119
P a r r I n s t r u m e n t C o m p a n y
1 - 8 0 0 - 8 7 2 - 7 7 2 0
5
O p t i o n a l F i t t i n g s
Explosion Proof Apparatus
A
ll Parr reactors are nor-
mally equipped with open
type, variable speed motors,
electric heaters and controllers
intended for use in non-hazar
dous environments. These
standard units can be used
in most laboratories without
undue hazard, but there will be
situations where the installed
equipment must be considered
explosion proof. Parr offers
various optional stirrer drives
and heating systems to meet
these strict requirements.
USA and International
Codes
Designing electrical
equipment to be operated
in a hazardous location is a
complex subject, governed by
extensive national electrical
codes and supplemented by
local regulations which require
that all electrical equipment
installed in a governed loca-
tion must be approved for use
with the specific gas, vapor
or dust that will be present in
that location. USA electrical
codes classify hazardous loca-
tions according to the nature
and concentration of specific
hazardous or flammable mate-
rials. These are divided into
three classes:
Class I
- Flammable liquids,
gases or vapors.
Class II
- Combustible
or electrically conductive
dusts.
Class III
- Easily ignitable
fibers or flying particles.
There are two divisions
within each of these classes.
Division 1
- Where the
flammable material exists in
the atmosphere under nor-
mal operating conditions.
Division 2
- Where the haz-
ardous material is confined
within a closed system from
which it may be released
only under abnormal condi-
tions, such as a leak
in the system.
Class I locations are further
subdivided into four Groups,
A, B, C and D which identify
specific explosive gases and
vapors. Explosive dusts and
fibers in Class II are subdivided
into Groups E, F and G. Most
hazardous applications for Parr
apparatus will occur in atmo-
spheres identified by Class I,
Group A for acetylene, Group
B for hydrogen and Groups C
and D for most other combus-
tible gases and vapors. Class
II, Group F covers coal dust.
Most other combustible dusts,
such as flour and grain, are in
Group G. Minimum ignition
temperatures and energy lev-
els are established for specific
materials in each group.
The European Community
uses a significantly different
convention identified as ATEX
or Atmospheres Explosives. In
this, the user must identify the
level of protection required for
their installation. Parr will work
with our customers operating
under ATEX to provide equip-
ment meeting current ATEX
requirements.
Explosion Proof Motors
Because of sparking from
brush contacts, electric motors
clearly represent the principal
explosion hazard introduced
by a stirred reactor. Electric
motors approved for Class I-
Division 2, Groups C and D,
and Class II, Groups F and
G atmospheres are readily
available in most sizes and
voltages. These sealed motors
are suitable for most hazard-
ous applications, and they are
sometimes used with hydro-
gen, but they are not approved
for Class B atmospheres. To
meet Class B requirements,
a motor must be purged by
building up a positive pres-
sure of air within the motor
to prevent explosive gases or
vapors from reaching electrical
ignition sources. This requires
a special, air purged motor
which can be provided when
required.
An alternate method of
dealing with the explosion
hazard is to use an air driven
motor. These are powered
by compressed air and offer
a convenient and satisfactory
drive system for use in flam-
mable atmospheres, including
hydrogen. They are available
in sizes suitable for all Parr
reactors.
Model 4524 Reactor, 2000 mL, Fixed Head Style with
Aluminum Block Heater
