The control valve is one of the types of valves that finds the widest application in all kinds of industries. This device can be used as a simple temperature controller or as part of a complex process control system in automatic mode. Regardless of these factors, a very important point is the selection of such a valve.
If the
control valve is selected correctly, then this will not only achieve optimal control accuracy, but also easily avoid problems such as erosion wear and high noise levels. In some cases, the valve has such
a capacity that is fully consistent with the task at hand, and in order to reduce the noise level, it is worthwhile to give preference to types of valves having a larger nominal diameter.
The control valve is quite difficult to choose due to the fact that a number of requirements should be linked together, which, in essence, are mutually exclusive. Choosing a valve with a low flow rate or with an excess supply of it can cause significant problems. If the
control valve has too much flow capacity, this leads to the fact that it does not provide the proper level of control accuracy. This is due to the fact that the valve stem will move a small distance (noticeably smaller in comparison with the full stroke of the rod). Errors of this kind often lead to instability of the entire system, as well as to failure of both the valve itself and the entire actuator. Sometimes the control valve is selected so that the pressure drop across the open device is maximum for this particular task with the largest vapor flow rate. If we talk about practice, this means that the selection of the valve is carried out at a differential pressure.
An important parameter to be guided when choosing a control valve is noise. The valve should be selected so that the steam flow rate at the outlet does not exceed 30% of the
speed of sound. This parameter is exceeded very often due to the fact that the nominal diameter of the valve is very small, and the seat also has significant throughput.
The shut-off and control valve may have a special design that can significantly reduce noise. In such units, a
pair of saddle-plunger is presented in the form of perforated cylinders, which significantly reduces the noise level, and also reduces cavitation (if the valve is used on liquids).
The choice of valve, as it became clear, should be carried out with the obligatory consideration of a considerable set of factors, which significantly complicates this process. The surest way to avoid any problems is to contact a reliable supplier with sufficient knowledge and experience. This will allow him to offer the client the highest quality products. It is important to pay attention to certain points, among which it is worth highlighting: the reputation of the manufacturer, the suitability of the valve for repair, the ability to change the throughput or characteristics of the valve, as well as other parameters that affect usability.