Monroe Electronics Electrostatic Fieldmeter - Static Monitor - model 177A - Manual (Page 78)

APNE-0016 77
I. Continuous Measurement and Control of Web Static Levels in
Critical Machine Areas
Content
Control of static is not something that occurs once and can then be forgotten. It requires the
implementation of continuous procedures such as charge neutralization using ionizers and electric
field monitoring using permanent fieldmeters to verify that the ionizers are working effectively.
Antistatic measuring and control systems are needed in practice because the conditions for static
elimination always change [1].
This document is the third in a series of three application notes about static charging of materials and
equipment in web converting machines, including recommendations for static measurement, control,
and continuous monitoring. The first document in the series is APNE-0014 Electrostatic Charging In
Web Converting and the second is APNE-0015 Electric Fields and Fieldmeters in Web Converting.
This document provides the reader, working in either hazardous or non-hazardous areas, with the
practical tools necessary to determine where permanent static control devices and Monroe
Electronics Model 1036 fieldmeter probes should be mounted on web converting machines. This
document includes installation and usage instructions for the 1036 probes.
The reader should first attempt to minimize web charging by becoming familiar with Application Note
APNE-0014 Electrostatic Charging In Web Converting before proceeding with the recommendations
in this document.
Machine Grounding Hazard Elimination
The most critical static control item to implement is electrical bonding and grounding of the web-
processing machine. Unless intrinsically connected by virtue of construction (bolted together, gears
with conductive grease, etc.), all conductive
1 parts on or near 2 the machine must be electrically
bonded together [3]. The bonding wires or straps should then be electrically grounded on both sides
of the bonding run to prevent electrical isolation of conductive components in case a bond breaks.
Proper grounding and bonding need to be checked by an electrician at least yearly, and after any
mechanical work is done on the machine.
Machine Part Geometry Hazard Elimination
Be careful to avoid incentive brush discharges
3
from a charged web to conductive machine parts in
hazardous areas due to part geometry. Brush discharges can occur in electric fields measured lower
than 30 kV/cm at the web. These discharges are due to conductive protuberances or corners (e.g.,
those with an edge diameter of less than 10 mm) near the web, which concentrate the field to the 30
kV/cm breakdown strength of air [4].
Determining Locations For Continuous Static Control And Monitoring In
Nonhazardous Areas Using Portable Fieldmeters
To determine where static control devices and permanent static monitoring fieldmeter probes should
be located, portable fieldmeters must first be used to determine the machine locations where fields
are highest and need to be controlled (see APNE-0015 Electric Fields and Fieldmeters In Web
Converting).
Passive and/or active ionizers (see Application Note APNE-0014 Electrostatic Charging In Web
Converting) should be installed at the chosen locations and in the proper manner [3,5]. For high-
speed or difficult-to-control operations, it may be necessary to install multiples of one or both type
ionizers for complete static control.
Permanent fieldmeter probes (Monroe Model1036E or 1036F) then need to be installed downstream
of the static control device(s) in critical locations to monitor their effectiveness.
1
A part is considered conductive if it is metal, or exhibits a volume resistivity less than 10
6
ohmcm [2].
2 A charged web can charge an ungrounded conductor by induction, setting up a spark risk to another
conductor, including a human body.
3
A discharge between a conductor and an insulator that is often characterized by crackling without sparking.