Control Valves

Control valves help system operators ensure operating conditions remain within the acceptable range, resulting in better process consistency throughout an operation and between operations.

Consistency and quality go hand-in-hand. Variability in processing operations inevitably leads to products of varying quality. By using control valves—which enable better process consistency — processing facilities minimize the risk of variation between products and product batches, resulting in better overall product quality.

Reduced process variability also translates to less material waste, as fewer substandard products will need to be scrapped. Additionally, the greater precision offered by control valves results in less time spent making adjustments to the process throughout an operation.

Many processing operations require specific operating temperatures, pressures, and other flow conditions. Control valves help equipment maintain the desired conditions throughout the process, reducing the amount of energy needed for optimal processing performance.

Deadband occurs when a valve lags or fails to respond to a controller’s initial signal. When the controller sends a second signal to compensate, the valve responds but travels further than it should, resulting in greater process and, consequently, product variability.

Similar to deadhead, hysteresis results in the valve responding inaccurately or inconsistently to a controller signal. In this case, the valve response differs between the upstroke and downstroke. For instance, consider a pressure control valve exhibiting hysteresis. A 10% increase in signal might cause a 100 psi jump in pressure, while a 10% decrease causes a reduction of only 80 psi. The result is process variation that can compound into larger-scale equipment failure if left unaddressed.

Stiction is a combination of “stick” and “friction” used to describe a valve stuck in a certain position. The controller must send a larger signal to force the valve to change position, which causes the valve to overshoot the desired position and get stuck in the new undesired one.

Due to the often hazardous nature of the chemicals employed, processing facilities in the chemical industry require precise control over fluids. Control valves allow facility workers to maintain appropriate pressure, temperature, and flow levels during operations, including for abrasive, acidic, corrosive, and other chemicals.

In food and beverage processing operations, control valves (and other equipment components) must comply with strict sanitation standards. They are used to control the flow of materials ranging from steam and water to slurry and mash.

In the marine industry, control valves are used for precise liquid flow regulation and control to ensure systems maintain optimal operating conditions.

Control valves are found in a wide range of power plant equipment and systems, including boilers, blowers, heat exchangers, and turbines.

In water and wastewater treatment facilities, control valves regulate water flow and pressure. In particular, they are often employed in boiler systems to control the feeding and discharge of treated water and negate the effects of corrosion and scaling.

Control valves are used in wood drying and pressing operations to mix or divert thermal fluid flow, depending on how much moisture is present in the raw wood material.