Parr Instrument Series 4530 - Manual (Page 13)

Floor Stand Reactors
w w w . p a r r i n s t . c o m 13
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 loca-
tion where care is taken to prevent the accumu-
lation of explosive gases or vapors. To eliminate
any possible spark hazard originating at the mo-
tor, 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 explo-
sion proof switch and wiring which will comply
with the local electrical code.
2. The Temperature Controller
The Series 4848 Temperature Controllers fur-
nished 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 explo-
sion 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 tem-
perature of the element becomes high enough
to ignite fl ammable vapors. This hazard must be
evaluated for each individual installation since
major modifi cations are required if the heater
must be isolated from the surrounding atmo-
sphere. Users who consider this a signifi cant
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, intrinsi-
cally safe barriers are available.
PERIODIC PRESSURE TESTS
Each cylinder used in a Parr stirred reactor is tested
under hydrostatic pressure to 1.3 times its maxi-
mum rating before it is released from the factory.
Micrometer caliper measurements are taken during
this test to check the defl ection of the walls under
pressure. Excessive defl ection or failure of the
metal to resume its original dimensions after pres-
sure is released indicates that a cylinder is poten-
tially unsafe and it will be rejected. Similar tests
should be made at regular intervals during the life
of each cylinder, and particularly whenever the user
suspects that the equipment has been over-stressed
or damaged.
Some laboratories maintain hydraulic test facilities
and make it a rule that all pressure vessels must
be tested at regular intervals. Records are kept of
defl ections at specifi c test pressures so that any
increase in defl ection becomes a warning that the
metal has lost strength. Any cylinder that fails to
return to its original dimensions after application of
the prescribed hydrostatic test should be discarded
as unsafe for further use.
Users who do not have pressure test facilities can
return any Parr pressure vessel to the factory for hy-
drostatic testing and overhaul. This should be done
whenever the metal shows excessive damage from
corrosion or whenever an over-pressure or other
unusual occurrence raises any safety questions. To
return a vessel for repair, contact Parr Instrument
Company for a return authorization number. Ap-
paratus returned for testing and overhaul should
be shipped prepaid to Parr Instrument Company,
211-53rd Street, Moline, Illinois 61265. An order or
letter of instructions should be mailed to the same
address, as no repair work will be started without
specifi c instructions and a Health & Safety Assur-
ance Certifi cation form (F0042) signed by a respon-
sible user.