Parr Instrument 1356 - Manual (Page 13)

13
the 238A sealing ring ages and hardens it becomes a partial electrical conductor,
permitting misfires and producing unwanted heating effects. Periodic replacement will
eliminate this potential problem.
The threads on the screw cap should be checked routinely for any burrs or other
deformity. After long use, the threads on the screw cap may become worn to the point
where they will no longer provide a safe closure for the bomb, and the screw cap will
have to be replaced. The following procedure can be used to check the extent to which
the threads have become worn.
Assemble the bomb with the head in the cylinder and count the number of turns required
to bring the screw cap down firmly against the head. Then open the bomb; remove the
head and replace the screw cap, but turn it down to only one-half of the turns previously
counted. This will usually be about four turns. With the screw cap in this position, use a
dial gage to measure the vertical deflection when lifting the screw cap upward. If this
measurement exceeds 1/32 inch (0.030”), the screw cap is unsafe and should be
discarded. The cylinder can then be returned to the factory for inspection. If the threads
on the cylinder are in good condition, a new screw cap can be custom-fitted to the
cylinder.
Never under any circumstances use oil on valves or fittings which handle
compressed oxygen. This precaution applies to all of the oxygen bomb parts as well as to
the oxygen filling connection.
The 1108CL Bombs will resist chlorine, fluorine or bromine in the presence of moisture.
If samples yielding appreciable amounts of these elements are burned in a Parr bomb, the
bomb should be emptied and washed as quickly as possible after each combustion.
If the interior of the bomb cylinder should become etched, the resistance of the metal to
further attack can be improved by restoring the surface to its original highly polished
condition. Bombs needing polishing or other repair work can be returned to the factory.
A periodic overhaul and test at the factory will help to keep any Parr oxygen bomb in
first-class condition.
Parr oxygen bombs can be returned at any time for repair and testing. A factory test is
recommended after every 5000 firings, or sooner if the bomb has been subject to any of
the following conditions: (a) fired with an excessive charge, (b) ignition of any internal
components, (c) machined by any source other than the factory, (d) damaged by corrosive
vapors that might have exceeded 80% of the corrosion allowance, or (e) any changes in
the threads on the bomb cylinder and/or screw cap. When returning a bomb to the
factory, ship it to Parr Instrument Company, 211-53rd Street, Moline, Illinois 61265, with
the package marked for the attention of the Repair Department. A purchase order
covering the repair work should be included with the shipment or mailed to the same
address, as no repairs will be started without specific instructions. Be sure to include a
return shipping address and the name and telephone number of the individual to be
contacted if questions arise concerning excessive repair costs or other problems.
Individual repair parts can be ordered from any Parr dealer or direct from the factory.