Flowserve Cast Globe Valves - Manual (Page 25)

Globe Valves FCD ADENIM0011-00
25
6.0 DISASSEMBLY
(Continued)
6.3.2 Bonnet: (Figs.18, 19, 20 & 21)
The_ following instructions assume the yoke has been removed as explained in 6.3.
a. Unbolt the gland nuts (234) and remove the gland flange (130) and gland (107). Put them in a safe place
and thread the nuts back on the gland studs to prevent loss. Remove the packing (110).
b. On globe valves 6" and larger the bonnet is-held in the raised position by capscrews (216) that draw it up
against a bonnet retainer (034). To disassemble these bonnets, first remove the capscrews and then lift off
the retainer. On globe valves 4" and smaller, a different arrangement is used. The bonnet retainer is
threaded onto the bonnet neck. It must be unthreaded off the bonnet. (Note: in order to lift the retainer off
the bonnet the gland retaining assembly must first be completely removed.)
c. Tap the bonnet sharply to break the seal between it and the pressure seal gasket (ll3ll). The bonnet will
drop downward against the stop, uncovering the retaining ring (033).
d. The retaining ring (gasket) (033) is comprised of four segments, one of which has a small drilled hole.
Remove this piece first. The groove in the top of the retaining ring gasket permits the use of a pry bar or
screwdriver in removing the segments. In some cases, it may be necessary to loosen the segments by
tapping with a hammer or bar.
e. The bonnet is now ready for removal from the body. The tight clearances between the body bonnet and
gasket, necessary far a reliable seal require that the-bonnet be withdrawn squarely from—the neck bore.
The slightest cocking of the bonnet during withdrawal can cause it bind. Therefore, it is recommended prior
to removal that the squareness of the bonnet and gasket with respect to the body be checked. This is most
easily accomplished by measuring the distance between the top of the gasket and top of the body neck. If
the gasket is not square, it should be tapped with a brass rod until it is. With large bonnets it is a good idea,
as well, to periodically check the squareness of bonnet as it is being withdrawn. Binding any time during
withdrawal, indicates the bonnet has cocked. Further efforts to force the bonnet will generally make the
situation worse. At the first sign of binding, stop and check the squareness of the bonnet.
f. The preferred method of lifting the bonnet (fig. 21) is by using slings attached to the gland retainer (131).
This means of lifting minimizes cocking. In order to attain the best attachment, the gland bolts (209) should
be removed and the retaining rings' halves be reassembled on the bonnet. If desired, the sling can be
looped through the retaining ring ears prior to assembly on the bonnet. Attempting to remove the bonnet by
raising the stem, either with slings or the actuator, is not recommended. The load between the stem and
the bonnet will be imparted to the backseat. Excessive force on the backseat sealing surface will cause it to
deform or crack.
g. Following the above procedure will, in most cases, result in removal of the bonnet with little difficulty.
However, certain circumstances such as installation of the valve with stem in other than a vertical
orientation may cause complications. If greater difficulty is encountered, an Anchor/Darling service
engineer should be consulted. Excessive force which may damage critical surfaces should be avoided.
h. It is not normally recommended that the pressure seal gasket be reused. However, if a spare gasket is
not available, mark the gasket, bonnet and body prior to removal so that the gasket may be reinstalled in its
original orientation.