Warm greetings to all 🤩 in the 18th post on #Day18 ! Today, we will begin to learn about Valves, their advantages, disadvantages, main functions and etch. In this post, linear motion valves will be introduced. Here we go 🏹,
Introduction🧚🏻
Valves regulate the flow of fluids and isolate piping or equipment for maintenance without interrupting the other connected units. They are typically controlled with actuators; use of manual valves may create safety problems in emergency situations. The valves below are categorized into four main types:
Linear motion valves,
Rotary valves,
Self-actuated valves, and
Specialty valves
Linear motion valves🐝
Linear motion valves include any valve that closes by the linear sliding motion of a structure within the valve. These include gate, globe, diaphragm, pinch, and needle valves.
Gate Valves🐞
Gate valves are primarily used for on/off applications. ‼️They are not used to regulate flow.
⛓Gate valves are very common due to their simple design and ease of operation. The gate is raised by a threaded stem to allow fluid flow. Gate valves are not recommended for throttling, or restricting fluid flow by having the valve partially open.
⛏Gate valves are very simple, and operate in either the fully open or fully closed position. By turning the handle on the top, the screw turns and moves the wedge up or down. The wedge is angled so that if wear does occur, the wedge will still be guided into position. When a gate valve is fully open, there is a very small pressure drop across the valve.
Conversely, when the valve is fully closed, it is pressurized and very well sealed. With the appropriate mating of a disk to seal the ring, very little or no leakage occurs across the disk when the gate valve is closed. Gate valves open and close very slowly to prevent fluid hammers and consequent damage to the piping system.
Usage Examples of Gate Valves
Gate valves are found in a variety of industries, such as underground water or sewage disposal applications. They are also commonly found in irrigation and distribution service lines.
Gate valves are suited for high pressures and temperatures, and are also used for low-pressure steam, and non-corrosive gas or oil.
Advantages
Suitable for high temperature and high pressure situations.
Low pressure drop when fully open.
Tight seal when fully closed.
Relatively free of buildup.
Low leakage, low maintenance, and little noise.
Disadvantages
Slow response times requiring large actuator forces.
Prone to vibration when the valve is partially open.
Subject to erosion from the high velocity flow that occurs when the gate is opened, which eventually prevents tight shutoff.
Globe Valves🦉
Globe valves are the most common type of valves for regulating flow. The picture below shows a typical globe valve.
General Info
Globe valves are primarily used for throttling purposes. They are also ideal for situations in which operation is frequent or tight shutoff is desired.
In the pictures below, fluid flows from left to right. The change in elevation within the valve results in high flow resistance and turbulence, and a large pressure drop. Globe valves can only regulate flow in one direction, whereas gate valves can regulate flow in both directions.
Equipment Design
Because globe valves operate with a perpendicular movement of the disk toward or away from the seat ring, the annular space between the seat and the disk close gradually as the valve closes. As a result, globe valves are ideal for throttling purposes and situations in which operation is frequent or tight shutoff is desired.
The plug can be raised or lowered a specific amount to allow fluid to flow at a given rate. The disk-to-seat-ring contact is very close to forming right angles, which allows the force of closing to tightly seat the disk. At this point the plug will just move further down, and there will still be a tight seal. When the valve is closed, there is no blocked-in volume. As a result, globe valves tend to have very little or no leakage around the seat.
👾In single-seated globe valves, the most common type of globe valve, the plug is only guided from the top part of the valve. In double-seated globe valves, the plug is guided from the top and bottom.
🙀Note: High volume noises are created because of the high pressures and large pressure drops through the valves when the valves do not use a technique known as jet independence to break up the noise.
🦯Globe valves can have digital controllers attached to them to control the operating position and the health of the valve. These controllers can identify issues such as: low/dirty air supply, incorrect regulator setting, air leak, stuck valve, excessive friction, or a broken spring. Controllers now offer wireless valve monitoring to make monitoring many valves simple.
Usage Examples
Globe valves are used in many applications which regulate flow. The two globe valves shown below are being used to regulate the flow of water in a filtration process.
Advantages
Efficient throttling with minimal damage to the valve.
Large number of design options.
A pneumatic diaphragm actuator and control system can be added for precise throttling.
Disadvantages
Highest pressure drops of all valves.
Requires a lot of force to open or close the valve.
Expensive.
Diaphragm 🐣
Diaphragm valves are excellent for regulating flow. Turning the wheel of a diaphragm valve will change the flow of the passing fluid.
General Information
When the wheel of a diaphragm valve is turned, it turns a screw that forces the diaphragm to decrease the incoming fluid flow rate. The diaphragm is the only part of the valve that is exposed to the fluid, minimizing erosion effects. The flow passing through the diaphragm is unobstructed by moving parts and free of crevices.
Some diaphragm valves have a spring instead of the screw. This spring holds the valve in the closed position until the fluid pressure becomes large enough to counteract the spring. Large fluid pressures will force the diaphragm into the open position.
Equipment Design
Two general designs exist, straightway and weir. In straightway valves, the pipe is completely straight. This design does not obstruct fluid flow and, hence, it is well suited for slurry and higher-flow applications. The picture shown below is a typical weir-style diaphragm valve, in which the two pipes bend up toward the center of the valve. This design is used for higher pressure applications. Both types of diaphragm valves are excellent in providing tight shutoff.
The diaphragms can be made from a wide variety of materials including natural rubber, synthetic rubber, or Teflon®. The picture below shows several rubber diaphragms. The diaphragms are inexpensive and easy to replace, so maintenance is inexpensive, quick, and easy.
The life of a diaphragm varies greatly depending on the temperature, pressure, and frequency of opening and closing in each situation.
Usage Examples
Diaphragm valves are used in a wide variety of industries including mining, water treatment, and food processing. Diaphragm valves are commonly used in applications where cleanliness, bubble-tight shut off, and chemical compatibility are important, since the fluid inside the diaphragm is free of gaps and moving parts. Diaphragm valves are considered to cause the least contamination, and are often used in high purity applications.
Advantages
Excellent for fluids containing suspended solids.
Maintenance is inexpensive and not required often, given the long life of the diaphragm.
Will not contaminate the fluid, and the fluid doesn't damage the valve.
Disadvantages
Limited to pressures of approximately 50 psi.
Limited to temperatures below 180°F.
Has bad flow characteristics, requires high and varying force to close valve.
Pinch🐢
Pinch valves are excellent at regulating flow and have a wide variety of uses.
General Information
A pinch valve contains a flexible tube that may be pinched to constrict fluid flow. Pinch valves may be used to throttle, or restrict, fluid flow. Pinch valves may also be used to turn fluid flow completely off.
Equipment Design
Pinching is accomplished by applying pressure to the flexible portion of the valve. This may be accomplished mechanically, or can be accomplished by the exertion of fluid pressure.
🐟Mechanical Fluid pressure controlled
One more figure:
Much the like diaphragm in the diaphragm valve above, the flexible portion of the pinch valve body is made of elastomers, natural rubber, or synthetic rubber. Often times the flexible portion is made up of a combination of fabric and elastomers to increase mechanical strength. The flexible portion is referred to as the valve sleeve. The sleeve can easily be detached and replaced.
Usage Examples
While the pinch valve provides a tight seal, the sleeve material is soft, so the valve can seal around solids without damaging them. Pinch valves are therefore well suited for slurries and fluids with suspended solids. Industries that use this technology of pinching flow without damaging solids include pharmaceuticals and food handling.
Advantages
Excellent for fluids containing suspended solids.
Maintenance is inexpensive and not required often, given the long life of the valve.
Will not contaminate the fluid, widely used in FDA regulated processes for this reason.
Disadvantages
Limited to pressure and temperature capabilities of the sleeve material.
Fluid pressure operated pinch valves cannot run under vacuum conditions.
Pinch valves should always start open when starting a pump upstream.
May fail if flow pulsates
If used as the main shut off of flow in a liquid system, the valve pressure must be watched because the pressure will eventually exceed the valve's capacity. If this is the case then the valve will burst.
Needle🦕
Needle valves are excellent for precise flow regulation at low pressures.
General Information
Needle valves can handle a large range of flow conditions including liquid systems, gas systems, systems with solids suspended in the fluid, and vacuum conditions. Needle valves are most commonly used for controlling flow when precise and minute changes in flow rate are required.
Equipment Design
The valve itself consists of a spindle and the needle. The spindle is at the top and is turned to raise or lower the needle. The needle is a long rod with a cone shaped tip. When fluid is flowing through the valve, the entering fluid turns 90° and passes through an orifice, or void, created by the cone shaped tip of the needle. Moving the needle's position changes the flow rate by changing the size of the orifice.
Usage Examples
Needle valves perform well when precise throttling is required at a low pressure. They are often used in processes where a low, constant flow rate must be maintained. Examples of such processes include filling a vacuum tube, or in a process involving a carburetor. A carburetor is a device that combines and mixes two fluids, usually air and fuel, into an internal combustion engine.
Advantages
Performs well a low pressure.
Performs well with system fluids that are gas, liquid, cryogenic, or fluids with suspended solids.
Can throttle to make small and precise adjustments in flow rate.
Can be used under vacuum conditions.
Disadvantages
Takes a long time to fully close and fully open. Also takes a long time to change flow rate by a large amount.
Does not perform well under high flow rates.
Easily damageable by large changes in system flow rate or system pressure.
References📖
http://encyclopedia.che.engin.umich.edu/Pages/TransportStorage/Valves/Valves.html
Gas Conditioning and Processing Volume 1, 7th edition
Additional Resources 🧪🔑
You can get deep insight about Process/Chemical Engineering from these sources😉:
https://t.me/OilAndGas/18122- Valve Sizing Sheet
https://t.me/ebookgate/1127- Engineering Fluid Mechanics Book
https://coursemania.xyz/course.html?id=433291- Free course on Fundamentals of Fluid Mechanics
https://t.me/ebookstorage/178- Engineering Heat Transfer
https://t.me/ebookstorage/159- Fundamentals of Engineering Thermodynamics (9th Edition) (2018)
https://t.me/ebookstorage/183-Heat Transfer applications and principles
https://t.me/ebookstorage/171-Design and Operation of Heat Exchangers and their Networks (2020)
https://t.me/ebookstorage/215- Industrial Separation Processes (book)
https://t.me/ebookstorage/214- Advanced Process Engineering Control (book)
https://t.me/OilAndGas- Information about Oil&Gas (mainly arabic lang)
https://t.me/chemical_worlds- Chemical Engineering Books, Quizzes and GATE Study Group
https://t.me/chemical_environmental- Discussion group related to Chemical Engineering Problems
https://t.me/chemicalengineeringworld_cew- Everything related to Chemical Engineering
https://t.me/ebookgate- Chemical Engineering E-books (Telegram Channel)
https://www.youtube.com/channel/UCqioh32NOJc8P7cPo3jHrbg- Piping Analysis
https://www.youtube.com/channel/UCQfMyugsjrVUWU0v_ZxQs2Q -Mechanics of engineered devices
http://chemicalengineeringguy.com/- suggests a wide range of courses in Chemical engineering (you can find free courses on topic of Aspen HYSYS, Aspen Plus)
https://www.youtube.com/user/LearnEngineeringTeam- suggests working principles of every engineered devices, equipment and etch.
https://www.youtube.com/channel/UCR0EfsRZIwA5TVDaQbTqwEQ- suggests great information about pumps, compressors with animation.
Today we have started learning about Valves. Tomorrow, we will continue learning the 2nd part of Valves. Now, time to say goodbye👋🏻 until tomorrow and Stay tuned for more content 😉🌝✨!
✏️Note: If you need one of those books or links, you can contact me via my email or LinkedIn profile.
#process #processengineering #engineering #chemical #chemicalengineering #technical #education #dailypost #newpost #wixsite #day18 #bernoulli #technology #material #materialbalance #mass #massbalance #project #projectengineering #selfdevelopment #challenge #recycle #streams #purge #improvement #fluidflow #flow #fluidmechanics #fluiddynamics #water #waterhammer #contuinity #energy #equations #Pfd #processdiagrams #diagrams #piping #instrumentation #pid #development #examples #study #studentlife #fluidstatics #valves #gatevalves #globevalves #rotaryvalves
Comments