Appendix C: Example UV Lamp Testing Report
Third-Party Report on UV Lamp Testing of 250 W UV Lamps in Air
Consulting Company Name
UV Lamp Company Name
Attention: Contact Person
Date of the tests: ________________
Products tested: (description of UV lamps tested)
Objectives: To obtain performance data for the tested lamps, and specifically to determine:
- the UVC irradiance at 4.0 m
- the electrical operating parameters
- the UVC efficiency of the lamps using the IUVA Lamp Testing Protocol
- Lamp ballast: manufacturer, model number and serial number
- UVC radiometer: manufacturer, model number and serial number, date of calibration and attach a copy of the calibration certificate
- Power analyzer: manufacturer, model number and serial number, date of calibration and attach a copy of the calibration certificate
- All UV lamps tested were “burned in” for a period of at least 100 h – see attached letter.
- The measurement protocols and calculations followed as far as possible the method proposed by the International Ultraviolet Association (IUVA).3 The efficiencies were measured as a function of the distance from the lamp, and a distance of 4.0 m was chosen, since efficiencies were found to be independent of this distance between 3 and 6 m from the center of the lamp. A two-chamber method was used to greatly reduce the reflected UV, which was measured and subtracted from the irradiance measurements.
- All lamps were mounted in air, horizontally, in a low-reflectance chamber (see Figures C1 and C2).
- The UVC detector was placed on a tripod mount at 4.0 m on a line out from the center of the lamp to the calibration plane of the detector and at the same height as that of the UV lamp (see Figure C3).
- A black-painted slotted divider was fabricated, which completely separated the lamp chamber from the detector chamber (see Figures C3 and C4). The divider had a rectangular hole 160 cm by 5.0 cm centered in the divider. This divider was mounted at a distance of 35 cm from the UV lamp and positioned so that the entire UV lamp could be “seen” through the hole in the divider at the detector position.
- Periodically black-painted pieces were placed over the slot in the divider to block any direct rays from the lamp reaching the detector. The meter readings from this test (which indicated reflected UV from the walls that reached the detector) were subtracted from all meter readings. In fact, the reflected UV was undetectable when the slot was so covered.
The room temperature during the tests was 28°C.
- Measurement results are valid only for the individual setup and the tested lamps. Test results may vary based on different environmental conditions, such as in a water-filled reactor.
- All measurements were made at the time of the peak lamp output (peak irradiance). The reason is that UV lamps overheat in air, and consequently the efficiency can drop significantly. Since these UV lamps are designed to work inside a quartz sleeve with water flowing outside the sleeve, the lamp temperature would be controlled, so the peak efficiency is the appropriate calculation. In fact, for the lamps tested, the lamp efficiency was virtually independent of time after the time of peak irradiance.
Figure C5 shows the growth curve for one of the 250 W UV lamps. The lamp reached a “steady-state” at about 10 min and had a peak output at 92 s.
Lamp efficiency vs. distance results
The radiometer detector was placed a various distance from the UV lamp. Table C1 shows the results.
It is clear that the calculated UVC power is independent of distance for distance greater than 4 m. Thus this distance was chosen as the distance for the testing.
Lamp efficiency results
Table C2 gives the test results for the 10 lamps tested.
- All measurements were made at the time of peak irradiance.
- After subtracting the irradiance with a cardboard mask to block the direct UV light from the lamp, the radiometer readings were multiplied by the calibration factor 1.209.
- Calculated using the Keitz formula: , where
E is the net measured irradiance (W m-2) at 254 nm
L is lamp length (1.465m) from electrode tip to electrode tip
D is distance (m) from lamp center to the sensor (here D = 4.00 m)
α is the half angle (radians) subtended by the lamp at the sensor position. That is, tan α = L/(2D)
- The relative uncertainty is calculated as twice the standard deviation of the mean (95 percent confidence level).
- The ratio of the power from the wall to the power across the lamp was found to be 0.927; hence, the average efficiency with respect to power from the wall is (33.4 ± 0.4) percent.
Note that the Keitz calculations were carried out for a distance 4.00 m from the lamp. Measurements were made at other distances (see Table C1), and it was established that when the radiometer detector is placed at 4.00 m from the UV lamp, it “sees” virtually the entire lamp with a cos ? response, and hence the lamp efficiencies, as calculated from the Keitz formula, are considered accurate at this distance.
- Dr. _______ supervised and witnessed all lamp tests.
- The efficiencies reported here are for lamps operated in open air. The efficiencies inside a quartz sleeve inside a UV reactor with water flowing outside the quartz sleeve will likely be different because of a different thermal environment around the lamp.
- The lamps for testing were from among the stock of this lamp type and were selected at random by Dr. _______ from a set of 25 serial numbers. The selected lamps were then “burned-in” for 100 h.
The uncertainties given in Table C2 assess the relative uncertainty of the results. The principal source of the absolute uncertainty arises from the uncertainty of the radiometer calibration. The radiometer manufacturer states that this uncertainty is 5 percent. Thus, including the relative uncertainty, the absolute uncertainty is about 6 percent. Since the reflected light was undetectable when the port between the two chambers was blocked, reflected light does not contribute to the uncertainty.
The average lamp efficiency relative to power across the lamp was (36.0 ± 0.4) percent. The lamp efficiency with respect to power from the wall was (33.4 ± 0.4) percent.
The average peak UVC power emitted by the lamps was 109.3 W for an average electrical power input of 303.6 W (the electrical power at steady state was 276.7 W).
The average irradiance at 1.0 m from the lamps is estimated to be 8.27 W m-2 or 0.827 mW cm-2.