CN100514021C - Method and device for detecting pipeline leakage - Google Patents

Abstract

The invention relates to a method and a device for detecting leakage of a fluid conveying pipeline. The method comprises the steps that a set of pressure transmitter arranged at each station of the pipeline measures the time difference and the average value of multiple times when pipeline leakage pressure change signals between two stations respectively reach the two stations, and the position of a pipeline leakage point is calculated according to the time difference and the average value; the pressure change signals of each station are subjected to pressure identification cross-over and pump starting processes through the automatic identification signal conversion unit, and the delta value amplification comparison unit which is output by the automatic identification signal conversion unit and controls switching detects the pressure signals of the station entering or the station exiting, and the pressure signals are amplified through the signal amplification driving unit to drive the alarm unit. The method is simple and practical, uses less equipment, saves investment, and particularly only needs to add a small amount of equipment for the operated pipeline. The determination of the location of the leak is not very accurate, but basically meets the practical requirements. Meanwhile, the alarm can be given in real time. And the alarm sensitivity is high, the alarm is accurate and reliable, the automation degree is high, and the operation is simple and convenient.

Description

Method and device for detecting pipeline leaks

technical field

The invention relates to a detection method and device for leakage of a fluid delivery pipeline. It relates to the measurement of fluid pressure and the technical field of piping systems.

Background technique

Fluid pipelines always leak due to various reasons during operation, especially those pipelines that have been in operation for a long time, such as corrosion and perforation, man-made or natural force majeure, etc. It is very important for pipeline operators and managers to grasp the information of perforation and accurate location in time. Therefore, various countries in the world have successively studied various methods and devices for detecting pipeline leakage. For example, the optical fiber detection method developed by the research and development of optical fiber technology, although this technology is reliable in detection and accurate in positioning, it can even perceive the information of excavation and touching pipelines, which can buy more time for troubleshooting. But because it is necessary to lay optical cables along the pipeline, not only the cost is high, but also for the pipelines that have been built, additional excavation and laying of optical cables is required, and the cost is even higher. The former Soviet Union has developed an ultrasonic detection technology that uses leakage to generate ultrasonic phenomena. This technology can also reliably and accurately detect leakage information, only need to install ultrasonic sensors and detection devices at a certain distance. However, it is still necessary to add many ultrasonic sensors and related equipment in addition to the commonly used or installed meters in the fluid pipeline, which still appears to be costly. Wouldn't it be more convenient, simpler, and more economical if there was a kind of instrument that had been installed in the existing fluid pipeline or a common instrument plus a small amount of devices to realize the detection of pipeline leakage?

Contents of the invention

The purpose of the present invention is to invent a simple, convenient, economical, reliable and more accurate detection method and device for fluid pipeline leakage.

When the fluid pipeline leaks, it not only needs to generate ultrasonic waves, but also produces a negative pressure shock wave in the pipeline, which is transmitted to the upper and lower stations by the fluid. According to this characteristic, the present invention realizes the detection of pipeline leakage by using the existing equipment to detect the negative pressure wave in the pipeline as much as possible. When the pipeline leaks, the negative pressure shock wave will be transmitted to the adjacent upper and lower stations——Station A and Station B, which will be sensed by a set of pressure sensors installed in Station A and Station B, and will be displayed on the screen of the station control computer of each station. There are pressure curve changes on the real-time pressure trend graph. Therefore, we can calculate the position of the pipeline leak according to the time difference between the arrival time of the pipeline leakage signal at A and B stations and the average value of the arrival time difference between the two stations; , the clocks of each station should be synchronized, of course, it is better to use one clock. At the same time, the pressure change signal is identified and amplified to drive an alarm. It is very simple to calculate the position of the pipeline leakage according to the time difference of the pressure change of the two stations A and B and the average value of the time difference between the two stations. The formula for calculating the distance from the pump station where the negative pressure wave first appears to the leakage point is:

In the formula: t _{average difference} - the average value (s) of the time difference between negative pressure waves arriving at A and B two stations N times

t ₁ - the time to the first negative pressure wave pumping station (s)

t ₂ —the time of negative pressure wave pumping station after arrival (s)

L—the distance between A and B stations (km)

There will be certain errors in this calculation formula due to the following reasons:

1. Since the fluid in the pipeline has a certain flow velocity, the speed of negative pressure wave transmission upward (reverse) and downward (same direction) will be different, which will cause certain errors in the calculation results, but due to the negative pressure wave in the liquid The speed transmitted in the pipeline is 1000m/s, while the flow rate of the fluid in the pipeline, such as crude oil, is generally about 1m/s, which is negligible for the crude oil pipeline;

2. The time when the leaked negative pressure wave arrives at stations A and B is based on the clock of the station control machine, which requires that the clocks of each station must be consistent. But in fact, the clocks of each station are independent, and need to be timed, corrected and consistent. If the error of the corrected time is large, or the error of the travel time is large, it will bring errors to the calculation results. For example, if the cumulative error is 2s within 24 hours, There is an error of 2000m. Of course, if the existing station control equipment is transformed, all stations use one clock, that would be the best;

3. The pressure curve in the general station control equipment is one scan line per second. Different stations use the mouse to click on the steep drop point of the pressure curve. There will be some errors in time. Even if the operator operates carefully, there will be some errors An error of about plus or minus one scan line will also produce an error of about 2000m.

It can be seen from the above that there will be some errors in this method using the existing station control equipment to detect the location of the leak point, but generally it can be controlled within 5000m, which is of course not very ideal for actually finding the leak point, but it is also possible up.

This method should not only be displayed on the screen display pressure trend graph of the station control machine, but also should have a timely alarm to help remind the operating personnel to deal with it in time. The alarm method for its leak detection is to install a set of pressure transmitters at each intermediate station of the pipeline to measure the incoming and outgoing pressures respectively. As long as there is a negative pressure wave in or out of the station, it means that there is an operation or a leak point. Use the Δ value to amplify and compare the unit to amplify, and amplify the difference to drive the alarm device.

In fact, for the intermediate station, there are pressure overshoot and pump start procedures. In order to distinguish these processes and accurately identify the leaked negative pressure wave signal, this method adopts the method of double input of the inbound and outbound pressure signals, that is, the input of the inbound and outbound pressure signals is compared, and the high-level signal is selected for detection When the pressure exceeds the station process, this can double the alarm accuracy.

According to the method of the present invention, the pipeline leak detection device is also designed based on the utilization of existing equipment as much as possible to minimize investment. This device consists of a pressure transmitter, a safety retainer or distributor that converts the current signal detected by the pressure transmitter into a voltage signal, station control equipment, automatic identification signal conversion unit, Δ value amplification and comparison unit, signal amplification drive unit, It consists of an alarm unit and a power supply unit. Since the realization of pipeline leakage detection consists of two parts: leakage alarm and location determination of the leakage point, and whether the pipeline is newly built or in operation, it generally has pressure detection and station control equipment, so there is no need to set up another set for this device, it is completely possible Use existing equipment. For example, the location of the leakage point can be determined by using the real-time pressure trend graph displayed on the screen of the existing station control computer and a simple calculation software to calculate the location of the leakage point. The pressure detection part of the alarm part of pipeline leakage detection - pressure transmitter, safety retainer or distributor can also use the existing equipment in the pipeline, and only need to set up an automatic identification signal conversion unit, Δ value amplification and comparison unit, The signal amplifying drive unit, the alarm unit and the power supply unit for supplying power to them are enough (as shown in Figure 1). Therefore, the device is simplified as two voltage signal connections that are detected by two pressure transmitters installed on the inbound and outbound pipelines through the safety retainer or the distribution box and then input to the automatic identification signal conversion. The input terminal of the unit, its output is switched by the contact of relay J ₁₀₁ to the input of the Δ value amplification comparison unit, the output of the Δ value amplification comparison unit is connected to the signal amplification drive unit and the alarm unit for alarm, and the power supply unit is converted to the automatic identification signal respectively Unit, delta value amplification and comparison unit, signal amplification drive unit and alarm unit supply power. In addition to the alarm, in order to provide more intuitive observation for the operating personnel, a moving coil instrument drive unit can also be added to drive the pointer instrument to display the trend of the current pressure value. This unit is connected to the output of the Δ value amplification and comparison unit. Also the drive unit is powered by the power supply unit. In order to facilitate the identification of leakage signals and the realization of circuit composition, the input signal of this device comes from the two-way pressure signal of inbound and outbound. It can be seen from Figure 2 that the automatic identification signal conversion unit is composed of a comparison amplifier composed of an operational amplifier and a subsequent The two-stage amplifier is composed of an inbound pressure signal and an outbound pressure signal, and the output is a relay J ₁₀₁ , which amplifies the input of the comparison unit by controlling the Δ value of its contact closure. The Δ value amplification and comparison unit is basically the same two amplifying circuits, except that the input circuit of one of them has an adjustable capacitor, which actually delays the input signal, and the output is a delayed amplified Δ value. The input of the two-way amplifying circuit is a double inbound pressure signal or a double outbound pressure signal. When there is no leakage signal, the signal amplification drive unit has no output, the relay J ₂₀₁ does not work, the input of the Δ value amplification comparison unit is the incoming or outgoing pressure signal, and the Δ value amplification comparison unit has no Δ value change output; when there is leakage Signal (negative pressure signal), the signal amplification drive unit has a Δ value change output, the relay J ₂₀₁ works, its normally open contact is connected, and the normally closed contact is disconnected. When there is a leakage signal, the signal amplifies the drive unit to work, and the normally open contact of the relay J ₂₀₁ is connected to make the alarm unit work. The alarm unit uses an audio oscillator circuit LM556, a power amplifier circuit and a loudspeaker. The input of the driving unit of the moving coil instrument also comes from the output of the Δ value amplification and comparison unit, which is directly amplified by the operational amplifier to drive its load—the moving coil instrument. The power supply unit is a three-level voltage stabilizing circuit after voltage transformation, rectification and filtering, and the output of each level of voltage stabilizing circuit supplies power to a part of the circuit units. This device adopts such a circuit structure, and automatically detects the outlet pressure when the pump is started. Automatically detect the inbound pressure when the pressure exceeds the inbound process. In this way, the alarm accuracy of the pressure overstepping process is doubled, and the disadvantage of alarming once a negative pressure wave enters the station without changing the pressure can be overcome when the pump is started, and the negative pressure signal can be reliably responded and alarmed.

Detailed ways

Embodiment: The present invention will be further described with an example that has been tested and succeeded on the oil pipeline below. This example has been applied to Tieqin crude oil pipeline. Install a pressure transmitter, safety retainer or distributor on the pipelines at the entrance and exit of each intermediate station, and measure the pressure change between the two stations (the negative pressure wave of pipeline leakage) and the signal reaches the two stations respectively. The time of the station (based on the clock of the station controller) and the average of 5 time differences between the two stations, and the distance between the two stations (a certain number), the specific location of the leak can be calculated. The alarm of pipeline leakage (see Figure 2) is identified by the two-way signal of the inbound and outbound pressure through the automatic identification signal conversion unit to detect the inbound or outbound pressure. When there is a negative pressure wave, the Δ value is amplified to drive the alarm unit. Alarm, and also drive the moving coil instrument to indicate the current pressure change trend. The device is assembled according to the electrical schematic diagram shown in Figure 2, and the components are selected according to the marks on the diagram. Among them, the first stage is the automatic identification signal conversion unit, which is amplified by the operational amplifier μpc157A or TA7506M (1), followed by an amplifier composed of two stages of discrete components. The load of the final stage amplifier is the relay J ₁₀₁ , choose HH53P, and choose to switch into the station Or the outbound signal, and send the inbound or outbound signal to the Δ value amplification and comparison unit. The Δ value amplification and comparison unit is composed of two sets of four-stage amplifiers with discrete components. One set of amplifiers is connected with an adjustable large electrolytic capacitor after the input resistor R ₄₀₁ to delay the input, and a small resistor R is connected in parallel with R ₄₀₁ through a manual button. ₄₀₉ , used for the alarm test of the circuit, the input of the two sets of amplifiers is controlled by the relay J ₁₀₁ to get the pressure signal from entering or exiting the station. When there is a negative pressure signal, one channel is amplified in time, and the other channel is amplified after a delay. The output of the Δ value amplification and comparison unit is divided into two channels, and one channel is connected to the comparison and amplification dynamic instrument drive unit composed of the operational amplifier μpc157A to directly drive the dynamic instrument 89C48 The other way is connected to the signal amplification drive unit, which is composed of the comparison amplifier of the operational amplifier μpc157A or TA7506M (1) and the subsequent two-stage discrete component amplifier. The load of the final stage amplifier is the relay J ₂₀₁ , the model is HH53P, the input of the alarm unit is controlled by its contacts. The input of the signal amplification drive unit comes from the output of the amplifier of the Δ value amplification and comparison unit. When there is a negative pressure signal, the Δ value amplified by one amplifier is compared with the delayed and amplified Δ value of the other amplifier, and the difference is added to the signal amplifier drive unit. Push the relay J ₂₀₁ , the normally open contact of J ₂₀₁ is closed, push the relay J ₆₀₂ , the normally open contact is closed to provide power to the alarm unit. The alarm unit uses the audio oscillator integrated circuit LM556 and the power amplifier circuit to drive the speaker Y601 to sound. The power supply unit is composed of a transformer, full-wave rectifier, filter, and stabilized voltage to output 24V to supply power to the automatic identification signal conversion unit, Δ value amplification comparison unit and signal amplification drive unit; the 24V voltage is then supplied to the alarm unit through a three-terminal voltage regulator circuit 7812 Power supply, through 2 voltage stabilizing circuits A ₄ and A ₅ (choose 723HC integrated block) to output +10V each direction automatic identification signal conversion unit A ₁ , the operational amplifier A ₂ of the signal amplification driving unit and the operational amplifier of the moving coil instrument driving unit A ₃ power supply.

The device has been installed and tested on the whole line. The measured alarm accuracy is ΔP↓≥0.025Mpa, and the time t≤150 seconds. As long as there is a perforation or drilling on the pipeline, the device can alarm. The sensitivity can meet the actual needs, the accuracy is high, and it can be automatically identified. , easy to operate. All 4 drilling oil spills have not been missed in more than a year since the device was put into use on the whole line, providing timely and accurate information for timely measures and avoiding greater losses.

It can be seen that the method of the present invention is simple and practical, requires less equipment, and saves investment, especially for pipelines that have already been in operation, only a small amount of equipment needs to be added. Although the determination of the location of the leakage point is not very accurate, it can basically meet the actual needs. At the same time, it can also provide real-time alarm prompts and instrument indications. The alarm device has high alarm sensitivity, is accurate and reliable, has a high degree of automation, and is easy to operate.

Claims (2)

1. A detection method for pipeline leakage, including measuring the time difference between the arrival of pipeline leakage signals at two adjacent stations and the average value of the multiple arrival time differences between the two stations by a set of pressure transmitters installed on the pipeline at each station of the pipeline Calculate the position of the pipeline leakage; after identifying the pressure change signal of each station, the pressure change signal caused by the leakage is detected and amplified to drive the alarm. With a pressure transmitter, the measured incoming and outgoing pressure change signals are recognized by the automatic identification circuit to determine the incoming or outgoing pressure signal, amplify the incoming or outgoing pressure change signal, and drive an alarm. 2. A pipeline leakage detection device according to the pipeline leakage detection method of claim 1, comprising a pressure transmitter, a safety retainer or a distributor for converting the current signal output by the pressure transmitter into a voltage signal, and a station control The device is characterized in that the leakage alarm is composed of an automatic identification signal conversion unit, a Δ value amplification and comparison unit, a signal amplification drive unit, an alarm unit and a power supply unit, and is composed of two pressure detectors installed on the pipeline at the entrance and exit of each station of the pipeline. The transmitter converts the measured pressure change signal into a voltage signal through a safety retainer or a distributor and connects it to the input terminal of the automatic identification signal conversion unit. The unit judges and measures the incoming or outgoing pressure signal, and the output is controlled by _the The contact switch is executed, the input of the Δ value amplification and comparison unit comes from the output of the relay J ₁₀₁ , the output of the Δ value amplification and comparison unit is sent to the alarm through the signal amplification drive unit and the alarm unit, and the power supply unit is respectively sent to the automatic identification signal conversion unit, Δ The value amplification comparison unit, the signal amplification drive unit and the alarm unit are powered.

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