Control Valve Actuators - Types and Failure Modes

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Control Valve Actuators

• Types and Failure Modes Discussed

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Control Valve Actuators

• The control valve actuators are the triggering
  units in control valves. These actuators are
  responsible for generating the motive force
  needed to operate the valves. The actuators can
  be operated using different types of energy
  provision systems such as hydraulic, pneumatic,
  manual, electrical, etc.
• Therefore, there are multiple types of valve
  actuators. Different types of actuators offer
  different operational parameters and performance
  efficiencies. Also, different types of these
  actuators feature different design specifications
  and scope for failure during applications.
• While using the actuators, it is essential to
  understand the types, and failure modes. That is
  why this post introduces valve actuators,
  different types, and failure modes for them.

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Different Types of Control Valve Actuators

• The following are the three main types of valve
  actuators.
• Pneumatic Actuators This valve actuator is
  pneumatically operated. This type of actuator
  features a pair of diaphragm and springs that are
  linked to each other. As the signal is received
  from a control system, the diaphragm and spring
  react to the force causing movement of the valve
  stem.
• There are two types of pneumatic actuators
  available.
• Direct pneumatic actuators
• Reverse pneumatic actuators

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Different Types of Control Valve Actuators
(contd.)

• Hydraulic Actuators These actuators share
  several similarities with pneumatic actuators.
  Hydraulic actuators feature a piston-rod
  arrangement of diaphragm and spring. The pistons
  are filled with hydraulic fluid. As the signal
  comes from a control system, the rod moves
  forward or reverse, based on which the actuator
  force increases or reduces. The valve stem is
  actuated by hydraulic force.

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Different Types of Control Valve Actuators
(contd.)

• Electrical Actuators The electric actuators
  feature a motor-operated trigger as the actuating
  element. These actuators can generate linear or
  rotary action of the valve. These actuators are
  commonly used for ON/OFF operations however, they
  can be used for continuous processing if
  integrated with a feedback loop. This way, these
  actuators can be automated.
• Note These main types of valve actuators can be
  merged together for enhanced performance. The
  hybrid types of valve actuators like
  electro-hydraulic, pneumatic piston controlled
  actuator, etc are available.
• The actuators can be designed according to
  different failure modes. Let us discuss the same.

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Failure Modes of Actuators

• Commonly, the failure modes of actuators are
  achieved as either fail open or fail close. The
  following designs are adopted to achieve one of
  the failure modes. For the design to achieve a
  specific failure mode, the following two
  combinations of the valve body and actuator
  combinations are used.
• Air to Close Valve (ACV) In this type of
  combination, a reverse acting actuator is
  connected to the reverse body or vice versa. This
  combination fails the open valve if operated in
  open condition.
• Air to Open Valve (ATO) In this type of
  combination, a reverse actuator is connected to
  the direct valve body. This combination fails to
  operate if the close circuit conditions.

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Failure Modes of Actuators

• Since the type of actuator makes a high impact on
  the performance of the control valve, the
  actuator should be of verified quality. That is
  why you should source valves and actuators from
  the trusted suppliers like The Transmitter Shop.
  The company holds 50 years of experience in
  supplying high-quality transmitters, control
  valves and actuators, and related process control
  equipment.

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The Transmitter Shop

• Contact US
• Address 2531 Preston, Pasadena, TX 77503
• Toll Free 1-888-964-8837
• Local 281-487-3115
• Fax [phone]
• Email sales_at_transmittershop.com
• Website https//www.transmittershop.com/