1. Laboratory Airflow Control Devices I2SL Denver – August, 2017

2. Laboratory Airflow Control Devices
Agenda
Standards
Mechanical Operation
Flow and Pressure Ranges
Control Methods and Accuracies
Speed of Response
Maintenance
Airflow Sound
Material Options Coatings

3. Laboratory Airflow Control Devices
Standards

4. Laboratory Airflow Control Devices
Standards & Guidelines
Primary Standards
ANSI Z9.5 – 2012
ASHRAE 110 – 2016
ASHRAE Lab Design Guide, 2nd Ed
Related Standards
ASHRAE 90.1 – 2010
NEBB Fume Hood Performance Testing

5. Laboratory Airflow Control Devices
Mechanical Operation

6. Laboratory Airflow Control Devices
Mechanical Operation
Standard Accuracy Damper Control Valve
Direct airflow measurement using in-stream flow sensors that utilize velocity pressure
Typical 6:1 turndown ratios
Typically require three duct diameters of straight duct leading into and out of the valve

7. Laboratory Airflow Control Devices
Mechanical Operation
High Accuracy Damper Control Valve
Direct airflow measurement using velocity pressure, vortex shedding sensors, or thermal dispersion
Typical 10:1 turndown ratios
Typically require one duct diameters of straight duct leading into and out of the valve
Damper Blade
Hi and Low Pressure Ports
Airflow

8. Laboratory Airflow Control Devices
Mechanical Operation
Venturi Valves
Electronic flow feedback
Mechanical pressure independent control valves
Typical 16:1 turndown ratio
No straight inlet/outlet duct run requirements

9. Laboratory Airflow Control Devices
Control Valve Fundamentals
Mechanical Pressure Independence
Laboratory Airflow Control Devices
Mechanical Operation
Venturi Valve
Expanded spring – increased airflow area
Compressed spring – reduced airflow area
Airflow remains constant – Damper position constant

10. Flow and Pressure Ranges
Laboratory Airflow Control Devices
Flow and Pressure Ranges

11. Laboratory Airflow Control Devices
Presentation Title
Version 00/00/00
Laboratory Airflow Control Devices
Operational Range
Valve Size
Standard Accuracy Damper Control Valves
Units
Min. Flow
Max. Flow
Turndown Ratio
Size 8
CFM
160
800
5:1
Size 10
225
1350
6:1
Size 12
350
2100
Size 14
500
3000
Operation Pressure
in. w.c.
>0.01
0.01
Copyright© 2012, All Rights Reserved - Price Industries

12. Laboratory Airflow Control Devices
Presentation Title
Version 00/00/00
Laboratory Airflow Control Devices
Operational Range
Valve Size
High Accuracy Damper Control Valves
Units
Min. Flow
Max. Flow
Turndown Ratio
Size 8
CFM 80
800
10:1
Size 10
120
1300
Size 12
180
1800
Size 14
250
2500
Operation Pressure
in. w.c.
>0.01
0.15
Copyright© 2012, All Rights Reserved - Price Industries

13. Laboratory Airflow Control Devices
Presentation Title
Version 00/00/00
Laboratory Airflow Control Devices
Operational Range
Valve Size
Units
Low Pressure Venturi Valve
Medium Pressure Venturi Valve
Min. Flow
Max. Flow
Turndown Ratio
Size 8
CFM 35
500
14:1
700
20:1
Size 10 50
550
11:1
1000
Size 12 90
1200
13:1
1500
16:1
Size 14
200
1400
7:1
2500
12:1
Operation Pressure
in. w.c.
Copyright© 2012, All Rights Reserved - Price Industries

14. Laboratory Airflow Control Devices
Operation Pressure

15. Control Methods and Accuracies
Laboratory Airflow Control Devices
Control Methods and Accuracies

16. Laboratory Airflow Control Devices
Control Methods
Closed Loop Control – Blade Damper Control Valve
A closed loop or feedback control measures actual changes in the controlled variable and actuates the controlled device to bring about a change. *
Airflow Control Methods **
Velocity Pressure
Vortex Shedding
Thermal Dispersion
*2005 ASHRAE Handbook – Fundamentals of Control, Chapter 15
** ASHRAE Laboratory Design Guide 2nd Edition; 2016, Chapter 11 - Controls

17. Laboratory Airflow Control Devices
Control Methods
Velocity Pressure *
Averaging pitot tubes, flow crosses, and orifice rings are examples of devices that measure and may amplify the velocity pressure
±5% accuracy can be read from the flow sensors down to 140 fpm (0.71 m/s) **
Pressure transducers have several types of errors that should be considered
Overall airflow sensing accuracy combines the effects of the probe and the pressure transducer.
*ASHRAE Laboratory Design Guide 2nd Edition; 2016, Chapter 11 – Controls
**ASHRAE Research Project RP-1353

18. Laboratory Airflow Control Devices
Control Methods
Velocity Pressure Error Example
2” Transducer w/ 0.50% Error of Full Scale.
CFM
Actual VP*
Transducer Error
Measured VP
Measured CFM
Error
1000
0.4522
0.01
0.4622
1011
1.1 %
500
0.1131
0.1231
522
4.3 %
200
0.0181
0.0281
249
24.5 %
120
0.007
0.0165
191
59.2 %

19. Laboratory Airflow Control Devices
Control Methods
Velocity Pressure Error Example
2” Transducer w/ 3% Error of Reading.
CFM
Actual VP*
Transducer Error
Measured VP
Measured CFM
% Flow
1000
0.4522
0.0136
0.4658
1015
1.49 %
500
0.1131
0.0034
0.1165
507
200
0.0181
0.0005
0.0186
203
120
0.007
0.0002
0.0067
122

20. Laboratory Airflow Control Devices
Control Methods
Vortex Shedding*
Vortex shedding devices measure airflow by measuring the pressure pulses or vortices formed on the leeward side of an obstruction in the airflow and calculating the airflow
±2.5% to 10% accuracy can be read from vortex shedding sensors down to 450 fpm
Response time for vortex shedders is typically slower than that of velocity pressure sensors.
*ASHRAE Laboratory Design Guide 2nd Edition; 2016, Chapter 11 – Controls

21. Laboratory Airflow Control Devices
Control Methods
Thermal Dispersion*
Thermal dispersion devices measure airflow through the use of thermistors in the airstream.
±3% of reading accuracy can be read from thermal dispersion sensors down to 50 fpm
check the manufacturer’s accuracy and speed of response to changes in airflow
as all thermal dispersion devices do not have the same accuracy and speed of response.
*ASHRAE Laboratory Design Guide 2nd Edition; 2016, Chapter 11 – Controls

22. Laboratory Airflow Control Devices
Airflow Control Concepts
Flow Characteristics of the Blade Damper Control Valve
In a closed loop flow control application, accuracy depends mainly on the airflow transducer but the resolution of the blade damper will greatly impact the flow measurement accuracy at low flows.
100%
“Quick opening” characteristic
Flow 0%
Closed
Full Open
Position

23. Laboratory Airflow Control Devices
Airflow Control Concepts
Open Loop Control – Venturi Valve Control
An open-loop control does not have a direct link between the value of the controlled variable and the controller. An open-loop control anticipates the effect of an external variable on the system and adjusts the set point to avoid excessive offset. *
Potentiometer
*2005 ASHRAE Handbook – Fundamentals of Control, Chapter 15

24. Laboratory Airflow Control Devices
Presentation Title
Version 00/00/00
Laboratory Airflow Control Devices
Airflow Control Concepts
No Airflow sensor – airflow is mapped to control arm position
Control: Drives to required airflow which is known position
Copyright© 2014, All Rights Reserved - Price Industries

25. Laboratory Airflow Control Devices
Airflow Control Concepts
Factory Valve Calibration
48 point characterization
NVLAP Accredited
N.I.S.T.* traceable
+/- 5% accuracy
Calibrated Flow Range
Error
30 scfm to < 100 scfm
4.0%
101 scfm to < 250 scfm
2.5%
251 scfm to < 5000 scfm
1.4%
*National Institute of Standards and Technology
Factory Valve Calibration
48 point characterization
N.I.S.T.* traceable equipment
+/- 5% accuracy

26. Laboratory Airflow Control Devices
Airflow Control Concepts
Flow Characteristics of the Venturi Valve
In an open loop application, flow control depends entirely on the flow versus position relationship of the valve but control resolution is improved at low flows.
100%
“Stable opening” characteristic
Flow 0%
Closed
Full Open
Position

27. Laboratory Airflow Control Devices
Speed of Response

28. Laboratory Airflow Control Devices
Speed of Response
Actuator Speed
No Hoods  Standard-Speed (90 sec. typical)
Hoods  High-Speed (< 4 sec. typical)

29. Laboratory Airflow Control Devices
PTP 3200 Critical Controls
January 5, 2014
Laboratory Airflow Control Devices
Speed of Response
Copyright© 2015, All Rights Reserved - Price Industries

30. Laboratory Airflow Control Devices
Speed of Response
Potentiometer
Potentiometer
Control Arm

31. Laboratory Airflow Control Devices
Speed of Response
ANSI Z9.5 – 2012 Section
VAV Response shall be sufficient to increase or decrease flow within 90% of the target flow or face velocity in a manner that does not increase potential for escape
A response time of <3 sec. after completion of the sash movement is considered acceptable for most operations. Faster response times may improve hood containment following the sash movement.

32. Laboratory Airflow Control Devices
Speed of Response
ANSI Z9.5 – 2012 Section
VAV Response shall be sufficient to increase or decrease flow within 90% of the target flow or face velocity in a manner that does not increase potential for escape
A response time of <3 sec. after completion of the sash movement is considered acceptable for most operations. Faster response times may improve hood containment following the sash movement.

33. Laboratory Airflow Control Devices
Speed of Response
ASHRAE Section 6.4
The sash shall be fully opened in a smooth motion at a velocity between 1.0 ft/s and 1.5 ft/s.
The time it takes from the start of the sash movement until the sash reaches the top and the time it takes from the start if the sash movement until the face velocity reaches and maintains, within 10%, the design face velocity shall be recorded

34. Laboratory Airflow Control Devices
Speed of Response
ASHRAE Section 6.4
The sash shall be fully opened in a smooth motion at a velocity between 1.0 ft/s and 1.5 ft/s.
The time it takes from the start of the sash movement until the sash reaches the top and the time it takes from the start if the sash movement until the face velocity reaches and maintains, within 10%, the design face velocity shall be recorded

35. Laboratory Airflow Control Devices
Speed of Response
NEBB Fume Hood Performance Testing - Section 9.3
VAV hoods are also to be tested to determine response time to return to a near steady state condition after a change in sash position.
When changing the sash position, use a smooth continuous motion and move the sash at a rate of approximately 1.5 ft/s.
Measure, record and report the VAV Speed of Response Time to first obtain a velocity equal to 90% of the baseline for each iteration.

36. Laboratory Airflow Control Devices
Speed of Response
NEBB Fume Hood Performance Testing - Section 9.3
VAV hoods are also to be tested to determine response time to return to a near steady state condition after a change in sash position.
When changing the sash position, use a smooth continuous motion and move the sash at a rate of approximately 1.5 ft/s.
Measure, record and report the VAV Speed of Response Time to first obtain a velocity equal to 90% of the baseline for each iteration.

37. Laboratory Airflow Control Devices
Speed of Response
0.8 Seconds
Venturi Valve – Time from completion of sash movement
*Results from testing completed at Engineered Air Balance Laboratory, Houston

38. Laboratory Airflow Control Devices
Speed of Response
2.5 Seconds
Venturi Valve – Time from start of sash movement
*Results from testing completed at Engineered Air Balance Laboratory, Houston

39. Laboratory Airflow Control Devices
Speed of Response
1.25 Seconds
High Accuracy Control Valve– Time from completion of sash movement
*Results from testing completed at Price Research Center North, Winnipeg

40. Laboratory Airflow Control Devices
Speed of Response
3.1 Seconds
High Accuracy Control Valve– Time from start of sash movement
*Results from testing completed at Price Research Center North, Winnipeg

41. Laboratory Airflow Control Devices
Maintenance

42. Laboratory Airflow Control Devices
Maintenance
Flow Measurement vs. Position Feedback

43. Laboratory Airflow Control Devices
Maintenance
No risk of airflow sensor buildup/interference

44. Laboratory Airflow Control Devices
Airflow Sound

45. Laboratory Airflow Control Devices
Airflow Sound
Valve Size
Flow (CFM)**
Terminal Discharge NC Value*
Terminal Radiated NC Value *
Venturi Discharge NC Value*
Venturi Radiated NC Value*
Size 8
400 21 31 23
Size 10
750 25 37 29
Size 12
900 27 32 24
Size 14
1500 26 41 44
*Test data obtained in accordance with AHRI Standard
*NC values are calculated based on typical attenuation values outlined in Appendix E, AHRI Standard
** Flow measurements taken at 1.5 in.W.C.

46. Material Options and Coatings
Laboratory Airflow Control Devices
Material Options and Coatings

47. Laboratory Airflow Control Devices
Material Options and Coatings
Aluminum Construction
Aluminum valve body and cone construction
Stainless steel internal hardware
PTFE Teflon coated center shaft
Clean air or non-corrosive applications

48. Laboratory Airflow Control Devices
Material Options and Coatings
Phenolic Coating - Class 1
Aluminum valve body and cone construction
Phenolic coated venturi body and cone
Stainless steel internal hardware and support brackets
PTFE Teflon coated center shaft
Typical for most fume hood applications

49. Laboratory Airflow Control Devices
Material Options and Coatings
Phenolic Coating – Class 2
Aluminum valve body and cone construction
Phenolic coated venturi body, cone and support brackets
PFA Teflon coated stainless steel internal hardware
PFA Teflon coated center shaft
No exposed metal
Chloric Acids
Bromine
Sodium Bisulfate

50. Laboratory Airflow Control Devices
Material Options and Coatings
PVDF Coating
Aluminum valve body and cone construction
Kynar® coated venturi body, cone and support brackets
PFA Teflon coated stainless steel internal hardware
PFA Teflon coated center shaft
Used in extremely corrosive applications:
No exposed metal
Nitric Acid
Hydrofluoric Acid
Sodium Hydroxide

51. Questions