Parr Instrument Series 4570 - Manual (Page 17)

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4570 HP/HT Pressure 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.