Why should I replace my bulbs if they still light?
UV-A and UV-C exposure bulbs lose output intensity over time. The gases inside the bulb become inert, resulting in longer start up time, while the UV output diminishes. This results in longer, inconsistent exposure times.
If you have an integrator on your exposure unit you may not be aware of the change because the integrator compensates for the difference. I suggest a weekly test of the number of seconds that correspond to the number of units for your standard exposure. This will enable you to determine how much strength your bulbs have lost. If you do not have an integrator I suggest doing a weekly exposure test using your own test negative or one supplied by your plate supplier. This negative should contain all of the standard elements needed to properly evaluate the plate. These include, various % screen blocks, isolated dots, lines, type, solids and reverses. By using the same exposure time each time and saving the last test plate for comparison you will be able to see any noticeable change in your exposure times. The most efficient method to test your bulbs is to use a uv meter, this units reads the bulb intensity and gives you a reading in numbers. You can record the readings and determine when your bulbs need to be replaced. It is widely recommend to replace your bulbs when get a reading below 1200.
When you first turn on the power to your equipment (cold start), it provides high voltage until the bulbs light. This strains the starting circuitry, power supply and the quartz (glass) of the bulbs. If you allow excessive start time to the cold start and exposures with old lamps you risk equipment failure.
Unreliable and inconsistent bulbs cause re-makes and wasted material and time. I suggest bulbs be replaced before they burn out. Save a few of your old ones as temporary replacements. When replacing bulbs, replace all of them at the same time. This will give you quicker exposure times and your equipment will operate at maximum efficiency.
How can I get the maximum usage from my bulbs?
Here are a few simple steps to get the most from your investment in new bulbs.
Use cotton gloves when installing new bulbs. If you clean them before use and install them using gloves you will avoid the oils from your fingers and other contaminants that can cause premature failure due to the high operating temperature in your exposing equipment.
Clean your bulbs on a regular basis to ensure the maximum reflected light.
Check the electrical contacts regularly for pitting or corrosion, which can cause arcing and failure of the bulb or equipment.
When installing new bulbs, apply pressure at the ceramic or metal ends never apply pressure to the quartz.
If your exposure unit has cooling fans and or filters, clean the blades, lubricate the motor bearings as needed and check to make sure the fans are operating properly. The vents must be clean and free of any obstruction to allow for maximum ventilation and unrestricted airflow. Keeping your bulbs cool will improve their life.
Make sure that the bulbs you are using are the correct type for your equipment. Many units require specific spectral output. If you change types, make sure your equipment is compatible.
When you install new bulbs, record the date, life hours and bulb part number. This simple record will help you establish an effective maintenance and replacement schedule.
And lastly, don't be intimidated by equipment manufacturers who insist you use only their brand of bulb. The bulb simply receives the output from the power supply, so it cannot harm your equipment. Just be certain to buy from a reliable supplier that will make sure you the correct bulb for your equipment, and help you should a problem arise.