JPH0446381B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a pipeline inspection device using a pig that detects at an early stage the occurrence of minute cracks, thinning due to wear or corrosion, or occurrence of minute leaks in pipelines, etc. It is.

<Prior art> In this type of pipeline inspection, an inspection pig equipped with sensors such as ultrasonic contacts and measurement equipment consisting of an amplifier circuit, arithmetic circuit, memory, power supply, etc. is propelled by the fluid inside the pipe. We perform non-destructive testing such as wall thickness measurement and flaw detection.

In addition to detection data, information on the location of such a test pig is also important, and conventionally the following method has been adopted.

() Detect circumferential welds, bent pipes, etc. using the eddy current method and record them along with the detected data. After the inspection, the positions will be determined by comparing the positions of circumferential welds and bent pipes recorded in the construction records.

() Ultrasonic waves are transmitted from the tube end into the tube, the delay time of the waves reflected by the pig is measured, and the pig position is determined using the pre-measured propagation speed.

() Install a wire reel on the departure side and connect one end of the wire to the pig. The length of the wire stretched as the pig advances is determined by measuring the number of rotations of the reel, and the position is determined.

() Attach a speed detection wheel to the pig, press this wheel against the pipe wall, measure the number of rotations of the wheel that rotates as the pig travels, and use the circumference of the wheel to determine the distance traveled by the pig. Confirm the position.

() Give the PIG the ability to transmit two types of signals to the ground, such as lines of magnetic force with different frequencies.
If the pig inspects the inside of the pipe and the result is normal, it will send one signal, and if it detects an abnormality in the pipe, it will send the other signal.
Transmit for a certain period of time. This is received on the ground along the railway line to confirm the position.

<Problems to be Solved by the Invention> The conventional techniques described above have the following problems and have not been put to practical use.

() Eddy current method A complex detection mechanism is required to perform the eddy current method, and fairly detailed construction records must be kept. In particular, the latter is difficult to expect with old piping that requires inspection.

() Ultrasonic method The transmitted ultrasonic waves are reflected not only by the pig but also by curved pipes and T-shaped tubes, making it difficult to distinguish between the former and the latter, and considering the attenuation of the waves. The distance seems to be a few hundred meters.

() Wire method When a pig travels a long distance, it becomes necessary to pull a long wire, and it is difficult to obtain such a large traction force from the fluid. The need arose;
It becomes difficult. Therefore, with this method, pig travel is limited to several hundred meters at most.

() Speed detection wheels It is possible to minimize the slippage between the wheels and the pipe wall in straight pipe sections by appropriately selecting the material and pressing force of the wheels, but it is possible to minimize the slippage between the wheels and the pipe wall in branch pipes and merging pipes. Since the cross-sectional shape of the channel changes, the contact between the wheels and the tube wall may be incomplete or absent, resulting in length measurement errors. Furthermore, when a phenomenon in which the pig rotates around the tube axis occurs, the locus of the wheel becomes spiral, and its length becomes longer than the traveling distance of the pig, which also causes an error. Furthermore, since the installation of such wheels complicates the pig, it is virtually impossible to apply it to pigs for small diameter pipelines such as 3 to 6B.

() Pig transmission method There are major limitations in its application because it requires that the test circuits and sensors built into the pig be unaffected by the transmitted signal, and that the ground along the railway line can be used.

The present invention was proposed to solve the above-mentioned problems, and its purpose is to provide a pipeline inspection device that has a relatively simple configuration and can easily determine the position of a pig.

<Means and effects for solving the problems> The pipeline inspection device according to the present invention is made of synthetic resin such as polyurethane, has high flexibility and sealing properties, and is propelled by receiving fluid in the pipe from a fluid power source such as a pump. and an inspection pig equipped with measuring equipment that non-destructively inspects the pipeline from the inside while being driven by the driving pig.
Consisting of a flowmeter that measures the flow rate of fluid discharged from a fluid power source and a means for measuring the pig position from the flow rate of the flowmeter, it is capable of grasping the pig position X from the flow rate at each time t and measuring the differential pig. The device is configured to store test results or abnormality detection times at each time.

<Examples> The present invention will be described below based on illustrated examples. As shown in FIG. 1, a pig launcher 4 is connected to the starting end of the pipeline P via an on-off valve 3, and a pump 5 as a fluid driving source.
A pressure feed pipe 6 is connected thereto, and the pressure feed pipe 6 is provided with a flow meter 7 and a branch pipe 8.

A driving pig 1 is propelled and travels by receiving fluid in the pipe from a pump 5, and an inspection pig 2 is attached to this driving pig 1.
are connected via a bendable joint 9.

The driving pig 1 is made of semi-rigid urethane foam or a material coated with a wear-resistant resin, and is a highly flexible pig with high sealing performance.

For example, the diameter of pig 1 is about 1 to 4 mm larger than the pipe diameter in the case of a pipe of about φ80, and about 5 to 10 mm larger in the case of a pipe of about φ200, so that the volume of the fluid that has displaced pig 1 is The sealing performance is said to be approximately 1% of (pig travel distance) x (pipe cross-sectional area).

As shown in FIG. 7, the inspection pig 2 has a large number of disc-shaped substrates 10 stacked one on top of the other at intervals in the longitudinal direction inside the main body, and is designed to be miniaturized.
It is equipped with measuring equipment 11 such as a clock, an amplifier circuit, an arithmetic circuit, a memory, and a power supply, and records leakage sound, pipe wall thickness, and pipe defect detection.

In the above configuration, since the driving pig 1 with high sealing performance is used, the total amount of fluid pumped from the time of starting the pig is approximately equal to the volume inside the pipe from the starting point 0 to the pig. By measuring the total pumping amount with the flow meter 7, the position of the drive pig 1 at each time t can be determined, and furthermore, the position of the inspection pig 2 connected thereto can also be determined.

In addition, inspection pig 2 has a built-in clock, sensor,
The inspection result or abnormality detection time at each time t is stored using the amplification/arithmetic circuit, memory, and power supply, and by comparing this with the pig position at each time t described above, the inspection result or pipe at each position of the pipeline is stored. It is possible to know the location of abnormality occurrence in the line.

Furthermore, in detail, the amount Q that flowed through the line from time to when the pig passed the starting point O to time t
is expressed as Q=∫ ^t _tp qdt (1). Here, q is the flow rate at each time.

On the other hand, if the position of the pig at time t (measured along the line from the starting point) is x, the intratubal volume V from the starting point of the pig to x is expressed as V=∫ ^x _p Adx (2). Here, A is the internal cross-sectional area of the pipe at each position.

In (1) and (2), q can be measured by the flowmeter 7, A is known from the design and construction results, and if there is no leakage from the pig, Q = V ... (3) holds, so each time The pig position x at time t can be accurately determined.

However, in reality, error factors include flow rate measurement errors, variations in the cross-sectional area of pipes due to pipe dimensional tolerances, leakage from pigs, and expansion and contraction of fluid due to temperature changes in the pipeline.

(a) Regarding flow rate measurement error The measurement error by the flow meter 7 varies from about 0.3 to 2% depending on the type of flow meter and maintenance status.
However, its linearity and short-term zero point drift are extremely small, estimated to be around 0.1 to 0.3%. Therefore, by performing the correction described later, the error can be kept within about 0.1 to 0.3% of the correction interval.

(b) Fluctuations in the internal cross-sectional area of the pipe The internal cross-sectional area of the pipe is due to dimensional tolerances during pipe manufacturing, the formation of deposits inside the pipe, wear of the pipe, etc. Of these, most can be removed by passing it through a cleaning pig equipped with a wire brush or the like before inspection. The tube diameter tolerance is guaranteed to be within ±1% considering flatness, and the circumference is said to be highly accurate. Even if there is some flattening, the internal cross-sectional area of the tube hardly changes. In addition, although the difference between the curved pipe section and the straight pipe section is large, it is thought that the variation depending on the position of several meters is small.

Therefore, the variation in the cross-sectional area of the pipe is at least 1
It can be considered less than %.

(c) Regarding leakage from pigs Leakage from polyurethane pigs occurs in normal piping.
If n pieces are connected and used, it is considered to be within 1/√%.

(d) Expansion and contraction of fluid due to temperature change When the fluid is a gas For a gas, when the temperature changes by 1°C, the specific gravity decreases by approximately
Changes by 0.3%. For this reason, if it is expected that there will be large temperature differences depending on the location of the pipeline due to contact between the above-ground part and the buried part, this effect cannot be ignored.

Therefore, as shown in Fig. 6, the inspection pig 2
A fluid temperature measurement system 12 is provided at the pipeline to measure and correct temperature changes at each location in the pipeline.

The temperature measurement error here is considered to be about 2° C. even when the influence of the temperature distribution in the cross section inside the pipe is taken into account, so the error due to temperature change can be suppressed to 1% or less.

When the fluid is a liquid, when the temperature of a liquid changes by 1℃, it changes by 0.01 for water.
There is a specific gravity fluctuation of 0.02% and 0.1% for oil. With water, this is rarely a problem, but with oil, if the temperature difference is about 10°C, it must be considered as a cause of error. In this case as well, the error can be suppressed to 0.3% or less by taking the measures described above.

From the above, the error in specifying the pig position is approximately 1.8% of the pig travel distance [(a): 0.3% (b): 1% (c): 1%
(d): 1%]. In order to reduce the absolute value of this estimation error, the following correction is performed.

In general, pipeline inspections need to be carried out in units of several kilometers, but since the departure and arrival times of the pigs can be known, the relationship between the time measured based on the departure time and the pig position (4 ) can be corrected using the arrival time.

x=f(t)...(4) x=l/l'f(ta)...(5) ta: arrival time, l: location of arrival point Furthermore, the section where the pipeline inspection is performed is divided, By measuring the elapsed time of the pig at the dividing point using an ultrasonic echo detector, etc., the above-mentioned error can be reduced by l・ε
can be reduced to li·ε (ε: error, li: interval length of the i-th divided interval).

In other words, the aforementioned error is 1.8% [(a): 0.3%,
(b): 1%, (c) 1%, (d) 1%], in order to suppress the positioning error within ±5 m, it is sufficient to detect the passage of the pig every 280 m.

Note that one drive pig 1 and one inspection pig 2 are used, and they are connected by a bendable joint 9 (the first
(see figure), but is not limited to this, as shown in Figures 2 to 5, multiple pigs 1 and 2 are used, joint 9
The test pig 2 may be pushed by the drive pig 1 without using the drive pig 1.

Figure 2 shows a driving pig 1 placed in front and behind an inspection pig 2, where the inspection pig 2 is pushed by the rear driving pig 1 on horizontal and uphill sections, and moves faster than the fluid on downhill sections. The test pig 2 attempting to move is held back by the front drive pig 1 to a speed comparable to the fluid speed.

In FIG. 3, the drive pig 1 is arranged only at the rear, and the inspection pig 2 is propelled.

In FIGS. 4 and 5, the driving pigs 1 in FIGS. 1 and 2 are arranged in multiple units to improve sealing performance and move the driving pigs 1 at a speed equal to the velocity of the fluid.

<Effects of the Invention> As described above, according to the present invention, a drive pig with high flexibility and sealing performance is used, the flow rate of fluid from a fluid drive source is measured by a flowmeter, and the pig position is determined from the flow rate at each time. At the same time, the inspection results at each time or the abnormality detection time are stored in the measuring device of the inspection pig, and by comparing the two, it is possible to know the inspection results at each position in the pipeline or the position where an abnormality occurs in the pipeline. It produces an effect like.

() The position of the pig can be easily determined with a relatively simple configuration.

() Drive pigs are used for internal cleaning, drainage, fluid replacement, etc. of pipelines, and have a proven track record for diameters of 10 mm or more.If the inspection pig is downsized as shown in Figure 7, it can be used for 3B to 6B. It is applicable to small diameter pipelines.

() The leakage of the drive pig can be suppressed to about 1% by selecting an appropriate diameter and material, so assuming that this leakage is uniform along the entire line, the error in determining the position will be a fraction of the amount of leakage. 1 to number + 1/1
Therefore, the error in determining the position can be in the range of several meters to several + meters when traveling several kilometers. Also,
Correcting various errors improves position determination accuracy. Furthermore, sealing performance can be improved by using multiple drive pigs.

() It can be applied to long distances of several kilometers from ().

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing a pipeline inspection device according to the present invention, Figs. 2 to 5 are schematic diagrams with different pig configurations, Fig. 6 is a schematic diagram with a temperature measurement system added, and Fig. 7 FIG. 2 is a longitudinal sectional view showing an example of an inspection pig. 1... Drive pig, 2... Inspection pig, 3... Open/close valve, 4... Pig launcher, 5... Pump, 6...
...Pressure pipe, 7...Flowmeter, 8...Branch pipe, 9...
Joint, 10... Board, 11... Measuring equipment,
12...Fluid temperature measurement system, P...Pipeline.

Claims (1)

[Scope of Claims] 1. A driving pig that has high flexibility and sealing properties and is propelled and travels by receiving fluid in the pipe from a fluid power source, and a pipeline that is equipped with measuring equipment and that travels while being driven by the driving pig. An inspection pig for non-destructively inspecting the inside of the fluid, a flow meter for measuring the flow rate of fluid discharged from the fluid power source, and a means for estimating the pig position from the flow rate of the flow meter. Pipeline inspection equipment.