Table of Contents
Advertisement
Increased Safety
Non-Electrical
Thermo Fisher Scientific
ignition could in fact occur. The apparatus is, however, enclosed in a
flameproof (or explosion proof) enclosure, which is rated to contain
any combustion products such that:
a. The enclosure remains intact.
b. Hot gases cannot escape and propagate the combustion
beyond the enclosure.
Flameproof enclosures are hence very robust, typically of cast iron or
cast aluminium construction. Flanges, etc. are designed so as to
provide a long, well defined path length for hot gases to follow if
they are to exit the enclosure. As a result, gases are sufficiently cool
when they reach the outside (hazardous) environment so that further
flame propagation does not occur. As a result of the nature of this
protection, a particular flameproof enclosure is only certified for use
with a particular set of gas groups (see above for gas group
definitions). Flameproof enclosures may additionally be fitted with
some form of weatherproofing seal, but this does not form part of the
protection method.
Cable entries to the enclosure must be of a type certified to maintain
the flameproof integrity of the enclosure. This might involve some
form of potting (with an epoxy compound) of the cable into a cable
gland and may also restrict the type of cable that can be used (e.g.
solid single core wires).
On the Prima PRO Ex and Sentinel PRO Ex systems, flameproof
protection is used for the electrical isolation enclosure(s) and the
rotary pump motor.
This is a "non-sparking" method of protection. It relies on methods
of construction of the electrical apparatus that eliminate any
possibility of sparking in normal operation. For example, screw
terminals must be of a certified type that will not vibrate loose in
service. The apparatus must be enclosed in a weatherproof enclosure
(e.g. IP65) to prevent the ingress of conductive dusts or liquids that
could cause sparks.
This method is used for the purge controller / monitor unit.
Where possible, the use of non-electrical apparatus is an obvious
way of avoiding electrical sparks. However, it should be noted this
does not exclude the possibility of non-electrical sources of ignition
such as mechanical sparks, hot surfaces due to friction heating, and
static discharge.
Commonly, this involves the use of pneumatics as an alternative and
can be simpler than using protected electrical apparatus.
Interconnection and servicing may also be simplified.
Prima PRO & Sentinel PRO Mass Spectrometers User Guide
Hazardous Area Operation
Hazardous Area – General
A-7
Advertisement
Table of Contents
