HP Integrity rx7620 Server - User Service Guide, Sixth Edition

• Establish a no eating or drinking policy. Spilled liquids can cause short circuits in equipment
such as keyboards.
• 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, are not only unpleasant but corrosive as well.
Hydrogen sulfide damages wiring and delicate sound equipment. The use of activated charcoal
filters reduces this form of air pollution.
Metallic Particle 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 worn printer components. 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 can 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 might 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.
Electrostatic Discharge Prevention
Static charges (voltage levels) occur when objects are separated or rubbed together. The voltage
level of a static charge is determined by the following factors:
• Types of materials
• Relative humidity
• Rate of change or separation
Table C-2 lists charge levels based on personnel activities and humidity levels
Table C-2 Effect of Humidity on ESD Charge Levels
Humidity
2
and Charge Levels
3
Personnel Activity
1
50%40%32%26%
3,700 V4,625 V5,750 V6,150 VWalking across a linoleum floor
11,100 V13,875 V17,250 V18,450 VWalking across a carpeted floor
14,800 V18,500 V23,000 V24,600 VRising from a plastic chair
1 Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices (Bell Laboratories, 1981)
2 For the same relative humidity level, a high rate of airflow produces higher static charges than a low airflow rate.
3 Some data in this table has been extrapolated.
Static Protection Measures
To minimize possible ESD-induced failures in the computer room, follow these precautions:
• Install conductive flooring (conductive adhesive must be used when laying tiles).
• Use conductive wax if waxed floors are necessary.
• Ensure that all equipment and flooring are properly grounded and are at the same ground
potential.
• Use conductive tables and chairs.
190 General Site Preparation Guidelines