CALEFFI 578 Serie Documentation Technique page 38

On 6" and smaller valves block and tackle or a power hoist can be used to lift valve cover by inserting proper size eye bolt
in place of the center cover plug. On 8" and larger valves there are 4 holes (5/8" - 11 size) where jacking screws and/or eye
bolts may be inserted for lifting purposes. Pull cover straight up to keep from damaging the integral seat bearing and stem.
4. Remove the diaphragm and disc assembly from the valve body. With smaller valves this can be accomplished by hand
by pulling straight up on the stem so as not to damage the seat bearing. On large valves, an eye bolt of proper size
can be installed in the stem and the diaphragm assembly can be then lifted with a block and tackle or power hoist. Take
care not to damage the stem or bearings. The valve won't work if these are damaged.
5. The next item to remove is the stem nut. Examine the stem threads above the nut for signs of mineral deposits or cor-
rosion. If the threads are not clean, use a wire brush to remove as much of the residue as possible. Attach a good fitting
wrench to the nut and give it a sharp "rap" rather than a steady pull. Usually several blows are sufficient to loosen the nut
for further removal. On the smaller valves, the entire diaphragm assembly can be held by the stem in a vise equipped
with soft brass jaws before removing the stem nut.
The use of a pipe wrench or a vise without soft brass jaws scars the fine finish on the stem. No amount of careful dressing
can restore the stem to its original condition. Damage to the finish of the stem can cause the stem to bind in the bearings
and the valve will not open or close.
6. After the stem nut has been removed, the diaphragm assembly breaks down into its component parts. Removal of the
disc from the disc retainer can be a problem if the valve has been in service for a long time. Using two screwdrivers inser-
ted along the outside edge of the disc usually will accomplish its removal. Care should be taken to preserve the spacer
washers in water, particularly if no new ones are available for re-assembly.
7. The only part left in the valve body is the seat which ordinarily does not require removal. Careful cleaning and polishing of
inside and outside surfaces with 400 wet/dry sandpaper will usually restore the seat's sharp edge. If, however, it is badly
worn and replacement is necessary, it can be easily removed.
Seats in valve sizes 1 1/4" through 6" are threaded into the valve body.
They can be removed with accessory X109 Seat Removing Tool availa-
ble from the factory. On 8" and larger valves, the seat is held in place by
flat head machine screws. Use a tight-fitting, long shank screwdriver to
prevent damage to seat screws. If upon removal of the screws the seat
cannot be lifted out, it will be necessary to use a piece of angle or channel
iron with a hole drilled in the center. Place it across the body so a long
stud can be inserted through the center hole in the seat and the hole in the
angle iron. By tightening the nut a uniform upward force is exerted on the
seat for removal.
Note: Do not lift up on the end of the angle iron as this may force the
integral bearing out of alignment, causing the stem to bind.
Installation - Operation - Maintenance
COVER CENTER PLUG SIZE
Valve size
NGE GE / AE
DN 50 DN 32 - 40
DN 65 - 100 DN 50 - 80
DN 125 - 200 DN 100 - 150
DN 250 - 300 DN 200 - 250
DN 650 - 400 DN 300
- DN 350
DN 500 - 600 DN 400
VALVE STEM THREAD SIZE
Valve size
NGE GE / AE
DN 50 - 80 DN 32 - 65
DN 100 - 150 DN 80 - 100
DN 200 - 400 DN 150 - 350
DN 500 - 600 DN 400
Thread Size (NPT)
1/4"
1/2"
3/4"
1"
1 1/4"
1 1/2"
2"
Thread Size (Internal)
10 - 32 UNF
1/4 - 28 UNF
3/8 - 24 UNF
1/2 - 20 UNF
VALVE SEAT
VALVE BODY
38
Serie 578
NGE - GE - AE
ANGLE OR CHANNEL IRON
NUT
LONG STUD
OR BOLT
NUT OR
BOLT HEAD