ORNL-2106 - the Molten Salt Energy Technologies Web Site

and lose their hardness in the presence of Cellu-
lube. These particular problems could be solved
by using O-rings made from butyl rubber, but,
unfortunately, butyl rubber suffers severe radia-
tion damage. Tests to determine the radiation
stability of Cellulube are planned for the near
future.
Dowtherm A, which is a good heat transfer
medium but which has poor lubricating properties,
was also selected for study because it is rela-
tively stable upon exposure to radiation. Dowtherm
A is a eutectic mixture containing 26.5% diphenyl
and 73.5% diphenyloxide that is manufactured by
the Dow Chemical Co, of Midland, Michigan. The
only test run to date was terminated after 575 hr
due to a motor failure, There was no transverse
load applied during the test. The Dowtherm A
operating temperature was 210 to 220'F. Both
seals had well-developed wear patterns, The upper
seal showed no leakage after the first 4 hr. The
lower seal had no leakage for the first 150 hr, at
which time it began to leak at a nearly uniform
rate of 20 cm3/day. Upon examination, the lower
seal rotor was found to have a light copper deposit.
This is contrary to the information provided by Dow.
The system used for this test had previously been
operating with Cellulube, und, although it was
carefully and thoroughly cleaned, it is possible
that some Cellulube may have remained and caused
the plating. This problem will be investigated in
future tests,
The process side of the seal nose had a black,
gummy deposit, which proved to be virtually all
carbon. Since there was no evidence of physical
damage to the Gaphitar seal nose, it is probable
that this deposit was the residue from Dowtherm A
which thermally decomposed in leaking across the
seal interface. Ag the elastomer O-ring
As originally designed the reactor pumps utilized,
as the upper bearing, a spherical roller type of
PERIOD ENDING JUNE 10, 1956
antifrictioq bearing. In addition to providing ample
thrust and radial load-carrying capacities, this
type of bearing permitted shaft alignment with
respect to the journal bearing without attendant
shaft deflections. This design appeared to be ode-
quate until tests of long duration on pump rotary
elements revealed that the initial bearing end play
of 0.0045 in. (maximum) had increased by a factor
of 2 to 3. Such excessive end play is not con-
ducive to good dynamic seal performance and it
also interferes with the close axial tolerances
required in these pumps. The easiest solution to
this problem, with respect to minimizing pump
redesign, was to change to a double-row angular-
contact bearing having convergent angles of con-
tact. This has been done and, to date, all per-
formance has been satisfactory. However, more
operating time will be necessary to prove the
reliability of the redesigned bearing arrangement.
A temporary impasse has been reached in the
development of seals for the NaK (primary and
auxiliary) pumps. All the seals purchased for
comparative testing have failed in operation. The
seal obtained from the Sealol Corporation failed
because the unhardened stainless steel wear ring
rotor and the mating carbon ring wore out in less
than 20 hr. The ceramic rotor of the seal obtained
from the Durametallic Corporation disintegrated
upon application of a 7OoF temperature differential
to the lubricating oil. An attempt to correct this
condition will be made by utilizing a thin ceramic
facing on a steel-bodied rotor, The Byron Jackson
Co. seals never developed full wear patterns, even
after runs in excess of 300 hr. This condition
apparently resulted from distortion of the relatively
thin rotor. At no time during test operation with
any of these seals was Q satisfactory leakage rate
Therefore efforts are being made to
configuration similar to that being
used on the fuel and sodium pumps. In addition,
other promising types of commercially available
seals will be investigated.
Pump Lube-OiI System GarAttenuat
5. M. DeCump
he leakage tests of the seals
MF-2 fuel pump
tinued with Gulfspin 60 oil bein
lubricant. For these tests the temperature of the
%. M. Decamp, ANP Qwr. Prog. Rep. March 10, 1956,
ORNL-2061, p 48.
47