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FORTiS-S enclosed encoder system with multiple readheads
3.5 Evaluation unit monitoring
To achieve full system integrity the evaluation unit must continuously monitor the error condition of
each readhead in the FORTiS-S FS encoder system, and in the case of fault detection place the
system into a safe state within the process safety time.
NOTES:
1. The evaluation unit must have its Functional Safety functions enabled (as often it is a
configuration parameter to turn on Functional Safety functionality) and must respond correctly
to a FORTiS-S FS encoder system position error flag.
2. A persistent fault condition may indicate a hardware failure of the FORTiS-S FS encoder
system or an installation problem.
3. The individual readheads must be treated as separate encoder sub-systems. Each readhead
must be connected to a separate evaluation unit and its outputs as per the safety function
and must be monitored separately. In the case of an error being reported then the appropriate
action must be taken.
4. The system manufacturer and/or system installer are responsible for ensuring the safe
operation of these sub-systems: for example, ensuring the readheads do not collide with each
other.
3.6 Maintenance
The maintenance check intervals will be defined by the system manufacturer according to their risk
assessment. There are no user-serviceable parts within the FORTiS-S FS encoder system.
The following maintenance actions are advised:
• Check the extrusion screws and readhead retaining screws are correctly tightened.
• Check for worn or damaged cables and connectors.
• Check the cable connectors are correctly tightened/located.
•
Check the air supply fitting is correctly tightened and the air hose is correctly fitted.
• When the DRIVE-CLiQ interface is used check the retaining screws are correctly tightened.
3.7 Repair
• Repair of the FORTiS-S FS encoder system is only by replacement of parts.
• The replacement parts must have the same part number as the original parts.
• The repaired encoder system must be installed and commissioned in accordance with
• In the event of failure the affected parts should be returned to Renishaw for further analysis.
•
Using damaged parts invalidates the Functional Safety certification.
3.8 Proof testing
It is the responsibility of the system manufacturer to define any proof testing of the system. Due to
the diagnostic coverage (DC) and safe failure fraction (SFF) required to achieve SIL2, the encoder
can only support continuous demand use.
Refer to the
FORTiS-S FS enclosed encoder system Functional Safety installation guide and safety
manual
(Renishaw part no. M-6725-9016) for details of the functional safety certificate and the
EU declaration of conformity.