Common Methods for Leak Detection in Subdivision Underground Pipelines

Tap water carried by underground pipes in small communities may leak over a long period of time, and when a leak occurs, no signs may be found on the surface. Even if water is seeping from the surface, the seepage point is not necessarily the leak point, especially if the ground is covered with a layer such as cement.

There are many methods currently used to detect leaks in underground pipes: static listening and acoustic vibration methods, or what we commonly refer to as pipe leak detection/leak detectors, for which the different methods have their own advantages and disadvantages. The following are several underground pipeline leak detection methods for your reference, I hope you can help.

1、View

As the high water content of the soil around the leak point, low cohesion, often occurring air settlement, so you can presume the leak point.

2、Experimental methods

There are many kinds. Here are some examples.

1. Stop the physical magnetization of water quality. After continuing for a period of time, stop the drainage and stop the analysis of the abnormal area using the magnetization detection equipment along the line.

2. Induced polarization method: This method is usually used to find water in poor waters. The key to this method lies in the scientific processing, analysis and discrimination of the actual data measured.

3. Open metal table: This is a standing weapon for checking rags. It is mainly used to find open ferrous metal items, but can also guess the location of the leak according to its strength.

4. Common utility pipe detector used by power companies: This device can stop imaging the utility pipe, and the leak site is obviously different from other parts.

3. In addition to this, construction materials need to be consulted. Based on the construction records related to the construction drawings, identify thin sections with a high likelihood of leaks and use the following methods to check for leaks.

1. Area list method

This means that in an area of the water network, the difference between the flow meter entering the area and the flow meter leaving the area must be a non-metering loss in that area. If there is no other non-metering consumption, you can know the leakage losses in that area, which will be "in the mind" of the manager. The more densely divided the zone, the clearer the division, the clearer the knowledge of the leakage in each section. However, meters should not be installed too densely. This method does not determine the exact location of leaks and cannot be used as a basis for specific repairs and breaks in the pavement.

Point: Leakage leads to poor measurement.

2. Hearing method and sound vibration method

The hearing method refers to listening to the sound of water leakage with certain sound transmission tools, and judging the location of the leakage according to the size and sound quality characteristics of the sound of the leakage. From a simple mechanical listening stick to a variety of leak monitors, this method should essentially be called the vibration method. Currently, it is rapidly evolving. It is a common and effective method applied both domestically and internationally, and is the method mainly introduced in this manual. Related leak detectors should also belong to the sound vibration method system.

Focus: Leakage can cause vibration and sound effects.

In general, the basic detection method is, connect the host, headphones, and sensors. Turn on the switch, put on the headphones, place the sensor on the road above the pipeline, place it step by step according to the length of the pace, and listen to it step by step, the closer to the leak, the stronger the signal, the farther away from the leak the weaker the signal, and achieve the purpose of detecting the leak by comparing the signal strength between different points. Therefore, we use the instrument, a single point to listen to the leak signal is not meaningful, to multi-point repeatedly compared, compared with the sound vibration of the larger place is the leak, of course, we have to consider many other additional factors, such as the direction of the leak breakage mouth, because the pipe is round, if the side of the leak, may be larger points instead in the side of the road above the pipe, rather than being the pipe Above the road, so the location of the pipeline to know, in addition to the tee, bend, water pressure, burial depth, buried layer, etc. will have an impact on the detection of these to take into account.

3. Infrared method.

Infrared thermal imaging detection is the use of photoelectric technology to detect the infrared specific waveband signal of the thermal radiation of the object, the signal is converted into human visual distinguishable images and graphics, infrared scanning measurement of the pipe network area. When groundwater seepage occurs, it will create a temperature difference between the local area and the surrounding area, and the infrared radiation will be different. The infrared image will reflect this difference. Using this difference, we can find leak points. It is important to note that due to subsurface drainage, standing water may vary depending on other factors. IR radiation may also be caused by non-leakage factors, so the application of this method is also limited.

Key point: Leakage causes local variation of IR radiation (temperature effect).

4. Relevance of leak detection

In principle, it is a transposition technique based on the acoustic vibration method, which is an acoustic vibration method. The vibration caused by the leak point propagates along the pipe to both sides. Sensors placed at different distances on both sides will have a time difference when they receive the sound wave from the leak point at a certain moment. This time difference is determined by the speed of sound in the pipe and the location of the leak point. It has the outstanding advantage that it can transmit sound well using the pipeline. It can measure directly on the official path and calculate the fixing point by the instrument, eliminating the human experience factor. It also avoids the problem of the tester having to keep the instrument above the measurement point. The practical difficulty lies in the condition constraints. Placement of the transducer must have two direct contact points and be very clear about the state of the pipe: including routing, bending, pipe diameter in different pipe sound propagation speed and sound propagation conditions are good. Another factor is expensive and has certain technical requirements for the operator's computer application. At present, there are a variety of foreign models of relevant detectors, which are sold in the domestic market and have many applications in large domestic water supply companies. However, due to the lack of specialized detection points in China's pipeline network and poor conditions, the application is quite inconvenient and the results are not satisfactory, and cannot replace other detection means to fully complete the detection task.