The water supply network is made up of various pipeline accessories and fittings such as pipes and valves. According to various needs, such as the amount of water in the network, the scheduling and deployment of water pressure, the need to stop the water for maintenance, the connection of old and new pipelines, the flushing of pipelines, etc., the valves have to be opened and closed every day. The service life and quality of the valve determines the normal operation of the network, plays a pivotal role in the network, must be given great attention.
Because the network is a bridge between the water supply enterprises and the majority of users, so to speak: a water supply enterprise management is reflected in the normal operation of the network; and the normal operation of the water supply network, and the valve life and quality is closely related.
The safety of water supply
Does not affect the water quality is an important indicator of valve selection. The part of the valve in direct contact with the water is mainly the inside of the valve body, the sealing part, the valve plate, etc. At present, many manufacturers produce the sealing part of the valve using rubber materials. Commonly used rubber materials are nitrile rubber (NBR), chloroprene rubber (CR) or ethylene propylene rubber (EPDM). These rubbers are all synthetic rubbers. In the synthesis process, more than ten kinds of raw materials and additives such as anti-aging agents are added to the natural rubber. The final synthetic rubber can be used to seal the water supply valve, we must see whether this rubber is non-toxic, whether it meets the drinking water hygiene standards. As for the inside of the valve and the valve plate and other parts, many manufacturers used to use the method of painting, considering only the problem of rust prevention, without considering whether it is toxic.
In practice, we found that: in the water supply network, the problem of anti-corrosion lining of pipes is solved, while the valves of the network are not lined, due to the phenomenon of water sedimentation and the erosion and deposition of iron bacteria in the water on the inner cavity of the valve and the valve plate, resulting in the phenomenon of mounding on the inner wall of some valves.
Not only affects the water quality of the water supply, but also is one of the main reasons why some valves do not close tightly. Therefore, we require that these parts in direct contact with water should be sprayed with non-toxic coating, preferably with non-toxic epoxy powder by electrostatic spraying method. When we choose the valve, we should first check whether it has the proof of non-toxic rubber and coating and inspection certificate, only the valve with the above conditions can ensure that the water quality is not polluted and the safety of water supply is guaranteed.
The advanced technology
The production technology of the valve is constantly developing, from the old gate valve to the soft seal gate valve, from the initial butterfly valve to the wafer type butterfly valve, single eccentric, double eccentric flange butterfly valve, hard seal butterfly valve, from the traditional single head exhaust valve to the high speed double orifice exhaust valve, etc.. Therefore, the advanced nature of the selected valve should also be taken into consideration when selecting the valve. However, in the application of new technology, we oppose the practice of indiscriminately, without understanding the actual user, and a flurry of new technology and new technology should be combined with the needs of the user.
Good valves are to be in the production of practical applications, from the direct needs of users. For example: the resin extrusion sealing method, although from the design ideas and factory tests proved that it does have advantages. However, in actual use, due to resin materials, extruded resin tools, etc., it does not solve the problem of how the user can use it. When users use such valves, they do not appreciate the advanced nature, characteristics and advantages of such valves, and use them as samitary butterfly valves. Therefore, valve production should pay attention to both its advancedness and its practicality. And pay attention to solving the problems in practical applications, such as: exhaust valve float ball material, float ball shape (spherical or cylindrical) on the exhaust effect and how the life of the study. How to prevent the worm gear worm butterfly valve operation control problems, the gearbox of the box top broken problem, the labeling of the switch indication and so on. Therefore, the selection of the valve must pay attention to its technical advancement and practicality.
Sealing of water flow
Whether the valve plays a sealing role is the basic requirement for the valve. In practice, there are various types of seals, such as soft seal, hard seal, valve plate seal, valve body seal, surface seal, line seal, etc.. No matter what kind of seal form is used, it cannot affect the sealing effect. In the past, we have used a part of the valve plate seal butterfly valve, theoretically speaking, the biggest advantage of this butterfly valve is that once the seal rubber ring fails, there is no need to disassemble the valve, and it can be replaced online. However, in the actual application of water supply enterprises, the advantages of this kind of butterfly valve are difficult to be reflected. Therefore, if the rubber ring is replaced online, it is not only necessary to disassemble the pipes at both ends of the valve and empty the water from the pipes.
At the same time, the replacement rubber ring cannot be tested for sealing, and the replacement effect cannot be determined. Therefore, when selecting a valve, it is important to pay attention to the sealing form of the valve and check the sealing effect of the valve in conjunction with the respective practical application.
Authenticity of the test
The manufacturer of the valve must be required to provide a true and accurate inspection report. These inspection reports include.
- the inspection of raw materials – the composition content of C, Si, Mn, P, S, etc. in the raw iron and the quality of coke, etc.
- inspection of castings – metallographic test, elongation test, strength test, etc.
- seal test – double-sided pumping test and multiple switching test, etc.
- aspects such as health and quarantine reports for rubber and health and quarantine reports for paint. Products produced by companies that provide untrue inspection reports cannot be used.
Reliability of quality
The good ring of valve quality is reflected in the whole process of valve manufacturing.
- the original iron matching.
- the manufacture of sand molds.
- the casting of iron casting.
- the accuracy of machining, etc.
To have a more complete set of quality assurance system. The significance of the indicator of how many times the valve is opened and closed is not necessarily to meet the test of more than five thousand times the switch. Because the valves in the pipe network is not often switched on and off. Sometimes, some valves are switched on and off only once in ten or eight years.
Flexibility of operation
Whether the valve operation is flexible is very important. Operation flexibility is not only reflected in the choice of which transmission method, but also in the processing accuracy of the parts related to the transmission mechanism. For example, in the butterfly valve transmission mode. There are generally two types of transmission – screw nut type and worm gear type.
The general screw nut type is characterized by slow at both ends and fast in the middle when switching, which is better for operation, but because of the small dynamic torque of the screw, it is not easy for the operator to grasp the opening and closing degree of the valve plate when operating, and it is easy to happen that the valve has been closed while still operating to make the screw twist and break. And worm gear worm type is generally easy to close the overposition. At the same time, the sealing of the gate valve stem, butterfly valve transmission parts of the speed and torque of the matching problem is the valve operation of the most difficult problem. Therefore, the choice of which transmission method should be based on the situation of each water supply enterprises, after listening to the views of the operator, and the manufacturer to work closely, so that the choice of valves can be operated flexibly, but also to meet the needs of use and work.
Establish a perfect inspection and re-inspection system
When a water supply enterprise, after several visits, research and after a certain range of tests, and finally selected one or several valve manufacturers, issued to its products allowed to enter the local water supply market after the pass, it means that the water supply enterprises and valve manufacturers to establish a relationship between supply and demand.
At the same time, the valve manufacturer to the water supply enterprises to ensure a safe and reliable water supply also assume joint and several responsibilities. On the one hand, the valve manufacturer is required to consistently provide high-quality products in accordance with the requirements of the water supply enterprises. On the other hand, to ensure quality also requires water supply enterprises to set manufacturers to establish the necessary, more complete regular inspection and re-inspection system, generally 2 to 5 years is appropriate.
The fixed-point manufacturers of people, machines, materials, methods, environmental and other five elements of the regular inspection and evaluation. Water supply enterprises in the manufacturer’s inspection at the same time, should also be based on the use of the unit valve, the original technical conditions for the necessary revisions and additions.