The conventional water production process of the water plant is inseparable from the use of valves from raw water intake, flocculation and sedimentation in the sedimentation tank, filtration in the filter tank, and finally the output of the water supply from the effluent pump room. However, the selection requirements for valves are very different in different parts. The main difference lies in the diameter of the valve, the type of valve and the control method of the valve.

Valves for conventional water production systems in water plants

1 Process valve for raw water intake

The valve of the raw water at the head is characterized by a large valve diameter and does not need to be operated frequently. Most of them only need to be operated once a year or even several years, and the valve is in a normally open or normally closed state for a long time. Therefore, in terms of control method, more than 95% of the valves are manual valves, and the valve types are gate valves or butterfly valves. Because the head loss of the gate valve is better than that of the butterfly valve, the head valve gate valve is slightly more than the butterfly valve. The diameter is concentrated in 1200~1600mm, and there is also a valve with a diameter of 3000mm on the head inlet pipe.

2 Sedimentation tank valve

The valves of the sedimentation tank are mainly the inlet valve, the outlet valve and the isolation valve. The outlet valve is basically in a normally open state, and the isolation valve is basically in a normally closed state, which is operated once a year. Therefore, these two types of valves use manual gate valves, and the specifications are distributed between 2200×1800~1200×840. The inlet valve of the sedimentation tank undertakes the important responsibility of water distribution, requiring frequent adjustment, reliable performance, and is distributed in front of each sedimentation tank, and the distribution is relatively scattered. It is a key part that determines the water volume of the sedimentation tank and the balance of the system. It is particularly important for the system where the water production line is dynamically adjusted according to the water output, and PID dynamic tracking adjustment is also required. At this time, for the full stroke time of the valve, The allowable start and stop frequencies will have corresponding requirements.

3 Filter valve

The most common filter is the four-valve filter, which is also the most basic configuration of the filter. That is, no matter what kind of filter, there are at least four types of valves: inlet valve, drain valve, flush valve and clean water valve. Of course, there are also many five-valve, six-valve or even seven-valve filters, which are also equipped with air flushing valves, primary filtration water valves or an additional water inlet valve, etc. From the structure of the valve, the clean water valve and the flush valve usually choose the butterfly valve. The main reason is that the clean water valve and the flush valve are both installed on the pipeline in the pipe gallery, and the clean water valve needs to be adjusted frequently, and the flush valve will also adjust the flushing strength. demand. The water inlet and drainage are usually carried out through the channel, so the inlet valve and the drain valve are basically the gate valve. The diameter of the flush valve of the filter tank is slightly larger than that of the clean water valve. The flush valve is basically DN600~DN800, while the clean water valve is DN400-DN600. The size of the inlet and drain valves is related to the channel size. From the point of view of the control method, these four types of valves all use electric control or pneumatic control. However, the clean water valve must be an adjustable intelligent control mode, which is consistent with the requirements of the inlet valve of the sedimentation tank. In addition, considering the integrated wiring and modular design method, the filter valve can choose the bus-type control mode or the PLC station-based control mode. The advantage of the former is to save wiring space, and the advantage of the latter is that the single-cell filter is separated, which is convenient for maintenance, management and transplantation.

4 Pump room valve

The valves in the pump room are mainly the inlet valve, outlet valve, maintenance valve and check valve on the pump unit. The first three valves basically use butterfly valves, and the difference lies in the control method. The inlet valve and the maintenance valve only need manual valves, because one of them is in a normally open state and the other is in a normally closed state, and the outlet valve needs to be opened and closed every time the pump is turned on and off. The water volume makes the pump have different working conditions to meet the demand factors, and the water outlet valve also needs to be controlled by an adjustable intelligent device. The check valve should prevent the occurrence of water flow to the turn and avoid the occurrence of water hammer. Usually, a silent check valve and a slow-closing check valve with a slight resistance are used. Sometimes a multi-function valve is also used, which integrates the water outlet check function.

Valves for dosing systems in water plants

The characteristics of the water plant dosing system determine that the valve used on it has a small diameter and a small flow rate, but it has high requirements for flow regulation, high precision and fast adjustment speed. Therefore, a flow regulating valve is usually used. Depending on the structure of the valve itself, the flow adjustment can be accomplished at one time. In addition, the medium in the pipeline of the dosing system is ammonium sulfate, sodium hypochlorite and other solutions, which requires the valve to also have the ability to resist corrosion. In addition, the dosing system will also use ball valves as on-off valves, back pressure valves, etc.