AEC OS Series Gravimetric Batch Blenders - Manual (Page 30)

Page 29 of 118
2-8-3 Fail Safe Operation
If a safety device or circuit should fail, the design must be such that the
failure causes a “Safe” condition. As an example, a safety switch must
be a normally open switch. The switch must be held closed with the
device it is to protect. If the switch fails, it will go to the open condition,
tripping out the safety circuit.
At no time should the safety device fail and allow the operation to
continue. For example, if a safety switch is guarding a motor, and the
safety switch fails, the motor should not be able to run.
2-8-4 Safety Device Lock-Outs
Some safety devices disconnect electrical energy from a circuit. The
safety devices that are utilized on HydReclaim OS/OA models are
primarily concerned with the pneumatics and electrical power
disconnection, and the disabling of moving parts that may need to be
accessed during the normal operation of the machine.
Some of the safety devices utilize a manual activator. This is the method
of initiating the safety lock out. This may be in the form of a plug,
disconnect plug, lever or a handle. Within this lockable handle, there may
be a location for a padlock. Personnel servicing the equipment should
place a padlock in the lockout handle.
WARNING!
Always disconnect and lockout all electrical power and pneumatic
(i.e. compressed air) sources prior to servicing or cleaning any
HydReclaim blender, including all OS/OA units. Failure to do so
may result in serious injury.
At no time must anyone remove the lockout or reconnect the twist
plug, other than the person who installed the lockout or who
unplugged the twist plug.