Parr Instrument 6400 - Manual (Page 72)

10
Maintenance
P a r r I n s t r u m e n t C o m p a n y 70
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10
Maintenance
Note: Some of the following manual sections
contain information in the form of warnings,
cautions and notes that require special at-
tention. 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 polish-
ing will restore the bomb sealing to an as new condi-
tion. 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 imper-
fection 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 perma-
nent 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 togeth-
er 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.
2. Use a non-metallic object, such as the rounded
corner of a plastic credit card, to simply pry the
seal from its groove.
Smaller diameter seals usually require a different
approach. A portion of the seal should be carefully
pulled, not pried, from the groove with a small pair
of pliers or a hemostat. The exposed portion of the
seal can then be cut, or pulled further to remove the
seal. The pliers or hemostat should never contact
the sealing surface, only the seal.
Bomb Removal
To service or remove the bomb cylinder from
the bucket assembly, remove the 668DD Check
Valve from the bomb cylinder. Remove the 941DD
Wedge with needle nose pliers. Remove the two
SA1632RD18 Machine Screws (see Figure 14-16),
then remove the 942DD plastic bushings and the
1071DD Quad-ring.
The entire bucket can be removed by disconnecting
the bucket probe at the quick disconnect. Carefully
lift the bucket and bomb assembly out of the air
chamber and position horizontally on the calorim-
eter to remove the 925DD Oxygen Bomb Retainer
Nut (see Figure 14-14). Now the cylinder can be
removed from the bucket assembly. Note the posi-
tion of the locating pin.
To replace, follow these steps in reverse.