In industrial valves, control valves serve various critical process functions. These power-operated devices, such as liquid, steam, or gas, typically regulate or manipulate flow.
Here, we will explore some of the most common types of control valves and their applications. We will also consider the steps necessary to ensure proper valve functioning and performance, including the importance of periodic control valve testing.
How Control Valves Work
Control valves operate under the power of an actuator, the power source of which can be pneumatic, hydraulic, or electric. Depending on the actuator signal, these devices vary the flow opening based on the desired settings specified for an individual process which involves set points for liquid level, temperature, velocity, and pressure. The degree of regulation involved – which can range from fully closed to fully open or modulating (any position in between) – is determined by a valve controller.
Although these devices are typically simple in design, their operation and control can be highly complex. Valve actuators receive signals from outside sources, depending on the process flow design and the specific requirements for the given valve.
Control valves are used in countless applications; these are some of the most common control valves in use today.
Linear Motion Control Valves
Sometimes known as multi-turn valves, these devices achieve flow control via a sliding stem-type mechanism to open and close the device. This simple design offers maximum durability and versatility. Some of the most common types of linear control valves include the following.
These devices, so named for their spherical-shaped body, function via an internal baffle with a disc or plug that operates to open or close flow within the device. Globe valves are standard in regulating process flow. Some typical applications for these devices include fuel oil systems, boilers, steam vents, water cooling systems, and chemical feed systems.
Sometimes called a sluice valve, these devices control flow by opening or closing a barrier within the valve’s body, known as a gate. Whereas globe valves typically regulate flow, gate valves are exceptional when the need to stop flow exists. Applications for gate valve use include potable, wastewater, and other neutral liquids.
Rotary Motion Control Valves
Sometimes known as quarter-turn valves, these devices allow fluids to flow through a type of rotating element, which can be used to cut off the flow. Typically used in high-demand environments, these devices are compact and versatile. Some of the most common rotary motion control valves include the following.
Popular for use in control and shut-off applications, these devices are exceptionally durable and reliable, even after long periods of disuse. Various ball valves are used, depending on the application, including full-bore valves, reduced bore, multiport, cavity filler, and v-port. Although operation remains consistent, ball valves can be composed of a single body, a split body, a top entry body, a three-piece body, or welded body.
Butterfly valves use a rotating disc to control flow, similar to ball valves. Although they can control liquids, gasses, or solids, these devices are primarily in the food and beverage industry, pharmaceuticals, petroleum, and other chemical processing applications. More cost-effective than ball valves, these devices have been widely adopted across various sectors.
Other Types of Control Valves
Control valves that don’t fit into the two primary categories outlined above include the following.
Pinch valves use a pinching effect to control flow. Fully ported control valves are found in various applications, including the food and beverage industries, chemical and wastewater applications, and the handling of bulk or solid materials. This approach is beneficial for containing and controlling aggressive materials that might overwhelm other types of valves.
Sometimes known as membrane valves, diaphragm valves are typically made from durable materials such as steel and brass – although some applications might support heavy-duty plastic materials. These devices are often found in corrosive or abrasive environments where solids or solid-entrained liquids are a part of the process. Diaphragm valves are controlled by manual, pneumatic, hydraulic, and electric actuators. The most common diaphragm valves use pneumatic actuators where air pressure is applied through a pilot valve into the actuator, which raises the diaphragm and opens the valve. This type of valve is used when valve speed is critical.
Hydraulic diaphragm valves are used in high-pressure, low-speed applications. Diaphragm valves are used in pharmaceuticals, mining, wastewater, power, and paper.
Control Valve Testing
Control valve testing is a critical aspect of valve operation. Specifically, periodic, comprehensive testing ensures a valve’s proper and safe operation.
SofTek Engineering offers industry-leading control valve testing equipment and valve profilers. Our valve testing and diagnostics equipment, including Profiler and Profiler Mini, is designed to help you avoid costly downtime. Our valve diagnostic systems perform a full range of performance testing appropriate for more than just control valve diagnostics. Use our systems for isolation valve diagnostics, block valve diagnostics, fugitive emissions testing, and more.
Our valve testing equipment is light and portable, making it ideal for use in virtually any location or application. Our best-in-class training ensures you get the maximum value and return on investment.