Fagor QC-PDS - 9.11 Maintenance, Repair and Analysis of Hazardous Events; Mission times; Probabilities of dangerous failure. PFH and MTTFd; Field analysis of hazardous events of the drive

 Functional safety
9.
FUNCTIONAL SAFETY
Maintenance, Repair and Analysis of Hazardous Events
· 318 ·
320
Ref.2003
QC-PDS
HARDWARE
9.11 Maintenance, Repair and Analysis of Hazardous Events
Mission times
Mission time is the period of time covering the intended use of the safety
functions.
Mission time of the STO
The STO circuit includes incorpora solid-state relays and, therefore, its
mission time is independent of the average No. of operations per year (nop)
Its mission time is 20 years.
Mission time of the DRIVE
The mission time of the drive is the mission time of the STO.
Expiration date
After mission time, the safety function will no longer be valid. The expiration
date must be calculated by adding the mission time to the date shown on the
version label of the unit. Write down this value in the maintenance plan of the
installation. Do not use the safety functions after this date.
Probabilities of dangerous failure. PFH and MTTFd
Bear in mind that PFH and MTTFd are theoretical values calculated from
the MTTFd of the components of the circuit and show the probability of
failure. This does not guarantee the mission time of a particular product.
It is impossible to know the instant when a component is going to fail. Only
the probability of a failure to occur is known (PFH or MTTFd). When a
channel fails, the safety function is executed because there are two
channels, but failure accumulation over time that disable it must be
avoided. That's why, the safety functions must be demanded at least at
each STO FORCED TEST INTERVAL and also, after each demand, the external
safety controller must run PLAUSIBILITY CHECK.
Field analysis of hazardous events of the drive
Fagor Automation monitors that field MTTFd are less than the theoretical
ones.
Tools for diagnosis, maintenance and repair in case of failure
 Fault detection in the safety functions
See STO FORCED TEST INTERVAL.
 Conventional error display
- On the CNC monitor.
For further detail, see "man_qc_60_65_err.pdf " CNC manual.
Repair
Neither the user nor the machine manufacturer is authorized to modify or
repair the drive, not even to replace boards.
In the event that any safety function suffers a failure, replace the drive with
a identical model to the model replaced.
Conduct the PARTIAL ACCEPTANCE TEST.