CONTROL VALVES
9Pages

Introduction: Fluid flow ratio regulation appliances, which keep the required regulation characteristics, are critical in industrial automatics systems. The main component of such appliances are controllers, which adjust the resistance for flowing fluid, and drives (actuators), which provide mechanic energy required in setting of controllers. The following are representatives of this group of appliances, manufactured by Varimex-Valves • globe and angle control valves, • three-way control valves, • butterfly valves. Regarding the type of drive, controllers are manufactured in following executions: • with spring diaphragm pneumatic actuators, • with electric and electro-hydraulic actuators, • with pneumatic piston actuators, • with hand operated drive, • without drive. • Regarding the fact that valves are the largest group of controllers, the expression “valves” is hereinafter often interchangeable with expression “controllers”. While selecting valves for specific working conditions one should consider the following aspects: 1. valve design version, 2. material execution, 3. nominal pressure, 4. flow coefficient, 5. flow characteristics, 6. internal tightness, 7. bonnet type and packing, 8. body connection types, 9. hardening of valve internal parts, 10. selection of drive, 11. harmful effects in valve operation. VARIMEX VALVES CO.LTD

CONTROL VALVES - TECHNICAL INFORMATION 1. Design versions: The design version aspect applies only to valves. Valves can be subdivided using the following criteria: a) position of body inlet and outlet • globe, • three-way, • angle, b) closing component • with linear motion valve plug, • with rotary motion valve plug, c) shape of closing component • profile valve plug, • perforated valve plug, • multi-stage valve plug, • cage valve plug, d) balancing of axial forces • unbalanced, • balanced, e) reversibility of operation • reversible design double-ported valves, • irreversible design...

CONTROL VALVES - TECHNICAL INFORMATION 2. Material executions: Material execution is determined by material in which body is executed. Basic material executions of the body casts: - cast iron: EN-GJL 250, per PN-EN 1561 - spheroidal iron: EN-GJS-400-15, per PN-EN 1563 EN-GJS-400-18LT, per PN-EN 1563 - carbon steel: GP240GH, (1.0619), per PN-EN 10213-2 G20Mn5, (1.6220) wg PN-EN 10213-3 WCB, per ASTM A216 - alloy steel: G17CrMo9-10, (1.7379), per PN-EN 10213-2 WC9, per ASTM A217 - stainless steel: GX5CrNiMo19-11-2, (1.4408), per PN-EN 10213-4 CF8M, per ASTM A351 Criteria for selection of...

CONTROL VALVES - TECHNICAL INFORMATION It is advised that DIVENT valve calculation and calculation program is used, which can be downloaded from the following website To ensure correct work of automatic controls and to avoid oversizing of the valve, adopted catalog value of flow coefficient is to be higher than calculated. It is assumed that maximum value of calculated flow coefficient is to be achieved within the 70…90% range of valve plug stroke. 5. Flow characteristic: Valve flow characteristics is the relation between flow value and closing component stroke. Regarding pressure drop we...

CONTROL VALVES - TECHNICAL INFORMATION Valve plugs with quick opening characteristics are designated exclusively for on-off operation. Limitations in application of perforated components are due to their susceptibility to contaminants suspended in fluids, hence the need for their permanent filtering. - flow coefficient (calculated) - fluid flow volume intensity - gas flow volume intensity in normal conditions (0°C, 760 mm Hg) - flow mass intensity - absolute pressure upstream valve - absolute pressure downstream valve - pressure drop on valve (available pressure drop) - fluid density...

CONTROL VALVES - TECHNICAL INFORMATION V VI Allowable leakage [blister / min.] 1 2 3 4 do D = 25 Allowable leakage [bubble / min.] 6 11 27 45 Checking the internal tightness is carried out as part of acceptance tests of the product with the use of air with pressure 3…4 [bar] (for valves in classes II, IV and VI) and with water with working pressure conforming to the order (for valves in class V). Valves in class VI have seats (single-seat valves) or plugs (two-seat valves) equipped with packing rings made of PTFE reinforced with glass fibre. Because of durability of the packing material,...

CONTROL VALVES - TECHNICAL INFORMATION Among maintenance-free packings are PTFE-V and TA Luft packings. PTFE-V ones are executed in PTFE in the form of V-profile rings, pressed to sealed surfaces with spiral spring. TA Luft packing comprises two kits of seal rings loaded with package of disk springs, and compliant in terms of tightness requirements of TA Luft:2002, Clause 5.2.6.4, and VDI 2440:2000. 8. End cannections, types: Body connections are used to connect valve to pipeline and they should provide tightness, pressure resistance, vibration resistance and pipeline deformations. Valves...

CONTROL VALVES - TECHNICAL INFORMATION 10. Selection of drive: Valves and butterfly valves can be equipped with spring diaphragm pneumatic actuator, piston actuator, electric actuator, electro-hydraulic actuator, handwhell, or no drive at all. Equipment without drives can be completed by end user with other types of actuators, such as springless diaphragm pneumatic, piston pneumatic acutator, crank actuator, and others, provided that such actuators are adapted to connection with valve bonnet and valve plug stem. Hand operated equipment is mostly used for applications requiring on-off...

CONTROL VALVES - TECHNICAL INFORMATION • position transmitter, • limit switches, • lock-up valve, • volume booster, • quick exhaust valve. Handwheel is applied in case of control signal failure, as well as to limit valve stroke. Application of positioners is recommended in following cases: • for systems requiring large pressure drops on valve, • for high working pressure, • for valves of nominal diameter DN > 100 mm, • for distance between valve and reducing valve exceeding 50 m, • for three-way valves, • for systems requiring high-speed action, • for viscous or highly contaminated fluids...