Cashco DA2 - Positive Differential - Manual (Page 10)

IOM-DA2 10
Recommended Torque values are:
Body Size Torque
in (DN) ft-lbs (N-m)
1/2" - 1" (15-25) 30-50 (41-68)
1 1/4" - 2" (32-50) 45-70 (61-95)
3. Position piston-guide bearing (13)
over and into upper end of cage (19)
until the cap seal (27.1) edge touches
the upper lip of the cage (19). While
gently applying force to press the
piston-guide bearing (13) into the
cage (19), simultaneously use fi ngers
to lightly press the u-cup seal (27.3)
inwards into the groove of the piston-
guide bearing (13) until the u-cup seal
(27.3) “slips into” the cage (19). DO
NOT USE TOOLS, LUBRICANT, OR
HEAVY FORCE TO ENGAGE THE
U-CUP SEAL (27.3) INTO THE CAGE
(19).
4. Place properly oriented seat ring (21) onto its
shoul der at the lower end of cage (19).
5. Composition Diaphragm Designs.
a. Place new o-ring lower stem seal (14.3)
into groove of valve plug (20).
b. Insert valve plug (20) upwards through
lower end of cage (19) and through the
center hole in piston-guide bearing (13),
also capturing camber adjusting washer
(17.2), wiper washer (17.1) and wiper seal
(16), if supplied. Hold plug (20) and cage
(19) together.
c. This completes ITA reassembly.
6. Metal Diaphragm Designs.
a. Insert valve plug (20) upwards through
lower end of cage (19) and through the
center hole of camber adjusting washer
(17.2) or wiper washer (17.1) and wiper
seal (16).
b. Engage valve plug (20) with piston-guide
bearing (13) threads and tighten manually
as far as possible.
c. Place ITA into a vise and grasp at a hub
location on the valve plug (20) that is not
in the “spindle” zone. (See Figure 3.)
d. Using a special double-posted spanner
wrench, (to order see NOTE in Sec tion
IX, Parts Ordering In for ma tion), tight en
the piston-guide bear ing (13) to the valve
plug (20) with the following torque values.
Do NOT allow valve plug (20) to rotate
against seat ring (21) during tight en ing.
e. This completes ITA reassembly.
F. Main Reassembly:
1. Place body (23) in a vise.
2. Reinstall internal sensing drilled plug (32) with
compatible thread sealant.
3. Insert the lower piston spring (22) into the
body (23), if supplied.
4. Fit the o-ring cage seal (15) into its body (23)
groove.
5. With the ITA held manually in the closed po-
si tion, insert ITA into body (23).
6. Properly align all three cage bolt (18) holes
as there is only one circumferential location
pos si ble for this align ment. If a lower piston
spring (22) is used, apply downward force to
the top of the cage (19) until the ITA is lowered
suf fi cient ly to engage the cage bolts (18) into
the body (23). Engage all of the cage bolts
(18), then evenly screw in the cage bolts in
one-half revolution increments to pull down
the ITA, taking care NOT TO “COCK” THE ITA
IN THE BODY. Torque the cage bolts (18) to
13-15 ft-lbs (18-20 N-m).
7. Composition Diaphragm Designs:
a. For the following steps b.–h., the upper
end of valve plug (20) MUST be manually
held up if unit is not supplied with lower
piston spring (22).
b. Place new o-ring middle stem seal (14.2)
into groove of piston-guide bearing (13)
upper surface.
c. Position lower diaphragm pusher plate
(10) over upper end of valve plug (20)
with tongue and groove “groove” on up per
side.
d. Place new o-ring upper stem seal (14.1)
into groove on lower diaphragm pusher
plate (10).
e. Place diaphragm(s) (9) over end of valve
plug (20). NOTE: For multiple di a phragms
(9) that include TFE material, the TFE
should be on wetted side.
f. Place upper diaphragm pressure plate
(8) over upper end of valve plug (20) with
tongue and groove “ridge” on lower side.
g. Place anti-seize lubricant on valve plug
(20) thread ed end. Engage diaphragm
lock nut (7) with upper end of valve stem
(20) as far as possible manually.
h. Place a wrench on diaphragm lock nut (7)
and a torque wrench on the upper end