After more than 20 years' development, Shenzhen Water Affairs Department has five modern water plants and four raw water pumping stations, with a daily water supply capacity of 65,438 0.62 cubic meters, forming a crisscross, safe and reliable water supply network with a total length of about 65,438 0.589 kilometers. As an important equipment in the pipe network, how to better control the quality of valves is becoming more and more important for the management of the pipe network.
I. Selection of valves
First of all, in terms of valve selection, in the early days of the establishment of the Special Zone, the water supply network was less than 10 km, and most of the network used gate valves. Because the pipe network is simple and the gate valve is well sealed, the role of the valve in the pipe network is not very important. In the early 1990s, butterfly valves were widely used all over the country. At that time, the production of butterfly valve in China had just started, and the quality problem of butterfly valve became more and more obvious under the condition that the strength of valve body casting was not high and the sealing performance of valve plate apron was poor. Our company discussed with the construction and development unit and the design unit in time, and finally unanimously decided to classify the valves used in the pipe network according to their diameters: that is, when DN is less than or equal to 400mm, the gate valve is used, and when DN> butterfly valve is used at 400 mm, the main basis of classification is that 90% of the maintenance and management work in the pipe network occurs in the small-diameter pipe network below DN≤400mm, so the valves in the pipe network are required to have good opening and closing tightness. Because of the small caliber, the labor intensity of valve opening and closing is not great. And DN & gt400mm pipe network, the explosion frequency is much lower than that of small-diameter pipe network, and the labor intensity of opening and closing is greatly reduced after using butterfly valves.
After more than ten years of exploration and comparison, our company finally chose the products of Jiangsu Tongshan Valve Factory and Anhui Baihu Valve Factory as small-caliber gate valves, and the products of Tieling Valve Factory, Tanggu Tap Water Valve Factory and Henan Shang Jie Valve Factory as large-caliber butterfly valves. 1998 China water association valve testing data shows that 80% of the valves selected by our company are the same. More than ten years of practical pipe network management work also proved that the valve selection of our company was correct at that time. In view of the problems that often occur in the use and management of valves, our company also put forward corresponding technical requirements in the purchase of valves:
1, valve material requirements
① The valve body and valve plate should be made of ductile iron.
② Valve stem material. The gate valve shall be stainless steel stem (2Cr 13) and the butterfly valve shall be stainless steel embedded stem;
3 nut material. It should be made of cast aluminum brass or cast aluminum bronze, and its hardness and strength are greater than that of the valve stem;
④ Material of sealing surface
A, ordinary wedge gate valve.
The copper ring shall be cast aluminum brass or cast aluminum bronze;
Soft sealing butterfly valve.
The sealing surface is usually made of Ding Qing rubber and EPDM rubber, and reclaimed rubber is strictly prohibited. The sealing material must meet the requirements of health indicators, and the relevant data of anti-aging experiment and wear-resistant experiment shall be marked;
⑤ Valve shaft packing. V-shaped rubber ring or carbon fiber impregnated PTFE packing should be used to ensure good sealing performance and no leakage; In the case of frequent opening and closing, the packing is required to be inactive and not aging, and the sealing effect should be maintained for a long time, at least for ten years or more.
2, the technical requirements of variable speed transmission box
(1) The box body material shall be consistent with the valve body material;
(2) The transmission box should be sealed, which can withstand immersion with a water depth of not less than 3m without leakage;
(3) There is no sundries in the box, and the gear mouth should be protected with grease.
3, the structure of the soft seal butterfly valve technical requirements:
(1) Close the valve clockwise;
(2) The valve body should be equipped with a butterfly plate limit block, and its strength should be greater than the opening torque of the valve;
③ The sealing ring should be fixed on the valve body, and the sealing ring pressure plate should be dovetail pressure plate with reliable anti-loosening measures;
④ The operating end of the valve should be square tenon of standard size, facing the ground;
⑤ The scale line of the opening and closing degree of the valve should be cast on the gearbox cover or the shell of the reversed display panel, and the scale line should be coated with fluorescent powder to show eye-catching.
4. Anti-corrosion measures should be taken for the parts in contact with water flow in the valve body and valve plate, such as spraying powder non-toxic epoxy resin after sand blasting and rust removal.
5. Requirements for valve marks
When the valve leaves the factory, the valve factory should give each valve a fixed number, and its number, valve model, caliber, nominal pressure, valve number, manufacturer and production date should be fixed on the valve body.
Second, the valve before installation inspection
In order to solve the common problems in the use of valves and strictly control the quality of valves put into the pipe network, Shenzhen Water Department set up a valve inspection and operation system, Valve 78 1, in September, 1996, which has been in operation for more than 4 years. The operation of the valve testing center effectively curbed the poor quality valves from flowing into the pipe network, and significantly improved the quality of the valves in the current pipe network. The valve inspection station has done a lot of work for this.
1. Strengthen contact and cooperation with existing valve manufacturers, and make valve inspectors fully understand and master the material, structure and processing technology of valves through technical training. Establish a professional testing team, equipped with perfect testing equipment and skilled testing personnel.
2. Strengthen the inspection content of valves.
① Appearance inspection. The surface of the valve shall be free from defects and cracks, and the valve body shall not burst;
② Valve sealing test. When the valve is closed, the pressure gauge has no leakage and pressure drop under the test pressure of 1. 1MPa. Require both sides of the valve to bear pressure in turn, test separately and open and close for many times to achieve the same effect;
③ Operation flexibility of the valve. When a single person opens and closes the valve many times, it is still flexible and light.
3. After more than four years of valve inspection, we found that unqualified valves accounted for about 20% of the inspection quantity, which greatly put an end to the use of unqualified valves in the pipe network.
Third, the management of valves.
In April 2000, our company promulgated the Regulations on Valve Management of Shenzhen Water Supply (Group) Co., Ltd., as follows:
1. Define the management, responsibilities and functional departments of valves.
The equipment department of the company is the comprehensive management department of valve equipment, including account establishment, valve procurement, warehousing acceptance, allocation and scrapping; Water supply dispatching center is the technical management department of valves in pipe network, including determining technical standards, establishing valve file cards, valve selection, construction and acceptance. All water plants and branches are responsible units for the use, maintenance, repair and management of valves within their respective jurisdictions; Valve testing center is the functional unit of valve testing.
2. Determine the purchasing unit of the valve.
The DN≤400 manual valve invested and purchased by the company shall be ordered by the supply and marketing company, and other valves shall be purchased by the equipment department or entrusted by the equipment department, and other units shall not distribute them. The valves needed for new pipe network or pipe network reconstruction and valve replacement must be approved by the company.
3. When the valves in the pipe network need to be replaced, the replacement unit must fill in the "Approval Form for Valve Replacement of Shenzhen Water Supply (Group) Co., Ltd." and send it to the testing center for testing after approval by relevant departments and competent leaders. After passing the inspection, the replacement unit can only implement it, and the replaced old valve will be sent to the valve inspection station for maintenance. If it can be used normally after maintenance, the valve testing station will report it to the Equipment Department for arrangement. If it is really unusable, the fixed assets shall be scrapped according to the regulations.
4. Valve maintenance
(1) The valves on the municipal pipe network shall be inspected and maintained by the branch at least once every six months.
(2) Valve maintenance is divided into primary maintenance and secondary maintenance:
First-class maintenance: complete the inspection of spare parts of valve transmission system to ensure its normal operation. Open and close the valve every six months. Valve wells are clean and free of water, and each valve file is recorded.
Secondary maintenance: clean the valve drive and add butter; Determine the correct position of valve closing and opening, and adjust the lock to ensure the correct indication;
(3) Remove sundries and accumulated water in the valve well in time to protect the water quality of the pipe network.
(4) The personnel who operate the valve on site shall report in time if they find that the valve cannot be used normally.
After more than ten years' exploration, the valve management of Shenzhen Water Affairs Division is gradually on the right track, and some practices of the company have been affirmed in Shenzhen. We will further sum up our experience, learn from our brothers and strive for a new level of valve management.
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