Parr Instrument 6400 - Manual (Page 66)

6400
Calorimeter Instruction Manual
9-1
MAINTENANCE
Note:
Some of the following manual sections contain information in the form of
warnings, cautions and notes that require special attention. Read and
follow these instructions carefully to avoid personal injury and damage to
the instrument. Only personnel qualified to do so, should conduct the
maintenance tasks described in this portion of the manual.
Caution – Risk of Electrical Shock
Disconnect the electrical power before servicing or replacing any
components!
Inspection of Critical Sealing Surfaces
The sealing grooves and related surfaces for most of the Parr bombs are machined to
tolerances as small as +/- 0.001" (0.03mm). As a result, any imperfection in a sealing
surface resulting from either normal use or carelessness in handling the bomb can
cause the bomb to leak. If the damage or accumulated wear is much less than 0.001"
(0.03mm), then careful polishing will restore the bomb sealing to an as new condition.
Imperfections that penetrate the sealing surface more than one or two thousandths of an
inch (0.03-0.06mm) may render the seal surface unserviceable.
Any surface that comes in contact with an elastomer seal should be carefully examined
for imperfections that would compromise its ability to seal. A freshly sharpened pencil
can be used to probe the metal sealing surfaces for significant imperfection. If the pencil
point hangs up in the imperfection, further attention is warranted. An attempt should be
made to polish (remove) any significant imperfections. This operation generally requires
the use of a lathe in order to guarantee that the sealing surface to be repaired remains
concentric with the mating surface. Knowledge of the dimensional tolerances and the
ability to accurately measure or gauge the affected area is required in order to insure
that too much polishing (metal removal) has not taken place. We recommend that
bombs with significant imperfection of this nature be serviced at Parr.
Caution! Do not pry elastomer seals (o-rings and quad-rings) from seal
grooves with metallic tools.
The use of dental picks and other metallic tools to pry the seals from their grooves must
be avoided. These hard steel tools, if misused, can leave permanent tool marks on the
sealing surface, which are difficult or impossible to remove. These blemishes are hidden
by the seal during normal use and as a result, are not readily apparent as the cause of a
leaking bomb.
Larger size seals (0.8" or 20 mm O.D.) typically used to seal the bomb head can be
extracted from its groove using either of the following two methods:
1. Grasp the outer circumference of the seal with the thumb and forefinger and
slide them together while applying sufficient pressure on the seal to cause it
to pucker out of the groove. With the other hand, grab the exposed, pinched
section and pull the seal from the groove.