What are control valves and how do they work?

To begin with, Control Valves are used to control the flow of fluids such as liquid, gas, and steam by partially opening or fully opening or vice-versa. 

The control valve consists of three main parts each of which available in different types and designs 

  •  Valve body 
  •  Valve Actuator 
  •  Valve positioner

The opening and closing are usually done by actuators. The actuators can be operated electrically or pneumatically or hydraulically.

Pneumatic actuators are most commonly used in industrial automation because of their simplicity. It just requires compressed dry air to work.

The standard input pressure range to the actuator is 3 to 15 psi. We have all come across this terminology 3 to 15 psi in automation here is where it is used.

Types of Actuators:

1) single acting( spring return ) actuators 

  • Air to open actuators
  • Air to close actuators 
                             

           The single-acting actuators need input air supply either to open or close depending on the type of the actuator.

2) Double acting actuators: 

               The double-acting actuators need input air supply for both the actions (to close or open ).

Actuators are driven by the output of the positioners based on the input electrical signal ( 4 to 20 mA ) or pneumatic signal ( 3 to 15 psi ) to the positioners.

Types of positioners :

             1) pneumatic positioners

            2)electro-pneumatic positioners

Electro-pneumatic positioners - 

                   In this case, the positioner is a built-in I/P converter. Thus the electrical signal from the controller such as PLC or DCS is directly given to the positioners. It is also called smart positioners.


The control valve in the image is a single-acting air to open with a smart positioner. 

Pneumatic positioners -  

                It has two input air supply. One is regulated air supply from the main air header and another one is from the I/p converter. The signal from a controller such as PLC or DCS is an electrical signal ( 4 to 20 mA ) and I/p converts are used to convert that electrical signal into a pneumatic air signal for the pneumatic positioners.

Positioners that are available with one output are used to control single-acting actuators and two outputs are used to control double-acting actuators.


Comments

  1. You've written an excellent post, and you've shared it with us. Your article provided me with some unique and useful knowledge Through Conduit Gate Valve. I appreciate you sharing this text with us.

    ReplyDelete
  2. I always check this type of advisory post and I found your article which is related to my interest.Private Industrial Valve Manufacturing This is a great way to increase knowledge for us. Thanks for sharing an article like this.

    ReplyDelete
  3. I liked your work and, as a result, the manner you presented this content about PP Sight Glass.It is a valuable paper for us. Thank you for sharing this blog with us.

    ReplyDelete
  4. It is great post thanks for sharing this post. You have give an informative information about Magnetic core material. Your article is useful for everyone. Keep it up.

    ReplyDelete
  5. Your blog contains lots of valuable data about roxtec. It is a factual and beneficial article for us. Thankful to you for sharing an article like this.

    ReplyDelete
  6. You are providing good knowledge. It is really helpful and factual information for us and everyone to increase knowledge. about castle valve .Continue sharing your data. Thank you.

    ReplyDelete
  7. It is used to control fluid flow by varying the size of the flow passage in response to a control signal. Check out this helpful guide on how air operated pump is changing industries.

    ReplyDelete

Post a Comment