Within hazardous environments, where flammable gases, vapour or dust pose a risk, equipment must be specially designed to operate safely. Explosion-proof actuators are actuators that have been engineered to prevent the ignition of potentially explosive atmospheres. This classification is a core component of the safety and operation of industries such as oil and gas, mining and wastewater treatment. These actuators are explosion-proof primarily because of their sealed casing that prevents any internal sparks or high temperatures from escaping beyond the actuator.
However, not every actuator is designed the same, making it important to carefully consider different technical and safety factors. By finding the right actuator for your industry, you can ensure your operation aligns with regulatory requirements while maximising safety.
What is an Explosion-Proof Actuator?
Actuators fitted with explosion-proof components are critical within hazardous environments, where flammable gas, vapour or dust may be present. Actuators that have been made explosion-proof have been specifically designed to contain any explosion that might occur within their enclosure and thus prevent it from spreading to the surrounding environment. This allows them to continue opening, closing or adjusting valves even in harsh conditions. These explosion-proof features are essential to industries such as oil and gas or mining, where flammable substances are commonly found.
Components of Explosion-Proof Actuators
For an actuator to achieve an explosion-proof certification, it requires an assembly of various components and features working together for protection. Note: We have focused solely on the key design features of that are critical to an actuator with explosion-proofing, which typically include the following:
Specialised explosion-proof enclosure
This is the sealed casing surrounding your actuator that prevents any internal sparks or heat from escaping. This is the most important safety component of your actuator, and is typically made from heavy-duty materials such as cast aluminium, stainless steel, or reinforced polymers. A key feature of the enclosure is its flameproof design, which makes it effective at containing internal ignition and escaping gases.
Cable Glands and Sealing
To receive power, actuators may require cables that feed into the electrical enclosure. When operating in hazardous areas, cable glands are responsible for sealing the point of entry. These glands operate on a dual-action principle that prevents the propagation of flames and contains any internal explosions.
Firstly, glands have a robust sealing system, typically using a rubber seal or elastomer that creates an impenetrable barrier against any dust and prevents an explosion from escaping. Secondly, cable glands also have a flameproof design. If an explosion occurs, the gland's construction enables it to cool and quench the hot gases as they attempt to escape. Cable glands must also carry an appropriate Ex rating that certifies they are safe to use in hazardous environments.
Flame paths
Flame paths are an essential part of an actuator being certified explosion-proof. They are a specialty designed channel, gap or thread that works to contain an internal explosion. Flame paths incorporate precision-machined joints, built within the enclosure, that cool the flame by forcing it through a long, narrow path. As they travel through, they send heat to the surrounding material of the enclosure before escaping at a lower temperature.
Durable materials
Actuators with explosion-proof protection are typically constructed from premium-grade materials that are highly durable and resistant to corrosion and extreme temperatures. Materials such as stainless steel and aluminium alloy are commonly used. These housing materials are also often coated with a polyester or epoxy for added protection against any hazardous environments.
Sensors
Actuators are commonly fitted with sensors, either integrated internally or connected externally, to bolster their explosion-proof protection. The role of these sensors is to monitor the actuator’s position and provide feedback to ensure precise control is maintained. For explosion-proofing in particular, sensors can provide real-time data back to the control system, allowing for any adjustments or shutdowns if anomalies are detected.
How Actuators Can Be Made Explosion-Proof
The primary purpose of an actuator with explosion-proof construction is to prevent any ignition sources and stop any internal explosions from spreading. However, the exact method for achieving an explosion-proof certification will vary depending upon your actuator’s power source. These typically involve the following:
Pneumatic actuators
One of the safest actuators within hazardous environments, because its power source is derived from compressed air or inert gas, which doesn't produce any electrical sparks. Still, though, to ensure no sparks are created from internal friction or mechanical movement, pneumatic actuators are made explosion-proof by making sure the air supply and all components are sealed.
Pneumatic actuators can also have springs installed to ensure the valve returns to its safe position in the event of a power or air failure. They can also operate in extreme heat and high pressures, requiring a design that’s robust and certified to withstand these conditions and operate safely.
Electric actuators
Because of the combination of control circuits, switches and electrical cables present in an electric actuator, there is a significant risk of heat or sparks being created. Explosion-proofing, therefore, is focused on placing all potential ignition sources (i.e., motor, terminal box) within a flameproof enclosure that contains an internal explosion. Additional measures should also focus on using non-sparking materials for internal parts, such as copper-aluminium alloys.
Hydraulic actuators
Like pneumatic, hydraulic actuators are inherently safer because they don’t require electrical components, using pressurised fluid to create power. However, there is still a threat of a fluid leak, which can create a slipping hazard or become dangerous when combined with electrical equipment. Therefore, explosion protection should centre on ensuring hydraulic fluid is contained, with leak-proof designs and robust housing preventing any fluid from escaping.
Solenoid actuators
Solenoid actuators use an electrical coil that generates a magnetic field. To achieve an explosion-proof design, all components that may produce sparks, such as the coil assembly, must be encased within a thick, flameproof enclosure to contain any resulting sparks or heat within its robust housing.
Why are Explosion-Proof Actuators Important?
Enhanced Safety
Actuators built to explosion-proof standards are important for an obvious reason, their design helps to prevent explosions within hazardous environments. With robust materials and a tough enclosure, all of which help to stop any ignition from occurring. This helps to safeguard workers from any injuries or loss of life, while protecting facilities and infrastructure.
Compliance with regulations
For most applications, actuators with explosion-proof construction aren’t just important, they’re required under regulations. In potentially hazardous environments where there is a risk of explosion, regulations such as Work Health and Safety (WHS) legally require you to ensure that ignition sources are not introduced into hazardous areas. This includes the use of specialised equipment such as actuators that are certified explosion-proof. This makes these actuators essential for avoiding costly fines, legal issues or facility shutdowns.
Adaptable and versatile
There are a variety of different actuator types and sizes, meaning you will almost certainly be able to find a certified explosion-proof model to suit your industrial needs. These can cover different power sources, from the precise movements of an electric actuator to the robust strength of a hydraulic actuator, an explosion-proof solution can fit seamlessly into any application.
Applications of Explosion-Proof Actuators
Actuators with an explosion-proof classification are an essential component of a variety of applications. These industries typically include the following:
Oil and Gas
The oil and gas industry requires actuators with an explosion-proof classification to control valves positioned within hazardous areas. Typically, because valves are often responsible for transporting flammable materials such as crude oil and natural gas,
Chemical Processing
Within chemical plants, valves are required to manage chemicals flowing in and out of any storage tanks or processing equipment. Because many of these media are flammable, such as petrol, ethanol, or acetone, an actuator with explosion-proofing is required, with their robust enclosures preventing any internal sparks or flames from creating a hazard.
Wastewater treatment
lthough you wouldn’t typically associate water treatment with the risk of explosions or fire, certain stages of wastewater treatment, such as sludge dewatering or biogas recovery systems, can produce flammable methane and hydrogen sulphide. This can create a potentially explosive atmosphere, necessitating actuators with an explosion-proof classification to maintain safe control of wastewater flow.
Mining
Underground mining operations will often use actuators for a variety of purposes, such as controlling valves, powering conveyor systems and pumps. Mining environments can be extremely hazardous, particularly coal mines, with the potential presence of flammable methane and coal dust. The superior sealing and protection of actuators with explosion-proof construction can help prevent sparks from occurring during mining operations and eliminate any risk of an explosion
Safety and Compliance
The use of explosion-proof actuators is essential for meeting the various stringent industry regulations and standards that ensure safety within hazardous environments. Exact regulations will differ depending upon your industry, but we recommend choosing an actuator that has the proper safety certificates.
In Australia, all equipment for explosive atmospheres must comply with the ANZEx (AS/NZS 60079) standards and IECEx certification. These confirm the actuator has been independently tested to meet rigorous internal standards for safety and manufactured to prevent it from becoming an ignition source. Each actuator will also carry an Ex marking code that indicates its specific protection level. These will include information on the type of hazardous substances (e.g., IIA, IIB, IIC for gases; IIIC for dust), as well as how frequently an explosive atmosphere is present (Zone 1 or Zone 2 for gas; Zone 21 or Zone 22 for dust).
If you have any further questions on safety and compliance, or you're looking for specific safety standards for your location or industry, please reach out to your local authority to avoid any potential legal issues.
How to Choose The Right Explosion-Proof Actuator
Choosing the right actuator for your application requires careful consideration of a variety of factors. These should include the following:
Consider technical specifications
Firstly, you’ll need to make sure you select the right actuator that matches the technician specifications of your application. This should include considering the following:
- Power supply - Firstly, you will need to confirm that your actuator’s specifications are compatible with the power supply available. For example, pneumatic actuators are powered by compressed air, hydraulic actuators use a pressurised liquid, while electric actuators use electrical energy.
- Motion type - You must also choose an actuator with the correct motion type that’s compatible with your valve and application. Actuators can be classified by motion type into linear actuators, which move back and forth in a line, as well as rotary actuators that produce a rotational movement.
- Torque and thrust - Torque and thrust are fundamental components for choosing any actuator. It’s important that you identify that your actuator can generate sufficient force to operate the valve under all conditions.
For more information on how to choose the right actuator specifications, please refer to our guide.
Understand your environment
Once you’ve determined the technical specifications, you’ll need to confirm the actuator meets the explosion-proof classifications, as outlined within the IECEX or ANZEx standards. This can be determined by considering the following:
- Zone - Firstly, you should assess the type of hazardous area you are in, as this will determine the required explosion protection level for your actuator. This is classified into zones (Zone 1 or Zone 2 for gas; Zone 21 or Zone 22 for dust), which indicates how frequently an explosive atmosphere is present.
- Gas or Dust Group - Also important to confirm your actuator meets the parameters for gas and dust. Check your actuator’s Ex for this information (e.g., IIA, IIB, IIC for gases; IIIC for dust).
- Temperature Class - Considering the temperature class of your explosion-proof actuator will be critical for safety. Their temperature class must be suitable for the hazardous area in which it will be used. This is indicated by a “T” rating from 1-6, where T6 is the lowest temperature and T1 represents the highest.
Evaluate Control Type and Fail-Safe Functionality
It’s important to select an actuator with a control type that fits your application. Typically, this will fall into the following two primary control modes:
- On/Off Control - This is designed for a fully open or a fully closed valve position, making it great for operations that require isolation or emergency shut-off.
- Modulating Control - This control type allows for proportional movement according to the input signals, such as 4–20 mA or 0–10 V. This makes it suitable for applications that require precise flow or pressure regulation.
- Fail-Safe Mechanism - If safety is a particular focus for your application, we highly recommend considering a fail-safe mechanism. This can be achieved with a pneumatic spring return or an electric actuator with a battery backup that moves the valve back into a safe position in the event of a power failure.
Explosion proof actuators play an important role in maintaining safety within hazardous environments. By using components and designs that contain any potential ignition sources, you can ensure your business complies with regulations, keeping workers and facilities safe. Fluidflo offers an extensive range of high-quality valve products to suit your workplace. Their explosion-proof actuators are an industry innovation currently in the research, design and certification phase, and coming soon to the market. Please reach out to the experts at Fluidflo for more information.