Attention: Bm³ and Nm³ may often differ from each other owing to the compressibility of the medium. Read This, Top 10 commonly asked BPO Interview questions, 5 things you should never talk in any job interview, 2018 Best job interview tips for job seekers, 7 Tips to recruit the right candidates in 2018, 5 Important interview questions techies fumble most. stellite hard facing). During operation they are kept closed by the internal pressure of the vessel. 1, 2 and 3 b. Why is it advisable to extend the pipeline in some cases? Multiple Choice Quiz: Multiple Choice Quiz This activity contains 15 questions. Valve components will tend to vibrate whenever they are subjected to high velocity turbulent flow. Linear trim will give better control at flow rates over 50% of the valve capacity. On gases and vapours the velocity at the exit of the valve body should be less than 0.33 Mach (1/3rd of sonic) for noise control valves and less than 0,5 Mach where noise is not a consideration. Bm³ : Volume of the medium (liquid or gas) in the operating mode. Increases accounting errors III. When two of such devices are associated, in our case on water and steam line, the minimum and maximum controllable flow of the system as a whole could be affected by other factors. What is the difference between a start-up and continuous bleeding valve? This compares with generally accepted line velocities of about 3 m/s, which explains why control valves often are smaller than the line size. Three methods exist for treating cavitation in control valves – the first is to ensure that the plug and seat are made of a material that can resist the damage (e.g. for a ball valve that has an inherent equal percent character it is possible to make it appear linear so that the flow rate through the valve at 50% signal is half of the maximum flow – the valve will however only be 25% open to achieve this result. Why Do Different Control Valves Have Different Characteristics? It is possible to predict where cavitation will occur by looking at the pressure conditions and the valve recovery factor. What is the difference between “Rangeability” and “Turn-down” in a steam desuperheating system ? 1. Which parameters are important for the selection of the nominal diameter apart from the Kv(s) values)? Lessens the risks of intentional irregularities IV. 2. If pressure ranges are given, the smallest pressure difference is relevant with regards to valve design.. Play as. Question 7. The velocity is one of the more important considerations in sizing a control valve. Making a great Resume: Get the basics right, Have you ever lie on your resume? Hard face trim (using hard facing materials such as Stellite, or Tungsten Carbide), Increase size of valve, thus reducing the velocity. The change in flow resulting from a fixed increment of valve travel is constant throughout the whole stroke. The pipeline extension is to be carried out by the customer. 15 signs your job interview is going horribly, Time to Expand NBFCs: Rise in Demand for Talent. They are provided with a lever transmission thus they also operate at very low or very high pressures. Also Read: Control Valves Questions & Answers, Dear sir I want more information for subject thank you sir. Control lines can enhance the regulating properties and are used to realize special applications (e.g. which will improve your skill. Previous Story ← 6 Common Pitfalls for Pumping Chocolate. Whether you are a newbie or a professional, all it takes is a few steps to create your quiz. These are all different states or phases in which a fluid can exist. Question 17. D. magnet ... (this multiple choice question has been scrambled) The QRS complex represents: A. atrial repolarization What is the valve seat? Question 2. Normally the term control valve is used to describe a valve that controls flow with an externally adjustable variable restriction. Use the choked pressure drop in any equation to calculate Cv or flow rates. Question 9. 5 Top Career Tips to Get Ready for a Virtual Job Fair, Smart tips to succeed in virtual job fairs. The valve seat is the apron for a defined flow through opening in the valve through which the medium to be regulated has to flow. In such a case they will act as bleeding valves without venting function. In the case of diaphragm actuated valves, the stiffness is much lower and so the flow direction must always be under the plug, resulting in the need of a heavy spring to give fail closed action. The third is to control where the bubbles collapse and keep this away from vulnerable components (for instance close to internal surface of valve body or pipe). sir plz discribe about throtiling of c.v. Other name for seating control valves….are called packaging!The material menu be of neoprene or as as per the grade of section is required!! The second is to control where the bubbles collapse and keep this away from vulnerable components (see Cav Control trim). Temperature – Maximum temperature for design plus temperatures at maximum, normal and minimum flow conditions. The pressure acting on the control surface closes (pressure reducing valve) or opens (backpressure regulator) the valve against the spring force. Will Separable Flanged Valves Seal In A Pipeline? Choked flow is not necessarily a problem in valves but does need to be taken into account in the Cv calculations. Regulators should be referred to as self-regulating control valves to avoid confusion. Question 5. Cavitation is a condition that occurs in liquid flow where the internal pressure of the liquid, at some point falls below the vapour pressure and vapour bubbles formation takes place. Question 34. Some valve designs require control lines to safely transmit the required set pressure to the control unit. Some plants stipulate that no control valve should be less than two sizes smaller than the line size, other that the valve should not be less than half the line size. What Process Date Is Required To Size A Control Valve? Question 24. This occurs with liquids that are viscous, working at low velocities. Equal Percentage – For equal stem movements the change of flow resulting from the movement is directly proportional to the flow rate immediately before the change took place. The overall noise level produced will be lower as the overall number of pressure drop stages are increased. All Control valves cause pressure drop in the fluid as it passes through the valve. Attemporators are used more in power stations for interstage temperature control. Not every pressure regulating valve requires a control line. Practically the most significant difference between liquids and vapours/gases is the compressibility. The control deviation indicates the extent of the variation. What is the difference between a pressure reducing valve and a pressure maintaining valve? By means of the cone stroke the valve is opened, throttled or closed. The basic pneumatic valve is a mechanical device consisting of a body and a moving part (poppet or stem), which connects or disconnects passages within the body. SIGNIFICANTLY HIGHER CONTROL RISK THAN THAT ASSESSED IN PRIOR AUDIT. Pneumatic Control System Multiple Choice Questions and Answers; 36. The Kv value of the valve should reach this Kvs value. Question 32. Definition Of Linear And Equal Percentage Characteristic? Adaptive gain is used for controlling processes. A check valve is a/an: directional control valve counterbalance valve reducing valve 2. 1 13. 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