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ANP PROJECT QUARTERLY PROGRESS REPORT
and frozen seal ran for 550 hr before
it had to be stopped because of a valve
failure in the loop. Average operating
conditions during t,his run were:
Pump suction pressure 5 to 15 psig
Pump discharge pressure 35 to 50 psig
Shaft speed 1500 rpm
Flow 15 gpm
Packing temperature 750 to 1050OF
Temperature at extreme
end of frozen seal 600 to 800°F
The packing of the pump was made up
of Inconel braid with mixtures of
graphite powder and nickel powder
bet,ween the layers of braid. The pump
shaft was coated with Stellite No. 6.
Operation of the pump was charac-
terized by frequent power surges of
the driving motor because of shaft
seizing in the seal area. Tricresyl
phosphate and lead glass were periodi-
cally injected into the seal as
lubricants, with indeterminant results.
Postrun examination of the shaft
showed very severe scoring in the
frozen seal region (0.056 in. on the
diameter of the 1 1/2-in. shaft).
The second run of this pump was of
600 -hr duration. Loop shutdown was
caused by leakage of the pump flange.
Changes made in the pump and in the
operating procedure before this run
were:
1. pump shaft resurfaced to remove
scoring of first run,
2. packing changed to nickel-foil
wrapped braid with graphite powder
be tween packing 1 ayer s,
3. no lubricants injected.
Operation was much smoother than
that of the first run. This seemed
to be primarily the result of closer
temperature regulation of the frozen-
seal area. It was found that 750 to
800°F was the most satisfactory range
for relatively smooth operation.
Leakage of solid fluoride from the
sen1 at these temperatures varied
approximately from 1 t o 3 g/day. The
packing temperature was maintained at
1050°F.
18
A stop-start technique for the
frozen seal was developed during this
second run. Upon turning off the
iiiotor power, the pump coasts freely to
a stop. However, the shaft becomes
immovable in approximately 30 seconds.
Therefore calrod heating is applied to
the frozen seal area and the tempera-
ature brought to an indicated 850°F.
Theseal then loosens, and the operation
may be resumed with no leakage. Timing
is important, since the application
of too much heat may result in heavy
seal leakage. A quick mean5 of
cooling the seal, such as an air
blast, must be used if the frozen
seal is completely removed.
A second Durco pump has been
modified to include a combination
packed and frozen seal. This pump has
accumulated 84 hr of operation at
1200°F and flow rates up to 60 gpm.
Operation of this pump has been
very difficult because of unexplained
seizing in the seal area. Temperature
rise5 along the seal area indicate
that the seizing is taking place in
the packing area of the seal. This
cannot be definitely concluded,
however, since the shaft has not been
examined in that area.
Some stop-start data were obtained
during one of the runs. It appeared
that a very definite temperature range
(750 to 820°F in this case) was needed
for remote loosening of the shaft and
subsequent startup without leakage.
The start-stop procedure was repeated
five times, and successful operation
followed each trial. However, this
performance could not he duplicated
in later trials. Part of this incon-
sistency is thought to be caused by
the chip retainer, which is being
removed for the next run.
One other change-is being made in
the seal geometry in an attempt to
obtain more consistent operation.
The radial clearance between shaft
and wall in the frozen seal region is
being increased from 0.010 to 0.040
in. to more closely duplicate the