Most safety comparisons between hydraulic systems and electric actuators involve issues like workplace cleanliness, slips, trips, falls and hazards related to pressurized fluid, such as leaks and loose hoses. Comparisons with pneumatic cylinders often focus on hearing damage due to noise. However, the most significant safety advantages of electric actuators may lie in their control. Here are seven ways that transitioning from fluid actuators to electric actuators can improve safety in industrial settings:
1. Precise control
Electric actuators provide precise control over motion more economically, ensuring accurate positioning and movement. This precision reduces the chance of errors that could lead to accidents or equipment damage. The higher the repeatability and reliability, the more consistent the operations—minimizing unexpected deviations that could introduce safety or production issues. Electric actuators enable the programming of complex motion profiles and safety sequences, enhancing control over the machinery. This capability reduces human error and helps employees enforce safe operating procedures.
In contrast, achieving high reliability and repeatability with fluid-driven systems can be complex and costly. These systems require controlling position and force simultaneously with servo valves, position feedback and a multi-axis motion controller. Additionally, fluids are more sensitive to environmental contamination, and response time can be slower due to the need for hydraulic fluid or air to move through the system.
2. Fewer failure points
Electric actuators require fewer components than hydraulic or pneumatic systems (Figure 1), reducing potential failure points and simplifying maintenance. On the other hand, fluid-driven systems require components such as pumps/compressors, hoses, filtration, valves, accumulators, breathers, oil, coolers/dehydrators and other infrastructure for monitoring and control. This complexity increases the potential for failure points. The simplicity of the electric actuator design lessens the chances of human error during assembly, operation or maintenance, enhancing overall safety and reliability.
Figure 1. When comparing electric actuators side by side with pneumatic and hydraulic systems, it is easy to understand how electric actuators experience far fewer maintenance and safety issues, including failures. Image courtesy of Thomson Industries, Inc.
3. Real-time monitoring
Electric actuators often come with built-in safety features like overload protection and emergency stop capabilities that can reduce the cost of ownership for equipment for most applications. They integrate sensors more easily and economically to monitor position, speed and load (Figure 2). These sensors detect anomalies and trigger safety protocols if parameters exceed safe limits. These actuators also facilitate real-time adjustments that keep operations within safe boundaries and include fail-safe features such as spring returns or backup power systems. This ensures that during a power loss or system failure, the actuator will move to a safe position. Programs can execute smooth start-and-stop routines, minimizing the risk of sudden movements that could endanger operators or machinery. Operators can program profiles to perform safety checks and initiate emergency shutdowns if necessary—all at a significantly reduced cost compared to fluid-driven systems.
Figure 2. Smart linear actuators are integrated with printed circuit boards (PCBs) to enhance controllability and contribute to worker safety programs. Image courtesy of Thomson Industries, Inc.
Conversely, fluid-based systems require expensive and complex infrastructure to accomplish similar monitoring and control levels. If these systems reach unsafe operating conditions, the user may only realize it after failure has occurred, unless costly monitoring and control platforms are used. For most applications, utilizing hydraulic or pneumatic systems to accomplish complex control is prohibitively costly. These systems prevail over electric actuators in scenarios involving shock loading, extreme environmental conditions, or when an extremely energy dense prime mover is required. Examples include a preload cylinder on a crusher needing to pass uncrushable objects, a crust-breaking cylinder for an aluminum smelting facility or an intensifier for a hydroforming application. Applications that operate in extreme environments often require a fluid-driven solution, but the vast majority do not.
4. Enhanced interoperability
Beyond their inherent safety capabilities, electric actuators can integrate with other plant safety systems far more economically. For example, a Controller Area Network (CAN) bus can be used to connect an actuator’s built-in monitoring to a plant’s distributed control system (DCS), programmable logic controller (PLC) or onboard central processing unit (CPU) for mobile application. This integration enables automatic responses to potential hazards, such as shutting off fuel supplies or closing vents to contain a fire. Many electric actuators already come with onboard processors that can monitor the health and operating conditions of the device.
5. Easier preventive maintenance
In addition to monitoring unsafe operating conditions, electric actuators can track signs of their own wear and tear, reducing the likelihood of breakdowns that could lead to hazardous situations. If there is an incident or malfunction, detailed sensor data can quickly diagnose the problem, logging data that can prevent similar issues in the future. Actuators also require far less maintenance over their lifespan than fluid-driven systems do. Fluid-driven systems provide minimal operating data compared to their electric counterparts in the same cost of ownership range.
Fluid-driven systems require more complex setups with costly external sensors and signal-processing equipment to accomplish the same level of system monitoring. Additionally, these systems require high maintenance to ensure proper functionality and reliability over time. Even the most basic systems require regular fluid and air filtration changes in their regular maintenance cycle.
6. Eliminated risk of accidental fluid injection
Premature hose wear in hydraulic systems can lead to pinhole leaks in hoses where pressurized hydraulic fluid penetrates human skin. Injuries from these extremely dangerous leaks can damage tissues, nerves and blood vessels, causing severe pain, swelling and discoloration at the injection site. If not treated promptly, such injuries may lead to infection, necrosis or even amputation.
7. Remote operation
Electric actuators can handle many challenging environments and operate automatically with minimal human involvement (Figure 3). With the proliferation of onboard microcontrollers, features like proportional integral and derivative (PID) control at the local level can be achieved—reducing the complexity of the control system used at the plant or system level.
Figure 3. These electrical actuators use a synchronization feature to handle uneven load distribution and raise or lower the platforms smoothly and safely. Image courtesy of Thomson Industries, Inc.
Operators can implement closed-loop feedback systems like encoders or resolvers to monitor position, speed and torque in real time and at the equipment level, increasing responsiveness. Most complex plant-wide control systems are limited by scan rate, which can reduce the achievable level of precise control. Using microcontrollers at the application site lessens the burden on the plant-wide controller. This setup can include improved acceleration or deceleration profiles to ensure smooth and predictable motion, reducing the risk of sudden or unintended movements that could pose hazards. Microcontrollers can integrate actuators with supervisory control systems and predict optimal maintenance periods to minimize human intervention.
While fluid-powered systems may handle environmental challenges better than an electric actuator, the frequent need for maintenance and manual control requires much more human presence (Figure 4). This benefit can be outweighed over time by the high cost of ownership.
Figure 4. With the complexity associated with fluid-powered systems, maintenance and safety require much more human involvement compared to electric actuators. Image courtesy of Thomson Industries, Inc.
Tap into the safety advantages of electrical actuators
Many plant managers put safe operations at or near the top of their priority list. However, balancing that risk with cost is always a challenge. The health and safety risks of fluid-based motion control in the industrial space are well known, making the safety benefits of electric actuators an important consideration. Most of these benefits are intrinsic and accessible by connecting one or two wires from the actuator to a network.
Using electric actuators simply involves following standard installation, operation and maintenance protocols. On the other hand, with hydraulic and pneumatic systems, most of the safety risks come from the system itself. Using electric actuators in place of fluid-controlled systems can greatly improve reliability and safety while reducing the cost of ownership for many, if not most, applications. The transition can minimize risks, reduce maintenance demands and optimize operational efficiency. Reach out to your technical support team or a qualified third-party specialist for further guidance.