JPS58206371A - Method for cleaning internal wall of pipe - Google Patents

Abstract

PURPOSE:To greatly enhance the scale-removing grinding power of quartz sands when applied to cleaning the internal wall of a pipe, by pulsating at constant period and pulsation factor the velocity of the mixed fluid of quartz sand and air flowing through the interior of a pipe to be treated. CONSTITUTION:A vane wheel 13 of a pulsation generator E for the mixed fluid provided at one end of a pipe to be treated 6 is rotated by a drive unit 14, and the velocity of the mixed fluid D of quartz sand and air being pressed into the interior of the pipe to be treated 6 at a constant rate from an accelerating injector is thereby caused to pulsate at constant period and pulsation factor. By virtue of this pulsation, the scale-removing grinding power of the quartz sands 3 in the mixed fluid D is greatly enhanced, and cleaning the internal wall of the pipe to be treated 6 is thus enabled at high efficiency with a small supply of air.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for grinding scale, etc. on the inner wall of the pipe by pumping a mixed fluid of air and silica sand (solid-gas two-phase flow) into the pipe. This relates to improvements in cleaning methods.

In general, in water supply mains and water supply pipes in housing complexes, etc., scale adheres to the inner walls of the pipes over time, causing various problems.

On the other hand, in order to avoid problems caused by scale as described above, the applicant had previously developed a method for cleaning the inner wall of the pipe, in which a mixed fluid of air and silica sand was injected into the pipe, thereby grinding the inner wall surface of the pipe. Japanese Unexamined Patent Publication No. 55-4185
This is published as issue 2.

Figure 1 shows an overview of the cleaning method according to JP-A No. 55-41852 written in +4iJ, in which 41 sand 3 (No. 3 to 6, 10 to 40 mesh) in a sand tank 2 is cleaned by compressed air from a compressor 1. ) is extruded from the mixing ejector 4 side, and at the same time, air and silica sand are mixed in the ejector 4 to form a silica sand flow C. Next, compressed air A is added to the silica sand flow C using an accelerating injector 5,
The structure is such that the scale S fixed to the inner wall surface of the pipe is sequentially ground by pumping a mixed fluid stream of air in a high-speed state and Il and I sand into the vibro to be treated. still,
In FIG. 1, 7 is a drain separator, 8 is a pressure regulator, 9.10 is a water mixer, 11 is a sand recovery device, and 12 is a flow meter.

The above-mentioned -L method can be applied to small-diameter pipes, and the inner wall surface of the pipe can be finished into a smooth mirror-like surface, so it has extremely excellent practical utility.

However, as the pipe diameter increases to the 4B side, the amount of air required to circulate crushed sand at high speed increases considerably, causing many problems in terms of air supply.

For example, in the case of pipe 11 diameter or 3B, 27 to 30 n
? The problem is that it requires a large amount of air, and the compressed air source is large, which poses a major constraint on construction work.

Therefore, in the cleaning method shown in Figure 1,
The flow velocity of the mixed fluid p of 41=sand and air in the pipe is 50 to 1
00WVec has been reached, and the flow of the mixed fluid, which is a solid-gas two-phase flow, is turbulent. As a result, this condition
The flow velocity distribution of the mixed fluid (average flow velocity Vm) in the direction perpendicular to the pipe axis is as shown in Figure 2, where the flow velocity V' near the inner wall of the pipe is relatively small, and the flow velocity at the center of the pipe is low. V is V
It's quite large compared to '\.

ing.

On the other hand, grinding of the scale S fixed on the inner wall surface 6a of the tube is mainly performed by the silica sand grains 3 flying along the inner wall surface 6a of the tube, and therefore, the flow velocity V' near the inner wall surface of the tube has a large influence. In other words, what is directly related to scale grinding is the air flow velocity V' near the inner wall of the pipe, and no matter how much air is pumped into the pipe, V' is low and only the flow velocity V at the center of the pipe is large. In this case, the result is that the amount of grinding I--less effective air and wasted air--is increased.

Furthermore, the frictional force of the crushed sand 3 in the mixed fluid flowing in the pipe against the inner wall of the pipe is relatively higher when the flow velocity is pulsating than when the mixed fluid flows through the pipe at a constant flow velocity. As a result, when the uniform flow velocity Vm is the same, the grinding efficiency is improved more when the pulsation is added to the flow velocity of the mixed fluid by 1jλ.

The present inventor focused on the above-mentioned flow velocity distribution of the M mixture of air and crushed sand in the pipe, and the phenomenon of improving the grinding action by pulsating the flow velocity of the mixed fluid,
The idea was that by pulsating the flow rate of the mixed fluid stream with an appropriate pulsation rate and period, it would be possible to grind scales with a smaller amount of air. Then, they conducted grinding tests on a large number of test tubes having different lengths and diameters, and from the results, they learned the present invention.

In the present invention, the crushed sand is mixed with a high-speed airflow to form a 1ift sandflow, and the mixed fluid (1), which is accelerated by adding high-speed air to the river, is forced into the pipe inner wall Q to be washed into the vibro. ) Cleaning method: The flow rate of the mixed fluid I) flowing in the vibro is pulsated at a constant period and pulsation rate, and the pipe inner wall surface 6a is ground by the pulsating flow of the mixed fluid I). It is composed of a board book,
With this configuration, the air flow rate required for ω1 cutting is reduced by 20 to 4
It becomes possible to reduce it by 0%.

Hereinafter, details will be explained based on an embodiment of the present invention shown in Figures 3 [1 to 5].

FIG. 3 shows a mixed fluid pulsation generator E suitable for carrying out the present invention, in which an impeller 1 is installed at the end of the pipe 6 to be treated.
3 is rotatably supported on a shaft, and the impeller 13 is connected to a drive device 14.
Rotate at a speed of 0.5 to IQ rps. The outer diameter of the impeller 13 is formed to be slightly smaller than the inner diameter Q of the pipe, and by rotating the impeller 13, the mixed fluid pumped from the tip of the pipe 1 in the pipe is rotated. The i17 uniform flow velocity vm pulsates as shown in FIG. The frequency of +'tiI pulsation is approximately 5 to 2Qllz, which is the most desirable value, and the pulsation rate ((V+nmax
-V+nm1n)/Vm) is optimally about 0.2 to 0.5.

Depending on the experimental results, the mixed fluid in the pipe (mainly air flow)
When the flow velocity Vm is made to pulsate at a frequency IQ Ilz and a pulsation rate of 0.2, the speed-up time domain, for example, is the mixing in the direction perpendicular to the pipe axis at point A (flow velocity Vm -Vm) in Fig. 4. The velocity distribution of the fluid is as shown in Fig. 5, and the velocity distribution near the inner wall of the pipe 6
The ratio (+) between the flow velocity V' at a and the flow velocity V at the center of the tube is approximately 0.9
So, when the flow rate is Vm = Vm and there is no pulsation (-
= 0.7~0.8'') compared to the flow velocity V near the pipe wall
′ is increased, and the grinding ability of the scale is greatly improved. It should be noted that in the deceleration time range, for example at point B in Figure 4, the grinding force decreases as the flow velocity decreases, or the grinding ability in the speed increase time range decreases. Therefore, the overall grinding capacity is greatly improved, and if the scale conditions of the pipe 6 to be processed are the same, the amount of air required will be significantly greater than in the case where the mixed fluid stream is not pulsated. Decrease. For example, a 3B (75 units) straight pipe 80m (
When cleaning a scale with an average thickness of 10 to 15 wm by the conventional method, it is necessary to pressurize an air amount of 27 to 30 cm for about 120 to 150 minutes.

On the other hand, according to the present invention, 22 to 2511/,
By press-fitting for 120 to 150 minutes with an air flow rate of #, pipes under the same conditions can be cleaned to the same degree of cleanliness, and the required air amount is reduced by approximately 20 to 25%.

In FIG. 3, the pulsation generating device E is provided on the tube bed of the tube 6 to be treated, but it is also possible to provide the pulsation generating device E on the tip side of the tube 6. Further, in this embodiment, an impeller-type pulsation generator is used, but a solenoid valve mechanism spring may be used instead of the impeller, and the solenoid valve may be controlled to turn on and off at a constant cycle.

Furthermore, in the above embodiment, as shown in FIG. 3, a mixed fluid of air and crushed sand is injected into the tube 6 to be treated at a constant flow rate from the accelerating injector 5, and the flow path at the end of the tube 6 to be treated is filled. By changing the cross-sectional area, the velocity of the mixed fluid inside the pipe is made to pulsate.The air flow iA applied to the accelerating injector 5 itself is made to pulsate, thereby causing the flow velocity of the mixed fluid jetted into the pipe 6 to pulsate. (Alternatively, the air iA added to the accelerating injector 5 is constant,
By periodically changing the supply of the silica sand flow C from the mixing ejector 4 mixed into the mixed fluid I), the flow velocity of the mixed fluid I) injected into the pipe 6 may be made to pulsate.

As mentioned above, the present invention makes the flow velocity of the mixed fluid 1) (solid gas-phase flow) of crushed sand and air flowing in the pipe 6 to be treated pulsating at a constant period and a pulsation rate of 7. The scale grinding force of the crushed sand 3 in the mixed fluid I) is greatly improved, and the inner wall surface of the pipe can be cleaned with high efficiency even with less air supply.

As mentioned above, the present invention has excellent practical utility.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the first method of cleaning the inner wall of the pipe, and FIG. 2 is a distribution diagram of the air flow velocity within the pipe in that case (average flow velocity Vm). FIG. 3 is a schematic diagram of a mixed fluid pulsation generator suitable for implementing the present invention, and FIG. 4 shows a pulsation state of the mixed fluid. FIG. 5 is a flow velocity distribution diagram in the pipe at point A in FIG. 4 when the mixed fluid is pulsated. A Acceleration air C Silica sand flow D Mixed fluid E Pulsation generator 1 Compressor 2 Sand tank 3 Silica sand 4 Mixing ejector 5 Acceleration injector 6 Treated pipe 13 Impeller wheel 14 Rotary drive device Patent applicant Representative of Japan Plant Service Center Co., Ltd. Person Kiyonori Niino and 2 others Figure 2 Figure 3 Figure 4 Figure 4 Flow-〇

Claims (1)

[Claims] In a method for cleaning the inner wall of a pipe in which a mixed fluid of silica sand and high-speed airflow is forced into a pipe to be cleaned, the flow velocity of the mixed fluid flowing through the pipe is pulsated at a constant cycle and pulsation rate. A method for cleaning an inner wall of a pipe, characterized in that the inner wall surface of the pipe is ground by a pulsating flow of the mixed fluid.