Globe Valves - Globe valves are used to throttle the flow of product
inside a pipeline. This is the same type of valve used at home on
kitchen or bathroom sinks.
Packing, disks, and seats will become
worn and will need replacing depending on usage. These valves are
used in areas where the throttling of product flow is desired.
Swing Check Valves - Swing check valves permit fuel to flow one way
only by means of a hinged disk or clapper which is pushed aside by the
fuel when it flows in the desired direction. When flow stops and back
pressure develops, the clapper is pushed against its seat, stopping
back flow. These valves are self-operating and need little
maintenance other than tightening the cover nuts regularly. Typically
they are used on the discharge sides of pumps and at pump stations
between the suction and discharge lines of each pump at the pump
station. They are also used at the foot of upgrade slopes in lieu of
gate valves, but they must be removed if the line is ever pumped in
reverse.
Flow Control Valves (Pressure Reducing Valves) - Flow control valves
are activated by pressure. If pressure in the pilot is great enough
to overcome the force of the spring, the excess pressure activates the
diaphragm to throttle the flow in dynamic situations, and in static
conditions it will decrease the head acting against a particular point
in the pipeline. These valves require little maintenance beyond
checking the pilot strainer at least every 3 months and inspecting the
diaphragm once a year. They are used on downhill slopes.
Pressure Relief Valves - Pressure relief valves are set to open at
certain pressures and are triggered by a spring. The pipeline is
tapped at points which may experience excess pressures under static
conditions. If pressures reach the upper limit set on the valve by
the operators, the valve activates by opening and bleeding fuel off
until safe pressures are again reached and the valve resets itself to
the closed position. Typically these valves are used at locations
where the pipe is going to a storage tank to bleed-off excess
pressures built up in the line because of heating by the sun under
shut down conditions. These valves should be tested once a year using
a reliable pressure gage.
Plug Valves - Plug valves are small, compact valves activated by
turning the head of the valve 1/4-turn. This valve may or may not
open to the full diameter of the pipe depending on the type of plug
valve used. As a result, plug valves which do not open to the full
diameter of the pipe cannot be used in portions of the pipeline
through which a scraper is designed to pass. This valve can be
lubricated in the open or closed position. Lubrication is done
through the lubrication screw at the top by the use of a high pressure
grease gun, or the screw can be screwed down. This valve also has
rope-type packing which must be periodically replaced. Plug valves
are commonly used at tank farm manifolds or in places requiring quick,
positive shut-off such as at a scraper launching station.
Additional pipeline components.
Figure Eight Blinds - Figure eight blinds provide a positive shutoff in
pipelines and manifold areas. A line blind is comprised of a flanged
holder, hand wheel, and figure eight blind. Turning the hand wheel one
way causes the holder to spread open wide enough to insert or remove one
12-90
QM 5099
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