Small flow electric control valve

In many industrial systems applications, precise control is required for small quantities of material under normal pressure or slightly larger quantities of material at very high pressure drops. Cv values ​​calculated at this time are very small. This can be done with an intermediate lab with minimal production or with industrial equipment that adds small amounts of reagent to a large amount of process liquid. The theoretical minimum Cv value is 0.00001 and the small flow includes a Cv range that is equivalent to the range covered by normal valve sizes from 1 inch to 16 inches. When considering the use of these small flow valves, the guidelines used are very different from those of conventional control valves. For example: the friction loss in series with the control valve is small and there is no disadvantage of the pump head characteristics. Does not require true equal percentage features. The main design issue is to carefully study the actual required flow range. The smaller the Cv value becomes, the more the theoretical value becomes. They are useful as an indicator of liquidity, but accuracy and repeatability are questionable because, in many cases, the fluid passing through the throttling part may be a laminar flow or a mixture of laminar and turbulent flow, which Mixed flow varies with valve travel or flow conditions. From the design point of view, the actual size required for fluid throttling is indeed small; the fact that many small flow applications involve the problem of high differential pressure with wear and tear poses further problems. In the standard valve design, the flow capacity is mainly determined by the diameter of the seat hole. As flow capacity decreases, the actual minimum diameter reaches 1/16 inch. Thus, the theoretical Cv value of the pores is approximately 0.06 or close to the upper limit of the small flow rate range. Mainly used to reduce the spool stroke or limit the opening of the mouth to make it even further reduced. The short stroke actuator is well-suited for balanced throttling, using a pneumatic actuator to actuate the arm and a slight rotation to drive a threaded spool valve stem, in which two different threads of thread are used To further limit the trip, use this method can limit the trip to less than 0.005 inches. When the linkage is variable and the stroke ratio is greater than 10, the maximum travel of the spool is 0.188 in. For actuators rated 3/4 in., The stroke can be reduced to 1/4. In this way the stroke can be reduced to a minimum of 0.010 inches. This allows a wide range of flow capacity to be adjusted in the field while also providing high operating force for high differential pressure operation. Both special valves use a simple tapered spool. For a very small flow, use a delicate taper pin and adjust it in the taper hole. For a few strict occasions, the use of tapered needles or tape milling magpie alarm clock 械 冢 冢 mute section mute section? / 8 inch to 1/4 inch, this type of valve stroke is about 1 / 2 inches. This low-flow trim can be installed in a common ball valve body at the factory but can significantly reduce the size of both the valve body and the actuator. These valves are lightweight, compact and well suited for the operation of the experimental setup. When the size is reduced, the Cv value of the small flow trim is not significant. Fortunately, there is a large effective flow range in the valve seat bore. In addition to adjustable valve travel, the trim is easy to replace and, with many of the same valves, the cost of repairing several trim parts is not high because interchangeable valves are interchangeable. Calculate the required Cv values ​​using the usual formulas and then select the trim near the maximum size for the particular valve being used. If the actual operation of the valve trim is too small, you can simply increase the valve stroke or slightly modified spool method to improve the flow capacity. Search Keyword: Electric Control Valve Supply Information