Advertisement
KEYSTONE KNIFE GATE VALVES
FIGURE 955/956
FLUSHING PORTS
CAUTION
Valves should be isolated prior to flushing, as valve
operation during flushing, or defective seats, may
cause the discharge of pipeline media through the
flushing ports at full pipeline pressure.
Valves are provided with flushing ports
to enable the valve body to be cleared of
sedimentation or debris which could impair
valve operation. The provision of a suitable
flushing system to each valve is imperative to
assure proper valve operation.
The type of flushing system employed will need
to be decided by site/project personnel with
due regard to such factors as, services
available, pipeline media, solids content,
service duty, and individual site considerations.
Please contact our Emerson sales/engineering
centres for recommendations on suitable
systems.
NOTE
It should be noted that the use of 'positive flushing' is
mandatory for valves used for line media's containing
hard gravel like solids.
Manual flushing
With the valve in either the open or closed
position, the flushing port plugs may be
carefully removed (see caution note above).
Apply a strong pressurized stream of fluid to
each port allowing the discharge of debris from
the opposing port. When body is cleared, refit
port plugs.
Waste flushing
Flushing plugs may be removed from the
ports and permanent pipework installed to
each port to direct pipeline media, lost during
valve cycling, to a collection point or to waste.
Additional valving may be installed in this
pipework to limit the velocity and/or duration
of the media discharge.
Positive flushing
Pipework may be attached to the flushing
ports to supply the lower valve body with line
compatible fluid at a pressure significantly
above that of the pipeline.The flushing
supply system must also be capable of a
volumetric delivery suitable for this application.
The flow of flushing media into the main
pipeline during valve actuation both minimizes
the amount of debris and sedimentation in the
lower bucket, and also clears larger pipeline
solids from the seat area for valve re-opening.
Some periodic flushing of the lower bucket will
still be required to clear sedimentary solids.
Automatic flushing
Additional valving and pipework may be
installed to the flushing ports to supply flushing
media to one of the flushing ports and a drain
facility to the other. The flushing system may
then be activated by a control system during
valve cycling.
Gland adjustment
Gate gland adjustment on new or rebuilt valves
should be checked on valve installation to the
pressurized pipeline. If leakage occurs, tighten
each adjustment nut evenly until the leak
subsides. If leakage persists check that the
valve is not being subjected to line pressures
above that of its pressure rating, or that
the packing may be damaged, incorrectly
installed or contaminated with foreign matter
(refer gland packing instruction sheet).
CAUTION
Do NOT over tighten gland packing as this will
impede valve operation and cause premature
gate/packing wear.
3
Advertisement
