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.
This Banner device can be used to assist in accomplishing anti-repeat control, but a risk assessment
must be accomplished to determine the suitability of such use.
Two-Hand Control Safety Distance (Minimum Distance)
The hand controls operator must not be able to reach the hazardous area with a hand or any other body part before the
machine motion ceases. Use the formula below to calculate the safety distance (minimum distance).
WARNING: Location of Touch Button Controls
Hand controls must be mounted a safe distance from moving machine parts, as determined
by the appropriate standard. It must not be possible for the operator or other non-qualified persons
to relocate them. Failure to establish and maintain the required safety distance may result in
serious injury or death.
U.S. Applications
The Safety Distance formula, as provided in ANSI B11.19:
Part-Revolution Clutch Machinery (the machine and its controls allow the machine to stop motion during the hazardous portion of the machine
cycle)
Ds = K x (Ts + Tr + Th)
For Full-Revolution Clutch Machinery (the machine and its controls are designed to complete a full machine cycle)
Ds = K x (Tm + Tr + Th)
Ds
the Safety Distance (in inches)
K
the OSHA/ANSI recommended hand-speed constant (in inches per second), in most cases is calculated at 63 in/sec, but may vary between 63
in/sec to 100 in/sec based on the application circumstances;
not a conclusive determination; consider all factors, including the physical ability of the operator, when determining the value of K to be used
Th
the response time of the slowest hand control from the time when a hand disengages that control until the switch opens;
Th is usually insignificant for purely mechanical switches. However, Th should be considered for safety distance calculation when using
electronic or electromechanical (powered) hand controls. For Banner Self-checking Touch Buttons (STBs) the response time is 0.02 seconds
Tm
the maximum time (in seconds) the machine takes to cease all motion after it has been tripped. For full revolution clutch presses with only one
engaging point, Tm is equal to the time necessary for one and one-half revolutions of the crankshaft. For full revolution clutch presses with
more than one engaging point, Tm is be calculated as follows:
Tm = (1/2 + 1/N) x Tcy
N = number of clutch engaging points per revolution
Tcy = time (in seconds) necessary to complete one revolution of the crankshaft
Tr
the response time of the Safety Controller as measured from the time a stop signal from either hand control. The Safety Controller response
time is obtained from the Configuration Summary in the PC Interface.
Ts
the overall stop time of the machine (in seconds) from the initial stop signal to the final ceasing of all motion, including stop times of all
relevant control elements and measured at maximum machine velocity
Ts is usually measured by a stop-time measuring device. If the specified machine stop time is used, add at least 20% as a safety factor to
account for brake system deterioration. If the stop-time of the two redundant machine control elements is unequal, the slower of the two times
must be used for calculating the separation distance
European Applications
The Minimum Distance Formula, as provided in ISO 13855:
S = (K x T) + C
XS/SC26-2 Safety Controller
76
