DRAFT - 26 March 2015
SM45-55-SAD Rev 3
32
1 INTRODUCTION
1.1 Application and function
The MTL452x and MTL552x are isolator modules which enable a device located in the hazardous area to be
controlled from the safe area. Some models are simply loop-powered while others have additional input logic
signals to enable power to be supplied to the output. The output current available to the hazardous area is
limited to comply with the requirements of the process explosion hazard. They are also designed and assessed
according to IEC 61508 for use in safety instrumented systems up to SIL2 or in loop-powered variant up to
SIL3 when the required function is to de-energise the output.
When used in a safety instrumented function where the required operation is to energise the output on
demand then a SIL1 rating is achieved for all module types, without hardware redundancy.
The modules can drive a certified intrinsically safe low-power load, such as a solenoid valve or a non-energy-
storing simple apparatus such as an LED lamp.
There are no configuration switches or operator controls to be set on the modules - they perform a fixed
function related to the model selected. Use of the phase-reversal link on the MTL5524 is not recommended in
functional safety applications and has not been considered in this manual.
These modules are members of the MTL4500 and MTL5500 range of products.
1.2 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 1-3, and 4-6) are made through the
removable blue connectors on the top of the modules, but the safe area and power connections for the MTL452x
modules are made through the connector on the base, while the MTL552x uses 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 DIN-rail mounting models.
The solenoid/alarm driver output models covered by this manual are:
MTL4521, MTL4521L, and MTL5521 loop powered, IIC gas group output
MTL5522 loop powered, IIB gas group output
MTL4523, MTL4523R, and MTL5523 powered, with LFD output
MTL4523L loop powered, with LFD output
MTL4523V, MTL4523VL, MTL5523V, MTL5523VL and
MTL4523Y
powered, with LFD output
MTL4524, and MTL5524 powered, two control inputs
MTL4524S powered, switch and voltage controls
MTL4525, and MTL5525 low power output
Note: To avoid repetition, further use of MTLx52x 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 them.
MTL4500 and MTL5500 range
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