What is a valve actuator and what does it do?
The basic explanation is that actuators move your control valves to a certain desired position by using an outside power source. There are different types of valve actuators, but they all are responsible for performing the following functions.
They must move the Control valve closure member to the position you want. The Control valve closure member is made of up the plug, disc, or ball. The actuator needs to create enough torque to move these things even under severe conditions.
The actuator also needs to be able to hold the control valve closure in the position you desire. This means it needs enough fluid power or spring to take on the dynamic torque that throttling applications create.
The actuator must seat the member with enough torque to ensure the shutoff specification. Actuators should also provide a solution in the event of system failure, like springs or battery power. Their failure positions can be either open or closed. Your actuator needs to be regulated to provide enough operating speed and provide enough rotational travel.
Traditional valve actuators were essentially a geared motor with position sensing switches. Modern-day valve actuators have more advanced capabilities. They not only perform functions of opening and closing valves but can also check on the functional status and wellbeing of a valve as well as offer predictive maintenance data.
Some physical locations are hazardous or precarious to human beings. In these circumstances, an automated controlling device can mitigate the risk to the individuals involved. In some situations, critical valves need to be controlled in situations of emergency circumstances.
The Control valve actuator can reduce the risk of serious environmental mishaps as well as to mitigate damages caused in such situations. When some processes require high pressure and large line sizes, the load of power needed to operate a valve can be very high. In these conditions, the intensified mechanical advantage and usage of high output motors can facilitate easy operation of large valves.
What are the different types of valve actuator?
There are four main types of actuators:
- Pneumatic Actuators
Is the most common form of actuation method. Pneumatic Actuators are highly effective, simple to use, inexpensive when compared to other forms of actuation methods. Reliable, inexpensive to maintain and generally have an extended operating life.
- Electric Multi-Turn & Quarter-Turn Actuators
This is also a ommon and widespread actuator used. The primary advantage of this type of actuator is that all accessories are included in the package and are physically and environmentally safeguarded. It has all the basic functions integrated in a compact housing which can be watertight, explosion proof and in most circumstances, submersible.
Like Electric Multi-Turn Actuators, these actuators are compact in nature and are ideal for smaller valves.
- Fluid Power Multi-Turn & Quarter-Turn Actuators
These forms of actuators are recurrently used when multi-turn output is needed to control a linear type of valve, for example, a gate or globe valve. In normal circumstances, electric actuators are used for this type of valve. Although, if there is no electric power supply available to use, then Pneumatic or Hydraulic motors can be utilised to operate multi-turn actuators.
For Quarter-turn actuation, as automation is growing across industries, physical work is being gradually phased out by technology and automatic controls. The importance of valve actuators to develop an interface between the control and the physical action of a valve has increased. There is a critical need for safe working conditions and process safety that valve actuators can offer.
These Actuators, which function on hydraulics are extremely dynamic. The primary factor attributing this is they can be utilised wherever there is no readily available source of electricity or power.
What kind of Pneumatic Actuators does MASCOT make?
Spring Cylinder Linear Actuator
The MASCOT Spring Cylinder Linear Actuator is a powerful, high-performance pneumatic actuator that provides positive throttling or on-off operation for automatic control valves. The positioner and most sized cylinders are designed for supply pressures up to 150 psi, making very high thrusts attainable in a compact unit.
This actuator is fully field reversible for air-to-open or air-to-close action without additional parts; a spring provides fail-safe operation. The positioner supplies air to both sides of the piston, providing exceptionally stiff, precise movement together with very high frequency response.
Spring Cylinder Rotary Actuator
The MASCOT Spring Cylinder Rotary Actuator combines high torque and pneumatic stiffness with excellent throttling capabilities. These characteristics are designed into a lightweight, rugged, and compact assembly, making the MASCOT rotary actuator the first choice for quarter turn applications. The MASCOT rotary actuator is designed to operate the DISKFLO high performance butterfly valve, the VFLO V-notch ball valve, or other applications requiring precise rotary motion. MASCOT pneumatic and electro-pneumatic positioners are available for throttling applications.
The actuator, cylinder and MASCOT positioner are designed for supply pressures up to 150 psi, making very high torques attainable. The actuator uses a rocking piston for direct conversion of linear motion to rotary motion. The rocking piston assembly combined with a splined shaft and lever eliminates lost motion.
How to choose a Control valve Actuator?
Electric valve actuators can make fluid systems safer and easier to control. They’re especially useful if you need to expand or upgrade your system and make it more complex.
Here are some parameters that can help guide your decision:
- Power Source: first determine your power source, be it (1) Pneumatic (2) Electric or (3) Hydraulic --- you may even consider manual operation of your Equipment.
- Torque and/or Thrust: Consider the general torque, breakaway torque or thrust requirements of the system. Secondary factors that influence the torque or thrust requirements include fluid viscosity and valve size. Voltage & Control Requirements: Determine the current type and intensity of the power source at the site of the actuator installation.
- Valve Mounting Connection: Different flanges, actuators, and mounting environment requirements can limit your choice of electric valve actuator.
- IP Rating: IP ratings, as established by IEC 60529, have different levels of protection against environmental factors such as moisture and dust.
- Enclosure Protection Certification: Similarly, the protective housing and enclosures must be able to act as a barrier against the application hazards that are specific to the environment.
- Fail-Safe: Integrated electric valve actuators can be programmed with automated settings that go into effect if there’s power loss, an emergency, or system failure.
- Modulation: Some actuators can control the fluid flow rate, modulating it, while other allow just a ON/OFF control.
- Application: The fluid material, temperature, and other factors of your intended application can also affect which electric actuator valve will work best.
If you need help deciding which kind of actuator you need, get in touch with our engineers today and we can help you decide.
MASCOT Industrial engineers have over 25 years of experience in providing high quality equipment to the Global Continuous Process Control Industry. Our core products and services include control valves, choke valves, actuated and commodity valves, and associated equipment for both standard and severe service applications.
MASCOT’s Engineering & Manufacturing expertise allows us to provide tailored solutions to our customers’ needs with timeliness and accuracy no matter the process. We aim to exceed our expectations with Better Value highly engineered products, faster delivery (-times) on any process, offering support from first contact through to after-sales and beyond.
For more information about our services, please call us at +61 3 9608 6400 or get in touch via the 'Contact Us' page on our website.