Introduction to the Types of Valves Because of the diversity of the types of systems, fluids, and environments in which valves must operate, a vast array of valve types have been developed. Examples of the common types are the globe valve, gate valve, ball valve, plug valve, butterfly valve, diaphragm valve, check valve, pinch valve, and safety valve. Each type of valve has been designed to meet specific needs. Some valves are capable of throttling flow, other valve types can only stop flow, others work well in corrosive systems, and others handle high pressure fluids. Each valve type has certain inherent advantages and disadvantages. Understanding these differences and how they effect the Valve’s application or operation is necessary for the successful operation of a facility. Although all valves have the same basic components and function to control flow in some fashion, the method of controlling the flow can vary dramatically. In general, there are four methods of controlling flow

  Control Valves body Valve Body The body, sometimes called the shell, is the primary pressure boundary of a valve. It serves as the principal element of a valve assembly because it is the framework that holds everything together. The body, the first pressure boundary of a valve, resists fluid pressure loads from connecting piping. It receives inlet and outlet piping through threaded, bolted, or welded joints. Valve bodies are cast or forged into a variety of shapes. Although a sphere or a cylinder would theoretically be the most economical shape to resist fluid pressure when a valve is open, there are many other considerations. For example, many valves require a partition across the valve body to support the seat opening, which is the throttling orifice. With the valve closed, loading on the body is difficult to determine. The valve end connections also distort loads on a simple sphere and more complicated shapes. Ease of manufacture, assembly, and costs are additional important consi

  Control Valves positioner A control valve positioner is a device used to operate the actuator of a control valve to increase and decrease the air load pressure until the valve stem is in equilibrium with the output signal of the process variable instrument controller. Because valve positioners know the exact position of the valve, they provide more precise control than the actuator can achieve on its own. In addition, positioners improve accuracy in the lower part of the valve stroke, where errors are more common. Positioners help control valves respond more quickly to changes in process variables, allowing the system to operate above or below setpoint. Consistent valve position, even with different pressures. Varying pressures on the valves can indicate instability in the control loop. A positioner is a device that helps to stabilize the position of the valve. A positioner allows you to set the distance between the controller and the control valve as well as use a diaphragm or pis

  Hydraulic Actuators Hydraulic Actuators, as used in industrial process control, employ hydraulic pressure to drive an output member. These are used where high speed and large forces are required. The fluid used in hydraulic actuator is highly incompressible so that pressure applied can be transmitted instantaneously to the member attached to it. What is a Hydraulic Actuator ? when a large amount of force is required to operate a valve (for example, the main steam system valves), hydraulic actuators are normally used. Hydraulic actuators come in many designs, piston types are most common. A typical piston-type hydraulic actuator. It consists of a cylinder, piston, spring, hydraulic supply and return line, and stem. The piston slides vertically inside the cylinder and separates the cylinder into two chambers. The upper chamber contains the spring and the lower chamber contains hydraulic oil. The hydraulic supply and return line is connected to the lower chamber and allows hydraulic flu

  What Is a Linear Actuator? A linear actuator changes the rotational motion of a motor into a straight line. Conventional electric motors move in a circle, while linear actuators move forward and backward. The push and pull action allows the device to slide, tip, and lift items with the push of a button. The design provides operators accurate and precise control over the production. The fluid movement means the linear actuator requires minimal maintenance over its lifespan and comes with natural energy efficiency. They are easier to install than their hydraulic or pneumatic counterparts, cost less, and take up significantly less room. When to Use a Linear Actuator Manufacturers leverage linear actuators in tools and industrial machines, such as printers, sprayers, computers, and valves. Choosing an actuator depends on the product, with hydraulic actuators powering hydraulic car jacks and pneumatic actuators often powering pistons and ignition chambers. Each of these devices offers an

  Electric Actuators Introduction An electric actuator is a mechanical device used to convert electricity into kinetic energy in either a single linear or rotary motion. It automates damper or valve in order to increase process efficiency and complexity. Designs for electric actuators are based on the specific tasks they accomplish within the processes for which they’re intended, and they can vary in both dimension and size. The motor of an electric actuator can operate on any voltage and is used across many different industries. The most common voltages used in single-phase motors are 115 VAC, 24 VAC, 12 VDC, 24 VDC, 208 VAC and  230 VAC. In addition to these options, three-phase motors also use voltages of 230 VAC and 460 VAC. An actuator’s brake is mounted on top of the motor. It’s responsible for stopping the media from forcing the valve open when it should be closed by locking the motor rotor in position when not in use. The motor start capacitor is the third main component of an

  pneumatic actuator A Pneumatic actuator mainly consists of a piston or a diaphragm which develops the motive power. It keeps the air in the upper portion of the cylinder, allowing air pressure to force the diaphragm or piston to move the valve stem or rotate the valve control element. The valves input is the “control signal.” A simplified diagram of a pneumatic actuator is shown in Figure a. It operates by a combination of force created by air and spring force. The actuator positions a control valve by transmitting its motion through the stem. A rubber diaphragm separates the actuator housing into two air chambers. The upper chamber receives supply air through an opening in the top of the housing. The bottom chamber contains a spring that forces the diaphragm against mechanical stops in the upper chamber. Finally, a local indicator is connected to the stem to indicate the position of the valve. The position of the valve is controlled by varying supply air pressure in the upper chambe

  Control Valves actuator Introduction Pneumatically operated control valve actuators are the most popular in use. Actuator are also widely used. The pneumatic spring and diaphragm actuator is most commonly specified due to its reliability and simplicity of design. Pneumatically operated piston actuators provide high stem output power for demanding service conditions. The adaptations of the pneumatic and spring piston actuators are available for direct installation on rotary shaft control valves. Electric and electro-hydraulic actuators are more complex and more expensive than pneumatic actuators. They offer advantages where an air supply source is not available, where low ambient temperatures could freeze condensed water in pneumatic supply lines, or where unusually large stem forces are needed. Below is a summary in which the design and characteristics of popular actuator styles are analyzed. An actuator is an assembly fitted to the control valve to provide power for moving the move-

  Types of Fast-acting On/Off Valves with Built-in Actuators Solenoid Valves Solenoid valves operate using a linear sliding obstructer that opens and closes the valve, or changes the flow from one outlet to another. There are many different types of obstructers used including plunger, shuttle, spool, and diaphragm. The linear motion is achieved by energizing an electromagnetic coil to pull the obstructer in one direction. A spring drives the obstructer back in the opposing direction when the coil is de-energized. 2-position on/off valves are the most common type of solenoid valves, but there are a vast number of others, including 3-position where there are 2 coils that pull the obstructer in opposite directions, using springs to center it when neither is energized. There are even proportional solenoid valves that can be used for flow control. In these valves, the coil moves the obstructer varying distances based on the voltage supplied to it. Solenoid valves are relatively small. Their