How To Choose The Valve In The Water Supply Network?

- Aug 14, 2019-

Water supply network is composed of various pipe accessories and fittings such as pipes and valves. According to various needs (water quantity of pipe network, water pressure regulation and allocation, water shut-off need for maintenance and repair, connection of new and old pipelines, flushing of pipelines, etc.), the valve should be opened and closed every day. The service life and quality of the valves determine the normal operation of the pipeline network, which plays a decisive role in the pipeline network and must be given high attention.

As the pipeline network is a bridge between water supply enterprises and users, it can be said that the management of a water supply enterprise is reflected in the normal operation of the pipeline network, and the normal operation of the water supply network is closely related to the life and quality of the valve.

Safety of water supply

Water quality is not affected by valve selection is an important indicator. The part of the valve directly contacting with water is mainly the inner part of the valve body, the sealing part, the valve plate and so on. At present, the sealing part of the valve manufactured by many manufacturers is made of rubber material. The commonly used rubber materials are nitrile butadiene rubber (NBR), chloroprene rubber (CR) or ethylene propylene dines rubber (EPDM). These rubbers are synthetic rubber. In the synthesis process, more than ten kinds of raw materials and anti-aging additives should be added to the natural rubber. Whether the final synthetic rubber can be used for sealing water supply valves depends on whether the rubber is non-toxic and meets the hygienic standards for drinking water. As for the inner part of the valve and the valve plate, many manufacturers used to paint, only considering the problem of anti-rust, without considering the toxicity. In practice, we find that in water supply network, the problem of anti-corrosion of pipeline lining has been solved, but the valve of pipeline network has no inner lining. Because of the precipitation of water and the erosion and deposition of iron bacteria in water on the valve chamber and valve plate, hilly accumulation phenomenon appears on the inner wall of some valves. It not only affects the water quality of water supply, but also is one of the main reasons for the inadequate closure of some valves. Therefore, we require that these parts which are in direct contact with water should be sprayed with non-toxic coatings, preferably with electrostatic spraying method to spray non-toxic epoxy powder. When choosing valves, we should first check whether there are no toxicity certificates and inspection certificates for rubber and paint. Only valves with the above conditions can ensure the water quality is not polluted and the safety of water supply.

Advancement of Technology

Butterfly valve

With the continuous development of valve production technology, from the old gate valve to the soft seal gate valve, from the original butterfly valve to the clamp butterfly valve, single eccentricity, double eccentricity flange butterfly valve, hard seal butterfly valve, from the traditional single-end exhaust valve to high-speed double-orifice exhaust valve, etc. Therefore, the selection of valves should also take into account the advanced nature of the selected valves. However, in the application of new technology, we oppose the practice of not distinguishing, not knowing the actual situation of users, but combining new technology and new technology with the needs of users. Good valves are obtained from the direct needs of users in the practical application of production. For example: resin extrusion sealing method, although from the design ideas and factory tests prove that it does have advantages. However, in actual use, due to resin materials, extrusion tools, etc., the problem of how to use users has not been solved. When users use this kind of valve, they will not realize the advance, characteristics and advantages of this kind of valve, but use it as a common butterfly valve. Therefore, valve production should not only pay attention to its advanced nature, but also to its practicability. And pay attention to solving practical problems, such as: exhaust valve float ball material; float ball shape (spherical or cylindrical) on the exhaust effect and service life of how to study. How to prevent the operation and control of worm and worm butterfly valve (closing over position), the top crushing of gearbox box, the indication of switch, etc. Therefore, the choice of valves must pay attention to its technological advancement and practicability.

Seal ability of water flow

Whether the valve plays a sealing role is the basic requirement of the valve. In practical applications, there are many types of seals, such as soft seals, hard seals, valve plate seals, body seals, surface seals, and line seals and so on. No matter what type of seal is used, the sealing effect cannot be affected. In the past, we have used some butterfly valves with plate seals. In theory, the greatest advantage of this kind of butterfly valve is that once the sealing ring fails, it can be replaced online without disassembling and assembling the valve. However, in the practical application of water supply enterprises, the advantages of this butterfly valve are difficult to reflect. Therefore, if the rubber ring is replaced online, it is not only necessary to dismantle the pipeline at both ends of the valve, but also to empty the water in the pipeline. At the same time, the sealing test of the replaced rubber ring cannot be carried out, and the replacement effect cannot be determined. Therefore, when choosing the valve, we must pay attention to the sealing form of the valve, and check the sealing effect of the valve according to their practical application.

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The authenticity of the test

Valve manufacturers must be required to provide real and accurate inspection reports. These inspection reports include:

1. Examination of raw materials - the content of C, Si, MN, P, S in raw iron and the quality of coke, etc.

2. Casting inspection - Metallographic test, elongation test, strength test, etc.

3. Sealing test - double-side pump pressure test and multiple switch test, etc.

4. Hygienic quarantine reports of rubber and coatings. The products produced by enterprises that provide untrue inspection reports are not usable.

Reliability of quality

A good ring of valve quality is embodied in the whole process of valve manufacturing.

1. Selection of raw iron;

2. Manufacture of sand molds;

3. Hot metal casting of castings;

4. Machining accuracy, etc.

A more complete quality assurance system should be established. The indicator of the number of valve switches is of little significance and does not necessarily need to satisfy the test of more than 5,000 switches. Because the valves in the pipe network are not always switched on and off. Sometimes, some valves only turn on and off once every ten or eight years. In our practical work, we found that the positioning screw on butterfly valve is loose when it is installed, and some of them have no bolt screw at all.

Operational flexibility

Flexibility of valve operation is very important. Flexible operation, not only reflected in the choice of which transmission mode, but also reflected in the accuracy of parts related to the transmission mechanism. For example, in the transmission mode of butterfly valve. Generally there are two transmission modes - screw nut type and worm gear type. Generally, the characteristics of the screw nut type are slow at both ends, fast in the middle and easy to operate. However, due to the small dynamic moment of the screw, it is not easy for the operator to grasp the opening and closing degree of the valve plate during operation, and it is easy for the valve to be closed and the screw to be distorted and broken during operation. The worm gear and worm type are easy to close and over position. At the same time, the sealing problem of gate valve stem and the matching of rotating speed and rotating moment of butterfly valve transmission parts are always difficult problems in valve operation. Therefore, the choice of transmission mode should be based on the situation of water supply enterprises, listen to the opinions of operators, and closely cooperate with manufacturers, so that the selected valve can operate flexibly and meet the needs of use and work.Rationality of price

Valves should have a reasonable price; reasonable price is not necessarily the lowest price. If only pay attention to the lowest price, it is easy to mislead manufacturers in order to promote their own products, competing to lower prices, or even lower than the cost price of the product sales, manufacturers in order not to lose money will inevitably have to cut corners in the process, materials, the production of valves there are quality risks, used in the water supply network, and ultimately suffer. It's the user himself. Therefore, we must pay attention to the selection of valves, encourage manufacturers to use value engineering principles, strengthen the main functions, remove redundant functions, optimize system functions. Work hard on management and cost accounting. It should be pointed out that a reasonable price can be the lowest price, but the lowest price is not necessarily a reasonable price.

Guarantee of after-sales service

When the valve is used in the water supply network, there will be some problems, some of which belong to the valve itself, some of which come from external factors such as disturbance, broken rings, brutal construction, illegal operation, poor management and use, etc. However, no matter what the reason, valve problems will affect the operation of the pipeline network, all need the cooperation of manufacturers, so valve manufacturers need to have a good after-sales service guarantee when selecting valves. Once the valve has problems, it can arrive at the site in the shortest time and solve the problems as soon as possible.

Consistency between order and supply

The consistency here refers to the consistency between the valve products produced by the valve manufacturer and the products required by the water supply enterprise. This requires the joint efforts of the ordered and the supplier (water supply enterprises and valve manufacturers), not just one of them. First of all, as the ordering party of water supply enterprises, when ordering to the valve manufacturers, they must put forward clear technical requirements in written form to the valve manufacturers. The contents should include the types of valves, the technical standards and quality standards to be implemented in all parts of the valve, the main technical parameters, the material of each part, and the valve's quality. Type, seal form, seal material requirement, structure form, connection mode and transmission mode, technical standard of pressure test and strength test, requirements of anticorrosion and lining, maximum torque and rotation, assembly and appearance requirement, delivery time, place and quantity, etc. Valve manufacturers should rationally organize production according to the order contract and technical conditions, and ensure that the products produced can meet the use requirements of the ordering units (water supply enterprises), and ensure the consistency between the ordering and suppliers.

Establishment of a perfect inspection and re-inspection system

When a water supply enterprise, after many investigations, investigations and tests in a certain range, finally chooses one or several valve manufacturers and issues the pass to its products to allow access to the local water supply market, it means that the supply-demand relationship between the water supply enterprises and the valve manufacturers has been established. At the same time, the valve manufacturer also assumes joint and several responsibilities in ensuring safe and reliable water supply for water supply enterprises. On the one hand, valve manufacturers are required to consistently provide high-quality products in accordance with the requirements of water supply enterprises. On the other hand, in order to ensure quality, water supply enterprises are required to establish a necessary and perfect periodic inspection and re-inspection system for designated manufacturers, which is generally suitable for 2-5 years. Regular inspection and evaluation are given to the five elements of fixed-point manufacturer, i.e. person, machine, material, method and ring. While inspecting the manufacturer, the water supply enterprise should also base itself on the unit.

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