Mueller Super Centurion 350, Operating Instructions Manual, Page: 7 / 12

6
MUELLER ® SUPER CENTURION ® 350 FIRE HYDRANT
Removing Main Valve From Bonnet Flange
1. Remove Hold Down Nut, Operating Nut, and
Thrust Bearing from Bonnet. Lubricate Brass
Sleeve and slide over threaded stem to prevent
O-ring damage. Unbolt and remove Bonnet.
Remove Brass Sleeve.
2. Slide slotted end of Wrench over top of Stem
and engage the slot with Pin in Upper Stem.
Thread Operating Nut onto stem and tighten
against wrench to hold it securely. Lower
support arm onto top flange of the Upper Barrel
and tighten Thumb Screw to hold the Main
Valve in the closed position. Shut off water at the
Gate Valve. Remove Main Valve Assembly by
turning Seat Wrench counter-clockwise.
3. Lift out Wrench, Lower Stem, Main Valve Assem -
bly and Seat Ring from Hydrant Barrel as a unit.
4. Straighten stainless steel Lock Washer,
unscrew Cap Nut and remove Washer, Stem
Seal, Lower Valve Plate, Main Valve and Seat
Ring. Clean, inspect and replace any damaged
parts. (Main Valve can be reversed to provide
new seal.) Replace Drain Ring Facings. Inspect
and lubricate Top and Bottom Seat Ring O-rings
(replace if necessary). Lubricate all threaded
surfaces and reassemble.
5. With Cap Nut tightened to 100 ft-lbs on 5
1/4” Hydrant or 75 ft-lbs on 4 1/2” Hydrant,
bend edges of stainless steel Lock Washer over
one flat on the Lower Valve Plate and one flat on
the Cap Nut.
6. Lower Main Valve, turn Seat Wrench
clockwise, and carefully thread Main Valve and
Seat Ring into the base of the Hydrant hand-
tight. Raise the Main Valve leaving about 1/2” of
play between the Main Valve and Seat. Lower
Support Arm and tighten Thumb Screw.
7. Turn Seat Wrench clockwise to tighten Main
Valve to 200 ft-lbs. Turn on water at the Gate
Valve and remove Seat Wrench by removing
operating nut.
8. Check Bonnet O-ring for proper position and
condition. Attach Brass Sleeve to Upper Stem and
lubricate outside to protect O-ring Seals from
thread damage. Place Bonnet onto Upper Barrel
and assemble Bonnet Bolts only hand-tight.
Remove Brass Sleeve. Reassemble Operating Nut,
Thrust Bearing (refer to pg 1 for correct assembly),
and Hold Down Nut*. Be sure O-ring Seals are in
good condition at thread shoulder on outside of
Hold Down Nut and on inside where contact is
made with Operating Nut. Remove Oil Filler Plug
in side of Bonnet. Pour MUELLER Hydrant
Lubricant into Oil Reservoir until it is level with the
Oil Filler Hole. Replace Oil Filler Plug.
9. Tighten Bonnet Bolts. Unscrew one Hose
Nozzle Cap slightly to bleed air. Open hydrant
fully. Tighten the Hose Nozzle Cap when water
starts flowing and check all flange connections
for leaks. Turn Operating Nut to fully closed
position and remove Hose Nozzle Cap to allow
Barrel to drain. Replace Nozzle Cap.
10. Turn Operating Nut in closing direction to
make sure Main Valve is closed tightly, then turn
in opening direction approximately 1/4 turn to
relieve tension on operating mechanism.
Before removing any bolt(s) holding the hydrant together, shut off gate valve to isolate hydrant from main water source.
Loosen (do not remove) one nozzle cap two turns and check for water under pressure inside hydrant – bleed off any pressure,
then remove nozzle cap completely. Open hydrant main valve completely. A continuous flow of water, no matter how slight,
indicates hydrant is not properly isolated from the main water supply, and that problem must be corrected before any
hydrant disassembly can proceed. Disassembly of hydrant with pressurized water acting against the main valve could result
in unexpected ejection of hydrant parts, debris or high-pressure water stream, which could cause serious bodily injury.
! WARNING
CAUTION: Always fill the oil reser -
voir with the bonnet installed, the
hydrant in its normal upright
position, and the main valve fully
closed. If the hydrant is filled with
lubricant under any other circum -
stances, excess lubricant can overfill
the bonnet and create a pressure
lock. This could result in damage to
the seals or bonnet, or prevent
proper hydrant operation.
*TIGHTEN HOLD DOWN NUT TO 200-300 FT-
LBS OF TORQUE. IF TORQUE WRENCH IS
NOT AVAILABLE, USE A 3 LB HAMMER TO
STRIKE THE END OF THE A-311 WRENCH
FIRMLY TWO TIMES TO ASSURE THE NUT IS
PROPERLY TIGHTENED.