Parr Instrument Series 4520 - Manual (Page 18)

- 18 -
4520 Bench Top Reactors Parr Instrument Company
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
any possible 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 that is approved
for use in Class 1, Groups C & D, and
Class 2, Groups E, F, & G atmospheres.
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 Temperature Controller
The Series 4848 Temperature
Controllers furnished with these reactors
contain switches and other elements that
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 that 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.