06-03-2013, 02:13 PM
HIGH PRESSURE DROP CONTROL VALVE 56
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COMPANY PROFILE
Instrumentation Limited was established by Government of India in 1964 at Kota, as an indigenous source for total C and L packages. The Palakkad unit was set up in 1974 for the manufacture of fluid control elements .IL has completed 25 years of highly fruitful and successful collaboration with M/s YAMATAKE HONEY WELL and it is still continuing.IL have supplied more than 3,00,000 products significantly to the export market with supplies to erstwhile USSR, Rumania, Hungary, Saudi Arabia, etc. The manufacture and testing of valves established at the Palakkad plant serves as one of the best high-order productivity plant ensuring quality and reliability.
The quality assurance and inspection standards adopted by IL conform to the latest international standards and all the products moving out of the Palakkad plant bear a stamp of high degree of quality and reliability. Some of the special tests conducted by Instrumentation Limited facilities include dynamic response testing, helium leak testing, radiographic inspection, clean room facility, ultrasonic and magnetic particle testing ,CV test laboratory, etc .The excellent sub-vendor base development by the Palakkad unit caters short team delivery requirement of fast track project
INTRODUCTION
Process plants consist of hundreds, or even thousands, of control loops all networked together to produce a product to be offered for sale. Each of these control loops is designed to keep some important process variable such as pressure, flow, level, temperature, etc. within a required operating range to ensure the quality of the end product. Each of these loops receives and internally creates disturbances that detrimentally affect the process variable, and interaction from other loops in the network provides disturbances that influence the process variable.
To reduce the effect of these load disturbances, sensors and transmitters collect information about the process variable and its relationship to some desired set point. A controller then processes this information and decides what must be done to get the process variable back to where it should be after a load disturbance occurs. When all the measuring, comparing, and calculation are done, some type of final control element must implement the strategy selected by the controller.
CONTROL VALVE
The control valve regulates the rate of fluid flow as the position of the valve plug or disk is changed by force from the actuator. To do this, the valve must:
1. Contain the fluid without external leakage.
2. Have adequate capacity for the intended service.
3. Be capable of withstanding the erosive, corrosive, and temperature influences
of the process.
4. Incorporate appropriate end connections to mate with adjacent pipelines and actuator attachment-means to permit transmission of actuator thrust to the valve plug stem or rotary shaft.
Many styles of control valve bodies have been developed through the years. Some have found wide application; others meet specific service conditions and are used less frequently. The following summary describes some popular control valve body styles in use today.
HIGH CAPACITY, CAGE GUIDED VALVE BODY
This adaptation of the cage-guided bodies mentioned above was designed for noise applications such as high pressure gas reducing stations where sonic gas velocities are often encountered at the outlet of conventional valve bodies (figure 6). The design incorporates oversize end connections with a streamlined flow path and the ease of trim maintenance inherent with cage-style constructions. Use of noise abatement trim reduces
overall noise levels by as much as 35 decibels. Also available in cageless versions with bolted seat ring, end connection sizes through 20-inch, Class 600, and versions for liquid service.
Flow direction depends on the intended service and trim selection, with unbalanced constructions normally flowing up and balanced constructions normally flowing down.
ROTARY VALVES
BUTTERFLY VALVE BODIES
Bodies require minimum space for installation (fig.9). They provide high capacity with low pressure loss through the valves. Butterfly valve bodies offer economy, particularly in larger sizes and in terms of flow capacity per investment dollar. Conventional contoured disks provide throttling control for up to 60-degree disk rotation. Patented, dynamically streamlined disks suit applications requiring 90-degree disk rotation. Bodies mate with standard raised-face pipeline flanges. Butterfly valve bodies might require high-output or large actuators if the valve is big or the pressure drop is high, because operating torques might be quite large.
ECCENTRIC PLUG CONTROL VALVE BODIES
Valve assembly combats erosion. The rugged body and trim design handle temperatures to 800o F (427o C) and shutoff pressure drops to 1500 psi (103 bar). Path of eccentric plug minimizes contact with the seat ring when opening, reducing seat wear and friction, prolonging seat life, and improving throttling performance (fig 12). Self-centering seat ring and rugged plug allow forward or reverse flow with tight shutoff in either direction. Plug, seat ring and retainer are available in hardened materials, including ceramics, for selection of erosion resistance. Designs offering a segmented V-notch ball in place of the plug for higher capacity requirements are available.
BALL VALVES
Ball valves are the name implies are stop valves that use a ball to stop or start the flow of fluid the ball performs the same function so the disk in the glob valve when the vale handling is operated to open the valve body inlet and outlet when the valve shut required only a 90 degree rotation of the hand wheel for most valve he ball is rotated so the hole id perpendicular to the slow of the body and the flow its stopped. Most ball valves are of quick acting type (required only a 90 degree turn to operate the valve .either completely open or closed).bout many are planetary gear operated.
This type of gearing allows the use of air relatively small hand wheel operating time for the valve some valves contain a swilling check located within the valve to give a check valve features ball valves are normally found in the following system aboard ship ,sea water, sanitary ,trim and drain ,air hydraulic, and the air oil transfer.
SPECIAL CONTROL VALVES
Special control valves can handle a wide range of control applications. The range of standard applications can be defined as being encompassed by: atmospheric pressure and6000 psi (414 bar), −150o F (−101o C) and 450o F (232o C), flow coefficient Cv values of 1.0 and 25000, and the limits imposed by common industrial standards. Certainly, corrosiveness and viscosity of the fluid, leakage rates, and many other factors demand consideration even for standard applications. Perhaps the need for careful consideration of valve selection becomes more critical for applications outside the standard limits mentioned
above. This chapter discusses some special applications and control valve modifications useful in controlling them, designs and materials for severe service, and test requirements useful for control valves used in nuclear power plant service.