82
P/N 133487
Banner Engineering Corp.
•
Minneapolis, U .S .A .
www .bannerengineering .com • Tel: 763 .544 .3164
SC22-3 Safety Controller
Instruction Manual
Appendix A
WARNING . . .
Point-of-Operation Guarding
When properly installed, the two-hand control device
provides protection only for the hands of the machine operator .
It may be necessary to install additional safeguarding, such as
safety light screens and/or hard guards, to protect personnel from
hazardous machinery . Failure to properly guard hazardous
machinery can result in a dangerous condition which could
lead to serious injury or death.
A.5 Two-Hand Control
The Safety Controller may be used as an initiation
device for most powered machinery when machine
cycling is controlled by a machine operator .
Using a two-hand control system makes the operator, in effect, a
“hostage” while the hazard is present, thus limiting or preventing
exposure to the hazard . The two-hand control actuators must be
located so that hazardous motion is completed or stopped before
the operator can release one or both of the buttons and reach
the hazard (see A .5 .1, Separation Distance) .
The SC22-3 safety inputs used to monitor the actuation of the
hand controls for two-hand control comply with the functionality
of Type III requirements of IEC60204-1 and ISO 13851 and
the requirements of ANSI NFPA79 for two-hand control, which
include:
• Concurrent actuation by both hands within a 500 ms time
frame
• Where this time limit is exceeded, both hand controls must
be released before operation is initiated
• Continuous actuation during hazardous condition
• Cessation of hazardous condition if either hand control was
released
• Release and re-actuation of both hand controls to re-initiate
the hazardous motion or condition (i .e ., “anti-tie down”)
• The appropriate performance level of the safety-related
function (e .g ., Control Reliability, Category, or SIL) as
determined by a risk assessment
CAUTION . . .
Hand Controls
The environment in which hand controls are installed
must not adversely affect the means of actuation .
Severe contamination or other environmental influences may cause
slow response or false ON conditions of mechanical or ergonomic
buttons . This may result in exposure to a hazard.
CAUTION . . .
Machine Control Must
Provide Anti-Repeat Control
Appropriate anti-repeat control must be
provided by the machine control and is required by U.S.
and International standards for single-stroke or single cycle
machines.
The level of safety achieved (e .g ., ISO 13849-1 Category)
depend in part on the circuit type selected . See Section A .5 .2 .
The installation of the hand controls must consider:
• Failure modes that would result in a short circuit, a broken
spring(s), mechanical seizure, etc . that would result in not
detecting the release of a hand control
• Severe contamination or other environmental influences
that may cause slow response when released or false
ON condition of the hand control(s), e .g ., sticking of a
mechanical linkage
• Protection from accidental or unintended operation
(e .g ., mounting position, rings, guards or shields)
• Minimizing the possibility of defeat (e .g ., hand controls must
be far enough apart so that they cannot be operated by the
use of one arm — typically, not less than 550 mm (21 .7") in
a straight line, per ISO 13851
• The functional reliability and installation of external logic
devices
• Proper electrical installation per NEC and NFPA79 or
IEC 60204
When used in single-cycle or single-stroke mode, the machine
control must provide an anti-repeat feature so that the operator
must release the two-hand control actuators after each machine
cycle, before a new cycle can be initiated . In addition to the
anti-repeat of the machine control, the SC22-3 safety controller
input(s) can also be used to halt a machine cycle and help in
providing Anti-Repeat Control (see Caution below) .
CAUTION . . .
Install Hand Controls
to Prevent Accidental Actuation
Total protection from defeat of the two-hand control
system is not possible . However, the user is required by OSHA
regulations to arrange and protect hand controls to minimize
possibility of defeat or accidental actuation .
