Getting to Know Control Valves
Control valves are devices that are commonly and greatly utilized in many different industries to control certain conditions such as pressure, flow, liquid level, and temperature. In the oil and gas as well as manufacturing industries, being able to control such conditions is very crucial in order to maintain a stable and safe stream of materials. The control valves allow regulating the flow of liquids through their open and close functions, partly or totally, as influenced by the sensors. Pressure as well as temperature, etc. are read and measured, while a microcontroller analyzes their scale according to a specified value. After assessment, it relays the controlling signals for the opening or closing of the valves, whichever is appropriate.
In the past, control valves were controlled manually, but now, almost every industry uses the automatic type of control valves. Such valves come with hydraulic and electrical regulators as well as pneumatic/electro hydraulic actuators that respond to magnetic or pneumatic signals. Although the industry traditionally used 0.2 – 1.0 bar (3-15 psi) for an HVAC system of 0-10V, today these systems are mostly using the 4-20 mA type. Different types of HVAC control valves now exist with design and assembly that vary just as well. Control Valves typically feature thee major parts: actuator, positioners, and body.
A valve actuator facilitates the automatic opening or closing of the valve to regulate the outpouring of fluids, based on the what the control signals transmit. There are four basic types of actuators that correspond to their power source – electrical, pneumatic, hydraulic, and electro-hydraulic. Electrical actuators feature motors that are powered by a voltage supply or an electric current. These actuators are relatively easy to manipulate considering that the electric signals can be simply controlled using its micro controllers as well amplifiers. Hydraulic as well as pneumatic actuators have similar structure, and both have a piston accompanied by a cylinder setup. When the cylinder is pressurized and de-pressurized it creates a reciprocating movement on the piston. The cylinders of hydraulic actuators contain water; the pneumatic versions have air. Electro hydraulic cylinders, on the other hand, are a mix of hydraulic and electric cylinders, and can take on heavier loads and are easily controllable through electric signals.
The valve’s positioners are used for accurately determining which valve needs to be closed or opened. Valve positioners of the digital variety are now widely used because they offer better positioning.
Valve’s body – the bodies of control valves generally come with a sliding stem ball along with angle valves. With this design and its rugged construction, it becomes suitable for a variety of applications.
Valves function as valuable HVAC diagnostic devices as they control the stream of liquids within the pipes. By closing or opening the pipelines, they actually bring down water and gas spending.
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