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INTRINSICALLY SAFE INSTRUMENTS AND ITS HELP IN MINIMIZING RISKS IN HAZARDOUS LOCATIONS

Intrinsic Safety – the basics
The term “Intrinsically Safe” (I
...
) is frequently used to describe any product destined for
an explosive area
...
S
...
A typical fixed
I
...
circuit would comprise a device such as a temperature sensor permanently located
within the explosive area, which is in turn protected by a safety barrier located in the safe
area
...

Interestingly, the inclusion of a barrier in the control loop does not allow any device to
be connected downstream
...

Intrinsic safety (IS) is a concept that is used to prevent electrical equipment from causing
explosions in hazardous environments
...
Electrical
equipment has the potential of igniting these mixtures if sparks or high temperatures are
generated during the operation of the equipment
...

Electricity In Hazardous Areas
Using electricity in potentially explosive areas has been a concern since the beginning
of the twentieth century
...
The explosive atmosphere may contain fumes, dust or fibres
...
Users of electrical equipment in these varied
atmospheres are faced with a universal problem
...
Enclosures for protecting
equipment such as motors and lighting equipment are proven and mature
...
Enclosures for primary controls such as
contactors and motor starters are safe and functional
...
European
manufacturers had needs that, until recently, were not significant in North America
...
In

these dense plants, hazardous areas are often in close proximity to one another
...
Today, in North America we now have some of the same
needs but for different reasons
...
We will see more
utilization of existing locations
...


Intrinsic Safety Applications
Hazardous material storage facilities
Automotive paint booths
Inlet monitoring of gas turbines
Organic coating manufacturing
Spray finishing areas
Petroleum dispensing areas
Solvent extraction plants
Utility gas plants and facilities
Aircraft hangars
Fuel servicing areas
Petroleum refining facilities

Another approach to preventing explosions is to install electrical equipment inside of
“explosion proof” housings
...
Explosion proof systems can be large, heavy, and expensive
...

However, intrinsic safety is only feasible for low voltage devices that require limited power
(instrumentation, thermocouples, etc
...

The Elements of an Intrinsically Safe System

An intrinsically safe (IS) system includes the IS device that is located in the hazardous
environment, a power limiting device (IS barrier or galvanic isolator) located in a nonhazardous area, and the associated wiring
...
For a manufacturer to achieve IS
certification of a device, the design and the apparatus itself must be inspected and
approved by an appropriate regulating authority ( for example, FM, CSA, PTB)
...


IS devices must always be connected to power limiting devices, such as intrinsically safe
barriers or galvanic isolators
...
They are placed between the electrical power supply and the IS device
...

Wire runs can change the electrical characteristics of a circuit and must therefore be
considered as part of the overall system
...


Configuring Intrinsically Safe Elements Together

The elements of IS systems can be organized in several different ways
...
The electronic portion of this instrument would be installed in a safe
environment and the remote probe installed in the hazardous environment
...
However, the electronic
portion of the instrument could never be mounted in a hazardous location, seriously
limiting the flexibility of installation
...
Power and signal wires terminate at the IS barriers in the safe environment
...

Installation Guidelines
▪ Installation guidelines are specific to each regulating body by which the IS device is
approved
...

▪ Factors to consider are the power supply and the electrical characteristics of the device
where the signal wires will terminate
...

▪ Users should contact the manufacturers of IS barriers or galvanic isolators for help in
selecting these devices
Certification standards
Across the world, there are differing regulations and requirements which dictate how
products are designed, developed, certified and manufactured in order to be sold to a
customer as I
...
certified
...
S
...
2 NO 157
...
S
...
These differences range from the effects
of static build-up on non-metallic casings to the assessment of cells, even the test
parameters themselves may be different
...
For each
country, the device should be tested in accordance with the local requirements
...


Conclusions
The explosive area equipment market is closely regulated by certification and
government requirements
...

This note concludes as follows:
• The choice to select I
...
or X
...
devices must be based on the functionality of the device
itself and the area the device is intended to operate
...
S
...
S
...
S
...

• X
...
is the best solution for devices offering high energy functionality
...

• If an uncertified product is to be used in an explosive area, then all of the aspects of
that product should be assessed including electrical energy, mechanical energy and
static energy
...


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