Typical accidents have included the
following:
• A robot’s arm functioned erratically
during a programming sequence and
struck the operator.
• A materials handling robot operator
entered a robot’s work envelope during
operations and was pinned between
the back end of the robot and
a safety pole.
• A fellow employee accidentally
tripped the power switch while a
maintenance worker was servicing an
assembly robot. The robot’s arm
struck the maintenance worker’s hand.
The proper selection of an effective robotic safeguarding system should be
based upon a hazard analysis of the robot
system’s use, programming, and
maintenance operations.
For the planning stage, installation,
and subsequent operation of a robot or
robot system, one should consider the
following safety guidelines from an
OSHA technical manual titled “Industrial
Robots and Robot System Safety.”
Risk Assessment: At each stage of development
of the robot and robot system
a risk assessment should be performed.
There are different system and personnel
safeguarding requirements at each
stage. The appropriate level of safeguarding
determined by the risk assessment
should be applied. In addition, the
risk assessments for each stage of development
should be documented for future
reference.
Safeguarding Devices: Personnel
should be safeguarded from hazards associated
with the restricted envelope
(space) through the use of one or more
safeguarding devices:
• Mechanical limiting devices;
• Nonmechanical limiting devices;
• Presence-sensing safeguarding devices;
• Fixed barriers (which prevent contact
with moving parts); and
• Interlocked barrier guards.
Awareness Devices: Typical awareness
devices include chain or rope barriers
with supporting stanchions or
flashing lights, signs, whistles, and
horns. They are usually used in conjunction
with other safeguarding devices.
Safeguarding the Teacher: Special consideration
must be given to the teacher or
person who is programming the robot.
During the teach mode of operation, the
person performing the teaching has control
of the robot and associated equipment
and should be familiar with the operations
to be programmed, system interfacing,
and control functions of the robot and
other equipment.
When systems are large and complex,
it can be easy to activate improper functions
or sequence functions improperly.
Since the person doing the training can
be within the robot’s restricted envelope,
such mistakes can result in accidents.
Mistakes in programming can result in
unintended movement or actions with
similar results. For this reason, a restricted
speed of 250 mm/§ or 10 in/§
should be placed on any part of the robot
during training to minimize potential
injuries to teaching personnel.
Several other safeguards are suggested in the ANSI/RIA R15.06-1992
standard to reduce the hazards associated
with teaching a robotic system.
Operator Safeguards: The system operator
should be protected from all hazards
during operations performed by the
robot. When the robot is operating automatically,
all safeguarding devices
should be activated, and at no time
should any part of the operator’s body be within
the robot’s safeguarded area.
For additional operator safeguarding suggestions,
see the ANSI/RIA R15.06-1992
standard, Section 6.6.
Attended Continuous Operation:
When a person is permitted to be in or
near the robots restricted envelope to
evaluate or check the robots motion or
other operations, all continuous operation
safeguards must be in force. During this operation, the robot should be at
slow speed, and the operator would have
the robot in the teach mode and be fully
in control of all operations.
Other safeguarding requirements are
suggested in the ANSI/RIA R15.06-
1992 standard, Section 6.7.
Maintenance and Repair Personnel:
Safeguarding maintenance and repair
personnel is very difficult because their job functions are so varied. Troubleshooting
faults or problems with the
robot, controller, tooling, or other associated
equipment is just part of their job.
Program touchup is another of their jobs
as is scheduled maintenance, and adjustments
of tooling, gauges, recalibration,
and many other types of functions.
While maintenance and repair is being
performed, the robot should be placed in the manual or teach mode, and the maintenance
personnel perform their work
within the safeguarded area and within the
robot’s restricted envelope. Additional hazards
are present during this mode of operation
because the robot system safeguards
are not operative.
To protect maintenance and repair personnel,
safeguarding techniques and procedures
as stated in the ANSI/RIA
R15.06-1992 standard, Section 6.8, are
recommended.
Maintenance: Should occur during the
regular and periodic inspection program
for a robot or robot system. An inspection
program should include, but not be
limited to, the recommendations of the
robot manufacturer and manufacturer of
other associated robot system equipment
such as conveyor mechanisms, parts feeders,
tooling, gauges, sensors, and the like.
These recommended inspection and
maintenance programs are essential for
minimizing the hazards from component
malfunction, breakage, and unpredicted
movements or actions by the robot or
other system equipment. To ensure
proper maintenance, it is recommended
that periodic maintenance and inspections
be documented along with the identity of
personnel performing these tasks.
Safety Training: Personnel who program,
operate, maintain, or repair robots or
robot systems should receive adequate safety
training, and they should be able to demonstrate
their competence to perform their jobs
safely. Employers can refer to OSHA’s publication
2254 (Revised), “Training Requirements
in OSHA Standards and Training
Guidelines.”
General Requirements: To ensure
minimum safe operating practices and
safeguards for robots and robot systems
covered by this instruction, the following
sections of the ANSI/RIA R15.06-
1992 must also be considered:
• Section 6 - Safeguarding Personnel;
• Section 7 - Maintenance of Robots and
Robot Systems;
• Section 8 - Testing and Start-up of
Robots and Robot Systems; and
• Section 9 - Safety Training of Personnel.
Robots or robotic systems must comply
with the following regulations: Occupational
Safety and Health Administration,
OSHA 29 CFR 1910.333, Selection and
Use of Work Practices, and OSHA 29 CFR
Part 1910.147, The Control of Hazardous
Energy (Lockout/Tagout).
