Stitzell Electric Supply Co., Inc.

"THE SLUMPER STORY"

WHAT HAPPENS WHEN THERE'S NOT ENOUGH

MERCURY IN A FLUORESCENT LAMP?

     Mercury is a required element in fluorescent lamp product.  "Slumper" is a term used to describe fluorescent tubes which fail to come to full performing value due to mercury depletion.  Many "slumpers" appear to be pink in color and lack full brightness.  Others show other characteristics of poor performance such as stirations which appear to be in motion along the lamp wall.  An example of a "slumper" is shown below:

      Why do certain lamps show outward signs of mercury depletion while others do not?  Some lamp manufacturers have chosen to reduce the mercury content of their lamps to extremely low levels.  They hope to claim a sales advantage by selling end users that their lamp contains the lowest amount of mercury in the industry.  In doing so, they may have hit the threshold where  lamps may pass their manufacturing quality control but fail to perform properly in the field.  The net result is poor performance, as exhibited in these pictures, commonly known as "slumpers." 

     These pictures are from the Des Moines Metro Area taken in January, 2005.  They represent a variety of installations including office space, food retail, big box retail, and hospital facilities. These are all Philips brand "Alto™" lamps with date codes ranging from 2002-2004.  Since most users replace their "slumpers" as soon as they are spotted,  the full scope of the problem is never seen.  

         The pink color is the usual tell-tale sign that a lamp is suffering from mercury starvation.   Pink is the argon discharge in the lamp.  If the mercury dosing is too low, both color appearance and color rendition will be dramatically affected.

                                                 

       All fluorescent lamp production begins with some form of pure recycled mercury which is added to the lamp to make the lamp operate properly.  As a lamp operates and ages, the mercury within the lamp combines with the glass wall of the lamp, the phosphors of the lamp, with "getter" (impurities) in the lamp and other materials around the filament.

      When mercury combines with these substances, it effectively becomes mercury oxide.  Mercury oxide plays no role in the fluorescent production of light.  Only free, pure or recycled mercury produces light.  

 

        With insufficient mercury dosing, fluorescent lamps will consume internally most of the available pure mercury before reaching rated life.   If the mercury dosing of a fluorescent lamp is too low, not only will a lamp begin to appear pink in color, the maintained lumen output of the lamp with be dramatically reduced. 

              Because lamps are subject to different operating conditions in different facilities, part of the "slumper" phenomenon could result from a combination of very low mercury content and the actual lighting system itself.  For example, mercury is depleted in tiny quantities each time a lamp is switched on.  If your system is turned on and off frequently, your system usage would be potentially depleting the already very low mercury content of the lamp at a faster rate than those system with only one or two starts per day. 

            More mercury is depleted when a lamp is "hard started" than when started more easily.  Newer, electronic instant start ballast start the lamp harder than most other types of ballasts.  Additionally, air temperature plays a role in how hard a lamp starts.  The cooler or colder the air temperature, the harder it is to start a fluorescent lamp.  Hard starting a lamp consumes more mercury than is otherwise needed under normal operating conditions.

   

           Even if a manufacturer would test start each lamp before shipping, the end user might be using the lamp in a manner which aggravates a mercury dosing issue, thus creating the "slumper." 

           Nevertheless, the lamp manufacturer has a responsibility to dose each lamp with enough mercury to insure it's proper field operation in all reasonable normal operating atmospheres.