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CONTROL VALVE SIZING

Control Valve Selection Control valves handle all kinds of fluids at temperatures from the cryogenic range to well over 1000�F (538�C). Selection of a control valve body assembly requires particular consideration to provide the best available combination of valve body style, material, and trim construction design for the intended service. Capacity requirements and system operating pressure ranges also must be considered in selecting a control valve to ensure satisfactory operation without undue initial expense. Reputable control valve manufacturers and their representatives are dedicated to helping select the control valve most appropriate for the existing service conditions. Because there are frequently several possible correct choices for an application, it is important that all the following information be provided: � Type of fluid to be controlled � Temperature of fluid � Viscosity of fluid � Specific gravity of fluid � Flow capacity required (maximum and minimum) � Inlet pressure at valve (maximum and minimum) � Outlet pressure (maximum and minimum) � Pressure drop during normal flowing conditions � Pressure drop at shutoff � Maximum permissible noise level, if pertinent, and the measurement reference point � Degrees of superheat or existence of flashing, if known Chapter 5. Control Valve Selection 76 � Inlet and outlet pipeline size and schedule � Special tagging information required � Body Material (ASTM A216 grade WCC, ASTM A217 grade WC9, ASTM A351 CF8M, etc.) � End connections and valve rating (screwed, Class 600 RF flanged, Class 1500 RTJ flanges, etc.) � Action desired on air failure (valve to open, close, or retain last controlled position) � Instrument air supply available � Instrument signal (3 to 15 psig, 4 to 20 mA, Hart, etc.) In addition the following information will require the agreement of the user and the manufacturer depending on the purchasing and engineering practices being followed. � Valve type number � Valve size � Valve body construction (angle, double-port, butterfly, etc.) � Valve plug guiding (cage-style, port-guided, etc.) � Valve plug action (push-down-to-close or push-down-toopen) � Port size (full or restricted) � Valve trim materials required � Flow action (flow tends to open valve or flow tends to close valve) � Actuator size required � Bonnet style (plain, extension, bellows seal, etc.) � Packing material (PTFE V-ring, laminated graphite, environmental sealing systems, etc.) � Accessories required (positioner, handwheel, etc.) Some of these options have been discussed in previous chapters of this book, and others will be explored in this and following chapters. VALVE SELECTION PROCESS DETERMINE SERVICE CONDITIONS � (P1, ΔP, Q, T1, Fluid Properties, Allowable Noise, etc). � Select appropriate ANSI Pressure Class required for valve body and trim. CALCULATE PRELIMINARY Cv REQUIRED � Check noise and cavitation levels SELECT TRIM TYPE � If no noise or cavitation indication, choose standard trim. � If aerodynamic noise is high, choose Whisper Trim�. � If liquid noise is high and/or cavitation is indicated, choose Cavitrol� III trim. SELECT VALVE BODY AND TRIM SIZE � Select valve body and trim size with required Cv. � Note travel, trim group, and shutoff options. SELECT TRIM MATERIALS Select trim materials for your application; make sure trim selected is available in the trim group for the valve size selected. OPTIONS Consider options on shutoff, stem packing, etc. Valve Body Materials Body material selection is usually based on the pressure, temperature, Chapter 5. Control Valve Selection 77 corrosive properties, and erosive properties of the flow media. Sometimes a compromise must be reached in selecting a material. For instance, a material with good erosion resistance may not be satisfactory because of poor corrosion resistance when handling a particular fluid. Some service conditions require use of exotic alloys and metals to withstand particular corrosive properties of the flowing fluid. These materials are much more expensive than common metals, so economy may also be a factor in material selection. Fortunately, the majority of control valve applications handle relatively non-corrosive fluids at reasonable pressures and temperatures. Therefore, cast carbon steel is the most commonly used valve body material and can provide satisfactory service at much lower cost than the exotic alloy materials. Specifications have been developed for ordering highly corrosion resistant, high nickel alloy castings. These specifications represent solutions to problems encountered with those alloys. These problems included unacceptable corrosion resistance compared to the wrought materials, poor weldability, poor casting integrity Designations for the High Nickel Alloys Casting Designations Equivalent Wrought Tradenames Generic Designations UNS Numbers for Wrought Equivalents CF3 304L S30403 CF8 304 S30400 CF3M 316L S31603 CF8M 316 S31600 CG8M 317 S31700 CK3MCuN Avesta 254 SMO(1) Alloy 254 S31254 CN7M Carpenter 20Cb3(2) Alloy 20 N08020 CU5MCuC Incoloy 825(3) Alloy 825 N08825 CW12MW Obsolete Hastelloy C(4) Alloy C N10002 CW2M New Hastelloy C(4) Alloy C276 N10276 CX2MW Hastelloy C22(4) Alloy C22 N06022 CW6MC Inconel 625(3) Alloy 625 N06625 CY40 Inconel 600(3) Alloy 600 N06600 CZ100 Nickel 200 Alloy 200 N02200 LCB LCB J03003 LCC LCC J02505 M25S S-Monel(3) Alloy S M35-1 Monel 400(3) Alloy 400 N04400 N12MV Obsolete Hastelloy B(4) Alloy B N10001 N7M Hastelloy B2(4) Alloy B2 N10665 WCB WCB J03002 WCC WCC J02503 1. Trademark of Avesta AB 2. Tradenames of Carpenter Technology 3. Tradenames of Special Metals Corp. 4. Tradename of Haynes International Chapter 5. Control Valve Selection 78 and unacceptable lead times. The specifications include foundry qualification, dedicated pattern equipment, pattern alloy qualification, heat qualification, and detailed controls on raw material, visual inspection, weld repairs, heat treatment, and non-destructive testing. A listing of these exotic alloys appears in the Designations for the High Nickel Alloys Table. The following descriptions and tables provide basic information on various popular castable materials used for control valve bodies. ASTM material designations are included. Use of proper ASTM designations is considered good practice and is encouraged in specifying materials, particularly for pressure-containing parts. Additional engineering data on these and other materials is included in Chapter 10. Cast Carbon Steel (ASTM A216 Grade WCC)—WCC is the most popular steel material used for valve bodies in moderate services such as air, saturated or superheated steam, non-corrosive liquids and gases. WCC is not used above 800�F (427�C) as the carbon rich phase might be converted to graphite. It can be welded without heat treatment unless nominal thickness exceeds 1-1/4 inches (32 mm). Pressure-Temperature Ratings for Standard Class ASTM A216 Grade WCC Valves (in accordance with ASME B16.34) TEMPERATURE, �F WORKING PRESSURES BY CLASS, PSIG 150 300 600 900 1500 Psig −20 to 100 290 750 1,500 2,250 3,750 200 260 750 1,500 2,250 3,750 300 230 730 1,455 2,185 3,640 400 200 705 1,410 2,115 3,530 500 170 665 1,330 1,995 3,325 600 140 605 1,210 1,815 3,025 650 125 590 1,175 1,765 2,940 700 110 570 1,135 1,705 2,840 750 95 505 1,010 1,510 2,520 800 80 410 825 1,235 2,060 �C Bar −29 to 38 20 52 103 155 259 93 18 52 103 155 259 149 16 50 100 151 251 204 14 49 97 146 243 260 12 46 92 138 229 316 10 42 83 125 209 343 9 41 81 122 203 371 8 39 78 118 196 399 7 35 70 104 174 427 6 28 57 85 142 Chapter 5. Control Valve Selection 79 Cast Chromium-Molybdenum Steel (ASTM A217 Grade WC9)—This is the standard Cr-Mo grade. WC9 has replaced C5 as the standard because of superior casting and welding properties. WC9 has successfully replaced C5 in most applications, especially in steam and boiler feedwater service. The chromium and molybdenum provide erosion-corrosion and creep resistance, making it useful to 1100�F (593�C). WC9 requires preheating before welding and heat treatment after welding. Pressure-Temperature Ratings for Standard Class ASTM A217 Grade WC9 Valves (in accordance with ASME B16.34) TEMPERATURE, �F WORKING PRESSURES BY CLASS, PSIG 150 300 600 900 1500 −20 to 100 290 750 1,500 2,250 3,750 200 260 750 1,500 2,250 3,750 300 230 730 1,455 2,185 3,640 400 200 705 1,410 2,115 3,530 500 170 665 1,330 1,995 3,325 600 140 605 1,210 1,815 3,025 650 125 590 1,175 1,765 2,940 700 110 570 1,135 1,705 2,840 750 95 530 1,065 1,595 2,660 800 80 510 1,015 1,525 2,540 850 65 485 975 1,460 2,435 900 50 450 900 1,350 2,245 950 35 375 755 1,130 1,885 1000 20 260 520 780 1,305 1050 20(1) 175 350 525 875 1100 20(1) 110 220 330 550 �C Bar −29 to 38 20 52 103 155 259 93 18 52 103 155 259 149 16 50 100 151 251 204 14 49 97 146 243 260 12 46 92 138 229 316 10 42 83 125 209 343 9 41 81 122 203 371 8 39 78 118 196 399 7 37 73 110 183 427 6 35 70 105 175 454 4 33 67 101 168 482 3 31 62 93 155 510 2 26 52 78 130 538 1 18 36 54 90 565 1(1) 12 24 36 60 593 1(1) 8 15 23 38 1. For welding end valves only. Flanged end ratings terminate at 1000�F. Chapter 5. Control Valve Selection 80 Cast Chromium-Molybdenum Steel (ASTM A217 Grade C5)—In the past C5 was commonly specified for applications requiring chromium-molybdenum steels. However, this material is somewhat difficult to cast and has a tendency to crack when welded. WC9 has successfully replaced C5 in many applications, but C5 continues to be used in refinery applications where its higher chromium content provides better resistance to high-temperature sulfidic corrosion. Pressure-Temperature Ratings for Standard Class ASTM A217 Grade C5 Valves (in accordance with ASME B16.34) TEMPERATURE, �F WORKING PRESSURE BY CLASS, PSIG 150 300 600 900 1500 −20 to 100 290 750 1,500 2,250 3,750 200 260 745 1,490 2,235 3,725 300 230 715 1,430 2,150 3,580 400 200 705 1,410 2,115 3,530 500 170 665 1,330 1,995 3,325 600 140 605 1,210 1,815 3,025 650 125 590 1,175 1,765 2,940 700 110 570 1,135 1,705 2,840 750 95 530 1,055 1,585 2,640 800 80 510 1,015 1,525 2,540 850 65 485 965 1,450 2,415 900 50 370 740 1,110 1,850 950 35 275 550 825 1,370 1000 20 200 400 595 995 1050 20(1) 145 290 430 720 1100 20(1) 100 200 300 495 �C Bar −29 to 38 20 52 103 155 259 93 18 51 103 154 257 149 16 49 99 148 247 204 14 49 97 146 243 260 12 46 92 138 229 316 10 42 83 125 209 343 9 41 81 122 203 371 8 39 78 118 196 399 7 37 73 109 182 427 6 35 70 105 175 454 4 31 67 100 167 482 3 26 51 77 128 510 2 19 38 57 94 538 1 14 28 41 89 565 1(1) 10 20 30 50 593 1(1) 7 14 21 34 1. For welding end valves only. Flanged end ratings terminate at 1000�F. Chapter 5. Control Valve Selection 81 Cast Type 304L Stainless Steel (ASTM A351 Grade CF3)—This is a good material offering for chemical service valves. 304L is the best material for nitric acid and certain other chemical service applications. Optimum corrosion resistance is retained even in the as-welded condition. Pressure-Temperature Ratings for Standard Class ASTM A351 Grade CF3 Valves (in accordance with ASME B16.34) TEMPERATURE WORKING PRESSURES BY CLASS 150 300 600 900 1500 �F Psig −20 to 100 275 720 1,440 2,160 3,600 200 230 600 1,200 1,800 3,000 300 205 540 1,080 1,620 2,700 400 190 495 995 1,490 2,485 500 170 465 930 1,395 2,330 600 140 435 875 1,310 2,185 650 125 430 860 1,290 2,150 700 110 425 850 1,275 2,125 750 95 415 830 1,245 2,075 800 80 405 805 1,210 2,015 850 65 395 790 1,190 1,980 900 50 390 780 1,165 1,945 950 35 380 765 1,145 1,910 1000 20 320 640 965 1,605 1050 20(1) 310 615 925 1,545 1100 20(1) 255 515 770 1,285 1150 20(1) 200 400 595 995 1200 20(1) 155 310 465 770 1250 20(1) 115 225 340 565 1300 20(1) 85 170 255 430 1350 20(1) 60 125 185 310 1400 20(1) 50 95 145 240 1450 15(1) 35 70 105 170 1500 10(1) 25 55 80 135 �C Bar −29 to 38 19 50 99 149 248 93 16 41 83 124 207 149 14 37 74 112 186 204 13 34 69 103 171 260 12 32 64 96 161 316 10 30 60 90 151 343 9 30 59 89 148 371 8 29 59 88 147 399 7 29 57 86 143 427 6 28 56 83 139 (continued) Chapter 5. Control Valve Selection 82 Pressure-Temperature Ratings for Standard Class ASTM A351 Grade CF3 Valves (in accordance with ASME B16.34) (continued) TEMPERATURE WORKING PRESSURES BY CLASS 150 300 600 900 1500 �C Bar 454 4 27 54 82 137 482 3 27 54 80 134 510 2 26 53 79 132 538 1 22 44 67 111 565 1(1) 21 42 64 107 593 1(1) 18 36 53 89 621 1(1) 14 28 41 69 649 1(1) 11 21 32 53 676 1(1) 8 16 23 39 704 1(1) 6 12 18 30 732 1(1) 4 9 13 21 760 1(1) 3 7 10 17 788 1(1) 2 5 70 12 815 1(1) 2 4 6 9 1. For welding end valves only. Flanged end ratings terminate at 1000�F. Cast Type 316 Stainless Steel (ASTM A351 Grade CF8M)—This is the industry standard stainless steel body material. The addition of molybdenum gives Type 316 greater resistance to corrosion, pitting, creep and oxidizing fluids compared to 304. It has the widest temperature range of any standard material: −425�F (−254�C) to 1500�F (816�C). The rough castings are heat treated to provide maximum corrosion resistance. Cast Type 317 Stainless Steel (ASTM A479 Grade UNS S31700)—S31700 is essentially S31600 with the nickel and molybdenum contents increased 1% each. This affords greater resistance to pitting than is obtained with S31600. Like S31600, S31700 is completely austenitic and non-magnetic. Because its strength is similar to that of S31600, it has the same pressure-temperature allowances. CG8M is the casting version of S31700. It contains considerable amounts of ferrite (15 to 35%), and therefore is partially to strongly magnetic. In general, Type S31700 has better corrosion resistance than S31600 in certain environments because of its higher molybdenum content. It has excellent resistance to digester liquor, dry chlorine dioxide and many other pulp and paper environments. Pressure-Temperature Ratings for Standard Class ASTM A351 Grades CF8M and CG8M(1) Valves (in accordance with ASME B16.34) TEMPERATURE WORKING PRESSURES BY CLASS 150 300 600 900 1500 �F Psig −20 to 100 275 720 1,440 2,160 3,600 (continued) Chapter 5. Control Valve Selection 83 Pressure-Temperature Ratings for Standard Class ASTM A351 Grades CF8M and CG8M(1) Valves (in accordance with ASME B16.34) (continued) TEMPERATURE WORKING PRESSURES BY CLASS 150 300 600 900 1500 �F Psig 200 235 620 1,240 1,860 3,095 300 215 560 1,120 1,680 2,795 400 195 515 1,025 1,540 2,570 500 170 480 955 1,435 2,390 600 140 450 900 1,355 2,255 650 125 445 890 1,330 2,220 700 110 430 870 1,305 2,170 750 95 425 855 1,280 2,135 800 80 420 845 1,265 2,110 850 65 420 835 1,255 2,090 900 50 415 830 1,245 2,075 950 35 385 775 1,160 1,930 1000 20 350 700 1,050 1,750 1050 20(2) 345 685 1,030 1,720 1100 20(2) 305 610 915 1,525 1150 20(2) 235 475 710 1,185 1200 20(2) 185 370 555 925 1250 20(2) 145 295 440 735 1300 20(2) 115 235 350 585 1350 20(2) 95 190 290 480 1400 20(2) 75 150 225 380 1450 20(2) 60 115 175 290 1500 20(2) 40 85 125 205 �C Bar −29 to 38 19 50 99 149 248 93 16 43 85 128 213 149 15 39 77 116 193 204 13 36 71 106 177 260 12 33 66 99 165 316 10 31 62 93 155 343 9 31 61 92 153 371 8 29 60 90 150 399 7 29 59 88 147 427 6 29 58 87 145 454 4 29 58 87 144 482 3 27 57 86 143 510 2 24 53 80 133 538 1 24 48 72 121 565 1(2) 21 47 71 119 (continued) Chapter 5. Control Valve Selection 84 Pressure-Temperature Ratings for Standard Class ASTM A351 Grades CF8M and CG8M(1) Valves (in accordance with ASME B16.34) (continued) TEMPERATURE WORKING PRESSURES BY CLASS 150 300 600 900 1500 �C Bar 593 1(2) 16 42 63 105 621 1(2) 13 33 49 82 649 1(2) 10 26 38 64 676 1(2) 8 20 30 51 704 1(2) 6 16 24 40 732 1(2) 4 13 20 33 760 1(2) 3 10 16 26 788 1(2) 2 8 12 20 815 1(2) 2 6 9 14 1. CG8M is limited to 1000�F (538�C) 2. For welding end valves only. Flanged end ratings terminate at 1000�F (538�C). Cast Iron (ASTM A126)—Cast iron is an inexpensive, non-ductile material used for valve bodies controlling steam, water, gas and non-corrosive fluids. Pressure-Temperature Ratings for ASTM A216 Cast Iron Valves (in accordance with ASME/ANSI B16.1) TEMPERATURE CLASS 125 CLASS 250 ASTM A 216 ASTM A 216 Class A Class B Class A Class B NPS 1-12 NPS 1-12 NPS 14-24 NPS 1-12 NPS 1-12 NPS 14-24 �F Psig −20 to 150 175 200 150 400 500 300 200 165 190 135 370 460 280 225 155 180 130 355 440 270 250 150 175 125 340 415 260 275 145 170 120 325 395 250 300 140 165 110 310 375 240 325 130 155 105 295 355 230 353 125 150 100 280 335 220 375 - - - 145 - - - 265 315 210 406 - - - 140 - - - 250 290 200 425 - - - 130 - - - - - - 270 - - - 450 - - - 125 - - - - - - 250 - - - �C Bar −29 to 66 12 14 10 28 34 21 93 11 13 9 26 32 19 107 11 12 9 24 30 19 121 10 12 9 23 29 18 (continued) Chapter 5. Control Valve Selection 85 Pressure-Temperature Ratings for ASTM A216 Cast Iron Valves (in accordance with ASME/ANSI B16.1) (continued) CLASS 125 CLASS 250 ASTM A 216 ASTM A 216 TEMPERATURE Class A Class B Class A Class B NPS 14-24 NPS 1-12 NPS 1-12 NPS 14-24 NPS 1-12 NPS 1-12 �C Bar 135 10 12 8 22 27 17 149 10 11 8 21 26 17 163 9 11 7 20 24 16 178 9 10 7 19 23 15 191 - - - 10 - - - 18 22 14 207 - - - 10 - - - 17 20 14 218 - - - 9 - - - - - - 19 - - - 232 - - - 9 - - - - - - 17 - - - Pressure-Temperature Ratings for ASTM B61 and B62 Cast Bronze Valves (in accordance with ASME B16.24) SERVICE TEMPERATURE WORKING PRESSURE Class 150 Class 300 ASTM B 62 C83600 ASTM B 61 C92200 ASTM B 62 C83600 ASTM B 61 C92200 �F �C psig bar psig bar psig bar psig bar −20 to 150 -29 to 66 225 16 225 16 500 34 500 34 175 79