Oil
filled leaded glass radiation shielding windows, when properly
maintained, can provide the user many years of quality viewing. The
shielding oil in the window provides six valuable special functions.
1) It couples the glass surfaces and simulates the view as a solid
glass block by eliminating numerous internal reflective surfaces, 2)
It increases the light transmission through the window, 3) It acts
as an insulator to help prevent a dielectric discharge, 4) It
increases the view angles through the window, 5) It provides thermal
stabilization of all components within the window housing, and 6) It
provides neutron shielding in proportion to the distance between the
shielding glass components.
The oil however, is susceptible to degradation from
radiation, light, and moisture. It is therefore extremely important
to test the oil at regular intervals to determine if an oil change
is required. The degradation process is very slow and when
degradation is initially noticed, it appears as a light gray haze of
film on the surface of the shielding glass. At this point, the
damage to the shielding glass is significant and the glass surfaces
must be cleaned to stop continued degradation. Failure to do so will
eventually result in etching the glass surfaces, which means the
shielding window must be refurbished to restore the glass surfaces
to provide quality viewing.
There are four analytical tests that can be
performed on the shielding oil in the windows to detect early
degradation well before hazing or filming begins. The tests and
their acceptable limits are listed below. Any test that exceeds the
maximum acceptable limit is an indication that an oil change should
be performed immediately.
|
TEST
|
ASTM
|
NEW
OIL LIMITS
|
MAXIMUM OIL LIMITS
|
| 1. Neutralization |
D-974 |
0.001 MG KOH/G |
.008 MG KOH/G |
| 2. Peroxide PPM |
E-299-20 |
<0.1 PPM |
30 PPM |
| 3. Interfacial Tension |
D-971-82 |
<28 Dynes |
>46 Dynes |
| 4. Water Content |
Aquatest 8 |
<2 PPM |
5 PPM |
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Data and information contained in the tutorial was written by Dale A. Tobias, Premier Technology, Inc. and Hienz E. Hoffman and William G. Wash, Schott Glass Technologies, Inc. and may be reproduced only with written consent.
For information, contact Lyle Freeman
Vice President of Business Development
(208) 782-9129 lfreeman@ptius.net
