Industrial processes rely on different process valves to regulate fluid flow through pipelines and equipment. These valves are pivotal for increasing the autonomy of various industrial processes and maximizing the productivity of fluid applications. An automated valve is any flow control device controlled by an actuator. The actuator connects to the valve stem or valve closure mechanism, manipulating the position of the disc to provide the desired flow conditions.

Automated valves are suitable alternatives to manually operated valves that require human intervention to open or close. Facilities can enjoy more precise and consistent flow control using actuated control valves that respond to parameters like pipe pressure, temperature, and flow rate. These valves operate faster than their manually operated counterparts.

What are the advantages of automated control valves, and how do they influence the efficiency and reliability of industrial processes?

Valve Actuation Mechanisms and Their Importance

A valve actuator provides the force needed to operate control valves and regulate fluid flow through a piping system or industrial process. The automated system alters the position of the valve closure mechanism, seats a valve’s disc, ball or plug to provide fluid shut-off and regulates the speed of valve movement in response to prevailing flow conditions. Actuators offer several advantages ranging from swift valve responsiveness, predictable, safe, and durable valve performance and better remote operation and monitoring of valves spread across a facility.

Factors to Consider When Choosing a Valve Actuation Mechanism

The choice of valve actuation mechanism depends on:

• Valve cycling requirements - high-pressure, frequently cycled applications require actuators that respond faster to changes in flow conditions without losing their efficiency in the long term. It is advisable to evaluate the duty cycles of different process valves to identify the most suitable actuator size and type.
• Type of process valve - industrial processes rely on rotary and linear valves in different sections of the piping system. Valves with a sliding stem require a linear actuator, while a motorized ball valve, butterfly valve, or globe valve utilizes a rotary-type actuator. Each actuator provides the desired torque or thrust to manipulate the valve and regulate or control fluid flow.
• Actuation speed - one can choose between a fast and slow-acting actuator to meet system performance characteristics (fluid pressure and temperature). A fast-acting actuator is best suited for systems with repetitive throttling, whereas a slow-acting actuator proves beneficial for mixing process fluids bearing different chemical and physical properties.
• Safety requirements of the piping system - valves are installed in different locations and exposed to various hazards that can cause premature failures and compromise the safety of processes, equipment and facilities, operators and technicians and the immediate environment. Actuators chosen for different fluid applications should provide reliable fail-safe mechanisms should they lose power or miscommunicate with the control system. Actuators can use a spring-return or fluid-powered accumulator as fail-safe mechanisms or battery backups for electrically-powered actuators.
• Valve usage area - actuators can suffer premature damage due to installation in aggressive environments and the corrosive effects of the service media. Consider the application area to select the appropriate actuator housing material and connection methods to reduce damage by the environment and the service media.

One is likely to interact with the following types of actuators when thinking of automating valve operations in a facility for better performance and safety. 

Types of Valve Actuators for Industrial Applications

Electric Actuators

Electric actuators have versatile designs featuring a two-way motor and a speed reduction mechanism — usually a miniature gearbox. The speed reduction system maximizes the torque from an actuator to operate process valves. Electric actuators receive signals as voltages or currents and convert them to force, modulating valves. These actuators are reliable for light-duty valve modulation and are usually maintenance-free. They are also easy to install, operate quietly and require less energy to work.

Advanced electric actuator designs have provisions for limit switches to stop motor rotations when the valve is at a fully open or fully closed position. One can only utilize electric actuators if one can access an uninterruptible power supply. These actuators are also very sensitive to vibrations. They may overheat if frequently cycled.

Pneumatic Actuators

Pneumatic actuators are popular for automating various industrial valves and can be single or double-acting. Pneumatic actuators contain inlet and outlet ports to convey compressed air and manipulate the position of pistons or plungers. Instrument air in the actuator causes linear or rotary plunger motion, delivering adequate torque or thrust, lifting the stem, and causing the valve to open or close. Some pneumatic actuators contain solenoids to enhance their performance and provide a more precise feedback loop to maximize the responsiveness and sensitivity of the actuator.

Pneumatic actuators have compact and lightweight designs. These actuators are powered by compressed air, making them the most economical valve automation options for facilities with multiple valves. Pneumatic actuators respond faster to changes in flow conditions and provide adequate force for throttling and overcoming inertial forces in pipelines conveying viscous media, slurries, or high-pressure systems like industrial steam pipelines.

Hydraulic Actuators

Hydraulic actuators, like their pneumatic counterparts, rely on fluid power to operate. They utilize hydraulic fluid in place of compressed air. Hydraulic actuators are popular in pipelines with heavy-duty process valves. These actuators are available in double and single-acting configurations. The actuator has a cylinder containing a plunger connected to the valve stem. The fluid pressure within the cylinder initiates linear or rotary motion to manipulate the position of the valve closure mechanism and regulate fluid flow.

Hydraulic actuators provide large actuation forces and feature sturdy housing designs for applicability in harsh environments. Some downsides of hydraulic actuators include:

• Sensitivity to temperature changes
• High maintenance requirements
• Hydraulic actuators are more expensive to acquire.

Electro-Hydraulic Actuators

Electro-hydraulic actuators use electric motors to drive hydraulic pumps, generating the hydraulic force required to alter valve positions for predetermined flow control. These actuators are more precise since the electrical signals dictate the speed of motors and valve strokes. Electro-hydraulic actuators provide high actuation forces, are low maintenance and are silent when operating. 

Benefits of Automated Control Valves in Industrial Processes

Automated control valves are beneficial in several ways. They overcome challenges associated with manual valve operations and allow facilities to control large process valves, centralize real-time performance monitoring of multiple valves and optimize their sensitivity, precision, and safety.

Improved Process Efficiency

Automated valves are more accurate. They eliminate human errors in process control and facilitate precise control of service fluids. Facilities can enjoy better product qualities since they experience fewer process stops due to delayed valve operations and faster valve response times based on dynamic control signal changes. Companies can improve process cycle times, and in return, they maximize product quality and yield.

Companies can enjoy more predictable processes with reduced downtime due to valve failures or improper operations. Companies can equip automated valves with diagnostic technologies for real-time valve monitoring and collect data required to improve valve designs, operation, and maintenance standards. Actuated control valves contain systems to alert operators or technicians on existing valve malfunctions, providing adequate time to repair or replace a damaged or poorly performing process valve.

Automating valves enhances efficiency in all facets of operations. It includes limiting unnecessary movements across the facility to manually open or close process valves, inspect valves and diagnose valve defects. Companies can enjoy improved energy efficiency since automated valves consume less energy. Valve operations are based on real-time flow conditions. This can optimize energy utilization and help companies control and reduce energy-related costs.

Enhanced Safety Standards

Automating process valves minimizes human intervention in industrial, commercial and domestic fluid applications. This reduces human errors, preventing accidents and minimizing the severe impacts of emergency valve failures. The automated valves rely on control signals to open or close valves at specific intervals and follow a predefined sequence. The consistency and accuracy of valve operations help prevent damage to equipment and pipelines. Proper and predictable process control significantly improves safety in facilities.

Actuators can provide automated valve shut-off should a system upset occur. For instance, programmed, automated valves can shut off when the control systems detect excessive leakages or fugitive emissions beyond the recommended levels. Companies can establish a remote monitoring system that prevents operators from working close to valves or accessing hazardous locations to operate, maintain or exercise less frequently cycled process valves. 

Predictable Valve Maintenance Needs

Valves are designed to offer reliable, long-term fluid service. Maintenance enhances their longevity and efficiency, allowing companies to recondition old valves, replace damaged components and recalibrate instruments for precise fluid control. Companies can analyze valve data to establish how different cycling requirements affect valve performance. The automated systems make it easy for facilities to develop condition-based or predictive valve maintenance programs.

Automating process valves is a reliable way to control valve maintenance costs by establishing and sustaining proactive maintenance programs focused on addressing root causes of valve defects, failures and anomalies, lowering their performance and durability. Companies can leverage historical data to streamline maintenance scheduling and implement corrective or preventive maintenance measures based on valve cycling frequency, age, and properties of the service fluids. 

Case Study: Explosion at Formosa Plastics Corporation

The Formosa Plastics Corporation explosion occurred in October 2005. The accident resulted from unsafe work practices and progressed due to flaws in valve design. The facility was rocked by explosions that led to the injury of several employees and the propagation of fire for several days.

Investigations by the US Chemical Safety and Hazard Investigation Board revealed that the explosion was due to the vaporization of the highly flammable propylene fluid. A manual valve on one of the storage tanks was left partially open. The partially open valve released the liquid, which vaporized and exploded after ignition.

The leakage was reported in time to employees in the control room. The operators managed to shut down sections of the facility fitted with automated valves. The emergency response did not yield the desired results since the critical shut-off valves were manually operated and hard to access based on the prevailing safety conditions during the incident.

The Formosa Plastics Corporation accident highlights safety risks associated with manual valve operations in hazardous environments. It would have been easier for control room operators to shut down and isolate sections of the facility to mitigate the spread of fire. Manually operated valves are difficult to monitor. If Formosa had automated valves across the facility, the operators could have received alerts about the affected valves. Employees could have ample time to respond, shutting affected valves down and remedy the situation.

The Formosa accident lays bare the advantages of automated control valves. There is little human intervention in the operation of process valves, with the human operator actively participating in remote control and monitoring. This reduces the probability of errors and ensures the correct sequence of plant shutdown during emergencies. The automated valves open and close at the right time and force, preventing additional damage due to panic. The severity of the accident would have been lower because:

• Automated valves would have shut down once the system detected a reduction in storage tank pressure preventing the leakage that caused fluid vaporization.
• Condition-monitoring sensors on the valve could detect fluid leakage and generate a timely alert for employees to evacuate the facility and operators to initiate an emergency shutdown and activate safety utilities like firefighting equipment.
• Remote operation of automated valves would have prevented the attempt by employees to close shut-off valves manually despite the prevailing safety risks.

Final Thoughts on Automated Valves in Industrial Processes

Automated valves are indispensable fluid control devices when dealing with aggressive fluid media, managing fluid flow using multiple valves and operating in aggressive environments. These valves are beneficial for optimizing the safety of facilities and the productivity of industrial fluid systems. It takes time and heavy financial investment to automate valves across a facility. It is advisable to audit facilities to identify critical processes requiring immediate automation. Monitor trending fluid control technologies to ensure you invest in the most reliable automation technologies for seamless operations. Engage a valve expert to size and select the appropriate automation solution for your facility.