HP Integrity rx5670 Site Preparation Guide - HP Integrity rx5670 (A6837B/A683 - Page 24

General Site Preparation Guidelines Environmental Elements Although this problem is relatively rare, it may be an issue within your computer room. Since metallic contamination can cause permanent or intermittent failures on your electronic equipment, Hewlett-Packard strongly recommends that your site be evaluated for metallic particulate contamination before installation of electronic equipment. ESD 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 2-1 Effect of Humidity on ESD Charge Levels Personnel Activitya Humidityband Charge Levels (voltages)c 26% 32% 40% 50% Person walking across a linoleum floor 6,150 V 5,750 V 4,625 V 3,700 V Person walking across a carpeted floor 18,450 V 17,250 V 13,875 V 11,100 V Person getting up from a plastic chair 24,600 V 23,000 V 18,500 V 14,800 V a. Source: B.A. Unger, Electrostatic Discharge Failures of Semiconductor Devices (Bell Laboratories, 1981) b. For the same relative humidity level, a high rate of airflow produces higher static charges than a low airflow rate. c. Some data in this table has been extrapolated. Static Protection Measures Follow these precautions to minimize possible ESD-induced failures in the computer room: • Maintain recommended humidity level and airflow rates in the computer room. • 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. • Use a grounded wrist strap (or other grounding method) when handling circuit boards. • Store spare electronic modules in antistatic containers. Acoustics Computer equipment and air conditioning blowers cause computer rooms to be noisy. Ambient noise level in a computer room can be reduced as follows: 24 Chapter 2