Impact of Various Lamp Intensity Measurement Methods on the End of Lamp Life (EOLL) of Low-pressure High-output Germicidal UV lamps

B. Ferran1, W. Yang1, N. Fontaine2

1Suez WTS, 600 Willow Tree Road, Leonia, NJ 07605

2Carollo Engineers, 2880 Gateway Oaks Drive, Suite 300 Sacramento CA 95833

Introduction

• The 2003 NWRI UV Disinfection Guidelines stipulate that to account for the degradation in lamp UVC output over time, the design UV dose of a UV plant must be adjusted using an EOLL, or lamp aging factor.

• Suez WTS conducted a third party aging test on a batch of 18 aquaray®

3X lamps of the low-pressure high-output type.

• Testing was conducted per the 2003 NWRI UV Guidelines as the 2012 NWRI UV Guidelines were issued after the start of the study

• Lamps were measured both in-air and in-water to evaluate the progressive change in UVC output over time

• End of life test data is compared between in-air & in-water measurements

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Methodology

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• The lamps were aged inside a full-scale

UV module submerged in a tank filled

with temperature controlled and

circulating water.

• All lamps were aged at maximum

electrical power using the same power

centers as in the field.

• The lamps were aged under varying

water temperatures

Aging

Tank

Chiller

Aging Module

Lamp Aging Test Setup

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Methodology

Lamp

3-meter distance

IL1700 SED240 cell

IL1700 Radiometer

Dark room for lamp output

measurements in air

• Lamp output measurements in air were

conducted in accordance with the

original 2008 IUVA methodology.

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Methodology

5 Sensor Ports

Temperature probe

Cooling water

IL1700 SED240 cell

• Lamp testing in water was conducted using

a single-lamp stainless steel vertical

chamber continuously fed with high

transmittance temperature controlled water.

• Local intensities were measured through

water using an IL1700 radiometer with the

SED240 cell at five fixed locations

alongside the lamp axis.

• Temperatures at the bottom and top of the

water chamber were monitored to confirm

proper cooling at all times.

Test chamber for intensity

measurements in water

Results

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EOLL versus Percent of Nominal Lifetime

• The relative output for each session was calculated by dividing the average

measured intensity from the test lamps by the average measured intensity

from reference lamps.

• The EOLL for the aquaray® 3X lamp obtained from in-air and in-water

measurements is the same at 0.90.

• Between 11% and 58% of nominal lamp lifetime the lamp output

measurements collected in-water resulted in slightly lower EOLL values

compared to in-air.

• At 58% of nominal lifetime and greater the measured EOLL factors

became similar regardless of the measurement approach.

Results

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• The data generated from this aging test yields the same EOLL

regardless of whether the test lamps were measured in-air for output or

in-water for intensity.

• Note that those EOLL values from in-water measurements were slightly

lower than their in-air counterpart for approximately half of the entire test

period.

Conclusion

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