What is a Control Valve?
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- เผยแพร่เมื่อ 6 ก.ย. 2020
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A control valve is a power-operated device used to regulate or manipulate the flow of fluids, such as gas, oil, water, and steam.
It is a critical part of a control loop and is an example of a final control element. The Control Valve is by far the most common final control element used in industry today.
A control valve has two separate components: the Valve and the Actuator.
Valve bodies are of different types or styles depending on service conditions, piping layout, and desired application. The two classes of control valves are Linear Motion and Rotary Motion.
On a linear motion valve, the stem and valve movement is up and down. A common type of sliding control valves is the Gate Valve.
A rotary motion valve in almost all cases rotates 90° from open to the closed position. A commonly used rotary valve is the Butterfly Valve.
The actuator is the device connected to the valve through the valve stem that provides the force required to move the valve.
The actuator can be controlled electrically, pneumatically, or hydraulically. The most common and the most reliable is the “Pneumatic Actuator”.
The control valve receives a signal from a controller such as a PLC or a DCS in order to operate. The controller compares the actual flow rate to the desired flow value called the setpoint.
The controller will produce an output to move the valve to bring the flow rate to the setpoint value.
Because the PLC signal is electrical, the control valve may require a device to convert that electrical signal so that it can operate.
Because of how pneumatic actuators are built, a control valve will fail to a specific position when a loss of the control signal occurs.
As the supply air pressure is increased, the rubber diaphragm pushes against the spring and moves the valve stem down into the valve body.
As the supply air pressure is reduced, the spring will move the valve stem out of the body.
The position to which the control valve is moved if a loss of signal occurs is referred to as the fail-safe mode.
The type of fail-safe mode depends on the application for which the control valve is used.
The actuator causes the valve to close in a Fail-Closed Control Valve.
The actuator causes the valve to open in a Fail-Open Control Valve.
In normal operation, the force of the spring must be overcome by the electrical or pneumatic actuator.
In the event of a power failure to the actuator, the electrical or pneumatic force is no longer present and the spring pressure forces the valve to open.
You might wonder how much the valve opens or closes when the flow rate changes. Well, that depends on a number of things such as the percentage of the flow rate change and the diameter of the pipe.
Regardless, the Controller must be tuned so that it produces the correct response to any change in flow rate. This is most commonly achieved by using PID control within the PLC or Controller.
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We have already created several easy-to-follow videos on what a PID Controller is:
What are PID Tuning Parameters? (realpars.com/pid-tuning-param...)
How to Program a Basic PID Loop in ControlLogix (realpars.com/pid-loop/)
What is a PID Controller? (realpars.com/pid-controller/)
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I spent a whole week I think when I was in school learning about control valves for the first time, you explained it in five mins. Great job!
That's amazing, great to hear that it helped you out, Bobby!
I would like to know English at the beginning of my industrial automation course so that I can have better results.
What did you go to school for? And what was particular class?
Thank you! I greatly appreciate the enormous effort you put into creating those animations, which really help with the understanding of the physical phenomena occurring in these systems. Please keep up the good work.
Hey!
Thanks a lot for your kind compliment! We are always extremely happy to hear such positive feedback.
If you ever have any questions, feel free to reach out to us.
Happy learning!
Another great video from realpars. Clear and concise with great graphics.
Glad you enjoyed it! Thanks for your positive feedback!
You are an incredible team of teachers.
Thanks for your kind comment, Ricardo! I will pass your compliment on to our team.
Estos videos no dejan de mejorar! Excelente, no pierdo la esperanza de que se narren en español para llegar a mas personas!
Congrats! Great Job!
Muchas gracias, Jorge!
Thank you once again. Especially for the use of video animation to drive your point home.
You're very welcome, Samuel! Thanks for your support.
Hello RealPars,
You guys have been amazing so far. I'm always anticipating you your video lessons. However, to fully understand the control valve and their service function, I think you should make a video lessons on the ANALOG POSITIONER.
Best regards
Hi Obafemi,
Thanks for your comment and sharing your feedback with us.
We truly appreciate that, and I will make sure to forward your suggestion to our course developers.
Thanks again and happy learning!
Tremendous effort sir... Thanks
Good work. Thanks for your effort to produce this issue
Our pleasure!
This channel is amazing😍
Thank you!
Another well made and didactic video! Thank you!!
Thank you, Bruna!
it was clear explanation for control valve functionality. Thanks!
Glad you liked it! Thank you for sharing.
Truly wonderful video, animation and explanation. Fantastic!
Many thanks, Brett!
Nice graphics, well explained, may need to have a look at the fail closed graphic though. The spring would be above the diaphragm to push it closed in failure.
Absolutely fantastic. Loved it👍👍👍
Amazing! That's great to hear, Abdul!
Thanks. I loved updates
Nice graphics, well explained! Keep doing what you do!
Thanks a lot for your kind comment, Frederic! Happy learning, feel free to reach out if you have any questions.
It's really interesting. Thank you. I learn from your videos. 👍👏🌺
Great to hear, happy learning!
Great video. But is recommended to install the electromagnetic flowmeter before the control valve, it can prevent empty pipe that produces wrong measuring of the flow.
Really dish channel very good and nicely teaching
Eternally grateful! Thankyou!!!
Glad it helped, Luke!
Very Thanks Sir.
Thankyou, very helpful and intresting to learn and understand.
Glad you enjoyed it! Happy learning
Very good quality content
Your channel very useful, thank you so much and request plz put video on calibrate and troubleshooting..
Hi Renold!
Thanks for your comment and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
Very good presentation !!!
Thank you very much!
Great knowledge, thank you very much
Glad it was helpful!
Fine information
I'm a student of electrical and electronic engineering, and I'm a really big fan of you.
Glad to hear that, Hossain! Happy learning
Thanks for knowledge 👍😁
You're very welcome, thanks for watching!
Very good presentation!
Thank you!
You videos and your channel are amazing
Can I ask you which program did you use to make a simulation
😀
I always watch this channel to improve my automation engineering
We are very happy to hear that! Feel free to reach out if you have any questions along the way.
Happy learning!
When I see new video uploaded by u , then I am happy
Best channel on TH-cam
Thanks a lot, Ben!
Thanks for uploading
Our pleasure, Andrés!
Thanks!
Thank you
Awesome knowledge you have been sharing. Go head
Thanks for watching!
Thats amazing job, I love the way you explain it, I would love with software you use for animation?
Thanks in advance
Hi there,
Thanks for your kind comment!
To answer your question, I am not sure about this as this is done by our graphic and animation department.
Sorry about that!
Great, i love this content
Thank you!
Thanks💓
Thanks for this knowledgeable video.
Glad it was helpful!
Thank you for saving me
Glad it is helpful!
Thankyou sir very helpful
Happy to hear that!
This animated videos put the knowledge inside ur head 4ever.
Thank you so much!
REALLY thanks 😊
You're very welcome!
Hi thank you for your great clips. Please make a clip about chemical processes and how to control the loop and adjust the loop in chemical processes and petrochemicals. For example, loop adjustment methods and loop control strategies in petrochemicals that produce methanol or ethylene.
Hi Farzad!
Thanks for your comment and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
nice explaination
Thank you very much!
ممتاز ،،، إمضي .
Excellent ,,, go ahead .
Thanks a lot!
I am interested on this learn. Thank you.
Great to hear that!
I really like your amazing videos. Can you make video about the resolver and how does it work. compare to encoder and what is the different between these two kinds of position sensors.
Hey!
Thanks for your comment and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
Dear RealPars
This is another awesome video, I would like to ask if it is possible to make a video on slip ring and how can we change it to a wireless slip ring with keeping the high voltage (400v) with a normal sleep ring and all what concern data and signal with the wireless one if it's possible
Thanks in advance!
Hi Messaoud,
Thanks for your kind comment, and for the topic suggestion, I will definitely go ahead and forward this to our creator team.
Happy learning!
Sir can discuss about burner,thank you keep educating us,god bless
Thanks for the topic suggestion, I will definitely go ahead and forward this to our creator team. Happy learning!
Can you do another video on advanced print reading? The videos that you did on prints are way too simple and don't show the complexity of most prints in the real world. A lot of people think they can read print but have a hard time finding what they are looking for when they are given a stack of prints or prints with lots of details. Thanks
Thanks for the feedback, Eric! I will surely pass this on to our course developers. Hopefully, this is something we can focus on in future video courses.
This video is great
Thank you!
Great animation! In which program did you made this? Thank you
Thanks a lot! I'm actually not sure about that, as this is done by our graphic and animation department.
great channel I like you .. from egypt
Thanks! 😃
谢谢😊
Hey my friends, thank you for your spectacular effort. May I know the name of the software used in creating this great illustration ?
Thanks for your support, Medo! We're happy to receive such positive feedback. Regarding your question, I am actually not sure about that as our illustrations are created by our Graphic and Animation Department.
Go on. Thank you.
You're very welcome!
Hello, what software do you use while preparing your videos? I want to use them to make very fluent presentations.
Hi Enis,
Thanks for your comment!
I am actually not sure about that, since our video courses are created by our animation and graphic department.
Plz make video on how I/p transducer works ,how it modulates the air flow.. it's working and mechanism...
Thanks for your comment, and for sharing your topic suggestion! I will happily go ahead and forward this to our course developers.
Thanks again, and happy learning!
Great😍😍
Is there any video explains how to size a control valve? Valve calculation as well.
You just picked my brain. I'm actually working on that as we speak. Send me an INMAIL on LinkedIn, Obafemi Jimoh. We could share idea about that.
Do you have Aspen Hysys or INtools for sizing and calculation?
@@obafemijimoh918 I use the software provided by the valve manufacturers. A lot of them will run the calculations and then give you a list of models they make that will work with those parameters.
@@Ryarios Are you on LinkedIn? If you are please connect with me. Valve sizing is out of my instrumentation scope but I'd love to know how I can independently size one and and prepare it's calculation and specification.
dear sir, what are the advantages of pneumatic control valve compared to motorized and what brand of PLC is the controller?
The main advantage is that a pneumatic control valve has a fail position that the valve returns to when the air signal is lost power loss or failure of the instrument air system. A motorized valve will simply stay in the last position on power loss, which may be in a position that allows fluids or gas to continue to pass. This can be dangerous if that fluid is natural gas or a dangerous chemical. I am not sure which PLC you are referring to. The video is a "digital twin" simulation of a process installation, and the controller shown looks like it could be a Siemens S7-1500 PLC.
Hi, pl make a video about mil (make) control valve calibration and troubleshooting video. Thanks
Hi Gopal,
Thanks for your comment and feedback! I will make sure to pass this on to our course developers!
Good 👍
You are amazing
Happy learning!
This video is amazing, i want to know everything about PLC and engineer, can u tell me training about plc alan bradley?
We could work something out. Do you have the RS Logix software?
I dont have, how i can download the RS Logic software new edition?
I have the full set-up. But the challenge is how to get it across.
@@obafemijimoh918 can i get it free? You can convey it simply, i will understand
Hi Bagas,
Thanks for your comment!
Although we mostly focus our course videos on Siemens, we do have a couple of course videos on Allen Bradley. We are planning to add more courses to our Allen Bradley section in our course library, but we do not have any of those courses scheduled yet.
Feel free to have a browse through our course library to see which topics we cover at the moment. bit.ly/30ZrxWq
I hope this helps- please let me know if you have any other questions, and I'll do my best to assist.
I liked the way the animation works Can I know the name of the program in which to make the graphics?
Hi there,
Thanks for your kind comment! I am not sure about this as this is done by our graphic and animation department.
Sorry about that!
@@realpars 🌷
Thank you 🌷
Sir I want to know about BMS working do you have any videos related to BMS
Thanks for your topic suggestion, Rajesh! I will happily pass this on to our course developers.
Happy learning!
What is the voltage that is supplied to the control valve which causes it to change its position?
Hi @Eshan Patil. Thanks for your question. Most control valves are pneumatic and operate in a full stroke range of 3 to 15 psi or 20 to 100 kPa. But, there is usually a converting device called a Voltage to pressure (E/P) or a Current to pressure (I/P) to convert the signal from the controller into a pneumatic signal to stroke the valve. The valve will begin to move at 1v if an E/P is connected or 4 ma if an I/P is connected. I hope that answers your question.
Do you have any videos on how to stroke control valves?
Hi @Nathan Dowlen. No, unfortunately, we do not. but that's a great idea. Thanks!
@@realpars Yeah, I'm just trying to understand some basic process operations.
Input air pressure also should be checked.
There is an error here, typically the flow meter is upstream of the control valve to minimize flow disturbances
nice
The flowrate before and after the control valve is the same?
Yes, the flow rate is the same at the inlet and at the outlet. Unless there is a serious leak around the stem of the valve, a control valve is a flow-through device
@@realpars what I don't understand how the control valve changes the flow rate.
@realpars
How is flow rate regulated if it is constant (or the same) before and after the valve?
Hi to all, what software is used to create these type of videos? Can somebody let me know? please
Hi Alberto,
Thanks for your comment! Regarding your question, I am actually not sure about this as our course videos are created by our graphics and animation department.
Please make a separate video only about positioner
Hey!
Thanks for your comment and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
Good 🎉
Thank you!
Please make a video of connection of an rtd that controls the on and off of the heater...thy has to be indications of each process....the whole process should be ran by a plc and pid
Thanks for your topic suggestion and feedback! I will happily pass this on to our course developers.
Thanks again and happy learning!
I love programming I m electrical engineer ted sir
Thank you!
I think practically control valves are place after flow meters , first flow is measured then everything comes thereafter...
This video is an amazing start. I wish I could have helped offer a few additional points before it was made. Or saw this when I was learning in the job. there are issues / limitations of each technical choice. My experience is that hydraulic actuators are more robust, respond quicker, more reliable, able to work better on larger valves with a smaller footprint. There can be issues but that is more a maintenance issue. Pneumatic valves also require good maintenance and quality instrument air. They work great for on off valves. They have less control because air within the actuator compresses. If you choose a butterfly valve instead of a globe valve you have less control. The valves have a leakage class and shutoff time requirement. They valves can have lvdt, position sensors or limit switches to communicate if it is behaving properly. Often valves are calibrated with a factory supplied cv curve that is custom to that exact valve. This information needs to be updated to account for variations from the standard values. There opening profiles like pop and glide.
With liquid, there may be no issues but with gas, due to compressibility, this can be an issue due to restrictions.
On another note, this may not be to scale, the distance from the valve to the flow meter may be large enough not to bother.
Regards.
For liquids it does not matter, but mostly I have seen control valve at upstream of flowmeter (whether it is gas or liquid).
Thanks.
Hi
I would like to do online course (plc,DCS,scada,HMI,VFS)
Please guide me the process
Hi Siraz,
Great to hear your interest!
We have a course library filled with over 400+ video courses. You obtain full access to our complete course library by subscribing to either our monthly package for €22.12 a month or our yearly package for €159.28
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Hope this helps! If I can be of any further assistance, please let me know - I’m more than happy to help!
👍👍👍
can you make video on Different softwares for siemens.
Hi Adil!
Thanks for your comment and your suggestion. I will pass this on to our course developers!
Thanks for sharing and happy learning!
@@realpars thank you
@@realpars entire video or a short series dedicated for softwares only.
Plz make video on IoT in brief.
Thanks for the topic suggestion, I will definitely go ahead and forward this to our creator team. Happy learning!
Flow meter location?
Typically the flow meter is upstream of the control valve
But in video graphics downstream show
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Thanks !
You're very welcome!