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design of the first combination seal
purrlp, discussed above, which ran
sa t,i s fa c to ri 1 y .
Pump with Frozen-Sodium Seal.
Approximately 4000 hr of operation
had been accumulated when the test
of the pump with the frozen-sodium
seal had to be terminated because of
leaking flanges and failure of a
thermocouple well. The final run
was of LOOO-hr duration at a pump
temperature of 1P00'F.
Postrun examination of the pump
showed no measurable wear of the
shaft in the frozen-seal area. Scoring
of the rear face of the impeller,
which indicated interference with the
housing, was very severe and was
probably the source of pump noises
during the last run.
Allis-Chalmers Pump. During this
quarter the Allis-Chalmers pump that
has a hydrostatic bearing was tested
with NaK as the system fluid. When
this pump was first tested, the shaft
gas seal provided by Allis-Chalmers
was used. The seal consisted of three
Graphitar rings, each of which had
three 120-deg segments. The room-
temperature di ametral clearance between
shaft seal rings was designed to be
between 0.0065 and 0.008 inch. A t
operating conditions (approximately
170 gpm, 45-ft head, and elevated
temperature), the diametral clearance
and the gas leakage to atmosphere past
these rings were to approach zero.
In the first test, the gas leakage
past the seal was excessive, and a
large amount of gas was entrained in
the system fluid. Therefore two
modifications were made to the pump:
a rotary face seal was added to
decrease gas leakage to a tmosphere,
and additional baffling, suggested by
Allis-Chalmcrs, was placed in the
region above the pump impeller to
reduce gas entrainmentin system fluid.
The second test revealed that the
additional baffling did materially
reduced gas en trainmen t in the sys tern
fluid and also that the rotary face
PERIOD ENDING DECEMBER 10, I952
seal reduced gas leakage toa tolerable
level. The unlubricated rotary face
seal, however, squealed and chattered
aftera very short period of operation.
Further testing indicated that the
seal operating temperature was sensitive
to changes in pump suction pressure,
a condition that may be overcome by
using a balanced bellows seal. These
tests indicate that this pump w i l l
give satisfactory performance when a
good gas seal is incorporated in the
design. A frozen-sodium gas seal is
presently being fabricated for test
in this pump.
' Laboratory-Size Pump with Gas Seal.
The laboratory-size centrifugal pump
with a gas seal, described previ-
ously,(') has been operated for a
total of 1275 hr with the fluoride
fuel NaF-ZrF,-UF, (46-50-4 mole %) at
temperatures up to 1500°F. The average
fluid temperature during this period
was approximately 1350°F. The satis-
factory performance data obtained are
presented in Fig. 2.1. The pump
discharge pressure and pressure drop
across the venturi were measured by
means of the null-balance level-
indicator system.
The initial difficulty of liquid-
level detection in the pump bowl at
high shaft speeds has been overcome.
The turbulence in the liquid surface
has been reduced by additional baffling,
and the action of the probes used
for level detection has been quite
satisfactory up to shaft speeds of
4400 rpm.
The rotary gas seal - Graphitar
No. 30 lubricated with spindle oil
running against hardened tool s tee1 -
has functioned with extremely small
gas leakage and without maintenance
or appreciable wear during the total
running time. Oil leakage past the
seal assembly was collected, and it
was found to amount to less than
1 cm3 per 24-hr period. The only
(l)W. G. Cobb. P. W. Taylor, and G. D. Whitman,
ANP Quar. Prog. Rep. Sept. IO, 1952. ORNL-1375,
p. 16.
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