Leslie Controls Pilot Controller - Manual (Page 11)

Page 11
Replacing Upper Diaphragms
Constant Pressure Pilot Controllers
(PDA-1, PRA-1, etc.)
For Type UDDV, UDRV Consult Instruction 20/2.5.3
For Type UDDD Consult Instruction 20/3.5.1
1. In all pilot controllers remove all adjusting spring com-
pression by screwing locknut (23) downward as far as it
will go, then following with adjusting nut (22) until all
compression is removed from adjusting spring (12). In
the case of lever action types (PRA-1, etc.) relieve lever
spring compression also by removing spring cap (49).
2. Disassemble bolts and nuts (2/8), diaphragm cover (3)
from diaphragm base (9). Remove spring (87) (13 psia -
20 psig range only). Clean cover. In direct acting types
(PDA-1, etc.) take screw (27) out of stem (13).
3. For all ranges from 13 psia - 20 psig to 50-125 psig Lift
diaphragm assembly out of diaphragm base (9). Hold
diaphragm disc screw (1) rigidly on hex and loosen
diaphragm disc nut (4). Disassemble parts. Clean parts,
replace diaphragm. Place diaphragm disc (7),
diaphragm (6), and diaphragm disc washer (5) on
diaphragm disc screw (1). Assemble diaphragm disc
nut (4) to diaphragm disc screw (1). Tighten snugly to
make a good pressure seal. Do not distort diaphragm.
For ranges 100-200 psig and over Diaphragm may be
changed by simply removing spring compression, dis-
assembling bolts/nuts and cover, replacing diaphragm
and closing unit up again.
NOTE: Balance of superstructure parts may be cleaned,
examined, and replaced if necessary at this point. To examine
yielding spring (18)(PDA-1, etc.) hold disc screw (1), rigidly on
hex. Press down on stem (13). Remove stem nut (19).
Disassemble parts. Reassemble. Tighten stem nut.
4. Replace diaphragm assembly in diaphragm base (9).
Reassemble diaphragm cover (3), and bolts and nuts
(2/8) to diaphragm base. Tighten bolts to make good
pressure seal.
Proceed with Step 5, “REASSEMBLY” insofar as it
applies to parts removed to permit rework of super-
structure and stem length readjustment (if the latter is
necessary). Reassemble pilot cover and screw to base
(25). Do not overtighten screw.
5. Reconnect control pipe to diaphragm cover and operat-
ing medium lines to pilot controller and valve. Turn on
operating medium supply and adjust pilot controller for
desired controlled pressure as described under “OPER-
ATION.”
Stem Length Adjustment (Pin/Lever)
Desired pilot controller performance will be obtained only if
the upper (sensing) diaphragm is operating at or near its mean
position, i.e. half way between its top and bottom limit stops
in base and cover. Its position is determined by adjusting
length of adjusting pin (53) in PDA-1, etc. types and lever
screw (26) in PRA-1, etc. types.
NOTE: THIS ADJUSTMENT IS FACTORY SET and should
not be disturbed unless it is obvious that the original setting
has been changed or major parts replacements were made
which may cause need for readjustment.
These adjustments can be made when the pilot controller is
set for either continuous or non-continuous leak off.
Adjustment Procedure
In all cases: Supply 20-22 psig operating pressure to the pilot
controller. Turn adjusting nut (22) to compress adjusting
spring to set upper diaphragm against its top limit stop. If
possible, remove fluid pressure from top of diaphragm, if not,
compress spring sufficiently to overcome fluid pressure and
move diaphragm to stop. Blank off output connection to
D.C.V.
PDA-1, PDW-1, PDQ, UDDV, etc. Pilot Controllers
1. Loosen locknut (74) on adjusting pin (53). Turn adjusting
pin (53) downward toward pilot until 0-3 psig air pres-
sure shows on output gauge.
2. Then turn adjusting pin (53) back upward into extension
pin (86) (away from pilot body) 1 turn for all low pres-
sure pilots (up to and including the 50-125 psig range);
1-3/4 turns for high pressure pilots (ranges 100-200
psig and over). Tighten locknut (74).
3. Reconnect output to D.C.V.
PRA-1, PRW-1, PRQ, UDRV, Etc. Pilot Controllers
1. Loosen locknut (27) on lever setscrew (87). With 20 psig
air pressure on output gauge turn setscrew (87) upward
into lever until output air pressure just begins to fall
away from 20 psig.
Figure 15. — FOR PRESSURE RANGES 13 PSIA - 20 PSIG TO
50-125 THIS TYPE OF DIAPHRAGM ASSEMBLY IS USED