Archives

• AS-i bus wiring for the process industry environment

• SpurGuard™ short circuit protection with visual fault detection

• Plug-in connectors for fast commissioning and maintenance

• Choice of junction box to meet site requirements

• Power LED

AS-i Megablocks are DIN-rail mounted passive* hubs for the AS-i

network. They connect several AS-i devices to the network trunk

cable and provide short circuit and over voltage to the segment. The

AS–i Megablock itself does not contain an AS–i chip or communicate

over the AS–i network, so it consumes no network communication

resources (bandwidth, slave addresses, etc.). They are used to

interconnect AS–i master and slave devices that do contain AS–i chips.

Megablocks minimize hand wiring and allow individual devices to be

added to and removed from the segment without disrupting network

communication. A green power LED on each unit indicates whether

DC power is present. Megablocks are available in four and eight drop

versions. Multiple Megablocks are easily wired to one another to allow

larger segments to be constructed.

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.

Installation

There are two particular aspects of safety that must be considered when installing the MTL4500 or

MTL5500 modules and these are:

• Functional safety

• Intrinsic safety

Reference must be made to the relevant sections within the instruction manual for MTL4500 range

(INM4500)or MTL5500 range (INM5500) 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.

To guard against the effects of dust and water the modules should be mounted in an enclosure providing

atlea st IP54 protection degree, or the location of mounting should provide equivalent protection such as

inside an equipment cabinet.

In applications using MTL4500 range, where the environment has a high humidity, the mounting

backplanes should be specified to include conformal coating.

Installation

There are two particular aspects of safety that must be considered when installing the MTL4500 or

MTL5500 modules and these are:

• Functional safety

• Intrinsic safety

Reference must be made to the relevant sections within the instruction manual for MTL4500 range

(INM4500) or MTL5500 range (INM5500) 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.

To guard against the effects of dust and water the modules should be mounted in an enclosure providing

at least IP54 protection degree, or the location of mounting should provide equivalent protection such as

inside an equipment cabinet.

In applications using MTL4500 range, where the environment has a high humidity, the mounting

backplanes should be specified to include conformal coating.

Variant Description

Functionally the MTL4500 and MTL5500 range of modules are the same but differ in the following way:

– the MTL4500 modules are designed for backplane mounted applications

– the MTL5500 modules are designed for DIN-rail mounting.

In both models the hazardous area field-wiring connections (terminals 1.2. and optionally 4.5) are made through

the removable blue connectors, but the safe area and power connections for the MTL454xA/MTL454xAS

modules are made through the connector on the base, while the MTL554xA/MTL554xAS modules use the

removable grey connectors on the top and side of the module.

Note that the safe-area connection terminal numbers differ between the backplane and the DIN-rail

mounting models.

Note: To avoid repetition, further use of MTLx54xA and MTLx54xAS in this document can be understood to

include both DIN-rail and backplane models. Individual model numbers will be used only where there is a need

to distinguish between them.

All the module types described in this manual have the same connectivity for the field signals, supporting

4-wire process transmitters or currents sourced in the hazardous area. The connection of the repeated current

signals into the input measurement channels for the safety logic system follows the arrangement shown in the

following diagram. When the input channels of the Safety Instrumented System (SIS) are providing power for

the loop, the ‘S’ variants of the isolator modules are used to ‘sink’ the measuring current.

In the other cases the isolator modules ‘source’ the measuring current that flows into a load resistor inside the

input card of the Safety Instrumented System.

INTRODUCTION

Application and function

The Analogue Input module types MTLx541A/MTLx541AS (single channel) and MTLx544A/MTLx544AS

(dual channel) are intrinsic safety isolators that interface with process measurement transmitters located

in a hazardous area of a process plant. They are also designed and assessed according to IEC 61508 for

use in safety instrumented systems up to SIL 2.

The MTLx541A provides an input for a separately-powered 4/20mA transmitter located in a hazardous

area, and repeats the transmitter current into a load in the safe area. The MTLx544A supports two

identical channels for use with two separate transmitters. The MTLx541AS and MTLx544AS versions act as

a current sink for the safe area connection rather than driving the current into the load.

All the modules allow bi–directional transmission of HART communication signals superimposed on the

4/20mA loop current, so that the transmitter can be interrogated either from the operator station or by a

hand held communicator (HHC).

There are no configuration switches or operator controls to be set on the modules. These modules are

members of the MTL4500 and MTL5500 range of products.