Process control valves are virtually used in all industries. It is fair to say that these affect our daily life in one way or another. They come in different shapes and sizes. These are considered an important part of the control loop because they control flowing fluids such as water, steam, gas, or other chemical components. They do that to compensate for the load disturbance and to ensure that the regulated process variable is kept as near as possible to the preferred set point.
What is Process Control?
It is a vast engineering discipline that specifically handles the use of a media, computerized or mechanical controllers, feedback sensors, control components, and even human activity to produce the desired results. It can be said that process control ranges from a thermostat used to control a furnace in a heating system to a complex industrial plant. Nowadays, many products are manufactured using different processes that are controlled with the help of automated valves. Process control has a vast range and its implications require a range of valve types, materials, sizes, and actuation methods.
There are two main categories of Process control systems:
Continuous Processes Systems: They run non-stop 24/7 and that is why they are called CPS. Special consideration is given to handling maintenance and malfunction of these systems because it can be very costly to start them up if they ever shut down.
Batch Processes Systems: These systems can start and stop naturally and require less maintenance as compared to continuous processes systems.
Process Control Valves
When there is talk about control loop, one of the major role players process control valves. These are responsible for manipulating flowing fluids. Hydraulic, electrical, and pneumatic actuators are used for the purpose of opening or closing of automatic control valves. There are three main parts of an automatic control valve:
- Valve positioner
- Valve actuator
- Valve body
Types of Process Control Valves
It is a quarter-turn valve that is used to control flow through it. It uses a perforated, hollow, and pivoting ball for this purpose. The ball valve has further two types:
- 2-Way Ball Valves
It has a simple and quite common design. A ball and hole are bored through that lead to inlet and outlet because they get sandwiched between two seats. The bore gets paralleled to the direction of flow when the ball is in open position. The flow gets stopped when the valve is turned to 90 degrees.
- 3-Way Ball Valves
It is quite likethe 2-way ball valves and the only difference is that it has 3 ports instead of 2 ports.
These are similar to ball valves and they are operated similarly by turning obstructer 90 degrees from open to closed position. However, there is the use of a thin disc as obstructer in these valves and they are opened by turning the obstructer sideways.
High-Performance Butterfly Valves
These valves have two types:
- Resilient Seated Butterfly Valves
These have a soft seat with a rigid body. The seat plays two important roles: (1) it acts as a seal between pipes and valves (2) it acts as a seal between the disc and valve.
- 3-Way Butterfly Valves
These have a geometry that makes it impossible for them to be 3-ways. However, an assembly of 2 butterfly valves is used when there is need of valve with 3-way functionality during the processes with large diameter pipes.
In addition to these valves, there are other types as well such as plug valves, pneumatic actuators, valve actuators, and electric actuators