To follow the guidelines pertaining to operation and maintenance of intrinsically safe equipment in a

hazardous area, yearly periodic audits of the installation are required by the various codes of practice. In

addition, proof testing of the loop operation to conform with functional safety requirements should be

carried out at the intervals determined by safety case assessment.

Proof testing must be carried out according to the application requirements, but it is recommended that

this be carried out at least once every three years.

Refer to Appendix B for the proof testing procedure of the MTLx541A/AS and MTLx544A/AS modules.

Note that there may also be specific requirements laid down in the E/E/PE operational maintenance

procedure for the complete installation.

If an MTLx541A/AS and MTLx544A/AS module is found to be faulty during commissioning or during the

normal lifetime of the product, then such failures should be reported to the local MTL office. When

appropriate, a Cus tomer Incident Report (CIR) will be notified by Eaton to enable the return of the unit to

the factory for analysis. If the unit is within the warranty period then a replacement unit will be sent.

Consideration should be given to the service lifetime for a device of this type, which is in the region of ten

years. Operating an MTLx541A/AS and MTLx544A/AS module for longer than this period could invalidate

the functional safety analysis, meaning that the overall safety function no longer meets its target SIL. If

high failure rates of the MTL modules are detected, indicating that they have entered the ‘end of life

phase’ of their service life, then they should be replaced promptly.