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Ceramic Protection
Tubes-
Silicon Carbide and
Hexaloy@
Silicon
Carbide
-
Oxide
Bonded
Silicon
carbide
protection
tubes
(SG) have a maximum service
temperature
of
2730"F
(1500'C).
Silicon carbide tubes
are
not gas
tight.
They are about
14%
porous.
Silicon
carbide also
has
good thermal shock and corrosion resistance.
lt
also
has excellent ther-
mal
conductivity.
Because of
this they are best
used as a
secondary
protection tube
to protect
Mullite
or
Alumina
primary tubes from
direct flame
impingement.
Silicon carbide tubes are also frequently used
in
oxygen atmosphere furnaces and molten non-ferrous met-
als
such
as
Aluminum,
since
they
are
very
resistant
to
oxidation
and slag
attack.
Composition -
89.6"/o
Silicon
Carbide
(Black, coarse
grained Alpha
/
Beta
mix)
,
8.5"/o
Silicon Dioxide,
.7%
Aluminum
Oxide,
.7o/o
lron
Oxide.
Silicon
Carbide
-
lUitride Bonded
Nitride bonded silicon carbide
tubes
(SCN) have the same characteristics as Ox bonded silicon carbide with
a
few exceptions. They
have
a
maximum service
temperature
of
2800"F (1550"C).
Nitride bonded tubes
are
more
dense and
less porous
than
oxide bonded
tubes.
They also
have slightly better
thermal
shock,
corrosion
resistance, and twice
the
crushing strength of
the
oxide bonded tubes.
Composition -
75.Oo/o
Silicon Carbide (Black, coarse grained Alpha
/
Beta
mix),
23.4%
Silicon
Nitride,
.5%
Silicon
Dioxide,
.3%
Aluminum Oxide,
.3%
lron
Oxide.
scP-*
SCNP.*
1
314
1
314
1
1
44.5
44.5
25.4
25.4
Plain
Tube
PIaIn Tube
SCB.*
scNB-*
1
1
314
314
1
1
44.5
44.5
25.4
25.4
Bushing
2" x
314"
NPT
Cemented on
the
Tube
scc-*
1
314
1
44.5
25.4
Collar
3"
O.D.
x
1" Wide
SCF.*
SCNF-*
1
1
314
314
1
1
44.5
44.5
25.4
25.4
Fitting
314"
NPT Female
held
by
three set
SCTEWS
FIfrIng
sc112-*
scl34-*
2
2
.62
.82
50.8
50.8
15.7
20.8
lsopressed around
a
steel tube
1/2" NPT
314"
NPT
P
Isopressed
.
Add
length
(P)
as
the suffix, multiples of
6
inches (152.4mm)
are
stocked.
Page
102