standards and guidelines for communication sites - Radio And ...
standards and guidelines for communication sites - Radio And ... standards and guidelines for communication sites - Radio And ...
MEASURES FOR CONTROLLING ELECTROSTATIC DISCHARGE APPENDIX C: PROTECTING AGAINST ELECTROSTATIC DISCHARGE IN EQUIPMENT ROOMS AND DISPATCH CENTERS C.3 MEASURES FOR CONTROLLING ELECTROSTATIC DISCHARGE C.3.1 WRIST-STRAPS Depending on the environment and mobility requirements of personnel, there are several ways to address ESD concerns. The least costly ways are more restrictive to personnel mobility and require more focus on properly established and institutionalized operating procedures (such as wrist-straps); these means will not help to eliminate the occurrence of ESD, but will help to dissipate the electrostatic charge from the person's body and keep it from entering the communications system equipment. There are many strategies for minimizing ESD events. The following sections provide some options, but are not all-inclusive. As a rule, not all of these techniques will be either necessary or desirable to establish an ESD protected area. The appropriate ESD protection strategy should be based on the particular application and the advantages and disadvantages of each ESD protective method. (ANSI T1.321-R2000, section 4) Personnel can be equipped with ESD-rated wrist-straps. The person connects the wrist-strap to an effectively grounded jack before connecting to the headset jack or touching equipment or grounded objects. The wrist-strap shall provide dissipative resistance values and other safety measures as described within ANSI/ESD S1.1-1998 or later. C.3.2 RELATIVE HUMIDITY CONTROL Control of the relative humidity can be an effective means for helping control ESD occurrences because higher relative humidity aids in static dissipation and is associated with lowered triboelectric charging. Rooms containing network operator positions (dispatch centers) should maintain a relative humidity within the range of 40 to 55 percent (ANSI T1.321-R2000). When the humidity drops below 40 percent, ESD events are more likely to occur. If humidity is kept above 55 percent, electrolytic corrosion may affect equipment performance and microbial contamination may occur (ANSI T1.321-R2000). Table C-1lists typical voltage levels at different relative humidity levels. The table and additional information on ESD control can be found on the Electrostatic Discharge Association web site http://www.esda.org. TABLE C-1 EXAMPLES OF STATIC GENERATION TYPICAL VOLTAGE LEVELS Means of Generation 10-25% RH 65-90% RH Walking across carpet 35,000 Volts 1,500 Volts Walking across vinyl tile 12,000 Volts 250 Volts Worker at bench 6,000 Volts 100 Volts Poly bag picked up from bench 20,000 Volts 1,200 Volts Chair with urethane foam 18,000 Volts 1,500 Volts C-2 68P81089E50-B 9/1/05
STANDARDS AND GUIDELINES FOR COMMUNICATION SITES MEASURES FOR CONTROLLING ELECTROSTATIC DISCHARGE C.3.3 FLOORING C.3.4 CHAIRS Carpeting or floor tiles within an equipment room or dispatch center, including raised flooring, should have a resistance to ground measurement of between 10 6 and 10 9 ohms when measured using the test method of ANSI/ESD STM7.1-2001 or later. Existing flooring that does not meet this requirement should be treated with a topical solution such as an antistatic floor wax or spray solution. The effectiveness of antistatic solutions is temporary and varies with floor material and relative humidity. Flooring resistance should be monitored every two weeks minimum to verify conformance to the above requirements. (ANSI T1.321-R2000, section 4.2 and ANSI/ESD STM7.1-2001) When ESD protective flooring is used, the following should be observed: • ESD protective flooring should be installed per the manufacturer's recommendations. • ESD protective flooring and floor coverings should be installed, grounded, and tested by trained installers. • Personnel entering the equipment room or dispatch area should wear ESD dissipative footwear or dissipative foot straps. The footwear should provide dissipative resistance values of less than 35 × 106 ohms as measured according to the measuring requirements within ANSI/ESD STM97.1- 1999 or later. The footwear should also provide dissipative resistance values of less than 1.0 × 10 9 ohms as measured in accordance with the measuring requirements of ANSI/ESD STM9.1-2001 or later. When ESD protective flooring is not installed at a dispatch position or equipment room, an ESD protective floor mat should be installed at the work areas. When ESD protective floor mats are installed, the following should be observed: • The floor mat should provide dissipative resistance values between 106 and 109 ohms when measured using the test method of ANSI/ESD STM7.1-2001 or later. • The floor mat should be effectively bonded to the common grounding point. • Personnel should wear ESD dissipative footwear or dissipative foot straps. The footwear should provide dissipative resistance values of less than 35 × 10 6 ohms as measured according to the measuring requirements within ANSI/ESD STM97.1-1999 or later. The footwear should also provide dissipative resistance values of less than 1.0 × 109 ohms as measured in accordance with the measuring requirements of ANSI/ESD STM9.1-2001 or later. • Personnel should stand on the floor mat before connecting to the headset jack or touching equipment or grounded objects. Chairs used in dispatch centers should be ESD protective and have a resistance to ground measurement of between 10 5 and 10 9 ohms when measured using the test method of ANSI/ESD STM12.1-1997 or later. Such chairs operate in conjunction with ESD protective flooring (see previous paragraph). (ANSI T1.321-R2000, section 4.3 and ANSI/ESD STM12.1-1997) ESD protective chairs should incorporate a continuous path between all chair elements and the ground point. The ground point of a static dissipative chair should be the static dissipative chain or the conductive casters that provide electrical continuity to the ESD flooring material. (See FAA-STD-019d- 2002 for additional information.) 68P81089E50-B 9/1/05 C-3
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MEASURES FOR CONTROLLING ELECTROSTATIC DISCHARGE APPENDIX C: PROTECTING AGAINST ELECTROSTATIC DISCHARGE IN EQUIPMENT ROOMS<br />
AND DISPATCH CENTERS<br />
C.3 MEASURES FOR CONTROLLING ELECTROSTATIC DISCHARGE<br />
C.3.1 WRIST-STRAPS<br />
Depending on the environment <strong>and</strong> mobility requirements of personnel, there are several ways to<br />
address ESD concerns. The least costly ways are more restrictive to personnel mobility <strong>and</strong> require<br />
more focus on properly established <strong>and</strong> institutionalized operating procedures (such as wrist-straps);<br />
these means will not help to eliminate the occurrence of ESD, but will help to dissipate the electrostatic<br />
charge from the person's body <strong>and</strong> keep it from entering the <strong>communication</strong>s system equipment.<br />
There are many strategies <strong>for</strong> minimizing ESD events. The following sections provide some options,<br />
but are not all-inclusive. As a rule, not all of these techniques will be either necessary or desirable to<br />
establish an ESD protected area. The appropriate ESD protection strategy should be based on the<br />
particular application <strong>and</strong> the advantages <strong>and</strong> disadvantages of each ESD protective method. (ANSI<br />
T1.321-R2000, section 4)<br />
Personnel can be equipped with ESD-rated wrist-straps. The person connects the wrist-strap to an<br />
effectively grounded jack be<strong>for</strong>e connecting to the headset jack or touching equipment or grounded<br />
objects. The wrist-strap shall provide dissipative resistance values <strong>and</strong> other safety measures as<br />
described within ANSI/ESD S1.1-1998 or later.<br />
C.3.2 RELATIVE HUMIDITY CONTROL<br />
Control of the relative humidity can be an effective means <strong>for</strong> helping control ESD occurrences because<br />
higher relative humidity aids in static dissipation <strong>and</strong> is associated with lowered triboelectric charging.<br />
Rooms containing network operator positions (dispatch centers) should maintain a relative humidity<br />
within the range of 40 to 55 percent (ANSI T1.321-R2000). When the humidity drops below 40 percent,<br />
ESD events are more likely to occur. If humidity is kept above 55 percent, electrolytic corrosion may<br />
affect equipment per<strong>for</strong>mance <strong>and</strong> microbial contamination may occur (ANSI T1.321-R2000).<br />
Table C-1lists typical voltage levels at different relative humidity levels. The table <strong>and</strong> additional<br />
in<strong>for</strong>mation on ESD control can be found on the Electrostatic Discharge Association web site<br />
http://www.esda.org.<br />
TABLE C-1 EXAMPLES OF STATIC GENERATION TYPICAL VOLTAGE LEVELS<br />
Means of Generation 10-25% RH 65-90% RH<br />
Walking across carpet 35,000 Volts 1,500 Volts<br />
Walking across vinyl tile 12,000 Volts 250 Volts<br />
Worker at bench 6,000 Volts 100 Volts<br />
Poly bag picked up from bench 20,000 Volts 1,200 Volts<br />
Chair with urethane foam 18,000 Volts 1,500 Volts<br />
C-2 68P81089E50-B 9/1/05
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