Operating & Service Manual 11 OPS-801 Rev.06
e)
Install new stem packing careful to install them with the expander spring side facing down into the
bonnet box. A little oil would help to squeeze the packing down. Replace packing gland. (See
Assembly Procedure for more information on assembly)
CAUTION:
If the replacement of stem packing is perform under line pressure and stem back seat, the task
should be carried out in the most efficient and swift manner to minimize exposure time.
f)
Remove stinger cap and reinstall protective cap to bonnet injection fitting. Install bearing assembly and
bonnet cap and set screw. (See Assembly Procedure for more information on assembly detail)
CAUTION:
Making up of bonnet cap will result in unseating the stem back seat and may subject stem packing to
line pressure in the valve.
g)
Lubricate stem bearing and valve cavity if necessary according to aforementioned recommended
procedures.
3)
Stem Back Seat
– Valve in Closed Position
a)
Close valve fully and back off ¼ turn.
b)
Remove set screw on the bonnet cap. Mark location and back off bonnet cap 3 full turns. If there is
sufficient line pressure in the valve the stem could be seen rising as the bonnet cap is back off. The
stem would stop the upward movement once the back seat taper on the stem comes into contact with
the matching profile in the bonnet. In case there is no line pressure, an upward heave on the hand-
wheel would similarly raise the stem.
The rest of the procedure steps c)-g) is similar to the procedure as in Stem Back Seating in Valve
Open Position.