Direct-Acting - Robertshaw 84374 Series Quick Start Manual

MAINTENANCE - See Figure 4
WARNING: USE CARE WHEN DISASSEMBLING,
SPRING FORCES PRESENT.
Caution: Do not subject O-rings, gasket, or
diaphragms to cleaning fluid, acetone, or any
halogenated hydrocarbons such as degrease
liquids, etc. Clean only with a soft, dry cloth.
Metal parts can be cleaned with a suitable solvent,
then dried thoroughly before reassembly.
Pressure Assembly
Remove the three screws (detail 35) holding the sensor to
its mounting bracket (detail 34). Remove the sensor.
Remove the remaining seven screws (detail 37) securing the
housing together. Remove the lower housing plate (detail
38) and then the exposed diaphragm, (detail 43). Remove
the retaining screw (detail 39) and the diaphragm shoe
(detail 42). Remove the four screws (detail 41) securing the
upper housing and remove the upper housing (detail 33).
The O-ring (detail 32) should come off with the housing. If
not, remove it. Replace the defective parts and reassemble*
in reverse sequence.
Bushing
To replace the bushing O-ring (detail 24) remove the
bushing (detail 25) and replace the defective O-ring.
Reassemble* and replace in valve housing (detail 15).
Recalibrate if sensor is an automatic reset model.
Spring Housing Assembly
Remove the cap screw (detail 1) and washer (detail 2) and
turn the adjustment screw (detail 5) counterclockwise to
bring the range spring (detail 6) to its free length. Remove
the four screws (detail 11) securing the spring housing
(detail 3) and remove the housing. Remove the range spring,
spring seat locking screw and spring seat (detail 4).
Reassemble* in reverse sequence.
Valve Housing Assembly
Remove the pressure assembly, spring housing assembly
and bushing as described above. Proceed as described under
applicable instructions for either the direct-acting or
reverse-acting sensor.

DIRECT-ACTING

Remove the four screws (detail 31) securing the flange
that was under the pressure assembly. Remove tile flange
(detail 30). Prevent the spring seat (detail 9) from rotating
and remove the exposed diaphragm clamp. Remove the
exposed diaphragm (detail 14). Pull the stem (detail 21)
from the valve housing by removing it as an assembly with
the remaining flange (detail 13). (The spring seat will
remain intact).
Prevent the spring seat from rotating and remove the
locking screw (detail 8). Prevent the stem from rotating and
remove the spring seat. Remove the flange from the stem
assembly. Proceed with the instructions under "DIRECT
AND REVERSE ACTING."
REVERSE-ACTING
Remove the four screws (detail 31) securing the flange
that was under the pressure assembly. Remove the flange
(detail 30).
Prevent the spring seat (detail 9) from rotating and
remove the locking screw (detail 8). Prevent the exposed
diaphragm clamp (detail 10) from rotating and remove the
spring seat. Remove the remaining flange (detail 13).
Still holding the same diaphragm clamp, remove the newly
exposed clamp and diaphragm. Pull the stem (detail 21)
from the valve housing with the remaining diaphragm and
clamp intact. Proceed with the instructions under "DIRECT
AND REVERSE ACTING."
DIRECT AND REVERSE ACTING
Remove the remaining diaphragm and clamp. Remove the
retaining ring (detail 16) while compressing and holding the
spring (detail 19) on the stem. Remove the spring and sleeve
(detail 23) to expose the O-ring (detail 20) for replacement.
Reassemble* the stem assembly in reverse sequence.
To replace the O-ring (detail 18) in the valve housing,
remove the retaining ring (detail 17) and the O-ring directly
beneath it. Insert the new O-ring and replace the retaining
ring.
To replace the O-ring (detail 22) located in the bellows
head, remove the O-ring with a knife or some other sharp
pointed instrument. Carefully remove any residue where the
O-ring was removed and clean the seating area with a
suitable solvent. Dry thoroughly and place a few drops of
liquid Viton (Pelmar Laboratories PLV-2000 or equivalent)
on the seating area. Clean and place the new O-ring on the
seating area. Allow bond to cure for one or more hours.
With all O-rings, diaphragms, gaskets and defective parts
replaced, reassemble* as follows: (refer to Figure 3).
NOTE: For Direct-Acting models hold valve housing as
in Figure 3; for Reverse-Acting models invert housing.
Be certain that all parts are clean and free of foreign
matter. On automatic reset models, turn the differential
adjustment screw counterclockwise several turns. Replace
the stem, diaphragms and diaphragm clamps.* Hand tighten
the clamps and then while holding each clamp with a
wrench, tighten 1/4 turn more.
Replace both flanges and secure with at least two screws
(placed diagonally from each other). On the flange where the
pressure assembly mounts, replace all four screws* (securing
the flange) and snug all screws down.
Replace the spring seat and its locking screw. DO NOT
TIGHTEN YET. Turn the differential adjustment screw
clockwise until it becomes difficult to turn; DO NOT
TIGHTEN. On manual reset models, depress the reset
plunger. Then apply an approximate one pound force at "P"
(See Fig. 3) and turn the spring seat to obtain dimension "A."
Tighten the locking screw* snug and turn the differential
adjustment screw counterclockwise 3/4 turn.
Remove the two screws securing the flange under the
spring seat and replace the spring and spring tower assembly.
Then replace all four screws* to secure the flange and spring
tower.
Reassemble the remainder in reverse sequence and
recalibrate.
*NOTE - The following should be fitted using Loctite
Sealant "H," or equivalent, applied before reassembly:
Spring Seat Screw (detail 8), Diaphragm Clamps,
Spring Housing Screws (detail 11), Bushing, Flange
Screws (detail 31), Housing Plate Screws (detail 41),
Diaphragm Shoe Screw (detail 39) and Cover Screws
(details 35 and 37).
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