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8
SM Surge Rev 2
4.1 EMC
The surge protection devices are designed for operation in normal industrial electromagnetic environment but,
to support good practice, modules should be mounted without being subjected to undue conducted or radiated
interference, see Appendix A for applicable standards and levels.
Any maintenance or other testing activity should only be conducted when the field loop is not in service, to
avoid any possibility of introducing a transient change in the field signal.
4.2 Environmental
The surge protection devices operate over the temperature range from -40°C to +70°C, and at up to 95% non-
condensing relative humidity.
The devices are intended to be mounted in a normal industrial environment without excessive vibration, as
specified for the specific product ranges. See Appendix A for applicable standards and levels.
Continued reliable operation will be assured if the exposure to temperature and vibration are within the
values given in the specification.
5 Installation
There are two particular aspects of safety that must be considered when installing the surge protection devices
and these are:
• Functional safety (applicable when used in SIFs)
• Intrinsic safety (only applicable when used in intrinsic safety loops)
When required, reference must be made to the relevant sections within the instruction sheet or manual
for the product range which contain basic guides for the installation of the interface equipment to meet the
requirements of intrinsic safety. In many countries there are specific codes of practice, together with industry
guidelines, which must also be adhered to.
Provided that these installation requirements are followed then there are no additional factors to meet the
needs of applying the products for functional safety use.
With the exception of the TP models which are designed for field mounting, to guard against the effects of dust
and water the modules should be mounted in an enclosure providing at least IP54 ingress protection rating, or
the location of mounting should provide equivalent protection such as inside an equipment cabinet.
6 Maintenance
To follow the guidelines pertaining to operation and maintenance of intrinsically safe equipment in a
hazardous area, periodic audits of the installation are required by the various codes of practice.
In addition, proof-testing of the instrumented loop operation to conform with functional safety requirements
should be carried out at the intervals determined by safety case assessment.
The continuity of the surge device will be tested (not surge function) when the overall loop function is tested
both during commissioning and through the life of the intended safety function. The removal of the Surge
protective device during these tests is not required.
If an MTL surge protection device 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 Customer
Incident Report (CIR) will be notified 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 made of the normal lifetime for a device of this type which would be in the region of
twenty years, with a typical warranty period of ten years.
