PLS 2014: Vent to Prevent: How pressure equalization prevents premature failure of outdoor luminaires

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

Pressure equalization

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.

How can this condensation be removed?

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.

High Concentration Low Concentration

Rate

Moisture Diffusion – Small Opening

High Concentration Low Concentration

Rate

Moisture Diffusion – Large Opening

Comparative Study

IP66 Rated

Light ConstructionOne piece aluminum shell

Lens and LED

Latch door for pole installation

and wire connection

Water proof housing for LED

driver

Vented vs. Non Vented

• Temperature

• Pressure

• Relative Humidity

Thermal Shock Wash Down Cycle

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

Pressure

Relative Humidity

Additional example:

Life Time Study

Gore® Protective Vents

1 532 4

European Alps

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

Visible results

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]