GE GFK-0787B Noise Reduction Machine User Manual


 
B
B-2 Genius Modular Redundancy Flexible Triple Modular Redundant (TMR) System
User’s Manual – March 1995
GFK-0787B
The following table shows common requirements. The differences between solution A
and B are shown by typeface italic.
Requirements for maintenance override handling Responsibility
Already during the software configuration of the PLC
system it is determined in a table or in the application
program, whether the signal is allowed to be overridden.
Project engineer and commissioner
responsible for correct configuration.
The configuration may also specify by a table, whether
simultaneous overriding in independent parts of the ap-
plication is acceptable.
A. Project engineer
B. Project engineer, Type approval
Maintenance overrides are enabled for the whole PLC or
a subsystem (process unit) by the DCS or a hard-wired
switch (e.g. key switch).
A. Operator or Maintenance engineer.
B. Type approval
A. The override is activated via DCS.
B. The maintenance engineer activates the override via the
programming environment.
As an organizational measure, the operator should con-
firm the override condition.
A. Operator, Maintenance engineer
B. Type approval, Maintenance
engineer
Direct overrides on inputs and outputs are not allowed.
Overrides have to be checked and to be implemented in
relation to the application. Multiple overrides in a PLC are
allowed as long as only one override is used in a given
safety related group. The alarm shall not be overridden.
A. Project engineer
B. Project engineer, Type approval
The PLC alerts the operator, e.g. via the DCS, indicating
the override condition. The operator will be warned until
the override is removed.
Project engineer, Commissioner
A. The override is removed via DCS.
B. The maintenance engineer removes the override via the
programming environment.
A. Operator, Maintenance engineer
B. Maintenance engineer
A. There should be a second way to remove the maintenance
overrode condition.
B. If urgent, the maintenance engineer can remove the
override by the hard-wired switch.
A. Project engineer
B. Maintenance engineer, Type
approval
During the time of override proper operational measures
have to be implemented. The time span for overriding
shall be limited to one shift (typically not longer than 8
hours), or hard-wired common maintenance override
switch (MOS) lamps shall be provided on the operator
console (one per PLC or per process unit).
Project engineer, Commissioner, DCS
program, PLC program