Waterworks of conventional water making process from the raw water intake, flocculating settling basin precipitation, filtration process, until the final output water supply, water pump house is inseparable from the use of the valve. But in a different part of the requirements for the selection of the valve is not the same, the correct and reasonable choice, can obtain the economic life of the valve and the best performance. The main difference is that the diameter of the valve, the valve material, the type of valve and valve control method. This article mainly aims at the valve selection of waterworks are briefly analyzed.
1, the valve in the role of urban and rural water supply network
In the process of the distribution of water resources, indispensable, it plays a transport mediation role, urban and rural water supply pipe network is widely used, construction work is also very great, different types of urban and rural water supply network to meet the needs of different people. In the ordinary management, is not always applied to the valve, but in an emergency situation, a qualified valve must be able to achieve flexible control, to control the water flow. Valve when the choice, focus on the type, material, manufacturer, production technology, etc., from various aspects to determine quality conforms to the standards of the valve.
2, water system, water system of the distribution of the valve
2.1 raw water for water process of the valve
The head of the raw water valve is characterized by the valve diameter is larger, more operations, most belong to need operation only once in a year or even years, valve normally open or normally closed state for a long time. Therefore, from the control method is more than 95% of chosen manual valves, from which for gate valve or butterfly valve type, due to the head loss than butterfly valve gate valve, head slightly more than butterfly valve gate valve. Caliber is concentrated in the 1200 ~ 1600 mm, path of the inlet pipe of the head is diameter 3000 mm or 3000 mm above the valve.
2.2 tank valve
Tank valve is mainly water valves, water valves and isolation valves. Basic in a normally open state, water valve isolation valve in a normally closed state, basic operation once a year, so these two valves are choose manual gate valves, specifications distribution between 2200 x 1800 ~ 1200 by 840. And the tank inlet valve bear an important responsibility of water distribution, require adjustment is frequent, reliable performance, and distribution in each tank before, distribution is more scattered, adopt electric regulator with intelligent control system. It is to determine the amount of water in the tank and system balance, a key ring for water system was adjusted dynamically according to the water yield of system, is particularly important, and you also need to adjust PID dynamic tracing, then for the total travel time of the valve, allowing the start-stop frequency will have corresponding requirements.
2.3 filter valve
The most common filter for four valve, filter, that is the most basic filter configuration. That no matter what kind of filter at least fill valve, drain valve, flush valve and water in the four types of valves. Now, of course, there are many five, six valves (v-type filter) even seven valve, filter, also equipped with a gas valve, filter water valve in the early or more equipped with a water inlet valve and so on. From the structure of the valve up to distinguish between water and flush valves usually choose butterfly valve, the main reason is that water and flush valves are installed on the pipeline within the pipe rack, and the water valve need frequent adjustment, and the intensity of flush valve will also have to adjust flush demand. And feed water and drainage usually through channels, and inlet valve and gate valve is used in the drain valve are basically. Filter the flush valve caliber valve diameter slightly larger than water, flush valve according to the filter area, irrigation intensity and the flush time requirements in DN600 ~ DN800, basically the water valve, filter velocity in the flow according to the requirements in DN400 to 24 "). The size of the inlet valve and drain valve associated with tank design flow, the size of the channel.
2.4 pump valve
Pump valve is mainly on the pump unit within the inlet valve, water valve, valve and check valve. The first three generally choose butterfly valve, the difference lies in the control mode. Inlet valve and valve repair you just need to manual valves, because they were in a normally open state. Pump outlet valve choice, should first meet can pump valve start and stop, if you consider to use water can adjust water, make water pump have different operating mode to meet the demand factors, water control valve is also need external regulation intelligent device; Second should be equipped with a check valve in the pump unit outages can quickly close the valve to prevent water pump long time reversal, and to avoid water hammer pump is going to happen.
2.5 water dosing system of the valve
The characteristics of water dosing system determines the use on top of the valve diameter is small, small flow rate, but higher requirement to the flow control, high accuracy, adjusting speed, so usually choose flow regulating valve, the valve makes medium flow capacity is determined by the structure of the valve, only then did a complete flow control. Piping within the medium water dosing system is mainly aluminum sulfate, ammonium sulfate, sodium hypochlorite solution, which requires the valve also has the ability to resist corrosion. Ammonium sulfate corrosion for copper, cannot choose copper mass production of the valve, general stainless steel ball valve or UPVC ball valve. Corrosion of steel, iron, sodium hypochlorite can't and the use of steel and iron material valve, generally USES the UPVC ball valve or ptfe lining hartz alloy valve spool valve.
Dosing system also can use stainless steel ball valve, UPVC ball valve or butterfly valve as a valve, switch valve, etc.
3, the choice of valves
The first step, chooses the valve use, the working conditions of use and control mode.
The second step, the installation size of size and shape, and pipeline connection.The third step, the flow characteristics of the valve requirements: head loss and flow characteristic, protection class, etc.
The fourth step, the nature of the working medium, working pressure, working temperature, corrosion resistance, whether containing solid particles.
Step 5, if the valve is used to control, must determine the following additional parameters, control mode, the maximum and minimum flow, normal flow pressure drop, the closing of the maximum and minimum pressure drop and valve inlet pressure.
4, the valve selection steps
The first step, the valve sealing performance to meet the requirements of the medium.
Second, determine the technical requirements, that is, to determine the pressure inside the piping, flow and back pressure, etc., to determine the nominal pipe diameter and the diameter of the valve seat hole, decided to form and type of the valve.
Third step, according to the diameter of pipeline, site conditions, choose the type of valve, based on the process parameters of the second step, select the valve, according to the installation position of the valve at the same time, determine the selected structure and length, the flange connection of valve size, the size of the height direction after the opening and closing valve, connection bolt hole size and quantity, the whole valve size shape, etc.
The fourth step, according to the pipeline medium, working pressure, working temperature to determine the selected valve shell and internal parts of the material.
Fifth, according to the transmission form selection, water plant of butterfly valve is given priority to with multi-turn rotational body, the transmission system of the gate valve is a straight travel.
Step 6, to determine control mode for the gas control system is the cylinder and the choice of form a complete set of transmission mechanism, the electric control system is the electric actuators. For the choice of electric actuators is the total travel time of according to the requirements of the valve, the valve torque parameters, such as to determine the transmission ratio and the output torque, interface types, determine the speed of the motor, power, etc.
Step 7, consider the protection grade of the actuator, communication method, whether to choose SCR and other configuration.
Step 8, using existing data: the valve catalogue, choose proper valve products such as valve products sample.
To sum up, with the improvement of automation level, water is becoming more and more high to the requirement of the valve, more and more, but no matter how to change, choose a regular on roughly in within the scope of this paper. The main valve has mentioned, this paper used water and, of course, exhaust valve, solenoid valve, back pressure valve, etc., there is no longer are introduced in detail.