Eaton MTL

MTL Instruments Group

FAQ - Environmental -

FAQ - Environmental


What does G3/G2 mean?

A G2 and G3 are corrosion resistance classifications within the ISA standard S71.04. The ‘G’ denotes attack by gaseous air-borne pollutants and the number the level of contamination.

G2 is defined by the standard as: “Moderate - An environment in which the effects of corrosion are measurable and may be a factor in determining equipment reliability”.

G3 is defined by the standard as: “Harsh - An environment in which there is a high probability that corrosive attack will occur. These harsh levels should prompt further evaluation resulting in environmental controls or specially designed and packaged equipment."

MTL8000 is designed for use in G3 environments providing the installation instructions are followed carefully.
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What degree of corrosion resistance can the MTL8000 equipment withstand

A An indication of this can be achieved by exposure of the MTL8000 to Ammonia gas. The ISA G3 corrosion test included exposure to ammonia at a concentration of 25 parts per million for a continuous period of 30 days.

The MTL8000 equipment achieved the G3 rating, as can be scrutinised by reference to the testing carried out by the British Standards Institute. Note that the testing was done without the equipment being mounted in an enclosure (ie, direct pollution of the modules and carriers). Hence, this is equivalent to a much longer installed lifetime within a cabinet, with occasional exposure to the gas due to opening of the enclosure door, or seepage at lower concentration into the enclosure.
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Why should I use MTL8000 instead of a PLC and remote I/O?


It has been well proven in factory automation that mounting the PLC I/O close to the process reduces installed cost. It has not been possible for the Process industries to enjoy that same level of installed cost reduction because PLC I/O does not provide the necessary capability. It does not provide the environmental performance or the functional specifications, nor does it provide for hazardous areas installation & interface to standard Process Industry Smart instrumentation (such as HART transmitters).

MTL8000 is designed specifically for the Process Industry :

  • flexibility for use in safe areas.
  • Division or Zone 2 location, with Intrinsic Safety an integral part of the system.
  • wide operating ambient temperature range : -40°C to +70° C.
  • resistance to corrosive gases : G3 Corrosion Resistance spec ISA SP71.04.
  • shock & vibration specification to EN 60068.
  • functional specifications & extensive diagnostics to channel level.
  • interfacing to Smart HART transmitters.
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Is the -40°C to +70°C valid for horizontal and vertical mounting ?

A The full -40°C to +70°C specified operating ambient range is achieved when the Carrier is mounted
horizontally, with the Field Terminals below the I/O Modules.

When the Carrier is mounted vertically, with the Field Terminals to either side of the I/O Modules, the operating ambient range is -40°C to +55°C
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Can the MTL8000 2/x system be used in areas with dust hazards ?

A The MTL8000 has been designed in accordance with the ATEX directives 94/9/EC (Apparatus Directive 100a) for installation within gas groups in acordance with directive 1999/92/EC (Workplace Directive 137). It is not marked for dust hazards (D) although it is possible to comply with the appropriate directives by evaluating the dust in question and the specific application.

A generic letter is attached, for use within any ATEX compliant region, for any application that focuses on dust hazards, and demonstrates how MTL8000 may be located in Zone 22 without further certification (equivalent to Zone 2 for gases). The hardware would be supplied by MTL with an appropriate letter detailing compliance.

MTL would have to quote a documentation charge in line with the work required to complete any evaluation. It is suggested that any request for quotation for dust applications is passed to the MTL8000 Product Manager to obtain an appropriate charge.

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