ESD Systems - Questions And Answers

Can Field Service personnel ground themselves by holding a grounded pole while working with ESD susceptible items and not have to use personal grounding items such as a Wrist Strap?

No, and not be in compliance with ANSI/ESD S20.20. ESD susceptible item Field Service work requires a temporary ESD Protected Area where all S20.20 requirements should be met.

Most important is the safety of the worker. Directly grounding personnel can be a safety hazard and is not approved by either OSHA or Underwriters Laboratory without at a minimum one megohm resistor in series with the human body. Per S1.1-1998 paragraph 7.1 Construction Guidelines Current-Limiting Resistance “A resistance of sufficient resistance to limit current to less than 0.0005 amps (O.5mA), at the highest voltage that may be encountered, should be incorporated into the wrist strap.” The argument that “I am not wearing a Wrist Strap” so I don’t need the current limiting resistor” is not persuasive.

The worker’s hand in contact with a grounded pole would not comply with S20.20 paragraph 6.2.1.1. Grounding / Bonding Systems Requirement that “Grounding/Bonding Systems shall be used to ensure that ESDS items, personnel and any other conductors (e.g. mobile equipment) are at the same electrical potential. As a minimum, ESDS items, personnel and other related conductors shall be bonded or electrically interconnected.” Paragraph 6.2.1.2. Grounding / Bonding Systems Guidance states “When the third wire AC equipment ground is not available or impractical to use, personnel should be bonded or electrically connected to a conductive element of the ESDS item using a wrist strap or other grounding system to ensure that all elements are at the same electrical potential.”

A fundamental ESD control principles that form the basis of S20.20 is: “All conductors in the environment, including personnel, must be bonded or electrically connected and attached to a known ground or contrived ground (as on shipboard or on aircraft). This attachment creates an equipotential balance between all items and personnel. Electrostatic protection can be maintained at a potential above a “zero” voltage ground potential as long as all items in the system are at the same potential.”

Per Paragraph 6.2. ESD CONTROL PROGRAM PLAN TECHNICAL REQUIREMENTS “Area 2 shown on Table 1 is intended to designate temporary ESD controlled areas such as field service or other remote locations that are not normally equipped as a Protected Area. Test methods used by the organization that differ from the test method or reference in Table 1 shall be documented.”

Per Paragraph 6.2.2.2 Personnel Grounding Guidance “The personnel grounding system in all cases includes the person, the control item(s) and connection to ground… When equipment ground or auxiliary ground systems are not available, bonding or electrical connections (contrived ground) may be used.”

Per Paragraph 6.2.3.1. Protected Areas Requirement “Handling of ESDS parts, assemblies and equipment without ESD protective covering or packaging shall be performed in a Protected Area.”

Per Paragraph 6.2.3.2. Protected Areas Guidance “A Protected Area may be a single workstation (fixed or portable).”

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