Table of Contents
Advertisement
5.0 CLAPPER REPLACEMENT PROCEDURE:
5.1 Position clapper firmly against
the seat face.
5.2 Pre-load spring and bind using
filament tape (see Fig. 1).
5.3 Take the clapper pin with the
extension screw and insert the
pin into the spring and support
hangers (see Fig. 2).
5.4 When holding the clapper firmly
against the seat, the clapper pin
must move freely into position.
5.5 Remove the extension screw,
replace the clapper pin plug, and
cut the filament tape to free the
spring.
5.6 Check the clapper for free movement by opening and
closing the clapper by hand.
5.7 If movement is free, complete the valve assembly.
6.0 MAINTENANCE:
The 3DV threaded valve requires no day-to-day maintenance
or lubrication. It is suggested that the valve be operated once a
month to ensure it is in operable condition. If at any time it is
suspected that the valve is leaking, either in the plug position
or as a check, it is possible that particulate is trapped between
the mating faces of the seal and seat, and is preventing tight
seal action. Cycling the valve from full open to full close causes
a jetting action that will wash away particulate that may be
trapped.
It is not uncommon to discover that when an 3DV threaded
valve has been reported leaking in the closed position, that
the valve is actually not completely closed. The cam-based
design of the 3DV threaded valve makes it almost impossible to
over-close. The 3DV threaded valve is designed to close at an
approximate ninety degree rotation of the plug stem. To close
the valve, rotate the stem one quarter turn and tighten.
An adjustable wrench may be used with the cam-based design
of the valve to assure a positive closure. The most satisfactory
closure is accomplished by turning the plug to a tight fit and
then 'bumping' the plug lightly using the wrench.
If these procedures have been completed and a tight seal is still
not apparent, the valve should be disassembled and inspected
for damage of the clapper seal and seat face, or for excessive
wear of the clapper pin and pin hanger supports.
Fig. 1
Fig. 2
11
7.0 STANDARD OPERATION:
The principle of operation for the 3DV threaded valve is
simple. When in the open position, the clapper swings out of
the flow. If the flow stops, the spring allows the clapper to
close.
When closing the valve, a final 'bumping' action with a wrench
gives the final positive seal closure.
Open Position
With the plug in the open position, the
clapper operates as an efficient check valve.
The clapper being hinged at an angle
provides 90% less dead weight to minimize
clapper slam and chatter.
Closed Downstream
As the plug is rotated toward the closed
position, the downstream part closes first.
This equalizes the pressure so the clapper
closes with little resistance.
SECTION 2 ITEM 1040
DATED NOVEMBER 2012
SUPERCEDES MAY 2010
Balancing
The plug holds the clapper at the selected
flow requirement for balancing.
Positive Seal Closure
Final closing is accomplished by the plug
camming against the back of the clapper.
Advertisement
Table of Contents
