The selection and determination of the caliber is mainly based on the flow capacity of the valve, that is, Cv. When designing and selecting instruments for various projects, Cv calculations must be performed for Universal Valve and Universal Valve design instructions must be provided. From calculating the Cv of the Globe Valve to determining the valve diameter, the following steps are generally required:
1. Determination of calculated flow rate. The existing production capacity, equipment load and medium conditions determine the Qmax and Qmin of the calculated flow rate.
2. Determine the pressure difference before and after the Globe Valve. Select S (resistance coefficient) according to the selected valve flow characteristics and system characteristics, and then determine the calculated pressure difference.
3. Calculate Cv. Select the appropriate calculation formula and chart according to the medium being adjusted to obtain Cmax and Cmin.
4. Select Cv. According to Cmax, select a level C that is >Cmax and is close to it in the selected product standard series.
5. Check the opening of the Globe Valve. It is generally required that the opening degree is ≯90% when the calculated flow rate is large, and the opening degree is ≮10% when the calculated flow rate is small.
6. Check the actual adjustable ratio of the Globe Valve. It is generally required that the actual adjustable ratio ≮10.
7. Determination of valve seat diameter and nominal diameter. After verification, determine according to C.
The selection of Globe Valve is a very detailed work, which requires not only solid professional theoretical knowledge, but also rich practical experience. Good selection not only helps to adjust the PID parameters of the control loop, so that the adjusted parameters can be better controlled, but also greatly increases the service life of the Universal Valve. The selection of Universal Valve must be adapted to local conditions and is not static. It must be constantly summarized and innovated in the process of practice. Especially with the application of mechatronics technology, computers and digital information technology, the structure and function of Globe Valve have become better and more comprehensive. It provides great convenience for selecting Globe Valve.
