Control valve CV value

{:1_90:} The Cv parameters are available on our company’s website: http://www.muhengpv.com/product/diaojiefa/qidongdiaojiefa/

Generally, just provide the operating conditions to the valve manufacturer

It was found that samples can be sent directly in the reply. . . Please find it below

Thank you. I took a look, but I still don’t quite understand how to make the choice. For example, the KV values I calculated are 5.49 for the maximum, normal, and minimum values respectively； 2.99 ； For a 0.5 pipe with dn50 and pn25, what KV value should be chosen?

Quoting a passage: The Cv value, which represents the flow capacity, is one of the key parameters in selecting control valves. The flow capacity of a control valve is defined as the volume of fluid that can pass through it per hour, when the valve is fully open, with a pressure difference of 0.1 MPa across it and a fluid density of 1 g/cm3. This value is also known as the flow coefficient, denoted by Cv, and its unit is t/h. When choosing a control valve, the calculated CV value must fall within the operating range under normal conditions; moreover, the valve’s characteristic curve must be taken into account, as well as extreme flow conditions. A coefficient is applied to the CV value for this purpose

According to your calculations, for example, if the rated Kv is set at 10 (with a nominal diameter of 25), the flow characteristic is equal percentage and the adjustable ratio is 50, then the corresponding opening degrees will be 85%, 69%, and 23% respectively. If other factors are not considered, diameter reduction is required, that is, reducing the diameter at the valve seat to 25mm.

I calculated that the maximum KV is 5.49. If I choose values based on equal percentages, then according to the manual you sent, it should be okay for me to choose 6.3 as well, right? Also, does the nominal diameter mentioned in the manual refer to the size of the valve seat?

1. No, the opening is too large; the adjustment function cannot be implemented. 2. If it is used for selection, it can probably be understood in this way. However, the nominal diameter is not used to indicate the actual size

This post was last edited by Hariky on 2022-8-13 at 17:11. Refer to clause 10.1.4.3 in SH/T 3005-2016. How to choose depends on the type of valve and its flow characteristics. The calculated Cv value is compared with the valve’s flow characteristic curve to determine the opening degree. Flow characteristics are divided into \"ideal flow characteristics\" and \"inherent flow characteristics\", with the latter being commonly used. The inherent flow characteristic curve is the actual curve that is determined point by point for each valve model and size. Some manufacturers that do not meet the required conditions use an “ideal flow characteristic curve” to determine the opening degree, which is not very accurate. One can initially estimate the opening degree for selection by referring to the ideal curve and the rated Cv values provided in the manufacturer’s samples (some manufacturers’ materials offer an approximate curve or Cv values corresponding to a range of opening degrees from 0, 10, 20, 30 to 100%). Confirmation will be made based on the manufacturer’s calculation sheet at the time of actual ordering. Note: You are using Kv; this value needs to be multiplied by 1.157 to convert it to Cv for selection purposes.