Jordan Valve Mark 78 Series – Globe Style Control Valve - Manual (Page 4)

-4-
Note B: air pressures quoted are relative. Actual pres-
sures required in operation may vary with pressure
drop conditions existing and/or actuator springs used.
Actuator Maintenance
Disassembly and Inspection of Actuator
1. Close inlet and outlet stop valves. Operate system by-
pass, if necessary. Remove the actuator as described
in “Valve Disassembly”, Step 3.
2. Remove the nuts (27) and bolts (7) which hold the up-
per actuator case (26) to the lower actuator case (16)
and remove the upper actuator case.
3a. Direct Acting Actuator (ATC): remove the actua-
tor stem bolt (45) and lift the fastener seal (21), seal
washer (22), diaphragm (23), diaphragm plate (24),
and spacer (38) from the actuator stem. Remove the
actuator stem (17). To check the stem o-ring (31), un-
screw the gland nut (20) from the gland (19) and re-
move the bushing (36) and stem o-ring from the end
of the actuator (16).
3b. Reverse Acting Actuator (ATO): remove springs (25)
from diaphragm plate (24). Remove the actuator stem
bolt (45) and lift spacer (38), diaphragm plate (24),
diaphragm (23), seal washer 22) and fastener seal
(21) from the actuator stem (17). Remove the actua-
tor stem (17). To check the stem o-ring (31), unscrew
the gland nut (20) from the gland (19) and remove
the bushing (36), and stem o-ring from the end of the
gland.
4. Clean all parts with an approved, non-residue-forming
solvent. Remove encrusted material with crocus or
very mild aluminum oxide cloth. Inspect all parts for
excessive wear and/or damage. Replace any worn or
damaged parts.
Reassembly of Actuator
After all parts have been thoroughly cleaned and inspect-
ed, reassemble the actuator.
1. Direct Acting Actuator (ATC): insert the actuator stem
(17) through the gland (19), greasing stem o-ring (31),
if available, before inserting the actuator stem and
bushing (36) and gland nut (20). Place the springs
(25) in the lower actuator case (16). Place the spacer
(38), diaphragm plate (24) on the springs so that the
stamped bosses are nested in the springs. Install the
diaphragm (23) so the bolt holes line up with the bolt
holes in the lower actuator case. Place the seal wash-
er (22) on the diaphragm and bolt together with the
seal ring (21) and actuator stem bolt (45) and tighten.
2. Reverse Acting Actuator (ATO): lightly grease the
stem o-ring (31) and install in the c’bore in the gland
(18), bushing (36), gasket (18) and gland nut (20).
Thread actuator stem (17) through the gland. Assem-
ble the spacer (38) [55M actuators only], diaphragm
plate (24), diaphragm (23), seal washer (22) and fas-
tener seal (21) to stem actuator bolt (45) and thread
into the actuator stem (17). Line up the bolt holes in
the diaphragm with the holes in the lower diaphragm
case. Place the springs (25) on the diaphragm plate
nested over the punched bosses.
3. Place the upper actuator case (26) on the diaphragm,
lining up the bolt holes.
4. Replace four bolts (7) and nuts (27) 90° apart and
tighten finger-tight. Replace the remainder of the bolts
and nuts and tighten evenly and alternate across the
actuator case.
5. Thread the valve stem (9) into the stem connector
(34) and adjust the spring preload as described previ-
ously (“Actuator Spring Preload Adjustment”).
Reversing Action
Changing the valve action from direct to reverse acting or
from reverse to direct acting.
Different actuator springs are required to meet the pub-
lished pressure drop ratings when changing action. Fail-
ure to do so will change the allowable pressure drop ca-
pability of the valve. Consult factory for details.
The action of the Mark 78 control valve is reversed by
reversing the action of the actuator.
1. Disassemble the actuator as described in “Actuator
Maintenance”.
2. Reassemble the actuator with the desired action. Re-
fer to “Actuator Maintenance”.
Troubleshooting
If you Experience Erratic Control:
 Oversizing causes cycling or hunting – recalculate
size required.
 Undersizing causes control setting to drop under
peak loads.
 Steam traps downstream may need reconditioning.
 Safety relief valve may be jammed open.
 Excessive foreign matter may be lodged in seats.
 Valve stroke may be out of adjustment.
 Valve plug may not be moving freely.
 Inlet pressure may be too low.
If You Experience Insufficient Flow:
 Check shutoff valves to be sure they are fully open.
 Check pressure on upstream side (install a pressure
gauge on the upstream side).
 Blow down strainers.
 Clean all traps and be sure they are in good working
order. If the return line from the trap is cool, the steam
coil may be clogged.