E-Stop Safety Module
– Models ES-GA-5A and ES-HA-5A
As recommended by the control reliability section of ANSI B11.19, relays K1 and K2 in
the output circuit of the E-Stop Safety Module have mechanically linked contacts which
allow the Safety Module circuitry to monitor the contacts of K1 and K2 for failure. If the
Safety Module detects failure of any contact of the output relays, the Safety Module
output is disabled and cannot be reset.
The E-Stop Safety Module also provides a necessary reset function. ANSI B11 and
NFPA 79 standards require that a reset routine be performed after returning an E-stop
switch to its closed-contact position. This prevents the controlled machinery from
restarting by simply closing the E-stop switch. Model ES-..A-5A may also be configured
for automatic reset (see Figure 2).
The automatic reset mode is useful for some
automated processes. However, when automatic reset is used, an alternate means
must be established to require a reset routine after the E-stop switch is returned to
its closed contact position (see WARNING on page 8).
This E-Stop Safety Module complies with the following design standards:
UL991
Tests for Safety Related Control Employing Solid-State Devices
EN 418
Emergency Stop Equipment - Functional Aspects, Principles for Design
EN 954-1 Safety of Machines: Safety-related Parts of Controllers
Part 1: General Design Directives (Safety Category 4)
The Safety Module has indicators for input power, fault (power supply fault, input cross
short, ground fault) and output relay contact status (K1 and K2); see Figure 1. There
are no adjustments and no user-serviceable parts. See page 11 for information
regarding repair service.
E-Stop Switch Requirements
As shown in Figures 2 and 3, the E-stop switch must provide contacts which are closed
when the switch is in the “armed” position. Once activated, the E-stop switch must
open its contacts and be returned to the closed-contact position
only
by a deliberate
action (such as twisting, pulling, or unlocking). The switch should be a “positive-
opening type,” as described by IEC947-5-1. A mechanical force applied to such a
button (or switch) is transmitted directly to the contacts, forcing them open. This
ensures that the switch contacts will open whenever the switch is activated. NFPA 79
section 13.2, Emergency Stop Devices, specifies the following additional switch (“stop
control”) requirements:
• Emergency Stop push buttons shall be located at each operator control station
and at other operating stations where emergency shutdown shall be required.
• Stop and Emergency Stop push buttons shall be continuously operable from
all control and operating stations where located.
• Actuators of Emergency Stop devices shall be colored RED. The background
immediately around the device actuator shall be colored YELLOW. The
actuator of a push-button-operated device shall be of the palm or mushroom-
head type.
• The Emergency Stop actuator shall be a self-latching type.
NOTE: Some applications may have additional requirements. The user must refer to all
relevant regulations.
WARNING . . .
1-Channel Input
If a 1-channel E-stop button
is used, a single fault (such as a short
across the single E-stop contact or from
the contact to a secondary source of
power) can lead to the complete loss of
safety.
A 1-channel E-stop should be used only
in applications where such a fault can
be excluded, or the resulting loss of
safety cannot result in serious injury or
death
(Safety Category 2, 1 or B; see
page 3).
If a 1-channel E-stop is used, separate
the wires from each other and from
other sources of power, by routing them
through separate wireways or conduit
in order to increase the reliability of the
interface.
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