PLS 2014: Vent to Prevent: How pressure equalization prevents premature failure of outdoor...
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Transcript of PLS 2014: Vent to Prevent: How pressure equalization prevents premature failure of outdoor...
Vent to Prevent
How pressure equalization
prevents premature failure of
outdoor luminaires
Presented by: Susan Chambers
W L Gore & Associates UK Limited
Content:
• Basics of pressure equalization
• Preventing pressure differentials
• How condensation forms
• Diffusion process
• Comparative Study – LED Streetlight
- vented v’s non-vented
• Life time study results
• Conclusions
Causes of pressure fluctuations
Temperature changesHeat generating internal
electronics / external weather
patterns – rain/sun/wind
Altitude changesIn transit or during use
Pressure fluctuation
Pressure build-up
Stress on seals
Compromised seals
Product failure
Causes of pressure differentials
Protecting the electronics
Desiccants+ Bind the relative humidity within the enclosure- Cannot equalize pressure
Potting+ Encapsulates electronics against contaminants- Stresses electronics - Prevents long-term maintenance or recycling- Requires labour-intensive chemical processes
Tortuous paths or leak hole+ Equalize pressure- Typically cannot achieve required IP levels
Venting+ Rapidly & continuously equalize pressure+ Effectively reduce condensation+ Block ingress of dust, dirt and water
ePTFE Membrane Properties
• Engineered with expanded PTFE
• Microporous structure
- Blocks liquid and particulates
- Allows air and vapor to flow freely
• Diffusion of corrosive gases
In the case of sealed housings, it is important to note that humidity from the air can enter the
inside of the housing ;
- either by air inclusion during the production process
- and/or via the housing seal
- or during operation due to penetration through the housing plastic
How does condensation form?
(thermodynamics)
What is condensation?
Condensation refers to the change of state of a substance from the gaseous to the liquid state
of matter caused by temperature differences. This process results in the formation of
condensation.
Plastic absorption rates
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
Wa
ter
Ab
so
rpti
on
(%
wt)
Water Absorption for Various Plastics
(24 hrs ASTM D570)
Maximum
Minimum
2.8 Maximum
W. L. Gore & Associates
Without ventilation, the trapped condensation is not able to escape
and there is a risk of corrosion on the sensitive electronic components.
Effects of condensation
GORE Corrosion Test - exposure to temperature cycles
in combination with submersion under water.
W. L. Gore & Associates
Diffusion: direction of water vapour
• The diffusion direction of water vapour exclusively
depends on the absolute air humidity, and is always in
the direction from a high to a low concentration.
• Diffusion is a physical process which leads to an
even distribution of particles, and therefore the
complete mixing between two or more substances.
• Diffusion is based on the thermal proper motion of
water vapour particles.
Light ConstructionOne piece aluminum shell
Lens and LED
Latch door for pole installation
and wire connection
Water proof housing for LED
driver
Temperature
0
10
20
30
40
50
60
6/20 00:00 6/20 12:00 6/21 00:00 6/21 12:00 6/22 00:00 6/22 12:00 6/23 00:00
Date and Time
Te
mp
era
ture
(°C
)Sealed Temp (°C)
Vented Temp (°C)
Ambient temp (°C)
Test # 1,
midday
Test # 2,
early morning
Test # 3 and 4,
midday
Differential Pressure
-150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150-150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150
-150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150 -150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150 -150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150
-150mbar< Box1 <131mbar
No Vent
-149mbar< Box2 <147mbar
No Vent
-30mbar< Box3 <30mbar
One Vent (side)
-4mbar< Box5 <4mbar
Two Vents (side)
-40mbar< Box4 <41mbar
One Vent (top)
Almost atmospheric conditions for the Gore® vented boxes
High differential pressure for the non-vented boxes
Gore®
Protective Vents reliability
Vent of Box 5 Vent of Box 5 New Vent
Airflow @ 70mbar
[ml/min] 320 340 400
WEP
@ [0,6 bar/60s] OK OK OK
Membrane after 5 years
in outdoor use
Gore® Protective Vents are still functioning after many years
in outdoor use!
Product after 5 years
in outdoor use
(No UV degradation) (No UV degradation)
Conclusion
• Pressure differentials, caused by temperature changes, compromise the housing seals.
• Vacuum occurs reducing long-term performance.
• Condensation build up decreases light efficiency.
• Integration of an ePTFE vent equalizes pressure, allowing continuous airflow, reducing condensation.
Thank you
FOR INDUSTRIAL USE ONLY.
Not for use in food, drug, cosmetic or
medical device manufacturing,
processing, or packaging operations
For further information:
Web: www.gore.com/protectivevents
Email: [email protected]