wT 1255/12
Page 15
11.1
Disassembly for Valve Ring Replacement
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Depressurize and purge pipe
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Fully open piston valve
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Unscrew and remove bonnet securing nuts (Pos. 27) and belleville washers (Pos.33)
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Rotate the handwheel (Pos. 3) clockwise (closing direction) until the bonnet is
moved out of the body and the bonnet flange is situated above the stud bolts
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Now slightly twist the bonnet (Pos. 2) so that the bonnet flange is braced on the
stud bolt faces (Pos. 25). Rotate the handwheel counterclockwise (opening
direction), until the piston (Pos. 4) is fully pulled out of the upper valve ring (Pos. 14)
(see Figure 1)
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Remove the bonnet with the handwheel, spindle and piston
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Pull out the thrust piece (Pos. 19) and the bonnet valve ring (Pos. 14) by means of
a ring extractor hook (see Fig. 2)
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Pull out the lantern bush (Pos. 5) by means of a lantern bush drawer without
damaging the surface of the body’s bore (see Fig. 3)
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Pull out the lower valve ring (Pos. 9) by means of a ring extractor hook without
damaging the surface of the body’s bore
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Clean the bore of the body and the valve ring seat
11.2
Checks during Valve Ring Replacement
!
CAUTION
The elements of the bonnet (piston, spindle, thread and bonnet) must
always be examined with regard to their correct function during the course
of valve ring replacement.
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The surface of the piston must be smooth and not display any score marks.
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The spindle head must be easy to turn in the split nut.
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The trapezoid thread of the spindle may not display too much wear.
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The clearance between the spindle thread and the thread of the bonnet and/or the
threaded bush may not be unnaturally large.
Should no components require replacement, the trapezoid thread and the bonnet throat
must be lubricated prior to assembly of the valve.
Figure 1
Figure 2
Figure 3