Installed Gain as a Control Valve Sizing Criteria Jon Monsen, Ph.D., P.E.

Installed Gain as a Control Valve Sizing

Criteria

Jon Monsen, Ph.D., P.E.

Control Valve Characteristics

• Inherent• Installed

• Inherent• Installed

FL

OW

CA

PA

CIT

Y,

CV

VALVE TRAVEL

FL

OW

CA

PA

CIT

Y,

CV

VALVE TRAVEL

FLOW

METER

P2P1

P

What you need to remember about the inherent characteristic:

1. It is the relationship between valve opening

and flow capacity (CV) of

the valve while the pressure drop is held constant. (No system effects.)

2. It is the characteristic that is published by the manufacturer.

Inherent Characteristic

VALVE TRAVEL(PERCENT OF RATED TRAVEL)

40

10

20

50 1000 60 70

30

40

80 90

CV is linear with valve travel.

10 20 30

Linear

50

60

70

80

90

100

FL

OW

CP

AC

ITY

, C

V

What you need to remember about the linear characteristic:

1. Its graph is a straight line.

2. It is only used about 10% of the time.


Equal changes in Valve Position produce equal percentage changes in flow capacity.

What you need to remember about the equal percentage characteristic:

1. The shape of the graph

2. It is used about 90% of the time.


VALVE TRAVEL(PERCENT OF RATED TRAVEL)

FL

OW

CP

AC

ITY

, C

V

40

10

20

50 1000 60 70

30

40

80 9010 20 30

50

60

70

80

90

100

Equal Percentage (=%)

+10 = 50%

+22.5 = 50%

+15 = 50%

45

67.5

Installed Characteristic

0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

Pressure

source

50 psig

280’ 1.5” pipe

0 50

050 0 gpm

0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

FLOW (gpm) 10PIPE LOSS 1VALVE P 49

Pressure

source

50 psig

1 49

280’ 1.5” pipe049

10 gpm

CraneTechnical Paper 410

(1942) www.tp410.com


0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

Pressure

source

50 psig

3.5 46.5

280’ 1.5” pipe

FLOW (gpm) 10 20PIPE LOSS 1 3.5VALVE P 49 46.5

46.5 020 gpm





0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

Pressure

source

50 psig

7.5 42.5

42.5280’ 1.5” pipe

FLOW (gpm) 10 20 30PIPE LOSS 1 3.5 7.5VALVE P 49 46.5 42.5

030 gpm




0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

Pressure

source

50 psig

13 37

37280’ 1.5” pipe

FLOW (gpm) 10 20 30 40PIPE LOSS 1 3.5 7.5 13VALVE P 49 46.5 42.5 37

040 gpm




0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

Pressure

source

50 psig

20 30

30280’ 1.5” pipe

FLOW (gpm) 10 20 30 40 50PIPE LOSS 1 3.5 7.5 13 20VALVE P 49 46.5 42.5 37 30

050 gpm




0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

Pressure

source

50 psig

28 22

22280’ 1.5” pipe

FLOW (gpm) 10 20 30 40 50 60PIPE LOSS 1 3.5 7.5 13 20 28VALVE P 49 46.5 42.5 37 30 22

060 gpm



Installed CharacteristicF

LO

W

VALVE TRAVEL

=% V

ALVE

Pressure

source

50 psig

Rule of Thumb:

Lots of pipe, use Equal Percentage valve

Appr

ox. L

inea

r inst

alle

d

280’ 1.5” pipe

0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

VALVE TRAVEL0

10

20

30

40

50

0 10 20 30 40 50 60

FLOW

VA

LV

E P

Pressure

source

50 psig

2.8’ 1.5” pipe

Linea

r inher

ent

Lin

ear i

nstal

led

0.28 psi drop @ 60 gpm

Rule of Thumb:

Very little pipe, use Linear valve

49.72

Installed CharacteristicF

LO

W

Inst

alle

d G

ain

1.0

2.0

3.0

4.0

Valve Travel, h

Gain = Output / Input

Installed Characteristic and Gain


Flo

w,

q

Inst

alle

d G

ain

1.0

2.0

3.0

4.0


Gain = q / h



Valve Travel, h

Flo

w,

q

Inst

alle

d G

ain

1.0

2.0

3.0

4.0


Gain = q / h = SLOPE



Valve Travel, h

Flo

w,

q

Inst

alle

d G

ain

1.0

2.0

3.0

4.0




q = h X Gain


Valve Travel, h

Flo

w,

q

Inst

alle

d G

ain

1.0

2.0

3.0

4.0

1%

1/4%




q = h X Gain


Valve Travel, h

Flo

w,

q

Inst

alle

d G

ain

1.0

2.0

3.0

4.0

1%

1/4%

4%




q = h X Gain


Valve Travel, h

Flo

w,

q

Inst

alle

d G

ain

1.0

2.0

3.0

4.0


Gain = d q / d h = SLOPE



Valve Travel, h

Flo

w,

q

Within the specified control range:

1. Gain 0.5

2. Gain 3.0

3. Gain (max) / Gain (min) 2.0


Gain = q / h

q = h X Gain

Installed Gain Recommendations

Inst

alle

d G

ain 3.0

2.0

4.0

1.0

q min q maxFlow


1. Gain 0.5

2. Gain 3.0



Gain = q / h

q = h X Gain


Loop Tuned here

Data courtesy of ExperTune, Inc.

SP

PV

Large gain change:Can’t maintain good control with stability throughout flow range.The “un-tunable” loop!

Inst

alle

d G

ain 3.0

2.0

4.0

1.0

q min q maxFlow

Inst

alle

d G

ain 3.0

2.0

4.0

1.0

q min q max


1. Gain 0.5

2. Gain 3.0



Gain = q / h

q = h X Gain


Flow

Loop Tuned here

SP

PV

Data courtesy of ExperTune, Inc.

Small gain change:Good control with stability throughout flow range.

Inst

alle

d G

ain 3.0

2.0

4.0

1.0

q maxq min


1. Gain 0.5

2. Gain 3.0


4. As constant as possible

5. As close to 1.0 as possible


Flow


Gain = q / h

q = h X Gain

Inst

alle

d G

ain 3.0

2.0

4.0

1.0

q min q maxFlow

Cv

Valve Travel

Actual inherent flow characteristic Actual system characteristicFlow, gpm

Pre

ssu

re,

psi

g

3220

P1 = 42

P1 = 32

P2 = 10 P2 = 12

25

P1 = 36

P2 = 11

MinNorm

Max

0

10

20

30

40

50

0 100 200 300 400 500 600 700 800

Software Graphs Installed Characteristic & Gain

qf=766

6” Sch. 40

580’(Equiv. pipe & fittings)

230’

70F Water

10P2P1PP

FC

=% Inherent characteristic

Flowgpm

PP

psigPipeLoss(up)

P1

psigPipeLoss

(down)

P2

psig P

80 42 0.1 42 0.05 10 32

550 37 5.0 32 2.00 12 20

0

10

20

30

40

50

0 100 200 300 400 500 600 700 800

Flow, gpm

Pre

ssu

re,

psi

g

32 20

P1 = 42

P1 = 32

P2 = 10 P2 = 12

Sizing Example

Cv QGP

Sizing Example

85 dBA for 6”32.8 fpsp < pT

Sizing Example

80 dBA for 3”32.8 fps

Sizing Example

p < pT

6” 3”

80

80

550

550

Sizing Example

6” 3”

80

80

550

550

6”

3”

80 550

q maxq min

Inst

alle

d G

ain

3

2

4

1

q min q max

Inst

alle

d G

ain

3

2

4

1


1. Gain 0.5

2. Gain 3.0




Sizing Example

4”

What is the optimum control valve pressure drop to design into a system to ensure adequate control while avoiding the use of excessive pumping power?

Selecting the Right Pump

TC

10

5 515

Pump head droops 5 psi from 100 gpm to 600 gpm

Pressure losses @600 gpm

6” Sch 40

70°F Water

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600

P210

45

535

P1 (Pump A) 17 hp*35 2050

P1 (Pump B) 23 hp*6050

30

* At normal flow (400 gpm)

P1 P2

3565

P1 (Pump C) 29 hp*7565


valve characteristic

Inhe

rrent

Inst

alle

d

Min. Norm. Max.

PRESSURE DROP = 5 psi @ MAX. FLOWPump power = 17 hp @ 400 gpm


Selecting the Right PumpPRESSURE DROP = 5 psi @ MAX. FLOW

Pump power = 17 hp @ 400 gpm

6”



3”



5 psi, 17 hp

20 psi, 23 hp

35 psi, 29 hp

q maxq min

Inst

alle

d G

ain

3

2

4

1

q min q max

Inst

alle

d G

ain

3

2

4

1


1. Gain 0.5

2. Gain 3.0




3”

6”


20 psi, 23 hp

35 psi, 29 hp

3”

Maximum Calculated SPLTo avoid cavitation damage

UP TO 3” 80dBA4” TO 6” 85 dBA8” TO 14” 90 dBA16” AND UP 95 dBA


Thank you!

[email protected]

Installed Gain as a Control Valve Sizing Criteria Jon Monsen, Ph.D., P.E.

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Transcript of Installed Gain as a Control Valve Sizing Criteria Jon Monsen, Ph.D., P.E.