control_valve_sizing.pdf

7/28/2019 Control_Valve_Sizing.pdf

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Control Valve Sizing

General GuidelinesMost control valves used for HVAC control fall into one of four categories:

1. Two position valves (water or steam)2. Proportional control of water varying the amount of flow (chilled and hot water coils,

differential pressure control)

3. Proportional control of water varying the temperature of the flow (boiler hot water bypassand condenser water bypass)

4. Proportional control of steam

Usually, the pipe size will be smaller than the valve size. In this case, the pipe must be fitted down to thevalve. This reduction affects the flow characteristics of the valve and reduces the effective Cv of thevalve. This effect is known as the PIPING GEOMETRY FACTOR (symbol = Fp). Use the charts on thereverse side of this page to determine the actual Cv of a valve when it is installed in a larger pipe.

STEP 1 Determining The Correct Pressure Drop(P)1. TWO POSITION VALVES: WATER OR STEAM

A low-pressure drop across the valve is desirable.

P = 10% of the available pressure If pressure is not known, it is best to go with a

line size valve.

In this system, 20 PSI is the available

pressure. Valve should be sized to havea 2 PSI drop.

2. PROPORTIONAL CONTROL OF WATER:VARYING THE AMOUNT OF FLOW

A high-pressure drop across the valve is desirable.

Use a P = 4.3 for control valves for chilledand hot water coils.

A P = 4.3 may also be used for differentialpressure control applications.

In this system, 4.3 PSI should be used asthe pressure drop.

3. PROPORTIONAL CONTROL OF WATER:VARYING THE TEMPERATURE OF THE FLOW

A low-pressure drop across the valve is desirable.

P = 10% of the available pressureP = 25% of the P thru load @ full flow

In this system, the amount of water tothe coil doesnt change. The valvecontrols the percentage of the flowcoming from the boiler. By modulatingthe valve, the supply temperature isvaried.

4. PROPORTIONAL CONTROL OF STEAMA very high-pressure drop across the valve isdesirable.

For 15 PSI steam or less:- P = 80% of inlet gauge pressure

Under 15 PSIInlet pressure: 10 PSI

X (80%): .88 PSI

8 PSI is the desired pressure drop

- Choose valve which is at least 1 size smaller thanline size

For greater than 15 PSI steam:- P = 42% of absolute pressure

Over 15 PSIInlet pressure: 35 PSIAdjust to PSIA (Absolute): +14.7

49.7 PSI(Gauge pressure + 14.7 then multiply by 0.42)X 0.42Do not be alarmed by the seemingly high Ps that

are recommended for steam. Due to the nature ofsteam and its heating abilities, it requires a high-pressure drop for proper control.

20.87 PSI20.87 PSI is the desired pressure drop

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STEP 2 Calculating Cv

1. WATER SYSTEMS:Cv = GPM

P2. STEAM SYSTEMS:

Cv = LBS per HOUR

3 X (P X PO) Where PO = Inlet pressure (PI) - P

STEP 3 Valve Selection

Select the type of valve needed, i.e. ball, globe, or butterfly which most closely matches the required Cvcalculated in Step 2. Choose a valve that has a slightly larger Cv than the calculated Cv.

STEP 4 Correct For Piping Geometry Factor (Fp)

On the reverse side of this page, find the corrected Cv by referencing the pipe size and the valve size onthe PIPING GEOMETRY CORRECTION FACTOR CHART. Verify that the corrected Cv is not lessthan the calculated Cv. If the corrected Cv is less than the calculated Cv, choose the next larger sizevalve. The selected valve should never be smaller than the pipe size.

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Adjusted CV Ratings For Piping Geometry Factor (Fp)

2-Way Ball ValvesValve Valve Pipe Size

Size Model # 1/2" 3/4" 1" 1-1/4" 1-1/2" 2" 2-1/2" 3" 4" 5" 6"

0.50 05-2-004 0.4 .39 .39 .39 --- --- --- --- --- --- ---

0.50 05-2-01 1.00 .99 .99 .99 --- --- --- --- --- --- ---

0.50 05-2-02 2.00 1.96 1.94 1.92 --- --- --- --- --- --- ---

0.50 05-2-04 4.00 3.75 3.58 3.50 --- --- --- --- --- --- ---

0.50 05-2-10 9.80 7.38 6.30 5.86 --- --- --- --- --- --- ---

0.75 75-2-25 --- 25.00 19.53 16.26 14.75 --- --- --- --- --- ---

1.00 1-2-35 --- --- 35.00 31.08 27.35 23.80 --- --- --- --- ---

1.25 125-2-47 --- --- --- 47.00 43.97 37.55 34.48 --- --- --- ---

1.50 150-2-81 --- --- --- --- 81.00 68.01 58.84 54.25 --- --- ---

2.00 2-2-105 --- --- --- --- --- 105.00 97.89 90.30 81.66 --- ---

3.00 3-2-390 --- --- --- --- --- --- --- 390.00 307.76 257.40 233.89

0.75 75-2-33 --- 33.00 22.71 17.96 15.98 --- --- --- --- --- ---

1.00 1-2-47 --- --- 47.00 38.60 32.06 26.71 --- --- --- --- ---

1.25 125-2-81 --- --- --- 81.00 67.90 49.46 43.00 --- --- --- ---

1.50 150-2-105 --- --- --- --- 105.00 80.47 66.15 59.97 --- --- ---

2.00 2-2-210 --- --- --- --- --- 210.00 165.90 134.61 110.48 --- ---

2.50 250-2-440 --- --- --- --- --- --- 440.00 329.00 217.00 184.31 ---

Example: What is the correct Cv rating of a 75-2-25 valve when placed in a 1" pipe?

Look at 1" column and cross over to the valve model #. As one can see, the correct Cv rating is 19.53.These values also apply to stainless steel ball and stem (SSBS) and stainless steel bodied valves (SS) where applicable.

2-Way Flanged Ball ValveValve Valve Pipe Size

Size Model # 3" 4" 5" 6" 8" 10" 12"

3.00 3-2-600 600.00 384.6 297.47 262.77 --- --- ---

4.00 4-2-1200 --- 1200.00 803.00 605.63 476.85 --- ---

6.00 6-2-3300 --- --- --- 3300.00 1713.11 1265.42 1102.07

3-Way Ball ValvesValve Valve Pipe Size

Size Model # 1/2" 3/4" 1" 1-1/4" 1-1/2" 2" 2-1/2" 3" 4" 5" 6"

0.50 05-3-02 2.00 1.96 1.94 1.92 --- --- --- --- --- --- ---

0.50 05-3-06 6.00 5.25 4.82 4.62 --- --- --- --- --- --- ---

0.75 75-3-12 --- 12.00 11.20 10.46 10.02 --- --- --- --- --- ---

1.00 1-3-14 --- --- 14.00 13.70 13.33 12.85 --- --- --- --- ---

1.25 125-3-21 --- --- --- 21.00 20.70 19.90 19.40 --- --- --- ---

1.50 150-3-30 --- --- --- --- 30.00 29.17 28.31 27.75 --- --- ---

2.00 2-3-50 --- --- --- --- --- 50.00 49.16 48.08 46.66 --- ---

2.00 2-3-91 --- --- --- --- --- 91.00 86.25 80.77 74.53 --- ---

3-Way Flanged Ball ValveValve Valve Pipe Size

Size Model # 3" 4" 5" 6" 8" 10" 12"

3.00 3-3-135 135.00 130.00 125.59 122.56 --- --- ---

4.00 4-3-230 --- 230.00 224.97 218.55 210.31 --- ---

6.00 6-3-330 --- --- --- 330.00 325.61 320.82 317.59

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Adjusted CV Ratings For Piping Geometry Factor (Fp)

2-Way Globe ValvesValve Valve Pipe Size

Size Model # 1/2" 3/4" 1" 1-1/4" 1-1/2" 2" 2-1/2" 3" 4" 5" 6"

0.50 DG05-2-03 2.5 2.43 2.38 2.36 --- --- --- --- --- --- ---

0.75 DG75-2-07 --- 6.3 6.17 6.04 5.95 --- --- --- --- --- ---

1.00 DG1-2-10 --- --- 10 9.89 9.74 9.55 --- --- --- --- ---

1.25 DG125-2-16 --- --- --- 16 15.86 15.49 15.25 --- --- --- ---

1.50 DG150-2-25 --- --- --- --- 25 24.51 23.99 23.65 --- --- ---

2.00 DG2-2-40 --- --- --- --- --- 40 39.57 38.99 38.22 --- ---

2.50 DG250-2-63 --- --- --- --- --- --- 63 62.50 61.08 59.6 ---

3.00 DG3-2-100 --- --- --- --- --- --- --- 100 98.06 94.62 ---

4.00 DG4-2-160 --- --- --- --- --- --- --- --- 160 155.99 ---

5.00 DG5-2-250 --- --- --- --- --- --- --- --- --- 248.06 242.52

6.00 DG6-2-400 --- --- --- --- --- --- --- --- --- 400 371.35

3-Way Mixing ValvesValve Valve Pipe Size

Size Model # 1/2" 3/4" 1" 1-1/4" 1-1/2" 2" 2-1/2" 3" 4" 5" 6" 8" 10"

0.50 DG05-3-03 2.5 2.43 2.38 2.36 --- --- --- --- --- --- --- --- ---

0.75 DG75-3-07 --- 6.3 6.17 6.04 5.95 --- --- --- --- --- --- --- ---

1.00 DG1-3-10 --- --- 10 9.89 9.74 9.55 --- --- --- --- --- --- ---

1.25 DG125-3-16 --- --- --- 16 15.86 15.49 15.25 --- --- --- --- --- ---

1.50 DG150-3-25 --- --- --- --- 25 24.51 23.99 23.65 --- --- --- --- ---

2.00 DG2-3-40 --- --- --- --- --- 40 39.57 38.99 38.22 --- --- --- ---

2.50 DG250-3-63 --- --- --- --- --- --- 63 62.50 61.08 60.16 59.6 --- ---

3.00 DG3-3-100 --- --- --- --- --- --- --- 100 98.06 95.99 94.62 --- ---

4.00 DG4-3-160 --- --- --- --- --- --- --- --- 160 158.28 155.99 154.21 ---

5.00 DG5-3-250 --- --- --- --- --- --- --- --- --- 250 248.06 245.09 242.54

6.00 DG6-3-400 --- --- --- --- --- --- --- --- --- --- 400 380.77 371.37

3-Way Mixing ValvesValve Valve Pipe Size

Size Model # 1/2" 3/4" 1" 1-1/4" 1-1/2" 2" 2-1/2" 3" 4" 5" 6" 8"

0.50 DDG05-3-04 4 3.75 3.58 3.5 --- --- --- --- --- --- --- ---

0.75 DDG75-3-08 --- 8 7.75 7.49 7.32 --- --- --- --- --- --- ---

1.00 DDG1-3-15 --- --- 15 14.6 14.19 13.6 --- --- --- --- --- ---

1.25 DDG125-3-20 --- --- --- 20 19.74 19.04 18.06 --- --- --- --- ---

1.50 DDG150-3-28 --- --- --- --- 28 27.32 26.61 26.15 --- --- --- ---

2.00 DDG2-3-40 --- --- --- --- --- 40 39.57 38.99 32.22 --- --- ---

2.50 DDG250-3-68 --- --- --- --- --- --- 68 67.37 65.61 64.47 --- ---

3.00 DDG3-3-85 --- --- --- --- --- --- --- 85 83.80 82.49 81.62 ---

4.00 DDG4-3-160 --- --- --- --- --- --- --- --- 160 158.28 155.99 152.91

5.00 DDG5-3-195 --- --- --- --- --- --- --- --- --- 195 194 191.4

6.00 DDG6-3-250 --- --- --- --- --- --- --- --- --- --- 250 248.07

Example: What is the correct Cv rating of a 75-3-07 valve when placed in a 1" pipe?Look at 1" column and cross over to the valve model #. As one can see, the correct Cv rating is 6.17.These values also apply to stainless steel trim valves (SS).

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control_valve_sizing.pdf

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