Control Valves - HVAC Excellence

Report
Control Valves:
Specifications, Sizing & Technologies
Control Valves:
Specifications, Sizing & Technologies
David Kandel
Application Consultant
Belimo
david.kandel@us.Belimo.com
720-354-0591
Agenda
Control Valves: Specification, Sizing and Technologies
•
•
•
•
•
Controlling a Coil
Ratings and Definitions
Hydronic Valve Sizing
Steam Valve Sizing
Control Valve Technology
© Belimo, 2012
Agenda
Control Valves: Specification, Sizing and Technologies
•
•
•
•
•
Controlling a Coil
Ratings and Definitions
Hydronic Valve Sizing
Steam Valve Sizing
Control Valve Technology
© Belimo, 2012
Understating Coil Behavior
Coil Performance
ΔT
Coil Power / Flow
Resulting Coil
Output
Valve GPM
BTUh
Flow / Control Signal
Agenda
Control Valves: Specification, Sizing and Technologies
•
•
•
•
•
Controlling a Coil
Ratings and Definitions
Hydronic Valve Sizing
Steam Valve Sizing
Control Valve Technology
© Belimo, 2012
Valve Specs
• Pressure/Temperature Ratings
•
•
•
•
•
Body Pressure
Close-Off Pressure
Close-Off Leakage
DP
Temp Ratings
• Valve Flow
• Characterization Curve
• Rangeability/Turndown
• Valve Authority
• Actuation
• Fail Safe
• Normally Open/Normally Closed
Body Pressure
Pressure Vessel Burst Rating
• Measured in psi
• Failure Threshold of the Vessel
Body Pressure
ANSI Body Rating
• Relationship between
Pressure and
Temperature
Close-Off Pressure
P1
The maximum pressure that a valve can withstand without leakage while in the
fully closed position.
Close-Off Pressure
Rule of Thumb
•
•
2-way Valve
• Close-off pressure should at least equal the maximum pressure produced
by the circulating pump
3-way Valve
• Close-off pressure should at least equal the system differential pressure
Close-Off Pressure
Close-Off Leakage
Bubble Tight is not an ANSI rating.
Bubble Tight implies No water leakage.
Pressure Drop
P1
P2
The maximum allowable pressure differential that a fully open
valve can withstand without damaging the internals of the valve.
Temperature Ratings
•
•
•
Media Temperature (hydronic)
• Acceptable fluid temperature range
Media Temperature (steam)
• Commonly measured in lbs of steam
Ambient Temperature
• Usually an actuator rating
Characterization Curves
Equal Percentage
Linear
Quick Opening
Modified Equal Percentage
Flow
•
•
•
•
• Varies
Modulating
2
Position
based
control
Control
on design
of Steam
a Coil
•Coil
CCV,
Zone
Butterfly
or Bypass
Valves
PI-Valves,
Valves,
Applications
Globe
others Valve
• ePIV, Globe Valves
Valve Position
Rangeability & Turndown
Rangeability:
The ratio of maximum flow to minimum controllable flow
of a valve body only under laboratory conditions with a
constant differential pressure applied across the valve.
Turndown Ratio:
The ratio of maximum usable flow to minimum
controllable flow of the valve assembly under installed
conditions. It is always lower than the rangeability
factor.
Agenda
Control Valves: Specification, Sizing and Technologies
•
•
•
•
•
Controlling a Coil
Ratings and Definitions
Hydronic Valve Sizing
Steam Valve Sizing
Control Valve Technology
© Belimo, 2012
Flow Coefficient
FLOW COEFFICIENT (Cv) is the quantity of water in gpm at
60 DegF that flows through an open valve with a pressure
drop of 1psi.
Cv 
gpm
P
Hydronic Valve Sizing
Cv 
gpm
Cv 
P
8
4

8
4
2
Example:
• Coil Requires 8 GPM
• Design DP for valve, 4 psi
• DP of Valve not to exceed 5
psi
Hydronic Valve Sizing
Cv 
8
4

8
4
2
Example:
• Coil Requires 8 GPM
• Design DP for valve, 4 psi
• DP of Valve not to exceed 5
psi
Hydronic Valve Sizing
Checking DP
 GPM 
P  

 Cv 
2
Example:
• Coil Requires 8 GPM
• Design DP for valve, 4 psi
• DP of Valve not to exceed 5
psi
Hydronic Valve Sizing
Checking DP
 GPM 
P  

 Cv 
2
2
8
 P     7 . 1 psi
3
2
 8 
P  
  2 . 9 psi
 4 .7 
Hydronic Valve Sizing
Checking DP
Which should we select?
And Why?
 GPM 
P  

 Cv 
2
2
8
 P     7 . 1 psi
3
2
 8 
P  
  2 . 9 psi
 4 .7 
Valve Authority
A
 p valve
 p branch
 p valve
Balance
Valve
Flow (%)
Coil
 pBranch
Valve Opening (%)
24
Valve Authority
2
8
 P     7 . 1 psi
3
A
 p valve
 p branch
2
 8 
P  
  2 . 9 psi
 4 .7 
 p valve
Balance
Valve
Coil
A
A
 p valve ( 7 . 1 psi )
 p branch ( 4  7 . 1  2 psi )
 p valve ( 2 . 9 psi )
 p branch ( 4  2 . 9  6 . 2 psi )
 0 . 54
 0 . 22
 pBranch
Valve Authority
Valve Authority Distortion
Flow (%)
Flow / Coil Output (%)
100
90
80
70
60
50
0.2
40
30
1
20
10
0
Valve Opening (%)
10
20
30
40 50
60
70
80 90 100
Valve Opening (%)
26
Hydronic Valve Sizing
Rules of Thumb
Differential Pressure Across the Valve
• Should be greater than coil DP
• Valve Authority > 0.4
• Typically between 3psi - 5psi for modulating
• Typically about 1 psi for on/off
Pipe Reduction Factor
½" valve in a ½" pipe with a Cv tested at 10
Same ½" valve in a 1" pipe will test at Cv = 6.3
Pipe Reduction Factor
Fp 
1

1





   d 2  
1.5 1 -  2    
2
   D      C v 
 2 
890
 d 


Fp  pipe geometry
C v  rated sizing
d  nominal
factor
coefficien
t without
valve size (in.)
D  inside diamter
C vc  corrected
C vc  Fp  C v
Cv
of the pipe (in.)
reducers
Pipe Reduction Factor
Only for Valves with High Cv relative to line size
Pipe Reduction Factor
Rules of Thumb
Choosing Valves Smaller than Line size
• The control valve shall be no less than ½ the pipe
size…
• However, it’s best to keep the valve size reduction
no greater than 2 pipe sizes.
• Large pipe reductions can increase the
effects of cavitation
Piping Considerations
•
Which is Correct?
And
•
Why is it Correct?
Template
day month year
32
Agenda
Control Valves: Specification, Sizing and Technologies
•
•
•
•
•
Controlling a Coil
Ratings and Definitions
Hydronic Valve Sizing
Steam Valve Sizing
Control Valve Technology
© Belimo, 2012
Steam Valve Sizing
Low Pressure Steam (under 15psi)
Cv = Flow Coefficient
Q
Cv 
3*
  P  Po 
Q = lbs per hour of steam
ΔP = Differential Pressure in psig
Po = Outlet Pressure in psia
(psia = psig + 14.7)
ΔP = 80% inlet gauge pressure (psig)
Steam Valve Sizing
Low Pressure Steam (under 15psi)
Q
Cv 
3*
 P  P 2 
P 2  5 - 4   14 . 7  15 . 7
 P  5  0.8   4
160
Cv 
3*
Example: Size a modulating
control valve for 160 lb/hr with
a 5 psig steam supply.
4  15 . 7

160
23 . 774
 6 . 73
Steam Valve Sizing
More than 15psi
Q
Cv 
3*
  P  Po 
Cv = Flow Coefficient
Q = lbs per hour of steam
ΔP = Differential Pressure in psia
Po = Outlet Pressure in psia
(psia = psig + 14.7)
ΔP =
42% absolute inlet pressure (psia)
Steam Valve Sizing
More than 15psi
Q
Cv 
3*
  P  Po 
 P  30  14.7   0 . 42  18 . 8
Po  30  14.7   18 . 8  25 . 9
Example: Size modulating
1/3-2/3 valves for a heat
exchanger with a design
flow of 600 lb/hr at 30
psig.
Steam Valve Sizing
More than 15psi
1/3rd:
2/3rd:
Cv 
Cv 
Example: Size modulating
1/3-2/3 valves for a heat
exchanger with a design
flow of 600 lb/hr at 30
psig.
200
3 * 18 . 8  25 . 9
400
3 * 18 . 8  25 . 9

200
 3 . 02
66 . 2

400
66 . 2
 6 . 04
1/3-2/3 Valve Sequencing
Open
Closed
0%
25%
50%
Control Signal
2/3 valve
1/3 valve
75%
100%
Agenda
Control Valves: Specification, Sizing and Technologies
•
•
•
•
•
Controlling a Coil
Ratings and Definitions
Hydronic Valve Sizing
Steam Valve Sizing
Control Valve Technology
© Belimo, 2012
Control Valve Technologies
CCV
Characterized Control Valves
•
•
Ball Valve (rotary action)
Characterizing Disc
CCV
CCV
2-way
CCV
3-way (Mixing or Diverting)
CCV
Valve Summary
• Pros
• Inexpensive
• Equal Percentage
Characteristic
• High Close Off
• Large Range of Cv
• Cons
• Hot and Chilled Water with
Glycol Only
• Applications
• Hot & chilled water coils
(for air handling units)
• Unit ventilators
• Fan coils
• VAV units
Globe Valves
Globe Valves
•
•
Linear Action
Plug Design
Globe Valves
Close-Off Pressure
•
•
Close-Off Rating Determined by Force
Applied to Stem
Close-Off is Actuator Dependent
Pd
Pu
Globe Valves
3-way Mixing
Globe Valves
3-way Mixing
Globe Valves
3-way Diverting
Globe Valves
3-way Diverting
Globe Valves
Valve Summary
• Pros
• Equal Percentage or
Linear Characteristic
• SS Trim works for Steam
• Cons
•
•
•
•
Expensive
Large
2 Versions of 3-way
Close off depends on
Actuator
• Applications
• Hot & chilled water coils
(for air handling units)
• Chillers
Globe Valves
What is a Pressure Compensated Globe Valve?
Pu
Pd
Pd
Pd
Pu
Holes in Plate
Balance the
Pressure
Pu
Globe Valves
Pressure Compensated Close-Off Pressures
Standard Globe Valve Close-Off Ratings
AFX24-MFT
G665
2½”
G665
2½”
G680
3”
G680
3”
2xAFX24-MFT
51 psi
82 psi
34 psi
56 psi
Pressure Compensated GV Close-Off Ratings
AFX24-MFT
2xAFX24-MFT
G665C
2½”
150 psi
G680C
3”
150 psi
G6100C
4”
150 psi
G6125C
5”
150 psi
G6150C
6”
105 psi
Butterfly Valves
Butterfly Valves
•
•
•
Rotary Action
Flow Characteristic:
• Modified Equal Percentage
Rotating Disc and Resilient Seat
Butterfly Valves
Butterfly Valves
3-Way Butterfly Valves
• 2 Valves linked on a Tee
• Mixing or Diverting
• 1 or 2 Actuators
Butterfly Valves
3-Way Butterfly Valves
• 2 Valves linked on a Tee
• Mixing or Diverting
• 1 or 2 Actuators
Butterfly Valves
Sizing a BFV: Velocity
•
•
12 ft/sec in Standard BFV
32 ft/sec in High Performance BFV
Butterfly Valves
Valve Summary
• Pros
•
•
•
•
Up to 30”
Inexpensive
High Close-Off
SS and HP Available
• Cons
• Modified Eq %
• High Cv Relative to Size
• Velocity Limitations
• Applications
• Chiller and Cooling Tower
Isolation
• Change Over Systems
• Large Air Handlers
• Bypass Controls
V-Ball (Segmented Ball Valve)
V-Ball Valves
• For Extreme Conditions
• 400F Water
• 250 PSI Steam
• 150 PSI Close-off
• Controls
• Equal Percent Flow Characteristic
• 300:1 Rangeability
V-Ball (Segmented Ball Valve)
V-Ball Valves
• Rotatory Valve
• Single seat
• Partial Ball reduced torque requirement
V-Ball (Segmented Ball Valve)
Valve Summary
• Pros
• For extreme applications
• High Temp Water
• High Pressure Steam
• High rangeability
• Cons
• Expensive
• Limited sizes and Cv
• Large (heavy)
• Applications
• Hot & chilled water coils
(for air handling units)
• Chillers
Zone Valves
Zone Valves
• Inexpensive
• 2 Position
• Spring Return
• “Paddle” Design
Zone Valves
2-Way
3-Way Diverting
Zone Valves
Valve Summary
• Pros
• Cheap
• Fail Safe
• Cons
• Cheap
• 2 Position Only
• Low Close-Off
• Applications
• Baseboards
• Low Flow needing 2
position, fail safe
Pressure Independent Valves
Pressure Independent Control Valves
2-way valve that supplies a specific flow for each value of the control signal –
– Regardless of pressure variations in the system
Pressure
Flow
PI Valve
Pressure Independent
Technologies
Mechanical Regulator
Electronic Flow Meter
Pressure Independent Valves
Valve Summary
• Pros
• Accurate Flow Regardless of
Pressure Conditions
• Increased Water-side DT
• Reduced Pump Energy
Usage
• Valve Authority = 1.0
• Eliminates need of
Automatic Balancing Valves
• Cons
• Higher Initial Cost
• Applications
• Hot & chilled water coils
(for air handling units)
• Unit ventilators
• Fan coils
• VAV units
Control Valves:
Specifications, Sizing & Technologies
Questions?

similar documents