Parr Instrument Series 4580 - Manual (Page 20)

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EXPLOSION PROOF
OPERATION
If the local safety code requires that
equipment installed in the user’s laboratory
must be explosion proof, there are four
possible ignition hazards to be considered:
1. The Motor
The standard adjustable speed motor
is not explosion proof, yet these motors
are not unduly hazardous if operated in a
well ventilated location where care is
taken to prevent the accumulation of
explosive gases or vapors. To eliminate
a spark hazard originating at the motor,
Parr can furnish an air motor as
described previously, or the reactor can
be equipped with a variable speed,
explosion proof motor which is approved
for use in Class 1, Groups C & D, and
Class 2, Groups E, F, & G environments.
Explosion proof motors are furnished
with a temporary power cord and plug
which are not explosion proof. The user
should remove this temporary wiring and
replace it with an explosion proof switch
and wiring which will comply with the
local electrical code.
2. The Controller
The Parr Controllers furnished with
these reactors contain switches and
other elements which are not explosion
proof. The minimal spark hazard
associated with these units can be
resolved by installing the controller in a
remote location outside of the hazardous
area or by enclosing it in an approved
explosion proof housing. If enclosed
within a positive pressure, clean air
housing, the discharge from the housing
must be directed into a safe area. If
requested, Parr will furnish the long lead
wires needed to mount the controller in a
remote location. If the controller is to be
installed in an explosion proof housing,
the user must provide the necessary
housing and installation.
3. The Heater
The elements in the heater could be
dangerous in an explosive atmosphere if
the surface temperature of the element
becomes high enough to ignite
flammable vapors. This hazard must be
evaluated for each individual installation
since major modifications are required if
the heater must be isolated from the
surrounding atmosphere. Users who
consider this a significant hazard are
urged to contact the Parr Instrument
Company for further discussion and
suggestions which might be helpful.
4. The Wiring
The wiring provided with the standard
reactor systems does not meet the
standards prescribed for explosion proof
operation. Optional, intrinsically safe
barriers are available.