The urban water supply pipe network system is composed of various water supply facilities installed and connected, among which the gates account for the largest proportion of pipe network facilities besides pipelines.
1. Analysis of the status quo of gate management
1.1 Gate pile flooded
Due to urban road expansion, subway, building construction and other projects, it is not uncommon for gates to be buried and lost. There are hundreds of them at least, and thousands of them at most. This is a common phenomenon and problem in every city. This does not include the case where the gate manhole cover is wrong. Taking a certain city as an example, in 2020, the number of buried gate wells increased by 30% compared with 2019. About 1,212 gates could not be found, and more than 60% of the gate inspection wells were located near the urban construction site and were buried more than once. Once the gate is buried or lost, it will cause huge hidden dangers and troubles to the leak detection of the pipe network, rush repair and water stop, and seriously affect the safety of the water supply pipe network.
1.2 Gate opening and closing status
Gate status detection is an important task in daily gate inspection, which directly affects the pressure of the pipe network and the work of water stoppage and repair, and is even related to the reduction of user complaints. Although gate inspections and opening and closing work are being done, due to gate quality, inspections, and opening and closing work not in place, it is difficult to stop water and serious waste always exists. It can be seen that the state of the gate is related to the rapid water stop, the range of water stop, and the control of leakage. For example, in order to repair the pipe network burst in a city, the water cutoff plan involved 1,000 households. As a result, due to valve failure and unclear topological relationship, the water cutoff range affected 3,000 households, resulting in an expansion of the water cutoff area and extended water stoppage time. , resulting in a large amount of water wastage.
In addition, during the process of pipeline network repair, construction, connection, and water stoppage due to arrears, the valves were not opened and closed according to the normal specifications, numbers, and order, resulting in the valves being leaked or not opened enough times, resulting in low water pressure. cause user complaints. For example: A city's water supply service hotline received complaints from users that the pressure of the pipe network in the area was low. The water company immediately sent leak inspectors along the line to investigate, and found that a main valve was closed, and the water pressure returned to normal after the leak inspectors started the valve.
1.3 Valve topological relationship
Gate topological relationship is the difficulty and pain point of gate relationship, and it is also the focus of gate management. The unclear topological relationship not only makes it more difficult to close and isolate areas during the construction of zonal metering, but also affects the speed of emergency maintenance. Although many water companies have built GIS systems, the topological relationship of the gates has not been completely resolved, and the credibility is poor. Often, the water cutoff plan does not match the actual opening and closing of the gates for on-site emergency repairs, resulting in safety accidents.
1.4 Gate inspection and maintenance
The gate inspection is the urban water supply network, but in fact the gate inspection work is not in place, and the gate inspection is not done according to the specifications and requirements, resulting in leakage and damage to the gate from time to time, and the gate inspection work is like a decoration . The gate ledger records are very sound and complete, but they are actually inspected. In fact, from the gate leakage and water accumulation reported by the leak inspectors every month, it can directly reflect whether the gate inspection work has been implemented. If the attitude and sense of responsibility of the inspectors determine the quality of the inspection, then the number of spot checks and supervision determines the reliability of the inspection quality.
1.5 Valve layout, unreasonable
The gate layout and design topology relationship are the difficulties and pain points of the gate relationship, and it is also the focus of gate management. In some old communities, the main water pipeline network has few gates and large spacing, which brings great troubles to the leak detection work of the pipeline network and seriously affects the application of sound detection technology. In addition, when a leak occurs in the pipe network, the scope of water stoppage is large, and the time for water stoppage is long, which prolongs the leakage period.
2. Application of gate management in leakage control
2.1 Effect of gate status on sound detection
It is well known that gate status has a direct effect on sound detection. Leaky gates, insufficient gate openings, or a half-open state all produce sound on the valve body. The sound is very similar to the leakage noise and becomes a source of sound interference, which can easily cause misjudgment or interfere with the leakage detection results of the water supply network. For those with insufficient experience in leak detection, it is easy to ignore the noise of the pipeline network leakage due to the influence of the noise of the valve, resulting in the omission of the leakage point of the pipeline network. In addition, even the pipes with pressure reducing valves installed in the pipe network will also cause interference to the sound of the valve plug and the related location of leaks. It can be seen that strengthening gate maintenance and emergency repair is very important to reduce the impact of gate status on sound detection.
2.2 Basics of Sound Detection
The gate is an important facility and foundation for sound collection and detection, and plays a pivotal role in the leak detection of the pipeline network. The number of gates, their status, and the size of the distance directly affect the sound detection work and determine whether the leak detection work can be carried out. The more reasonable the valve layout and spacing, and the better the condition, the easier it is to carry out the sound detection work. Leak detection personnel can analyze, judge, and track the leakage noise of the pipeline network by listening to the gate, and detect the leakage of the pipeline network. At the same time, it is an indispensable and important infrastructure for correlator and noise recorder to collect the leakage noise of the pipe network. It can be seen that gate management is the key to leakage control of water supply network.
2.3 Temporary partition and step-by-step valve closing to detect leakage clues
Temporary partition is an important means to improve the efficiency of leak detection, shorten the cycle of leak detection, and quickly find leak clues. It has incomparable advantages over carpet leak detection and general inspection. Leak detection personnel can analyze the control area of the pipe network node valves according to the pipe network drawings, and then close the node valves during the minimum flow period from 02:00 to 04:00 at night, and observe the changes in the minimum flow readings of the inlet flowmeter to quickly identify the leaking area or Pipe section. In addition, a portable flowmeter can be used, combined with valve facilities, to temporarily close and isolate a large area into several small temporary areas, and then find leak clues segment by segment by closing the valve step by step.
The step-by-step closed valve detection plays a leading role in the leak detection of urban pipe networks and residential garden pipe networks, especially suitable for the detection of PE pipe leaks in complex environments, difficult leaks and wave-sparse. In the leak detection work, it is often encountered that the leakage clues cannot be found in multiple rows. The leak detection personnel will close the valve step by step, monitor the flow change before and after the valve closing, evaluate and analyze the leakage clues of the pipeline network, and locate the leak point for the sound detection. Provide convenience. In particular, PE pipes have poor sound transmission characteristics and fast sound attenuation, and there is a certain gap between them and metal pipes. You can try to open and close the gate many times to record the changes in the noise of the PE pipe wall to detect the location of the leakage point of the PE pipe.
2.4 Valve leakage
Due to gate cavitation, corrosion, rubber ring sealing, material quality and daily maintenance, and improper replacement, gate leakage and cracking are very frequent. It can be seen from the annual repair work order data of the water company that the maintenance volume of the gate is very large, and the problem of open leakage is not uncommon. It doesn't matter if one gate leaks, the leakage caused by hundreds of thousands of gates should not be underestimated, and the leakage caused by the breakage of individual valves is even greater. For example: In 2020, a city’s water affairs group received a water work order for the road area. After leak detection and on-site investigation, it was determined that the DN100mm gate valve body was cracked.
In addition, in the construction of DMA zoning metering, the isolation and blocking functions of gates play a decisive role in determining the boundary and scope, closing and cutting off the water supply area. The clearer the boundaries of water supply areas, the more conducive it is to assess the difference between production and sales in the area, analyze the minimum flow at night, and facilitate leak control and governance.
3. How to standardize gate management
3.1 Standardize gate inspection management
The gate inspectors arrange the gate inspection plan scientifically and reasonably according to the gate card book. According to the five-determined principles of "fixed area, fixed person, fixed responsibility, fixed time, and fixed line", after checking the type, caliber, place name, direction, address, topography, and coordinates of the gate card position map, (the coordinate line should be selected for a more permanent fixed objects), check the gate well chamber elevation, manhole cover, valve body, well wall, whether there is leakage, siltation, corrosion, subsidence, occupation in the well, whether the manhole cover is wrongly covered, damaged, tilted, whether the plug is missing, and whether it is related to the GIS system information Does it match. Gate inspection is not a process, but a high degree of unity of attitude, experience, sense of responsibility and quality. It can be seen that gate inspections should formulate norms and standards, performance assessment and incentive mechanisms, and improve and improve the supervision and evaluation mechanism in order to truly implement the inspection work .
3.2 Complete and complete gate information
The gate information is not only the gate file, but also the basis for checking, checking and updating the gate. The status information of the gate information is inspected and recorded during the operation of the urban water supply pipeline network, such as: gate number, address, type, control range, gate bolt point map, status of gate leakage, repair status after leakage, etc. Only when the basic data of the pipe network facilities are accurate can a solid foundation be laid for the development of the water supply pipe network. Therefore, gate information management should start from collection, sorting, filing, paper card electronic documents and GIS system correspondence, and real-time update of the gate card directory. At the same time, improve the data borrowing system and handover system to prevent the loss of gate information.
3.3 Sorting out the topological relationship of gates
The topological relationship of the gate is actually a very complicated task, and it takes a lot of opening and closing or closing valve tests to sort out the topological relationship clearly. The reality is that it is unrealistic to shut down the gates frequently and cut off the water supply, which makes the progress of this work slow. Even so, in order to solve the problem, it is still necessary to gradually sort out measures such as water stoppage for emergency repairs and planned water stoppage. For example, in the DMA district metering area of a community in a city in East China, because the topological relationship of the valve is not clear, after the leakage point is repaired, the minimum flow rate at night does not change. Afterwards, through a sluice gate survey, it was found that the water supply pipe network of the community had more than the only entrance. The minimum traffic data of the DMA cell is shown in the figure below.
3.4 Gate detection and chamber cleaning
The problems of siltation, missing, heaping, and occupation of gate wells are closely related to urban road expansion and construction demolition projects. The more major demolition and construction projects, the more serious the buried gate wells will be. If the valve well inspection, detection, and cleaning work cannot keep up, hidden dangers will be buried. These problems have caused great troubles to the emergency repair of the pipe network, water allocation, and leak detection of the pipe network. It can be seen that it is necessary to be equipped with advanced detection equipment such as manhole cover locator and GPS, and to formulate supporting mechanisms for key inspections and assessments, so that the detection of the gate well chamber and the sedimentation cleaning can be done well.
3.5 Optimizing gate layout and design
With the expansion of urban water supply scale and the increase of users, DMA partition metering, smart water projects, pipe network leak detection and scientific dispatching requirements, the original gate layout and design can no longer meet the current needs of the Internet of Things, online monitoring, etc. In addition, the design and layout of the gates did not fully comply with the water supply and drainage design specifications and requirements at the beginning. Perhaps it was to save costs, or it may not have considered the leakage control and partition metering needs of the gates in the long run, which made the gate layout and design deviate from the actual needs. Therefore, the layout and design of gates should be continuously optimized according to the construction needs of actual leakage control, smart water affairs, and zonal metering, so as to meet the needs of various detection and monitoring.