Air-Cooled and Water-Cooled Xenon Arc Lamps: A Comparison
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Last Updated 2025
Xenon-arc lamps generate significant amounts of heat and require cooling for proper operation. Two basic types of xenon-arc lamps are available: air-cooled and water-cooled. When properly maintained, both are capable of delivering the same weathering test conditions and results. However, air-cooled systems offer significantly lower operating costs, simpler maintenance, and fewer calibration requirements—making them the more practical choice for most testing laboratories. This article will discuss some key points and differences between these two widely-used technologies.
Are Both Lamp Types Permitted in Test Standards?
Yes! Nearly every major international and national test standard, as well as most OEM standards, allow for the use of both lamp types.
Are the light spectra different?
No, generally speaking. The cooling method doesn't affect the lamp output spectrum, which is determined by optical filter selection. Both systems deliver equivalent light spectra when properly maintained and calibrated, which is why international weathering standards accept both cooling techniques.
The critical factor is maintenance consistency—particularly for water-cooled systems where optical filter aging can impact UV light output from the lamps if not addressed on schedule.
Understanding Xenon Arc Lamp Cooling
Xenon arc lamps generate substantial heat during accelerated weathering testing, requiring active cooling to prevent overheating. The two primary cooling methods—air and water—each impact tester design, operation costs, and maintenance schedules differently.
Air-cooled lamps use cooling fans or blowers to maintain proper operating temperatures. These systems are simpler in design and require no water input.
Water-cooled lamps circulate deionized water through lamp assemblies, with tap water serving as a heat exchanger. While water offers more effective heat transfer and allows the use of higher-power lamps, it adds complexity to the system.
Operating Costs
Water-cooled systems require continuous tap water flow at several liters per minute. Depending on your region, this can add significant expense to your laboratory testing. Chilled heat exchanger systems can reduce water consumption but will increase electricity costs per year depending on your region.
Air-cooled systems eliminate cooling water costs entirely.
Lamp Replacement Costs
Air-cooled lamps from Q-Lab are warrantied at Typical irradiance values for 3,000 hours (Xe-1, Xe-2, Xe-3) or 8,000 hours (Xe-8). Lifetimes vary for water-cooled lamps, but 1,500-2,000 hours is typical. The cost to replace each is a major difference, as water-cooled lamps are several times more expensive to replace than air-cooled lamps.
Optical Filter Maintenance and Cost
This is where the systems diverge most dramatically.
Air-cooled systems: Q-Lab optical filters don't "solarize," or age, maintaining a consistent transmission indefinitely. With the exception of Window-IR filters, Q-Lab optical filters for air-cooled testers never require replacement. Some air-cooled systems may require periodic filter replacement at 4,000-15,000 hours depending on the manufacturer.
Water-cooled systems: Filters must be replaced regularly due to transmission degradation. A typical replacement scheme is:
- Inner filter: every 400 hours
- Outer filter: every 2,000 hours
Filter solarization for water-cooled lamps reduces UV spectrum output over time, potentially affecting test accuracy and adding significant maintenance time and expense.
Calibration and Maintenance
| Air-Cooled Lamps | Water-Cooled Lamps |
|---|---|
| Lamp Replacement: every 3,000 or 8,000 hours | Lamp Replacement: every 1,500-2,000 hours |
| Calibration: simple procedure every 500 light hours using a calibrated irradiance sensor | Complicated calibration process every 500 light hours, typically using a calibrated reference lamp |
| Periodic cleaning of housings and filters | Frequent filter cleaning, periodic cleaning of lamp reservoir and water gasket |
Making the Right Choice for Your Lab
When selecting a xenon arc weathering tester, consider:
- Total cost of ownership: Consider water costs, electricity, lamp replacements, and filter maintenance
- Maintenance resources: Water-cooled systems require more frequent attention and technical intervention
- Infrastructure: Water-cooled systems need a reliable tap water supply; any interruption stops testing
- Long-term filter stability: Air-cooled systems offer more consistent optical filter performance over time
For most laboratories, air-cooled xenon arc systems provide excellent reliability, cost-effectiveness, and ease of maintenance while delivering the accurate, reproducible test results your quality program demands.
All of Q-Lab testers use air-cooled lamps, but water-cooled lamps and filters are available for purchase to use in Atlas testers.
Conclusion
While both cooling methods are viable for accelerated weathering testing, air-cooled xenon arc lamps offer distinct operational advantages. Lower operating costs, reduced maintenance complexity, and superior filter stability make them an efficient choice without compromising test quality.
Ready to start your testing journey? Contact our team today to get started.
Frequently Asked Questions:
Q: Are both lamp types permitted in internationally recognized test standards?
A: Yes! Both air-cooled and water-cooled lamps deliver nearly the same result, and are allowed by nearly every major international test standard.
Q: What is the main difference between air-cooled and water-cooled xenon arc lamps?
A: The primary difference lies in the cooling method. Air-cooled lamps use ambient air circulation to dissipate heat, while water-cooled lamps require a continuous supply of deionized water flowing around the lamp to regulate temperature. This fundamental design difference impacts operating costs, maintenance requirements, and overall system complexity.
Q: Which type of lamp is more cost-effective?
A: Air-cooled xenon arc lamps are significantly more cost-effective. They eliminate the need for expensive deionized cooling water, reduce maintenance expenses, and have lower operating costs overall. Additionally, air-cooled systems have simpler infrastructure requirements since they don't need water purification and circulation systems.
Q: How long do air-cooled vs water-cooled lamps typically last?
A: Q-Lab's air-cooled xenon arc lamps for Q-SUN Xe-1, Xe-2, and Xe-3 testers are warrantied for 3,000 hours at normal irradiance and 1,000 hours at high irradiance. Air-cooled lamps used in the large-capacity Q-SUN Xe-8 are warrantied for 8,000 light hours at normal irradiance. Water-cooled lamp lifespans vary by manufacturer but generally have comparable or shorter lifespans, though this can depend on the specific model and usage conditions.
Q: What are the maintenance differences between the two systems?
A: Air-cooled systems require significantly less maintenance. They don't need water quality monitoring, deionized water replenishment, or cooling system maintenance. Lamp replacement in air-cooled systems is typically simpler and can be performed from the front of the unit with minimal steps. Water-cooled systems require ongoing maintenance of water circulation systems, regular water quality checks, and more complex lamp replacement procedures.