A valve actuator is the mechanism that opens and closes a valve. Manually controlled valves require someone present to adjust them with a direct or geared mechanism linked to the valve stem. You can find these devices from different brands such as Honeywell, Belimo, Danfoss, etc.
To begin, valve actuators are one form of control valve. It consists of a box with an input, an output, and a mechanism for operation. Before you make your selection, there are a few things you should be aware of, which include:
- The actuator should not be too expensive.
- It has an intrinsic failure mode action.
- Low supply-pressure requirements
- Easily adapt to altering situations.
- Easily maintained.
Types of valve actuators
Now that we’ve defined a valve actuator, let’s look at the many types that exist. The bulk of them fall into common categories and are classified depending on the power applied and the type of movement required:
Pneumatic and hydraulic actuators (fluid power)—quarter-turn
They are well-known for their versatility and are employed in situations where electrical power is scarce or when dependability and simplicity are critical. They have several capacities. For starters, they are little actuators that give a few inch-pounds of torque, while the larger ones may generate millions of inch-pounds of torque or more.
They have a cylinder that is connected to some device that converts linear motion to quarter-turn motion, which is required for valve functioning. Not only that, but they have an extra opposing spring with a positive shut-down in an emergency.
Multi-turn pneumatic or hydraulic actuators (fluid power)
Multi-turn valve actuators help to operate a linear-type, valve-like gate valve or a globe valve. People rarely utilize electric actuators for this purpose, although pneumatic and hydraulic actuators are feasible options in situations when energy is unavailable.
Electric valve actuators, multi-turn
They are the most popular actuators and you will encounter them almost everywhere. They are also quite reliable. They are capable of quickly working some of the largest valves and may be powered by a single or three-phase electric motor. They are made up of gears and spurs. Furthermore, they gear and spur drive a stem nut, which engages the valve stem to open or close it.
Electric valve actuators—quarter-turn
Its design is similar to the multi-turn electric actuator; the main difference is that the final element is located in one quadrant and rotates 90 degrees. They are particularly compact in this kind and are frequently utilized in tiny valves due to their low power consumption.
Manual Actuators
Manual valve actuators do not require an external power source to move a valve to the desired position. Instead, they employ a handwheel, chainwheel, lever, or declutchable mechanism to drive a set of gears, the ratio of which leads to a larger output torque as compared to the input (manual) torque.
For numerous valves, manual operation is not an option, owing to the application’s usage of valves in remote pipes or the sheer force necessary for operation.
Here are three important aspects to consider when purchasing a Belimo valve actuator.
Nature of the application
Two essential parameters influencing Belimo valve actuator selection are media load and desired reaction speed. For example, pneumatic actuators open and close valves fast, but hydraulic actuators can bear higher load.
Electric Belimo valve actuators are very simple to install and use, but they are more susceptible to fire and explosions than other actuators. They cannot be utilized in delicate environments.
Force
The force required to move a valve is referred to as its fore. This could be a rotating force for rotary actuators whereas linear actuators could receive a linear push-pull force.
Several factors impact the force required to operate a valve actuator, including the valve’s size and design, stem packing friction, differential pressure, and valve torque.
This is the amount of force necessary to move the valve from the open to the closed position. In a sliding stem valve, the force required is linear push-and-pull, whereas multi-turn or part-turn valves require rotating effort. To estimate the amount of force necessary, several parameters must be considered, including minimum and maximum supply pressure, actuator type, failure mode, and valve torque.
Aside from that, the force of the media flow should be addressed. The velocity and force of the media can influence the selection of additional linear actuator components like nuts, ball screws, and motors. The impact force of the media will help you choose the proper size and capacity of the motor of the actuator.
Easy to use
Tasks, from going to the beach to controlling valves, are more fun and gratifying if they are simple to complete. Actuators play an important role in making valves easier to install and operate. For example, pneumatic Belimo valve actuators are the simplest to install and use, but hydraulic actuators are the most complicated to use and require extensive maintenance.
The good old-fashioned hand wheels are also worth considering in this category. When building valve handwheels, it is important to consider the power and position of the human operator. This entire notion is addressed in human factor engineering in valves. Human factor engineering is the study of evaluating human capabilities and using that knowledge in the design and selection of equipment and procedures.
