Cashco DA4 - Manual (Page 6)

IOM-DA4 6
to ensure that no scratches are imparted
to any portion of the piston-guide bearing
(13) groove.
e. Remove wiper seal (16), if supplied, from
within cage (19).
f. Remove wiper washer (17.1) or camber
adjusting washer (17.2), if supplied, from
within cage (19).
g. Remove o-ring lower stem seal (14.3)
from plug (20).
h. Remove seat ring (21); examine for signs
of leakage. If seat ring (21) shows signs of
signifi cant leakage, determine if op er at ing
con di tions of pressure, pressure drop, or
temperature are ex ceed ing limits.
2. Units with Metal Diaphragm(s) (See Fig 3):
a. To disassemble the ITA, hold the lower
part of the valve plug (20) in a bench
vise; do not hold on the machined sur-
face in the plug's (20) spindle area. (The
spin dle “slides” in the pressed-in-place
lower guide bushing (24) and can not be
al lowed to be marred.)
b. Using a special double-posted spanner
wrench fi tting (to order see NOTE in
Section X, Parts Ordering Information),
turn the piston-guide bear ing (13) CCW
to loos en; pis ton-guide bear ing (13) can
be re moved by hand after loos en ing.
c. Pull the valve plug (20) downwards out
of the piston-guide bearing (13) and out
thru the bottom of the cage (19).
pres sure drop, or tem per a ture lim its.
Remove dynamic side seal (27) com po-
nents and discard. Special care should be
taken when using “tools” to remove the
components to ensure that no scratches
are imparted to any portion of the piston-
guide bearing (13) groove.
f. Remove wiper seal (16), if supplied, from
within cage (19).
g. Remove wiper washer (17.1) or camber
adjusting washer (17.2), if supplied, from
within cage (19).
h. Remove o-ring lower stem seal (14.3)
from plug (20).
i. Remove seat ring (21); examine for signs
of leakage. If seat ring (21) shows signs of
signifi cant leakage, determine if op er at ing
con di tions of pressure, pressure drop, or
temperature are ex ceed ing limits.
3. Clean all reusable metal parts according to
owner's procedures.
D. Inspection of Parts:
1. After inspection remove from the work area
and dis card the old “soft goods” parts (i.e. o-
rings, di a phragms, seals, gaskets, etc.) after
in spec tion. These parts MUST be re placed
with fac to ry supplied new parts.
2. Inspect the metal parts that will be reused. The
parts should be free of surface con tam i nants,
burrs, oxides, and scale. Rework and clean
parts as necessary. Surface con di tions that
affect the regulator performance are stated
below; replace parts that can not be re worked
or cleaned.
3. QC Requirements:
a. Valve plug (20);
1. 16 rms fi nish on its seating surface
for tight shutoff.
2. No major defects on bottom guide
spin dle.
b. Cage (19);
1. 16 rms fi nish on cylinder bore. No
“ledges” formed due to wear from
moving dynamic side seal (27) or
wiper seal (16).
c. Lower guide bushing (24) (non-re place-
able):
1. 16
rms fi nish on bore.
2. Max 0.015 inch (0.38 mm) clearance
be tween valve plug (20) spindle and
lower guide bushing (24).
d. Internal sensing drilled plug (32);
Figure 3: Assembled ITA,
Metal Diaphragm Construction
d. Remove the piston-guide bearing (13)
from the upper end of cage (19).
e. Examine the com po nents (27.1, 27.2,
27.3, 27.4, 27.5, 27.6) of the dy nam ic
side seal (27) mechanism to de ter mine
if sig nifi cant leakage was oc cur ring. If the
dy nam ic side seal (27) shows signs of
sig nifi cant leakage, de ter mine if operat-
ing conditions are ex ceed ing pres sure,
13
27
15
17
19
21
20