Large Arrivals Of Single Channel Isolator Modules MTL 4531

Large Arrivals Of Single Channel Isolator Modules MTL 4531

Large Arrivals Of Single Channel Isolator Modules MTL 4531

1.1 Application and function
The MTL4531 and MTL5531 are single channel isolator modules which enable vibration sensors and
probes located in a hazardous area to be connected to monitoring systems in the safe area. For resistance
temperature detectors, rtds, the MTL4582B and MTL5582B module is a single channel isolator module
that repeats the resistance value from hazardous to safe area. The modules are also designed and assessed
according to IEC 61508 for use in safety instrumented systems up to SIL1, without hardware redundancy.
Higher integrity levels for a SIF can be achieved by hardware duplication, for example by using the modules in
a voting architecture.

Large Arrivals Of Single Channel Isolator Modules MTL 4531
The vibration modules are compatible with three-wire eddy-current probes and accelerometers or two-wire
current sensors. The RTD isolator is compatible with two, three or four-wire devices. There are configuration
switches to be set on the modules that define the type and arrangement of the connected sensors.
These modules are members of the MTL4500 and MTL5500 range of products.

2 System configuration
An MTLx531 or MTLx582B module may be used in a single-channel (1oo1) safety instrumented function up to
SIL1 where the safe state is the output de-energised. Higher integrity levels for a SIF can be realised through
duplication of the function. The worked example in this manual is for a SIL1 application.
The figures below show the system configuration and specifies the interfaces to the safety related and non
safety-related system components. It does not aim to show all details of the internal module structure, but is
intended to support understanding for the application.

3 Selection of product and implications
For the MTLx531 modules there is only one function - to repeat the signal voltage and frequency from a
vibration sensor, powered through the module, into the input channel of a vibration monitoring system.
This may be used within a safety function, with power off as the safe state. The input modules of the vibration
monitoring system must be able to diagnose when the signal voltage is outside of the expected measuring
range and take appropriate action to declare the signal as ‘bad’.
This is considering the hardware failure rate only and the user must consider the systematic implications
of applying this equipment in safety functions where a number of safety-related subsystem channels are
implemented to achieve the requisite hardware fault tolerance.
Large Arrivals Of Single Channel Isolator Modules MTL 4531
4 Assessment of functional safety
The design features and the techniques/measures used to prevent systematic faults are suitable for the use
of the MTLx531 and MTLx582B modules in safety functions up to SIL1 where the safe state of the loop is
with the output de-energised.
It is assumed that the module is powered from a nominal 24Vdc supply. The product has been assumed to
operate at a maximum ambient temperature of 45°C under normal conditions.

5 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

6 Maintenance
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.
7 Appendices
The MTL4531 and MTL5531 are single channel isolator modules which enable vibration sensors and
probes located in a hazardous area to be connected to monitoring systems in the safe area. For resistance
temperature detectors, rtds, the MTL5582 module is a single channel isolator module that repeats the
resistance value from hazardous to safe area. The modules are also designed and assessed according to IEC
61508 for use in safety instrumented systems up to SIL1.