Electrostatic Discharge Protected Work Area Grounding Issues

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STORY BY ROBERT DALE TATE, AIR SYSTEMS ELECTROMAGNETIC INTERFERENCE CORRECTIVE ACTION PROGRAM (ASEMICAP) PROGRAM MANAGER, NAVAL AIR SYSTEMS COMMAND

The implementation of a common electrostatic discharge (ESD) program should not be rocket science. Air systems electromagnetic interference corrective action program (ASEMICAP) agrees with that assessment, but like most things, we believe the devil is in the details. In this article we will explore one of the more perplexing details of the ESD protected work area (PWA).

Having public works install a certified hard ground for your ESD PWA is great, but can be costly, especially when in most cases, you have good equipment grounds throughout your spaces that if properly verified, will serve this purpose. Also, the certified hard ground that public works set up requires 24-month verification in accordance with MIL-HDBK-274A. So what is an EMI/ESD program manager supposed to do about grounding?

Figure 1: Common ESD/ordnance grounding point

Figure 1: Common ESD/ordnance grounding point

Grounding should be basic to an ESD program. The Commander Naval Air Forces (CNAF) 4790.2B, Section 10.21.4 lists procedures for the conduct of an ESD program. This naval aviation maintenance program standard operating procedure (NAMPSOP) needs improved, and before we make that happen we decided to first introduce some physical changes (ESD finger cot and ESD PWA earth ground checker) that we believed were needed.

The CNAF 4790.2B Section 10.21.4.2 states “to handle unprotected ESDS items only at ESD PWA that comply with requirements in MIL-HDBK-263B, Naval Air Systems Command (NAVAIR) 01-1A-23, and NAVAIR 17-600-193-6-2.” The MIL-HDBK-263 although still accurate has become is a bit antiquated. The NAVAIR 17-600-193-6-2 will be deleted with the next naval aviation maintenance program (NAMP) change. That leaves the NAVAIR 17-600-193ESD-6-1 the ESD PWA (pre-operational checklist card) and it points to the NAVAIR 01-1A-23 for configuration guidance. The NAVAIR-01-1A-23, work package 004 00, Section 4-4.9 presents grounding in a clean and concise manner. Reading the NAVAIR 01-1A-23, Section 4-4.9, it uses terms such as ESD common point ground (Figure 1), common point ground barrier strip, and others all of which are connected to equipment ground.

That is a key factor because that point is electrically equivalent to ground in your AC outlets. Below are figures 04-23 and 04-24 from the NA 01-1A-23 that point is clearly illustrated. The bottom line is equipment ground is already present throughout all work centers and it is the ground wire of the AC outlet.

Main(s) service equipment single phase. (04-23)

Main(s) service equipment single phase. (04-23)

Typical ground connection and main(s) service equipment.(04-24)

Typical ground connection and main(s) service equipment.(04-24)

The third wire green ground of a common AC outlet in your circuit is equipment ground. I should point out here that I spent four years in the Naval Safety Center and understand that we must be very careful with electrical safety. I am also a trained aircraft electrician and have been in this field for over thirty years. The concern with the third wire green ground is only to prevent personnel from connecting the wrist straps directly to an unverified circuit and I agree that connecting directly to any unverified circuit cannot happen!

However, I am convinced that we can provide the user a device that will allow for the ESD PWA ground in an AC outlet to work safely and doing this will achieve an equipment ground as identified in the NA 01-1A-23 easily. The device I am speaking of is the ESD earth ground checker (Figure 2).

This tester, sold by Static Solutions (P/N SP-101), when connected to an AC outlet will check the outlet for failures and determine if the ground is safe for use (two yellow lights). All that is left to do then is to configure the ESD PWA with a banana plug and connect it to the earth ground checker. No more mystery about ground find an AC outlet use the earth ground checker, plug the ESD PWA into it, and perform a pre-operational check.

Figure 2: The Static Solutions SP-101 plugged-in and indicating “CORRECT” configuration.

Figure 2: The Static Solutions SP-101 plugged-in and indicating “CORRECT” configuration.

Last year ASEMICAP verified this device in many locations. The results were overwhelming favorable that our activities are configured to meet National Electrical Code (NEC). Once briefed by ASEMICAP, CNAF aviation maintenance management team (AMMT) members agreed that this would be the best way forward. This device is designed to be plugged into the AC outlet so it does not constitute plugging directly into ground and if used correctly verifies your ground as functional. If equipment ground is essential to the proper application of the ESD control program then that is exactly what this action will complete.

ASEMICAP recently released a naval message authorizing the use of these devices which was subsequently endorsed by CNAF avionics (160014Z MAY 16). This message is available on our website(https://asemicap.navair.navy.mil).

In the very near future, ASEMICAP will submit a change to the CNAF 4790.2B EMI/ESD NAMPSOP via the AMMT. Once this change is submitted, we will monitor the CH 10.21 for a change that will close this action.

ASEMICAP would like to invite you to visit our ASEMICAP website. It is a 24/7/365 one-stop shop for electromagnetic environmental effects (E3) issues and information.


ONLINE RESOURCES

 Air Systems Electromagnetic Interference Corrective Action Program

https://asemicap.navair.navy.mil

Naval Safety Center

http://www.public.navy.mil/navsafecen/Pages/media/asemicap.aspx

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