Today’s ultraviolet (UV) systems, including those used in small community and industrial water systems, are far superior to yesterday’s legacy systems. But that doesn’t mean legacy systems are ready for the trash heap. Many UV systems that are 20 to 30 years old can still operate as well as they did when they were installed. They just require a little “TLC” to get them back to their original operating condition.

A well-maintained system is all that is required. Proper maintenance goes beyond the obvious annual lamp change-out, the cleaning of the interior of the quartz sleeve, and a sensor adjustment. A new preventive maintenance (PM) perspective can be applied to any existing UV system.

Points of a good PM program
Where to start? Begin with the owner’s manual. Most reputable UV manufacturers provide a manual with each unit. It should contain a well-laid-out PM schedule. If not, consider the following guidelines.

Design material. UV light is aggressive and will oxidize or corrode just about everything it comes into contact with, including improperly finished stainless steel. If a UV system is not manufactured with high-quality material and is not properly maintained, it will cause maintenance issues down the road.

UV lamps. All UV units incorporate a single or multiple UV lamp(s), the units’ critical component, into their designs. Each unit requires periodic lamp replacement. While many lamps will continue to operate well beyond their stated life, a lamp’s performance declines if it operates for too long.

Typically, lamp replacement should be scheduled at no later than 4,000 to 5,000 operating hours for medium-pressure systems and 9,000 hours for low-pressure systems. Medium-pressure systems with variable output power settings will now achieve a 9,000-hour lamp life. Whatever system you have, do yourself a favor and don’t wait for the lamp to burn out before replacing it.

A physical process called solarization eventually blocks UV light from being emitted into the water stream, rendering it ineffective by preventing vital UV rays from penetrating the water stream. As a lamp becomes solarized, it turns slightly brown in color and should be replaced.

Mercury disposal. All UV lamps contain mercury. More companies are becoming environmentally conscious and looking for responsible waste disposal programs for their lamps.

If you are a small-system operator, be sure the water treatment service company has a program in place to properly dispose of the lamps. Expect to pay a fee per lamp to have it picked up and the mercury inside it properly extracted, recycled and disposed of.

UL-listed equipment. Most reputable UV equipment is UL-listed in the United States. A UV manufacturer typically receives their UL listing on the entire unit, not on each individual component of the unit. Should non-genuine UV replacement parts be incorporated into the equipment, the unit’s UL listing would become void. For this reason it is not recommended that non-genuine OEM replacement parts be incorporated into UV systems.

Before you decide to incorporate the slightly less-expensive generic aftermarket replacement parts into your UV system, check with your risk management team and insurance provider to determine if the risks associated with this decision are worth the relatively few dollars saved.

Quartz sleeves. The quartz sleeves are probably the most abused components of a UV system, yet they are one of the most critical for delivering UV rays into the water stream.

Sleeves provide a protective barrier around the lamp so that the lamp can operate at its optimal temperature. For the quartz sleeve to maximize a unit’s performance, both the interior and exterior of the sleeve must be cleaned periodically, even in UV units installed in ultra-pure water systems. All quartz sleeves are susceptible to fouling.

Cleaning frequency of quartz sleeves will be site-specific and directly related to water quality. UV systems that are installed in post-reverse osmosis/deionization (RO/DI) locations will require cleaning much less frequently than units installed on raw water or surface water systems. As a general rule of thumb, a post-RO/DI system should have the quartz sleeves cleaned once a year.

Plan on cleaning quartz sleeves quarterly on post-activated carbon systems and more frequently for hard water applications exceeding 5 grains of hardness.

Sleeve replacement. Quartz sleeves, just like UV lamps, wear out over time. Quartz will lose its ability to transmit UV rays into the reactor chamber. To maximize the optimal performance of any UV unit, manufacturers recommend that the quartz sleeves be replaced with each lamp replacement. Most system operators typically replace their quartz sleeves every three to five years in disinfection applications, and replace them every one to three years in TOC-reduction, ozone-destruction and UV-dechlorination applications.

Reactor chamber. Many system operators and service companies overlook the importance of cleaning the interior of the UV reactor chamber. The inside of a reactor chamber acts as a mirror to reflect UV light back into the water stream. When it becomes fouled or scaled, it loses its reflective qualities. The interior of a reactor chamber may need to be cleaned physically. A unit’s performance will suffer if this important step is ignored.

Replacement parts. Don’t forget to stock a few replacement lamps, quartz sleeves and O-rings for those unexpected emergencies. Quartz sleeves are like glass. They are fragile and they tend to break when improperly handled or abused. If replacement quartz sleeves are not readily available and one breaks, a complete water system could be shut down until a replacement is located.

Imagine a commercial/industrial customer’s cost of lost revenue, when, while they normally produce $100,000 to $1 million worth of product an hour, one or several replacement quartz sleeves are not on hand. Don’t be so frugal that a whole system has to shut down due to the lack of a $40 to $100 quartz sleeve.

Matched power supply. This is critical to the overall performance of UV equipment. UV manufacturers have gone to great lengths and expense to develop power supplies for their specific equipment to maximize the unit’s output. They want the surface-wall temperature of their lamp to operate at a particular temperature for a particular application, and they have to drive the lamp at a certain voltage and current to achieve the desired temperature.

When original ballasts burn out, some operators have found that off-the-shelf generic ballasts easily can be substituted for the original equipment. Don’t make this assumption, because the equipment’s performance will likely suffer. Plan to replace their ballasts every five to seven years.

Lamp sockets. This is another critical UV component that is often overlooked. Lamp sockets deliver the necessary voltage to the UV lamp to produce the output. Like everything else, lamp sockets wear out over time. Plan on replacing them every three to five years.

O-rings and gaskets. These maintain the hydraulic integrity of the equipment. Yet, O-rings and gaskets are often overlooked in the annual PM schedule and are not replaced until the unit starts leaking. Think about it: O-rings and gaskets are usually directly exposed to UV light, and in a short period of time the elastomers of which they are made become brittle, crack and leak.

Change the O-rings once a year and the gaskets every two years to avoid leaks and the potential leaching of contaminants into your critical systems.

Dirt and dust. A UV unit incorporates a number of critical electrical connections in the unit design. In many cases, cooling fans are used to move air across heat-sensitive components. After two to three years of continuous operation, the inside of a UV unit’s electrical enclosure becomes filled with dust, dirt and grime. Add a small, persistent water leak and you will have quite a mess on your hands. Over time, this dirt and dust works itself into the electrical connection, reducing the integrity of that connection.

Set up an annual PM schedule to vacuum out the inside of each electrical enclosure. For units that incorporate a built-in dust fan, don’t forget to clean or replace that filter as well. Your unit will be easier to maintain and will operate more efficiently.

Intensity meter and sensor. Not too long ago, the only option available to measure UV intensity was a meter that provided a zero to 100 percent relative intensity measurement. This meter design was far from accurate, but it did provide a rough idea of the lamp’s condition. That is, if it were allowed to operate as initially intended.

No one likes to see UV intensity below that 100 percent level, although that’s what happens as a UV lamp ages. Too many individuals will go around and adjust, or shall we say recalibrate, the intensity up to that magical 100 percent level. This process tended to defeat the purpose of the sensor as a viable tool:

In a perfectly operating system, one would clean their quartz sleeves, install new UV lamps, clean the UV intensity probe and reassemble the unit. With the lamps on and operating at their correct operating temperature, the intensity meter would be adjusted to 100 percent. After 72 hours of operation, the new lamp’s intensity would drop off until the lamp’s output stabilized. This required a technician to come back and adjust the intensity meter back to 100 percent. Over the course of 8,000 to 9,000 hours, the UV intensity would drop by 40 percent from that new, adjusted intensity level. At a 60 percent intensity level, the unit would be telling you that either the quartz sleeves were dirty, one or more of the lamps had failed, or all the lamps needed to be replaced because they had reached their end of lamp life.

Incorporating a relative intensity meter and probe into your UV system is no longer considered “best practice.” If you still operate a system with one of these antiquated instruments, the time has come to bring your UV unit into the 21st century.

Digital intensity meters that read absolute intensity have been available for several years. They are far superior to the old 0-100 percent analog meters they replaced. Digital meters can be hot-water sterilized or steam sterilized, and some can even be provided with an optional NIST certificate. It’s one of the best upgrades you can make on older units. Plan to replace UV intensity probes every three to five years.

Final thoughts
A properly maintained UV system will dramatically extend the useful life and performance of your customer’s investment. A UV system is one of the most cost-effective components of any water treatment system. Follow your owner’s manuals for advice on establishing your own PM schedules, and if you are not sure how to maintain a system, contact an experienced professional for advice.