Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

• the most efficient way to navigate the Engineering ToolBox!

# Steam Control Valves - Calculate Flow Factor Kv

The procedure below can be used for proper design of steam process control valves and their correct flow factors - Kv.

### 1. Determine Pressure Coefficient - Pcoef

Start with the absolute pressure before the control valve and the actual pressure drop available over the valve and determine the pressure coefficient - Pcoef - from the table below.

Pcoef = pressure drop / specific volume

Note! The pressure drop can not exceed critical pressure drop which is approximately 42% of the inlet pressure.

For full table - rotate the screen!

Steam Control Valves - Pressure Coefficient - Pcoef
Absolute Pressure
- Pin -
(bar)

Specific Volume
- v -
(m3/kg)

Pcoeff
Pressure drop (bar)
0.511.522.533.544.555.566.577.5
1 1.69 0.30
2 0.89 0.56 1.12
3 0.61 0.82 1.64 2.46
4 0.45 1.11 2.22 3.33 4.44
5 0.38 1.32 2.63 3.95 5.26 6.58
6 0.32 1.56 3.13 4.69 6.25 7.81 9.38
7 0.27 1.85 3.70 5.56 7.41 9.26 11.1 13.0
8 0.24 2.08 4.17 6.25 8.33 10.42 12.5 14.6 16.7
9 0.21 2.38 4.76 7.14 9.52 11.90 14.3 16.7 19.1 21.4
10 0.19 2.63 5.26 7.89 10.53 13.16 15.8 18.4 21.1 23.7 26.3
11 0.18 2.78 5.56 8.33 11.11 13.89 16.7 19.4 22.2 25.0 27.8 30.6
12 0.16 3.13 6.25 9.38 12.50 15.63 18.7 21.9 25.0 28.1 31.3 34.4 37.5
13 0.15 3.33 6.67 10.00 13.33 16.67 20.0 23.3 26.7 30.0 33.3 36.7 40.0 43.3
14 0.14 3.57 7.14 10.71 14.29 17.86 21.4 25.0 28.6 32.1 35.7 39.3 42.9 46.4 50.0
15 0.13 3.85 7.69 11.54 15.38 19.23 23.1 26.9 30.8 34.6 38.5 42.3 46.2 50.0 53.9 57.7

#### Example - Pressure Coefficient

In a steam system with 9 bar gauge pressure the absolute pressure is 10 bar. If a pressure drop of 3.5 bar is acceptable and suitable for the steam consumer, the pressure coefficient Pcoef should be 18.4.

### 2. Determine Flow Factor - Kv

Select the pressure coefficient - Pcoef - column closest possible to the actual pressure coefficient calculated in step 1.

Follow the column down until reaching the appropriate actual flow value. Interpolate between values if necessary.

Go left in the table to find the actual flow factor Kv.

Steam Control Valves - Flow Factor - Kv
KvSteam Flow (kg/h)
Pressure Coefficient - Pcoeff
11.251.561.952.443.053.814.775.967.45
0.01 0 0 0 0 0 1 1 1 1 1
0.02 0 1 1 1 1 1 1 1 1 1
0.02 1 1 1 1 1 1 1 2 2 2
0.03 1 1 1 1 2 2 2 2 3 3
0.05 2 2 2 2 3 3 3 4 4 4
0.08 2 3 3 3 4 4 5 5 6 7
0.11 4 4 5 5 6 6 7 8 9 10
0.17 5 6 7 8 8 9 11 12 13 15
0.26 8 9 10 11 13 14 16 18 20 22
0.38 12 14 15 17 19 21 24 27 30 33
0.58 18 20 23 26 29 32 36 40 45 50
0.86 27 31 34 38 43 48 54 60 67 75
1.3 41 46 51 57 64 72 80 90 100 112
2.0 62 69 77 86 96 108 120 135 151 168
2.9 93 103 116 129 145 162 181 202 226 253
4.4 139 155 174 194 217 242 271 303 339 379
6.6 208 233 260 291 325 364 407 455 508 568
9.9 312 349 390 436 488 546 610 682 763 853
14.8 468 524 586 655 732 818 915 1023 1144 1279
22.2 703 786 878 982 1098 1228 1373 1535 1716 1918
33.3 1054 1179 1318 1473 1647 1841 2059 2302 2574 2877
49.9 1581 1768 1976 2210 2471 2762 3088 3453 3860 4316
74.8 2372 2652 2965 3315 3706 4143 4632 5179 5790 6474
112 3558 3978 4447 4972 5559 6215 6948 7769 8686 9711
168 5336 5966 6671 7458 8338 9322 10423 11653 13028 14566
253 8005 8949 10006 11187 12507 13983 15634 17479 19543 21849
379 12007 13424 15009 16780 18761 20975 23451 26219 29314 32774
568 18010 20136 22513 25170 28141 31463 35177 39329 43971 49161
852 27016 30204 33769 37755 42212 47194 52765 58993 65956 73741
1278 40523 45307 50654 56633 63318 70791 79147 88489 98934 110612

For full table - rotate the screen!

Steam Control Valves - Flow Factor - Kv
KvSteam Flow (kg/h)
Pressure Coefficient - Pcoeff
9.3111.614.518.222.728.435.544.455.569.4
0.01 1 1 1 1 2 2 2 2 2 3
0.02 1 2 2 2 2 3 3 3 4 4
0.02 2 2 3 3 3 4 4 5 5 6
0.03 3 4 4 5 5 6 6 7 8 9
0.05 5 5 6 7 8 9 10 11 12 13
0.08 7 8 9 10 11 13 14 16 18 20
0.11 11 12 14 15 17 19 22 24 27 30
0.17 17 18 21 23 26 29 32 36 40 45
0.26 25 28 31 35 39 43 48 54 61 68
0.38 37 42 46 52 58 65 73 81 91 102
0.58 56 62 70 78 87 97 109 122 136 152
0.86 84 94 105 117 131 146 163 183 204 228
1.3 126 140 157 175 196 219 245 274 306 343
2.0 188 210 235 263 294 329 368 411 460 514
2.9 282 316 353 395 441 493 552 617 689 771
4.4 424 474 530 592 662 740 827 925 1034 1156
6.6 635 710 794 888 993 1110 1241 1388 1551 1734
9.9 953 1066 1191 1332 1489 1665 1862 2081 2327 2602
14.8 1430 1598 1787 1998 2234 2498 2792 3122 3491 3903
22.2 2145 2398 2681 2997 3351 3746 4189 4683 5236 5854
33.3 3217 3597 4021 4496 5026 5620 6283 7025 7854 8781
49.9 4825 5395 6032 6744 7540 8429 9424 10537 11781 13171
74.8 7238 8092 9047 10115 11309 12644 14137 15805 17671 19757
112 10857 12138 13571 15173 16964 18966 21205 23708 26506 29635
168 16285 18208 20357 22760 25446 28449 31808 35562 39759 44452
253 24428 27312 30535 34139 38169 42674 47711 53343 59639 66679
379 36642 40967 45803 51209 57254 64011 71567 80014 89459 100018
568 54963 61451 68704 76814 85880 96017 107350 120021 134188 150027
852 82445 92176 103056 115220 128820 144026 161025 180032 201282 225040
1278 123668 138265 154584 172831 193231 216038 241538 270048 301923 337560

#### Example - Determine Flow Factor

For a pressure coefficient Pcoef = 18.2 and steam flow = 592 kg/h -  the flow factor Kv is 4.4.

### The formula used for the flow factor - Kv

The tables above are based on the formula:

Kv = m / (31.7 (dP / v)1/2)                             (1)

where

m= steam flow (kg/h)

dP = pressure drop (bar)

v = specific volume of steam before control valve (m3/kg)

### Steam Control Valve - Kv Calculator

Steam Kv calculator based on eq. 1:

## Related Topics

### • Control Valves

Control Valve terminology, bodies, trim, flow characteristics, Cv and Kv sizing, noise, actuators and positioners

### • Control Valves and Equipment

Sizing and dimensions of control valves & equipment in steam and condensate systems.

### • Process Control

Instrumentation and process control systems - design and documentation.

### • Steam and Condensate

Steam & condensate systems- properties, capacities, pipe sizing, systems configuration and more.

## Related Documents

### Ball Valves - Flow Coefficients Cv

Flow coefficients - Cv - for typical ball valves - reduced and full bore.

### Control Valves - Adding Flow Coefficients for Valves in Series or Parallel

How to add flow coefficients for control valves in series or parallel.

### Control Valves - Cavitation

Control valves and cavitation, application ratio and multi stage control valves.

### Control Valves - Flow Characteristics

Flow capacities vs. stem opening.

### Control Valves - Leakage Classification

Seat leakage classification through control valves.

### Control Valves - Sizing and Selection

Sizing control valves to match process requirements.

### Gases - Control Valve Calculator

An online control valve - Cv - calculator for gases.

### Liquid, Steam and Gas - Flow Coefficients Cv

Calculate flow coefficients for the design of control valves - Imperial units.

### Steam & Condensate Equations

Steam consumption and condensate generation when heating liquid or gas flows

### Steam Control Valves - Sizing

Calculate control valves in steam systems.

### Valve Authority

The valve authority expresses the ratio between pressure drop across the control valve compared to total pressure drop across the whole system.

### Valve Selection Guide

Applications guide for selecting valves.

### Water Control Valves - Flow Coefficient Cv Diagram

Sizing of water control valves - Imperial units.

## Search Engineering ToolBox

• the most efficient way to navigate the Engineering ToolBox!

## SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!