Banner EZ-SCREEN­ Safety Light Curtain Systems - Manual (Page 20)

18
P/N 68413 rev. A
Banner Engineering Corp. • Minneapolis, U.S.A.
www.bannerengineering.com • Tel: 763.544.3164
EZ-SCREEN Point
Instruction Manual
System Installation
Figure 3-4. Separation distance
3.3.2 Minimum Separation Distance (Ds)
Minimum Separation (Safety) Distance (Ds) is the minimum
distance required between the light beam(s) and the closest
reachable hazard point . Separation distance is calculated so
that the EZ-SCREEN Point System will send a stop signal to the
machine when an object or a person is detected (by blocking a
sensing beam), allowing the machine to come to a stop by the
time the person can reach any machine hazard point .
After the Ds is determined, record the calculated distance
in Section 6.4 (step 2) of this manual, and/or on the Daily
Checkout Card.
Ds
Ds
Ds
Hazard
Calculation of separation distance takes into account several
factors, including a calculated human speed, the total system
stopping time (which itself has several components), and
the depth penetration factor . The formula used to calculate
separation distance is:
Ds = K
x
(Ts + Tr) + Dpf
where:
Ds = the separation distance, in inches;
K = 63" per second (or 1600 mm per second), the OSHA-
recommended (or EN 999-recommended) hand-speed
constant 1 ;
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) 2 . See
the Warnings on page 22, and the Notice Regarding
MPCEs (at left).
This measurement must take into account the slower of the
two MPCE channels, and the response time of all devices
or controls (such as interface modules) that react to stop
the machine. If all devices are not included, the calculated
separation distance (Ds) will be too short and serious injury
could result .
Tr = 0.024 seconds, the maximum response time of the
EZ-SCREEN Point System; and
Dpf = 48", the added distance due to depth penetration
factor (for U.S. 2-beam applications, prescribed in
ANSI/RIA R15.06 and ANSI B11). See warnings
regarding beam spacing in Section 3 .4 .
In European 2-beam applications, Dpf is 850 mm,
prescribed in EN 999.
NOTES:
1. The OSHA-recommended hand speed constant K has been
determined by various studies, and although these studies
indicate speeds of 63"/second to more than 100"/second, they
are not conclusive determinations. The user should consider
all factors, including the physical ability of the operator, when
determining the value of K to be used.
2 . Ts is usually measured by a stop-time measuring device. If
the machine manufacturer’s specified stop time is used, at
least 20% should be added to allow for possible clutch/brake
system deterioration .3 .3 .3 Supplemental Safeguarding
Figure 3-5. Reach over hazard
Reaching Over
Beam 1
Beam 2
Notice Regarding MPCEs
Each of the two Machine Primary Control Elements (MPCE 1 and
MPCE2) must be capable of immediately stopping the dangerous
machine motion, irrespective of the state of the other. These two
channels of machine control need not be identical, but the stop time
performance of the machine (Ts, used to calculate the separation
distance) must take into account the slower of the two channels.