Silver brazing methods for joining the OH and SF field coil turns for the PLT machine Page: 2 of 5
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The Induction Heating Coil
Thec basic requlrementa of the work coil were
that it he capable of uniformly heating all of the
copper bar lzes used in the 'LX puloidal coils
in 150 seconds or less and be compact enough to fit
in the limited fabrication space available. Many
variations of work coils were investigated. The
final work coil, shown in Fig. 7, is a compromise
of the designs studied. It met all of the design
requirements and has given excellent results. The
coil was made of 0.287" square ETP copper with a
round 0.161" I.D. hole. The flow rate through the
work coil is 0.75 gpm with a pressure drop of 30
psi and results in a temperature rise of 100*F during
maximum rower conditions. It is capable of brazing
copper bars from 1/2" square to 7/8" x 1-1/4" wIth-
out any manual retuning of the power supply.
The parts necessary and the joint make-up are
shown In Fig. 8. The joints are scarfed on -300
angles. The copper sleeves are 0.002" to 0.004"
undersized to the diameter of the counterbore. The
prc-formed rings of silver are used to seal the
ends of the sleeve. Silver wafers and hairpins
are used to seal the joints.
'Sil-Fos'was chosen as the braze filler metal
because it produces a strong joint without the use
of fluxes, which could become entrapped. The
5%P in Sil-Fos is adequate as a wetting agent.
The joint surfaces and components ace polished
with 'Scotchbrite' pads and cleaned with a 1:4
solution of 'cnthone Enplate'#AD-482 and water. A
properly cleaned joint will exhibit a uniformly
wetted surface. The cleared surfaces are protected
from contamination until used; handling is done with
gloves or tweezers.
The support table of the brazing fixture and
alignment ices are shown in Fies. 9 and 10. After
the bar is properly aligned and clamped, the clamp
arm containing the work coil is placed over joint
and the pivo+ pin is inserted. A lava block is
placed between the clamp arm and joint, and the
clar.p is tightened. This keeps the joint halves
from over-riding, allows for expansion to close the
joint. Excess expansion slips under the clamps.
The 'Ircon' infra-red detector 'with a stainless
steel mirror at 45* is attached to the support table.
le induction work coil is energized and the brazing
cycle is automatically controlled. The bar is
heated to the preset temperature limit of 1250*F,
soaked for 2-6 seconds, and shut off. At the con-
clusion of the braze, the clamp with work coil is
removed, and the work is allowed to cool. The work
is unclamped, the joint inspected, filed, cleaned,
pressure-tested and reinspected.
The authors wish to thank Mr. L. Krivanek of
the Taylor-Winfield Corporation and Mr. F. Reed and
Mr. A. Dixon of the Westinghouse Electric Corporation
for thrir useful comments and suggestions concerning
.iy - inn bra inr.
111. C. Johnson, "Dcsign Aspects of Oil and Sr
CoIls for the PLT Machine," Proceodinjp of i:e Fiflh
Symposium on Engineering Problems of Fusion Research,
IEEE Pub. No. 73CH0843-3NPS (1973).
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Bahr, M.W.G.; Heitzenroeder, P.J. Jr. & Johnson, H.G. Silver brazing methods for joining the OH and SF field coil turns for the PLT machine, article, January 1, 1975; New Jersey. (digital.library.unt.edu/ark:/67531/metadc868447/m1/2/: accessed September 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.