Metallic Particulate Contamination - HP Integrity rx8620 Site Preparation Manual

General Site Preparation Guidelines
Environmental Elements
Specifically, disk drives, tape drives, and some other mechanical devices can have bearing failures resulting
from airborne abrasive particles. Dust might also blanket electronic components like printed circuit boards,
causing premature failure due to excess heat or humidity buildup on the boards. Other failures to power
supplies and other electronic components can be caused by metallically-conductive particles, including zinc
whiskers. These metallic particles are conductive and can short circuit electronic components. Use every
effort to ensure that the environment is as dust- and particulate-free as possible. See the following heading
titled "Metallic Particulate Contamination" for additional details.
Smaller particles can pass though some filters and, over time, cause problems in mechanical parts. Small
dust particles can be prevented from entering the computer room by maintaining the air-conditioning system
at a high static air pressure level.
Other sources of dust, metallic, conductive, abrasive, and microscopic particles can be present. Some sources
of these particulates are:
• Subfloor shedding
• Raised-floor shedding
• Ceiling-tile shedding
These particulates are not always visible to the naked eye. A good check to determine their possible presence
is to check the underside of the tiles. The tile should be shiny, galvanized, and rust-free.
The computer room should be kept clean. The following guidelines are recommended:
• Smoking—Establish a no-smoking policy. Cigarette smoke particles are eight times larger than the
clearance between disk drive read/write heads and the disk surface.
• Printer—Locate printers and paper products in a separate room to eliminate paper particulate problems.
• Eating or drinking—Establish a no-eating or drinking policy. Spilled liquids can cause short circuits in
equipment such as keyboards.
• Tile floors—Use a dust-absorbent cloth mop rather than a dry mop to clean tile floors.
Special precautions are necessary if the computer room is near a source of air pollution. Some air pollutants,
especially hydrogen sulfide (H2S), are not only unpleasant, but corrosive as well. H2S damages wiring and
delicate sound equipment. The use of activated charcoal filters reduces this form of air pollution.

Metallic Particulate Contamination

Metallic particulates can be especially harmful around electronic equipment. This type of contamination can
enter the data center environment from a variety of sources, including but not limited to, raised floor tiles,
worn air-conditioning parts, heating ducts, rotor brushes in vacuum cleaners, or printer component wear.
Because metallic particulates conduct electricity, they have an increased potential for creating short circuits
in electronic equipment. This problem is exaggerated by the increasingly dense circuitry of electronic
equipment.
Over time, very fine whiskers of pure metal can form on electroplated zinc, cadmium, or tin surfaces. If these
whiskers are disturbed, they may break off and become airborne, possibly causing failures or operational
interruptions. For over 50 years, the electronics industry has been aware of the relatively rare, but possible
threat posed by metallic particulate contamination. During recent years, a growing concern has developed in
computer rooms where these conductive contaminants are formed on the bottom of some raised floor tiles.
Although this problem is relatively rare, it can be an issue within your computer room. Since metallic
contamination can cause permanent or intermittent failures on your electronic equipment, HP strongly
recommends that your site be evaluated for metallic particulate contamination before installation of
electronic equipment.
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Chapter 2