How to choose the size and design of the shut-off and control valve
The requirements for the shut-off and control valve are determined by the scope of its application, the specifics of the controlled process and the expected result. The process conditions and the range of parameters also vary widely, including pressure, temperature, controllability, cavitation risk, environmental impact, noise, etc. The priorities of the user and the contractor are also often different.
Choice of execution
Each type of valve plays a role. Therefore, it is important to know which one to choose to complete the task. As shut-off and control valves are most often used:
- Ball bearings;
- Segmental;
- Eccentric;
- Butterfly valves.
Ball type shut-off and control valves are a good choice for medium and high pressure drops. Their popularity is due to their resistance to cavitation. The replacement of such a valve is very simple, which is especially convenient in case of changes in the conditions of the controlled process or the performance of the unit. These valves are ideal for reducing noise when pumping purified liquids, and are also widely used for servicing small diameter pipelines. As an external drive, a hydraulic or pneumatic actuator is usually chosen.
Segment valves are an economical solution to achieve high performance with a smaller nominal valve size. Such drive valves operate stably with any method of their installation – vertical, horizontal or inclined. Segment valves function stably in viscous and poorly cleaned working environments.
Eccentric rotary plug valves are a compact and reliable solution for more complex tasks due to high costs and high viscosity of the pumped products. They are used for industrial purposes, for example, in the oil and gas industry (hydraulic drive) or at water treatment plants (electromechanical drive).
Butterfly valves are lightweight, cost-effective solutions, especially popular in conditions of increased costs. They provide high throughput and good stability with changes in pumping mode. The drive is mainly pneumatic.
How to implement the adjustment process
External changes in pumping conditions may be associated with cavitation and noise, which are accompanied by an increase in pressure and temperature. The torque values on the shut-off valve actuator change dramatically at the same time. If you do not react to this, they can quickly cause problems with the valve and with the process controlled by it.
It is important not to choose a valve based on a single operating point, but to take into account all possible process conditions. The dimensions and standard size should be based on minimum, median and maximum flow conditions and flow pressure values. Therefore, in the control circuits of valves of this type, pressure, temperature and flow sensors are necessarily provided, or at least a pressure gauge (with manual control of the actuator).