δt reaches a maximum value Delta tm. These values in the axes δ tmand τMbuild dependencies for different values of thickness and Ude is Inoi thermal conductivity (Fig.7), because thermal processes, of course, depend on the value of thermal conductivity λ of the material deposits. Curve at λ=0.55 W/(m·K) corresponds to the average value of thermal conductivity of the material deposits, the curves for λ=0.66 W/(m·K) and λ=0.44 W/(m·K) cover the range of possible changes of thermal conductivity of the material of the sediments corresponding to the different operating conditions of the pipe. Thus, for values of δ tmand τMobtained for the test pipe, get through interpolation of the values of the thickness of deposits of β and thermal conductivity of the material that is of interest to technologists-operatives and is another advantage of the claimed method and device. Dependence shown in figure 3, 6, 7, can be obtained by experiments (which is cumbersome) or simulation (as shown in figure 3, 6, 7 data).

The advantage of the proposed methods and devices to determine the thickness of sediment in the pipes in comparison with the prototype is that it is not necessary preliminary measurements of thermophysical characteristics of the sediments and the method is implemented and in the absence of fluid in the pipeline.

By obtained by measuring the display (as in figure 3) is calculated differential cu is the first (as in Fig.6) and obtained values of δ t maxand τmaxusing the memory of the computing device 6 data (type 7) are determined by the thicknesses and thermal conductivity of sediments collected indicators 7, 8.

The method and apparatus can be implemented to control sediment on the outer surface of the piping by using a heater and coil inside a pipeline.

Sources of information

1. Patent US 7405558 B2, date 29.07.2008.

2. Patent RU 02098754 C1, M CL G01B 17/2, 12.10.1997,

3. Patent RU 2099632 C1 IPC F17D 3/00, 20.12.1997,

4. Patent RU 2344338 C1 IPC F17D G01B 17/02, 16.05.2007,

1. The method of determining the thickness of deposits on the internal surface of the pipeline, including the measurement of the surface temperature of the pipe from the heat source in the form of a ring mounted coaxially with the pipeline, determining the change in temperature on its surface, which is judged on the size of deposits inside the pipe, characterized in that the temperature impact exercise pulse heating over time
,
where R is the radius of the pipe, d is the wall thickness;andthermal diffusivity of the material of the pipe, and determining the change in temperature is carried out at a distance l=(2,5÷3,5)d from the heat source.

2. A device for determining the thickness of sediments on the inner surface of Truboprovod, the content is ASEE the heat source in the form of a narrow ring, placed on the outer surface of the pipe coaxially with her, temperature sensor, located on the pipe surface at some distance from the heat source, wherein the heat source is made in the form of a coil of the inductor, the width of which t is chosen equal to m=R/10, the distance from the temperature sensor to the extreme spiral inductor is chosen equal to l=(2,5÷3,5)d
where d is the thickness of the pipe wall, the device is equipped with a generator of radio power amplifier, analog-to-digital Converter, a computing device, an indicator of the thickness of the sediments and indicator of thermal conductivity, while the output of the generator of impulses of current connected to the coil of the inductor, the input of the amplifier connected to the output of the temperature sensor, the output of the amplifier to the input of the analog-to-digital Converter, the output of the analog-to-digital Converter to the input of the computing device, the outputs of the computing device is connected to the indicators.



 

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