CHAPTER7
deposits
of
dust or dirt since these buildups can
cause a decrease
in
air capacity or
lead
to
an
unbalanced condition.
CAUTION!
If
the
boiler
Is
Installed
In a
dusty
location,
check
'the vanes
occasionally
for
deposits
of
dust
or
dirt.
These
buildups
can
cause a decrease
In
air
capacity,
lead
to
an
unbalanced
condi-
tion,
or
cause
damage
to
the
equipment
•.
M.
SAFETY
VALVES
The safety valve
is
a very important safety device
and
deserves attention accordingly.
Follow
the
recommendations
of
your boiler in-
spector regarding valve inspection and testing.
The frequency
of
testing, either
by
the
use
of
the
lifting lever or
by
raising
the
steam pressure,
should be based on
the
recommendation
of
your
boiler inspector and/or
the
valve manufacturer,
and
in
accordance with sections
VI
and
VII
of
the
AS~
Boiler
and
Pressure Vessel Code.
Avoid excessive operation
of
the
safety valve
because even one opening can provide a means
of
leakage. Safety valves should
be
operated only
often enough
to assure that
they
are
in
good
working order. When a pop test
is
required, raise
the
operating pressure to
the
set pressure
of
the
safety valve. Allow
the
valve
to
open
and
reseat
as
it
would
in
normal service.
Do not
hand
operate
the
valve with
less
than
75%
of
the
stamped set pressure exerted on
the
under-
side
of
the
disc. When hand operating,
be
sure
to
hold
the
valve
in
an
open position long enough
to
purge accumulated foreign material
from
the
seat area
and
then allow
the
valve to snap shut.
750-150
INSPECilON
AND MAINTENANCE
Frequent usage
of
the
safety valve will cause
the
seat
and
disc to become worn
and
cause
it
not
to
seal properly. This will cause
the
valve to leak
and
necessitate down·time
of
the
boiler for valve
repair or replacement. Repair
of
a valve must
be
done only
by
the
manufacturer or
its
authorized
representative.
Avoid having
the
operating pressure too near
the
safety valve set pressure. A
10%
differential
is
recommended. An even greater differential
is
desirable
and
will assure better seat tightness
and
valve longevity.
N. FUEL OIL
METERING
VALVE,
ADJUSTING
AND
RELIEF
VALVES
In
the
event that a leak occurs
in
.the
packing of
the
metering valve,
the
packing nut should
be
snugged gradually to stop
the
leak.
CAUTION!
Excessive
tightening
of
meter-
ing valve
packing
nut
prevents
free
movement
of
the
metering
stem and can cause damage
to
the
equipment.
If
replacement
of
the
metering valve packing
is
necessary, procure
PIN
880-370
kit
and
install
in
accordance with
the
following procedure.
(1)
Shut off
the
oil flow.
Be
sure
no
pressure shows on
the
gauge.
(2) Match mark
the
cam hub
and
drive
shaft. This will enable replacement
of
the
cam
in
the
original position
and
result
in
a minimum
of
cam adjustment when
the
burner
is
refired.
CHAPTER 7·13
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