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 Current Topics Agricultural Water Distribution |
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Resolving the concerns of agricultural water distribution ... YOKOTA Constant
Flow Regulator Valve (PAT.)
Water is indispensable for all agricultural crops. The critical role of supplying only the necessary amount of water at the required time is performed by agricultural irrigation systems. In addition to traditional use of open channels, today we see increasing use of pipeline irrigation that is a more rational form of water control management and allows for more economic use of water resources. We would like to present the YOKOTA Constant Flow Regulator Valve that is being adopted more and more as a convenient control valve for pipeline irrigation. Agricultural-use water is taken from a dam or river, sent through a main channel to where it is divided up and sent along branch lines. At the end of the branch lines the water is then divided again for the agricultural-use channels through which the water is supplied to the fields. For this reason, the overall pipeline distance is quite long and there is a large variance of pipe elevation due to the peaks and valleys the piping must traverse. Supplying equal amounts of water to all fields in a stable manner under these conditions is a challenging task. In order to ensure an even supply of water, facilities called "water division works" are established and it is here that flow rate control valves are installed and operate so that water intake matches the flow rate specific to each water division work.
By the way, in the past, the division of water to various fields was a constant source of concern since nothing as useful as a flow rate control valve existed. For example, let's take a look at two large concerns of the past that have caused numerous headaches:
The YOKOTA Constant Flow Regulator Valve has been developed to resolve these types of concerns. First, let's take a look at the constant flow rate characteristics of the Constant Flow Regulator Valve. The flow rate shown along the vertical axis is securely maintained at a constant value even if there is a change in the difference between the primary side pressure P1 (inlet side) and secondary side pressure P2 (outlet side) as shown along the horizontal axis.
In addition to this secure constant flow rate characteristic, the YOKOTA Constant Flow Regulator Valve is clog-resistant and, moreover, is highly versatile as the set flow rate can be freely adjusted and, when water is not needed at all, the valve can be completely shut. How can one valve have all these capabilities? Before we explain how it works, let's examine how the valve is used at some actual locations. Constant Flow Regulator Valve used for discharge water distribution to open channels Constant Flow Regulator Valves were first installed at the Water Resources Development Public Corporation (former name) in Gifu Prefecture in 1979. At that time, as seen in the photos below, the valves were installed as discharge devices on the ends of piping and they were utilized as constant flow rate discharge valves and also to reduce the pressure of high-pressure water coming from higher elevations, such as that from dams. They were especially noteworthy for their compact structure, as seen in the figure, allowing them to be installed with a minimum use of space.
In-line type Constant Flow Regulator Valve used for water distribution to open channels The lineup of Constant Flow Regulator Valves, including the in-line types currently in use, was completed in 1986. The photos below show a 400mm bore Constant Flow Regulator Valve installed in a water division works of the Kasumigaura Canal of the Kanto Regional Agricultural Administration. Due to this, a wide area of agricultural fields in the Kanto Plains can be irrigated, allowing the valve to play a beneficial role in producing bountiful crops. As shown in the figure, the valve is located in the middle of the piping, enabling it to distribute water according to the set flow rate. Because the Kasumigaura Canal must provide irrigation water for a large area of agricultural fields in Ibaraki Prefecture, there are tens and even hundreds of water division works locations, all requiring water simultaneously during the irrigation season. The valve is able to ensure that no matter how the pressure on the primary side changes, the flow rate from out of the secondary side will remain exactly as set.
Constant Flow Regulator Valve used for farm pond water distribution The photos below show a farm pond (agricultural-use water tank) located at the top of a "mikan (Mandarin orange) hill" in Ehime Prefecture and a 250mm bore Constant Flow Regulator Valve used for distributing water to the pond. Water used for irrigating the mikan orchards all over the hill is taken from the main channel and brought to the top of the hill where it is stored in the farm pond. In the past, it was extremely difficult to supply a uniform amount of water to each hill with their varying altitudes. Now, however, this task can be performed effortlessly thanks to the Constant Flow Regulator Valve.
YOKOTA Constant Flow Regulator Valve (PAT.) features
How is such precise constant flow rate control achieved? Let's look at the figure and examine how the water flows.
The primary pressure water enters through the inlet and flows out in the direction indicated by the arrow. Chambers above and below the sliding valve are partitioned by the diaphragm and the pressure of the upper chamber of the diaphragm is equivalent to primary pressure P1 since the chamber is connected to the inlet via the primary pressure pipe. On the other hand, since the lower chamber of the diaphragm (intermediate chamber) is connected to the inlet via the throttle passage A, the chamber's pressure Pd is slightly less than primary pressure P1. Thus, the sliding valve lowers to a position where the differential pressure (P1-Pd) is balanced against the coil spring force, adjusting the outlet passage B so that water discharged from the outlet side remains at the preset flow rate. This is where the advantage of the Constant Flow Regulator Valve becomes apparent. If the primary pressure increases, increasing the rate of incoming water, the passage resistance of passage A increases and the pressure differential (P1-Pd) increases accordingly. When this occurs, the force pressing downward on the sliding valve acts until the valve reaches a balanced position again, and the outlet passage B is constricted so that the discharge flow rate remains the same as before the primary pressure increased. What do you think? Quite ingenious, isn't it? Cavitation coefficient The cavitation coefficient is used as a standard for judging the performance of flow rate control valves. The Constant Flow Regulator Valve has an excellent coefficient value of 0.24 or less. The figure below compares the cavitation coefficient of various valves. As shown, a butterfly valve has a value of from 1 to 3 and a conventional automatic control valve has a value of 0.5 so the excellence of the Constant Flow Regulator Valve's cavitation characteristic is clearly understood.
Given this unique structure, the Constant Flow Regulator Valve is extremely easy to use for water division works management, is beneficial for the economic use of water resources, and can be utilized by those who strive to create even more productive crops. For details of this product, please refer to Constant Flow Regulator Valve UF series. |
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