Control Valve's TOP 3 MOST asked INTERVIEW Question and Answers

Instrumentation and control engineering interview questions and answers.
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Instrumentation interview question and answers help in last minute preparation before giving interviews and also for revising important concepts.
Instrumentation and control engineering is a branch of engineering that deals with measurement of various parameters like flow, pressure, level and flow.
here we would learn important questions such as
How to select packing material of control valve
What is cavitation flashing and chocked flow
What is CV in control valve
Flow coefficient (Cv) is defined as the number of gallons per minute (gpm) at 60°F that will pass through a full open valve with a pressure drop of 1 psi.
Valve Flow Coefficient (Cv) is a valve’s capacity for a liquid or gas to flow through it. It is technically defined as “the volume of water at 60°F (in US gallons) that will flow through a valve per minute with a pressure drop of 1 psi across the valve.”
When selecting valves, choose the closest to the calculated Cv, typically rounding down unless a specified maximum ΔP of a project is exceeded. An oversized valve may cause control issues such as hunting or poor heat transfer (delta T) across a coil due to overflow. Conversely, an undersized valve may not provide enough flow and exceed available ΔP.
The relationship between pressure drop and flow rate through a valve is conveniently expressed by a flow coefficient (Cv)
Cavitation in control valve : In a control valve, if the liquid's pressure falls below its fluid vapor pressure, vapor bubbles will form and these bubbles burst after the pressure is increased beyond the vapor pressure curve is called cavitation in control valve
Flashing and cavitation in control valves : In a control valve, if the liquid's pressure falls below its fluid vapor pressure, and if the downstream pressure remains below the vapor pressure of the fluid, the process condition is called flashing.
Choked flow control valve : Choked flow is the point at which decreasing downstream pressure will not increase the flow through a valve. At this point the velocities are the highest and cavitation at this stage is very severe.
the most widely used packing material is Teflon (PTFE) and Graphite.
As a rule of thumb, PTFE packing materials are suitable up to 200 °C
And Graphite based packing material are suitable up to 600°C.
However, refer individual material datasheet for detailed information.
Fugitive emission requirements must also be checked, and the vendor must be consulted for special environmental protection packing sets.
For example Kalrez Valve Stem Packing (KVSP), Live load packing, Enviro-Seal and Bellows seal have better sealing properties and are less prone to leakage.
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[@AsadPassionateEngineer]

🔴Can you learn from ENGINEER's around the WORLD ? Yes ? For FREE (Without any strings attached) Here is a "Group" where every month we take "Questions" from Engineer around the world and share the Answers with the ENTIRE community So EVERYONE learns and Benefits Introducing !! 👉 "Advanced Instrumentation" WhatsApp Community Where you will learn from 1) Monthly Q&A session on Advanced Instrumentation Topics 2) Learning videos directly on WhatsApp so you learn distraction FREE link to Join WhatsApp Group : 👉 chat.whatsapp.com/G1Aon6ZnbEJFRzDpZEv7ir Also, Learn for FREE on Udemy Revise Instrumentation Concepts with Udemy Crash Course Course Link : www.udemy.com/course/instrumentation-interview-crash-course/?referralCode=654FBA0756575E3BF055 Happy learning and Do share your feedback !!! ALSO, Please find the link to the Free E-book ( I hope you would find it valuable) www.asad-shaikh.com/newsletter-and-books.html And also here is link to my previous book on Diaphragm seals www.asad-shaikh.com/uploads/1/2/7/1/127173248/engineering_diaphragm_seal_for_the_industrail_world.pdf

[@mohsenk5985]

Merci d'avoir produit ce genre de vidéos.

[@svsoleil3255]

What excellent videos! Thank you sir!!!!

[@AsadPassionateEngineer]

Glad you like them!

[@ss-bk8xw]

Thank you .. very useful info

[@rameshhariharan2623]

Thisis great simple to understand

[@Instrumentation010]

Amazon video thank you ❤

[@user-jv9ib4bw4q]

Thanks

[@abdulgaffarmohammedshafee9333]

Mr. Asad.Dear Sir. can you explain why fallow on Cavitation in the the pressure vessels (P1,P2)

[@AMANKUMAR-pe3ys]

Very informative..... thankyou

[@AsadPassionateEngineer]

Most welcome !! and thank you to you as well for your constant support. 😊

[@Ovoi248]

Your video is very helpful. Can you please answer the following Shouldn’t we consider the position of valve opening ie Fully opened valve when stating the Cv definition.

[@AsadPassionateEngineer]

Yes you are absolutely correct 😊 will make a separate video about covering this point also engineers get confused about concept of calculated CV at min, normal and Max flow and the valves rated CV so will cover this as well. Thanks for your comment 😊

[@tariqueanwer9329]

Dear Sir, your all videos are always very informative and helps us to understand easily. Sir, for control valve which book you prefer .

[@AsadPassionateEngineer]

Tony K Rudalp's Lessons in industrial instrumentation is a pretty good book

[@Sreeram.G]

Next question by interviewer : How to overcome capitation and flashing in the control valve?

[@AsadPassionateEngineer]

I am working on this video, It might be a little longer one, But i am trying my best to make it as interesting as possible 😊

[@Gokuvegeta-fx5db]

Cavitation can be overcomed by using hard trim material like stellite and Colmonoy 6 and using multi stage trim. Flashing cannot be avoided however it's effect can be reduced by placing the valve at a high pressure area or using a downstream restriction device such as a restriction orifice so that the due to backpressure effect the pressure recovers above the vapour pressure of the liquid

[@akankshasharma9000]

Where is the link ?

[@prabhatsingh5377]

Sir kindly make a detail video on woodward governer control

[@AsadPassionateEngineer]

Sure Prabhat !!

[@harrietmono-rq3ko]

Please mention terms in full like GPM or CV, DP sometimes people are new to the entire concept

[@AsadPassionateEngineer]

Yes good point.👍 For people new to concept : GPM - gallons per minute D.P -differential pressure

[@SurajSingh-wk1tk]

if valve it is 10 cv then what is the meaning of 10?

[@ramkumark9789]

Thanks for the video...but I believe this topic is discussed in ur old video

[@AsadPassionateEngineer]

Thank for following, And yes i am making videos on Solutions to cavitation etc in the upcoming videos 😊

[@prabhatsingh5377]

Sir where is the link for E-book ?

[@AsadPassionateEngineer]

My apology, the link is now shared in the Pinned comment 😄

[@ranjithgowda6327]

Where is the E-BOOK link sir

[@AsadPassionateEngineer]

My apology, the link is now shared in the Pinned comment 😄

[@abdessamedghettas7167]

Thanks

[@AsadPassionateEngineer]

Most welcome !! and thank you to you as well for your constant support. 😊