Transcript Slide 1
VALVE AND CONTROL VALVE What’s the Different? Valve: biasanya digunakan sebagai isolasi atau safety, kebanyakan sistem kerja/ kontrol bersifat mandiri (self actuated) tidak perlu sinyal kontrol atau penggerak Control Valve: mempunyai fungsi elemen akhir atau sebagai actuator dengan penggerak (close or open) bergantung dari sinyal kontrol Secara umum fungsi dari valve: a. To control the rate of flow (throttle); b. To shut off/permit flow (ON/OFF function); c. To isolate systems and protect products. Regulating Valves Regulating valves are used extensively in piping systems to regulate the flow of fluid. Backflow Prevention Valves are generally used for the prevention of backflow. The valves are selfactuating and the valve disc is kept open by the forward flow of fluid Pressure-Relief Devices Pressure-relief devices are used to protect piping and equipment from being subjected to pressures that exceed their design pressures. The main types and their uses are 1. Gate Valve Used for shut off - ON/OFF function. 2. Ball/Plug Valves Used for shut off - ON/OFF function 3. Globe Valves Used for control of flow and shut off. 4. Butterfly Valves Used for control of flow and shut off. The main types and their uses are ……………. 5. Relief Valves: Spring loaded to open at a given pressure, and used to protect systems from over-pressure. 6. Check Valves: To allow flow in one direction only. 7. Fusible (gabungan) Link Valves/Piston Operated Valves: Quick acting and used for emergency shut off. 8. Twin Sea valves: Used when tight shut off required. 9. Semi-Needle Valves: Used in conjunction instruments to bleed off (mengeluarkan) part of the flow. 10. Ball Check Valves: Used with gauge glasses as safety precaution. Pilot operated pressure relief valve: A pressurerelief valve in which the major relieving device is combined with and controlled by a self-actuated auxiliary pressure-relief valve. Power actuated pressure-relief valve: A pressurerelief valve in which the major relieving device is combined and controlled by a device requiring an external source of energy Relief valve: A pressure-relief valve actuated by inlet static pressure and having a gradual lift generally proportional to the increase in pressure over the opening pressure (set pressure). Safety-relief valve: A pressure-relief valve characterized by rapid opening pop action, or by opening generally proportional to the increase in pressure over the opening pressure. Safety valve: A pressure-relief valve actuated by inlet static pressure and characterized by rapid opening or pop action. Classification Based On Motion Expansion Valve Expansion valves are designed in accordance with API 6A and can meet the requirements of various working conditions. Gate Valves Gate valves are primarily designed to serve as isolation valves. In service, these valves generally are either fully open or fully closed. When fully open, the fluid or gas flows through the valve in a straight line with very little resistance. Gate valves should not be used in the regulation or throttling of flow because accurate control is not possible. Advantages of Gate Valves 1. They have good shutoff characteristics. 2. They are bidirectional. 3. The pressure loss through the valve is minimal. Disadvantages of Gate Valves The following are some of the disadvantages of gate valves that must be considered when selecting a gate valve for an application: 1. Gate valves are not quick opening or closing valves. Full-stem travel to open or close a gate valve requires many turns of its handwheel or an actuator. 2. Gate valves require large space envelope for installation, operation, and maintenance. 3. The slow movement of the disc near the full-closed position results in high-fluid velocities, causing scoring of seating surfaces, referred to as wire drawing. It also causes galling of sliding parts. Check valves, Check Valve disebut juga “no-return or one directional valve” yang akan bekerja (valve open) jika arah aliran sama dengan arah yang ditentukan dan akan menutup jika terjadi backflow Needle Valves (Swagelok) Bekerjanya berdasar buka atau tutupnya needle (seperti jarum/ batang) yang menekan dudukan flow dari valve Needle Berdasar kekuatan bahannya dapat digunakan pada tekanan tinggi (< 2.000 psi) Butterfly Valve Twin Seal Valve Piston Valve Sepertinya fungsi semua Valve sama bagaimana cara memilihnya??? 1.Melihat P&ID 2.Karakteristik Fluida Kerja/Proses 3.Mengacu pada standard (contoh API) Ball Valves The ball valve is a quarter-turn valve suitable for clean gas, compressed air, and liquid service. They also can be used for slurry service, but provisions for Advantages of Ball Valves 1. Provides bubble-tight service. 2. Quick to open and close. 3. Smaller in size than a gate valve. 4. Lighter in weight than a gate valve. 5. Multiport design offers versatility not available with gate or globe valves. It reduces the number of valves required. 6. Several designs of ball valves offer flexibility of selection. 7. Can be used in clean and slurry applications. 8. High-quality ball valves provide reliable service in high-pressure and high-temperature applications. 9. Force required to actuate the valve is smaller than that required for a gate or a globe valve. Disadvantages of Ball Valves 1. They are not suitable for sustained throttling applications. 2. In slurry or other applications, the suspended particles can settle and become trapped in body cavities causing wear, leakage, or valve failure. Typical Applications of Ball Valves The following are some typical applications of ball valves: 1. Air, gaseous, and liquid applications requiring bubble-tight service 2. Low-point drains and high-point vents in liquid, gaseous, and other fluid services 3. Instrument root valves 4. Cooling water and feedwater systems 5. Steam service Plug Valves Plug valves, also called cocks, generally are used for the same fullflow service as gate valves, where quick shutoff is required. They are used for steam, water, oil, gas, and chemical liquid service. Plug valves are not generally designed for the regulation of flow WE’LL GO TO CONTROL VALVE SECTION